Journal articles on the topic 'Receptor depletion'
To see the other types of publications on this topic, follow the link: Receptor depletion.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Receptor depletion.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Frey, A. B. "Role of host antigen receptor-bearing and antigen receptor-negative cells in immune response to rat adenocarcinoma 13762." Journal of Immunology 156, no. 10 (May 15, 1996): 3841–49. http://dx.doi.org/10.4049/jimmunol.156.10.3841.
Full textAbstract:
Abstract Involvement of individual immune cell populations in the immune response to rat breast adenocarcinoma 13762 was studied by selective depletion treatments in vivo. Depletion of Ag nonspecific host defense cells from naive animals before tumor challenge resulted in statistically significant acceleration of tumor growth (p less than 0.01 or less), whereas depletion of either CD4+ T cells or CD8+ T cells had no effect on the incidence or kinetics of tumor development. In contrast to naive animals treated before tumor challenge, animals actively immunized by injection of irradiated tumor before depleting treatments were shown to require CD4+ T cells to reject tumorigenic challenge. Depletion of either macrophages or neutrophils from immune animals also increased tumor development, whereas NK cells were not involved. Depletion of CD8+ T cells from immune animals permitted transient growth of tumors that were subsequently rejected, implying a role in tumor rejection. Transfer of immune antiserum to naive animals at the time of tumor challenge was without effect on tumor development. Depletion of CD4+ T cells, neutrophils, or macrophages in the priming phase of antitumor immune response abrogated tumor immunity, but depletion of CD8+ T cells or NK cells was without effect on the ability to prime animals by immunization with irradiated cells. Collectively, these data suggest that host natural defense cells that do not express Ag receptor are primarily responsible for resistance of adenocarcinoma 13762 growth in naive animals. In contrast, tumor immunity induced by active immunization requires Ag receptor-bearing CD4+ T cells and involves participation of CD8+ T cells, neutrophils, or macrophages in elimination of tumor.
2
Ray, P. E., E. Castren, E. J. Ruley, and J. M. Saavedra. "Different effects of sodium or chloride depletion on angiotensin II receptors in rats." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 258, no. 4 (April 1, 1990): R1008—R1015. http://dx.doi.org/10.1152/ajpregu.1990.258.4.r1008.
Full textAbstract:
We studied the effects of selective chronic sodium or chloride depletion (0.005% in diet) on central and peripheral angiotensin II receptors in young rats. Chloride depletion produced the most significant increase in plasma renin activity and extracellular fluid volume contraction. In the brain, subfornical organ angiotensin II receptor concentration was decreased by sodium depletion and increased by chloride depletion. There were no significant changes in angiotensin II binding in the paraventricular nucleus. When sodium-depleted rats were water deprived for 3 days, subfornical organ angiotensin II receptor concentration increased, showing that normal sodium intake was not essential for increased numbers of angiotensin II receptors during dehydration. In the adrenal gland, chloride depletion decreased angiotensin II receptors in the medulla and zona glomerulosa. Conversely, sodium depletion increased angiotensin II receptors in the zona glomerulosa. In the kidney glomeruli and medulla, angiotensin II receptors were decreased by either sodium or chloride depletion. These results suggest different roles for sodium and chloride in the regulation of the peripheral and central renin-angiotensin system in young rats.
3
Aoh, Quyen L., Anna M. Castle, Charles H. Hubbard, Osamu Katsumata, and J. David Castle. "SCAMP3 Negatively Regulates Epidermal Growth Factor Receptor Degradation and Promotes Receptor Recycling." Molecular Biology of the Cell 20, no. 6 (March 15, 2009): 1816–32. http://dx.doi.org/10.1091/mbc.e08-09-0894.
Full textAbstract:
The epidermal growth factor receptor (EGFR) is targeted for lysosomal degradation by ubiquitin-mediated interactions with the ESCRTs (endosomal-sorting complexes required for transport) in multivesicular bodies (MVBs). We show that secretory carrier membrane protein, SCAMP3, localizes in part to early endosomes and negatively regulates EGFR degradation through processes that involve its ubiquitylation and interactions with ESCRTs. SCAMP3 is multimonoubiquitylated and is able to associate with Nedd4 HECT ubiquitin ligases and the ESCRT-I subunit Tsg101 via its PY and PSAP motifs, respectively. SCAMP3 also associates with the ESCRT-0 subunit Hrs. Depletion of SCAMP3 in HeLa cells by inhibitory RNA accelerated degradation of EGFR and EGF while inhibiting recycling. Conversely, overexpression enhanced EGFR recycling unless ubiquitylatable lysines, PY or PSAP motifs in SCAMP3 were mutated. Notably, dual depletions of SCAMP3 and ESCRT subunits suggest that SCAMP3 has a distinct function in parallel with the ESCRTs that regulates receptor degradation. This function may affect trafficking of receptors from prelysosomal compartments as SCAMP3 depletion appeared to sustain the incidence of EGFR-containing MVBs detected by immunoelectron microscopy. Together, our results suggest that SCAMP3, its modification with ubiquitin, and its interactions with ESCRTs coordinately regulate endosomal pathways and affect the efficiency of receptor down-regulation.
4
Lu, Justine P., Yuan Wang, Danielle A. Sliter, Margaret M. P. Pearce, and Richard J. H. Wojcikiewicz. "RNF170 Protein, an Endoplasmic Reticulum Membrane Ubiquitin Ligase, Mediates Inositol 1,4,5-Trisphosphate Receptor Ubiquitination and Degradation." Journal of Biological Chemistry 286, no. 27 (May 24, 2011): 24426–33. http://dx.doi.org/10.1074/jbc.m111.251983.
Full textAbstract:
Inositol 1,4,5-trisphosphate (IP3) receptors are endoplasmic reticulum membrane calcium channels that, upon activation, are degraded via the ubiquitin-proteasome pathway. While searching for novel mediators of IP3 receptor processing, we discovered that RNF170, an uncharacterized RING domain-containing protein, associates rapidly with activated IP3 receptors. RNF170 is predicted to have three membrane-spanning helices, is localized to the ER membrane, and possesses ubiquitin ligase activity. Depletion of endogenous RNF170 by RNA interference inhibited stimulus-induced IP3 receptor ubiquitination, and degradation and overexpression of a catalytically inactive RNF170 mutant suppressed stimulus-induced IP3 receptor processing. A substantial proportion of RNF170 is constitutively associated with the erlin1/2 (SPFH1/2) complex, which has been shown previously to bind to IP3 receptors immediately after their activation. Depletion of RNF170 did not affect the binding of the erlin1/2 complex to stimulated IP3 receptors, whereas erlin1/2 complex depletion inhibited RNF170 binding. These results suggest a model in which the erlin1/2 complex recruits RNF170 to activated IP3 receptors where it mediates IP3 receptor ubiquitination. Thus, RNF170 plays an essential role in IP3 receptor processing via the ubiquitin-proteasome pathway.
5
Lièvremont, Jean-Philippe, Gary St J. Bird, and James W. Putney. "Canonical transient receptor potential TRPC7 can function as both a receptor- and store-operated channel in HEK-293 cells." American Journal of Physiology-Cell Physiology 287, no. 6 (December 2004): C1709—C1716. http://dx.doi.org/10.1152/ajpcell.00350.2004.
Full textAbstract:
Previous studies on the activation mechanism of canonical transient receptor potential (TRPC) channels have often produced conflicting conclusions. All seven have been shown to be activated by phospholipase C (PLC)-coupled receptors, but TRPC1, TRPC2, TRPC3, TRPC4, TRPC5, and TRPC7 have also been proposed to function as store-operated channels. 1 1 Although PLC activation inevitably leads to activation of store-operated channels, in this report when we refer to PLC-activated channels, we mean those channels that are specifically activated by PLC independently of store depletion. In the case of TRPC3, the expression environment and the expression level appear to determine the mode of regulation. Evidence of a close structural relative of TRPC3, TRPC7, has been presented that this channel is activated by receptor activation or by store depletion. On the basis of previous findings for TRPC3, we reasoned that subtle differences in structure or expression conditions might account for the apparent distinct gating mechanisms of TRPC7. To reexamine the mode of activation of TRPC7, we stably and transiently transfected human embryonic kidney (HEK)-293 cells with cDNA encoding for human TRPC7. We examined the ability of a PLC-activating agonist and an intracellular Ca2+ store-depleting agent to activate these channels. Our findings demonstrate that when transiently expressed in HEK-293 cells, TRPC7 forms channels that are activated by PLC-stimulating agonists, but not by Ca2+ store depletion. However, when stably expressed in HEK-293 cells, TRPC7 can be activated by either Ca2+ store depletion or PLC activation. To our knowledge, this is the first demonstration of a channel protein that can be activated by both receptor- and store-operated modes in the same cell. In addition, the results reconcile the apparently conflicting findings of other laboratories regarding TRPC7 regulation.
6
Kyakumoto, S., R. Kurokawa, and M. Ota. "Mechanism of replenishment of androgen receptors in cytosol of mouse submandibular gland." Journal of Endocrinology 115, no. 3 (December 1987): 411–18. http://dx.doi.org/10.1677/joe.0.1150411.
Full textAbstract:
ABSTRACT Female mice were used to examine the process of depletion and replenishment of cytosolic androgen receptors in submandibular glands, and to investigate the effects of cycloheximide and actinomycin D on these processes. The dose-dependence of receptor depletion and replenishment in the cytosolic fraction, and that of receptor accumulation in the nuclear fraction were investigated. Almost 100% depletion was revealed 1 h after the injection of testosterone propionate at a dose of 500 or 50 μg testosterone/100 g body weight. With a 5 μg dose, depletion of cytosolic receptors was not complete and replenishment proceeded rapidly compared with that which occurred with the 50 or 500 μg dose. The nuclear receptor level increased 1 h after injection of testosterone, and the raised level was gradually reduced to the pretreatment level with all doses. However, the time required for this return to pretreatment level was dependent on the dose of testosterone. The change in the levels of cytosolic and nuclear androgen receptors following injection of testosterone was parallel to the level of circulating androgen. To determine the requirements for transcriptional and translational events in the replenishment process, cycloheximide and actinomycin D were given in vivo. The process of replenishment of cytosolic receptors was inhibited by the injection of cycloheximide. However, actinomycin D exerted no inhibitory effect on receptor replenishment. Neither cycloheximide nor actinomycin D had any effect on the nuclear receptor level until 6 h after the injection of testosterone. Cycloheximide or actinomycin D alone had no effect on the cytosolic or nuclear receptor level. These results suggest that receptor replenishment involves protein synthesis. J. Endocr. (1987) 115, 411–418
7
Peterson, Theresa J., Sudipan Karmakar, Margaret C. Pace, Tong Gao, and Carolyn L. Smith. "The Silencing Mediator of Retinoic Acid and Thyroid Hormone Receptor (SMRT) Corepressor Is Required for Full Estrogen Receptor α Transcriptional Activity." Molecular and Cellular Biology 27, no. 17 (June 25, 2007): 5933–48. http://dx.doi.org/10.1128/mcb.00237-07.
Full textAbstract:
ABSTRACT Multiple factors influence estrogen receptor α (ERα) transcriptional activity. Current models suggest that the silencing mediator of retinoic acid and thyroid hormone receptor (SMRT) corepressor functions within a histone deactylase-containing protein complex that binds to antiestrogen-bound ERα and contributes to negative regulation of gene expression. In this report, we demonstrate that SMRT is required for full agonist-dependent ERα activation. Chromatin immunoprecipitation assays demonstrate that SMRT, like ERα and the SRC-3 coactivator, is recruited to an estrogen-responsive promoter in estrogen-treated MCF-7 cells. Depletion of SMRT, but not histone deacetylases 1 or 3, negatively impacts estradiol-stimulated ERα transcriptional activity, while exogenous expression of SMRT's receptor interaction domains blocks ERα activity, indicating a functional interaction between this corepressor and agonist-bound ERα. Stimulation of estradiol-induced ERα activity by SMRT overexpression occurred in HeLa and MCF-7 cells, but not HepG2 cells, indicating that these positive effects are cell type specific. Similarly, the ability of SMRT depletion to promote the agonist activity of tamoxifen was observed for HeLa but not MCF-7 cells. Furthermore, impairment of agonist-stimulated activity by SMRT depletion is specific to ERα and not observed for receptors for vitamin D, androgen, or thyroid hormone. Nuclear receptor corepressor (N-CoR) depletion increased the transcriptional activity of all four tested receptors. SMRT is required for full expression of the ERα target genes cyclin D1, BCL-2, and progesterone receptor but not pS2, and its depletion significantly attenuated estrogen-dependent proliferation of MCF-7 cells. Taken together, these data indicate that SMRT, in conjunction with gene-specific and cell-dependent factors, is required for positively regulating agonist-dependent ERα transcriptional activity.
8
Linas, S. L., R. Marzec-Calvert, and M. E. Ullian. "K depletion alters angiotensin II receptor expression in vascular smooth muscle cells." American Journal of Physiology-Cell Physiology 258, no. 5 (May 1, 1990): C849—C854. http://dx.doi.org/10.1152/ajpcell.1990.258.5.c849.
Full textAbstract:
Dietary K depletion (KD) results in increases in the number of angiotensin II (ANG II) receptors and prevents ANG II-induced downregulation of ANG II receptors in membrane preparations of vessels from KD animals. Because dietary KD results in changes in factors other than K, we K depleted vascular smooth muscle cells (VSMC) in culture to determine the specific effects of KD on ANG II receptor expression and processing. Scatchard analysis of ANG II uptake at 4 degrees C revealed that the number of surface receptors was increased by 37% in cells in which K had been reduced by 45%. This increase also occurred in the presence of cycloheximide. To determine the effect of KD on receptor processing, we measured the number of surface receptors after exposure to ANG II in concentrations sufficient to cause down-regulation. After 30-min exposure to ANG II, the number of surface receptors was reduced by 63% in control cells but only 33% in KD cells. Thirty minutes after withdrawing ANG II, surface binding returned to basal levels in control cells but was still reduced by 20% in KD cells. To determine the functional significance of impaired receptor processing, we measured ANG II uptake at 21 degrees C. Uptake at 21 degrees C depends on the functional number of receptors, i.e., the absolute number of surface receptors and the rate at which receptors are recycled to the surface after ANG II binding. ANG II uptake at 21 degrees C was reduced by 50% in KD cells.(ABSTRACT TRUNCATED AT 250 WORDS)
9
Morris, Gavin E., Carl P. Nelson, Paul J. Brighton, Nicholas B. Standen, R. A. John Challiss, and Jonathon M. Willets. "Arrestins 2 and 3 differentially regulate ETA and P2Y2 receptor-mediated cell signaling and migration in arterial smooth muscle." American Journal of Physiology-Cell Physiology 302, no. 5 (March 1, 2012): C723—C734. http://dx.doi.org/10.1152/ajpcell.00202.2011.
Full textAbstract:
Overstimulation of endothelin type A (ETA) and nucleotide (P2Y) Gαq-coupled receptors in vascular smooth muscle causes vasoconstriction, hypertension, and, eventually, hypertrophy and vascular occlusion. G protein-coupled receptor kinases (GRKs) and arrestin proteins are sequentially recruited by agonist-occupied Gαq-coupled receptors to terminate phospholipase C signaling, preventing prolonged/inappropriate contractile signaling. However, these proteins also play roles in the regulation of several mitogen-activated protein kinase (MAPK) signaling cascades known to be essential for vascular remodeling. Here we investigated whether different arrestin isoforms regulate endothelin and nucleotide receptor MAPK signaling in rat aortic smooth muscle cells (ASMCs). When intracellular Ca2+ levels were assessed in isolated ASMCs loaded with Ca2+-sensitive dyes, P2Y2 and ETA receptor desensitization was attenuated by selective small-interfering (si)RNA-mediated depletion of G protein-coupled receptor kinase 2 (GRK2). Using similar siRNA techniques, knockdown of arrestin2 prevented P2Y2 receptor desensitization and enhanced and prolonged p38 and ERK MAPK signals, while arrestin3 depletion was ineffective. Conversely, arrestin3 knockdown prevented ETA receptor desensitization and attenuated ET1-stimulated p38 and ERK signals, while arrestin2 depletion had no effect. Using Transwell assays to assess agonist-stimulated ASMC migration, we found that UTP-stimulated migration was markedly attenuated following arrestin2 depletion, while ET1-stimulated migration was attenuated following knockdown of either arrestin. These data highlight a differential arrestin-dependent regulation of ETA and P2Y2 receptor-stimulated MAPK signaling. GRK2 and arrestin expression are essential for agonist-stimulated ASMC migration, which, as a key process in vascular remodeling, highlights the potential roles of GRK2 and arrestin proteins in the progression of vascular disease.
10
Clarke, David C., Meredith L. Brown, Richard A. Erickson, Yigong Shi, and Xuedong Liu. "Transforming Growth Factor β Depletion Is the Primary Determinant of Smad Signaling Kinetics." Molecular and Cellular Biology 29, no. 9 (February 17, 2009): 2443–55. http://dx.doi.org/10.1128/mcb.01443-08.
Full textAbstract:
ABSTRACT A cell's decision to growth arrest, apoptose, or differentiate in response to transforming growth factor β (TGF-β) superfamily ligands depends on the ligand concentration. How cells sense the concentration of extracellular bioavailable TGF-β remains poorly understood. We therefore undertook a systematic quantitative analysis of how TGF-β ligand concentration is transduced into downstream phospho-Smad2 kinetics, and we found that the rate of TGF-β ligand depletion is the principal determinant of Smad signal duration. TGF-β depletion is caused by two mechanisms: (i) cellular uptake of TGF-β by a TGF-β type II receptor-dependent mechanism and (ii) reversible binding of TGF-β to the cell surface. Our results indicate that cells sense TGF-β dose by depleting TGF-β via constitutive TGF-β type II receptor trafficking processes. Our results also have implications for the role of the TGF-β type II receptor in disease, as tumor cells harboring TGF-β type II receptor mutations exhibit impaired TGF-β depletion, which may contribute to the overproduction of TGF-β and a consequently poor prognosis in cancer.
11
Jung, Seung-Ryoung, Jong Bae Seo, Yi Deng, Charles L. Asbury, Bertil Hille, and Duk-Su Koh. "Contributions of protein kinases and β-arrestin to termination of protease-activated receptor 2 signaling." Journal of General Physiology 147, no. 3 (February 29, 2016): 255–71. http://dx.doi.org/10.1085/jgp.201511477.
Full textAbstract:
Activated Gq protein–coupled receptors (GqPCRs) can be desensitized by phosphorylation and β-arrestin binding. The kinetics and individual contributions of these two mechanisms to receptor desensitization have not been fully distinguished. Here, we describe the shut off of protease-activated receptor 2 (PAR2). PAR2 activates Gq and phospholipase C (PLC) to hydrolyze phosphatidylinositol 4,5-bisphosphate (PIP2) into diacylglycerol and inositol trisphosphate (IP3). We used fluorescent protein–tagged optical probes to monitor several consequences of PAR2 signaling, including PIP2 depletion and β-arrestin translocation in real time. During continuous activation of PAR2, PIP2 was depleted transiently and then restored within a few minutes, indicating fast receptor activation followed by desensitization. Knockdown of β-arrestin 1 and 2 using siRNA diminished the desensitization, slowing PIP2 restoration significantly and even adding a delayed secondary phase of further PIP2 depletion. These effects of β-arrestin knockdown on PIP2 recovery were prevented when serine/threonine phosphatases that dephosphorylate GPCRs were inhibited. Thus, PAR2 may continuously regain its activity via dephosphorylation when there is insufficient β-arrestin to trap phosphorylated receptors. Similarly, blockers of protein kinase C (PKC) and G protein–coupled receptor kinase potentiated the PIP2 depletion. In contrast, an activator of PKC inhibited receptor activation, presumably by augmenting phosphorylation of PAR2. Our interpretations were strengthened by modeling. Simulations supported the conclusions that phosphorylation of PAR2 by protein kinases initiates receptor desensitization and that recruited β-arrestin traps the phosphorylated state of the receptor, protecting it from phosphatases. Speculative thinking suggested a sequestration of phosphatidylinositol 4-phosphate 5 kinase (PIP5K) to the plasma membrane by β-arrestin to explain why knockdown of β-arrestin led to secondary depletion of PIP2. Indeed, artificial recruitment of PIP5K removed the secondary loss of PIP2 completely. Altogether, our experimental and theoretical approaches demonstrate roles and dynamics of the protein kinases, β-arrestin, and PIP5K in the desensitization of PAR2.
12
Brierley, G. V., S. L. Macaulay, B. E. Forbes, J. C. Wallace, L. J. Cosgrove, and V. M. Macaulay. "Silencing of the Insulin Receptor Isoform A Favors Formation of Type 1 Insulin-Like Growth Factor Receptor (IGF-IR) Homodimers and Enhances Ligand-Induced IGF-IR Activation and Viability of Human Colon Carcinoma Cells." Endocrinology 151, no. 4 (February 23, 2010): 1418–27. http://dx.doi.org/10.1210/en.2009-1006.
Full textAbstract:
Insulin receptor (IR) overexpression is common in cancers, with expression of the A isoform (IR-A, exon 11−) predominating over the B isoform. The IR-A signals a proliferative, antiapoptotic response to IGF-II, which itself can be secreted by tumors to establish an autocrine proliferative loop. Therefore, IGF-II signaling via the IR-A could mediate resistance to type 1 IGF receptor (IGF-IR) inhibitory drugs that are currently in development. This study addressed the role of the IR-A, using a small interfering RNA-based approach in SW480 human colon adenocarcinoma cells that coexpress the IGF-IR. Clonogenic survival was inhibited by depletion of the IGF-IR but not the IR-A, and dual receptor depletion had no greater effect than IGF-IR knockdown alone, suggesting that the IR-A could not compensate for IGF-IR loss. IGF-IR knockdown also resulted in a decrease in viability, whereas IR-A depletion resulted in increased viability. Consistent with this, upon IR-A depletion, we found a concomitant enhancement of IGF-IR activation by IGF-I and IGF-II, reduced formation of IGF-IR:IR-A hybrid receptors and increased IGF-IR homodimer formation. Together, these results suggest that IGF bioactivity is mediated more effectively by the IGF-IR than by the IR-A or receptor hybrids and that signaling via the IGF-IR is dominant to the IR-A in colon cancer cells that express both receptors.
13
Dickson, Eamonn J., Björn H. Falkenburger, and Bertil Hille. "Quantitative properties and receptor reserve of the IP3 and calcium branch of Gq-coupled receptor signaling." Journal of General Physiology 141, no. 5 (April 29, 2013): 521–35. http://dx.doi.org/10.1085/jgp.201210886.
Full textAbstract:
Gq-coupled plasma membrane receptors activate phospholipase C (PLC), which hydrolyzes membrane phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). This leads to calcium release, protein kinase C (PKC) activation, and sometimes PIP2 depletion. To understand mechanisms governing these diverging signals and to determine which of these signals is responsible for the inhibition of KCNQ2/3 (KV7.2/7.3) potassium channels, we monitored levels of PIP2, IP3, and calcium in single living cells. DAG and PKC are monitored in our companion paper (Falkenburger et al. 2013. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201210887). The results extend our previous kinetic model of Gq-coupled receptor signaling to IP3 and calcium. We find that activation of low-abundance endogenous P2Y2 receptors by a saturating concentration of uridine 5′-triphosphate (UTP; 100 µM) leads to calcium release but not to PIP2 depletion. Activation of overexpressed M1 muscarinic receptors by 10 µM Oxo-M leads to a similar calcium release but also depletes PIP2. KCNQ2/3 channels are inhibited by Oxo-M (by 85%), but not by UTP (<1%). These differences can be attributed purely to differences in receptor abundance. Full amplitude calcium responses can be elicited even after PIP2 was partially depleted by overexpressed inducible phosphatidylinositol 5-phosphatases, suggesting that very low amounts of IP3 suffice to elicit a full calcium release. Hence, weak PLC activation can elicit robust calcium signals without net PIP2 depletion or KCNQ2/3 channel inhibition.
14
Yi, Ping, Ray-Chang Wu, Joshua Sandquist, Jiemin Wong, Sophia Y. Tsai, Ming-Jer Tsai, Anthony R. Means, and Bert W. O'Malley. "Peptidyl-Prolyl Isomerase 1 (Pin1) Serves as a Coactivator of Steroid Receptor by Regulating the Activity of Phosphorylated Steroid Receptor Coactivator 3 (SRC-3/AIB1)." Molecular and Cellular Biology 25, no. 21 (November 1, 2005): 9687–99. http://dx.doi.org/10.1128/mcb.25.21.9687-9699.2005.
Full textAbstract:
ABSTRACT Steroid receptor coactivator 3 (SRC-3/AIB1) interacts with steroid receptors in a ligand-dependent manner to activate receptor-mediated transcription. A number of intracellular signaling pathways initiated by growth factors and hormones induce phosphorylation of SRC-3, regulating its function and contributing to its oncogenic potential. However, the range of mechanisms by which phosphorylation affects coactivator function remains largely undefined. We demonstrate here that peptidyl-prolyl isomerase 1 (Pin1), which catalyzes the isomerization of phosphorylated Ser/Thr-Pro peptide bonds to induce conformational changes of its target proteins, interacts selectively with phosphorylated SRC-3. In addition, Pin1 and SRC-3 activate nuclear-receptor-regulated transcription synergistically. Depletion of Pin1 by small interfering RNA (siRNA) reduces hormone-dependent transcription from both transfected reporters and an endogenous steroid receptor target gene. We present evidence that Pin1 modulates interactions between SRC-3 and CBP/p300. The interaction is enhanced in vitro and in vivo by Pin1 and diminished when cellular Pin1 is reduced by siRNA or in stable Pin1-depleted cell lines. Depletion of Pin1 in MCF-7 human breast cancer cells reduces the endogenous estrogen-dependent recruitment of p300 to the promoters of estrogen receptor-dependent genes. Pin1 overexpression enhanced SRC-3 cellular turnover, and depletion of Pin1 stabilized SRC-3. Our results suggest that Pin1 functions as a transcriptional coactivator of nuclear receptors by modulating SRC-3 coactivator protein-protein complex formation and ultimately by also promoting the turnover of the activated SRC-3 oncoprotein.
15
Flórido, Manuela, John E. Pearl, Alejandra Solache, Margarida Borges, Laura Haynes, Andrea M. Cooper, and Rui Appelberg. "Gamma Interferon-Induced T-Cell Loss in Virulent Mycobacterium avium Infection." Infection and Immunity 73, no. 6 (June 2005): 3577–86. http://dx.doi.org/10.1128/iai.73.6.3577-3586.2005.
Full textAbstract:
ABSTRACT Infection by virulent Mycobacterium avium caused progressive severe lymphopenia in C57BL/6 mice due to increased apoptosis rates. T-cell depletion did not occur in gamma interferon (IFN-γ)-deficient mice which showed increased T-cell numbers and proliferation; in contrast, deficiency in nitric oxide synthase 2 did not prevent T-cell loss. Although T-cell loss was IFN-γ dependent, expression of the IFN-γ receptor on T cells was not required for depletion. Similarly, while T-cell loss was optimal if the T cells expressed IFN-γ, CD8+ T-cell depletion could occur in the absence of T-cell-derived IFN-γ. Depletion did not require that the T cells be specific for mycobacterial antigen and was not affected by deficiencies in the tumor necrosis factor receptors p55 or p75, the Fas receptor (CD95), or the respiratory burst enzymes or by forced expression of bcl-2 in hematopoietic cells.
16
BÖHM, Stephan K., Eileen F. GRADY, and Nigel W. BUNNETT. "Regulatory mechanisms that modulate signalling by G-protein-coupled receptors." Biochemical Journal 322, no. 1 (February 15, 1997): 1–18. http://dx.doi.org/10.1042/bj3220001.
Full textAbstract:
The large and functionally diverse group of G-protein-coupled receptors includes receptors for many different signalling molecules, including peptide and non-peptide hormones and neurotransmitters, chemokines, prostanoids and proteinases. Their principal function is to transmit information about the extracellular environment to the interior of the cell by interacting with the heterotrimeric G-proteins, and they thereby participate in many aspects of regulation. Cellular responses to agonists of these receptors are usually rapidly attenuated. Mechanisms of signal attenuation include removal of agonists from the extracellular fluid, receptor desensitization, endocytosis and down-regulation. Agonists are removed by dilution, uptake by transporters and enzymic degradation. Receptor desensitization is mediated by receptor phosphorylation by G-protein receptor kinases and second-messenger kinases, interaction of phosphorylated receptors with arrestins and receptor uncoupling from G-proteins. Agonist-induced receptor endocytosis also contributes to desensitization by depleting the cell surface of high-affinity receptors, and recycling of internalized receptors contributes to resensitization of cellular responses. Receptor down-regulation is a form of desensitization that occurs during continuous, long-term exposure of cells to receptor agonists. Down-regulation, which may occur during the development of drug tolerance, is characterized by depletion of the cellular receptor content, and is probably mediated by alterations in the rates of receptor degradation and synthesis. These regulatory mechanisms are important, as they govern the ability of cells to respond to agonists. A greater understanding of the mechanisms that modulate signalling may lead to the development of new therapies and may help to explain the mechanism of drug tolerance.
17
Yamazoe, Noboru, and Kengo Shimanoe. "Receptor Function and Response of Semiconductor Gas Sensor." Journal of Sensors 2009 (2009): 1–21. http://dx.doi.org/10.1155/2009/875704.
Full textAbstract:
Theoretical approaches to receptor function and response of semiconductor gas sensor are described, following the illustrations of some relevant key issues such as tunneling transport. Depletion in small semiconductor crystals is characterized by the occurrence of new type depletion (volume depletion) after conventional one (regional depletion), and inclusion of both types makes it possible to formulate the receptor function and response to oxygen (air base), oxidizing gas (nitrogen dioxide), and reducing gas (hydrogen). The equations derived theoretically using physical parameters of the semiconductor side and chemical parameters of the gases side appear to reproduce satisfactorily the sensing behavior to the aforementioned gases as well as the influence of changes in physical parameters such as grain size and donor density. Extension to the semiconductor crystals dispersed with surface electron-traps shows that the traps act as a sensitizer to promote sensor response.
18
Ara, Hosne, Susmita Bhattarai, Sudha Sharma, Utsab Subedi, Xiuping Yu, Md Shenuarin Bhuiyan, Sumitra Miriyala, and Manikandan Panchatcharam. "Abstract 5810: LPAR2 depletion suppresses gastric cancer via alteration of mitochondrial energy metabolism." Cancer Research 82, no. 12_Supplement (June 15, 2022): 5810. http://dx.doi.org/10.1158/1538-7445.am2022-5810.
Full textAbstract:
Abstract Introduction: Gastric cancer is the second most common cause of cancer-related death worldwide. Altered metabolism is considered a primary hallmark of tumorigenesis, as it can regulate important processes associated with proliferation, migration, and invasion. Lysophosphatidic acid (LPA), a multifunctional endogenous phospholipid, plays a vital role in cellular homeostasis and malignant behavior of the cancer cells through G-protein coupled receptors. Although several signaling pathways have been reported as a critical mediator of gastric cancer, LPA-LPAR2 axis-mediated alteration of energy metabolism in gastric cancer progression has not been established yet. Therefore, our study focused on the molecular mechanism of LPA-LPAR2 axis-mediated alteration of mitochondrial bioenergetics during gastric cancer progression. Method: TCGA database analysis was carried out to check the mRNA levels of the LPA receptors. Expression of LPA receptors was investigated in human gastric cancer samples by immunoblotting, RT-PCR, and immunohistochemical analysis. We elucidated the functional effects of LPA on gastric cancer by performing ECIS proliferation, migration assay, scratch assay, and transwell invasion assay in gastric cancer cells. To confirm the involvement of the specific LPA receptor on gastric cancer progression, we treated the cells with LPA1-3 receptor blocker (Ki16425) and LPA2 receptor-specific antagonist. Following LPA receptor blockade, we analyzed the glycolytic and mitochondrial functions by measuring extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) using a Seahorse XF24 analyzer. Result: Our TCGA dataset analysis, LPA ELISA, and the Western blotting result showed the presence of LPA receptors in human gastric cancer tissues, specifically LPAR2 was robustly increased (P<0.001) in human gastric cancer tissue samples, and LPA level was significantly higher (P<0.001), suggesting a possible role of LPA in gastric cancer. LPA treatment increased proliferation, migration, and invasion activity in AGS and NCI-N87 gastric cancer cell lines. In contrast, LPA receptor antagonist Ki16425 abrogated the LPA-induced effect. Our seahorse analysis results showed that LPA treatment increased the OCR (P<0.001) and the ECAR (P<0.001), whereas LPAR2 specific receptor antagonists abrogated this effect (P<0.001). Conclusion: Together, our results suggested that the LPA-LPAR2 axis mediates gastric cancer initiation and progression by increasing energy metabolism via oxidative phosphorylation and glycolysis. Thus, targeting the LPAR2 receptor may give us a novel therapeutic approach to treat gastric cancer. Citation Format: Hosne Ara, Susmita Bhattarai, Sudha Sharma, Utsab Subedi, Xiuping Yu, Md. Shenuarin Bhuiyan, Sumitra Miriyala, Manikandan Panchatcharam. LPAR2 depletion suppresses gastric cancer via alteration of mitochondrial energy metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5810.
19
WILLARS, Gary B., Craig A. McARDLE, and Stefan R. NAHORSKI. "Acute desensitization of phospholipase C-coupled muscarinic M3 receptors but not gonadotropin-releasing hormone receptors co-expressed in αT3-1 cells: implications for mechanisms of rapid desensitization." Biochemical Journal 333, no. 2 (July 15, 1998): 301–8. http://dx.doi.org/10.1042/bj3330301.
Full textAbstract:
In the present study we have expressed the muscarinic M3 receptor in an immortalized mouse pituitary cell line (αT3-1), which expresses an endogenous gonadotropin-releasing hormone (GnRH) receptor, to examine potential differences in acute receptor regulation. Both of these receptors couple to the activation of phosphoinositide-specific phospholipase C (PLC) in these cells and we demonstrate that, despite expression in the same cell background, acute desensitization is a feature of muscarinic M3 receptors but not of GnRH receptors. We show that, when the concentrations of GnRH and methacholine are matched to give approximately equivalent maximal elevations of Ins(1,4,5)P3, the GnRH receptor is able to sustain PLC activity at the initial rate, whereas the muscarinic M3 receptor cannot. Thus PLC-activating G-protein-coupled receptors are able to undergo rapid desensitization in this cell line, indicating that the desensitization profile is receptor-specific rather than cell-specific. This argues strongly that post-receptor regulatory features do not have a prominent role in mediating rapid desensitization in these cells. Furthermore GnRH receptor-mediated PLC activity is sustained despite a marked and persistent depletion in the steady-state level of PtdIns(4,5)P2. In contrast, activation of muscarinic receptors is not sustained despite only a transient decrease in PtdIns(4,5)P2 concentration. Thus, whereas the contribution of PtdIns(4,5)P2 depletion to the temporal profile of receptor-mediated PLC signalling has been difficult to assess, the present results demonstrate that this is unlikely to be of importance in these cells. We suggest that unique structural features of the GnRH receptor result in a lack of appropriate regulatory phospho-acceptor sites and that the absence of agonist-dependent phosphorylation might underlie the lack of acute regulation.
20
McNeely, Patrick M., Andrea N. Naranjo, Kimberly Forsten-Williams, and Anne Skaja Robinson. "A2AR Binding Kinetics in the Ligand Depletion Regime." SLAS DISCOVERY: Advancing the Science of Drug Discovery 22, no. 2 (September 27, 2016): 166–75. http://dx.doi.org/10.1177/1087057116667256.
Full textAbstract:
Ligand binding plays a fundamental role in stimulating the downstream signaling of membrane receptors. Here, ligand-binding kinetics of the full-length human adenosine A2A receptor (A2AR) reconstituted in detergent micelles were measured using a fluorescently labeled ligand via fluorescence anisotropy. Importantly, to optimize the signal-to-noise ratio, these experiments were conducted in the ligand depletion regime. In the ligand depletion regime, the assumptions used to determine analytical solutions for one-site binding models for either one or two ligands in competition are no longer valid. We therefore implemented a numerical solution approach to analyze kinetic binding data as experimental conditions approach the ligand depletion regime. By comparing the results from the numerical and the analytical solutions, we highlight the ligand-receptor ratios at which the analytical solution begins to lose predictive accuracy. Using the numerical solution approach, we determined the kinetic rate constants of the fluorescent ligand, FITC-APEC, and those for three unlabeled ligands using competitive association experiments. The association and dissociation rate constants of the unlabeled ligands determined from the competitive association experiments were then independently validated using competitive dissociation data. Based on this study, a numerical solution is recommended to determine kinetic ligand-binding parameters for experiments conducted in the ligand-depletion regime.
21
Falkenburger, Björn H., Eamonn J. Dickson, and Bertil Hille. "Quantitative properties and receptor reserve of the DAG and PKC branch of Gq-coupled receptor signaling." Journal of General Physiology 141, no. 5 (April 29, 2013): 537–55. http://dx.doi.org/10.1085/jgp.201210887.
Full textAbstract:
Gq protein–coupled receptors (GqPCRs) of the plasma membrane activate the phospholipase C (PLC) signaling cascade. PLC cleaves the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers diacylgycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), leading to calcium release, protein kinase C (PKC) activation, and in some cases, PIP2 depletion. We determine the kinetics of each of these downstream endpoints and also ask which is responsible for the inhibition of KCNQ2/3 (KV7.2/7.3) potassium channels in single living tsA-201 cells. We measure DAG production and PKC activity by Förster resonance energy transfer–based sensors, and PIP2 by KCNQ2/3 channels. Fully activating endogenous purinergic receptors by uridine 5′triphosphate (UTP) leads to calcium release, DAG production, and PKC activation, but no net PIP2 depletion. Fully activating high-density transfected muscarinic receptors (M1Rs) by oxotremorine-M (Oxo-M) leads to similar calcium, DAG, and PKC signals, but PIP2 is depleted. KCNQ2/3 channels are inhibited by the Oxo-M treatment (85%) and not by UTP (<1%), indicating that depletion of PIP2 is required to inhibit KCNQ2/3 in response to receptor activation. Overexpression of A kinase–anchoring protein (AKAP)79 or calmodulin (CaM) does not increase KCNQ2/3 inhibition by UTP. From these results and measurements of IP3 and calcium presented in our companion paper (Dickson et al. 2013. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201210886), we extend our kinetic model for signaling from M1Rs to DAG/PKC and IP3/calcium signaling. We conclude that calcium/CaM and PKC-mediated phosphorylation do not underlie dynamic KCNQ2/3 channel inhibition during GqPCR activation in tsA-201 cells. Finally, our experimental data provide indirect evidence for cleavage of PI(4)P by PLC in living cells, and our modeling revisits/explains the concept of receptor reserve with measurements from all steps of GqPCR signaling.
22
Backer, J. M., S. E. Shoelson, E. Haring, and M. F. White. "Insulin receptors internalize by a rapid, saturable pathway requiring receptor autophosphorylation and an intact juxtamembrane region." Journal of Cell Biology 115, no. 6 (December 15, 1991): 1535–45. http://dx.doi.org/10.1083/jcb.115.6.1535.
Full textAbstract:
The effect of receptor occupancy on insulin receptor endocytosis was examined in CHO cells expressing normal human insulin receptors (CHO/IR), autophosphorylation- and internalization-deficient receptors (CHO/IRA1018), and receptors which undergo autophosphorylation but lack a sequence required for internalization (CHO/IR delta 960). The rate of [125I]insulin internalization in CHO/IR cells at 37 degrees C was rapid at physiological concentrations, but decreased markedly in the presence of increasing unlabeled insulin (ED50 = 1-3 nM insulin, or 75,000 occupied receptors/cell). In contrast, [125I]insulin internalization by CHO/IRA1018 and CHO/IR delta 960 cells was slow and was not inhibited by unlabeled insulin. At saturating insulin concentrations, the rate of internalization by wild-type and mutant receptors was similar. Moreover, depletion of intracellular potassium, which has been shown to disrupt coated pit formation, inhibited the rapid internalization of [125I]insulin at physiological insulin concentrations by CHO/IR cells, but had little or no effect on [125I]insulin uptake by CHO/IR delta 960 and CHO/IRA1018 cells or wild-type cells at high insulin concentrations. These data suggest that the insulin-stimulated entry of the insulin receptor into a rapid, coated pit-mediated internalization pathway is saturable and requires receptor autophosphorylation and an intact juxtamembrane region. Furthermore, CHO cells also contain a constitutive nonsaturable pathway which does not require receptor autophosphorylation or an intact juxtamembrane region; this second pathway is unaffected by depletion of intracellular potassium, and therefore may be independent of coated pits. Our data suggest that the ligand-stimulated internalization of the insulin receptor may require specific saturable interactions between the receptor and components of the endocytic system.
23
Meinsohn, Marie-Charlotte, Olivia E. Smith, Kalyne Bertolin, and Bruce D. Murphy. "The Orphan Nuclear Receptors Steroidogenic Factor-1 and Liver Receptor Homolog-1: Structure, Regulation, and Essential Roles in Mammalian Reproduction." Physiological Reviews 99, no. 2 (April 1, 2019): 1249–79. http://dx.doi.org/10.1152/physrev.00019.2018.
Full textAbstract:
Nuclear receptors are intracellular proteins that act as transcription factors. Proteins with classic nuclear receptor domain structure lacking identified signaling ligands are designated orphan nuclear receptors. Two of these, steroidogenic factor-1 (NR5A1, also known as SF-1) and liver receptor homolog-1 (NR5A2, also known as LRH-1), bind to the same DNA sequences, with different and nonoverlapping effects on targets. Endogenous regulation of both is achieved predominantly by cofactor interactions. SF-1 is expressed primarily in steroidogenic tissues, LRH-1 in tissues of endodermal origin and the gonads. Both receptors modulate cholesterol homeostasis, steroidogenesis, tissue-specific cell proliferation, and stem cell pluripotency. LRH-1 is essential for development beyond gastrulation and SF-1 for genesis of the adrenal, sexual differentiation, and Leydig cell function. Ovary-specific depletion of SF-1 disrupts follicle development, while LRH-1 depletion prevents ovulation, cumulus expansion, and luteinization. Uterine depletion of LRH-1 compromises decidualization and pregnancy. In humans, SF-1 is present in endometriotic tissue, where it regulates estrogen synthesis. SF-1 is underexpressed in ovarian cancer cells and overexpressed in Leydig cell tumors. In breast cancer cells, proliferation, migration and invasion, and chemotherapy resistance are regulated by LRH-1. In conclusion, the NR5A orphan nuclear receptors are nonredundant factors that are crucial regulators of a panoply of biological processes, across multiple reproductive tissues.
24
Siragy, H. M., and R. M. Carey. "The subtype 2 angiotensin receptor regulates renal prostaglandin F2 alpha formation in conscious rats." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 273, no. 3 (September 1, 1997): R1103—R1107. http://dx.doi.org/10.1152/ajpregu.1997.273.3.r1103.
Full textAbstract:
The angiotensin AT1 receptor mediates renal prostaglandin (PG) E2 production through stimulation of phospholipase A2. Blockade of the AT2 receptor potentiates the angiotensin II-induced increase in PGE2 levels. In the kidney, PGE2 is converted to PGF2 alpha mainly by the enzyme PGE 9-ketoreductase. We hypothesized that the conversion of PGE2 to PGF2 alpha is inhibited by AT2 receptor blockade, resulting in the observed increase in PGE2 levels. Using a microdialysis technique, we monitored changes in renal interstitial fluid PGE2 and PGF2 alpha in response to 5 days of sodium depletion alone or a combination of sodium depletion and intravenous infusion of the AT1 receptor blocker losartan or the AT2 receptor blocker PD-123319 in conscious rats. We utilized the PGF2 alpha-to-PGE2 ratio as an indirect measure of the rate of renal PGF2 alpha formation. Sodium depletion increased PGE2, PGF2 alpha, and the PGF2 alpha-to-PGE2 ratio. During sodium depletion, losartan decreased PGE2 and PGF2 alpha and did not change the PGF2 alpha-to-PGE2 ratio. In contrast, PD-123319 increased PGE2, decreased PGF2 alpha, and decreased the PGF2 alpha-to-PGE2 ratio. These data demonstrate that activation of the renin-angiotensin system during sodium depletion physiologically increases renal conversion of PGE2 to PGF2 alpha. The increase in renal production of PGF2 alpha is mediated through stimulation of the angiotensin AT2 receptor.
25
Marala, R. B., and S. J. Mustafa. "Adenosine analogues prevent phorbol ester-induced PKC depletion in porcine coronary artery via A1 receptor." American Journal of Physiology-Heart and Circulatory Physiology 268, no. 1 (January 1, 1995): H271—H277. http://dx.doi.org/10.1152/ajpheart.1995.268.1.h271.
Full textAbstract:
This study was undertaken to determine the adenosine receptor involved in the modulation of protein kinase C (PKC) in porcine coronary artery. Endothelium-denuded arterial rings were incubated with phorbol 12,13-dibutyrate (PDBu) in the presence or absence of adenosine receptor agonists and antagonists for 24 h. After incubation, contractile responses to endothelin-1 (ET-1) were compared in various treatment groups. Arterial rings incubated with PDBu alone failed to produce significant contractions in response to ET-1. (2s)-N6-[2-endo-norbornyl]adenosine (ENBA), an A1-receptor agonist, attenuated the PDBu-induced blunting of the ET-1 contractions. Incubation with ENBA alone elevated ET-1 contractility by about twofold. Inclusion of A1-receptor antagonists completely blocked both effects of ENBA: protection against PDBu and increase in ET-1 contractility. On the contrary, arterial rings incubated with the A2-receptor agonist 2-p-(2-carboxyethyl)phenethyl-amino-5'-N-ethylcarboxamidoadenosine (CGS-21680) did not show significant alteration of the ET-1 contractility when incubated with CGS-21680 alone or in combination with PDBu. Inclusion of A2-receptor antagonist in combination with CGS-21680 mimicked the effects of ENBA alone, i.e., protected against PDBu and enhanced ET-1 contractions. Measurement of PKC activities in arteries indicated that exposure to ENBA caused a twofold increase in the enzyme activity, whereas exposure to CGS-21680 had no significant effect on PKC activity. Adenosine analogues caused an accumulation of PKC through the activation of A1- but not A2-adenosine receptors. These results indicate that the modulation of PKC by adenosine analogues is mediated through A1-adenosine receptors in the coronary artery.
26
Carter, Clare M. Scaramellini, Juliet R. Leighton-Davies, and Steven J. Charlton. "Miniaturized Receptor Binding Assays: Complications Arising from Ligand Depletion." Journal of Biomolecular Screening 12, no. 2 (January 11, 2007): 255–66. http://dx.doi.org/10.1177/1087057106297788.
Full textAbstract:
The advent of miniaturized assay formats has made possible the screening of large numbers of compounds against a single target, known as high-throughput screening. Despite this clear advantage, assay miniaturization also increases the risk of ligand depletion, where the actual concentration of free ligand is significantly lower than that added. This, in turn, complicates the interpretation of data from such assays, potentially introducing significant error if not recognized. In this study, the effects of reducing assay volume on radioligand Kd and competitor Ki values have been investigated, using the muscarinic M3 receptor as a model system. It was found that assay miniaturization caused dramatic effects, with up to a 30-fold underestimation of ligand affinity. A theoretical model was developed and shown to accurately predict both the degree of ligand depletion in any given assay volume and the effect of this depletion on affinity estimates for competing ligands. Importantly, it was found that in most cases, errors introduced by ligand depletion could be largely corrected for by the use of appropriate analysis methods. In addition to those previously described by others, the authors propose a simple method capable of correcting errors in competition binding experiments performed in conditions of ligand depletion.
27
Mamińska, Agnieszka, Anna Bartosik, Magdalena Banach-Orłowska, Iwona Pilecka, Kamil Jastrzębski, Daria Zdżalik-Bielecka, Irinka Castanon, et al. "ESCRT proteins restrict constitutive NF-κB signaling by trafficking cytokine receptors." Science Signaling 9, no. 411 (January 19, 2016): ra8. http://dx.doi.org/10.1126/scisignal.aad0848.
Full textAbstract:
Because signaling mediated by the transcription factor nuclear factor κB (NF-κB) is initiated by ligands and receptors that can undergo internalization, we investigated how endocytic trafficking regulated this key physiological pathway. We depleted all of the ESCRT (endosomal sorting complexes required for transport) subunits, which mediate receptor trafficking and degradation, and found that the components Tsg101, Vps28, UBAP1, and CHMP4B were essential to restrict constitutive NF-κB signaling in human embryonic kidney 293 cells. In the absence of exogenous cytokines, depletion of these proteins led to the activation of both canonical and noncanonical NF-κB signaling, as well as the induction of NF-κB–dependent transcriptional responses in cultured human cells, zebrafish embryos, and fat bodies in flies. These effects depended on cytokine receptors, such as the lymphotoxin β receptor (LTβR) and tumor necrosis factor receptor 1 (TNFR1). Upon depletion of ESCRT subunits, both receptors became concentrated on and signaled from endosomes. Endosomal accumulation of LTβR induced its ligand-independent oligomerization and signaling through the adaptors TNFR-associated factor 2 (TRAF2) and TRAF3. These data suggest that ESCRTs constitutively control the distribution of cytokine receptors in their ligand-free state to restrict their signaling, which may represent a general mechanism to prevent spurious activation of NF-κB.
28
Miyamoto, Takashi, Daniel Kim, Joseph A. Knox, Erik Johnson, and Lennart Mucke. "Increasing the Receptor Tyrosine Kinase EphB2 Prevents Amyloid-β-induced Depletion of Cell Surface Glutamate Receptors by a Mechanism That Requires the PDZ-binding Motif of EphB2 and Neuronal Activity." Journal of Biological Chemistry 291, no. 4 (November 20, 2015): 1719–34. http://dx.doi.org/10.1074/jbc.m115.666529.
Full textAbstract:
Diverse lines of evidence suggest that amyloid-β (Aβ) peptides causally contribute to the pathogenesis of Alzheimer disease (AD), the most frequent neurodegenerative disorder. However, the mechanisms by which Aβ impairs neuronal functions remain to be fully elucidated. Previous studies showed that soluble Aβ oligomers interfere with synaptic functions by depleting NMDA-type glutamate receptors (NMDARs) from the neuronal surface and that overexpression of the receptor tyrosine kinase EphB2 can counteract this process. Through pharmacological treatments and biochemical analyses of primary neuronal cultures expressing wild-type or mutant forms of EphB2, we demonstrate that this protective effect of EphB2 depends on its PDZ-binding motif and the presence of neuronal activity but not on its kinase activity. We further present evidence that the protective effect of EphB2 may be mediated by the AMPA-type glutamate receptor subunit GluA2, which can become associated with the PDZ-binding motif of EphB2 through PDZ domain-containing proteins and can promote the retention of NMDARs in the membrane. In addition, we show that the Aβ-induced depletion of surface NMDARs does not depend on several factors that have been implicated in the pathogenesis of Aβ-induced neuronal dysfunction, including aberrant neuronal activity, tau, prion protein (PrPC), and EphB2 itself. Thus, although EphB2 does not appear to be directly involved in the Aβ-induced depletion of NMDARs, increasing its expression may counteract this pathogenic process through a neuronal activity- and PDZ-dependent regulation of AMPA-type glutamate receptors.
29
Huang, Steve, Sergey Apasov, Masahiro Koshiba, and Michail Sitkovsky. "Role of A2a Extracellular Adenosine Receptor-Mediated Signaling in Adenosine-Mediated Inhibition of T-Cell Activation and Expansion." Blood 90, no. 4 (August 15, 1997): 1600–1610. http://dx.doi.org/10.1182/blood.v90.4.1600.
Full textAbstract:
Abstract Accumulation of adenosine and of deoxyadenosine in the absence of adenosine deaminase activity (ADA) activity results in lymphocyte depletion and in severe combined immunodeficiency (ADA SCID), which is currently explained by direct cell death-causing effects of intracellular products of adenosine metabolism. We explored the alternative mechanisms of peripheral T-cell depletion as due to inhibition of T-cell expansion by extracellular adenosine-mediated signaling through purinergic receptors. The strong inhibition of the T-cell receptor (TCR)-triggered proliferation and of upregulation of interleukin-2 receptor α chain (CD25) molecules, but not the direct lymphotoxicity, were observed at low concentrations of extracellular adenosine. These effects of extracellular adenosine (Ado) are likely to be mediated by A2a receptor-mediated signaling rather than by intracellular toxicity of adenosine catabolites, because (1) poorly metabolized adenosine analogs cause the accumulation of cAMP and strong inhibition of TCR-triggered CD25 upregulation; (2) the A2a, but not the A1 or A3, receptors are the major expressed and functionally coupled adenosine receptors in mouse peripheral T and B lymphocytes, and the adenosine-induced cAMP accumulation in lymphocytes correlates with the expression of A2a receptors; (3) the specific agonist of A2a receptor, CGS21680, induces increases in [cAMP]i in lymphocytes, whereas the specific antagonist of A2a receptor, CSC, inhibits the effects of Ado and CGS21680; and (4) the increases in [cAMP]i mimic the adenosine-induced inhibition of TCR-triggered CD25 upregulation and splenocyte proliferation. These studies suggest the possible role of adenosine receptors in the regulation of lymphocyte expansion and point to the downregulation of A2a purinergic receptors on T cells as a potentially attractive pharmacologic target.
30
Huang, Steve, Sergey Apasov, Masahiro Koshiba, and Michail Sitkovsky. "Role of A2a Extracellular Adenosine Receptor-Mediated Signaling in Adenosine-Mediated Inhibition of T-Cell Activation and Expansion." Blood 90, no. 4 (August 15, 1997): 1600–1610. http://dx.doi.org/10.1182/blood.v90.4.1600.1600_1600_1610.
Full textAbstract:
Accumulation of adenosine and of deoxyadenosine in the absence of adenosine deaminase activity (ADA) activity results in lymphocyte depletion and in severe combined immunodeficiency (ADA SCID), which is currently explained by direct cell death-causing effects of intracellular products of adenosine metabolism. We explored the alternative mechanisms of peripheral T-cell depletion as due to inhibition of T-cell expansion by extracellular adenosine-mediated signaling through purinergic receptors. The strong inhibition of the T-cell receptor (TCR)-triggered proliferation and of upregulation of interleukin-2 receptor α chain (CD25) molecules, but not the direct lymphotoxicity, were observed at low concentrations of extracellular adenosine. These effects of extracellular adenosine (Ado) are likely to be mediated by A2a receptor-mediated signaling rather than by intracellular toxicity of adenosine catabolites, because (1) poorly metabolized adenosine analogs cause the accumulation of cAMP and strong inhibition of TCR-triggered CD25 upregulation; (2) the A2a, but not the A1 or A3, receptors are the major expressed and functionally coupled adenosine receptors in mouse peripheral T and B lymphocytes, and the adenosine-induced cAMP accumulation in lymphocytes correlates with the expression of A2a receptors; (3) the specific agonist of A2a receptor, CGS21680, induces increases in [cAMP]i in lymphocytes, whereas the specific antagonist of A2a receptor, CSC, inhibits the effects of Ado and CGS21680; and (4) the increases in [cAMP]i mimic the adenosine-induced inhibition of TCR-triggered CD25 upregulation and splenocyte proliferation. These studies suggest the possible role of adenosine receptors in the regulation of lymphocyte expansion and point to the downregulation of A2a purinergic receptors on T cells as a potentially attractive pharmacologic target.
31
Kang, Yuan-Lin, John Yochem, Leslie Bell, Erika B. Sorensen, Lihsia Chen, and Sean D. Conner. "Caenorhabditis elegans reveals a FxNPxY-independent low-density lipoprotein receptor internalization mechanism mediated by epsin1." Molecular Biology of the Cell 24, no. 3 (February 2013): 308–18. http://dx.doi.org/10.1091/mbc.e12-02-0163.
Full textAbstract:
Low-density lipoprotein receptor (LDLR) internalization clears cholesterol-laden LDL particles from circulation in humans. Defects in clathrin-dependent LDLR endocytosis promote elevated serum cholesterol levels and can lead to atherosclerosis. However, our understanding of the mechanisms that control LDLR uptake remains incomplete. To identify factors critical to LDLR uptake, we pursued a genome-wide RNA interference screen using Caenorhabditis elegans LRP-1/megalin as a model for LDLR transport. In doing so, we discovered an unanticipated requirement for the clathrin-binding endocytic adaptor epsin1 in LDLR endocytosis. Epsin1 depletion reduced LDLR internalization rates in mammalian cells, similar to the reduction observed following clathrin depletion. Genetic and biochemical analyses of epsin in C. elegans and mammalian cells uncovered a requirement for the ubiquitin-interaction motif (UIM) as critical for receptor transport. As the epsin UIM promotes the internalization of some ubiquitinated receptors, we predicted LDLR ubiquitination as necessary for endocytosis. However, engineered ubiquitination-impaired LDLR mutants showed modest internalization defects that were further enhanced with epsin1 depletion, demonstrating epsin1-mediated LDLR endocytosis is independent of receptor ubiquitination. Finally, we provide evidence that epsin1-mediated LDLR uptake occurs independently of either of the two documented internalization motifs (FxNPxY or HIC) encoded within the LDLR cytoplasmic tail, indicating an additional internalization mechanism for LDLR.
32
Shah, Prexy, Steven Justiniano, Robert Dunn, David Jarjoura, John Byrd, Jon Butchar, and Susheela Tridandapani. "Toll-like receptor 2 ligands enhance monocyte Fcγ receptor function (68.16)." Journal of Immunology 188, no. 1_Supplement (May 1, 2012): 68.16. http://dx.doi.org/10.4049/jimmunol.188.supp.68.16.
Full textAbstract:
Abstract Fcγ receptors (FcγR) are major effectors of antibody therapy so it is critical to seek new ways to enhance their effectivness. Toll-like receptors (TLR) recognize a wide range of microbial components, eliciting cellular responses such as cytokine production and generation of antimicrobial factors. Among these receptors, TLR2 recognizes both bacterial and fungal components. Given the strong cellular proinflammatory responses to TLR2 activation, we explored the possibility that TLR2 agonists could strengthen FcγR activity. Human peripheral blood monocytes (PBM) were treated with or without the TLR2 agonist PAM2CSK4 and tested for FcγR expression and function. Results showed that overnight treatment with PAM2CSK4 led to an increase in the expression of both FcγRIIa and the common γ-subunit, while expression of the inhibitory receptor FcγRIIb remained unchanged. Along with this, PAM2CSK4 significantly increased IgG-mediated TNFα production in plate-bound assays. We then tested its effect on phagocytosis, using fluorescently-labeled opsonized sheep red blood cells as targets. PAM2CSK4 significantly enhanced the phagocytic ability of PBM. To test the effect of PAM2CSK4 in vivo, we injected it in combination with anti-CD20 antibody and measured B-cell depletion. Results showed that PAM2CSK4 led to greater depletion of splenic B cells. These findings suggest that TLR2 agonists modulate FcγR expression and function and should be investigated as possible adjuvants for antibody therapy.
33
Sungur, Can, Maite Alvarez, Yajarayma Tang-Feldman, Lewis Lanier, Claire Pomeroy, and William Murphy. "Evidence for NK cell subset licensing in anti-viral and anti-leukemic responses after syngeneic hematopoietic stem cell transplantation in mice (169.10)." Journal of Immunology 186, no. 1_Supplement (April 1, 2011): 169.10. http://dx.doi.org/10.4049/jimmunol.186.supp.169.10.
Full textAbstract:
Abstract Natural killer (NK) cells are an initial defense against cancers and viruses and can be classified into subsets based on their expression of receptors. These subsets are considered “licensed” if inhibitory receptors are capable of binding host MHC I and “unlicensed” if not. Since in vivo data on licensing and subsets are limited, our studies aim to show licensing in tumor and viral models as well as elucidate the roles of NK subsets in a post-hematopoietic stem cell transplantation (HSCT) setting. We have recently observed that cells bearing the Ly49G2 inhibitory receptor predominated post-HSCT regardless of MHC I haplotype. Additionally, studies in resting mice indicated that the unlicensed subset is the major mediator of murine cytomegalovirus (MCMV) protection. Surprisingly, we have found that depleting unlicensed, Ly49G2+, NK cells from leukemia (C1498) bearing, H2b strain mice after syngeneic HSCT significantly improved survival of mice, while depleting the licensed subset, Ly49C/I+, decreased survival. Furthermore, depletion of the Ly49C/I+ subset resulted in significantly increased viral loads in the liver, spleen, and salivary glands in H2b strain mice infected with MCMV 14 days post-HSCT. Conversely, depletion of the unlicensed ly49G2+ subset resulted in only a minor increase in viral load. Collectively, these data support the importance of NK licensing in tumor and viral models post-HSCT and suggest a regulatory role for the unlicensed subsets.
34
Chattopadhyay, Amitabha, Md Jafurulla, and Thomas J. Pucadyil. "Ligand Binding and G-protein Coupling of the Serotonin1A Receptor in Cholesterol-enriched Hippocampal Membranes." Bioscience Reports 26, no. 2 (June 22, 2006): 79–87. http://dx.doi.org/10.1007/s10540-006-9009-9.
Full textAbstract:
The serotonin1A receptor is the most extensively studied member of the family of seven transmembrane domain G-protein coupled serotonin receptors. Since a large portion of such transmembrane receptors remains in contact with the membrane lipid environment, lipid–protein interactions assume importance in the structure-function analysis of such receptors. We have earlier reported the requirement of cholesterol for serotonin1A receptor function in native hippocampal membranes by specific depletion of cholesterol using methyl- β-cyclodextrin. In this paper, we monitored the serotonin1A receptor function in membranes that are enriched in cholesterol using a complex prepared from cholesterol and methyl-β-cyclodextrin. Our results indicate that ligand binding and receptor/G-protein interaction of the serotonin1A receptor do not exhibit significant difference in native and cholesterol-enriched hippocampal membranes indicating that further enrichment of cholesterol has little functional consequence on the serotonin1A receptor function. These results therefore provide new information on the effect of cholesterol enrichment on the hippocampal serotonin1A receptor function.
35
Hinson, J. P., and S. Kapas. "Effects of sodium depletion on the response of rat adrenal zona glomerulosa cells to stimulation by neuropeptides: actions of vasoactive intestinal peptide, enkephalin, substance P, neuropeptide Y and corticotrophin-releasing hormone." Journal of Endocrinology 146, no. 2 (August 1995): 209–14. http://dx.doi.org/10.1677/joe.0.1460209.
Full textAbstract:
Abstract There are several neuropeptides, present in nerves supplying the rat adrenal zona glomerulosa, which have been shown to stimulate aldosterone secretion in the intact perfused rat adrenal preparation. The purpose of the present study was twofold: first, to determine whether these peptides acted directly on adrenocortical cells by examining their effects on collagenase-dispersed rat zona glomerulosa cells, and second, to investigate the likely physiological significance of these actions, by determining whether the responses of zona glomerulosa cells to neuropeptides were changed by prior sodium depletion. Of the peptides tested, neuropeptide Y (NPY) and substance P had only a minor effect on aldosterone secretion, which was not substantially affected by sodium depletion. Corticotrophin-releasing hormone (CRH) had a significant stimulatory effect on aldosterone secretion, but neither the threshold concentration for significant stimulation nor the maximal response to stimulation were altered by prior sodium depletion. Vasoactive intestinal peptide (VIP), on the other hand, had little effect on aldosterone secretion by cells from normal animals, but was a potent stimulus to aldosterone secretion in cells obtained from sodium-depleted animals. The response to the Met-enkephalin analogue, [d-Ala2-Met2]-enkephalinamide (DALA), was also significantly enhanced by prior sodium depletion. Experiments using the angiotensin II receptor blocker, saralasin, were carried out to determine whether the enhanced actions of DALA and VIP seen in sodium depletion may be a result of activation of angiotensin II receptors, known to be increased in sodium depletion. Saralasin did not affect the response to either peptide. These data suggest that all the peptides tested may be able to stimulate aldosterone secretion. However, the data obtained with substance P, NPY and CRH do not support a major role for these peptides in the regulation of aldosterone secretion either under control conditions, or in sodium depletion. The finding that the responses to VIP and DALA were altered by sodium depletion suggests that the actions of VIP and opioid peptides may have physiological significance in the regulation of aldosterone secretion in response to sodium depletion. Furthermore, the observation that saralasin does not inhibit the responses to these peptides strongly suggests that they are not acting through angiotensin II receptors, and may indicate altered VIP- and opioid-receptor regulation in sodium depletion. Journal of Endocrinology (1995) 146, 209–214
36
Maneepak, Montree, Supang le Grand, and Anan Srikiatkhachorn. "Serotonin Depletion Increases Nociception-Evoked Trigeminal NMDA Receptor Phosphorylation." Headache: The Journal of Head and Face Pain 49, no. 3 (March 2009): 375–82. http://dx.doi.org/10.1111/j.1526-4610.2009.01341.x.
Full text
37
Migliaccio, G., CV Nicchitta, and G. Blobel. "The signal sequence receptor, unlike the signal recognition particle receptor, is not essential for protein translocation." Journal of Cell Biology 117, no. 1 (April 1, 1992): 15–25. http://dx.doi.org/10.1083/jcb.117.1.15.
Full textAbstract:
Detergent extracts of canine pancreas rough microsomal membranes were depleted of either the signal recognition particle receptor (SR), which mediates the signal recognition particle (SRP)-dependent targeting of the ribosome/nascent chain complex to the membrane, or the signal sequence receptor (SSR), which has been proposed to function as a membrane bound receptor for the newly targeted nascent chain and/or as a component of a multi-protein translocation complex responsible for transfer of the nascent chain across the membrane. Depletion of the two components was performed by chromatography of detergent extracts on immunoaffinity supports. Detergent extracts lacking either SR or SSR were reconstituted and assayed for activity with respect to SR dependent elongation arrest release, nascent chain targeting, ribosome binding, secretory precursor translocation, and membrane protein integration. Depletion of SR resulted in the loss of elongation arrest release activity, nascent chain targeting, secretory protein translocation, and membrane protein integration, although ribosome binding was unaffected. Full activity was restored by addition of immunoaffinity purified SR before reconstitution of the detergent extract. Surprisingly, depletion of SSR was without effect on any of the assayed activities, indicating that SSR is either not required for translocation or is one of a family of functionally redundant components.
38
Őrfi, Erik, László Hricisák, László Dézsi, Péter Hamar, Zoltán Benyó, János Szebeni, and Gábor Szénási. "The Hypertensive Effect of Amphotericin B-Containing Liposomes (Abelcet) in Mice: Dissecting the Roles of C3a and C5a Anaphylatoxins, Macrophages and Thromboxane." Biomedicines 10, no. 7 (July 21, 2022): 1764. http://dx.doi.org/10.3390/biomedicines10071764.
Full textAbstract:
Liposomal amphotericin B (Abelcet) can cause infusion (anaphylactoid) reactions in patients whose mechanism is poorly understood. Here, we used mice to investigate the role of complement (C) receptors and the cellular sources of vasoactive mediators in these reactions. Anesthetized male NMRI and thromboxane prostanoid receptor (TP) or cyclooxygenase-1 (COX-1)-deficient and wild type C57Bl6/N mice were intravenously injected with Abelcet at 30 mg/kg. Mean arterial blood pressure (MABP) and heart rate (HR) were measured. In untreated mice, Abelcet caused a short (15 min) but large (30%) increase in MABP. C depletion with cobra venom factor (CVF) and inhibition of C5a receptors with DF2593A considerably prolonged, while C3aR inhibition with SB290157 significantly decreased the hypertensive effect. Likewise, the hypertensive response was abolished in COX-1- and TP-deficient mice. CVF caused a late hypertension in TP-deficient mice. Both macrophage depletion with liposomal clodronate and blockade of platelet GPIIb/IIIa receptors with eptifibatide prolonged the hypertensive effect. The early phase of the hypertensive effect is COX-1- and TP-receptor-dependent, partly mediated by C3aR. In contrast, the late phase is under the control of vasoactive mediators released from platelets and macrophages subsequent to complement activation and C5a binding to its receptor.
39
Wang, D. H., Y. Du, H. Zhao, J. P. Granger, R. C. Speth, and D. J. Dipette. "Regulation of angiotensin type 1 receptor and its gene expression: role in renal growth." Journal of the American Society of Nephrology 8, no. 2 (February 1997): 193–98. http://dx.doi.org/10.1681/asn.v82193.
Full textAbstract:
Low sodium intake has been demonstrated to upregulate the gene expression of the predominant renal type 1 angiotensin II (Ang II) receptor (AT1), the AT1A subtype. The study presented here tests the hypothesis that the upregulation of renal AT1 mRNA induced by sodium depletion occurs conjointly with an elevation of the AT1 receptor that modulates renal growth. Seven-week-old male Wistar rats were divided into four groups and treated for 2 wk with normal sodium diet, normal sodium diet plus 3 mg/kg/day losartan, low sodium diet, or low sodium diet plus losartan. Body weight and MAP were not significantly different among the four groups. Plasma renin activity was significantly elevated by losartan treatment, low salt intake, or a combination of the two, compared with the plasma renin activity of the controls. Northern blot analysis indicated that renal AT1 mRNA levels were significantly increased-183% by losartan, 212% by low salt intake, and 227% by the combination of the two-compared with their levels in controls. Radioligand binding assays revealed that AT1 receptors were significantly increased by low salt intake but were significantly decreased by losartan treatment. Renal AT1 receptor binding in the rats subjected to sodium depletion plus losartan did not differ from that in control rats. Kidney weight, kidney weight/body weight ratio, and renal DNA and protein content were not altered by sodium depletion but were significantly lowered by losartan treatment with both normal and low sodium intake, compared with those of controls. The protein/DNA ratio was not significantly different among the four groups. Blockade of renal AT1 receptors with losartan was found to retard normal renal growth, indicating that Ang II is required for normal renal development. Low sodium intake was found to increase mRNA and expression of the renal AT1 receptor but to have no effect on renal growth, suggesting that an increase in renal mass above a normal level requires the activation of multiple factors. Blockade of the AT1 receptor by losartan was found to upregulate AT1 mRNA but to down-regulate the AT1 receptor, suggesting that AT1 receptor-mediated intracellular events are necessary to sustain functional AT1 receptor expression in the kidney.
40
Willars, Gary B., Werner Müller-Esterl, and Stefan R. Nahorski. "Receptor phosphorylation does not mediate cross talk between muscarinic M3 and bradykinin B2 receptors." American Journal of Physiology-Cell Physiology 277, no. 5 (November 1, 1999): C859—C869. http://dx.doi.org/10.1152/ajpcell.1999.277.5.c859.
Full textAbstract:
This study examined cross talk between phospholipase C-coupled muscarinic M3 and bradykinin B2 receptors coexpressed in Chinese hamster ovary (CHO) cells. Agonists of either receptor enhanced phosphoinositide signaling (which rapidly desensitized) and caused protein kinase C (PKC)-independent, homologous receptor phosphorylation. Muscarinic M3 but not bradykinin B2 receptors were also phosphorylated after phorbol ester activation of PKC. Consistent with this, muscarinic M3 receptors were phosphorylated in a PKC-dependent fashion after bradykinin B2 receptor activation, but muscarinic M3 receptor activation did not influence bradykinin B2receptor phosphorylation. Despite heterologous phosphorylation of muscarinic M3 receptors, phosphoinositide and Ca2+signaling were unaffected. In contrast, marked heterologous desensitization of bradykinin-mediated responses occurred despite no receptor phosphorylation. This desensitization was associated with a sustained component of muscarinic receptor-mediated signaling, whereas bradykinin's inability to influence muscarinic receptor-mediated responses was associated with rapid and full desensitization of bradykinin responses. Thus the mechanism of functional cross talk most likely involves depletion of a shared signaling component. These data demonstrate that receptor phosphorylation is not a prerequisite for heterologous desensitization and that such desensitization is not obligatory after heterologous receptor phosphorylation.
41
Ma, Xiaojie, Angelina Schwarz, Sonia Zambrano Sevilla, Anna Levin, Kjell Hultenby, Annika Wernerson, Mark Lal, and Jaakko Patrakka. "Depletion of Gprc5a Promotes Development of Diabetic Nephropathy." Journal of the American Society of Nephrology 29, no. 6 (April 10, 2018): 1679–89. http://dx.doi.org/10.1681/asn.2017101135.
Full textAbstract:
Background Renal glomeruli are the primary target of injury in diabetic nephropathy (DN), and the glomerular podocyte has a key role in disease progression.Methods To identify potential novel therapeutic targets for DN, we performed high-throughput molecular profiling of G protein–coupled receptors (GPCRs) using human glomeruli.Results We identified an orphan GPCR, Gprc5a, as a highly podocyte-specific gene, the expression of which was significantly downregulated in glomeruli of patients with DN compared with those without DN. Inactivation of Gprc5a in mice resulted in thickening of the glomerular basement membrane and activation of mesangial cells, which are two hallmark features of DN in humans. Compared with wild-type mice, Gprc5a-deficient animals demonstrated increased albuminuria and more severe histologic changes after induction of diabetes with streptozotocin. Mechanistically, Gprc5a modulated TGF-β signaling and activation of the EGF receptor in cultured podocytes.Conclusions Gprc5a has an important role in the pathogenesis of DN, and further study of the podocyte-specific signaling activity of this protein is warranted.
42
Yang, Chengfeng, Ying Liu, Mark A. Lemmon, and Marcelo G. Kazanietz. "Essential Role for Rac in Heregulin β1 Mitogenic Signaling: a Mechanism That Involves Epidermal Growth Factor Receptor and Is Independent of ErbB4." Molecular and Cellular Biology 26, no. 3 (February 1, 2006): 831–42. http://dx.doi.org/10.1128/mcb.26.3.831-842.2006.
Full textAbstract:
ABSTRACT Heregulins are a family of ligands for the ErbB3/ErbB4 receptors that play important roles in breast cancer cell proliferation and tumorigenesis. Limited information is available on the contribution of Rho GTPases to heregulin-mediated signaling. In breast cancer cells, heregulin β1 (HRG) causes a strong activation of Rac; however, it does so with striking differences in kinetics compared to epidermal growth factor, which signals through ErbB1 (epidermal growth factor receptor [EGFR]). Using specific ErbB receptor inhibitors and depletion of receptors by RNA interference (RNAi), we established that, surprisingly, activation of Rac by HRG is mediated not only by ErbB3 and ErbB2 but also by transactivation of EGFR, and it is independent of ErbB4. Similar receptor requirements are observed for HRG-induced actin cytoskeleton reorganization and mitogenic activity via extracellular signal-regulated kinase (ERK). HRG-induced Rac activation was phosphatidylinositol 3-kinase dependent and Src independent. Furthermore, inactivation of Rac by expression of the Rac GTPase-activating protein β2-chimerin inhibited HRG-induced ERK activation, mitogenicity, and migration in breast cancer cells. HRG mitogenic activity was also impaired by depletion of Rac1 using RNAi. Our studies established that Rac is a critical mediator of HRG mitogenic signaling in breast cancer cells and highlight additional levels of complexity for ErbB receptor coupling to downstream effectors that control aberrant proliferation and transformation.
43
Sloley, B. D., V. L. Trudeau, J. G. Dulka, and R. E. Peter. "Selective depletion of dopamine in the goldfish pituitary caused by domperidone." Canadian Journal of Physiology and Pharmacology 69, no. 6 (June 1, 1991): 776–81. http://dx.doi.org/10.1139/y91-116.
Full textAbstract:
The effects of the dopamine type-2 receptor (D-2) antagonist domperidone on pituitary and brain amine concentrations and serum gonadotropin levels in the goldfish were investigated. Domperidone caused a long-lasting, dose-dependent depletion of dopamine in the goldfish pituitary. Pituitary concentrations of 5-hydroxytryptamine (5HT) were unaffected by domperidone treatment. Concentrations of noradenaline, dopamine, and 5HT in the hypothalamus and telencephalon were also unaffected by domperidone treatment. In contrast to the goldfish, dopamine levels in both mouse pituitary and hypothalamus were unaffected by domperidone treatment. The depletion of dopamine was observed in both sexually regressed and recrudescent male and female fish, but elevation of serum gonadotropin levels in response to domperidone treatment occurred only in sexually recrudescent fish. Treatment of sexually recrudescent fish with the D-2 antagonists pimozide, (−)-sulpiride and eticlopride and the dopamine type-1 (D-1) antagonists SKF 83566 and SCH 23390 failed to elicit a depletion of pituitary dopamine or elevation of serum gonadotropin. Treatment of sexually recrudescent fish with domperidone, α-methyl-p-tyrosine or carbidopa elicited comparable depletions of pituitary dopamine and elevations of serum gonadotropin. The results suggest that in addition to D-2 receptor antagonist activity, domperidone has some other neuropharmacological action on dopaminergic neurones in the goldfish pituitary.Key words: domperidone, dopamine, noradrenaline, 5-hydroxytryptamine, pituitary, hypothalamus, telencephalon, gonadotropin, goldfish.
44
De Young, M. B., and A. Scarpa. "ATP receptor-induced Ca2+ transients in cardiac myocytes: sources of mobilized Ca2+." American Journal of Physiology-Cell Physiology 257, no. 4 (October 1, 1989): C750—C758. http://dx.doi.org/10.1152/ajpcell.1989.257.4.c750.
Full textAbstract:
Addition of micromolar concentrations of extracellular ATP to adult rat cardiac ventricular myocytes increases cytosolic Ca2+ concentration ([Ca2+]). Experiments were performed on fura-2-loaded myocytes to determine whether the [Ca2+] rise was due to Ca2+ influx, release of Ca2+ from the sarcoplasmic reticulum (SR), or a combination of both. BAY K 8644 and nifedipine affected ATP-induced [Ca2+] transients, indicating involvement of voltage-sensitive Ca2+ channels. Addition of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) or Ca2+ channel blockers significantly reduced cytosolic [Ca2+] changes due to addition of ATP or KCl without depleting Ca2+ stores (shown by ionomycin treatment in a Ca2+-free medium), demonstrating that these responses require Ca2+ influx. Depletion of intracellular Ca2+ stores by caffeine or ryanodine also diminished cytosolic [Ca2+] responses, indicating that a portion of the increased cytosolic [Ca2+] is due to Ca2+ release from SR. Norepinephrine potentiates the ATP-Ca2+ response, and this effect was not inhibited by depletion of intracellular stores. Although the data show that there are two Ca2+ sources in the cytosolic Ca2+ response to ATP, the pattern is also consistent with the hypothesis of Ca2+-induced Ca2+ release from cardiac SR.
45
McCarron, John G., John W. Craig, Karen N. Bradley, and Thomas C. Muir. "Agonist-induced phasic and tonic responses in smooth muscle are mediated by InsP3." Journal of Cell Science 115, no. 10 (May 15, 2002): 2207–18. http://dx.doi.org/10.1242/jcs.115.10.2207.
Full textAbstract:
Many cellular functions are regulated by agonist-induced InsP3-evoked Ca2+ release from the internal store. In non-excitable cells, predominantly, the initial Ca2+release from the store by InsP3 is followed by a more sustained elevation in [Ca2+]i via store-operated Ca2+ channels as a consequence of depletion of the store. Here, in smooth muscle, we report that the initial transient increase in Ca2+, from the internal store, is followed by a sustained response also as a consequence of depletion of the store (by InsP3), but, influx occurs via voltage-dependent Ca2+ channels. Contractions were measured in pieces of whole distal colon and membrane currents and [Ca2+]i in single colonic myocytes. Carbachol evoked phasic and tonic contractions; only the latter were abolished in Ca2+-free solution. The tonic component was blocked by the voltage-dependent Ca2+ channel blocker nimodipine but not by the store-operated channel blocker SKF 96365. InsP3 receptor inhibition, with 2-APB, attenuated both the phasic and tonic components. InsP3 may regulate tonic contractions via sarcolemma Ca2+ entry. In single cells,depolarisation (to ∼-20 mV) elevated [Ca2+]i and activated spontaneous transient outward currents (STOCs). CCh suppressed STOCs, as did caffeine and InsP3. InsP3 receptor blockade by 2-APB or heparin prevented CCh suppression of STOCs; protein kinase inhibition by H-7 or PKC19-36did not. InsP3 suppressed STOCs by depleting a Ca2+ store accessed separately by the ryanodine receptor (RyR). Thus depletion of the store by RyR activators abolished the InsP3-evoked Ca2+ transient. RyR inhibition (by tetracaine) reduced only STOCs but not the InsP3transient. InsP3 contributes to both phasic and tonic contractions. In the former, muscarinic receptor-evoked InsP3 releases Ca2+ from an internal store accessed by both InsP3 and RyR. Depletion of this store by InsP3 alone suppresses STOCs, depolarises the sarcolemma and permits entry of Ca2+ to generate the tonic component. Therefore, by lowering the internal store Ca2+ content,InsP3 may generate a sustained smooth muscle contraction. These results provide a mechanism to account for phasic and tonic smooth muscle contraction following receptor activation.
46
Kojima, Akiko, Hirotoshi Kitagawa, Mariko Omatsu-Kanbe, Hiroshi Matsuura, and Shuichi Nosaka. "Sevoflurane Protects Ventricular Myocytes from Ca2+Paradox-mediated Ca2+Overload by Blocking the Activation of Transient Receptor Potential Canonical Channels." Anesthesiology 115, no. 3 (September 1, 2011): 509–22. http://dx.doi.org/10.1097/aln.0b013e31822b7901.
Full textAbstract:
Background Volatile anesthetics produce cardioprotective action by attenuating cellular Ca2+ overload. The Ca2+ paradox is an important model for studying the mechanisms associated with Ca2+ overload-mediated myocardial injury, and was recently found to be mediated by Ca2+ entry through the transient receptor potential canonical channels upon Ca2+ repletion. This study investigated the effect of sevoflurane on cellular mechanisms underlying the Ca2+ paradox. Methods The Ca2+ paradox was examined in fluo-3 or mag-fluo-4-loaded mouse ventricular myocytes using confocal laser scanning microscope, upon Ca2+ repletion after 15 min of Ca2+ depletion in the absence and presence of sevoflurane. Results The Ca2+ paradox was evoked in approximately 65% of myocytes upon Ca2+ repletion, as determined by an abrupt elevation of cytosolic Ca2+ accompanied by hypercontracture. The Ca2+ paradox was significantly suppressed by sevoflurane administered for 3 min before and during Ca2+ repletion (Post) or during Ca2+ depletion and repletion (Postlong), and Postlong was more beneficial than Post application. The sarcoplasmic reticulum Ca2+ levels gradually decreased during Ca2+ depletion, and the Ca2+ paradox was readily evoked in myocytes with reduced sarcoplasmic reticulum Ca2+ levels. Postlong but not Post application of sevoflurane prevented decrease in sarcoplasmic reticulum Ca2+ levels by blocking Ca2+ leak through ryanodine receptors. Whole cell patch-clamp recordings revealed that sevoflurane rapidly blocked thapsigargin-induced transient receptor potential canonical currents. Conclusions Sevoflurane protects ventricular myocytes from Ca2+ paradox-mediated Ca2+ overload by blocking transient receptor potential canonical channels and by preventing the decrease in sarcoplasmic reticulum Ca2+ levels, which is associated with less activation of transient receptor potential canonical channels.
47
Turnamian, S. G., and H. J. Binder. "Aldosterone and glucocorticoid receptor-specific agonists regulate ion transport in rat proximal colon." American Journal of Physiology-Gastrointestinal and Liver Physiology 258, no. 3 (March 1, 1990): G492—G498. http://dx.doi.org/10.1152/ajpgi.1990.258.3.g492.
Full textAbstract:
Dietary sodium depletion increases electroneutral Na-Cl absorption and potassium secretion in the proximal colon of the rat. Although sodium depletion results in secondary hyperaldosteronism, the stimulation of electroneutral Na-Cl absorption is not a typical mineralocorticoid-mediated event. These studies were performed to determine whether the aldosterone or glucocorticoid receptor mediates these changes in electrolyte transport. Continuous infusion of aldosterone at 70 micrograms.100 g body wt-1.day-1 for 7 days resulted in a significant increase in net Na+ and Cl- absorption (5.5 +/- 0.8 and 5.9 +/- 1.0 mueq.h-1.cm-2, respectively). A 7-day infusion of RU 28362, a glucocorticoid receptor-specific agonist, at 70 micrograms.100 g body wt-1.day-1 similarly increased net Na+ and Cl- absorption (5.4 +/- 1.3 and 4.1 +/- 0.5 mueq.h-1.cm-2, respectively). Both aldosterone and RU 28362 produced a minimal increase in Isc (0.4 +/- 0.2 and 0.8 +/- 0.2, respectively). Administration of spironolactone prevented the stimulation of Na+ absorption induced by aldosterone but not that by RU 28362, and aldosterone but not RU 28362 stimulated active potassium secretion. These studies indicate that aldosterone mediates the stimulation of both electroneutral Na-Cl absorption and K+ secretion produced by dietary sodium depletion and that both aldosterone and glucocorticoid agonists each stimulate electroneutral Na-Cl absorption as a result of interacting with the mineralocorticoid and glucocorticoid receptors, respectively.
48
Samakovli, Despina, Loukia Roka, Panagiota Konstantinia Plitsi, Georgia Drakakaki, Kosmas Haralampidis, Dimitrios J. Stravopodis, Polydefkis Hatzopoulos, and Dimitra Milioni. "BRI1 and BAK1 Canonical Distribution in Plasma Membrane Is HSP90 Dependent." Cells 11, no. 21 (October 22, 2022): 3341. http://dx.doi.org/10.3390/cells11213341.
Full textAbstract:
The activation of BRASSINOSTEROID INSENSITIVE1 (BRI1) and its association with the BRI1 ASSOCIATED RECEPTOR KINASE1 (BAK1) are key steps for the initiation of the BR signaling cascade mediating hypocotyl elongation. Heat shock protein 90 (HSP90) is crucial in the regulation of signaling processes and the activation of hormonal receptors. We report that HSP90 is required for the maintenance of the BRI1 receptor at the plasma membrane (PM) and its association with the BAK1 co-receptor during BL-ligand stimulation. HSP90 mediates BR perception and signal transduction through physical interactions with BRI1 and BAK1, while chaperone depletion resulted in lower levels of BRI1 and BAK1 receptors at the PM and affected the spatial partitioning and organization of BRI1/BAK1 heterocomplexes at the PM. The BRI1/BAK1 interaction relies on the HSP90-dependent activation of the kinase domain of BRI1 which leads to the confinement of the spatial dynamics of the membrane resident BRI1 and the attenuation of the downstream signaling. This is evident by the impaired activation and transcriptional activity of BRI1 EMS SUPPRESSOR 1 (BES1) upon HSP90 depletion. Our findings provide conclusive evidence that further expands the commitment of HSP90 in BR signaling through the HSP90-mediated activation of BRI1 in the control of the BR signaling cascade in plants.
49
Liu, Lan, Rachel Santora, Jaladanki N. Rao, Xin Guo, Tongtong Zou, Huifang M. Zhang, Douglas J. Turner, and Jian-Ying Wang. "Activation of TGF-β-Smad signaling pathway following polyamine depletion in intestinal epithelial cells." American Journal of Physiology-Gastrointestinal and Liver Physiology 285, no. 5 (November 2003): G1056—G1067. http://dx.doi.org/10.1152/ajpgi.00151.2003.
Full textAbstract:
Smad proteins are transcription activators that are critical for transmitting transforming growth factor-β (TGF-β) superfamily signals from the cell surface receptors to the nucleus. Our previous studies have shown that cellular polyamines are essential for normal intestinal mucosal growth and that a decreased level of polyamines inhibits intestinal epithelial cell proliferation, at least partially, by increasing expression of TGF-β/TGF-β receptors. The current study went further to determine the possibility that Smads are the downstream intracellular effectors of activated TGF-β/TGF-β receptor signaling following polyamine depletion. Studies were conducted in IEC-6 cells derived from rat small intestinal crypts. Depletion of cellular polyamines by α-difluoromethylornithine (DFMO) increased basal levels of Smad3 and Smad4 proteins, induced their nuclear translocation, and stimulated Smad sequence-specific DNA-binding activity. Polyamine depletion-induced Smads were also associated with a significant increase in transcription activation as measured by luciferase reporter gene activity of Smad-dependent promoters. Inhibition of Smads by a dominant-negative mutant Smad4 in the DFMO-treated cells prevented the increased Smad transcription activation. Polyamine-deficient cells highly expressed TGF-β and were growth-arrested at the G1 phase. Inhibition of TGF-β by treatment with either immunoneutralizing anti-TGF-β antibody or TGF-β antisense oligodeoxyribonucleotides not only blocked the induction of Smad activity but also decreased the Smad-mediated transcriptional activation in polyamine-depleted cells. These findings suggest that Smads are involved in the downstream cellular processes mediated by cellular polyamines and that increased TGF-β/TGF-β receptor signaling following polyamine depletion activates Smads, thus resulting in the stimulation of Smad target gene expression.
50
Chang, W. J., K. G. Rothberg, B. A. Kamen, and R. G. Anderson. "Lowering the cholesterol content of MA104 cells inhibits receptor-mediated transport of folate." Journal of Cell Biology 118, no. 1 (July 1, 1992): 63–69. http://dx.doi.org/10.1083/jcb.118.1.63.
Full textAbstract:
The folate receptor is clustered on the surface of MA104 cells in association with caveolae. This relationship is thought to be essential for the proper internalization and recycling of the receptor during the delivery of 5-methyltetrahydrofolate to the cytoplasm of folate-depleted cells. Both the clustered organization of the receptor and the integrity of caveolae are disrupted when cells are deprived of cholesterol. We now show that cholesterol depletion of MA104 cells markedly reduces the rate of 5-methyltetrahydrofolate internalization and causes a 70% decline in the number of receptors present in the internal, recycling compartment. This effect is consistent with morphologic data showing that cholesterol-depleted MA104 cells have a reduced number of caveolae as well as fewer receptors per caveolae.