Required for insulin-stimulated glucose transport and glucose transporter SLC2A4/GLUT4 translocation from intracellular glucose storage vesicle (GSV) to the plasma membrane (PM) in adipocytes. Binds phospholipid membranes in a calcium-dependent manner and is necessary for the optimal membrane fusion between SLC2A4/GLUT4 GSV and the PM. Binds 3 Ca(2+) ions per C2 domain. Dynamically associated with GLUT4-containing glucose storage vesicles (GSV) and plasma membrane in response to insulin stimulation. The C2 domain binds to calcium and membrane lipids. Phosphorylated on Ser-197 by active myristoylated kinase AKT2; insulin-stimulated phosphorylation by AKT2 regulates SLC2A4/GLUT4 translocation into the plasma membrane.