THE KDEL RECEPTOR, ERD2, REGULATES INTRACELLULAR TRAFFIC BY RECRUITING A GTPASE-ACTIVATING PROTEIN FOR ARF1

The small GTPase ADP-ribosylation factor 1 (ARF1) is a key regulator o f intracellular membrane traffic, Regulators of ARF1, its GTPase-activ ating protein (GAP) and its guanine nucleotide exchange factor have be en identified recently, However, it remains uncertain whether these re gulators drive the GTPase cycle of ARF1 autonomously or whether their activities can be regulated by other proteins, Here, we demonstrate th at the intracellular KDEL receptor, ERD2, self-oligomerizes and intera cts with ARF1 GAP, and thereby regulates the recruitment of cytosolic ARF1 GAP to membranes, Because ERD2 overexpression enhances the recrui tment of GAP to membranes and results in a phenotype that reflects ARF 1 inactivation, our findings suggest that ERD2 regulates ARF1 GAP, and thus regulates ARF1-mediated transport.