RAB5c orchestrates LC3-associated phagocytosis to promote microbicidal function of macrophages.

Abstract

Noncanonical 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 <i>Aspergillus fumigatus</i> and disruption of the V-ATPase-ATG16L1 axis increased susceptibility in vivo. Thus, early endosome-to-phagosome trafficking can be selectively engaged to promote pathogen elimination by directing phagosomal maturation toward LAP.