May act as a GTPase-activating protein for Rab family protein(s). May play a role in the cell cycle and differentiation of various tissues. Involved in the trafficking and translocation of GLUT4-containing vesicles and insulin-stimulated glucose uptake into cells (By similarity). Interacts with APPL2 (via BAR domain); interaction is dependent of TBC1D1 phosphorylation at Ser-235; interaction diminishes the phosphorylation of TBC1D1 at Thr-596, resulting in inhibition of SLC2A4/GLUT4 translocation and glucose uptake. Insulin-stimulated phosphorylation by AKT family kinases stimulates SLC2A4/GLUT4 translocation.