A pathogenic human Orai1 mutation unmasks STIM1-independent rapid inactivation of Orai1 channels
- Northwestern University, United States
Abstract
Ca2+ release-activated Ca2+ (CRAC) channels are activated by direct physical interactions between Orai1, the channel protein, and STIM1, the endoplasmic reticulum Ca2+ sensor. A hallmark of CRAC channels is fast Ca2+-dependent inactivation (CDI) which provides negative feedback to limit Ca2+ entry through CRAC channels. Although STIM1 is thought to be essential for CDI, its molecular mechanism remains largely unknown. Here, we examined a poorly understood gain-of-function (GOF) human Orai1 disease mutation, L138F, that causes tubular aggregate myopathy. Through pairwise mutational analysis, we determine that large amino acid substitutions at either L138 or the neighboring T92 locus located on the pore helix evoke highly Ca2+-selective currents in the absence of STIM1. We find that the GOF phenotype of the L138 pathogenic mutation arises due to steric clash between L138 and T92. Surprisingly, strongly activating L138 and T92 mutations showed CDI in the absence of STIM1, contradicting prevailing views that STIM1 is required for CDI. CDI of constitutively open T92W and L138F mutants showed enhanced intracellular Ca2+ sensitivity, which was normalized by re-adding STIM1 to the cells. Truncation of the Orai1 C-terminus reduced T92W CDI indicating a key role for the Orai1 C-terminus for CDI. Overall, these results identify the molecular basis of a disease phenotype with broad implications for activation and inactivation of Orai1 channels.
Data availability
Source Data files containing the numerical data used in Figures 1-8 and the associated Supplementary figures have been uploaded.
Article and author information
Author details
Priscilla S-W Yeung
Funding
National Institutes of Health (R01 NS057499)
- Murali Prakriya
National Institutes of Health (R01 NS115508)
- Murali Prakriya
National Institutes of Health (F31NS101830)
- Priscilla S-W Yeung
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2023, Yeung et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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A pathogenic human Orai1 mutation unmasks STIM1-independent rapid inactivation of Orai1 channels
eLife 12:e82281.
https://doi.org/10.7554/eLife.82281
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