Genome-wide CRISPR screen identifies TMEM41B as a gene required for autophagosome formation

  • J Cell Biol. 2018 Nov 5;217(11):3817-3828. doi: 10.1083/jcb.201804132.
Keigo Morita  1 ,  Yutaro Hama  1 ,  Tamaki Izume  2 ,  Norito Tamura  1 ,  Toshihide Ueno  3 ,  Yoshihiro Yamashita  3 ,  Yuriko Sakamaki  4 ,  Kaito Mimura  1 ,  Hideaki Morishita  1 ,  Wataru Shihoya  2 ,  Osamu Nureki  2 ,  Hiroyuki Mano  3 ,  Noboru Mizushima  5
Affiliations
  • 1. Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
  • 2. Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
  • 3. Department of Cellular Signaling, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
  • 4. Research Core, Tokyo Medical and Dental University, Tokyo, Japan.
  • 5. Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan [email protected].
PMID: 30093494 DOI: 10.1083/jcb.201804132
Abstract

Macroautophagy is an intracellular degradation process that requires multiple autophagy-related (ATG) genes. In this study, we performed a genome-wide screen using the autophagic flux reporter GFP-LC3-RFP and identified TMEM41B as a novel ATG gene. TMEM41B is a multispanning membrane protein localized in the endoplasmic reticulum (ER). It has a conserved domain also found in vacuole membrane protein 1 (VMP1), another ER multispanning membrane protein essential for Autophagy, yeast Tvp38, and the Bacterial DedA family of putative half-transporters. Deletion of TMEM41B blocked the formation of autophagosomes at an early step, causing accumulation of ATG proteins and small vesicles but not elongating autophagosome-like structures. Furthermore, lipid droplets accumulated in TMEM41B-knockout (KO) cells. The phenotype of TMEM41B-KO cells resembled those of VMP1-KO cells. Indeed, TMEM41B and VMP1 formed a complex in vivo and in vitro, and overexpression of VMP1 restored autophagic flux in TMEM41B-KO cells. These results suggest that TMEM41B and VMP1 function together at an early step of autophagosome formation.