Abstract
T cell effector functions require sustained calcium influx. However, the signaling and phenotypic consequences of non-specific sodium permeation via calcium channels remain unknown. α-SNAP is a crucial component of Orai1 channels, and its depletion disrupts the functional assembly of Orai1 multimers. Here we show that α-SNAP hypomorph, hydrocephalus with hopping gait, Napa(hyh/hyh) mice harbor significant defects in CD4 T cell gene expression and Foxp3 regulatory T cell (Treg) differentiation. Mechanistically, TCR stimulation induced rapid sodium influx in Napa(hyh/hyh) CD4 T cells, which reduced intracellular ATP, [ATP](i). Depletion of [ATP](i) inhibited mTORC2 dependent NFκB activation in Napa(hyh/hyh) cells but ablation of Orai1 restored it. Remarkably, TCR stimulation in the presence of monensin phenocopied the defects in Napa(hyh/hyh) signaling and Treg differentiation, but not IL-2 expression. Thus, non-specific sodium influx via bonafide calcium channels disrupts unexpected signaling nodes and may provide mechanistic insights into some divergent phenotypes associated with Orai1 function.