RHOD mediates ATG9A trafficking to promote autophagosome formation during autophagy in cancer.

ATG9A is a transmembrane protein essential for macroautophagy/autophagy that drives autophagosome formation by delivering essential proteins and lipids to the phagophore through vesicle trafficking. Here, we demonstrate that the atypical Rho GTPase RHOD is required for ATG9A trafficking and stimulates autophagosome formation. Upon starvation, RHOD interacted with ATG9A and accompanied ATG9A trafficking from the Golgi toward phagophores. In addition, starvation-induced high levels of RHOD resulted in Golgi fragmentation to further promote ATG9A vesicle export from the trans-Golgi network to the peripheral region. Loss of RHOD suppressed ATG9A trafficking and reduced the distribution of ATG9A on the phagophore. Moreover, WHAMM (WASP homolog associated with actin, golgi membranes and microtubules) forms a complex with RHOD and participates in this process in a RHOD-dependent manner. Importantly, RHOD mutants, which lack the exon II-containing effector region motif that is required for ATG9A binding or lack the CAAX box that is responsible for membrane targeting, fail to stimulate ATG9A trafficking and autophagosome formation. Furthermore, RHOD plays a distinct suppressor role in tumor development, partly associated with its regulatory effect on autophagy. These findings reveal the important roles of RHOD in autophagy and tumor development.Abbreviation: ATG9A: autophagy related 9A; BafA1: bafilomycin A₁; BiFC: bimolecular fluorescence complementation; co-IP: co-immunoprecipitation; EBSS: Earle's balanced salt solution; FM: full culture medium; KO: knockout; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; PUP-IT: pupylation-based interaction tagging; RHOD: ras homolog family member D; SQSTM1: sequestosome 1; TGN: trans-Golgi network; VC: Venus C-terminal; VN: Venus N-terminal; WHAMM: WASP homolog associated with actin, golgi membranes and microtubules; WIPI2: WD repeat domain, phosphoinositide interacting 2; WT: wild-type; 3-MA: phosphatidylinositol 3-kinase (PtdIns3K) inhibitor 3-methyladenine.