Orai1α and Orai1β more potently promote NFAT activation and transcription than Orai2 and Orai3
Year: 2026
Type: preprint
Abstract: The Ca²⁺ release-activated Ca²⁺ (CRAC) channel mediates store-operated calcium entry (SOCE), a ubiquitous pathway essential for many cell types, including immune cells. Three Orai (Orai1, Orai2, Orai3) proteins constitute the plasma membrane pore-forming units of CRAC channels that are activated by the endoplasmic reticulum (ER) Ca 2+ -sensing STIM1 and STIM2 proteins when ER Ca 2+ stores are depleted. Orai1/2/3 are differentially expressed across primary cells with discernible differences in their structures and biophysical properties. Further, Orai1 has two alternatively translated isoforms: the long mammalian-specific Orai1α and the 63-residue shorter Orai1β, which is evolutionarily older and conserved across vertebrates. Whether Orai1α/1β/2/3 at native expression levels produce unique cytosolic Ca²⁺ signatures that bias transcriptional responses through effectors like NFAT is unclear. Here we used HEK293 cells engineered to express one native Orai isoform and show that all Orai isoforms couple to NFAT1 and NFAT4 induction. The magnitude of NFAT1/4 induction tracked the magnitude of SOCE, with the following profile: Orai1β>Orai1α>>Orai2>Orai3. Near-native ectopic expression of either Orai1α or Orai1β in primary murine Orai1 −/− CD4⁺ T cells restored SOCE, NFAT activation, cytokine production and promoted near identical transcriptional responses enriched for immune activation pathways. An analysis of genetic and clinical data of human individuals showed that homozygous null mutations selectively abolishing Orai1α are not associated with disease resembling CRAC channelopathy. Primary T cells from individuals homozygous or heterozygous for an Orai1α null mutation showed enhanced, rather than impaired, SOCE and NFAT induction. Collectively, our data indicate that Orai isoforms regulate NFAT activation and downstream transcription primarily through the magnitude of SOCE they support, with Orai1α and Orai1β being the most potent isoforms coupling SOCE to NFAT responses.
Authors: Ahmed Emam Abdelnaby, Yin-Hu Wang, J. Cory Benson, Isagani Perez, Boheng Shen, Maxwell McDermott, Miki Jishage, Amal T. Elhaw, Silvia Cruz-Rangel, Raphael Courjaret, Abdelaziz Belkadi, Fang Yu, Douglas S. Prado, Shuai Yuan, Ping Xin, Adam C. Straub, Francisco J. Schopfer, Nadine Hempel, William F. Hawse, David B. Beck, Khaled Machaca, Stefan Feske, Mohamed Trebak
Language: English
Topic: Ion Channels and Receptors
Subfield: Sensory Systems
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7168221703