Abstract
Although calmodulin is known to be a component of the Hsp70/Hsp90 multichaperone complex, the functional role of the protein remains uncertain. In this study, we have identified S100A1, but not calmodulin or other S100 proteins, as a potent molecular chaperone and a new member of the multichaperone complex. Glutathione S-transferase pull-down assays and co-immunoprecipitation experiments indicated the formation of stable complexes between S100A1 and Hsp90, Hsp70, FKBP52, and CyP40 both in vitro and in mammalian cells. S100A1 potently protected citrate synthase, aldolase, glyceraldehyde-3-phosphate dehydrogenase, and rhodanese from heat-induced aggregation and suppressed the aggregation of chemically denatured rhodanese and citrate synthase during the refolding pathway. In addition, S100A1 suppressed the heat-induced inactivation of citrate synthase activity, similar to that for Hsp90 and p23. The chaperone activity of S100A1 was antagonized by calmodulin antagonists, such as fluphenazine and prenylamine, that is, indeed an intrinsic function of the protein. The overexpression of S100A1 in COS-7 cells protected transiently expressed firefly luciferase and Escherichia coli beta-galactosidase from inactivation during heat shock. The results demonstrate a novel physiological function for S100A1 and bring us closer to a comprehensive understanding of the molecular mechanisms of the Hsp70/Hsp90 multichaperone complex.
MeSH terms
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Amino Acid Sequence
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Animals
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Brain / metabolism
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Calcium / metabolism
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Calcium-Binding Proteins / chemistry
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Calcium-Binding Proteins / genetics
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Calcium-Binding Proteins / metabolism*
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Calmodulin / metabolism
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Carrier Proteins / chemistry
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Carrier Proteins / genetics
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Carrier Proteins / metabolism
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Cattle
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Cyclophilins*
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HSP70 Heat-Shock Proteins / chemistry
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HSP70 Heat-Shock Proteins / genetics
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HSP70 Heat-Shock Proteins / metabolism*
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HSP90 Heat-Shock Proteins / chemistry
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HSP90 Heat-Shock Proteins / genetics
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HSP90 Heat-Shock Proteins / metabolism*
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Humans
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In Vitro Techniques
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Kinetics
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Macromolecular Substances
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Molecular Chaperones / chemistry
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Molecular Chaperones / genetics
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Molecular Chaperones / metabolism*
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Molecular Sequence Data
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Peptidylprolyl Isomerase / chemistry
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Peptidylprolyl Isomerase / genetics
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Peptidylprolyl Isomerase / metabolism
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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S100 Proteins
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Surface Plasmon Resonance
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Tacrolimus Binding Proteins / chemistry
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Tacrolimus Binding Proteins / genetics
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Tacrolimus Binding Proteins / metabolism
Substances
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Calcium-Binding Proteins
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Calmodulin
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Carrier Proteins
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HSP70 Heat-Shock Proteins
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HSP90 Heat-Shock Proteins
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Macromolecular Substances
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Molecular Chaperones
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Recombinant Fusion Proteins
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S100 Proteins
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S100A1 protein
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Cyclophilins
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Tacrolimus Binding Proteins
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tacrolimus binding protein 4
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PPID protein, human
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Peptidylprolyl Isomerase
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Calcium