RAB5c controls the assembly of non-canonical autophagy machinery to promote phagosome maturation and microbicidal function of macrophages

Abstract

Non-canonical conjugation of ATG8 proteins, including LC3, to single membranes implicates the autophagy machinery in cell functions unrelated to metabolic stress. One such pathway is LC3-associated phagocytosis (LAP), which aids in phagosome maturation and subsequent signaling upon cargo uptake mediated by certain innate immunity-associated receptors. Here, we show that a specific isoform of RAB5 GTPases, the molecular switches controlling early endosome traffic, is necessary for LAP. We demonstrate that RAB5c regulates phagosome recruitment and function of complexes required for phosphatidylinositol-3-phosphate [PI(3)P] and reactive oxygen species (ROS) generation by macrophages. RAB5c facilitates phagosome translocation of the V-ATPase transmembrane core, which is needed for ATG16L1 binding and consequent LC3 conjugation. RAB5c depletion impaired macrophage elimination of the fungal pathogen Aspergillus fumigatus and disruption of the V-ATPase-ATG16L1 axis increased susceptibility in vivo. Therefore, early endosome-to-phagosome traffic is differentially regulated to promote LAP and ROS contributes to resistance against A. fumigatus by effecting LAP. HIGHLIGHTSO_LIRAB5c is required for LC3-associated phagocytosis C_LIO_LIRAB5c finetunes NAPDH oxidase assembly and ROS generation in the phagosome C_LIO_LIRAB5c regulates V-ATPase assembly on the phagosome C_LIO_LIRAB5c and V-ATPase-ATG16L1 axis are required for the killing of A. fumigatus C_LI