Conformational surveillance of Orai1 by a rhomboid intramembrane protease prevents inappropriate CRAC channel activation.
Mol Cell 2021;
81:4784-4798.e7. [PMID:
34800360 PMCID:
PMC8657799 DOI:
10.1016/j.molcel.2021.10.025]
[Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/14/2021] [Accepted: 10/26/2021] [Indexed: 12/19/2022]
Abstract
Calcium influx through plasma membrane calcium release-activated calcium (CRAC) channels, which are formed of hexamers of Orai1, is a potent trigger for many important biological processes, most notably in T cell-mediated immunity. Through a bioinformatics-led cell biological screen, we have identified Orai1 as a substrate for the rhomboid intramembrane protease RHBDL2. We show that RHBDL2 prevents stochastic calcium signaling in unstimulated cells through conformational surveillance and cleavage of inappropriately activated Orai1. A conserved disease-linked proline residue is responsible for RHBDL2’s recognizing the active conformation of Orai1, which is required to sharpen switch-like signaling triggered by store-operated calcium entry. Loss of RHBDL2 control of CRAC channel activity causes severe dysregulation of downstream CRAC channel effectors, including transcription factor activation, inflammatory cytokine expression, and T cell activation. We propose that this surveillance function may represent an ancient activity of rhomboid proteases in degrading unwanted signaling proteins.
A screen for transmembrane substrates of the rhomboid intramembrane protease RHBDL2
RHBDL2 cleaves the CRAC channel protein Orai1 when it is inappropriately activated
Conformational change in these calcium channels is recognized by RHBDL2
An Orai1 mutant that cannot be cleaved by RHBDL2 causes a human disease syndrome
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