Fig. 3.

A model for GLUT4 trafficking. In the absence of insulin (basal), a pool of GLUT4 is targeted to GSVs, which are derived from the TGN and/or endosomes. In the presence of insulin, these GSVs fuse directly with the plasma membrane in an initial burst (insulin burst). GLUT4 subsequently recycles through endosomes, the TGN and back to the plasma membrane through generic recycling compartments in the presence of insulin (‘continuous insulin’). Following insulin withdrawal, GLUT4 traffics through the TGN to re-form GSVs. Arrows represent different trafficking rates: low (light grey), medium (dark grey), high (black). Endo, endosomes.