title: Sulfatide-Hsp70 interaction promotes Hsp70 clustering and stabilizes binding to unfolded protein.
abstract: The 70-kDa heat shock protein (Hsp70), one of the major stress-inducible molecular chaperones, is localized not only in the cytosol, but also in extracellular milieu in mammals. Hsp70 interacts with various cell surface glycolipids including sulfatide (3'-sulfogalactosphingolipid). However, the molecular mechanism, as well as the biological relevance, underlying the glycolipid-Hsp70 interaction is unknown. Here we report that sulfatide promotes Hsp70 oligomerization through the N-terminal ATPase domain, which stabilizes the binding of Hsp70 to unfolded protein in vitro. We find that the Hsp70 oligomer has apparent molecular masses ranging from 440 kDa to greater than 669 kDa. The C-terminal peptide-binding domain is dispensable for the sulfatide-induced oligomer formation. The oligomer formation is impaired in the presence of ATP, while the Hsp70 oligomer, once formed, is unable to bind to ATP. These results suggest that sulfatide locks Hsp70 in a high-affinity state to unfolded proteins by clustering the peptide-binding domain and blocking the binding to ATP that induces the dissociation of Hsp70 from protein substrates.
authors.affiliation: The Laboratory of Animal Cell Function, Bioscience and Biotechnology Center, Nagoya University, Nagoya 464-8601, Japan. yoharada@m.kufm.kagoshima-u.ac.jp.|Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan. yoharada@m.kufm.kagoshima-u.ac.jp.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Harada
authors.affiliation: The Laboratory of Animal Cell Function, Bioscience and Biotechnology Center, Nagoya University, Nagoya 464-8601, Japan. chi@agr.nagoya-u.ac.jp.|Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan. chi@agr.nagoya-u.ac.jp.
authors.forename: Chihiro
authors.initials: C
authors.lastname: Sato
authors.affiliation: The Laboratory of Animal Cell Function, Bioscience and Biotechnology Center, Nagoya University, Nagoya 464-8601, Japan. kitajima@agr.nagoya-u.ac.jp.|Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan. kitajima@agr.nagoya-u.ac.jp.
authors.forename: Ken
authors.initials: K
authors.lastname: Kitajima
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D011485:Protein Binding; D017510:Protein Folding; D055503:Protein Multimerization; D055550:Protein Stability; D013433:Sulfoglycosphingolipids / Q000737:chemistry*
chemical_list: D018840:HSP70 Heat-Shock Proteins; D013433:Sulfoglycosphingolipids; D000255:Adenosine Triphosphate
keywords: Hsp70; high molecular-weight complex; oligomerization; sulfatide