POSSIBLE ROLE OF Rab21, Rab32 and VARP IN AUTOPHAGIC EXOCITOSIS

BARBOSA MC; NOLA S; GALLI T; COLOMBO MI; FADER CM

La Serena

Workshop; Actualizations in Membrane Trafficking in Health and Desease; 2016

EMBO

Autophagy is a degradation process, being LC3 the main autophagosomal membrane protein. Rab32, a GTP-aseinvolved in the cellular transport, is related to autophagy. We described that some autophagosomes redistribute to thecell periphery and they also fuse with plasma membrane in a VAMP7 (a v-SNARE) dependent manner. This proteincan interact with different proteins, like Rab21, its GEF (VARP) and Rab32. We found that Rab21 and LC3colocalize at the cell periphery after autophagic activation. The aim of this work is to evaluate the role of Rab21,Rab32 and VARP in the redistribution of exocytic autophagosomes after autophagic stimulus. HeLa cells weretransfected with GFP-Rab21 (wt or T33N), RFP-LC3 or YFP-Rab32 and then were incubated in starvation,rapamycin or resveratrol for 2-4 hours. We detected Golgi (GM130) or VARP proteins by immunofluorescence. Weobserved the presence of two populations of Rab32 vesicles: One is perinuclear and colocalizes with the Golgimarker; the other one colocalizes with VARP peripherically. We also found that upon autophagic stimulation, LC3-Rab32 or LC3-Rab21wt positive vesicles changed their distribution toward the periphery while Rab21 mutant stillcolocalizes with Golgi. Our result suggests that Rab32, Rab21 and VARP could be implicated in theautophagosomes? trafficking to the cell periphery, possibly favoring the autophagic exocytosis.