RAB11, A SMALL GTPASE ASSOCIATED WITH BOTH CONSTITUTIVE AND REGULATED SECRETORY PATHWAYS IN PC12-CELLS

A specific polyclonal antibody was used to investigate the subcellular distribution of the small GTPase, rab11p, in the neuroendocrine cell line, PC12. We took advantage of a previously described pulse-chase protocol based on sulfation [1] to examine the distribution of rab11 along the secretory pathway. Using the rab11 antiserum, but not serum depleted of rab11 antibodies, we were able to specifically immunoisolate markers of the constitutive and the regulated secretory pathway in the trans-Golgi network (TGN) as well as after their exit from this compartment (constitutive secretory vesicles, immature, and mature secretory granules). We therefore conclude that rab11p is associated with the TGN and with TGN-derived vesicles of both the constitutive and the regulated secretory pathway in PC12 cells.