<i>Coxiella</i> effector protein CvpF subverts RAB26-dependent autophagy to promote vacuole biogenesis and virulence

<i>Coxiella burnetii</i>, the etiological agent of the zoonosis Q fever, replicates inside host cells within a large vacuole displaying autolysosomal characteristics. The development of this compartment is mediated by bacterial effectors, which interfere with a number of host membrane trafficking pathways. By screening a <i>Coxiella</i> transposon mutant library, we observed that transposon insertions in <i>cbu0626</i> led to intracellular replication and vacuole biogenesis defects. Here, we demonstrate that CBU0626 is a novel member of the <i>Coxiella</i> vacuolar protein (Cvp) family of effector proteins, which is translocated by the Dot/Icm secretion system and localizes to vesicles with autolysosomal features as well as <i>Coxiella</i>-containing vacuoles (CCVs). We thus renamed this effector CvpF for <i>Coxiella</i> vacuolar protein F. CvpF specifically interacts with the host small GTPase RAB26, leading to the recruitment of the autophagosomal marker MAP1LC3B/LC3B (microtubule associated protein 1 light chain 3 beta) to CCVs. Importantly, <i>cvpF</i>::Tn mutants were highly attenuated compared to wild-type bacteria in the SCID mouse model of infection, highlighting the importance of CvpF for <i>Coxiella</i> virulence. These results suggest that CvpF manipulates endosomal trafficking and macroautophagy/autophagy induction for optimal <i>C. burnetii</i> vacuole biogenesis. <b>Abbreviations:</b> ACCM: acidified citrate cystein medium; AP: adaptor related protein complex; CCV: <i>Coxiella</i>-containing vacuole; Cvp: <i>Coxiella</i> vacuolar protein; GDI: guanosine nucleotide dissociation inhibitor; GDF: GDI dissociation factor; GEF: guanine exchange factor; LAMP1: lysosomal associated membrane protein 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MTORC1: mechanistic target of rapamycin kinase MTOR complex 1; PBS: phosphate-buffered saline; PMA: phorbol myristate acetate; SQSTM1/p62: sequestosome 1; WT: wild-type.