Noncanonical role of astrocytic mitochondrial Cx43: suppressing IDH3α to sustain glycolytic homeostasis against depression

Depression remains a pervasive global health challenge, compounded by limited therapeutic efficacy that is partly attributed to incompletely understood metabolic underpinnings. In this study, we reveal a noncanonical mitochondrial function of astrocytic connexin 43 (Cx43) whereby it directly inhibits isocitrate dehydrogenase 3α (IDH3α), thereby sustaining glycolytic metabolism and lactate production essential for neuronal excitability. Astrocyte-specific deletion of Cx43 in the prelimbic cortex (PrL) recapitulates hallmark depressive phenotypes, characterized by reduced lactate synthesis, diminished neuronal excitability, and depressive-like behaviors. Loss of Cx43 enhances IDH3α activity, prompting a metabolic reprogramming from aerobic glycolysis toward oxidative phosphorylation (OXPHOS) driven by glutamine-fueled anaplerosis, resulting in suppressed glucose uptake and decreased lactate output. This metabolic impairment restricts astrocytic lactate supply, depriving neurons of a critical energetic substrate. Importantly, this reprogramming occurs independently of gap junction intercellular communication, as demonstrated using a channel function-deficient dominant-negative Cx43 mutant. Restoration of mitochondrial Cx43 in astrocytes rescues neuronal excitability and ameliorates depressive-like phenotypes. Collectively, our findings identify mitochondrial Cx43 as a vital regulator of IDH3α activity, essential for astrocyte-neuron metabolic coupling, and highlight a promising target for therapeutic intervention in depression.