S70

DIABETES, VOLUME 45, SUPPLEMENT 1, JANUARY 1996, PAGES S70-S81

Insulin-Induced Redistribution of GLUT4 Glucose Carriers in the Muscle Fiber

In Search of GLUT4 Trafficking Pathways

Antonio Zorzano, Purificacion Munoz, Marta Camps, Conchi Mora, Xavier Testar,
and Manuel Palacin

Insulin rapidly stimulates glucose transport in muscle fiber. This process controls the utilization of glucose in skeletal muscle, and it is deficient in various insulin-resistant states, such as non-insulin-dependent diabetes mellitus. The effect of insulin on muscle glucose transport is mainly due to the recruitment of GLUT4 glucose carriers to the cell surface of the muscle fiber. There is increasing evidence that the recruitment of GLUT4 carriers triggered by insulin affects selective domains of sarcolemma and transverse tubules. In contrast, GLUTl is located mainly in sarcolemma and is absent in transverse tubules, and insulin does not alter its cellular distribution in muscle fiber. The differential distribution of GLUT1 and GLUT4 in the cel1 surface raises new questions regarding the precise endocytic and exocytic pathways that are functional in the muscle fiber. The current view of insulin-induced GLUT4 translocation is based mainly on studies performed in adipocytes. These studies have proposed the existence of intracellular compartments of GLUT4 that respond to insulin in a highly homogeneous manner. However, studies performed in skeletal muscle have identified insulin-sensitive as well as insulin-insensitive intracellular GLUT4-containing membranes. These data open a new perspective on the dynamics of intracellulr GLUT4 compartments in insulin-sensitive cells. Diabetes 45 (Suppl. 1):S70-S81, 1996

Last updated: 5/30/96
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