title: Up-regulation of sodium-dependent glucose transporter by interaction with heat shock protein 70.
abstract: Heat shock stress induces some heat shock proteins, including Hsp70, and activates sodium-dependent glucose transport in porcine renal LLC-PK(1) cells, but its mechanisms have not been described in detail. We investigated whether sodium-dependent glucose transporter (SGLT1) interacts with Hsp70 to increase SGLT1 activity. Heat shock stress increased SGLT1 activity without changing SGLT1 expression. The increase of SGLT1 activity was completely inhibited by an anti-transforming growth factor-beta1 (TGF-beta1) antibody. Instead of heat shock stress, TGF-beta1 increased SGLT1 activity dose- and time-dependently without changing SGLT1 expression. We found that the amount of Hsp70 immunoprecipitated from TGF-beta1-treated cells with an anti-SGLT1 antibody was higher than that of the control cells. Transfection of an anti-Hsp70 antibody into the cells inhibited the increase of SGLT1 activity. With confocal laser microscopy, both SGLT1 and Hsp70 was localized near the apical membrane in the TGF-beta1-treated cells, and an anti-Hsp70 antibody disturbed this localization. Furthermore, we clarified that an anti-Hsp70 antibody inhibited interaction of SGLT1 with Hsp70 in vitro. These results suggest that Hsp70 forms a complex with SGLT1 and increases the expression level of SGLT1 in the apical membrane, resulting in up-regulation of glucose uptake.
authors.affiliation: Department of Environmental Biochemistry and Toxicology, University of Shizuoka School of Pharmaceutical Sciences, 52-1 Yada, Shizuoka 422-8526, Japan. ikari@u-shizuoka-ken.ac.jp
authors.forename: Akira
authors.initials: A
authors.lastname: Ikari
authors.forename: Mika
authors.initials: M
authors.lastname: Nakano
authors.forename: Kazuya
authors.initials: K
authors.lastname: Kawano
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Suketa
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005947:Glucose / Q000378:metabolism / Q000493:pharmacokinetics; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006358:Hot Temperature; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000378:metabolism; D018613:Microscopy, Confocal; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D011233:Precipitin Tests; D051269:Sodium-Glucose Transporter 1; D013552:Swine; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000378:metabolism; D053773:Transforming Growth Factor beta1; D015854:Up-Regulation
chemical_list: D018840:HSP70 Heat-Shock Proteins; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D051269:Sodium-Glucose Transporter 1; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D000255:Adenosine Triphosphate; D005947:Glucose