Ca Signaling Augmented by ORAI1 Trafficking Regulates the Pathogenic State of Effector T Cells.

Activation of the Ca release-activated Ca (CRAC) channel is crucial for T cell functions. It was recently shown that naked cuticle homolog 2 (NKD2), a signaling adaptor molecule, orchestrates trafficking of ORAI1, a pore subunit of the CRAC channels, to the plasma membrane for sustained activation of the CRAC channels. However, the physiological role of sustained Ca entry via ORAI1 trafficking remains poorly understood. Using NKD2 as a molecular handle, we show that ORAI1 trafficking is crucial for sustained Ca entry and cytokine production, especially in inflammatory Th1 and Th17 cells. We find that murine T cells cultured under pathogenic Th17-polarizing conditions have higher Ca levels that are NKD2-dependent than those under nonpathogenic conditions. In vivo, deletion of alleviated clinical symptoms of experimental autoimmune encephalomyelitis in mice by selectively decreasing effector T cell responses in the CNS. Furthermore, we observed a strong correlation between NKD2 expression and proinflammatory cytokine production in effector T cells. Taken together, our findings suggest that the pathogenic effector T cell response demands sustained Ca entry supported by ORAI1 trafficking.