Elucidation of the anti-autophagy mechanism of the Legionella effector RavZ using semisynthetic LC3 proteins

Abstract

Autophagy is a conserved cellular process involved in the elimination of proteins and organelles. It is also used to combat infection with pathogenic microbes. The intracellular pathogen <i>Legionella pneumophila</i> manipulates autophagy by delivering the effector protein RavZ to deconjugate Atg8/LC3 proteins coupled to phosphatidylethanolamine (PE) on autophagosomal membranes. To understand how RavZ recognizes and deconjugates LC3-PE, we prepared semisynthetic LC3 proteins and elucidated the structures of the RavZ:LC3 interaction. Semisynthetic LC3 proteins allowed the analysis of structure-function relationships. RavZ extracts LC3-PE from the membrane before deconjugation. RavZ initially recognizes the LC3 molecule on membranes via its N-terminal LC3-interacting region (LIR) motif. The RavZ α3 helix is involved in extraction of the PE moiety and docking of the acyl chains into the lipid-binding site of RavZ that is related in structure to that of the phospholipid transfer protein Sec14. Thus, <i>Legionella</i> has evolved a novel mechanism to specifically evade host autophagy.