GPR143 mediates virus-induced cytoplasmic vacuolation through the MKK6–p38 pathway in teleosts

Cytoplasmic vacuolization is a prominent cytopathic feature of many viral infections, yet the host pathways that convert viral replication into vacuolar cell injury remain poorly characterized. Nervous necrosis virus (NNV) produces extensive vacuolation in the brain during infection, providing a tractable model for dissecting virus-associated vacuolar injury in the central nervous system. G protein-coupled receptors (GPCRs) have been implicated in autophagosome regulation and vacuole formation, with GPR143 previously identified as a candidate host factor for resistance to red-spotted grouper nervous necrosis virus (RGNNV) in groupers. In the present study, orange-spotted grouper (Epinephelus coioides) and RGNNV were used to define the contribution of GPR143 to virus-induced neural vacuolation. Results demonstrated that GPR143 promoted RGNNV-induced cytoplasmic vacuolization by enhancing autophagosome–lysosome fusion. Mechanistically, RGNNV infection increased the interaction between GPR143 and MKK6, which promoted p38 phosphorylation and engaged mammalian target of rapamycin (mTOR) pathway signaling to drive autophagosome–lysosome fusion and vacuole formation. Finally, the zebrafish with GPR143 knockout confirmed that the absence of GPR143 significantly reduces brain vacuolation and fry mortality. These results indicated that GPR143 directs virus-induced cell vacuolation via the MKK6–p38 pathway in teleost. Our study reveals a novel pathway by which viruses cause vacuolation in vertebrates.