ARF GTPases activate Salmonella effector SopF to ADP-ribosylate host V-ATPase and inhibit endomembrane damage-induced autophagy

Selective autophagy helps eukaryotes to cope with endogenous dangers or foreign invaders; its initiation often involves membrane damage. By studying a Salmonella effector SopF, we recently identified the vacuolar ATPase (V-ATPase)-ATG16L1 axis that initiates bacteria-induced autophagy. Here we show that SopF is an ADP-ribosyltransferase specifically modifying Gln124 of ATP6V0C in V-ATPase. We identify GTP-bound ADP-ribosylation factor (ARF) GTPases as a cofactor required for SopF functioning. Crystal structures of SopF-ARF1 complexes not only reveal structural basis of SopF ADP-ribosyltransferase activity but also a unique effector-binding mode adopted by ARF GTPases. Further, the N terminus of ARF1, although dispensable for high-affinity binding to SopF, is critical for activating SopF to modify ATP6V0C. Moreover, lysosome or Golgi damage-induced autophagic LC3 activation is inhibited by SopF or Q124A mutation of ATP6V0C, thus also mediated by the V-ATPase-ATG16L1 axis. In this process, the V-ATPase functions to sense membrane damages, which can be uncoupled from its proton-pumping activity. The authors show that the Salmonella effector SopF is activated by ARF GTPases to ADP-ribosylate a glutamine in the V-ATPase subunit ATP6V0C, blocking xenophagy or other selective autophagy types independent of proton-pumping activity.

Automated summary

Selective autophagy is an important mechanism for eukaryotes to defend against internal dangers or foreign invaders. This study reveals that the Salmonella effector SopF initiates bacteria-induced autophagy by modifying the V-ATPase subunit ATP6V0C and that ARF GTPases play a role in this process. Crystal structures of the SopF-ARF1 complexes provide insights into the ADP-ribosyltransferase activity of SopF and the unique effector-binding mode of ARF GTPases.