Chaperones in preventing protein denaturation in living cells and protecting against cellular stress.
A variety of cellular internal and external stress conditions can be classified as proteotoxic stresses. Proteotoxic stresses can be defined as stresses that increase the fraction of proteins that are in an unfolded state, thereby enhancing the probability of the formation of intracellular aggregates. These aggregates, if not disposed, can lead to cell death. In response to the appearance of damaged proteins, cells induce the expression of heat shock proteins. These can function as molecular chaperones to prevent protein aggregation and to keep proteins in a state competent for either refolding or degradation. Most knowledge of the function and regulation (by co-factors) of individual heat shock proteins comes from cell free studies on refolding of heat- or chemically denatured, purified proteins. Unlike the experimental situation in a test tube, cells contain multiple chaperones and co-factors often moving in and out different subcompartments that contain a variety of protein substrates at different folding states. Also, within cells folding competes with the degradative machinery. In this chapter, an overview will be provided on how the main cytosolic/nuclear chaperone Hsp70 is regulated, what is known about its interaction with other main cytosolic/nuclear chaperone families (Hsp27, Hsp90, and Hsp110), and how it may function as a molecular chaperone in living mammalian cells to protect against proteotoxic stresses.
Kampinga
H H
HH
Department of Cell Biology, Section of Radiation and Stress Cell Biology, Faculty of Medical Sciences, University of Groningen, The Netherlands. h.h.kampinga@med.rug.nl
D000818:Animals; D017209:Apoptosis; D004268:DNA-Binding Proteins / Q000502:physiology; D050956:HSP40 Heat-Shock Proteins / Q000502:physiology; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology; D018841:HSP90 Heat-Shock Proteins / Q000502:physiology; D006801:Humans; D018832:Molecular Chaperones / Q000502:physiology*; D011489:Protein Denaturation; D017510:Protein Folding; D013312:Stress, Physiological / Q000517:prevention & control*; D014157:Transcription Factors / Q000502:physiology
C091732:BCL2-associated athanogene 1 protein; D004268:DNA-Binding Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; C105426:Hip chaperone; D018832:Molecular Chaperones; D014157:Transcription Factors