Artículos de revistas: "FKBP12 protein"

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Wang, Chin-Chou, Wan-Jou Shen, Gangga Anuraga, Yu-Hsiu Hsieh, Hoang Dang Khoa Ta, Do Thi Minh Xuan, Chiu-Fan Shen, Chih-Yang Wang y Wei-Jan Wang. "Penetrating Exploration of Prognostic Correlations of the FKBP Gene Family with Lung Adenocarcinoma". Journal of Personalized Medicine 13, n.º 1 (26 de diciembre de 2022): 49. http://dx.doi.org/10.3390/jpm13010049.

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The complexity of lung adenocarcinoma (LUAD), the development of which involves many interacting biological processes, makes it difficult to find therapeutic biomarkers for treatment. FK506-binding proteins (FKBPs) are composed of 12 members classified as conservative intracellular immunophilin family proteins, which are often connected to cyclophilin structures by tetratricopeptide repeat domains and have peptidyl prolyl isomerase activity that catalyzes proline from residues and turns the trans form into the cis form. Since FKBPs belong to chaperone molecules and promote protein folding, previous studies demonstrated that FKBP family members significantly contribute to the degradation of damaged, misfolded, abnormal, and foreign proteins. However, transcript expressions of this gene family in LUAD still need to be more fully investigated. In this research, we adopted high-throughput bioinformatics technology to analyze FKBP family genes in LUAD to provide credible information to clinicians and promote the development of novel cancer target drugs in the future. The current data revealed that the messenger (m)RNA levels of FKBP2, FKBP3, FKBP4, FKBP10, FKBP11, and FKBP14 were overexpressed in LUAD, and FKBP10 had connections to poor prognoses among LUAD patients in an overall survival (OS) analysis. Based on the above results, we selected FKBP10 to further conduct a comprehensive analysis of the downstream pathway and network. Through a DAVID analysis, we found that FKBP10 was involved in mitochondrial electron transport, NADH to ubiquinone transport, mitochondrial respiratory chain complex I assembly, etc. The MetaCore pathway analysis also indicated that FKBP10 was involved in "Ubiquinone metabolism", "Translation_(L)-selenoaminoacid incorporation in proteins during translation", and "Transcription_Negative regulation of HIF1A function". Collectively, this study revealed that FKBP family members are both significant prognostic biomarkers for lung cancer progression and promising clinical therapeutic targets, thus providing new targets for treating LUAD patients.

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ZENG, Baifei, J. Randy MACDONALD, G. James BANN, Konrad BECK, E. Jay GAMBEE, A. Bruce BOSWELL y Peter Hans BÄCHINGER. "Chicken FK506-binding protein, FKBP65, a member of the FKBP family of peptidylprolyl cis–trans isomerases, is only partially inhibited by FK506". Biochemical Journal 330, n.º 1 (15 de febrero de 1998): 109–14. http://dx.doi.org/10.1042/bj3300109.

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The chicken FK506-binding protein FKBP65, a peptidylprolyl cis-trans isomerase, is a rough endoplasmic reticulum protein that contains four domains homologous to FKBP13, another rough endoplasmic reticulum PPIase. Analytical ultracentrifugation suggests that in FKBP65 these four domains are arranged in a linear extended structure with a length of about 26 nm and a diameter of about 3 nm. All four domains are therefore expected to be accessible to substrates. The specificity of FKBP65 towards a number of peptide substrates was determined. The specific activity of FKBP65 is generally lower than that of FKBP12 when expressed as a per domain activity. The substrate specificity of FKBP65 also differs from that of FKBP12. Inhibition studies show that only one of the four domains can be inhibited by FK506, a powerful inhibitor of all other known FKBPs. Furthermore, the same domain seems to be susceptible to inhibition by cyclosporin A. No other FKBPs were shown to be inhibited by cyclosporin A. It is also shown that FKBP65 can catalyse the re-folding of type III collagen in vitro with a kcat/Km = 4.3×103 M-1·s-1.

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Barg, S., J. A. Copello y S. Fleischer. "Different interactions of cardiac and skeletal muscle ryanodine receptors with FK-506 binding protein isoforms". American Journal of Physiology-Cell Physiology 272, n.º 5 (1 de mayo de 1997): C1726—C1733. http://dx.doi.org/10.1152/ajpcell.1997.272.5.c1726.

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In the present study, we compare functional consequences of dissociation and reconstitution of binding proteins FKBP12 and FKBP12.6 with ryanodine receptors from cardiac (RyR2) and skeletal muscle (RyR1). The skeletal muscle RyR1 channel became activated on removal of endogenously bound FKBP12, consistent with previous reports. Both FKBP12 and FKBP12.6 rebind to FKBP-depleted RyR1 and restore its quiescent channel behavior by altering ligand sensitivity, as studied by single-channel recordings in planar lipid bilayers, and macroscopic behavior of the channels (ryanodine binding and net energized Ca2- uptake). By contrast, removal of FKBP12.6 from the cardiac RyR2 did not modulate the function of the channel using the same types of assays as for RyR1. FKBP12 or FKBP12.6 had no effect on channel activity of FKBP12.6-depleted cardiac RyR2, although FKBP12.6 rebinds. Our studies reveal important differences between the two ryanodine receptor isoforms with respect to their functional interaction with FKBP12 and FKBP12.6.

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Chen, Hui, Sourajit M. Mustafi, David M. LeMaster, Zhong Li, Annie Héroux, Hongmin Li y Griselda Hernández. "Crystal structure and conformational flexibility of the unligated FK506-binding protein FKBP12.6". Acta Crystallographica Section D Biological Crystallography 70, n.º 3 (15 de febrero de 2014): 636–46. http://dx.doi.org/10.1107/s1399004713032112.

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The primary known physiological function of FKBP12.6 involves its role in regulating the RyR2 isoform of ryanodine receptor Ca2+channels in cardiac muscle, pancreatic β islets and the central nervous system. With only a single previously reported X-ray structure of FKBP12.6, bound to the immunosuppressant rapamycin, structural inferences for this protein have been drawn from the more extensive studies of the homologous FKBP12. X-ray structures at 1.70 and 1.90 Å resolution fromP21andP3121 crystal forms are reported for an unligated cysteine-free variant of FKBP12.6 which exhibit a notable diversity of conformations. In one monomer from theP3121 crystal form, the aromatic ring of Phe59 at the base of the active site is rotated perpendicular to its typical orientation, generating a steric conflict for the immunosuppressant-binding mode. The peptide unit linking Gly89 and Val90 at the tip of the protein-recognition `80s loop' is flipped in theP21crystal form. Unlike the >30 reported FKBP12 structures, the backbone conformation of this loop closely follows that of the first FKBP domain of FKBP51. The NMR resonances for 21 backbone amides of FKBP12.6 are doubled, corresponding to a slow conformational transition centered near the tip of the 80s loop, as recently reported for 31 amides of FKBP12. The comparative absence of doubling for residues along the opposite face of the active-site pocket in FKBP12.6 may in part reflect attenuated structural coupling owing to increased conformational plasticity around the Phe59 ring.

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Bultynck, Geert, Daniela Rossi, Geert Callewaert, Ludwig Missiaen, Vincenzo Sorrentino, Jan B. Parys y Humbert De Smedt. "The Conserved Sites for the FK506-binding Proteins in Ryanodine Receptors and Inositol 1,4,5-Trisphosphate Receptors Are Structurally and Functionally Different". Journal of Biological Chemistry 276, n.º 50 (11 de octubre de 2001): 47715–24. http://dx.doi.org/10.1074/jbc.m106573200.

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We compared the interaction of the FK506-binding protein (FKBP) with the type 3 ryanodine receptor (RyR3) and with the type 1 and type 3 inositol 1,4,5-trisphosphate receptor (IP3R1 and IP3R3), using a quantitative GST-FKBP12 and GST-FKBP12.6 affinity assay. We first characterized and mapped the interaction of the FKBPs with the RyR3. GST-FKBP12 as well as GST-FKBP12.6 were able to bind ∼30% of the solubilized RyR3. The interaction was completely abolished by FK506, strengthened by the addition of Mg2+, and weakened in the absence of Ca2+but was not affected by the addition of cyclic ADP-ribose. By using proteolytic mapping and site-directed mutagenesis, we pinpointed Val2322, located in the central modulatory domain of the RyR3, as a critical residue for the interaction of RyR3 with FKBPs. Substitution of Val2322for leucine (as in IP3R1) or isoleucine (as in RyR2) decreased the binding efficiency and shifted the selectivity to FKBP12.6; substitution of Val2322for aspartate completely abolished the FKBP interaction. Importantly, the occurrence of the valylprolyl residue as α-helix breaker was an important determinant of FKBP binding. This secondary structure is conserved among the different RyR isoforms but not in the IP3R isoforms. A chimeric RyR3/IP3R1, containing the core of the FKBP12-binding site of IP3R1 in the RyR3 context, retained this secondary structure and was able to interact with FKBPs. In contrast, IP3Rs did not interact with the FKBP isoforms. This indicates that the primary sequence in combination with the local structural environment plays an important role in targeting the FKBPs to the intracellular Ca2+-release channels. Structural differences in the FKBP-binding site of RyRs and IP3Rs may contribute to the occurrence of a stable interaction between RyR isoforms and FKBPs and to the absence of such interaction with IP3Rs.

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Vervliet, Tim, Jan B. Parys y Geert Bultynck. "Bcl-2 and FKBP12 bind to IP3 and ryanodine receptors at overlapping sites: the complexity of protein–protein interactions for channel regulation". Biochemical Society Transactions 43, n.º 3 (1 de junio de 2015): 396–404. http://dx.doi.org/10.1042/bst20140298.

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The 12- and 12.6-kDa FK506-binding proteins, FKBP12 (12-kDa FK506-binding protein) and FKBP12.6 (12.6-kDa FK506-binding protein), have been implicated in the binding to and the regulation of ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate receptors (IP3Rs), both tetrameric intracellular Ca2+-release channels. Whereas the amino acid sequences responsible for FKBP12 binding to RyRs are conserved in IP3Rs, FKBP12 binding to IP3Rs has been questioned and could not be observed in various experimental models. Nevertheless, conservation of these residues in the different IP3R isoforms and during evolution suggested that they could harbour an important regulatory site critical for IP3R-channel function. Recently, it has become clear that in IP3Rs, this site was targeted by B-cell lymphoma 2 (Bcl-2) via its Bcl-2 homology (BH)4 domain, thereby dampening IP3R-mediated Ca2+ flux and preventing pro-apoptotic Ca2+ signalling. Furthermore, vice versa, the presence of the corresponding site in RyRs implied that Bcl-2 proteins could associate with and regulate RyR channels. Recently, the existence of endogenous RyR–Bcl-2 complexes has been identified in primary hippocampal neurons. Like for IP3Rs, binding of Bcl-2 to RyRs also involved its BH4 domain and suppressed RyR-mediated Ca2+ release. We therefore propose that the originally identified FKBP12-binding site in IP3Rs is a region critical for controlling IP3R-mediated Ca2+ flux by recruiting Bcl-2 rather than FKBP12. Although we hypothesize that anti-apoptotic Bcl-2 proteins, but not FKBP12, are the main physiological inhibitors of IP3Rs, we cannot exclude that Bcl-2 could help engaging FKBP12 (or other FKBP isoforms) to the IP3R, potentially via calcineurin.

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Ozawa, Terutaka. "Effects of FK506 on Ca2+ Release Channels (Review)". Perspectives in Medicinal Chemistry 2 (enero de 2008): PMC.S382. http://dx.doi.org/10.4137/pmc.s382.

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Tacrolimus (FK506), which was isolated from the fermentation broth of Streptomyces tsukubaensis No. 9993, has an immunosuppressive effect. In T-lymphocytes, FK506 binds to the intracellular receptor, a 12-kDa FK506-binding protein (FKBP12). The FK506-FKBP12 complex binds to the phosphatase calcineurin (CN) and inhibits the activity of CN. By inhibition of the activity of CN, dephosphorylation of a nuclear factor of activated T-cells (NFAT) is inhibited, and translocation of the NFAT to the nucleus is suppressed. Thereby, the production of T-cell-derived mediators such as interleukin 2 (IL-2) is inhibited, and the proliferation of cytotoxic T-cells is suppressed. In muscle cells, FKBP12 and FKBP12.6 are associated with ryanodine-sensitive Ca2+ release channels (ryanodine receptors: RyRs) on the skeletal and cardiac muscle sarcoplasmic reticulum (SR), respectively. FK506 modulates the RyR by dissociating FKBP12 or FKBP12.6 from the RyR complex. FKBP12 is also associated with inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ release channels (IP3 receptors: IP3Rs) on the endoplasmic reticulum (ER) of non-muscle cells. The IP3R-FKBP12 complex binds to CN, which dephosphorylates the protein kinase C (PKC) phosphorylation site on the receptor. When FKBP12 is dissociated from the IP3R complex by FK506, CN is also dissociated from the IP3R. Thereby, the IP3R is phosphorylated by PKC, and the receptor is modulated. Recently, it was found that FK506 itself induces Ca2+ release through RyRs in some tissues.

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Dolinski, Kara J. y Joseph Heitman. "Hmo1p, a High Mobility Group 1/2 Homolog, Genetically and Physically Interacts With the Yeast FKBP12 Prolyl Isomerase". Genetics 151, n.º 3 (1 de marzo de 1999): 935–44. http://dx.doi.org/10.1093/genetics/151.3.935.

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Abstract The immunosuppressive drugs FK506 and rapamycin bind to the cellular protein FKBP12, and the resulting FKBP12-drug complexes inhibit signal transduction. FKBP12 is a ubiquitous, highly conserved, abundant enzyme that catalyzes a rate-limiting step in protein folding: peptidyl-prolyl cis-trans isomerization. However, FKBP12 is dispensible for viability in both yeast and mice, and therefore does not play an essential role in protein folding. The functions of FKBP12 may involve interactions with a number of partner proteins, and a few proteins that interact with FKBP12 in the absence of FK506 or rapamycin have been identified, including the ryanodine receptor, aspartokinase, and the type II TGF-β receptor; however, none of these are conserved from yeast to humans. To identify other targets and functions of FKBP12, we have screened for mutations that are synthetically lethal with an FKBP12 mutation in yeast. We find that mutations in HMO1, which encodes a high mobility group 1/2 homolog, are synthetically lethal with mutations in the yeast FPR1 gene encoding FKBP12. Δhmo1 and Δfpr1 mutants share two phenotypes: an increased rate of plasmid loss and slow growth. In addition, Hmo1p and FKBP12 physically interact in FKBP12 affinity chromatography experiments, and two-hybrid experiments suggest that FKBP12 regulates Hmo1p-Hmo1p or Hmo1p-DNA interactions. Because HMG1/2 proteins are conserved from yeast to humans, our findings suggest that FKBP12-HMG1/2 interactions could represent the first conserved function of FKBP12 other than mediating FK506 and rapamycin actions.

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Tang, Wang-Xian, Ya-Fei Chen, Ai-Ping Zou, William B. Campbell y Pin-Lan Li. "Role of FKBP12.6 in cADPR-induced activation of reconstituted ryanodine receptors from arterial smooth muscle". American Journal of Physiology-Heart and Circulatory Physiology 282, n.º 4 (1 de abril de 2002): H1304—H1310. http://dx.doi.org/10.1152/ajpheart.00843.2001.

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cADP ribose (cADPR) serves as second messenger to activate the ryanodine receptors (RyRs) of the sarcoplasmic reticulum (SR) and mobilize intracellular Ca2+in vascular smooth muscle cells. However, the mechanisms mediating the effect of cADPR remain unknown. The present study was designed to determine whether FK-506 binding protein 12.6 (FKBP12.6), an accessory protein of the RyRs, plays a role in cADPR-induced activation of the RyRs. A 12.6-kDa protein was detected in bovine coronary arterial smooth muscle (BCASM) and cultured CASM cells by being immunoblotted with an antibody against FKBP12, which also reacted with FKBP12.6. With the use of planar lipid bilayer clamping techniques, FK-506 (0.01–10 μM) significantly increased the open probability ( NP O) of reconstituted RyR/Ca2+release channels from the SR of CASM. This FK-506-induced activation of RyR/Ca2+ release channels was abolished by pretreatment with anti-FKBP12 antibody. The RyRs activator cADPR (0.1–10 μM) markedly increased the activity of RyR/Ca2+ release channels. In the presence of FK-506, cADPR did not further increase the NP O of RyR/Ca2+ release channels. Addition of anti-FKBP12 antibody also completely blocked cADPR-induced activation of these channels, and removal of FKBP12.6 by preincubation with FK-506 and subsequent gradient centrifugation abolished cADPR-induced increase in the NP O of RyR/Ca2+ release channels. We conclude that FKBP12.6 plays a critical role in mediating cADPR-induced activation of RyR/Ca2+ release channels from the SR of BCASM.

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Reiken, Steven, Alain Lacampagne, Hua Zhou, Aftab Kherani, Stephan E. Lehnart, Chris Ward, Fannie Huang et al. "PKA phosphorylation activates the calcium release channel (ryanodine receptor) in skeletal muscle". Journal of Cell Biology 160, n.º 6 (10 de marzo de 2003): 919–28. http://dx.doi.org/10.1083/jcb.200211012.

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The type 1 ryanodine receptor (RyR1) on the sarcoplasmic reticulum (SR) is the major calcium (Ca2+) release channel required for skeletal muscle excitation–contraction (EC) coupling. RyR1 function is modulated by proteins that bind to its large cytoplasmic scaffold domain, including the FK506 binding protein (FKBP12) and PKA. PKA is activated during sympathetic nervous system (SNS) stimulation. We show that PKA phosphorylation of RyR1 at Ser2843 activates the channel by releasing FKBP12. When FKB12 is bound to RyR1, it inhibits the channel by stabilizing its closed state. RyR1 in skeletal muscle from animals with heart failure (HF), a chronic hyperadrenergic state, were PKA hyperphosphorylated, depleted of FKBP12, and exhibited increased activity, suggesting that the channels are “leaky.” RyR1 PKA hyperphosphorylation correlated with impaired SR Ca2+ release and early fatigue in HF skeletal muscle. These findings identify a novel mechanism that regulates RyR1 function via PKA phosphorylation in response to SNS stimulation. PKA hyperphosphorylation of RyR1 may contribute to impaired skeletal muscle function in HF, suggesting that a generalized EC coupling myopathy may play a role in HF.

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Cheung, Ming-Yan, Wan-Kin Auyeung, Kwan-Pok Li y Hon-Ming Lam. "A Rice Immunophilin Homolog, OsFKBP12, Is a Negative Regulator of Both Biotic and Abiotic Stress Responses". International Journal of Molecular Sciences 21, n.º 22 (20 de noviembre de 2020): 8791. http://dx.doi.org/10.3390/ijms21228791.

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A class of proteins that were discovered to bind the immunosuppressant drug FK506, called FK506-binding proteins (FKBPs), are members of a sub-family of immunophilins. Although they were first identified in human, FKBPs exist in all three domains of life. In this report, a rice FKBP12 homolog was first identified as a biotic stress-related gene through suppression subtractive hybridization screening. By ectopically expressing OsFKBP12 in the heterologous model plant system, Arabidopsis thaliana, for functional characterization, OsFKBP12 was found to increase susceptibility of the plant to the pathogen, Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). This negative regulatory role of FKBP12 in biotic stress responses was also demonstrated in the AtFKBP12-knockout mutant, which exhibited higher resistance towards Pst DC3000. Furthermore, this higher-plant FKBP12 homolog was also shown to be a negative regulator of salt tolerance. Using yeast two-hybrid tests, an ancient unconventional G-protein, OsYchF1, was identified as an interacting partner of OsFKBP12. OsYchF1 was previously reported as a negative regulator of both biotic and abiotic stresses. Therefore, OsFKBP12 probably also plays negative regulatory roles at the convergence of biotic and abiotic stress response pathways in higher plants.

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Widjajakusuma, Elisabeth Catherine, Monica Frederica, Kornelius Kaweono, Arkenjela Shea, Gracia De Sales Lodhu Jawa, Yohanes Aliandra Kelan, Ajeng Indah et al. "Studi Perbandingan Sifat Struktur dan Dinamika Bentuk Apo dan Holo dari FKBP12 dan Mip dengan Menggunakan Simulasi Dinamika Molekul". Jurnal Farmasi Sains dan Terapan 9, n.º 1 (febrero de 2022): 24–29. http://dx.doi.org/10.33508/jfst.v9i1.4059.

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Interaksi protein danligan pada sisi pengikatan merupakan topik penting dalam desain obat dan proses prediksi fungsi protein. FKBP12 dan Mip(macrophage infectivity potentiator)termasuk dalam keluarga protein FKBP dengan sisi pengikatan yang kemiripannya sangat tinggi. Oleh karena itu untuk mendapatkan ligan yang selektif tidaklah mudah. Tujuan penelitian ini untuk membandingkan sifat struktur dan dinamis dari FKBP12 dan Mip dalam bentuk holo (membentuk kompleks dengan suatu ligan) dan bentuk apo (tidak terikat dengan ligan) dengan menggunakan simulasi dinamika molekul selama 40 ns dengan penambahan energi potensial selama 10 ns. Penggantian ligan rapamycin dengan ligan yang lebih kecil, yaitu turunan asam pipecolat, menyebabkan perubahan strukturpada FKBP12 dibandingkan Mip terutama pada asam amino Q81/E54, V82/F55, I83/I56, W86/W59, Y109/Y82, P117/H87, dan I118/I90.Hal ini memberikan informasi untuk pengembangan ligan yang selektif.

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Caraveo, Gabriela, Martin Soste, Valentina Cappelleti, Saranna Fanning, Damian B. van Rossum, Luke Whitesell, Yanmei Huang et al. "FKBP12 contributes to α-synuclein toxicity by regulating the calcineurin-dependent phosphoproteome". Proceedings of the National Academy of Sciences 114, n.º 52 (11 de diciembre de 2017): E11313—E11322. http://dx.doi.org/10.1073/pnas.1711926115.

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Calcineurin is an essential Ca2+-dependent phosphatase. Increased calcineurin activity is associated with α-synuclein (α-syn) toxicity, a protein implicated in Parkinson’s Disease (PD) and other neurodegenerative diseases. Calcineurin can be inhibited with Tacrolimus through the recruitment and inhibition of the 12-kDa cis-trans proline isomerase FK506-binding protein (FKBP12). Whether calcineurin/FKBP12 represents a native physiologically relevant assembly that occurs in the absence of pharmacological perturbation has remained elusive. We leveraged α-syn as a model to interrogate whether FKBP12 plays a role in regulating calcineurin activity in the absence of Tacrolimus. We show that FKBP12 profoundly affects the calcineurin-dependent phosphoproteome, promoting the dephosphorylation of a subset of proteins that contributes to α-syn toxicity. Using a rat model of PD, partial elimination of the functional interaction between FKBP12 and calcineurin, with low doses of the Food and Drug Administration (FDA)-approved compound Tacrolimus, blocks calcineurin’s activity toward those proteins and protects against the toxic hallmarks of α-syn pathology. Thus, FKBP12 can endogenously regulate calcineurin activity with therapeutic implications for the treatment of PD.

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Fruman, D. A., B. E. Bierer, J. E. Benes, S. J. Burakoff, K. F. Austen y H. R. Katz. "The complex of FK506-binding protein 12 and FK506 inhibits calcineurin phosphatase activity and IgE activation-induced cytokine transcripts, but not exocytosis, in mouse mast cells." Journal of Immunology 154, n.º 4 (15 de febrero de 1995): 1846–51. http://dx.doi.org/10.4049/jimmunol.154.4.1846.

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Abstract FK506 and cyclosporin A (CsA) are immunosuppressive agents that inhibit IL-2 production by activated T cells, but only CsA inhibits IgE activation-induced cytokine transcripts in mouse IL-3-dependent, bone marrow-derived mast cells (BMMC). We previously associated the resistance of BMMC to FK506 with a deficiency in the expression of FK506 binding protein (FKBP) 12, a molecule that forms a complex with FK506 capable of inhibiting calcineurin phosphatase activity in vitro. In this report, we establish that FKBP12 mediates FK506 inhibition of both calcineurin phosphatase activity and IgE activation-induced cytokine transcripts in a Kirsten murine sarcoma virus-immortalized mast cell line that is FKBP12 deficient. Overexpression of FKBP12 by transfection enhanced the ability of FK506 to inhibit calcineurin phosphatase activity (IC50 = 2 nM), compared with cells transfected with the expression vector alone (IC50 > 30 nM). The IC50 value for FK506 inhibition of IgE activation-induced transcripts for TNF-alpha decreased from 40 nM in vector control cells to 10 nM in FKBP12 transfectants. Similarly, the IC50 value for inhibition of IL-6 transcripts decreased from > 1000 nM in vector control cells to 35 nM in FKBP12 transfectants. In contrast, activation-elicited release of the secretory granule mediator beta-hexosaminidase was only partially inhibited by FK506 at 1000 nM, regardless of the levels of FKBP12 expressed by the cells. Thus, FKBP12 is the dominant cytosolic protein that mediates FK506 inhibition of TNF-alpha and IL-6 transcripts.

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Sengupta, Prabuddha, Prasanna Satpute-Krishnan, Arnold Y. Seo, Dylan T. Burnette, George H. Patterson y Jennifer Lippincott-Schwartz. "ER trapping reveals Golgi enzymes continually revisit the ER through a recycling pathway that controls Golgi organization". Proceedings of the National Academy of Sciences 112, n.º 49 (23 de noviembre de 2015): E6752—E6761. http://dx.doi.org/10.1073/pnas.1520957112.

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Whether Golgi enzymes remain localized within the Golgi or constitutively cycle through the endoplasmic reticulum (ER) is unclear, yet is important for understanding Golgi dependence on the ER. Here, we demonstrate that the previously reported inefficient ER trapping of Golgi enzymes in a rapamycin-based assay results from an artifact involving an endogenous ER-localized 13-kD FK506 binding protein (FKBP13) competing with the FKBP12-tagged Golgi enzyme for binding to an FKBP-rapamycin binding domain (FRB)-tagged ER trap. When we express an FKBP12-tagged ER trap and FRB-tagged Golgi enzymes, conditions precluding such competition, the Golgi enzymes completely redistribute to the ER upon rapamycin treatment. A photoactivatable FRB-Golgi enzyme, highlighted only in the Golgi, likewise redistributes to the ER. These data establish Golgi enzymes constitutively cycle through the ER. Using our trapping scheme, we identify roles of rab6a and calcium-independent phospholipase A2 (iPLA2) in Golgi enzyme recycling, and show that retrograde transport of Golgi membrane underlies Golgi dispersal during microtubule depolymerization and mitosis.

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Liang, Jun, Jungwon Choi y Jon Clardy. "Refined structure of the FKBP12–rapamycin–FRB ternary complex at 2.2 Å resolution". Acta Crystallographica Section D Biological Crystallography 55, n.º 4 (1 de abril de 1999): 736–44. http://dx.doi.org/10.1107/s0907444998014747.

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The structure of the FKBP12–rapamycin–FRB ternary complex has now been refined at 2.2 Å resolution. The cell-cycle arrest agent rapamycin binds FK506-binding protein (FKBP12) and the FKBP12–rapamycin binding (FRB) domain of FKBP12–rapamycin associated protein (FRAP) simultaneously, and the inhibition of FRAP is responsible for rapamycin's biological activity. The conformation of rapamycin in the ternary complex is very similar to that observed in the FKBP12–rapamycin binary complex, with an r.m.s. difference of only 0.30 Å. However, a slight (9°) rotation repositions the FRB-binding face of rapamycin in the ternary complex. There are extensive rapamycin–protein interactions and relatively few interactions between the two protein partners FKBP12 and FRB, these interactions mainly involving residues in the 40s and 80s loops of FKBP12 and α1 and α4 of FRB. The high-resolution refinement has revealed the crucial role of several buried waters in the formation of the ternary complex.

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DARGAN, Sheila L., Edward J. A. LEA y Alan P. DAWSON. "Modulation of type-1 Ins(1,4,5)P3 receptor channels by the FK506-binding protein, FKBP12". Biochemical Journal 361, n.º 2 (8 de enero de 2002): 401–7. http://dx.doi.org/10.1042/bj3610401.

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FK506-binding protein (FKBP12) is highly expressed in neuronal tissue, where it is proposed to localize calcineurin to intracellular calcium-release channels, ryanodine receptors and Ins(1,4,5)P3 receptors (InsP3Rs). The effects of FKBP12 on ryanodine receptors have been well characterized but the nature and function of binding of FKBP12 to InsP3R is more controversial, with evidence for and against a tight interaction between these two proteins. To investigate this, we incorporated purified type-1 InsP3R from rat cerebellum into planar lipid bilayers to monitor the effects of exogenous recombinant FKBP12 on single-channel activity, using K+ as the current carrier. Here we report for the first time that FKBP12 causes a substantial change in single-channel properties of the type-1 InsP3R, specifically to increase the amount of time the channel spends in a fully open state. In the presence of ATP, FKBP12 can also induce co-ordinated gating with neighbouring receptors. The effects of FKBP12 were reversed by FK506. We also present data showing that rapamycin, at sub-optimal concentrations of Ins(2,4,5)P3, decreases the rate of calcium release from cerebellar microsomes. These results provide evidence for a direct functional interaction between FKBP12 and the type-1 InsP3R.

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Alarcón, C. M. y J. Heitman. "FKBP12 physically and functionally interacts with aspartokinase in Saccharomyces cerevisiae." Molecular and Cellular Biology 17, n.º 10 (octubre de 1997): 5968–75. http://dx.doi.org/10.1128/mcb.17.10.5968.

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The peptidyl-prolyl isomerase FKBP12 was originally identified as the intracellular receptor for the immunosuppressive drugs FK506 (tacrolimus) and rapamycin (sirolimus). Although peptidyl-prolyl isomerases have been implicated in catalyzing protein folding, the cellular functions of FKBP12 in Saccharomyces cerevisiae and other organisms are largely unknown. Using the yeast two-hybrid system, we identified aspartokinase, an enzyme that catalyzes an intermediate step in threonine and methionine biosynthesis, as an in vivo binding target of FKBP12. Aspartokinase also binds FKBP12 in vitro, and drugs that bind the FKBP12 active site, or mutations in FKBP12 surface and active site residues, disrupt the FKBP12-aspartokinase complex in vivo and in vitro.fpr1 mutants lacking FKBP12 are viable, are not threonine or methionine auxotrophs, and express wild-type levels of aspartokinase protein and activity; thus, FKBP12 is not essential for aspartokinase activity. The activity of aspartokinase is regulated by feedback inhibition by product, and genetic analyses reveal that FKBP12 is important for this feedback inhibition, possibly by catalyzing aspartokinase conformational changes in response to product binding.

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19

Dolinski, Kara, Christian Scholz, R. Scott Muir, Sabine Rospert, Franz X. Schmid, Maria E. Cardenas y Joseph Heitman. "Functions of FKBP12 and Mitochondrial Cyclophilin Active Site Residues In Vitro and In Vivo inSaccharomyces cerevisiae". Molecular Biology of the Cell 8, n.º 11 (noviembre de 1997): 2267–80. http://dx.doi.org/10.1091/mbc.8.11.2267.

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Cyclophilin and FK506 binding protein (FKBP) acceleratecis–trans peptidyl-prolyl isomerization and bind to and mediate the effects of the immunosuppressants cyclosporin A and FK506. The normal cellular functions of these proteins, however, are unknown. We altered the active sites of FKBP12 and mitochondrial cyclophilin from the yeast Saccharomyces cerevisiae by introducing mutations previously reported to inactivate these enzymes. Surprisingly, most of these mutant enzymes were biologically active in vivo. In accord with previous reports, all of the mutant enzymes had little or no detectable prolyl isomerase activity in the standard peptide substrate-chymotrypsin coupled in vitro assay. However, in a variation of this assay in which the protease is omitted, the mutant enzymes exhibited substantial levels of prolyl isomerase activity (5–20% of wild-type), revealing that these mutations confer sensitivity to protease digestion and that the classic in vitro assay for prolyl isomerase activity may be misleading. In addition, the mutant enzymes exhibited near wild-type activity with two protein substrates, dihydrofolate reductase and ribonuclease T1, whose folding is accelerated by prolyl isomerases. Thus, a number of cyclophilin and FKBP12 “active-site” mutants previously identified are largely active but protease sensitive, in accord with our findings that these mutants display wild-type functions in vivo. One mitochondrial cyclophilin mutant (R73A), and also the wild-type human FKBP12 enzyme, catalyze protein folding in vitro but lack biological activity in vivo in yeast. Our findings provide evidence that both prolyl isomerase activity and other structural features are linked to FKBP and cyclophilin in vivo functions and suggest caution in the use of these active-site mutations to study FKBP and cyclophilin functions.

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Pan, Zhenwei, Tomohiko Ai, Po-Cheng Chang, Ying Liu, Jijia Liu, Mitsunori Maruyama, Mohamed Homsi et al. "Atrial fibrillation and electrophysiology in transgenic mice with cardiac-restricted overexpression of FKBP12". American Journal of Physiology-Heart and Circulatory Physiology 316, n.º 2 (1 de febrero de 2019): H371—H379. http://dx.doi.org/10.1152/ajpheart.00486.2018.

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Cardiomyocyte-restricted overexpression of FK506-binding protein 12 transgenic (αMyHC-FKBP12) mice develop spontaneous atrial fibrillation (AF). The aim of the present study is to explore the mechanisms underlying the occurrence of AF in αMyHC-FKBP12 mice. Spontaneous AF was documented by telemetry in vivo and Langendorff-perfused hearts of αMyHC-FKBP12 and littermate control mice in vitro. Atrial conduction velocity was evaluated by optical mapping. The patch-clamp technique was applied to determine the potentially altered electrophysiology in atrial myocytes. Channel protein expression levels were evaluated by Western blot analyses. Spontaneous AF was recorded in four of seven αMyHC-FKBP12 mice but in none of eight nontransgenic (NTG) controls. Atrial conduction velocity was significantly reduced in αMyHC-FKBP12 hearts compared with NTG hearts. Interestingly, the mean action potential duration at 50% but not 90% was significantly prolonged in αMyHC-FKBP12 atrial myocytes compared with their NTG counterparts. Consistent with decreased conduction velocity, average peak Na+ current ( INa) density was dramatically reduced and the INa inactivation curve was shifted by approximately +7 mV in αMyHC-FKBP12 atrial myocytes, whereas the activation and recovery curves were unaltered. The Nav1.5 expression level was significantly reduced in αMyHC-FKBP12 atria. Furthermore, we found increases in atrial Cav1.2 protein levels and peak L-type Ca2+ current density and increased levels of fibrosis in αMyHC-FKBP12 atria. In summary, cardiomyocyte-restricted overexpression of FKBP12 reduces the atrial Nav1.5 expression level and mean peak INa, which is associated with increased peak L-type Ca2+ current and interstitial fibrosis in atria. The combined electrophysiological and structural changes facilitated the development of local conduction block and altered action potential duration and spontaneous AF. NEW & NOTEWORTHY This study addresses a long-standing riddle regarding the role of FK506-binding protein 12 in cardiac physiology. The work provides further evidence that FK506-binding protein 12 is a critical component for regulating voltage-gated sodium current and in so doing has an important role in arrhythmogenic physiology, such as atrial fibrillation.

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21

Batra, Jyotica, Harianto Tjong y Huan-Xiang Zhou. "Electrostatic effects on the folding stability of FKBP12". Protein Engineering Design and Selection 29, n.º 8 (5 de julio de 2016): 301–8. http://dx.doi.org/10.1093/protein/gzw014.

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22

Galat, Andrzej. "Compression of Large Sets of Sequence Data Reveals Fine Diversification of Functional Profiles in Multigene Families of Proteins: A Study for Peptidyl-Prolyl cis/trans Isomerases (PPIase)". Biomolecules 9, n.º 2 (11 de febrero de 2019): 59. http://dx.doi.org/10.3390/biom9020059.

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In this technical note, we describe analyses of more than 15,000 sequences of FK506-binding proteins (FKBP) and cyclophilins, also known as peptidyl-prolyl cis/trans isomerases (PPIases). We have developed a novel way of displaying relative changes of amino acid (AA)-residues at a given sequence position by using heat-maps. This type of representation allows simultaneous estimation of conservation level in a given sequence position in the entire group of functionally-related paralogues (multigene family of proteins). We have also proposed that at least two FKBPs, namely FKBP36, encoded by the Fkbp6 gene and FKBP51, encoded by the Fkbp5 gene, can form dimers bound via a disulfide bridge in the nucleus. This type of dimer may have some crucial function in the regulation of some nuclear complexes at different stages of the cell cycle.

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23

Jin, Liqing, Haruhiko Asano y C. Anthony Blau. "Stimulating Cell Proliferation Through the Pharmacologic Activation of c-kit". Blood 91, n.º 3 (1 de febrero de 1998): 890–97. http://dx.doi.org/10.1182/blood.v91.3.890.

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Abstract Previous studies have shown that expression of a membrane targeted chimeric protein containing the erythropoietin receptor (EpoR) cytoplasmic domain fused to the FK506-binding peptide FKBP12 allowed Ba/F3 cells to be rescued from interleukin-3 (IL-3) deprivation using a dimeric form of FK506, called FK1012. In this report, a similar approach is applied to the c-kit receptor. Expression of a membrane targeted fusion protein containing the c-kit receptor linked to one or more copies of FKBP12 allowed Ba/F3 cells to be switched from IL-3 dependence to FK1012-dependence. Similar results were obtained using an alternative dimerizer of FKBP12 domains called AP1510. Pharmacologic dimerization of chimeric proteins containing only a single FKBP12 domain confirmed that receptor dimerization is sufficient for proliferative signaling. Interestingly, while the proliferative effects of both FK1012 and AP1510 were reversible, FK1012-driven proliferation persisted for several days after drug withdrawal. Furthermore, much higher concentrations of FK506 were required to inhibit FK1012-mediated proliferation than were required to inhibit AP1510-mediated proliferation. The persistence of FK1012's effect appeared to be specific to clones expressing c-kit–containing fusion proteins. These results suggest that pharmacologically-responsive fusion proteins containing c-kitmay be useful for specifically and reversibly expanding genetically modified hematopoietic cell populations.

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24

Jin, Liqing, Haruhiko Asano y C. Anthony Blau. "Stimulating Cell Proliferation Through the Pharmacologic Activation of c-kit". Blood 91, n.º 3 (1 de febrero de 1998): 890–97. http://dx.doi.org/10.1182/blood.v91.3.890.890_890_897.

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Previous studies have shown that expression of a membrane targeted chimeric protein containing the erythropoietin receptor (EpoR) cytoplasmic domain fused to the FK506-binding peptide FKBP12 allowed Ba/F3 cells to be rescued from interleukin-3 (IL-3) deprivation using a dimeric form of FK506, called FK1012. In this report, a similar approach is applied to the c-kit receptor. Expression of a membrane targeted fusion protein containing the c-kit receptor linked to one or more copies of FKBP12 allowed Ba/F3 cells to be switched from IL-3 dependence to FK1012-dependence. Similar results were obtained using an alternative dimerizer of FKBP12 domains called AP1510. Pharmacologic dimerization of chimeric proteins containing only a single FKBP12 domain confirmed that receptor dimerization is sufficient for proliferative signaling. Interestingly, while the proliferative effects of both FK1012 and AP1510 were reversible, FK1012-driven proliferation persisted for several days after drug withdrawal. Furthermore, much higher concentrations of FK506 were required to inhibit FK1012-mediated proliferation than were required to inhibit AP1510-mediated proliferation. The persistence of FK1012's effect appeared to be specific to clones expressing c-kit–containing fusion proteins. These results suggest that pharmacologically-responsive fusion proteins containing c-kitmay be useful for specifically and reversibly expanding genetically modified hematopoietic cell populations.

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25

Robaglia, C., B. Menand, Y. Lei, R. Sormani, M. Nicolaï, C. Gery, E. Teoulé, D. Deprost y C. Meyer. "Plant growth: the translational connection". Biochemical Society Transactions 32, n.º 4 (1 de agosto de 2004): 581–84. http://dx.doi.org/10.1042/bst0320581.

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The TOR (target of rapamycin) pathway is a phylogenetically conserved transduction system in eukaryotes linking the energy status of the cell to the protein synthesis apparatus and to cell growth. The TOR protein is specifically inhibited by a rapamycin–FKBP12 complex (where FKBP stands for FK506-binding protein) in yeast and animal cells. Whereas plants appear insensitive to rapamycin, Arabidopsis thaliana harbours a single TOR gene, which is essential for embryonic development. It was found that the product of this gene was capable of binding to rapamycin and yeast FKBP12. In-frame fusion with a GUS reporter gene shows that the TOR protein is produced essentially in proliferating zones, whereas the TOR mRNA can be detected in all organs suggesting a translational regulation of TOR. Phenotypic analysis of Arabidopsis TOR mutants indicates that the plant TOR pathway fulfils the same role in controlling cell growth as its other eukaryotic counterparts.

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26

Yamaguchi, T., A. Kurisaki, N. Yamakawa, K. Minakuchi y H. Sugino. "FKBP12 functions as an adaptor of the Smad7–Smurf1 complex on activin type I receptor". Journal of Molecular Endocrinology 36, n.º 3 (junio de 2006): 569–79. http://dx.doi.org/10.1677/jme.1.01966.

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The cytoplasmic immunophilin FKBP12, a 12 kDa FK506-binding protein, has been shown to act as an inhibitor for transforming growth factor-β (TGF-β) signaling. FKBP12 binds to the glycine- and serine-rich motif (GS motif) of the TGF-β type I receptor, and functions as a secure switch to prevent the leaky signal. Upon stimulation with ligand, FKBP12 is released from the receptor to fully propagate the signal. We found that activin, a member of TGF-β superfamily, also induced the dissociation of FKBP12 from the activin type I receptor (ALK4). However, we observed that the released FKBP12 associates again with the receptor a few hours later. FKBP12 also interacted with another inhibitory molecule of activin signal, Smad7, in an activin-dependent manner, and formed a complex with Smad7 on the type I receptor. FK506, a chemical ligand for FKBP12, which dissociates FKBP12 from the receptor, decreased the interaction between Smad7 and Smad ubiquitin regulatory factor 1 (Smurf1). FK506 also inhibited the ubiquitination of the type I receptor by Smurf1. These findings indicate a new inhibitory function of FKBP12 as an adaptor molecule for the Smad7–Smurf1 complex to regulate the duration of the activin signal.

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27

BULTYNCK, Geert, Patrick DE SMET, Daniela ROSSI, Geert CALLEWAERT, Ludwig MISSIAEN, Vincenzo SORRENTINO, Humbert DE SMEDT y Jan B. PARYS. "Characterization and mapping of the 12kDa FK506-binding protein (FKBP12)-binding site on different isoforms of the ryanodine receptor and of the inositol 1,4,5-trisphosphate receptor". Biochemical Journal 354, n.º 2 (22 de febrero de 2001): 413–22. http://dx.doi.org/10.1042/bj3540413.

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We investigated the interaction of the 12kDa FK506-binding protein (FKBP12) with two ryanodine-receptor isoforms (RyR1 and RyR3) and with two myo-inositol 1,4,5-trisphosphate (IP3) receptor isoforms (IP3R1 and IP3R3). Using glutathione S-transferase (GST)-FKBP12 affinity chromatography, we could efficiently extract RyR1 (42±7% of the solubilized RyR1) from terminal cisternae of skeletal muscle as well as RyR3 (32±4% of the solubilized RyR3) from RyR3-overexpressing HEK-293 cells. These interactions were completely abolished by FK506 (20µM) but were largely unaffected by RyR-channel modulators. In contrast, neither IP3R1 nor IP3R3 from various sources, including rabbit cerebellum, A7r5 smooth-muscle cells and IP3R-overexpressing Sf9 insect cells from Spodoptera frugiperda, were retained on the GST-FKBP12 matrix. Moreover, immunoprecipitation experiments indicated a high-affinity interaction of FKBP12 with RyR1 but not with IP3R1. In order to determine the FKBP12-binding site, we fragmented both RyR1 and IP3R1 by limited proteolysis. We obtained a 45kDa fragment of RyR1 that bound to the GST-FKBP12 matrix, indicating that it retained all requirements for FKBP12 binding. This fragment was identified by its interaction with antibody m34C and must therefore contain its epitope (amino acids 2756–2803). However, no fragment of IP3R1 was retained on the column. These molecular data are in agreement with the lack of correlation between FKBP12 and IP3R1 expression in various cell types. The observation that FKBP12 did not affect IP3-induced Ca2+ release but reduced caffeine-induced Ca2+ release also indicated that mature IP3R1 and IP3R3, in contrast to RyR1 and RyR3, did not display a specific, high-affinity interaction with FKBP12.

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Otto, Kevin G., Liqing Jin, David M. Spencer y C. Anthony Blau. "Cell proliferation through forced engagement of c-Kit and Flt-3". Blood 97, n.º 11 (1 de junio de 2001): 3662–64. http://dx.doi.org/10.1182/blood.v97.11.3662.

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To investigate the potential for functional interactions between heterologous receptors, the cytoplasmic domains of 2 different receptors (c-Kit and Flt-3) were coexpressed in the interleukin-3–dependent cell line Ba/F3. The receptor signaling domains were presented in the context of fusion proteins, with c-Kit linked to the FK506 binding protein (FKBP12) and Flt-3 linked to the FRB domain of the FKBP12–rapamycin-associated protein. The fusions were brought into apposition with the use of chemical inducers of dimerization (CIDs). Two classes of CID were employed. FK1012 and its synthetic analogue AP1510 bring together 2 copies of the FKBP12 domain, thereby inducing homodimerization of the c-KitFKBP12fusion. A second type of CID, rapamycin, brings together one FKBP12 domain and one FRB domain, resulting in heterodimerization of the c-KitFKBP12 and Flt-3FRB fusions. Ba/F3 cell growth was promoted not only by FK1012- or AP1510-induced homodimerization of the c-KitFKBP12 fusion (as reported previously), but also by rapamycin-induced c-KitFKBP12–Flt-3FRB heterodimerization. These findings demonstrate the potential for a direct functional interaction between c-Kit and Flt-3.

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Cunningham, Earlene Brown. "An Inositolphosphate-Binding Immunophilin, IPBP12". Blood 94, n.º 8 (15 de octubre de 1999): 2778–89. http://dx.doi.org/10.1182/blood.v94.8.2778.420k10_2778_2789.

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A novel inositolphosphate-binding protein has been identified and shown to be an immunophilin. This protein, which was isolated from human erythrocyte membranes and from K562 (human erythroleukemia) cell membranes, has robust peptidylprolyl cis-trans isomerase activity that is strongly inhibited by nanomolar concentrations of FK506 or rapamycin, indicating a member of the FKBP (FK506-binding protein) class. However, unlike the cytosolic FKBP12, the isomerase activity of this membrane-associated immunophilin is strongly inhibited by nanomolar concentrations of inositol 1,4,5-trisphosphate (IP3), inositol 1,3,4,5-tetrakisphosphate (IP4), and phosphatidylinositol 4- and 4,5-phosphates, which are suggested to be physiological ligands. The demonstration of a single 12-kD protein that binds both IP4 or IP3and anti-FKBP12 provides strong support for the inositolphosphate-binding immunophilin having an apparent mass of 12 kD, and it is suggested that the protein might be called IPBP12 for 12-kD inositol phosphate binding protein. When an internal tryptic peptide derived from IPBP12 was sequenced, a sequence also present in human cytokeratin 10 was identified, suggesting a cytoskeletal localization for the immunophilin. While purifying IPBP12, it was found that it is immunoprecipitated with specific proteins that include a protein kinase and a phosphoprotein phosphatase. The latter is indicated to be phosphoprotein phosphatase 2A (PP-2A). It is suggested that immunophilins promote the assembly of multiprotein complexes that often include a protein kinase or a phosphoprotein phosphatase or both.

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Mustafi, Sourajit M., Hui Chen, Hongmin Li, David M. LeMaster y Griselda Hernández. "Analysing the visible conformational substates of the FK506-binding protein FKBP12". Biochemical Journal 453, n.º 3 (12 de julio de 2013): 371–80. http://dx.doi.org/10.1042/bj20130276.

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The 1H-15N 2D NMR correlation spectrum of the widely studied FK506-binding protein FKBP12 (FK506-binding protein of 12 kDa) contains previously unreported peak doublings for at least 31 residues that arise from a minor conformational state (12% of total) which exchanges with the major conformation with a time constant of 3.0 s at 43°C. The largest differences in chemical shift occur for the 80′s loop that forms critical recognition interactions with many of the protein partners for the FKBP family. The residues exhibiting doubling extend into the adjacent strands of the β-sheet, across the active site to the α-helix and into the 50′s loop. Each of the seven proline residues adopts a trans-peptide linkage in both the major and minor conformations, indicating that this slow transition is not the result of prolyl isomerization. Many of the residues exhibiting resonance doubling also participate in conformational line-broadening transition(s) that occur ~105-fold more rapidly, proposed previously to arise from a single global process. The 1.70 Å (1 Å=0.1 nm) resolution X-ray structure of the H87V variant is strikingly similar to that of FKBP12, yet this substitution quenches the slow conformational transition throughout the protein while quenching the line-broadening transition for residues near the 80′s loop. Line-broadening was also decreased for the residues in the α-helix and 50′s loop, whereas line-broadening in the 40′s loop was unaffected. The K44V mutation selectively reduces the line-broadening in the 40′s loop, verifying that at least three distinct conformational transitions underlie the line-broadening processes of FKBP12.

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Shigdel, Uddhav K., Seung-Joo Lee, Mathew E. Sowa, Brian R. Bowman, Keith Robison, Minyun Zhou, Khian Hong Pua et al. "Genomic discovery of an evolutionarily programmed modality for small-molecule targeting of an intractable protein surface". Proceedings of the National Academy of Sciences 117, n.º 29 (30 de junio de 2020): 17195–203. http://dx.doi.org/10.1073/pnas.2006560117.

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The vast majority of intracellular protein targets are refractory toward small-molecule therapeutic engagement, and additional therapeutic modalities are needed to overcome this deficiency. Here, the identification and characterization of a natural product, WDB002, reveals a therapeutic modality that dramatically expands the currently accepted limits of druggability. WDB002, in complex with the FK506-binding protein (FKBP12), potently and selectively binds the human centrosomal protein 250 (CEP250), resulting in disruption of CEP250 function in cells. The recognition mode is unprecedented in that the targeted domain of CEP250 is a coiled coil and is topologically featureless, embodying both a structural motif and surface topology previously considered on the extreme limits of “undruggability” for an intracellular target. Structural studies reveal extensive protein–WDB002 and protein–protein contacts, with the latter being distinct from those seen in FKBP12 ternary complexes formed by FK506 and rapamycin. Outward-facing structural changes in a bound small molecule can thus reprogram FKBP12 to engage diverse, otherwise “undruggable” targets. The flat-targeting modality demonstrated here has the potential to expand the druggable target range of small-molecule therapeutics. As CEP250 was recently found to be an interaction partner with the Nsp13 protein of the SARS-CoV-2 virus that causes COVID-19 disease, it is possible that WDB002 or an analog may exert useful antiviral activity through its ability to form high-affinity ternary complexes containing CEP250 and FKBP12.

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Xiao, He, Li-Li Wang, Cui-Ling Shu, Ming Yu, Song Li, Bei-Fen Shen y Yan Li. "Establishment of a Cell Model Based on FKBP12 Dimerization for Screening of FK506-like Neurotrophic Small Molecular Compounds". Journal of Biomolecular Screening 11, n.º 3 (20 de febrero de 2006): 225–35. http://dx.doi.org/10.1177/1087057105285440.

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FK506 is an efficient immunosuppressive agent with an increasing number of clinical applications. It has been approved to prevent rejection in transplant patients and be efficacious in several autoimmune diseases. Its immunosuppressive activity results from binding to receptor proteins designated as immunophilins (i.e., FKBP12, FK506 binding protein). Recent studies have suggested that FK506 can promote neurite outgrowth as a 2nd activity. Furthermore, it has been shown that the neurotrophic property of FK506 is independent of its immunosuppressive action. Although the mechanism of its neurotrophic activity has not yet been well elucidated, FKBP12 is identified as a drug target, and much effort has been directed toward the design of FKBP12-binding molecules, which are neurotrophic but nonimmunosuppressive, for clinical use. In this present study, the authors constructed a stable cell line, which underwent apoptosis upon treatment by AP20187, a wholly synthesized, cell-permeable dimeric FK506 derivative, based on FKBP12-mBax dimerization. This AP20187-mediated apoptosiswas rapidly reversed by the addition of an FKBP12-binding competitormolecule (FK506 or rapamycin), indicating that this cell line might be used to screen FK506 derivatives. Using the screening model, hundreds of synthetic FK506 analogs were analyzed. A promising compound, named N308, was obtained. The results showed that N308 could inhibit AP20187-induced gene-modified target cell apoptosis and elicit augmentation of neurite extension from both cultured PC-12 cells and chicken dorsal root ganglia cultures.

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Brown, Kalyn A., Yan Zou, David Shirvanyants, Jie Zhang, Subhas Samanta, Pavan K. Mantravadi, Nikolay V. Dokholyan y Alexander Deiters. "Light-cleavable rapamycin dimer as an optical trigger for protein dimerization". Chemical Communications 51, n.º 26 (2015): 5702–5. http://dx.doi.org/10.1039/c4cc09442e.

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Corona, Benjamin T., Clement Rouviere, Susan L. Hamilton y Christopher P. Ingalls. "FKBP12 deficiency reduces strength deficits after eccentric contraction-induced muscle injury". Journal of Applied Physiology 105, n.º 2 (agosto de 2008): 527–37. http://dx.doi.org/10.1152/japplphysiol.01145.2007.

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Strength deficits associated with eccentric contraction-induced muscle injury stem, in part, from excitation-contraction uncoupling. FKBP12 is a 12-kDa binding protein known to bind to the skeletal muscle sarcoplasmic reticulum Ca2+ release channel [ryanodine receptor (RyR1)] and plays an important role in excitation-contraction coupling. To assess the effects of FKBP12 deficiency on muscle injury and recovery, we measured anterior crural muscle (tibialis anterior and extensor digitorum longus muscles) strength in skeletal muscle-specific FKBP12-deficient and wild-type (WT) mice before and after a single bout of 150 eccentric contractions, as well as before and after the performance of six injury bouts. Histological damage of the tibialis anterior muscle was assessed after injury. Body weight and peak isometric and eccentric torques were lower in FKBP12-deficient mice compared with WT mice. There were no differences between FKBP12-deficient and WT mice in preinjury peak isometric and eccentric torques when normalized to body weight, and no differences in the relative decreases in eccentric torque with a single or multiple injury bouts. After a single injury bout, FKBP12-deficient mice had less initial strength deficits and recovered faster (especially females) than WT mice, despite no differences in the degree of histological damage. After multiple injury bouts, FKBP12-deficient mice recovered muscle strength faster than WT mice and exhibited significantly less histological muscle damage than WT mice. In summary, FKBP12 deficiency results in less initial strength deficits and enhanced recovery from single (especially females) and repeated bouts of injury than WT mice.

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Bossard, M. J., D. J. Bergsma, M. Brandt, G. P. Livi, W. K. Eng, R. K. Johnson y M. A. Levy. "Catalytic and ligand binding properties of the FK506 binding protein FKBP12: effects of the single amino acid substitution of Tyr82 to Leu". Biochemical Journal 297, n.º 2 (15 de enero de 1994): 365–72. http://dx.doi.org/10.1042/bj2970365.

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The binding of FK506 and rapamycin to their cytosolic receptor FKBP12 is an intermediate step in the paths leading to their potent immunosuppressive properties. One of the amino acids defining the hydrophobic binding cleft for the macrocycles is Tyr82, which is thought to form a hydrogen bond with the amide oxygens of the common pipecolyl structural element within the two macrolides. To understand better the influence of this amino acid residue in catalytic activity (cis-trans peptidyl prolyl isomerization) and ligand binding properties, a Tyr82 to Leu site-specific modification of FKBP12 was prepared, purified and characterized. Kinetic experiments have demonstrated that the Tyr82 to Leu modification has a greater effect on catalytic properties than on ligand binding affinities, a result which indicates that these inhibitors may not be binding as true transition-state analogues. In an additional test for cellular function, expression of both wild-type and mutant human FKBP12 in a strain of Saccharomyces cerevisiae rendered resistant to rapamycin by deletion of the gene encoding a cytosolic rapamycin binding protein (RPB1), the yeast homologue of FKBP12, restored wild-type drug sensitivity.

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Chambraud, Béatrice, Christine Radanyi, Jacques H. Camonis, Kamran Shazand, Krzysztof Rajkowski y Etienne-Emile Baulieu. "FAP48, a New Protein That Forms Specific Complexes with Both Immunophilins FKBP59 and FKBP12". Journal of Biological Chemistry 271, n.º 51 (20 de diciembre de 1996): 32923–29. http://dx.doi.org/10.1074/jbc.271.51.32923.

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Vilella-Bach, Montserrat, Paul Nuzzi, Yimin Fang y Jie Chen. "The FKBP12-Rapamycin-binding Domain Is Required for FKBP12-Rapamycin-associated Protein Kinase Activity and G1Progression". Journal of Biological Chemistry 274, n.º 7 (12 de febrero de 1999): 4266–72. http://dx.doi.org/10.1074/jbc.274.7.4266.

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Geisler, Markus, H. Üner Kolukisaoglu, Rodolphe Bouchard, Karla Billion, Joachim Berger, Beate Saal, Nathalie Frangne et al. "TWISTED DWARF1, a Unique Plasma Membrane-anchored Immunophilin-like Protein, Interacts with Arabidopsis Multidrug Resistance-like Transporters AtPGP1 and AtPGP19". Molecular Biology of the Cell 14, n.º 10 (octubre de 2003): 4238–49. http://dx.doi.org/10.1091/mbc.e02-10-0698.

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Null-mutations of the Arabidopsis FKBP-like immunophilin TWISTED DWARF1 (TWD1) gene cause a pleiotropic phenotype characterized by reduction of cell elongation and disorientated growth of all plant organs. Heterologously expressed TWD1 does not exhibit cis-trans-peptidylprolyl isomerase (PPIase) activity and does not complement yeast FKBP12 mutants, suggesting that TWD1 acts indirectly via protein-protein interaction. Yeast two-hybrid protein interaction screens with TWD1 identified cDNA sequences that encode the C-terminal domain of Arabidopsis multidrugresistance-like ABC transporter AtPGP1. This interaction was verified in vitro. Mapping of protein interaction domains shows that AtPGP1 surprisingly binds to the N-terminus of TWD1 harboring the cis-trans peptidyl-prolyl isomerase-like domain and not to the tetratrico-peptide repeat domain, which has been shown to mediate protein-protein interaction. Unlike all other FKBPs, TWD1 is shown to be an integral membrane protein that colocalizes with its interacting partner AtPGP1 on the plasma membrane. TWD1 also interacts with AtPGP19 (AtMDR1), the closest homologue of AtPGP1. The single gene mutation twd1-1 and double atpgp1-1/atpgp19-1 (atmdr1-1) mutants exhibit similar phenotypes including epinastic growth, reduced inflorescence size, and reduced polar auxin transport, suggesting that a functional TWD1-AtPGP1/AtPGP19 complex is required for proper plant development.

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39

Cafferkey, R., P. R. Young, M. M. McLaughlin, D. J. Bergsma, Y. Koltin, G. M. Sathe, L. Faucette, W. K. Eng, R. K. Johnson y G. P. Livi. "Dominant missense mutations in a novel yeast protein related to mammalian phosphatidylinositol 3-kinase and VPS34 abrogate rapamycin cytotoxicity". Molecular and Cellular Biology 13, n.º 10 (octubre de 1993): 6012–23. http://dx.doi.org/10.1128/mcb.13.10.6012-6023.1993.

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Rapamycin is a macrolide antifungal agent that exhibits potent immunosuppressive properties. In Saccharomyces cerevisiae, rapamycin sensitivity is mediated by a specific cytoplasmic receptor which is a homolog of human FKBP12 (hFKBP12). Deletion of the gene for yeast FKBP12 (RBP1) results in recessive drug resistance, and expression of hFKBP12 restores rapamycin sensitivity. These data support the idea that FKBP12 and rapamycin form a toxic complex that corrupts the function of other cellular proteins. To identify such proteins, we isolated dominant rapamycin-resistant mutants both in wild-type haploid and diploid cells and in haploid rbp1::URA3 cells engineered to express hFKBP12. Genetic analysis indicated that the dominant mutations are nonallelic to mutations in RBP1 and define two genes, designated DRR1 and DRR2 (for dominant rapamycin resistance). Mutant copies of DRR1 and DRR2 were cloned from genomic YCp50 libraries by their ability to confer drug resistance in wild-type cells. DNA sequence analysis of a mutant drr1 allele revealed a long open reading frame predicting a novel 2470-amino-acid protein with several motifs suggesting an involvement in intracellular signal transduction, including a leucine zipper near the N terminus, two putative DNA-binding sequences, and a domain that exhibits significant sequence similarity to the 110-kDa catalytic subunit of both yeast (VPS34) and bovine phosphatidylinositol 3-kinases. Genomic disruption of DRR1 in a mutant haploid strain restored drug sensitivity and demonstrated that the gene encodes a nonessential function. DNA sequence comparison of seven independent drr1dom alleles identified single base pair substitutions in the same codon within the phosphatidylinositol 3-kinase domain, resulting in a change of Ser-1972 to Arg or Asn. We conclude either that DRR1 (alone or in combination with DRR2) acts as a target of FKBP12-rapamycin complexes or that a missense mutation in DRR1 allows it to compensate for the function of the normal drug target.

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40

Cafferkey, R., P. R. Young, M. M. McLaughlin, D. J. Bergsma, Y. Koltin, G. M. Sathe, L. Faucette, W. K. Eng, R. K. Johnson y G. P. Livi. "Dominant missense mutations in a novel yeast protein related to mammalian phosphatidylinositol 3-kinase and VPS34 abrogate rapamycin cytotoxicity." Molecular and Cellular Biology 13, n.º 10 (octubre de 1993): 6012–23. http://dx.doi.org/10.1128/mcb.13.10.6012.

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Rapamycin is a macrolide antifungal agent that exhibits potent immunosuppressive properties. In Saccharomyces cerevisiae, rapamycin sensitivity is mediated by a specific cytoplasmic receptor which is a homolog of human FKBP12 (hFKBP12). Deletion of the gene for yeast FKBP12 (RBP1) results in recessive drug resistance, and expression of hFKBP12 restores rapamycin sensitivity. These data support the idea that FKBP12 and rapamycin form a toxic complex that corrupts the function of other cellular proteins. To identify such proteins, we isolated dominant rapamycin-resistant mutants both in wild-type haploid and diploid cells and in haploid rbp1::URA3 cells engineered to express hFKBP12. Genetic analysis indicated that the dominant mutations are nonallelic to mutations in RBP1 and define two genes, designated DRR1 and DRR2 (for dominant rapamycin resistance). Mutant copies of DRR1 and DRR2 were cloned from genomic YCp50 libraries by their ability to confer drug resistance in wild-type cells. DNA sequence analysis of a mutant drr1 allele revealed a long open reading frame predicting a novel 2470-amino-acid protein with several motifs suggesting an involvement in intracellular signal transduction, including a leucine zipper near the N terminus, two putative DNA-binding sequences, and a domain that exhibits significant sequence similarity to the 110-kDa catalytic subunit of both yeast (VPS34) and bovine phosphatidylinositol 3-kinases. Genomic disruption of DRR1 in a mutant haploid strain restored drug sensitivity and demonstrated that the gene encodes a nonessential function. DNA sequence comparison of seven independent drr1dom alleles identified single base pair substitutions in the same codon within the phosphatidylinositol 3-kinase domain, resulting in a change of Ser-1972 to Arg or Asn. We conclude either that DRR1 (alone or in combination with DRR2) acts as a target of FKBP12-rapamycin complexes or that a missense mutation in DRR1 allows it to compensate for the function of the normal drug target.

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41

HE, GANG, JUYING SHI, YANTAO CHEN, YI CHEN, QIANLING ZHANG, MINGLIANG WANG y JIANHONG LIU. "RANK-ORDERING THE BINDING AFFINITY FOR FKBP12 AND H1N1 NEURAMINIDASE INHIBITORS IN THE COMBINATION OF A PROTEIN MODEL WITH DENSITY FUNCTIONAL THEORY". Journal of Theoretical and Computational Chemistry 10, n.º 04 (agosto de 2011): 541–65. http://dx.doi.org/10.1142/s0219633611006633.

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The quantum mechanical interaction energies between FKBP12 as well as H1N1 neuraminidase and their inhibitors were directly calculated with an efficient density functional theory by mimicking the whole protein with a protein model composed of the amino acids surrounding the ligands. It was found that the calculated quantum mechanical interaction energies correlate well with the experimental binding free energies with the correlation coefficients of 0.88, 0.86, and the standard deviation of 0.93 and 1.00 kcal/mol, respectively. To compare with force field approach, the binding free energies with the correlation coefficient R = 0.80 and 0.47 were estimated by AutoDock 4.0 programs. It was indicated that the quantum interaction energy shows a better performance in rank-ordering the binding affinity between FKBP12 and H1N1 neuraminidase inhibitors than those of AutoDock 4.0 program. In combination protein model with density functional theory, the estimated quantum interaction energy could be a good predictor or scoring function in structure-based computer-aided drug design. Finally, five new FKBP12 inhibitors were designed based on calculated quantum mechanical interaction energy. In particular, the theoretical K i value of one compound is as low as 0.05 nM, nearly 8-fold more active than FK506.

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42

Yang, Huan, Yuping Zhou, Benjiamin Edelshain, Frederick Schatz, Charles J. Lockwood y Hugh S. Taylor. "FKBP4 is regulated by HOXA10 during decidualization and in endometriosis". REPRODUCTION 143, n.º 4 (abril de 2012): 531–38. http://dx.doi.org/10.1530/rep-11-0438.

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FKBP4 (FKBP52) and FKBP5 (FKBP51) are progestin receptor (PR) co-chaperone proteins that enhance and inhibit, respectively, progestin-mediated transcription by PR. Here, we examinedFKBP4andFKBP5expression in the eutopic endometrium of fertile women with endometriosis and effects of FKBP4 and FKBP5 on the decidualization of human endometrial stromal cells (HESCs), and assessed HOXA10 regulation of FKBP4. Expression ofFKBP4mRNA was increased in the late proliferative phase and remained elevated throughout the secretory phase.FKBP5expression was low and remained constant throughout the menstrual cycle. Compared with controls,FKBP4mRNA expression was decreased in the endometrium of women with endometriosis, whereas no significant endometriosis-related change was seen forFKBP5. Cultured HESCs were treated with eitherFKBP4orFKBP5siRNA and then decidualized by incubation with progesterone (P4) and 8-bromoadenosine cAMP. Treatment of HESCs withFKBP4siRNA resulted in 60% lowerIGFBP1expression. In contrast, incubation withFKBP5siRNA did not significantly decreaseIGFBP1expression duringin vitrodecidualization.HOXA10andFKBP4expression increased in parallel duringin vitrodecidualization. In HESCs, overexpressed HOXA10 enhanced FKBP4 mRNA and protein levels, whereas HOXA10 knockdown decreased FKBP4 mRNA and protein levels compared with controls. Similarly, duringin vitrodecidualization,FKBP4expression was decreased in HOXA10-silenced cells. EnhancedHOXA10expression in HESCs elicits a decidualization mediating increase inFKBP4expression. The findings are consistent with the observation that women with endometriosis have diminishedFKBP4expression leading to impaired decidualization and infertility. The P4resistance seen in endometriosis may be mediated through HOXA10-regulatedFKBP4expression.

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43

Singh, Vikramjeet, Amita Nand, Caixia Chen, ZhiPeng Li, Sheng-Jie Li, Songbai Wang, Mo Yang, Alejandro Merino, Lixin Zhang y Jingsong Zhu. "Echinomycin, a Potential Binder of FKBP12, Shows Minor Effect on Calcineurin Activity". Journal of Biomolecular Screening 19, n.º 9 (1 de agosto de 2014): 1275–81. http://dx.doi.org/10.1177/1087057114544742.

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Echinomycin, a member of the quinoxaline family of antibiotics, is known to be a small-molecule inhibitor of hypoxia inducible factor–1 (HIF-1) DNA binding activity. Recently, it has been shown to suppress mammalian target of rapamycin (mTOR) signaling and growth in leukemia cell lines. In this study, we investigated whether echinomycin interacts with the FKBP12 protein. Molecular docking was used, and the predicted binding energy was −10.61 kcal/mol. Moreover, surface plasmon resonance imaging and fluorescence quenching techniques were used to validate this interaction. Echinomycin binds to FKBP12 with a strong binding affinity comparable with rapamycin. Furthermore, the echinomycin-FKBP12 complex has been shown to affect calcineurin activity when tested in a calcineurin phosphatase inhibition assay. All of these studies have shown that echinomycin may have a double impact on HIF signaling by direct inhibition and through mTOR.

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44

Harris, Diondra C., Yenni A. Garcia, Cheryl Storer Samaniego, Veronica W. Rowlett, Nina R. Ortiz, Ashley N. Payan, Tatsuya Maehigashi y Marc B. Cox. "Functional Comparison of Human and Zebra Fish FKBP52 Confirms the Importance of the Proline-Rich Loop for Regulation of Steroid Hormone Receptor Activity". International Journal of Molecular Sciences 20, n.º 21 (28 de octubre de 2019): 5346. http://dx.doi.org/10.3390/ijms20215346.

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Previous studies demonstrated that the 52-kDa FK506-binding protein (FKBP52) proline-rich loop is functionally relevant in the regulation of steroid hormone receptor activity. While zebra fish (Danio rerio; Dr) FKBP52 contains all of the analogous domains and residues previously identified as critical for FKBP52 potentiation of receptor activity, it fails to potentiate activity. Thus, we used a cross-species comparative approach to assess the residues that are functionally critical for FKBP52 function. Random selection of gain-of-function DrFKBP52 mutants in Saccharomyces cerevisiae identified two critical residues, alanine 111 (A111) and threonine 157 (T157), for activation of receptor potentiation by DrFKBP52. In silico homology modeling suggests that alanine to valine substitution at position 111 in DrFKBP52 induces an open conformation of the proline-rich loop surface similar to that observed on human FKBP52, which may allow for sufficient surface area and increased hydrophobicity for interactions within the receptor–chaperone complex. A second mutation in the FKBP12-like domain 2 (FK2), threonine 157 to arginine (T157R), also enhanced potentiation, and the DrFKBP52-A111V/T157R double mutant potentiated receptor activity similar to human FKBP52. Collectively, these results confirm the functional importance of the FKBP52 proline-rich loop, suggest that an open conformation on the proline-rich loop surface is a predictor of activity, and highlight the importance of an additional residue within the FK2 domain.

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45

Cruz, M. Cristina, Alan L. Goldstein, Jill Blankenship, Maurizio Del Poeta, John R. Perfect, John H. McCusker, Youssef L. Bennani, Maria E. Cardenas y Joseph Heitman. "Rapamycin and Less Immunosuppressive Analogs Are Toxic to Candida albicans and Cryptococcus neoformans via FKBP12-Dependent Inhibition of TOR". Antimicrobial Agents and Chemotherapy 45, n.º 11 (1 de noviembre de 2001): 3162–70. http://dx.doi.org/10.1128/aac.45.11.3162-3170.2001.

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ABSTRACT Candida albicans and Cryptococcus neoformans cause both superficial and disseminated infections in humans. Current antifungal therapies for deep-seated infections are limited to amphotericin B, flucytosine, and azoles. A limitation is that commonly used azoles are fungistatic in vitro and in vivo. Our studies address the mechanisms of antifungal activity of the immunosuppressive drug rapamycin (sirolimus) and its analogs with decreased immunosuppressive activity. C. albicans rbp1/rbp1 mutant strains lacking a homolog of the FK506-rapamycin target protein FKBP12 were found to be viable and resistant to rapamycin and its analogs. Rapamycin and analogs promoted FKBP12 binding to the wild-type Tor1 kinase but not to a rapamycin-resistant Tor1 mutant kinase (S1972R). FKBP12 and TOR mutations conferred resistance to rapamycin and its analogs inC. albicans, C. neoformans, andSaccharomyces cerevisiae. Our findings demonstrate the antifungal activity of rapamycin and rapamycin analogs is mediated via conserved complexes with FKBP12 and Tor kinase homologs in divergent yeasts. Taken together with our observations that rapamycin and its analogs are fungicidal and that spontaneous drug resistance occurs at a low rate, these mechanistic findings support continued investigation of rapamycin analogs as novel antifungal agents.

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46

Neye, Holger. "Mutation of FKBP associated protein 48 (FAP48) at proline 219 disrupts the interaction with FKBP12 and FKBP52". Regulatory Peptides 97, n.º 2-3 (marzo de 2001): 147–52. http://dx.doi.org/10.1016/s0167-0115(00)00206-8.

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47

Brasseur, Anaïs, Brice Rotureau, Marjorie Vermeersch, Thierry Blisnick, Didier Salmon, Philippe Bastin, Etienne Pays, Luc Vanhamme y David Pérez-Morga. "Trypanosoma brucei FKBP12 Differentially Controls Motility and Cytokinesis in Procyclic and Bloodstream Forms". Eukaryotic Cell 12, n.º 2 (26 de octubre de 2012): 168–81. http://dx.doi.org/10.1128/ec.00077-12.

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ABSTRACT FKBP12 proteins are able to inhibit TOR kinases or calcineurin phosphatases upon binding of rapamycin or FK506 drugs, respectively. The Trypanosoma brucei FKBP12 homologue (TbFKBP12) was found to be a cytoskeleton-associated protein with specific localization in the flagellar pocket area of the bloodstream form. In the insect procyclic form, RNA interference-mediated knockdown of TbFKBP12 affected motility. In bloodstream cells, depletion of TbFKBP12 affected cytokinesis and cytoskeleton architecture. These last effects were associated with the presence of internal translucent cavities limited by an inside-out configuration of the normal cell surface, with a luminal variant surface glycoprotein coat lined up by microtubules. These cavities, which recreated the streamlined shape of the normal trypanosome cytoskeleton, might represent unsuccessful attempts for cell abscission. We propose that TbFKBP12 differentially affects stage-specific processes through association with the cytoskeleton.

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48

Brooksbank, Richard L., Margaret E. Badenhorts, Hyam Isaacs y Nerina Savage. "Treatment of Normal Skeletal Muscle with FK506 or Rapamycin Results in Halothane-induced Muscle Contracture". Anesthesiology 89, n.º 3 (1 de septiembre de 1998): 693–98. http://dx.doi.org/10.1097/00000542-199809000-00020.

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Background FKBP12 is a protein that is closely associated with the ryanodine receptor type 1 of skeletal muscle and modulates Ca2+ release by the channel. The immunosuppressants FK506 and rapamycin both bind to FKBP12 and in turn dissociate the protein from the ryanodine receptor. By treating healthy human skeletal muscle strips with FK506 or rapamycin and then subjecting the strips to the caffeine-halothane contracture test, this study determined that FK506 and rapamycin alter the sensitivity of the muscle strip to halothane, caffeine, or both. Methods Skeletal muscle strips from 10 healthy persons were incubated in Krebs medium equilibrated with a 95% oxygen and 5% carbon dioxide mixture, which contained either 12 microM FK506 (n = 8) or 12 microM rapamycin (n = 6), for 15 min at 37 degrees C. The strips were subjected to the caffeine-halothane contracture test for malignant hyperthermia according to the European Malignant Hyperthermia Group protocol. Results Treatment of normal skeletal muscle strips with FK506 and rapamycin resulted in halothane-induced contractures of 0.44+/-0.16 g and 0.6+/-0.49 g, respectively, at 2% halothane. Conclusions The results obtained show that pre-exposure of healthy skeletal muscle strips to either FK506 or rapamycin is sufficient to give rise to halothane-induced contractures. This is most likely caused by destabilization of Ca2+ release by the ryanodine receptor as a result of the dissociation of FKBP12. This finding suggests that a mutation in FKBP12 or changes in its capacity to bind to the ryanodine receptor could alter the halothane sensitivity of the skeletal muscle ryanodine receptor and thereby predispose the person to malignant hyperthermia.

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49

Wang, Yong-Xiao, Yun-Min Zheng, Qi-Bing Mei, Qinq-Song Wang, Mei Lin Collier, Sidney Fleischer, Hong-Bo Xin y Michael I. Kotlikoff. "FKBP12.6 and cADPR regulation of Ca2+ release in smooth muscle cells". American Journal of Physiology-Cell Physiology 286, n.º 3 (marzo de 2004): C538—C546. http://dx.doi.org/10.1152/ajpcell.00106.2003.

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Intracellular Ca2+ release through ryanodine receptors (RyRs) plays important roles in smooth muscle excitation-contraction coupling, but the underlying regulatory mechanisms are poorly understood. Here we show that FK506 binding protein of 12.6 kDa (FKBP12.6) associates with and regulates type 2 RyRs (RyR2) in tracheal smooth muscle. FKBP12.6 binds to RyR2 but not other RyR or inositol 1,4,5-trisphosphate receptors, and FKBP12, known to bind to and modulate skeletal RyRs, does not associate with RyR2. When dialyzed into tracheal myocytes, cyclic ADP-ribose (cADPR) alters spontaneous Ca2+ release at lower concentrations and produces macroscopic Ca2+ release at higher concentrations; neurotransmitter-evoked Ca2+ release is also augmented by cADPR. These actions are mediated through FKBP12.6 because they are inhibited by molar excess of recombinant FKBP12.6 and are not observed in myocytes from FKBP12.6-knockout mice. We also report that force development in FKBP12.6-null mice, observed as a decrease in the concentration/tension relationship of isolated trachealis segments, is impaired. Taken together, these findings point to an important role of the FKBP12.6/RyR2 complex in stochastic (spontaneous) and receptor-mediated Ca2+ release in smooth muscle.

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50

Nerattini, Francesca, Riccardo Chelli y Piero Procacci. "II. Dissociation free energies in drug–receptor systems via nonequilibrium alchemical simulations: application to the FK506-related immunophilin ligands". Physical Chemistry Chemical Physics 18, n.º 22 (2016): 15005–18. http://dx.doi.org/10.1039/c5cp05521k.

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The fast switch double annihilation method (FS-DAM) provides an effective mean to the compute the binding free energies in drug-receptor systems. Here we present an application to the FK506-related ligands of the FKBP12 protein.

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