Coupling of cargo to the autophagy receptor is a critical step in ER-phagy.

Abstract

During cell stress, endoplasmic reticulum autophagy (ER-phagy) receptors remodel the ER by sequestering membrane proteins (cargo) into autophagosomes for degradation. The conserved ER-phagy receptor, Atg40, contains a motif that binds to Atg8 and a reticulon homology domain that is needed for vacuolar/lysosomal delivery. Cargo capture, however, requires the Atg40 binding partner Lst1/SEC24C. To address whether lipids regulate cargo capture during ER-phagy, we analyzed autophagy in neutral lipid-deficient cells. Unexpectedly, we found that Atg40 was delivered to the vacuole in autophagosomes without Lst1/SEC24C or cargo in mutant cells. Lipidomic analysis revealed changes in the ratio of phosphatidylethanolamine to phosphatidylcholine in the neutral lipid-deficient cells that are predicted to alter ER membrane bendability. Our findings imply that phospholipids control cargo sequestration by regulating receptor-cargo coupling at autophagic sites.