Academic literature on the topic 'AHL Receptor Binding'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'AHL Receptor Binding.'
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.
Journal articles on the topic "AHL Receptor Binding"
1
Cui, Yaya, Asita Chatterjee, Hiroaki Hasegawa, and Arun K. Chatterjee. "Erwinia carotovora Subspecies Produce Duplicate Variants of ExpR, LuxR Homologs That Activate rsmA Transcription but Differ in Their Interactions with N-Acylhomoserine Lactone Signals." Journal of Bacteriology 188, no. 13 (July 1, 2006): 4715–26. http://dx.doi.org/10.1128/jb.00351-06.
Full textAbstract:
ABSTRACT The N-acylhomoserine lactone (AHL) signaling system comprises a producing system that includes acylhomoserine synthase (AhlI, a LuxI homolog) and a receptor, generally a LuxR homolog. AHL controls exoprotein production in Erwinia carotovora and consequently the virulence for plants. In previous studies we showed that ExpR, a LuxR homolog, is an AHL receptor and that it activates transcription of rsmA, the gene encoding an RNA binding protein which is a global negative regulator of exoproteins and secondary metabolites. An unusual finding was that the transcriptional activity of ExpR was neutralized by AHL. We subsequently determined that the genomes of most strains of E. carotovora subspecies tested possess two copies of the expR gene: expR1, which was previously studied, and expR2, which was the focus of this study. Comparative analysis of the two ExpR variants of E. carotovora subsp. carotovora showed that while both variants activated rsmA transcription, there were significant differences in the patterns of their AHL interactions, the rsmA sequences to which they bound, and their relative efficiencies of activation of rsmA transcription. An ExpR2− mutant produced high levels of exoproteins and reduced levels of RsmA in the absence of AHL. This contrasts with the almost complete inhibition of exoprotein production and the high levels of RsmA production in an AhlI− mutant that was ExpR1−. Our results suggest that ExpR2 activity is responsible for regulating exoprotein production primarily by modulating the levels of an RNA binding protein.
2
Rajamani, Sathish, Wolfgang D. Bauer, Jayne B. Robinson, John M. Farrow, Everett C. Pesci, Max Teplitski, Mengsheng Gao, Richard T. Sayre, and Donald A. Phillips. "The Vitamin Riboflavin and Its Derivative Lumichrome Activate the LasR Bacterial Quorum-Sensing Receptor." Molecular Plant-Microbe Interactions® 21, no. 9 (September 2008): 1184–92. http://dx.doi.org/10.1094/mpmi-21-9-1184.
Full textAbstract:
Many bacteria use quorum sensing (QS) as an intercellular signaling mechanism to regulate gene expression in local populations. Plant and algal hosts, in turn, secrete compounds that mimic bacterial QS signals, allowing these hosts to manipulate QS-regulated gene expression in bacteria. Lumichrome, a derivative of the vitamin riboflavin, was purified and chemically identified from culture filtrates of the alga Chlamydomonas as a QS signal-mimic compound capable of stimulating the Pseudomonas aeruginosa LasR QS receptor. LasR normally recognizes the N-acyl homoserine lactone (AHL) signal, N-3-oxo-dodecanoyl homoserine lactone. Authentic lumichrome and riboflavin stimulated the LasR receptor in bioassays and lumichrome activated LasR in gel shift experiments. Amino acid substitutions in LasR residues required for AHL binding altered responses to both AHLs and lumichrome or riboflavin. These results and docking studies indicate that the AHL binding pocket of LasR recognizes both AHLs and the structurally dissimilar lumichrome or riboflavin. Bacteria, plants, and algae commonly secrete riboflavin or lumichrome, raising the possibility that these compounds could serve as either QS signals or as interkingdom signal mimics capable of manipulating QS in bacteria with a LasR-like receptor.
3
He, Qing, Kang Wang, Tiantian Su, Feng Wang, Lichuan Gu, and Sujuan Xu. "Crystal structure of the N-terminal domain of VqsR fromPseudomonas aeruginosaat 2.1 Å resolution." Acta Crystallographica Section F Structural Biology Communications 73, no. 7 (June 28, 2017): 431–36. http://dx.doi.org/10.1107/s2053230x17009025.
Full textAbstract:
VqsR is a quorum-sensing (QS) transcriptional regulator which controls QS systems (las,rhlandpqs) by directly downregulating the expression ofqscRinPseudomonas aeruginosa. As a member of the LuxR family of proteins, VqsR shares the common motif of a helix–turn–helix (HTH)-type DNA-binding domain at the C-terminus, while the function of its N-terminal domain remains obscure. Here, the crystal structure of the N-terminal domain of VqsR (VqsR-N; residues 1–193) was determined at a resolution of 2.1 Å. The structure is folded into a regular α–β–α sandwich topology, which is similar to the ligand-binding domain (LBD) of the LuxR-type QS receptors. Although their sequence similarity is very low, structural comparison reveals that VqsR-N has a conserved enclosed cavity which could recognize acyl-homoserine lactones (AHLs) as in other LuxR-type AHL receptors. The structure suggests that VqsR could be a potential AHL receptor.
4
Chatterjee, Asita, Yaya Cui, Hiroaki Hasegawa, Nathan Leigh, Vaishali Dixit, and Arun K. Chatterjee. "Comparative Analysis of Two Classes of Quorum-Sensing Signaling Systems That Control Production of Extracellular Proteins and Secondary Metabolites in Erwinia carotovora Subspecies." Journal of Bacteriology 187, no. 23 (December 1, 2005): 8026–38. http://dx.doi.org/10.1128/jb.187.23.8026-8038.2005.
Full textAbstract:
ABSTRACT In Erwinia carotovora subspecies, N-acyl homoserine lactone (AHL) controls the expression of various traits, including extracellular enzyme/protein production and pathogenicity. We report here that E. carotovora subspecies possess two classes of quorum-sensing signaling systems defined by the nature of the major AHL analog produced as well as structural and functional characteristics of AHL synthase (AhlI) and AHL receptor (ExpR). Class I strains represented by E. carotovora subsp. atroseptica strain Eca12 and E. carotovora subsp. carotovora strains EC153 and SCC3193 produce 3-oxo-C8-HL (N-3-oxooctanoyl-l-homoserine lactone) as the major AHL analog as well as low but detectable levels of 3-oxo-C6-HL (N-3-oxohexanoyl-l-homoserine lactone). In contrast, the members of class II (i.e., E. carotovora subsp. betavasculorum strain Ecb168 and E. carotovora subsp. carotovora strains Ecc71 and SCRI193) produce 3-oxo-C6-HL as the major analog. ExpR species of both classes activate rsmA (Rsm, repressor of secondary metabolites) transcription and bind rsmA DNA. Gel mobility shift assays with maltose-binding protein (MBP)-ExpR71 and MBP-ExpR153 fusion proteins show that both bind a 20-mer sequence present in rsmA. The two ExpR functions (i.e., expR-mediated activation of rsmA expression and ExpR binding with rsmA DNA) are inhibited by AHL. The AHL effects are remarkably specific in that expR effect of EC153, a strain belonging to class I, is counteracted by 3-oxo-C8-HL but not by 3-oxo-C6-HL. Conversely, the expR effect of Ecc71, a strain belonging to class II, is neutralized by 3-oxo-C6-HL but not by 3-oxo-C8-HL. The AHL responses correlated with expR-mediated inhibition of exoprotein and secondary metabolite production.
5
Cui, Yaya, Asita Chatterjee, Hiroaki Hasegawa, Vaishali Dixit, Nathan Leigh, and Arun K. Chatterjee. "ExpR, a LuxR Homolog of Erwinia carotovora subsp. carotovora, Activates Transcription of rsmA, Which Specifies a Global Regulatory RNA-Binding Protein." Journal of Bacteriology 187, no. 14 (July 2005): 4792–803. http://dx.doi.org/10.1128/jb.187.14.4792-4803.2005.
Full textAbstract:
ABSTRACT N-acyl homoserine lactone (AHL) is required by Erwinia carotovora subspecies for the expression of various traits, including extracellular enzyme and protein production and pathogenicity. Previous studies with E. carotovora subsp. carotovora have shown that AHL deficiency causes the production of high levels of RsmA, an RNA binding protein that functions as a global negative regulator of extracellular enzymes and proteins and secondary metabolites (Rsm, regulator of secondary metabolites). We document here that ExpR, a putative AHL receptor belonging to the LuxR family of regulators, activates RsmA production. In the absence of AHL, an ExpR+ E. carotovora subsp. carotovora strain compared to its ExpR− mutant, produces higher levels of rsmA RNA and better expresses an rsmA-lacZ transcriptional fusion. Moreover, the expression of the rsmA-lacZ fusion in Escherichia coli is much higher in the presence of expR71 (the expR gene of E. carotovora subsp. carotovora strain Ecc71) than in its absence. We also show that purified preparation of MBP-ExpR71 binds (MBP, maltose binding protein) rsmA DNA. By contrast, MBP-ExpR71 does not bind ahlI (gene for AHL synthase), pel-1 (gene for pectate lyase), or rsmB (gene for regulatory RNA that binds RsmA), nor does ExpR71 activate expression of these genes. These observations strongly suggest transcriptional activation of rsmA resulting from a direct and specific interaction between ExpR71 and the rsmA promoter. Several lines of evidence establish that N-3-oxohexanoyl-l-homoserine lactone (3-oxo-C6-HL), the major AHL analog produced by E. carotovora subsp. carotovora strain Ecc71, inhibits ExpR71-mediated activation of rsmA expression. These findings for the first time establish that the expR effect in E. carotovora subsp. carotovora is channeled via RsmA, a posttranscriptional regulator of E. carotovora subspecies, and AHL neutralizes this ExpR effect.
6
Pérez, Daniela, Maicol Ahumedo, Eileen Herrera, Catalina Vivas-Gomez, and Ricardo Vivas-Reyes. "Computational study of the interactions among structural analogues of acyl homoserine lactones (AHLs) and the Agrobacterium tumefaciens TraR binding site." F1000Research 8 (December 5, 2019): 2062. http://dx.doi.org/10.12688/f1000research.20793.1.
Full textAbstract:
Background: In the present investigation, relationships between a set of 34 analogues of N-acyl-L-homoserine lactones (AHL) and the TraR receptor were studied. The aim was to use molecular modeling as a strategy for elucidating important aspects of the mechanism of chemical signaling in the Gram-negative bacteria Agrobacterium tumefaciens, with the idea of identifying some of analogues’ structural characteristics and molecular interactions with the active site of the TraR receptor. Methods: For this purpose, we combine two molecular modeling strategies: molecular docking and three-dimensional quantitative structure-activity relationship (3D-QSAR). First, the molecular docking methodology was applied to a series of 34 analogues of AHL on the TraR transcriptional receptor to simulate the binding of analogues at the active TraR site. Secondly, 3D-QSAR models were generated to describe the correlation with the experimental biological activity using partial least squares (PLS) calculations and steric and electrostatic properties, which theoretically predict the activity of the 34 AHL analogues through statistical parameters and evaluate the prediction of the models obtained. Two alignment models were constructed; one using the optimized structures of the 34 analogues (ligand-based model) and another using the conformations of the best poses generated in the docking with TraR (receptor-based model). Results: The outcomes obtained for each protein-ligand complex showed that the Aspartic acid 70 and Threonine 129 residues are residues that participate in the formation of hydrogen bonds, while residues Alanine 38, Leucine, 40, Tyrosine 53, Glutamine 58, Tyrosine 61, Phenylalanine 62 and Valine 72 form hydrophobic interactions. These interactions are important in determining the antagonistic activity of the analogues under study against TraR. Conclusions: The ligand-based model produces better statistical results expressed in terms of several rigorous evaluation criteria, such as Q2 and R2 for the data sets than those of the receptor-based model.
7
Herrera-Arizmendi, José Luis, Everardo Curiel-Quesada, José Correa-Basurto, Martiniano Bello, and Alicia Reyes-Arellano. "Effect of New Analogs of Hexyloxy Phenyl Imidazoline on Quorum Sensing in Chromobacterium violaceum and In Silico Analysis of Ligand-Receptor Interactions." Journal of Chemistry 2020 (February 25, 2020): 1–18. http://dx.doi.org/10.1155/2020/8735190.
Full textAbstract:
The increasing common occurrence of antibiotic-resistant bacteria has become an urgent public health issue. There are currently some infections without any effective treatment, which require new therapeutic strategies. An attractive alternative is the design of compounds capable of disrupting bacterial communication known as quorum sensing (QS). In Gram-negative bacteria, such communication is regulated by acyl-homoserine lactones (AHLs). Triggering of QS after bacteria have reached a high cell density allows them to proliferate before expressing virulence factors. Our group previously reported that hexyloxy phenylimidazoline (9) demonstrated 71% inhibitory activity of QS at 100 μM (IC50 = 90.9 μM) in Chromobacterium violaceum, a Gram-negative bacterium. The aim of the present study was to take 9 as a lead compound to design and synthesize three 2-imidazolines (13–15) and three 2-oxazolines (16–18), to be evaluated as quorum-sensing inhibitors on C. violaceum CV026. We were looking for compounds with a higher affinity towards the Cvi receptor of this bacterium and the ability to inhibit QS. The binding mode of the test compounds on the Cvi receptor was explored with docking studies and molecular dynamics. It was found that 8-pentyloxyphenyl-2-imidazoline (13) reduced the production of violacein (IC50 = 56.38 μM) without affecting bacterial growth, suggesting inhibition of quorum sensing. Indeed, compound 13 is apparently one of the best QS inhibitors known to date. Molecular docking revealed the affinity of compound 13 for the orthosteric site of N-hexanoyl homoserine lactone (C6-AHL) on the CviR protein. Ten amino acid residues in the active binding site of C6-AHL in the Cvi receptor interacted with 13, and 7 of these are the same as those interacting with AHL. Contrarily, 8-octyloxyphenyl-2-imidazoline (14), 8-decyloxyphenyl-2-imidazoline (15), and 9-decyloxyphenyl-2-oxazoline (18) bound only to an allosteric site and thus did not compete with C6-AHL for the orthosteric site.
8
Deryabin, Dmitry, Anna Galadzhieva, Dianna Kosyan, and Galimjan Duskaev. "Plant-Derived Inhibitors of AHL-Mediated Quorum Sensing in Bacteria: Modes of Action." International Journal of Molecular Sciences 20, no. 22 (November 8, 2019): 5588. http://dx.doi.org/10.3390/ijms20225588.
Full textAbstract:
Numerous gram-negative phytopathogenic and zoopathogenic bacteria utilise acylated homoserine lactone (AHL) in communication systems, referred to as quorum sensing (QS), for induction of virulence factors and biofilm development. This phenomenon positions AHL-mediated QS as an attractive target for anti-infective therapy. This review focused on the most significant groups of plant-derived QS inhibitors and well-studied individual compounds for which in silico, in vitro and in vivo studies provide substantial knowledge about their modes of anti-QS activity. The current data about sulfur-containing compounds, monoterpenes and monoterpenoids, phenylpropanoids, benzoic acid derivatives, diarylheptanoids, coumarins, flavonoids and tannins were summarized; their plant sources, anti-QS effects and bioactivity mechanisms have also been summarized and discussed. Three variants of plant-derived molecules anti-QS strategies are proposed: (i) specific, via binding with LuxI-type AHL synthases and/or LuxR-type AHL receptor proteins, which have been shown for terpenes (carvacrol and l-carvone), phenylpropanoids (cinnamaldehyde and eugenol), flavonoid quercetin and ellagitannins; (ii) non-specific, by affecting the QS-related intracellular regulatory pathways by lowering regulatory small RNA expression (sulphur-containing compounds ajoene and iberin) or c-di-GMP metabolism reduction (coumarin); and (iii) indirect, via alteration of metabolic pathways involved in QS-dependent processes (vanillic acid and curcumin).
9
Gamage, Akshamal Mihiranga, Guanghou Shui, Markus R. Wenk, and Kim Lee Chua. "N-Octanoylhomoserine lactone signalling mediated by the BpsI–BpsR quorum sensing system plays a major role in biofilm formation of Burkholderia pseudomallei." Microbiology 157, no. 4 (April 1, 2011): 1176–86. http://dx.doi.org/10.1099/mic.0.046540-0.
Full textAbstract:
The genome of Burkholderia pseudomallei encodes three acylhomoserine lactone (AHL) quorum sensing systems, each comprising an AHL synthase and a signal receptor/regulator. The BpsI–BpsR system produces N-octanoylhomoserine lactone (C8HL) and is positively auto-regulated by its AHL product. The products of the remaining two systems have not been identified. In this study, tandem MS was used to identify and quantify the AHL species produced by three clinical B. pseudomallei isolates – KHW, K96243 and H11 – three isogenic KHW mutants that each contain a null mutation in an AHL synthase gene, and recombinant Escherichia coli heterologously expressing each of the three B. pseudomallei AHL synthase genes. BpsI synthesized predominantly C8HL, which accounted for more than 95 % of the extracellular AHLs produced in stationary-phase KHW cultures. The major products of BpsI2 and BpsI3 were N-(3-hydroxy-octanoyl)homoserine lactone (OHC8HL) and N-(3-hydroxy-decanoyl)homoserine lactone, respectively, and their corresponding transcriptional regulators, BpsR2 and BpsR3, were capable of driving reporter gene expression in the presence of these cognate lactones. Formation of biofilm by B. pseudomallei KHW was severely impaired in mutants lacking either BpsI or BpsR but could be restored to near wild-type levels by exogenous C8HL. BpsI2 was not required, and BpsI3 was partially required for biofilm formation. Unlike the bpsI mutant, biofilm formation in the bpsI3 mutant could not be restored to wild-type levels in the presence of OHC8HL, the product of BpsI3. C8HL and OHC8HL had opposite effects on biofilm formation; exogenous C8HL enhanced biofilm formation in both the bpsI3 mutant and wild-type KHW while exogenous OHC8HL suppressed the formation of biofilm in the same strains. We propose that exogenous OHC8HL antagonizes biofilm formation in B. pseudomallei, possibly by competing with endogenous C8HL for binding to BpsR.
10
Koch, B., T. Liljefors, T. Persson, J. Nielsen, S. Kjelleberg, and M. Givskov. "The LuxR receptor: the sites of interaction with quorum-sensing signals and inhibitors." Microbiology 151, no. 11 (November 1, 2005): 3589–602. http://dx.doi.org/10.1099/mic.0.27954-0.
Full textAbstract:
The function of LuxR homologues as quorum sensors is mediated by the binding of N-acyl-l-homoserine lactone (AHL) signal molecules to the N-terminal receptor site of the proteins. In this study, site-directed mutagenesis was carried out of the amino acid residues comprising the receptor site of LuxR from Vibrio fischeri, and the ability of the L42A, L42S, Y62F, W66F, D79N, W94D, V109D, V109T and M135A LuxR mutant proteins to activate green fluorescent protein expression from a PluxI promoter was measured. X-ray crystallographic studies of the LuxR homologue TraR indicated that residues Y53 and W57 form hydrogen bonds to the 1-carbonyl group and the ring carbonyl group, respectively, of the cognate AHL signal. Based on the activity and signal specificity of the LuxR mutant proteins, and on molecular modelling, a model is suggested in which Y62 (corresponding to Y53 in TraR) forms a hydrogen bond with the ring carbonyl group rather than the 1-carbonyl group, while W66 (corresponding to W57 in TraR) forms a hydrogen bond to the 1-carbonyl group. This flips the position of the acyl side chain in the LuxR/signal molecule complex compared to the TraR/signal molecule complex. Halogenated furanones from the marine alga Delisea pulchra and the synthetic signal analogue N-(sulfanylacetyl)-l-homoserine lactone can block quorum sensing. The LuxR mutant proteins were insensitive to inhibition by N-(propylsulfanylacetyl)-l-homoserine lactone. In contrast, the mutations had only a minor effect on the sensitivity of the proteins to halogenated furanones, and the data strongly suggest that these compounds do not compete in a ‘classic’ way with N-3-oxohexanoyl-l-homoserine lactone for the binding site. Based on modelling and experimental data it is suggested that these compounds bind in a non-agonist fashion.
Dissertations / Theses on the topic "AHL Receptor Binding"
1
Goh, Wai Kean Chemistry Faculty of Science UNSW. "Novel antagonists of bacterial signaling pathways." Publisher:University of New South Wales. Chemistry, 2008. http://handle.unsw.edu.au/1959.4/41458.
Full textAbstract:
Traditional bacterial disease therapies utilize compounds that ultimately kill the target bacteria but it exerts a strong selective pressure on the bacteria to develop multi-drug resistance mutants. The increasing occurrence of resistance in common pathogens has highlighted the need to identify new anti-microbials that target the control of bacterial pathogenicity in a non-extermination manner to reduce the incidence of bacteria resistance. One new strategy exploits the discrete signaling molecules that regulate the various bacterial signaling pathways, which are responsible for the expression of pathogenicity traits. Halogenated furanones (fimbrolides) from the marine red alga, Delisea pulchra have been shown to interfere with the key signaling pathway present in Gram-negative bacteria by competitively displacing the cognate signaling molecule from the transcription protein. This project focused on the design and synthesis of 1,5-dihydropyrrol-2-ones, a new class of fimbrolide derivatives capable of displaying strong antagonistic properties of the fimbrolides. Primary synthetic methodologies examined include the halolactamization of allenamides and the direct lactone-lactam transformation. No doubt, both methodologies yielded the lactam ring, the former failed to introduce the crucial C-5 bromomethylene group essential for bioactivity. A facile high yielding two-step lactone-lactam transformation method was developed and using this method, a wide range of substituted 5-bromomethyl- and 5-dibromomethylene-1,5-dihydropyrrol-2-ones were synthesized. Furthermore, a new class of tricyclic crown-ether type compounds with no literature precedent were discovered. To vary the diversity of the compounds, a related class of compounds, 5,6-dihydroindol-2-ones, were examined. A general versatile method for the synthesis of 7-substituted 5,6-dihydroindol-2-ones was developed. The synthetic strategy proceeds via the established Suzuki-Miyaura cross-coupling reaction of halogenated dihydroindol-2-ones with arylboronic acids/esters. The Suzuki methodology was found to be reliable in furnishing a wide range of 7-substituted products in high yields. A preliminary molecular modeling approach was used to assist in the design of new anti-microbials via the ligand-docking analyses of the TraR and LasR protein. A positive correlation was observed between the docking scores and biological activity and the methodology was further developed into an initial screening tool to filter potential active and non-active compounds. The newly synthesized compounds were analysed for their efficacy in reducing the expression of the Green Fluorescent Protein (GFP) in the presence of natural AHL signaling molecules in an AHL-monitor strain, indicative of the inhibition of bacterial phenotype expression. The dihydropyrrol-2-one class of compounds showed significant biological activity and this highlighted their potential for further development.
2
Williams, Stanley J. "Inhibition of Aryl Hydrocarbon Receptor (AhR) Activity Decreases ABCG2 Expression and Activity." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2018. http://digitalcommons.auctr.edu/cauetds/122.
Full textAbstract:
The androgen receptor’s (AR) resurgence following treatment leads to castration resistant prostate cancer (CRPC). Studies show that the aryl hydrocarbon receptor (AhR) regulates AR signaling, is constitutively active, and enhances AR signaling in CRPC. AhR has ligands with carcinogenic properties and interacts with phytochemicals with anti-tumorigenic properties. Curcumin inhibits AhR activity and multidrug transporter ABCG2 activity, which mediates substrates out of the cell. Elevated ABCG2 expression causes resistance to anticancer drugs. AhR transcriptionally activates ABCG2 and our hypothesis is that inhibition of AhR activity by curcumin will decrease ABCG2 expression and activity in CRPC cells. C4-2 cells were treated with increasing concentrations of curcumin (0, 10, 25, 50µM) and CH223191 (50µM). Results show that curcumin decreases AhR, CYP1B1 and ABCG2 gene expression. Higher concentrations of curcumin diminish AhR and ABCG2 protein expression, ABCG2 activity, and cell proliferation. These results will help reveal a role for AhR in drug resistance.
3
Öberg, Camilla. "The life and death of the notch intracellular domain /." Stockholm, 2003. http://diss.kib.ki.se/2003/91-7349-464-X/.
Full text
4
Salisbury, Richard L. Jr. "TCDD represses 3'IghRR activation through an AhR-dependent shift in the NF-κB/Rel protein complexes binding to κB motifs within the hs1,2 and hs4 enhancers." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1401136335.
Full text
5
Xie, Jinghang. "Study of the aryl hydrocarbon receptor as a target for rational drug design." Scholarly Commons, 2014. https://scholarlycommons.pacific.edu/uop_etds/140.
Full textAbstract:
The aryl hydrocarbon receptor (AhR) heterodimerizes with the aryl hydrocarbon receptor nuclear translocator (Arnt) for transcriptional regulation. We generated three N-terminal deletion constructs of the human AhR of 12-24 KDa in size—namely D1 (aa 84-295), D2 (aa 84-192) and D3 (aa 191-295)—to suppress the Arnt function. We observed that all three constructs interact with the human Arnt with similar affinities. D2, which contains part of the AhR PAS-A domain and interacts with the PAS-A domain of Arnt, inhibits the formation of the AhR gel shift complex. D2 suppresses the 3-methylcholanthrene-induced, dioxin response element (DRE)-driven luciferase activity in Hep3B cells and exogenous Arnt reverses this D2 suppression. D2 suppresses the induction of CYP1A1 at both the message and protein levels in Hep3B cells; however, the CYP1B1 induction is not affected. D2 suppresses the recruitment of Arnt to the cyp1a1 promoter but not to the cyp1b1 promoter, partly because the AhR/Arnt heterodimer binds better to the cyp1b1 DRE than to the cyp1a1 DRE. Interestingly, D2 has no effect on the cobalt chloride-induced, hypoxia inducible factor-1 (HIF-1)-dependent expression of vegf, aldolase c, and ldh-a messages. Our data reveal that the flanking sequences of the DRE contribute to the binding affinity of the AhR/Arnt heterodimer to its endogenous enhancers and the function of AhR and HIF-1 can be differentially suppressed by the D2 inhibitory molecule. In chapter 2, a Pichia Pastoris expression system was constructed expressing codon optimized human full length AhR. This codon optimization is necessary for overexpression of huAhR. RT-PCR data showed that the codon optimized mRNA was more stably expressed than wild types. Overexpressed huAhR protein was degraded by proteinase when using a regular P. Pastoris strain yJC100 whereas the proteinase deficient ySMD1163 maintained a much higher level of huAhR. P. Pastoris expressed huAhR was natively purified and analyzed. Coimmunopricipitation assay shows its interaction with endogenous Arnt. A ligand-dependent gel shift was also observed. In addition, we performed an in vitro coprecipitation assay to study its binding to endogenous cyp1b1 DREs. The result shows that the DRE3, known as a critical DRE for cyp1b1 transcriptional activity, has the highest binding affinity to AhR/Arnt complex. Taking together, we constructed a novel P. Pastoris expression system to overexpress human full length AhR. Purified huAhR is a good reagent for studing its ligand and DNA binding. In chapter 3, an adeno-associated virus (AAV) expression system was constructed to express an AhR deletion contruct CΔ553 (aa1-295) for tumor injection. Western blot shows the expression of CΔ553 (aa1-295) in hela cells infected by AAV-553, but the low yield of AAV-553 limited its application on tumor treatment. Possible solutions were discussed for future work.
6
Sikri, Vishal. "Characterization of all-trans-retinol binding to the retinoic acid receptor." 2000. http://catalog.hathitrust.org/api/volumes/oclc/44638602.html.
Full textAbstract:
Thesis (M.S.)--University of Wisconsin--Madison, 2000.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 79-88).
7
Chen, Grace Yi-Ying. "Functional Analysis of Adapter Protein c-Abl Src Homology 3 Domain-binding Protein 2." Thesis, 2009. http://hdl.handle.net/1807/17740.
Full textAbstract:
3BP2 is a pleckstrin homology (PH) domain- and Src homology 2 (SH2) domain-containing adapter protein that has been linked through genetic evidence to a rare human disease called cherubism 146. 3BP2 was originally cloned in a screen to identify c-Abl SH3 binding proteins 23,24. In overexpression studies, 3BP2 has been implicated as a positive regulatory adapter molecule coupled to immunoreceptor on T cells 67,69,70, B cells 68, NK cells 71-73 and mast cells 74,75. It was also evident that 3BP2 forms complexes with a number of signaling molecules, such as Zap-70, LAT, phospholipase C-γ1 (PLC-γ1), Grb2, Cbl, and Fyn in Jurkat cells 67 and Vav1, Vav2, PLC-γ, and Syk in Daudi B cells 68.
Despite the growing body of biochemical data to support the importance of 3BP2 in cells of the hematopoietic lineage, a clear picture of the biological function of 3BP2 has yet to emerge. To elucidate the in vivo function of 3BP2, our laboratory has generated 3BP2 gene-deficient mice through homologous recombination 452. The 3BP2-deficient (3BP2-/-) mice were born at the expected Mendelian frequency and were fertile and viable.
3BP2-/- mice accumulate splenic marginal-zone (MZ) B cells, possess a reduced frequency of peritoneal B-1 B cells, and have a diminished thymus-independent type 2 (TI-2) antigen response. 3BP2-/- B cells demonstrate diminished proliferation and cell survival following cross-linking of the B-cell receptor (BCR). Following BCR ligation, 3BP2 might be recruited to BCR complex through its inducible interaction with BCR costimulatory molecule CD19. In the absence of 3BP2, the activation of BCR downstream effectors such as MAPK Erk1/2, JNK, and c-Abl is normal; however, 3BP2 deficiency leads to defects in Syk phosphorylation and calcium flux.
In addition to defects in peripheral B cell activities, 3BP2 deficiency contributes to defects in neutrophil activities. In response to the chemotactic peptide, fMLF, 3BP2-/- neutrophils fail to establish directional migration in vitro. There is a defect in the accumulation of filamentous actin at the leading edge of migrating 3BP2-/- neutrophils which might be responsible for the random movement of these cells under shallow gradient of fMLF. In vivo, there is a delay in the recruitment of circulating neutrophils to the site of chemically induced inflammation in 3BP2-/- mice. Compared to wildtype neutrophils, 3BP2-/- neutrophils fail to properly produce superoxide anion (O2-) following fMLF stimulation. Defects in both directional migration and superoxide production of 3BP2-/- neutrophils might contribute to the reduction in bacteria clearance and the increased mortality in 3BP2-/- mice post Listeria Monocytogenes infection.
In Chapter 1 of this thesis, I have reviewed basic structures and functions of the domain modules found in adapter proteins. In addition, I have reviewed the findings from numerous reports on the function of 3BP2 in different cell types. A discussion of the physical appearance and some of the initial characterization of 3BP2-deficient mice (3BP2-/-) we have generated in our laboratory are included in Chapter 1. The second part of Chapter 1 consists of an introduction on B cell receptor signaling pathway and B-cell development and activation. A discussion of G protein-coupled receptor-mediated neutrophil functions can also be found in Chapter 1.
Chapter 2 contains all the methods and materials used in my study.
Chapter 3 includes the characterization of peripheral B cell compartment of 3BP2-/- mice as well as the role of 3BP2 downstream of B-cell antigen receptor and in T-independent immune response.
In chapter 4, I present data from experiments designed to examine the role of 3BP2 downstream of a G protein-coupled receptor, fMLF receptor, of neutrophils. I also show the requirement of 3BP2 in the clearance of Listeria Monocytogenes.
In chapter 5, I propose two models for 3BP2 action based on the findings in B cells and neutrophils and discuss future areas for investigation.
Books on the topic "AHL Receptor Binding"
1
Ren, Ke, and Ronald Dubner. The first crystal structure of an ionotropic glutamate receptor ligand-binding core. Edited by Paul Farquhar-Smith, Pierre Beaulieu, and Sian Jagger. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198834359.003.0032.
Full textAbstract:
The known functional ionotropic glutamate receptors (iGluRs) are composed of three major subtypes: AMPA, NMDA, and kainate. In 1998, in the landmark paper discussed in this chapter, Armstrong et al. provided the first crystal structure of an iGluR-subunit ligand-binding core, the S1S2 region of the rat GluA2 ‘flop’ isoform. They solved its structure with X-ray crystallography from selenomethonine crystals. They also identified residues involved in kainate binding, analysed allosteric sites that regulate affinity and specificity of the agonist, and mapped potential subunit–subunit interaction sites. They also proposed that binding of different agonists may result in variable degrees of domain closure. This work has profound impact on the field and it has been importantly cited. Subsequently, numerous high-resolution crystal structures of ligand-binding domains of iGluRs in complex with ligands, both agonists and antagonists, have been solved.
2
Peppin, John, Joseph V. Pergolizzi, Robert B. Raffa, and Steven L. Wright, eds. The Benzodiazepines Crisis. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780197517277.001.0001.
Full textAbstract:
When properly prescribed, benzodiazepines and related “Z” drugs, are usually safe and effective. However, some patients experience lack of efficacy, severe adverse effects, and/or protracted withdrawal symptoms. Unfortunately, there is no reliable way to predict outcome prior to treatment. Use has dramatically expanded, to the point where some experts suggest a disconnect with actual medical need. With increased and longer prescribing there has been a corresponding increase in the “down-side” of these drugs. Benzodiazepines, as all drugs, produce some degree of normal physiologic tolerance and physical dependence. But for some patients withdrawal can result in a bewildering array of symptoms, that can persist for protracted time periods, difficult to understand and live with. Although there is currently no clear mechanistic explanation, some potentials include alterations of receptor number, promoters of receptor protein synthesis or degradation, absorption, distribution, metabolism, and elimination, GABAA-receptor function or subtype-distribution, or involvement of peripheral benzodiazepine binding/receptor sites. This book attempts to bring benzodiazepine use under a more rational paradigm and reduce the incidence of side-effects and drug–drug interactions (DDI). It is the first devoted to take on this responsibility. Use, overuse/misuse, side-effects, DDI, physiology, and withdrawal are reviewed by expert clinicians and basic scientists in-depth. The book challenges the medical community to take seriously the use of this class of drug and to ameliorate prescribing behavior. The case is made for limiting initiation and duration (2–4 weeks) of use, and careful, supported discontinuation. We laud and suggest increased research into this class of drug and it’s “down-side.”
3
Hamilton, Matthew Lloyd. COMT genotypes in pain responses. Edited by Paul Farquhar-Smith, Pierre Beaulieu, and Sian Jagger. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198834359.003.0080.
Full textAbstract:
The landmark study discussed in this chapter is ‘COMT val158met genotype affects μ-opioid neurotransmitter responses to a pain stressor’, published by Zubieta et al. in 2003. Catechol-O-methyl-transferase (COMT) is a key modulator of dopaminergic and noradrenergic neurotransmission. This study focused on a single nucleotide polymorphism of the COMT gene encoding the substitution of valine (val) by methionine (met) at Codon 158 (val158met), resulting in a three- to fourfold reduction in its activity. Individuals with the val/val genotype have the highest activity of COMT, val/met genotypes have intermediate activity, and met/met genotypes have the lowest activity of COMT. Using a mixture of PET imaging of the binding of μ-opioid receptors and correlation with clinical outcomes, this groundbreaking study provided evidence that confirmed their hypothesis and established the COMT val158met SNP as one of the first gene modifications with direct ramifications on human pain.
Book chapters on the topic "AHL Receptor Binding"
1
DeGroot, Danica, Guochun He, Domenico Fraccalvieri, Laura Bonati, Allesandro Pandini, and Michael S. Denison. "AHR Ligands: Promiscuity in Binding and Diversity in Response." In The AH Receptor in Biology and Toxicology, 63–79. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118140574.ch4.
Full text
2
Medvedev, A. E., V. I. Shvedov, T. M., O. A. Fedotova, E. Saederup, and R. F. Squires. "The influence of the antidepressant pirlindole and its dehydro-derivative on the activity of monoamine oxidase A and GABAA receptor binding." In MAO — The Mother of all Amine Oxidases, 337–42. Vienna: Springer Vienna, 1998. http://dx.doi.org/10.1007/978-3-7091-6499-0_36.
Full text
3
Mao, Youdong. "Structure, Dynamics and Function of the 26S Proteasome." In Subcellular Biochemistry, 1–151. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-58971-4_1.
Full textAbstract:
AbstractThe 26S proteasome is the most complex ATP-dependent protease machinery, of ~2.5 MDa mass, ubiquitously found in all eukaryotes. It selectively degrades ubiquitin-conjugated proteins and plays fundamentally indispensable roles in regulating almost all major aspects of cellular activities. To serve as the sole terminal “processor” for myriad ubiquitylation pathways, the proteasome evolved exceptional adaptability in dynamically organizing a large network of proteins, including ubiquitin receptors, shuttle factors, deubiquitinases, AAA-ATPase unfoldases, and ubiquitin ligases, to enable substrate selectivity and processing efficiency and to achieve regulation precision of a vast diversity of substrates. The inner working of the 26S proteasome is among the most sophisticated, enigmatic mechanisms of enzyme machinery in eukaryotic cells. Recent breakthroughs in three-dimensional atomic-level visualization of the 26S proteasome dynamics during polyubiquitylated substrate degradation elucidated an extensively detailed picture of its functional mechanisms, owing to progressive methodological advances associated with cryogenic electron microscopy (cryo-EM). Multiple sites of ubiquitin binding in the proteasome revealed a canonical mode of ubiquitin-dependent substrate engagement. The proteasome conformation in the act of substrate deubiquitylation provided insights into how the deubiquitylating activity of RPN11 is enhanced in the holoenzyme and is coupled to substrate translocation. Intriguingly, three principal modes of coordinated ATP hydrolysis in the heterohexameric AAA-ATPase motor were discovered to regulate intermediate functional steps of the proteasome, including ubiquitin-substrate engagement, deubiquitylation, initiation of substrate translocation and processive substrate degradation. The atomic dissection of the innermost working of the 26S proteasome opens up a new era in our understanding of the ubiquitin-proteasome system and has far-reaching implications in health and disease.
4
Hammes, Stephen R., and Carole R. Mendelson. "Mechanisms of Hormone Action." In Textbook of Endocrine Physiology. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199744121.003.0006.
Full textAbstract:
The capacity of a cell to respond to a particular hormone depends on the presence of cellular receptors specific for that hormone. After binding hormone, the receptor is biochemically and structurally altered, resulting in its activation; the activated receptor then mediates all of the actions of the hormone on the cell. The steroid and thyroid hormones as well as retinoids and 1,25-dihydroxyvitamin D3 diffuse freely through the lipophilic plasma membrane of the cell and interact with receptors that are primarily within the nucleus. On activation, the receptors alter the transcription of specific genes, resulting in changes in the levels of specific messenger RNAs (mRNAs), which are in turn translated into proteins. Hormones that are water soluble, such as the peptide and polypeptide hormones, catecholamines, and other neurotransmitters, as well as the relatively hydrophobic prostaglandins, interact with receptors in the plasma membrane. After hormone binding, the activated membrane receptors initiate signal transduction cascades that result in changes in enzyme activities and alterations in gene expression. In this chapter, the properties of various classes of receptors that are localized within the plasma membranes of target cells and the signal transduction mechanisms that mediate interactions with their ligands will first be addressed. This will be followed by consideration of the structural properties of the nuclear hormone receptors, the events that result in their activation, and the mechanisms whereby the activated nuclear receptors alter the expression of specific genes. Finally, a number of endocrine disorders that are caused by alterations in the number and/or function of plasma membranes and nuclear receptors will be reviewed. The function of a receptor is to recognize a particular hormone among all the molecules in the environment of the cell at a given time and, after binding the hormone, to transmit a signal that ultimately results in a biological response. Hormones are normally present in the circulation in extremely low concentrations, ranging from 10 –9 to 10 –11 M.
5
Deeb, Omar, Heidy Martínez-Pachecho, Guillermo Ramírez-Galicia, and Ramón Garduño-Juárez. "Application of Docking Methodologies in QSAR-Based Studies." In Pharmaceutical Sciences, 850–76. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-1762-7.ch033.
Full textAbstract:
The computational strategies permeate all aspects of drug discovery such as virtual screening techniques. Virtual screening can be classified into ligand based and structure based methods. The ligand based method such as Quantitative Structure Activity Relationship (QSAR) is used when a set of active ligand compounds is recognized and slight or no structural information is available for the receptors. In structure based drug design, the most widespread method is molecular docking. It is widely accepted that drug activity is obtained through the molecular binding of one ligand to receptor. In their binding conformations, the molecules exhibit geometric and chemical complementarity, both of which are essential for successful drug activity. The molecular docking approach can be used to model the interaction between a small drug molecule and a protein, which allow us to characterize the performance of small molecules in the binding site of target proteins as well as to clarify fundamental biochemical processes.
6
Deeb, Omar, Heidy Martínez-Pachecho, Guillermo Ramírez-Galicia, and Ramón Garduño-Juárez. "Application of Docking Methodologies in QSAR-Based Studies." In Advances in Medical Technologies and Clinical Practice, 29–55. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-5225-0362-0.ch002.
Full textAbstract:
The computational strategies permeate all aspects of drug discovery such as virtual screening techniques. Virtual screening can be classified into ligand based and structure based methods. The ligand based method such as Quantitative Structure Activity Relationship (QSAR) is used when a set of active ligand compounds is recognized and slight or no structural information is available for the receptors. In structure based drug design, the most widespread method is molecular docking. It is widely accepted that drug activity is obtained through the molecular binding of one ligand to receptor. In their binding conformations, the molecules exhibit geometric and chemical complementarity, both of which are essential for successful drug activity. The molecular docking approach can be used to model the interaction between a small drug molecule and a protein, which allow us to characterize the performance of small molecules in the binding site of target proteins as well as to clarify fundamental biochemical processes.
7
Etti, Imaobong, Chukwuemeka Nwafor, and Grace Essien. "Small Molecules Inhibit Extranuclear Signaling by Estrogen: A Promising Strategy to Halt Breast Cancer Progression and Metastasis." In Sex Hormones [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94052.
Full textAbstract:
The sex hormone estrogen plays critical roles in reproductive and sexual development. It regulates the expression and activity of key signaling molecules critical in various cellular signaling pathways. These signals are mediated by its binding to estrogen receptors alpha (ERα) and beta (ERβ). ERα has been shown to greatly participate in extranuclear signaling, inducing tumorogenesis and breast cancer metastasis. Small molecules from plants are reported with better selectivity toward tumorigenic cells with negligible toxicity when compared to their synthetic counterpart. The molecules used in this study were first probed for their drug-likeness and their pharmacokinetic profile was elucidated before docking them to the ligand binding domain of the human ERα followed by a post docking prime analysis. All tested molecules had good drug-like and pharmacokinetic properties when compared to about 95% of orally available drugs as predicted by qikprop. The docking results revealed a strong binding interaction with ERα, influenced mostly by the vicinal diol groups of the studied molecules. These resulted in a conformational change, inducing receptor dimerization and altering the interactions of the sex hormone with other proteins. The studied ligands are promising in strongly inhibiting the binding of estrogen to ERα, thus limiting its extranuclear signaling.
8
D. Maniero, Gregory. "Evolutionary Conservation of the Role of CD4 as a Receptor for Interleukin-16." In Interleukins - The Immune and Non-Immune Systems’ Related Cytokines. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96951.
Full textAbstract:
The interaction of CD4 with MHC class II during helper T-cell activation and effector function is required for the initiation of an adaptive immune response in all gnathostomes. CD4 is comprised of four immunoglobulin domains but most likely arose from an ancestral two-domain homolog. The distal, D1 domain of CD4 binds to non-polymorphic regions of the MHC molecule, but despite the absolute requirement for this interaction, the sequence and structure of this domain are not well conserved through phylogeny. Conversely, the proximal, D4 domain of CD4 contains the binding site of the cytokine IL-16 and is highly conserved in its amino acid structure. IL-16 is a cytokine that has been described in a wide variety of invertebrate and vertebrate species. The CD4-binding residues on IL-16 are highly conserved throughout phylogeny, allowing for promiscuous binding of IL-16 to CD4 between members of unrelated taxa. This chapter aims to present structural, and functional support for the hypothesis that the CD4 co-receptor of the TCR arose from a primordial receptor for IL-16.
9
Oldstone, Michael B. A. "Introduction to the Principles of Virology." In Viruses, Plagues, and History, 11–22. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190056780.003.0002.
Full textAbstract:
This chapter defines what a virus is, how it replicates, and how it causes diseases. Peter Medawar, a biologist awarded the Nobel Prize for Medicine and Physiology in 1960, defined viruses as a piece of nucleic acid surrounded by bad news. Viruses cannot multiply until they invade a living cell. However, viruses can enter all cellular forms of life from plants and animals to bacteria, fungi, and protozoa. As opposed to plants and animals, which are made up of cells, viruses lack cell walls and are therefore obligatory parasites that depend for replication on the cells they infect. The attachment or binding of a viral protein to a cell receptor is the first step that initiates infection of a cell. The type of cells with such receptors and/or with the ability to replicate a given virus often determines the severity of illness that a virus can cause, the distribution of areas in the body that can be affected, and the host’s potential for recovery.
10
Becker, Richard C., and Frederick A. Spencer. "Novel Platelet Antagonists." In Fibrinolytic and Antithrombotic Therapy. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195155648.003.0016.
Full textAbstract:
The development of pharmacologic agents that inhibit platelet performance could not have proceeded without a fundamental knowledge of normal biology and a clear understanding of the laws that govern cellular events in the circulatory system. The adhesion of platelets to a site of vessel wall injury is mediated by von Willebrand factor (vWF), which binds to the platelet glycoprotein (GP) Ib/IX-V complex receptor (and the GPIIb/IIIa receptor under high shear stress conditions). Monoclonal antibodies to vWF have been developed and tested in animal models, as has aurintricarboxylic acid (Strony et al., 1990), a triphenylmethyl compound that inhibits vWF binding. To date, investigation in humans has not taken place, perhaps because of concerns regarding the potential risk for hemorrhagic complications. Nevertheless, the scientific community remains interested in vWF and its platelet surface receptor as potential pharmacology-directed targets. Although the GPIIb/IIIa receptor antagonists are best known for their ability to inhibit platelet aggregation, under high shear stress conditions vWF can also bind the GPIIb/IIIa receptor, facilitating adhesion. As a result, GPIIb/IIIa antagonists may have an impact on both platelet adhesion and aggregation. As previously discussed, platelet activation is followed by a series of intracellular events that culminate in the release of calcium and substances that augment platelet aggregation and support coagulation protease binding. Thus, pharmacologic agents that inhibit initial surface receptor–mediated activation may also impair platelet aggregation. Several natural prostanoids (prostaglandin [PG] E1 and PGI2) can inhibit platelet activation and aggregation by elevating cyclic adenosine monophosphate (cAMP) levels. Although the mechanism is complex, the primary mode of inhibition is through the activation of adenylate cyclase (with a subsequent rise in cAMP concentrations), which in turn prevents calcium mobilization. The clinical application of PGE1 and PGI2 has been limited by their effect on vascular tone, producing substantial systemic hypotension (Emmons et al., 1967; Terres et al., 1989), and by extensive first-pass metabolism in the lungs (70% of the active compound is rapidly cleared) (Kleiman et al., 1994).
Conference papers on the topic "AHL Receptor Binding"
1
McGregor, J. L., and H. Boukerche. "NORMAL EXPRESSION OF THROMBOSPONDIN RECEPTOR SITES ON PLATELETS OF THREE GLANZMANN THROMBASTHENIC PATIENTS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644740.
Full textAbstract:
A well characterised anti-thrombospondin (TSP) monoclonal antibody (Mab) LYP8 was used to investigate the presence of TSP receptors on Glanzmann thrombasthenic (G.T.) platelets. LYP8 inhibited platelet aggregation induced by low concentrations of thrombin (0.05 U/ml) or collagen (0.5 ug/ml). The presence of LYP8 did not affect the number of sites and Kd of 125I-fibrinogen binding to thrombin-stimulated normal platelets. Binding of LYP8 to normal platelets was minimal in whole blood (300 IgG molecules/ olatelet), increased in citrated PRP (1187 ± 209 IgG molecules/ platelet) and washed platelets (2967 ± 1278 IgG molecules/platelet) . Thrombin stimulation of platelets, washed in the presence of 2 mM calcium, increased the number of LYP8 binding sites (14917 ± 42n IgG molecules/platelet). Addition of EDTA (5mM) to thrombin-stimulated platelets did not reduce the number of LYP8 binding sites. The number of LYP8 binding sites on thrombin-stimulated platelets of three Glanzmann thrombasthenic patients (showing an absence of the glycoprotein (GP) lib and IIIa)was similar to normals in the presence of 2 mM calcium or 5 mM EDTA. In competitive binding, Mab LYP18 directed against the GPIIb-IIIa complex did not inhibit the binding of labelled monoclonal antibody LYP8. These results strongly suggest that TSP binds to a membrane receptor different from the GPIIb-IIIa complex in the presence of calcium or EDTA. This unidentified receptor may be GPIV also known as GPIIIb (Asch, A. et al. Clin. Res. 1986, 34:450A).
2
Arita, H., and T. Nakano. "INFLUENCE OF β-LACTAM ANTIBIOTICS ON THE PLATELETS IN VITRO EFFECTS OF SOME β-LACTAM ANTIBIOTICS ON THE BIOCHEMICAL RESPONSES OF RAT PLATELETS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644814.
Full textAbstract:
The inhibitory mechanism of 3-lactam antibiotics on rat platelets were studied using carbenicil1 in (CBPC) as a representative of the antibiotics. CBPC suppressed all the thrombin-induced cellular responses including shape change, secretion, and aggregation, however, it only suppressed aggregation of ADP-induced responses. This suggests that ADP binding to its own receptor was not affected by the drug while that of thrombin was inhibited. Inhibition of thrombinbinding was confirmed using 125CQSe 0f ADP-stimulated platelets, fibrinogen binding, which has an essential role for ADP-induced primary aggregation, was significantly suppressed by CBPC. Increase of a net negative charge of the membrane surface was observed after treatment of the platelets with antibiotics, and good correlation was obtained between suppression of the platelet responses and degree of net negativecharge of the antibiotics especially on the penicillin analogues. These findings strongly suggest that the inhibition of ligand binding to their own receptors is due to the increase of the negative charge of the platelet membranes which is probably caused by the antibiotic bound to the platelet membrane
3
Jakobs, K. H., P. Gierschik, and R. Grandt. "THE ROLE OF GTP-BINDING PROTEINS EXHIBITING GTPase ACTIVITY IN PLATELET ACTIVATION." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644773.
Full textAbstract:
Activation of platelets by agonists acting via cell surface-located receptors apparently involves as an early event in transmembrane signalling an interaction of the agonist-occupied receptor with a guanine nucleotide-binding regulatory protein (G-protein). The activated G-protein, then, transduces the information to the effector molecule, being responsible for the changes in intracellular second messengers. At least two changes in intracellular signal molecules are often found to be associated with platelet activation by agonists, i.e., increases in inositol trisphosphate and diacylglycerol levels caused by activation of a polyphosphoinositide-specific phospholipase C and decrease in cyclic AMP concentration caused by inhibition of adenylate cyclase.Both actions of platelet-activating agents apparently involve G-proteins as transducing elements. Generally, the function of a G-protein in signal transduction can be measured either by its ability to regulate the activity of the effector molecule (phospholipase C or adenylate cyclase) or the binding affinity of an agonist to its specific receptor or by the abitlity of the G-protein to bind and hydrolyze GTP or one of its analogs in response to agonist-activated receptors. Some platelet-activating agonists (e.g. thrombin) can cause both adenylate cyclase inhibition and phospholipase C activation, whereas others induce either inhibition of adenylate cyclase (e.g. α2-adrenoceptor agonists) or activation of phospholipase C (e.g. stable endoperoxide analogs) . It is not yet known whether the simultaneous activation of two signal transduction systems is due to activation of two separate G-proteins by one receptor, to two distinct receptors activating each a distinct G-protein or to activation of two effector molecules by one G-protein.For some of the G-proteins, rather specific compounds are available causing inactivation of their function. In comparison to Gs, the stimulatory G-protein of the adenylate cyclase system, the adenylate cyclase inhibitory Gi-protein is rather specifically inactivated by ADP-ribosylation of its a-subunit by pertussis toxin, “unfortunately” not acting in intact platelets, and by SH-group reactive agents such as N-ethylmaleimide and diamide, apparently also affecting the Giα-subunit. Both of these treatments completely block α2-adrenoceptor-induced GTPase stimulation and adenylate cyclase inhibition and also thrombin-induced inhibition of adenylate cyclase. In order to know whether the G-protein coupling receptors to phospholipase C is similar to or different from the Gi-protein, high affinity GTPase stimulation by agents known to activate phospholipase C was evaluated in platelet membranes. The data obtained indicated that GTPase stimulation by agents causing both adenylate cyclase inhibition and phospholipase C activation is reduced, but only partially, by the above mentioned Gi-inactivating agents, while stimulation of GTPase by agents stimulating only phospholipase C is not affected by these treatments. These data suggested that the G-protein regulating phospholipase C activity in platelet membranes is different from the Gi-protein and may also not be a substrate for pertussis toxin. Measuring thrombin stimulation of inositol phosphate and diacylglycerol formation in saponin-permeabilized platelets, apparently contradictory data were reported after pertussis toxin treatment, being without effect or causing even an increase in thrombin stimulation of inositol phosphate formation (Lapetina: BBA 884, 219, 1986) or being inhibitory to thrombin stimulation of diacylglycerol formation (Brass et al.: JBC 261, 16838, 1986). These data indicate that the nature of the phospholipase C-related G-protein(s) is not yet defined and that their elucidation requires more specific tools as well as purification and reconstitution experiments. Preliminary data suggest that some antibiotics may serve as useful tools to characterize the phospho-lipase-related G-proteins. The possible role of G-protein phosphorylation by intracellular signal molecule-activated protein kinases in attenuation of signal transduction in platelets will be discussed.
4
De Marco, L., M. Mazzucato, M. G. Del Ben, U. Budde, A. B. Federici, A. Girolami, and Z. M. Ruggeri. "THE PLATELET AGGREGATING PROPERTIES OF TYPE IIB VON WILLEBRAND FACTOR (vWF): THE ROLE OF PLATELET ACTIVATION, FIBRINOGEN AND TWO DISTINCT MEMBRANE RECEPTORS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644643.
Full textAbstract:
Three preparations of purified von Willebrand factor (vWF), obtained from unrelated patients affected by type IIB von Willebrand disease, were found to have normal sialic acid content (between 129-190 nmoles/mg of vWF, as compared to 158 ± 17 nmoles/mg in four normal preparations) and to induce platelet aggregation in the presence of physiologic levels of divalent cations and without addition of ristocetin. A monoclonal antibody that blocks the vWF binding domain of the platelet glycoprotein (GP) Ib caused complete inhibition of IIB vWF-induced aggregation. On the contrary, a monoclonal antibody that blocks the receptor for adhesive proteins on the platelet GPIIb/IIIa complex failed to inhibit the initial response of platelets to high concentration of IIB vWF Moreover, IIB vWF caused agglutination of formalin-fixed platelets that was blocked only by the anti-GPIb antibody, suggesting that the binding of vWF to GPIb, even in the absence of ristocetin, results in platelet-platelet interaction that is followed by exposure of the GPIIb/IIIa receptors for adhesive proteins. Endogenous ADP, normally active platelet metabolism and fibrinogen binding to GPIIb/IIIa were necessary for maximal and irreversible platelet aggregation. In the absence of fibrinogen, however, aggregation was mediated by vWF binding to GPIIb/IIIa. A 52/48 kDa tryptic fragment containing the GPIb binding domain of normal vWF completely blocked the aggregation induced by all three IIB vWF preparations. The present study defines in detail the mechanisms involved in IIB vWF-induced platelet aggregation. Moreover, it establishes that the GPIb binding domain of normal and IIB vWF are closely related and that desialylation is not required for the direct interaction of IIB vWF with GPIb.
5
Pfliegler, G., J. Arnout, J. Kienast, K. Wittevrongel, and J. Vermylen. "INSULIN RECEPTORS ARE NOT COUPLED TO THE PHOSPHOINOSITIDE OR ADENYLCYCLASE MESSENGER SYSTEMS IN HUMAN PLATELETS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644523.
Full textAbstract:
Insulin receptors have been found not only on its “target Cells” but also on several other cell-types, including human platelets. From studies on adipocytes and liver cells it seems that they are coupled both to the adenylate cyclase-cyclic AMP and the polyphosphoinositide messenger systems. Circulating blood cells might faithfully reflect the insulin receptor state of target organ tissues. Impaired platelet function has an important role in the pathogenesis of vascular and thrombotic complications in diabetes mellitus, and insulin seems to act directly on platelets. A reduction in the number and binding capacity of platelet insulin receptors in diabetic patients (Udvardy et al. 1986) suggested a (patho)physiological role for these receptors. In our studies, insulin (1 × 10-9 - 1 × 10-6 M) did not affect basal platelet cyclic AMP levels, as measured following incorporation of [3H] adenine. Insulin did not prevent PGI2 (25-75 nmol/L) induced cyclic AMP formation in platelets. Insulin did not modify the basal levels of inositol phosphate (IP), IP2 or IP3 in platelets, as measured following incorporation of [3H] inositol. Insulin did not affect formation of IP, IP2 or IP3 by thrombin. No changes in cytosolic free Ca2+ (Quin 2 method) were detected in the presence of insulin. Sodium nitroprusside on the other hand, which is known to mimic several effects of insulin on adipocytes, inhibited IP formation induced by threshold concentrations of thrombin.On the basis of our results the insulin receptors in human platelets seem to be “non-functional” insofar as their occupancy is not accompanied by the stimulation or inhibition of phospho-inositide breakdown or cyclic AMP formation. Similarly, “silent” muscarinic-cholinergic receptors have recently been reported in human erythrocytes (Sehar et al. 1986).
6
Belin, D., D. Baccino, A. Wohlwend, A. Estreicher, J. Hurate, and J.-D. Vassalli. "A CELLULAR RECEPTOR FOR UROKINASE-TYPE PLASMINOGEN ACTIVATOR." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642957.
Full textAbstract:
Recent cell biological and biochemical studies on the urokinase-type plasminogen activator (u-PA) have revealed an unsuspected property of this protein: it binds with high affinity and specificity to the plasma membrane of a number of cell types. Hence, while the interaction of tissue-type plasminogen activator (t-PA) with fibrin suggests a preferred role for this enzyme in the maintenance of fluidity of the extracellular milieu, the cellular binding of u-PA results in the focalisation of plasmin generation to the close environment of the cell surface; this appears as an optimal configuration if u-PA is to participate in the enzymatic events required for cell migration.The available information on the cellular binding of u-PA can be summarized as follows:1. Human monocytes-macrophages, monocyte-like cell lines, fibroblasts, and a variety of other cell lines all express u-PA binding sites. The number of u-PA binding sites on a given cell type may vary as a function of the functional state of the cells. In some cases all sites are occupied by “endogenous” u-PA.2. Binding does not require u-PA activity, and prou-PA binds with the same affinity as does the active enzyme.3. The Kd for u-PA binding is between 1 and 10×10-10 M. The binding site appears to be specific for u-PA.4. Binding requires the presence of the A chain of u-PA; the growth factor module of the A chain is involved in this interaction.5. Bound enzyme does not dissociate readily, nor is it rapidly endocytosed; most importantly, it retains catalytic activity.Studies in progress are aimed at further defining the u-PA determinants responsible for binding. In this context it is noteworthy that there is a tight species specificity of binding: human and murine u-PA, for instance, bind only to cells of the homologous species. Characterization of the u-PA binding site suggests that it is an integral membrane protein that includes at least one Mf 50.000 polypeptide chain.In addition to allowing for the peri-cellular focalisation of u-PA catalysed proteolysis, expression of the u-PA binding site provides a mecanism whereby one cell type can acquire membrane-bound u-PA activity following secretion of the (pro)enzyme by another cell population. A striking example of this is the binding of u-PA, synthesized by the epithelial layer of the male genital tract, to the head region of murine spermatozoa.
7
Shattil, S. J., J. A. Hoxie, M. Cunningham, C. S. Abrahms, J. O’Brien, and Z. Budzynski. "DETECTION OF ACTIVATED PLATELETS IN WHOLE BLOOD BY FLOW CYTOMETRY." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643830.
Full textAbstract:
Platelets may become activated in a number of clinical disorders and participate in thrombus formation. We have developed a direct test for activated platelets in whole blood that utilizes dual-color flow cytometry and requires no washing steps. Platelets were distinguished from erythrocytes and white blood cells in the flow cytometer by labeling the platelets with biotin-AP1, an antibody specific for membrane glycoprotein lb, and analyzing the cells for phycoerythrin-streptavidin fluorescence. Membrane surface changes resulting from platelet activation were detected with three different FITC-labeled monoclonal antibodies: 1) PAC1, an antibody specific for the fibrinogen receptor on activated platelets; 2) 9F9, which binds to the D-domain of fibrinogen and detects platelet-bound fibrinogen; and 3) S12, which binds to an alpha-granule membrane protein that associates with the platelet surface during secretion. Unstimulated platelets demonstrated no PAC1, 9F9, or S12-specific fluorescence, indicating that they did not bind these antibodies. Upon stimulation with agonists, however, the platelets demonstrated a dose-dependent increase in FITC-fluorescence. The binding of 9F9 to activated platelets required fibrinogen. Low concentrations of ADP and epinephrine, which induce fibrinogen receptors but little secretion, stimulated near-maximal PAC1 or 9F9 binding but little S12 binding. On the other hand, a concentration of phorbol myristate acetate that evokes full platelet aggregation and secretion induced maximal binding of all three antibodies. When blood samples containing activated and non-activated platelets were mixed, as few as 0.8% activated platelets could be detected by this technique. There was a direct correlation between ADP-induced FITC-PAC1 binding and binding determined in a conventional 125I-PAC1 binding assay (r = 0.99; p < 0.001). These studies demonstrate that activated platelets can be reliably detected in whole blood using activation-dependent monoclonal antibodies and flow cytometry. This method may be useful to assess the degree of platelet activation and the efficacy platelet inhibitor therapy in thrombotic disorders.
8
Ryckewaert, J. J., O. Valiron, I. A. Newton, E. Concord, M. Prenant, and E. Berthier. "STUDIES ON THE INVOLVEMENTOF GPIIb/IIIa COMPLEX IN PLATELET AGGREGATION WITH TWO MONOCLONAL ANTIBODIES." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643706.
Full textAbstract:
The involvement of the glycoproteins IIb/IIIa in the binding of fibrinogen to stimulated platelets and in the aggregation of these cells is well documented. Monoclonal antibodies (MoAb) directedagainst these two glycoproteins are useful probes in functional studies. Two MoAbs have been obtained against thetwo glycoproteins in their heterodimer form. Both MoAbs immunoprecipitate the complex from platelet lysates and only bind to platelets if the complex of the two glycoproteins is not dissociated.Studies onthe effect of the two MoAbs on platelet function have been performed. Firstly CS9,a murine IgG 2a, inhibited the binding of fibrinogen to stimulated platelets and prevented platelet aggregation. Fab CS9 obtained bypapain digestion had a similar activity. The binding of I125 Fab CS9 to resting platelets was similar to that of ADP-stimulated platelets (30 000 MoAbs/platelet). Similar behaviour of MoAbs against GPIIb/IIIa has been repeatedly reported and is considered as evidence that the fibrinogen receptor is the GPIIb/IIIa complex. The second MoAb (CS3),an IgGJ, subtype had a different action on platelet function.Contrary to all other known antibodies directed against the GPIIb/IIIa complex, CS3 or (Fab’2)CS3 induced the bindingof fibrinogen to platelet in the absence ofany plateletstimuli. Washed platelets in the presenceof CS3 underwent immediate and extensive aggregation, even in the absenceof fibrinogen. The stimulatory activity of MoAb CS3 on platelet can be eliminated by PGEJ. Monovalent CS3 (Fab fragment) failed to exhibit the properties of the parent antibody and had no effect on platelet function. The most likely explanation of the action of CS3 on platelet function may be that crosslinking of two GPIIb/IIIa complex mediated by the antibody leads to platelet stimulation. Whetheror not this mechanism is evocative of a physiological event when platelets are stimulated remains to be demonstrated. When both MoAbs are used in combination, the binding of fibrinogen and platelet aggregation are prevented by CS9 despite the stimulatory activity of CS3. Thus both MoAbsareable to bind to the GPIIb/IIIa complexat the same time.
9
Brewer, Bryson M., Yandong Gao, Rebecca M. Sappington, and Deyu Li. "Microfluidic Molecular Trap: Probing Extracellular Signaling by Selectively Blocking Exchange of Specific Molecules in Cell-Cell Interactions." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64489.
Full textAbstract:
Communication among cell populations is achieved via a wide variety of soluble, extracellular signaling molecules [1]. In order to investigate the role of specific molecules in a cellular process, researchers often utilize in vitro cell culture techniques in which the molecule under question has been removed from the signaling pathway. Traditionally, this has been accomplished by eliminating the gene in the cell that is responsible for coding the targeted ligand/receptor by using modern DNA technology such as gene knockout; however, this process is expensive, time-consuming, and labor intensive. Previously, we have demonstrated a microfluidic platform that uses a semi-permeable barrier with embedded receptor-coated nanoparticles to selectively remove a specific molecule or ligand from the extracellular signaling pathway in a cell co-culture environment [2]. This initial proof-of-principle was conducted using biotinylated nanoparticles and fluorescently tagged avidin molecules, as the avidin/biotin complex is the strongest known non-covalent interaction between a protein and a ligand (Dissociation constant kd = 10−15 M). Also, the trap was only effective for short time periods (<15 min) because the high concentration of fluorescently tagged avidin molecules required for visualization quickly saturated the barrier. However, nearly all biologically relevant ligand-receptor interactions have lower binding affinities than the avidin-biotin complex, with dissociation constants that are larger by several orders of magnitude. In addition, many in vitro cell culture experiments are conducted over multiple hours or days. Thus, a practically useful molecular trap device must be able to operate in a lower binding affinity regime while also lasting for extended time periods. Here we present results in which a biotinylated-particle barrier was used to successfully block lower concentrations of fluorescently tagged avidin for multiple days, showcasing the applicability of the device for long term experiments. In addition, we introduce a modified molecular trap in which the protein A/goat IgG complex was used to demonstrate the effectiveness of the platform for lower binding affinity protein-ligand interactions. These results indicate the potential usefulness of the microfluidic molecular trap platform for probing extracellular signaling pathways.
10
Gray, S. J., and S. Heptinstall. "INTERACTIONS BETWEEn PGE2 AND INHIBITORS OF PLATELET AGGREGATION THAT ACT THROUGH cAMP." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643582.
Full textAbstract:
PGE2 has a biphasic effect on platelet aggregation with low concentrations of the prostaglandin potentiating aggregation and high concentrations inhibiting it. In this investigation we have studied the interaction of PGE2 with agents that inhibit platelet aggregation through an effect on cAMP. The agents chosen raise the level of cAMP in platelets by different mechanisms: PGI2, PGD9 and adenosine combine with specific surface-located receptors and stimulate adenylate cyclase (AC) via a guanine nucleotide-binding protein (GNBP), forskolin stimulates AC directly, and AH-P 719 and DN 9693 inhibit cAMP phosphodiesterase (PDE). ADP-induced platelet aggregation was measured in platelet-rich plasma and cAMP was measured in platelets labelled with 3H-adenine.PGE2 alone potentiated platelet aggregation at concentrations from 10™8 -10™6 M and inhibited aggregation at 10™5M. PGE2 did not reduce cAMP levels at any concentration and increased cAMP levels at concentrations > 10™6 M, profcably by stimulating AC.PGI2 (10™9 -10™8 M), PGD2 (10™7 -5×10™6 M) and adenosine (8×l0™5-2×10™4 M) increased the level of cAMP in platelets and inhibited aggregation these changes were reversed by low concentrations of PGE2 (10™8-10™6M).Forskolin (5×10™6-2.5×10™5M), AH-P 719 (10™7-10™5M) and DN 9693 (5×10™6 -10™5M) increased the level of cAMP in platelets and inhibited aggregation. However, PGE2 did not reverse the inhibitory effects of these particular agents. In contrast, PGE2 potentiated the effects of the agents at all the concentrations of PGE2 that were tested (10™8-10™5M).The different results obtained with PGE2 in combination with agents that act via surface-located receptors compared with agents that stimulate AC directly or act through PDE, suggest that PGE2 may potentiate platelet aggregation by acting at a point between the platelet receptor and AC i.e. GNBP.PGE2 is one of the major prostaglandins synthesised by human microvascular endothelial cells and interstitial cells of the renal medulla. Since it reverses the inhibitory effects of some AC stimulators but adds to those of PDE inhibitors, the latter may have greater potential as anti-thrombotic agents in the micro-circulation and intra-renal circulation.