Host restriction factors mediate intrinsic immunity against infections, thus serving as promising targets for host-directed therapy (HDT) against drug-resistant pathogens. While restriction factors counteracting viruses have been extensively studied, those targeting bacteria, particularly those with broad-spectrum activity, remain largely unexplored. Here, through screening for host factors promoting lysosomal acidification, a crucial process clearing pathogens, we identify the host small GTPase Rab14 as a restriction factor with broad-spectrum activity against multiple bacteria and viruses. Mechanistically, upon pathogen infections, GTP-bound Rab14 increases and binds to the calcium/calmodulin-dependent protein kinase type 2 delta (CAMK2D), suppressing CAMK2D-mediated phosphorylation of V0a1, the critical subunit determining V-ATPase localization, thus promoting V0a1 binding to the COPⅡ complex to facilitate V-ATPase trafficking from the endoplasmic reticulum to lysosomes, resulting in lysosomal acidification and pathogen clearance. Taken together, our data demonstrate an unrecognized intrinsic immune mechanism mediated by Rab14-CAMK2D-V-ATPase axis, which might be a promising target for infectious diseases. Broad-spectrum host restriction factors against bacteria and viruses remain largely unclear. Here, the authors identify the small GTPase Rab14 as a restriction factor that promotes lysosomal acidification by delivering the V-ATPase to lysosomes.
Lei et al. (Mon,) studied this question.