Restoration of the GTPase activity and cellular interactions of Gα_o mutants by Zn²⁺ in <i>GNAO1</i> encephalopathy models.

Abstract

De novo point mutations in <i>GNAO1</i>, gene encoding the major neuronal G protein Gα_o, have recently emerged in patients with pediatric encephalopathy having motor, developmental, and epileptic dysfunctions. Half of clinical cases affect codons Gly²⁰³, Arg²⁰⁹, or Glu²⁴⁶; we show that these mutations accelerate GTP uptake and inactivate GTP hydrolysis through displacement Gln²⁰⁵ critical for GTP hydrolysis, resulting in constitutive GTP binding by Gα_o. However, the mutants fail to adopt the activated conformation and display aberrant interactions with signaling partners. Through high-throughput screening of approved drugs, we identify zinc pyrithione and Zn²⁺ as agents restoring active conformation, GTPase activity, and cellular interactions of the encephalopathy mutants, with negligible effects on wild-type Gα_o. We describe a <i>Drosophila</i> model of <i>GNAO1</i> encephalopathy where dietary zinc restores the motor function and longevity of the mutant flies. Zinc supplements are approved for diverse human neurological conditions. Our work provides insights into the molecular etiology of <i>GNAO1</i> encephalopathy and defines a potential therapy for the patients.