Regulatory Mechanisms of Intracellular Distribution of Na<sup>+</sup>-dependent Glucose Transporter and the Role in Recovery from Cellular Injury

  • IKARI Akira
    Department of Environmental Biochemistry and Toxicology, School of Pharmaceutical Sciences, University of Shizuoka

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  • ナトリウム依存性糖輸送体の細胞内分布調節機構の解明と細胞障害からの回復における役割
  • ナトリウム イゾンセイ トウ ユソウタイ ノ サイボウ ナイ ブンプ チョウセツ キコウ ノ カイメイ ト サイボウ ショウガイ カラ ノ カイフク ニ オケル ヤクワリ

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Abstract

  Exposure of cells or organs to sublethal stress induces the expression of some heat-shock proteins (Hsp), including Hsp70. In porcine renal LLC-PK1 cells, heat stress (HS) elevates Hsp70 expression and Na+-dependent glucose transport. We examined whether Na+-dependent glucose transporter (SGLT1) interacts with Hsp70 to elevate SGLT1 activity and whether SGLT1 activation is involved in the recovery from HS injury. HS (42°C for 3 h) elevated SGLT1 activity and expression of SGLT1 in the apical membrane fraction. HS increased the maximal transport rate (Vmax), but did not affect the apparent affinity constant (Km) for glucose. The HS-induced SGLT1 activation was inhibited by anti-transforming growth factor (TGF)-β1 antibody. Furthermore, transfection of anti-Hsp70 antibody into the cells inhibited SGLT1 activation. These results suggest that HS induces TGF-β1 secretion, and then Hsp70 forms a complex with SGLT1 and increases the distribution of SGLT1 in the apical membrane. Next, we examined the effect of HS on plasma membrane integrity. Accumulation of calcein, a membrane-impermeable fluorescent dye, was decreased by HS and then returned to basal level. This recovery was inhibited by phloridzin, a selective SGLT inhibitor, and nonmetabolizable glucose analogues. Anti-TGF-β1 antibody also inhibited the recovery of calcein accumulation. Taken together, the present results show that HS elevates SGLT1 activity mediated via the TGF-β1 signaling pathway and that the increase in glucose uptake is necessary to repair plasma membrane injury.<br>

Journal

  • YAKUGAKU ZASSHI

    YAKUGAKU ZASSHI 124 (12), 959-964, 2004-12-01

    The Pharmaceutical Society of Japan

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