Does GLUT4 Queue? A Mechanistic Mathematical Model for Insulin Response in Adipocytes

Mammalian cells regulate their glucose levels by redistributing glucose transporter proteins within the cell. Glucose Transporter 4 (GLUT4) is the main insulin-regulated glucose transporter in mammalian cells. Insulin signals the redistribution of GLUT4 from intracellular compartments to the cell surface. The mechanisms of the release of GLUT4 and subsequent transport to the plasma membrane remain an open question. Here, a biologically plausible model of GLUT4 translocation is presented. Using a stochastic queuing model, we find that changing only the number of fusion sites available for GLUT4-containing vesicles as a function of insulin is sufficient to explain experimental observations. Thus, the activity of the fusion sites could be the primary determinant of the dynamics of GLUT4.