7/30/2023 0 Comments Molecular chaperone hub![]() Navigating the chaperone network: an integrative map of physical and genetic interactions mediated by the Hsp90 chaperone. Diverse cellular functions of the Hsp90 molecular chaperone uncovered using systems approaches. pH-dependent conformational changes in bacterial Hsp90 reveal a Grp94-like conformation at pH6 that is highly active in suppression of citrate synthase aggregation. The first structural analysis of an HSP90–co-chaperone–client complex, paving the way for the molecular-level understanding of HSP90 specificity and function. Structure of an Hsp90-Cdc37-Cdk4 complex. Hsp90-dependent activation of protein kinases is regulated by chaperone-targeted dephosphorylation of Cdc37. Conserved conformational changes in the ATPase cycle of human Hsp90. The large conformational changes of Hsp90 are only weakly coupled to ATP hydrolysis. Mickler, M., Hessling, M., Ratzke, C., Buchner, J. The charged linker region is an important regulator of Hsp90 function. Hsp90 is regulated by a switch point in the C-terminal domain. Molecular chaperones Hsp90 and HSP70 deliver preproteins to the mitochondrial import receptor Tom70. Protein quality control: chaperones culling corrupt conformations. Asymmetric deceleration of ClpB or Hsp104 ATPase activity unleashes protein-remodeling activity. Converging concepts of protein folding in vitro and in vivo. Adapting proteostasis for disease intervention. Hyper-acidic protein fusion partners improve solubility and assist correct folding of recombinant proteins expressed in Escherichia coli. Protein misassembly: macromolecular crowding and molecular chaperones. Client protein recognition is one of the largest puzzles in the field.Įllis, R. HSP90 has been implicated in RNA processing, membrane trafficking and in innate and adaptive immunity.ĭespite the numerous client proteins, clear structural or sequence determinants for HSP90 binding remain largely unknown. In yeast, Hsp90 is functionally linked to ∼20% of all genes. However, recent studies have uncovered numerous genes and proteins that either physically or genetically interact with HSP90. ![]() The best-characterized HSP90 client proteins are kinases and steroid hormone receptors. Post-translational modifications of HSP90 and co-chaperones add further regulatory layers. Some co-chaperones modulate HSP90 ATPase activity and the chaperone cycle, and others seem to function as adaptors that recruit specific client proteins. ![]() More than 20 known co-chaperones regulate HSP90 function in many different ways. The extreme conformation flexibility of HSP90 sets it apart from other chaperone systems and renders its study remarkably complex. How the chaperone cycle is mechanistically connected to client protein folding is just beginning to be understood. HSP90 exists as a dimer that undergoes ATP-dependent conformational changes during client protein maturation (known as the chaperone cycle). In eukaryotes, HSP90 is essential for survival during heat and other stresses, but it also has a central role in a vast array of signal transduction pathways in non-stressful conditions. The Company of Biologists Ltd.Heat shock protein 90 (HSP90) is an abundant and evolutionarily highly conserved molecular chaperone that regulates the maturation, activity and stability of a wide range of substrate proteins (clients). Therefore, a balance between the UPS and the chaperones tightly controls neuronal differentiation.ĭevelopment, 2020, v. The abundance of DLK-1, and likely other Hsp90 substrates, is fine-tuned by the antagonism between MEC-15 and the chaperones this antagonism regulates TRN development, as well as synaptic functions of GABAergic motor neurons. MEC-15 probably functions in a Skp-, Cullin- and F-box- containing complex to degrade DLK-1, which is an Hsp90 client protein stabilized by the chaperones. ![]() Using the touch receptor neurons (TRNs) of Caenorhabditis elegans, we find that mec-15(-) mutants display defects in microtubule formation, neurite growth, synaptic development and neuronal functions, and that these defects can be rescued by the loss of Hsp70/Hsp90 chaperones and co-chaperones. In this study, however, we report that the Hsp70/Hsp90 chaperone machinery and an F-box protein, MEC-15, have opposing effects on neuronal differentiation, and that the chaperones negatively regulate neuronal morphogenesis and functions. Molecular chaperones often work collaboratively with the ubiquitylation-proteasome system (UPS) to facilitate the degradation of misfolded proteins, which typically safeguards cellular differentiation and protects cells from stress.
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