A Ypt/Rab GTPase module makes a PAS

Abstract

Organization of membrane microdomains by Ypt/Rab GTPases is key for all membrane trafficking events in eukaryotic cells. Since autophagy is a membrane trafficking process, it was expected that these GTPases would play a role in autophagy as well. While evidence about participation of Ypt/Rabs in autophagy is beginning to emerge, the mechanisms by which they act in this process are still not clear. Moreover, it is still questionable if and how Ypt/Rabs coordinate autophagy with other cellular trafficking processes. Yeast Ypt1 and its mammalian homolog Rab1 are required for both endoplasmic reticulum (ER)-to-Golgi transport and autophagy, suggesting that they coordinate these two processes. In our recent paper, we identify Atg11, a bona fide phagophore assembly site (PAS) component, as a downstream effector of Ypt1. Moreover, we show that three components of a GTPase module - the Ypt1 activator, Trs85-containing TRAPP complex, Ypt1, and the Atg11 effector - interact on the PAS and are required for PAS formation during selective autophagy. We propose that Ypt/Rabs coordinate the secretory and the autophagic pathways by recruiting process-specific effectors. © 2012 Landes Bioscience.