Conformational surveillance of Orai1 by a rhomboid intramembrane protease prevents inappropriate CRAC channel activation

Mol Cell. 2021 Dec 2;81(23):4784-4798.e7. doi: 10.1016/j.molcel.2021.10.025. Epub 2021 Nov 19.

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.

Keywords: CRAC channel; Orai1; RHBDL2; T cell; calcium; rhomboid protease; signalling; transmembrane.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism
  • Calcium Channels / chemistry
  • Calcium Signaling / physiology
  • Cell Membrane / metabolism
  • Computational Biology
  • Drosophila melanogaster
  • HEK293 Cells
  • Humans
  • Ion Channel Gating
  • Lymphocyte Activation
  • Membrane Proteins / metabolism
  • Mutation
  • ORAI1 Protein / chemistry*
  • Peptide Hydrolases / chemistry*
  • Protein Binding
  • Protein Conformation
  • Serine Endopeptidases / metabolism*
  • Signal Transduction
  • Stochastic Processes

Substances

  • Calcium Channels
  • Membrane Proteins
  • ORAI1 Protein
  • ORAI1 protein, human
  • Orai1 protein, mouse
  • Peptide Hydrolases
  • RHBDL2 protein, mouse
  • Serine Endopeptidases
  • RHBDL2 protein, human
  • Calcium