Syntaxin11 Deficiency Inhibits CRAC Channel Priming To Suppress Cytotoxicity And Gene Expression In FHLH4 Patient T
Sritama Datta1, Abhikarsh Gupta1, Kunal Mukesh Jagetiya1
1Tata Institute of Fundamental Research, Hyderabad, India.
Abstract:
CRAC channels enable calcium entry from the extracellular space in response to a variety of stimuli and are crucial for gene expression and granule exocytosis in lymphocytes. Here we find that Syntaxin11, a Q-SNARE, associated with FHLH4 disease in human patients, directly binds Orai1, the pore forming subunit of CRAC channels. Syntaxin11 depletion strongly inhibited SOCE, CRAC currents, IL-2 expression and cytotoxicity in cell lines and FHLH4 patient T lymphocytes. Constitutively active H134 Orai1 mutant completely reconstituted calcium entry in Syntaxin11 depleted cells and the defects of granule exocytosis as well as gene expression could be bypassed by ionomycin induced calcium influx in FHLH4 T lymphocytes. Our data reveal a Syntaxin11 induced pre-activation state of Orai which is necessary for its subsequent coupling and gating by the endoplasmic reticulum resident Stim protein. We propose that ion channel regulation by specific SNAREs is a primary and conserved function which may have preceded their role in vesicle fusion.
Insights
Syntaxin11 directly binds Orai1, regulating calcium entry crucial for lymphocyte function. Its absence impairs immune responses, but specific Orai1 mutations can restore function, revealing a novel role for SNAREs in ion channel regulation.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Calcium-selective channels (CRAC) are vital for lymphocyte activation, controlling gene expression and granule release.
- Syntaxin11 is linked to FHLH4 disease, but its precise role in cellular function remains unclear.
Purpose of the Study:
- To investigate the interaction between Syntaxin11 and Orai1, the pore-forming subunit of CRAC channels.
- To elucidate the functional consequences of Syntaxin11 deficiency on CRAC channel activity and lymphocyte function.
Main Methods:
- Co-immunoprecipitation to assess Syntaxin11-Orai1 binding.
- Electrophysiology to measure CRAC currents (SOCE).
- Analysis of IL-2 expression, cytotoxicity, and granule exocytosis in cell lines and patient-derived T lymphocytes.
Main Results:
- Syntaxin11 directly binds to Orai1.
- Syntaxin11 depletion significantly inhibits SOCE, CRAC currents, IL-2 production, and cytotoxicity.
- A constitutively active Orai1 mutant rescues calcium entry and bypasses Syntaxin11-dependent defects.
- Syntaxin11 appears to induce a pre-activation state in Orai1, facilitating STIM protein coupling and gating.
Conclusions:
- Syntaxin11 plays a critical, previously unrecognized role in regulating CRAC channel function in lymphocytes.
- This interaction highlights a novel mechanism for controlling calcium influx essential for immune cell activation.
- SNARE-mediated regulation of ion channels may represent a fundamental function preceding their role in membrane fusion.
