title: Interactions of S100A2 and S100A6 with the tetratricopeptide repeat proteins, Hsp90/Hsp70-organizing protein and kinesin light chain.
abstract: S100A2 and S100A6 interact with several target proteins in a Ca2+-regulated manner. However, the exact intracellular roles of the S100 proteins are unclear. In this study we identified Hsp70/Hsp90-organizing protein (Hop) and kinesin light chain (KLC) as novel targets of S100A2 and S100A6. Hop directly associates with Hsp70 and Hsp90 through the tetratricopeptide (TPR) domains and regulates Hop-Hsp70 and Hop-Hsp90 complex formation. We have found that S100A2 and S100A6 bind to the TPR domain of Hop, resulting in inhibition of the Hop-Hsp70 and Hop-Hsp90 interactions in vitro. Although endogenous Hsp70 and Hsp90 interact with Hop in resting Cos-7 cells, but not with S100A6, stimulation of these cells with ionomycin caused a Hop-S100A6 interaction, resulting in the dissociation of Hsp70 and Hsp90 from Hop. Similarly, glutathione S-transferase pulldown and co-immunoprecipitation experiments revealed that S100A6 binds to the TPR domain of KLC, resulting in inhibition of the KLC-c-Jun N-terminal kinase (JNK)-interacting protein 1 (JIP-1) interaction in vitro. The transiently expressed JIP-1 interacts with KLC in resting Cos-7 cells but not with S100A6. Stimulation of these cells with ionomycin also caused a KLC-S100A6 interaction, resulting in dissociation of JIP-1 from KLC. These results strongly suggest that the S100 proteins modulate Hsp70-Hop-Hsp90 multichaperone complex formation and KLC-cargo interaction via Ca2+-dependent S100 protein-TPR protein complex formation in vivo as well as in vitro. Moreover, we have shown that S100A2 and S100A6 interact with another TPR protein Tom70 and regulate the Tom70-ligand interaction in vitro. Thus, our findings suggest a new intracellular Ca2+-signaling pathway via S100 proteins-TPR motif interactions.
authors.affiliation: Department of Signal Transduction Sciences, Kagawa University Faculty of Medicine, 1750-1 Ikenobe, Kita-gun, Kagawa 761-0793, Japan.
authors.forename: Seiko
authors.initials: S
authors.lastname: Shimamoto
authors.forename: Maki
authors.initials: M
authors.lastname: Takata
authors.forename: Masaaki
authors.initials: M
authors.lastname: Tokuda
authors.forename: Fumikazu
authors.initials: F
authors.lastname: Oohira
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tokumitsu
authors.forename: Ryoji
authors.initials: R
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000737:chemistry*; D002630:Chemotactic Factors / Q000737:chemistry*; D002522:Chlorocebus aethiops; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry*; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry*; D006801:Humans; D016547:Kinesins / Q000737:chemistry*; D008024:Ligands; D026901:Membrane Transport Proteins / Q000378:metabolism*; D051379:Mice; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry*; D021381:Protein Transport; D051381:Rats; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins / Q000737:chemistry*
chemical_list: D018797:Cell Cycle Proteins; D002630:Chemotactic Factors; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D008024:Ligands; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D010455:Peptides; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; C483336:S100A2 protein, rat; C489132:S100a6 protein, rat; C402118:TOMM70 protein, human; D016547:Kinesins