The Rab5 effector EEA1 interacts directly with syntaxin-6

The fusion of transport vesicles with their cognate target membranes, an es sential event in intracellular membrane trafficking, is regulated by SNARE proteins and Rab GTPases. Rab GTPases are thought to act prior to SNAREs in vesicle docking, but the exact biochemical relationship between the two cl asses of molecules is not known. We recently identified the early endosomal autoantigen EEA1 as an effector of Rab5 in endocytic membrane fusion. Here we demonstrate that EEA1 interacts directly and specifically with syntaxin -6, a SNARE implicated in trans-Golgi network to early endosome trafficking . The binding site for syntaxin-6 overlaps with that of Rab5-GTP at the C t erminus of EEA1. Syntaxin-6 and EEA1 were found to colocalize extensively o n early endosomes, although syntaxin-6 is present in the trans-Golgi networ k as well. Our results indicate that SNAREs can interact directly with Rab effecters, and suggest that EEA1 may participate in trans-Golgi network to endosome as well as in endocytic membrane traffic.