Abstract
Efficient immune responses require Ca2+ fluxes across ORAI1 channels during engagement of T cell receptors (TCR) at the immune synapse (IS) between T cells and antigen presenting cells. Here, we show that ZDHHC20-mediated S-acylation of the ORAI1 channel at residue Cys143 promotes TCR recruitment and signaling at the IS. Cys143 mutations reduced ORAI1 currents and store-operated Ca2+ entry in HEK-293 cells and nearly abrogated long-lasting Ca2+ elevations, NFATC1 translocation, and IL-2 secretion evoked by TCR engagement in Jurkat T cells. The acylation-deficient channel remained in cholesterol-poor domains upon enforced ZDHHC20 expression and was recruited less efficiently to the IS along with actin and TCR. Our results establish S-acylation as a critical regulator of ORAI1 channel trafficking and function at the IS and reveal that ORAI1 S-acylation enhances TCR recruitment to the synapse.
Highlights
The development of efficient immune responses by T lymphocytes require long-lasting Ca2+ elevations mediated by the plasma membrane (PM) channel ORAI1 during engagement of T cell receptors (TCR) at the immune synapse (IS) forming between T cells and antigen-p resenting cells (Lioudyno et al, 2008; Cahalan and Chandy, 2009; Hartzell et al, 2016)
We show that S-a cylation of ORAI1 at a single cysteine residue enhances the affinity of the channel for cholesterol-rich lipid microdomains and promotes its trapping at the immune synapse, thereby enabling the local Ca2+ fluxes that control the activation of Jurkat T cells
Using acyl-PEG exchange, palmitate incorporation, and mutagenesis, we show that ORAI1 can be chemically modified by S-a cylation and identify the acylation site as Cys143 on the cytosolic rim of the second TM domain
Summary
The development of efficient immune responses by T lymphocytes require long-lasting Ca2+ elevations mediated by the plasma membrane (PM) channel ORAI1 during engagement of T cell receptors (TCR) at the immune synapse (IS) forming between T cells and antigen-p resenting cells (Lioudyno et al, 2008; Cahalan and Chandy, 2009; Hartzell et al, 2016). Following TCR engagement, the Ca2+ depletion of the endoplasmic reticulum (ER) causes the ER-b ound Ca2+ sensors STIM1-2 to oligomerise and to accumulate in ER-P M junctions (Zhang et al, 2005; Liou et al, 2005), where they trap and gate the Ca2+-release-activated (CRAC) ORAI1 channel (Vig et al, 2006). Recent studies have revealed the structural rearrangements occurring within ORAI1 as STIM1.
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