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Control of type I interferon-induced cell death by Orai1-mediated calcium entry in T cells
Chanyu Yue1, Jonathan Soboloff, Ana M Gamero
1Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
Abstract:
Store-operated Ca(2+) entry (SOCE) is an essential process in T cell activation. SOCE is controlled by the Ca(2+) release-activated Ca(2+) (CRAC) channel encoded by the gene Orai1 that is expressed on the plasma membrane and activated by STIM1 when ER Ca(2+) stores are depleted. Our earlier work showed that a somatic T-cell line Jurkat mutant H123 bearing a defect in Ca(2+) signaling was susceptible to the apoptotic effects of type I interferons (IFN-α/β). The nature of the mutation and whether this mutation was linked to IFN-α/β apoptotic susceptibility was unknown. Here we show that H123 cells lacked Orai1 and exhibit reduced STIM1 protein. Reconstitution of both Orai1 and STIM1 in H123 cells rescued SOCE in response to thapsigargin and ionomycin and abrogated IFN-α/β-induced apoptosis. Reciprocally, overexpression of the dominant negative Orai1-E106A in either parental Jurkat cells or an unrelated human T cell line (CEM391) inhibited SOCE and led to sensitization to IFN-α/β-induced apoptosis. Furthermore, we showed that the Ca(2+) response pathway antagonized the IFN-α/β -induced transcriptional responses; in the absence of SOCE, this negative regulatory effect was lost. However, the inhibitory effect of Ca(2+) on type I IFN-induced gene transcription was diminished by pharmacological inhibition of NF-κB in cells with intact SOCE. Our findings reveal an unexpected and novel regulatory crosstalk mechanism between type I IFNs and store-operated Ca(2+) signaling pathways mediated at least in part by NF-κB activity with significant clinical implications to both viral and tumor immunology.
Insights
Store-operated Ca(2+) entry (SOCE) is crucial for T cell activation and prevents apoptosis from type I interferons (IFN-α/β). Loss of SOCE sensitizes cells to IFN-α/β-induced apoptosis, revealing a novel crosstalk mechanism.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Store-operated Ca(2+) entry (SOCE) is vital for T cell activation, regulated by Orai1 channels and STIM1. Jurkat mutant H123 cells with defective Ca(2+) signaling are susceptible to type I interferons (IFN-α/β).
- The specific mutation in H123 cells and its link to IFN-α/β sensitivity were previously unknown.
Purpose of the Study:
- To investigate the genetic basis of the Ca(2+) signaling defect in H123 cells.
- To determine the relationship between SOCE, Orai1, STIM1, and susceptibility to type I IFN-induced apoptosis.
- To elucidate the molecular crosstalk between Ca(2+) signaling and type I IFN responses.
Main Methods:
- Characterization of H123 T-cell mutant.
- Genetic reconstitution of Orai1 and STIM1 in H123 cells.
- Overexpression of dominant-negative Orai1 in Jurkat and CEM391 cells.
- Assessment of SOCE using thapsigargin and ionomycin.
- Analysis of IFN-α/β-induced apoptosis and transcriptional responses.
- Pharmacological inhibition of NF-κB.
Main Results:
- H123 cells lack Orai1 and have reduced STIM1 protein, confirming a defect in SOCE.
- Reconstitution of Orai1 and STIM1 restored SOCE and abrogated IFN-α/β-induced apoptosis in H123 cells.
- Inhibition of SOCE in parental Jurkat and CEM391 cells sensitized them to IFN-α/β-induced apoptosis.
- The Ca(2+) response pathway normally antagonizes type I IFN-induced transcription, an effect lost without SOCE.
- NF-κB activity partially mediates the inhibitory effect of Ca(2+) on type I IFN-induced gene transcription.
Conclusions:
- The H123 mutation disrupts Orai1 expression, leading to impaired SOCE and increased susceptibility to type I IFN-induced apoptosis.
- A novel regulatory crosstalk exists between type I IFNs and SOCE, partly mediated by NF-κB.
- This crosstalk has significant implications for viral and tumor immunology, highlighting the role of Ca(2+) signaling in immune responses.
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