Targeting motifs in GLUT4

The trafficking of the insulin-sensitive glucose transporter, GLUT4, is the paradigm of how cells control the movement of membrane proteins through intricate pathways of transport in response to external stimuli, and how, by doing so, regulate their function. The GLUT4 intracellularly sequestered in resting adipocytes and muscle cells becomes exposed on their surface in response to an increase in insulin levels and muscle contraction, where it facilitates glucose uptake. Ceasing of the stimuli is followed by endocytosis of the GLUT4 molecules exposed on the plasma membrane and their recycling to the original stores, where they are retained. This review discusses current understanding of the organelles that host GLUT4 and the motifs that mediate its trafficking.