Ric8 proteins as the neomorphic partners of G alpha o in GNAO1 encephalopathies

GNAO1 mutated in pediatric encephalopathies encodes the major neuronal G-protein Go. Of >40 pathogenic mutations, most are single amino acid substitutions spreading across Go sequence. We perform extensive characterization of Go mutants showing abnormal GTP uptake and hydrolysis, and deficiencies to bind G{beta}{gamma} and RGS19. Plasma membrane localization of Go is decreased for a subset of mutations that leads to epileptic manifestations. Pathogenic mutants massively gain interaction with Ric8A/B proteins, delocalizing them from cytoplasm to Golgi. Being general G-subunit chaperones and binding multiple other proteins, Ric8A/B likely mediate the disease dominance when engaging in neomorphic interactions with pathogenic Go. As the strength of Go-Ric8B interactions correlates with disease severity, our study further identifies an efficient biomarker and predictor for clinical manifestations in GNAO1 encephalopathies. One-Sentence SummaryNeomorphic mutations in Go gain dominant interactions with Ric8A/B, correlating with severity in pediatric encephalopathies.