Rab4: Proteins and Enzymes

Rab4 is a small GTPase that regulates recycling of proteins, such as GPCRs, from the early endosomes to the cell surface. Overexpression of Rab4 causes a redistribution of receptors on plasma membrane versus endocytic compartments. Rab4 is also involved in the translocation of glucose transporter (Glu4) in adipocytes in response to insulin. Association of Rab4 with transferrin receptor containing early endosomes is mediated through the geranylgeranyl groups at its carboxyl terminus. Rab4 can be used as a marker for early endosomes (see Daro et al. 1996 and Zuk et al. 1999 for more information). Membrane association is also cell cycle dependent, as phosphorylation at its C-terminal cdc2 kinase consensus sequence in mitotic cells leads to dissociation of Rab4 into the cytosol.