This laboratory investigates intracellular protein traffic with special emphasis on the delivery of secretory and membrane proteins from the Golgi apparatus to the two differentiated cell surface domains of polarized epithelial cells. We have developed in vitro systems to produce post-Golgi carrier vesicles, and we are defining the cytosolic and membrane proteins that control this process and play a role in sorting the proteins incorporated into the vesicles.

Rab proteins, low molecular weight GTP-binding proteins, are important in vesicular transport, but the molecular interactions through which they exert their action are yet unknown. We identified and cloned novel proteins (rab8ip and rab11bp) that interact with two specific rab proteins, rab8 and rab11, that participate in trafficking to the cell surface. These proteins recognize only the active GTP-containing forms of the rabs and likely serve as their effectors. We investigate the rab8 interacting protein, which is a ser/thr protein kinase, and how its activity contributes to vesicle formation and/or targeting. We and others have recently found that rab11 controls the traffic of plasma membrane receptors through the recycling endosome and discovered the association of rab11 and rab11bp, which takes place on the endosomal membrane is required for the normal function of the endocytic recycling pathway. We are now investigating how the association of rab11 with its binding protein enables the rab to exert its controlling role in recycling. We collaborate in most studies with David D. Sabatini, M.D., Ph.D., also of the NYU School of Medicine.