Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50502 (Hip)
 7,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A variety of regulatory proteins, including different classes of transcription factors and protein kinases, have been identified in complexes with Hsp90. On careful examination of unactivated progesterone receptor complexes, eight different protein participants have been identified, and each can be considered a component of the cytoplasmic molecular chaperone machinery. These proteins are Hsp90, Hsp70, Hip, p60, p23, FKBP51, FKBP52 and Cyp40. Studies in a cell-free assembly system have helped to define a highly ordered, dynamic pathway for assembly of progesterone receptor complexes. In the present study, target proteins other than progesterone receptor were used in this cell-free system to assemble complexes in vitro and to compare the composition of resulting complexes. Targets used were human estrogen receptor, human Fes protein-tyrosine kinase, human heat shock transcription factor Hsf1, and human aryl hydrocarbon receptor. The striking similarity of resulting target complexes with previously characterized progesterone receptor complexes suggest that each of these targets undergoes a common assembly pathway involving multiple chaperone components in addition to Hsp90.
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PMID:A pathway of multi-chaperone interactions common to diverse regulatory proteins: estrogen receptor, Fes tyrosine kinase, heat shock transcription factor Hsf1, and the aryl hydrocarbon receptor. 922 9

The progesterone receptor can be reconstituted into hsp90-containing complexes in vitro, and the resulting complexes are needed to maintain hormone binding activity. This process requires ATP/Mg2+, K+, and several axillary proteins. We have developed a defined system for the assembly of progesterone receptor complexes using purified proteins. Five proteins are needed to form complexes that are capable of maintaining hormone binding activity. These include hsp70 and its co-chaperone, hsp40, the hsp70/hsp90-binding protein, Hop, hsp90, and the hsp90-binding protein, p23. The proteins Hip and FKBP52 were not required for this in vitro process even though they have been observed in receptor complexes. Each of the five proteins showed a characteristic concentration dependence. Similar concentrations of hsp70, hsp90, and p23 were needed for optimal assembly, but hsp40 and Hop were effective at about 1/10 the concentration of the other proteins, suggesting that these two proteins act catalytically or are needed at levels similar to the receptor concentration. ATP was required for the functioning of both hsp70 and hsp90. The binding of hsp70 to the receptor requires hsp40 and about 10 microM ATP; however, hsp90 binding appears to occur subsequent to hsp70 binding and is optimal with 1 mM ATP. A three-step model is presented to describe the assembly process.
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PMID:The assembly of progesterone receptor-hsp90 complexes using purified proteins. 983 49

Rapid and transient activation of heat shock genes in response to stress is mediated in eukaryotes by the heat shock transcription factor HSF1. It is well established that cells maintain a dynamic equilibrium between inactive HSF1 monomers and transcriptionally active trimers, but little is known about the mechanism linking HSF1 to reception of various stress stimuli or the factors controlling oligomerization. Recent reports have revealed that HSP90 regulates key steps in the HSF1 activation-deactivation process. Here, we tested the hypothesis that components of the HSP90 chaperone machine, known to function in the folding and maturation of steroid receptors, might also participate in HSF1 regulation. Mobility supershift assays using antibodies against chaperone components demonstrate that active HSF1 trimers exist in a heterocomplex with HSP90, p23, and FKBP52. Functional in vivo experiments in Xenopus oocytes indicate that components of the HSF1 heterocomplex, as well as other components of the HSP90 cochaperone machine, are involved in regulating oligomeric transitions. Elevation of the cellular levels of cochaperones affected the time of HSF1 deactivation during recovery: attenuation was delayed by immunophilins, and accelerated by HSP90, Hsp/c70, Hip, or Hop. In immunotargeting experiments with microinjected antibodies, disruption of HSP90, Hip, Hop, p23, FKBP51, and FKBP52 delayed attenuation. In addition, HSF1 was activated under nonstress conditions after immunotargeting of HSP90 and p23, evidence that these proteins remain associated with HSF1 monomers and function in their repression in vivo. The remarkable similarity of HSF1 complex chaperones identified here (HSP90, p23, and FKBP52) and components in mature steroid receptor complexes suggests that HSF1 oligomerization is regulated by a foldosome-type mechanism similar to steroid receptor pathways. The current evidence leads us to propose a model in which HSF1, HSP90 and p23 comprise a core heterocomplex required for rapid conformational switching through interaction with a dynamic series of HSP90 subcomplexes.
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PMID:Multiple components of the HSP90 chaperone complex function in regulation of heat shock factor 1 In vivo. 1056 29

Like other nuclear receptors, steroid hormone receptors form large protein hetero-complexes in their inactive, ligand-friendly state. Several heat-shock proteins, immunophilins and others have been identified as members of these highly dynamic complexes. The interaction kinetics and dynamics of hsp90, hsp70, p60 (Hop), FKBP52, FKBP51, p48 (Hip) and p23 have been assessed by a biosensor approach measuring the complex formation in real time. A core chaperone complex has been reconstituted from p60, hsp90 and hsp70. p60 forms a molecular bridge between hsp90 and hsp70 with an affinity in the range of 10(5) M(-1). Dynamics of hsp90-p60 complex formation is modulated by ATP through changes in the co-operativity of interaction. At low protein concentrations ATP stabilizes the complex. Binding of p23 to hsp90 did not change the affinity of the hsp90-p60 complex and the stabilizing effect of ATP. Saturation of the p48-hsp70 interaction could not be achieved, suggesting multiple binding sites. A picture of the protein complex, including stoichiometric coefficients, co-operativity of interaction and equilibrium-binding constants, has been formed.
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PMID:Quantitative assessment of complex formation of nuclear-receptor accessory proteins. 1064 22

Heat shock protein 90 (Hsp90) is a molecular chaperone involved in the folding and assembly of a limited set of "client" proteins, many of which are involved in signal transduction pathways. In vivo, it is found in complex with additional proteins, including the chaperones Hsp70, Hsp40, Hip and Hop (Hsp-interacting and Hsp-organising proteins, respectively), as well as high molecular mass immunophilins, such as FKBP59, and the small acidic protein p23. The role of these proteins in Hsp90-mediated assembly processes is poorly understood. It is known that ATP binding and hydrolysis are essential for Hsp90 function in vivo and in vitro. Here we show, for the first time, that human Hsp90 has ATPase activity in vitro. The ATPase activity is characterised using a sensitive assay based on a chemically modified form of the phosphate-binding protein from Escherichia coli. Human Hsp90 is a very weak ATPase, its activity is significantly lower than that of the yeast homologue, and it has a half-life of ATP hydrolysis of eight minutes at 37 degrees C. Using a physiological substrate of Hsp90, the ligand-binding domain of the glucocorticoid receptor, we show that this "client" protein can stimulate the ATPase activity up to 200-fold. This effect is highly specific and unfolded or partially folded proteins, which are known to bind to Hsp90, do not affect the ATPase activity. In addition, the peroxisome proliferator-activated receptor, which is related in both sequence and structure to the glucocorticoid receptor but which does not bind Hsp90, has no observable effect on the ATPase activity. We establish the effect of the co-chaperones Hop, FKBP59 and p23 on the basal ATPase activity as well as the client protein-stimulated ATPase activity of human Hsp90. In contrast with the yeast system, human Hop has little effect on the basal rate of ATP hydrolysis but significantly inhibits the client-protein stimulated rate. Similarly, FKBP59 has little effect on the basal rate but stimulates the client-protein stimulated rate further. In contrast, p23 inhibits both the basal and stimulated rates of ATP hydrolysis. Our results show that the ATPase activity of human Hsp90 is highly regulated by both client protein and co-chaperone binding. We suggest that the rate of ATP hydrolysis is critical to the mode of action of Hsp90, consistent with results that have shown that both over and under-active ATPase mutants of yeast Hsp90 have impaired function in vivo. We suggest that the tight regulation of the ATPase activity of Hsp90 is important and allows the client protein to remain bound to Hsp90 for sufficient time for activation to occur.
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PMID:Stimulation of the weak ATPase activity of human hsp90 by a client protein. 1181 47

The high-affinity ligand-binding form of unactivated steroid receptors exists as a multicomponent complex that includes heat shock protein (Hsp)90; one of the immunophilins cyclophilin 40 (CyP40), FKBP51, or FKBP52; and an additional p23 protein component. Assembly of this heterocomplex is mediated by Hsp70 in association with accessory chaperones Hsp40, Hip, and Hop. A conserved structural element incorporating a tetratricopeptide repeat (TPR) domain mediates the interaction of the immunophilins with Hsp90 by accommodating the C-terminal EEVD peptide of the chaperone through a network of electrostatic and hydrophobic interactions. TPR cochaperones recognize the EEVD structural motif common to both Hsp90 and Hsp70 through a highly conserved clamp domain. In the present study, we investigated in vitro the molecular interactions between CyP40 and FKBP52 and other stress-related components involved in steroid receptor assembly, namely Hsp70 and Hop. Using a binding protein-retention assay with CyP40 fused to glutathione S-transferase immobilized on glutathione-agarose, we have identified the constitutively expressed form of Hsp70, heat shock cognate (Hsc)70, as an additional target for CyP40. Deletion mapping studies showed the binding determinants to be similar to those for CyP40-Hsp90 interaction. Furthermore, a mutational analysis of CyP40 clamp domain residues confirmed the importance of this motif in CyP40-Hsc70 interaction. Additional residues thought to mediate binding specificity through hydrophobic interactions were also important for Hsc70 recognition. CyP40 was shown to have a preference for Hsp90 over Hsc70. Surprisingly, FKBP52 was unable to compete with CyP40 for Hsc70 binding, suggesting that FKBP52 discriminates between the TPR cochaperone-binding sites in Hsp90 and Hsp70. Hop, which contains multiple units of the TPR motif, was shown to be a direct competitor with CyP40 for Hsc70 binding. Similar to Hop, CyP40 was shown not to influence the adenosine triphosphatase activity of Hsc70. Our results suggest that CyP40 may have a modulating role in Hsc70 as well as Hsp90 cellular function.
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PMID:Interaction of the Hsp90 cochaperone cyclophilin 40 with Hsc70. 1549 3

The U-box E3 ubiquitin ligase CHIP (C terminus of Hsc70-interacting protein) binds Hsp90 and/or Hsp70 via its tetratricopeptide repeat (TPR), facilitating ubiquitination of the chaperone-bound client proteins. Mechanisms that regulate the activity of CHIP are, at present, poorly understood. We previously reported that Ca(2+)/S100 proteins directly associate with the TPR proteins, such as Hsp70/Hsp90-organizing protein (Hop), kinesin light chain, Tom70, FKBP52, CyP40, and protein phosphatase 5 (PP5), leading to the dissociation of the interactions of the TPR proteins with their target proteins. Therefore, we have hypothesized that Ca(2+)/S100 proteins can interact with CHIP and regulate its function. GST pulldown assays indicated that Ca(2+)/S100A2 and S100P bind to the TPR domain and lead to interference with the interactions of CHIP with Hsp70, Hsp90, HSF1, and Smad1. In vitro ubiquitination assays indicated that Ca(2+)/S100A2 and S100P are efficient and specific inhibitors of CHIP-mediated ubiquitination of Hsp70, Hsp90, HSF1, and Smad1. Overexpression of S100A2 and S100P suppressed CHIP-chaperone complex-dependent mutant p53 ubiquitination and degradation in Hep3B cells. The association of the S100 proteins with CHIP provides a Ca(2+)-dependent regulatory mechanism for the ubiquitination and degradation of intracellular proteins by the CHIP-proteasome pathway.
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PMID:Ca2+/S100 proteins act as upstream regulators of the chaperone-associated ubiquitin ligase CHIP (C terminus of Hsc70-interacting protein). 2334 57

FKBP38 (FK506-binding protein 38), a membrane-anchored TPR (tetratricopeptide repeat)-containing immunophilin, regulates signalling pathways such as cell survival, apoptosis, proliferation and metastasis. However, the mechanisms that regulate the activity of FKBP38 are, at present, poorly understood. We previously reported that Ca2+/S100 proteins directly associate with the TPR proteins, such as Hop [Hsp70 (heat-shock protein of 70 kDa)/Hsp90-organizing protein], kinesin-light chain, Tom70 (translocase of outer mitochondrial membrane 70), FKBP52, CyP40 (cyclophilin 40), CHIP (C-terminus of Hsc70-interacting protein) and PP5 (protein phosphatase 5), leading to the dissociation of the interactions of the TPR proteins with their target proteins. Therefore we have hypothesized that Ca2+/S100 proteins can interact with FKBP38 and regulate its function. In vitro binding studies demonstrated that S100A1, S100A2, S100A6, S100B and S100P specifically interact with FKBP38 and inhibit the interaction of FKBP38 with Bcl-2 and Hsp90. Overexpression of permanently active S100P in Huh-7 cells inhibited the interaction of FKBP38 with Bcl-2, resulting in the suppression of Bcl-2 stability. The association of the S100 proteins with FKBP38 provides a Ca2+-dependent regulatory mechanism of the FKBP38-mediated signalling pathways.
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PMID:Ca2+/S100 proteins inhibit the interaction of FKBP38 with Bcl-2 and Hsp90. 2429 50