L-type voltage-gated Ca²⁺ channels control T cell killing via non-canonical Hedgehog signalling

Cytotoxic CD8⁺ T lymphocytes (CTLs) efficiently eliminate infected and cancerous cells throughout the body. T cell receptor (TCR)-induced Hedgehog signalling contributes to CTL-mediated killing, but how the pathway is activated downstream of the TCR is unknown. Here, we show that extracellular calcium (Ca²⁺) flux through L-type voltage-gated Ca²⁺ (Ca_v1) channels at the plasma membrane downstream of the TCR drives induction of the Hedgehog transcription factor Gli1, which is important for CTL killing in vitro and in vivo. This previously unknown non-canonical Hedgehog pathway is independent of canonical signalling and represents a primary mechanism of Gli1 induction in naive CD8⁺ T cells, whereas CTLs can also activate Gli1 via MAPK. We further show that Ca_v1 channel-controlled Gli1 induction is functionally important for CTL killing in mice and humans and other cytotoxic lymphocytes. Notably, killing capacity can be amplified using a small molecule Ca_v1 agonist or by overexpressing a gain-of-function Ca_v1 subunit. These findings suggest a strategy to improve cytotoxic lymphocyte function in the clinic, including in CAR T cell therapy.