Yeast TLDc domain-containing proteins control assembly and subcellular localization of the V-ATPase

Yeast vacuoles, equivalent to lysosomes in other eukaryotes, are important acidic degradative organelles as well as storage compartments and signaling hubs. To perform these functions, they rely on important protein complexes, including the V-ATPase, responsible for organelle acidification. In this study, we used cross-linking mass spectrometry to characterize the protein complexes of isolated vacuoles. We were able to detect many known protein-protein interactions, including known protein complexes, as well as undescribed ones. Among these, we identified the uncharacterized TLDc domain-containing protein Rtc5 as a novel interactor of the V-ATPase. We show that Rtc5 localizes to the vacuole membrane depending on N-myristoylation and on its interactions with the V-ATPase. We further analyzed the influence of this protein, and the second yeast TLDc domain-containing protein, Oxr1, on V-ATPase function. We find that both Rtc5 and Oxr1 promote the disassembly of the vacuolar V-ATPase in vivo, counteracting the role of the assembly chaperone, the RAVE complex. Finally, Oxr1 is necessary for the retention in the late Golgi complex of an organelle-specific subunit of the V-ATPase. Collectively, our results shed light on the in vivo roles of yeast TLDc domain-containing proteins in relation to the V-ATPase, highlighting the multifaceted regulation of this crucial protein complex.