Tetrameric GLUT4, the SLC2A4 gene product, associated with the plasma membrane, mediates the facilitated diffusion of glucose (Glc) into cells. GLUT4 is found in heart, skeletal muscle, brain and adipose tissue. GLUT4 molecules are translocated from an intracellular store to the cell surface in response to increased insulin levels, increasing glucose transport 10-20-fold (Bryant et al. 2002; Fukumoto et al. 1989). Defects in SLC2A4 may be a cause of non-insulin-dependent diabetes mellitus (NIDDM) (Kusari et al. 1991; Choi et al. 1991).