STIM1 interacts with termini of Orai channels in a sequential manner

J Cell Sci. 2020 Apr 29;133(8):jcs239491. doi: 10.1242/jcs.239491.


Store-operated Ca2+ entry (SOCE) is critical for numerous Ca2+-related processes. The activation of SOCE requires engagement between stromal interaction molecule 1 (STIM1) molecules on the endoplasmic reticulum and Ca2+ release-activated channel (CRAC) Orai on the plasma membrane. However, the molecular details of their interactions remain elusive. Here, we analyzed STIM1-Orai interactions using synthetic peptides derived from the N- and C-termini of Orai channels (Orai-NT and Orai-CT, respectively) and purified fragments of STIM1. The binding of STIM1 to Orai-NT is hydrophilic based, whereas binding to the Orai-CT is mostly hydrophobic. STIM1 decreases its affinity for Orai-CT when Orai-NT is present, supporting a stepwise interaction. Orai3-CT exhibits stronger binding to STIM1 than Orai1-CT, largely due to the shortness of one helical turn. The role of newly identified residues was confirmed by co-immunoprecipitation and Ca2+ imaging using full-length molecules. Our results provide important insight into CRAC gating by STIM1.

Keywords: CRAC; Gating mechanism; Immunodeficiency; STIM1; Store-operated Ca2+ entry.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium Channels* / genetics
  • Calcium Channels* / metabolism
  • Calcium Signaling
  • Calcium* / metabolism
  • Endoplasmic Reticulum / genetics
  • Endoplasmic Reticulum / metabolism
  • ORAI1 Protein / genetics
  • ORAI1 Protein / metabolism
  • Stromal Interaction Molecule 1 / genetics
  • Stromal Interaction Molecule 1 / metabolism


  • Calcium Channels
  • ORAI1 Protein
  • Stromal Interaction Molecule 1
  • Calcium