The problem of protein kinase activity of small heat shock protein Hsp22 (H11 or HspB8)
Department of Biochemistry, Lomonosov Moscow State University, Moskva, Moscow, RussiaBiochemical and Biophysical Research Communications (Impact Factor: 2.3). 12/2004; 325(3):649-52. DOI: 10.1016/j.bbrc.2004.10.074
The recently described protein denoted H11, Hsp22 or HspB8 seems to participate in regulation of proliferation, apoptosis, and cardiac hypertrophy. Mutation of Hsp22 causes distal motor neuropathy. Multitude action of Hsp22 is supposed to be due to its protein kinase and/or chaperone-like activities. There are many indirect evidences indicating that Hsp22 possesses intrinsic protein kinase activity. However, low homology to protein kinases, low extent of autophosphorylation, lack of significant protein kinase activity with commonly used substrates, and lack of information on stoichiometry, kinetics, and substrate specificity make the existence of intrinsic protein kinase activity of Hsp22 questionable. It is supposed that protein kinase activity ascribed to Hsp22 is due to contaminating protein kinases. Hsp22 is highly homologous to small heat shock proteins and effectively prevents aggregation of denatured protein both in vitro and in vivo. Therefore, it is supposed that chaperone-like activity is of great importance for Hsp22 functioning.
The Big Book on Small Heat Shock Proteins, Springer edited by Robert M. Tanguay • Lawrence E. Hightower, 01/2015: chapter 18: pages 435-456; Springer International Publishing AG Switzerland., ISBN: ISBN 978-3-319-16077-1 (eBook)
- "autophosphorylation assays, raising the possibility for contaminations by associated protein kinases (Depre et al. 2002; Kim et al. 2004a, b). In contrast, there are many strong data in support of the chaperone-like activity of HspB8. "
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ABSTRACT: Many cellular signaling molecules exist in different conformations corresponding to active and inactive states. Transition between these states is regulated by reversible modifications, such as phosphorylation, or by binding of nucleotide triphosphates, their regulated hydrolysis to diphosphates, and their exchange against fresh triphosphates. Specificity and efficiency of cellular signaling is further maintained by regulated subcellular localization of signaling molecules as well as regulated protein-protein interaction. Hence, it is not surprising that molecular chaperones--proteins that are able to specifically interact with distinct conformations of other proteins--could per se interfere with cellular signaling. Hence, it is not surprising that chaperones have co-evolved as integral components of signaling networks where they can function in the maturation as well as in regulating the transition between active and inactive state of signaling molecules, such as receptors, transcriptional regulators and protein kinases. Furthermore, new classes of specific chaperones are emerging and their role in histone-mediated chromatin remodeling and RNA folding are under investigation.Handbook of experimental pharmacology 02/2006; 172(172):93-109. DOI:10.1007/3-540-29717-0_4
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ABSTRACT: Some properties of the K141E mutant of human HSP22 that is expressed in distal hereditary motor neuropathy were investigated. This mutation slightly decreased intrinsic fluorescence of HSP22 and induced changes in the far UV CD spectra that correlate with increase of disordered structure. Destabilized K141E mutant was more susceptible to trypsinolysis than the wild type protein. Mutation K141E did not significantly affect the hydrophobic properties measured by bis-ANS binding and did not affect the quaternary structure of HSP22. With insulin as a substrate the chaperone-like activity of K141E mutant and the wild type protein were similar. However with alcohol dehydrogenase and rhodanese the chaperone-like activity of K141E mutant was remarkably lower than the corresponding activity of the wild type protein. It is concluded that K141E mutation induces destabilization of HSP22 structure and probably by this means diminish the chaperone-like activity of HSP22 with certain protein substrates.Archives of Biochemistry and Biophysics 11/2006; 454(1):32-41. DOI:10.1016/j.abb.2006.07.014 · 3.02 Impact Factor
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