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Nat Commun. 2015 Apr 21;6:6899. doi: 10.1038/ncomms7899.

A STIM2 splice variant negatively regulates store-operated calcium entry.

Author information

1
Molecular Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, Building 48, Homburg 66421, Germany.
2
1] Molecular Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, Building 48, Homburg 66421, Germany [2] Department of Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, Homburg 66421, Germany.
3
Center for Bioinformatics, Saarland University, Campus E2 1, R. 315, PO Box 151150, Saarbrücken 66041, Germany.
4
Department of Medical Biochemistry and Molecular Biology, Saarland University, Building 44, Homburg 66421, Germany.

Abstract

Cellular homeostasis relies upon precise regulation of Ca(2+) concentration. Stromal interaction molecule (STIM) proteins regulate store-operated calcium entry (SOCE) by sensing Ca(2+) concentration in the ER and forming oligomers to trigger Ca(2+) entry through plasma membrane-localized Orai1 channels. Here we characterize a STIM2 splice variant, STIM2.1, which retains an additional exon within the region encoding the channel-activating domain. Expression of STIM2.1 is ubiquitous but its abundance relative to the more common STIM2.2 variant is dependent upon cell type and highest in naive T cells. STIM2.1 knockdown increases SOCE in naive CD4(+) T cells, whereas knockdown of STIM2.2 decreases SOCE. Conversely, overexpression of STIM2.1, but not STIM2.2, decreases SOCE, indicating its inhibitory role. STIM2.1 interaction with Orai1 is impaired and prevents Orai1 activation, but STIM2.1 shows increased affinity towards calmodulin. Our results imply STIM2.1 as an additional player tuning Orai1 activation in vivo.

PMID:
25896806
PMCID:
PMC4411291
DOI:
10.1038/ncomms7899
[Indexed for MEDLINE]
Free PMC Article
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