Figure 1

Recycling of Glut4. The cellular location of Glut4 is governed by a process of regulated recycling, in which the endocytosis, sorting into specialized vesicles, exocytosis, tethering, docking, and fusion of the protein are tightly regulated. In the absence of insulin, Glut4 slowly recycles between the plasma membrane and vesicular compartments within the cell, where most of the Glut4 resides. Insulin stimulates the translocation of a pool of Glut4 to the plasma membrane, through a process of targeted exocytosis. The microtubule network and actin cytoskeleton play a role in Glut4 trafficking, either by linking signaling components or by directing movement of vesicles from the perinuclear region to the plasma membrane in response to insulin. Once at the plasma membrane, the Glut4 vesicles dock and fuse, allowing for extracellular exposure of the transporter.