Antidepressant Actions of Ketamine Mediated by the Mechanistic Target of Rapamycin, Nitric Oxide, and Rheb

The weeks/months it takes for traditional antidepressants to act pose an obstacle in the management of depression. Ketamine's prompt and sustained antidepressant effects constitute a major advance. Multiple studies implicate glutamatergic signaling to protein synthesis machinery and synapse formation in ketamine's antidepressant effects. Here we review evidence linking ketamine to glutamate receptor sub-types and protein homeostasis. We describe a signaling cascade wherein nitric oxide drives the formation of a ternary protein complex comprised of glyceraldehyde 3-phosphate dehydrogenase, seven in absentia homolog 1, and Ras homolog enriched in brain downstream of the glutamate N-methyl-D- aspartate receptor. Seven in absentia homolog 1 ubiquitylates and degrades Ras homolog enriched in brain leading to inhibition of mechanistic target of rapamycin. Ketamine inhibits this molecular cascade leading to activation of mechanistic target of rapamycin and, in turn, to antidepressant actions.