Cholesterol and ORP1L-mediated ER contact sites control autophagosome transport and fusion with the endocytic pathway.

Ruud H Wijdeven,Ilana Berlin,Kees Jalink,Leila Nahidiazar,Hans Janssen,Jacques Neefjes,Lennert Janssen

doi:10.1038/ncomms11808

Abstract

Autophagy is the main homeostatic pathway guiding cytosolic materials for degradation by the lysosome. Maturation of autophagosomes requires their transport towards the perinuclear region of the cell, with key factors underlying both processes still poorly understood. Here we show that transport and positioning of late autophagosomes depends on cholesterol by way of the cholesterol-sensing Rab7 effector ORP1L. ORP1L localizes to late autophagosomes and—under low-cholesterol conditions—contacts the ER protein VAP-A, forming ER-autophagosome contact sites, which prevent minus-end transport by the Rab7–RILP–dynein complex. ORP1L-mediated contact sites also inhibit localization of PLEKHM1 to Rab7. PLEKHM1, together with RILP, then recruits the homotypic fusion and vacuole protein-sorting (HOPS) complex for fusion of autophagosomes with late endosomes and lysosomes. Thus, ORP1L, via its liganding by lipids and the formation of contacts between autophagic vacuoles and the ER, governs the last steps in autophagy that lead to the lysosomal degradation of cytosolic material.

Highlights

Autophagy is the main homeostatic pathway guiding cytosolic materials for degradation by the lysosome
ORP1L localizes to amphisomes and autolysosomes and, under low cholesterol conditions, contacts the ER protein VAP-A to form intimate membrane contact sites (MCSs) with the ER
We identify a negative regulator of autophagosome fusion with the late endosomes (LEs)/Ly—which functions as a cholesterol sensor poised on receiving vesicles to either licence or refute autophagic progression

Summary

Introduction

Autophagy is the main homeostatic pathway guiding cytosolic materials for degradation by the lysosome. PLEKHM1, together with RILP, recruits the homotypic fusion and vacuole protein-sorting (HOPS) complex for fusion of autophagosomes with late endosomes and lysosomes. Rab[7] can associate with several effectors, including RILP, which recruits the dynein–dynactin motor for minus-end transport[28,29] Whether autophagosomes utilize this Rab7-associated transport and fusion machinery en route to the lysosome, and if so, what factors control this process, is not known. ORP1L localizes to amphisomes and autolysosomes and, under low cholesterol conditions, contacts the ER protein VAP-A to form intimate membrane contact sites (MCSs) with the ER These ER-autophagosome MCSs prevent dynactin binding to RILP, blocking dynein-mediated transport. Our study reveals a molecular mechanism whereby ORP1L, via its liganding by lipids and the formation of contacts between AVs and the ER, controls the degradation of cytosolic components by autophagy

Methods

Results

Conclusion