Dombrowski L, Marette A
Department of Physiology, Laval University Hospital Research Center, Ste-Foy, Qubec, Canada.
FEBS Lett. 1995 Oct 23;374(1):43-7. doi: 10.1016/0014-5793(95)01071-l.
The principal goal of the present study was to determine the subcellular content of GLUT4 in diabetic rat muscle, and to test the hypothesis that a reduced abundance of the transporter protein in transverse tubules is responsible for impaired glucose utilization in that tissue. GLUT4 protein levels were measured in hindlimb muscle homogenates as well as in subcellular membrane fractions enriched with either plasma membranes, transverse tubules, or GLUT4-containing intracellular membranes from control and diabetic (streptozotocin-induced) rats. GLUT4 protein contents in diabetic muscle homogenates was reduced by 30% as compared to control rats. Subcellular fractionation experiments revealed that GLUT4 contents in transverse tubules-enriched fractions was markedly decreased (by 55-60%) in skeletal muscle of diabetic animals whereas no significant reductions in GLUT4 abundance was observed in the plasma membrane fraction. Moreover, GLUT4 was markedly depleted (by 45%) in the GLUT4-enriched intracellular membrane fraction. These results indicate that GLUT4 is markedly depleted in both the intracellular pool and in the cell surface membranes in muscle of STZ-diabetic rats. Most strikingly, this study demonstrates that transverse tubules and not the plasma membrane are the main sites of cell surface GLUT4 depletion in diabetic muscle.
本研究的主要目的是确定糖尿病大鼠肌肉中GLUT4的亚细胞含量，并验证以下假设：横管中转运蛋白丰度降低是该组织葡萄糖利用受损的原因。测量了对照大鼠和糖尿病（链脲佐菌素诱导）大鼠后肢肌肉匀浆以及富含质膜、横管或含GLUT4的细胞内膜的亚细胞膜组分中的GLUT4蛋白水平。与对照大鼠相比，糖尿病肌肉匀浆中的GLUT4蛋白含量降低了30%。亚细胞分级实验显示，糖尿病动物骨骼肌中富含横管的组分中的GLUT4含量显著降低（降低55%-60%），而质膜组分中未观察到GLUT4丰度有显著降低。此外，富含GLUT4的细胞内膜组分中的GLUT4明显减少（减少45%）。这些结果表明，在链脲佐菌素诱导的糖尿病大鼠肌肉中，细胞内池和细胞表面膜中的GLUT4均明显减少。最引人注目的是，本研究表明，糖尿病肌肉中细胞表面GLUT4减少的主要部位是横管而非质膜。
