High glucose levels induce inhibition of Na,K-ATPase via stimulation of aldose reductase, formation of microtubules and formation of an acetylated tubulin/Na,K-ATPase complex

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• 作者：Juan F. Rivelli^a ; Marina R. Amaiden^a ; Noelia E. Monesterolo^a ; Gabriela Previtali^a ; Veró ; nica S. Santander^a ; Adriana Fernandez^a ; Carlos A. Arce^b ; Cesar H. Casale^a ; ^{ccasale@exa.unrc.edu.ar}
• 关键词：AcTub ; acetylated tubulin ; AR ; aldose reductase ; PAGE ; polyacrylamide gel electrophoresis ; PMSF ; phenylmethylsulfonylfluoride ; SDS ; sodium dodecyl sulfate ; NKA ; Na+ ; K+-ATPase ; TSA ; trichostatin A ; N erythrocytes ; erythrocytes from normal subjects ; D eryth
• 刊名：The International Journal of Biochemistry and Cell Biology
• 出版年：2012
• 期刊代码：127_13572725
• 类别：med
• 出版时间：August, 2012
• 卷：44
• 期：8
• 页码：1203-1213
• 文件大小：1449 K

摘要

Our previous studies demonstrated that acetylated tubulin forms a complex with Na⁺,K⁺-ATPase and thereby inhibits its enzyme activity in cultured COS and CAD cells. The enzyme activity was restored by treatment of cells with l-glutamate, which caused dissociation of the acetylated tubulin/Na⁺,K⁺-ATPase complex. Addition of glucose, but not elimination of glutamate, led to re-formation of the complex and inhibition of the Na⁺,K⁺-ATPase activity. The purpose of the present study was to elucidate the mechanism underlying this effect of glucose. We found that exposure of cells to high glucose concentrations induced: (a) microtubule formation; (b) activation of aldose reductase by the microtubules; (c) association of tubulin with membrane; (d) formation of the acetylated tubulin/Na⁺,K⁺-ATPase complex and consequent inhibition of enzyme activity. Exposure of cells to sorbitol caused similar effects. Studies on erythrocytes from diabetic patients and on tissues containing insulin-insensitive glucose transporters gave similar results. Na⁺,K⁺-ATPase activity was >50%lower and membrane-associated tubulin content was >200%higher in erythrocyte membranes from diabetic patients as compared with normal subjects. Immunoprecipitation analysis showed that acetylated tubulin was a constituent of a complex with Na⁺,K⁺-ATPase in erythrocyte membranes from diabetic patients. Based on these findings, we propose a mechanism whereby glucose triggers a synergistic effect of tubulin and sorbitol, leading to activation of aldose reductase, microtubule formation, and consequent Na⁺,K⁺-ATPase inhibition.