Cav3.1 is a neuronal leucine sensor that mediates satiety and weight loss in response to dietary protein.

Dietary protein promotes satiety and weight loss, yet how appetite-regulating neurons sense dietary protein remains poorly understood. Here, we show that Cacna1g, which encodes the T-type voltage-gated calcium channel Cav3.1, is enriched in hypothalamic leucine-sensing neurons and mediates neuronal leucine sensing. Pharmacological inhibition of Cav3.1 blunts leucine-induced activation of pro-opiomelanocortin (POMC) neurons in cultured neurons and brain slices, thereby suppressing the anorectic response to hypothalamic leucine in vivo. Genetic deletion of Cacna1g in POMC neurons abolishes the appetite- and weight-suppressive effects of high-protein feeding. Mechanistically, leucine binds a hydrophobic pocket of Cav3.1 and lowers its threshold for voltage-dependent activation. Finally, pharmacological activation of mediobasal hypothalamic Cav3.1 promotes weight loss in diet-induced obese mice and potentiates responses to anorectic agents, including liraglutide. Together, these findings establish hypothalamic Cav3.1 as a neuronal leucine sensor and nominate it as a tractable target for anti-obesity therapy.