The role of small G-proteins in the regulation of glucose transport

Insulin increases the rate of glucose transport into fat and muscle cells b y stimulating the translocation of intracellular Glut 4-containing vesicles to the plasma membrane. This results in a marked increase in the amount of the facilitative glucose transporter Glut 4 at the cell surface, allowing for an enhanced glucose uptake. This process requires a continuous cycling through the early endosomes, a Glut 4 specific storage compartment and the plasma membrane. The main effect of insulin is to increase the rate of Glut 4 trafficking from its specific storage compartment to the plasma membrane. The whole phenomenon involves signal transduction from the insulin recepto r, vesicle trafficking (sorting and fusion processes) and actin cytoskeleto n modifications, which are all supposed to require small GTPases. This revi ew describes the potential role of the various members of the Ras, Rad, Rho , Arf and Rab families in the traffic of the Glut 4-containing vesicles.