Harnessing metabolic control for synaptic stability: REST/NRSF links glycolytic inhibition to excitatory neurotransmission.

Under resting conditions most neuronal ATP is produced through mitochondrial oxidative phosphorylation, whereas glycolysis becomes more important during intense neuronal firing. Recent studies suggest that inhibiting glycolysis plays a key role in regulating seizure-related hyperactivity, with the epigenetic modulator REST/NRSF being activated when glycolysis inhibition lowers the NADH/NAD⁺ ratio. Our previous research has shown that REST/NRSF initiates homeostatic processes to counteract neuronal hyperactivity by regulating both firing and synaptic activities. However, the exact mechanism through which the metabolic activation of REST/NRSF controls neuronal excitability is still unknown. Here, we studied the role of REST/NRSF in the effects of glycolysis inhibition on hippocampal neuron activity. Treatment with 2-deoxy-d-glucose (2DG) decreased the NADH/NAD⁺ ratio, increased REST/NRSF expression, and promoted its nuclear translocation. Although GABAergic inhibitory inputs and the firing properties of both excitatory and inhibitory neurons were unaffected by 2DG, the amplitude of evoked EPSCs (eEPSCs) and miniature EPSCs (mEPSCs) was reduced in a REST/NRSF-dependent manner. This effect was associated with a REST/NRSF-dependent reduction in the size of GluA2-positive puncta and a decrease in GluA2 expression in the absence of changes in the density of excitatory synapses. These effects provide a mechanistic basis for the significant reduction in network firing and bursting activity observed when the hippocampal network was treated with 2DG. These findings highlight a role of the REST/NRSF-dependent pathway in the 2DG-mediated downregulation of excitatory inputs, a mechanism that contributes to neuronal network stability, strengthening the homeostatic defences against hyperactivity. KEY POINTS: Reducing glucose metabolism with 2-deoxy-d-glucose (2DG) lowers the cell's energy balance and increases the levels of a gene regulator called REST/NRSF. REST/NRSF then moves into the nucleus, where it controls the activity of genes linked to nerve cell communication. 2DG weakens the strength of signals between excitatory nerve cells, without affecting inhibitory signals or the basic ability of neurons to fire. This effect depends in part on REST/NRSF, which reduces the amount and size of GluA2-containing AMPA receptors at excitatory synapses, without altering the overall number of excitatory contacts. These findings suggest that blocking glucose metabolism activates a protective response that stabilizes brain networks, which could help control seizures in epilepsy.