A charge-sensing region in the stromal interaction molecule 1 luminal domain confers stabilization-mediated inhibition of SOCE in response to S-nitrosylation

J Biol Chem. 2018 Jun 8;293(23):8900-8911. doi: 10.1074/jbc.RA117.000503. Epub 2018 Apr 16.

Abstract

Store-operated Ca2+ entry (SOCE) is a major Ca2+ signaling pathway facilitating extracellular Ca2+ influx in response to the initial release of intracellular endo/sarcoplasmic reticulum (ER/SR) Ca2+ stores. Stromal interaction molecule 1 (STIM1) is the Ca2+ sensor that activates SOCE following ER/SR Ca2+ depletion. The EF-hand and the adjacent sterile α-motif (EFSAM) domains of STIM1 are essential for detecting changes in luminal Ca2+ concentrations. Low ER Ca2+ levels trigger STIM1 destabilization and oligomerization, culminating in the opening of Orai1-composed Ca2+ channels on the plasma membrane. NO-mediated S-nitrosylation of cysteine thiols regulates myriad protein functions, but its effects on the structural mechanisms that regulate SOCE are unclear. Here, we demonstrate that S-nitrosylation of Cys49 and Cys56 in STIM1 enhances the thermodynamic stability of its luminal domain, resulting in suppressed hydrophobic exposure and diminished Ca2+ depletion-dependent oligomerization. Using solution NMR spectroscopy, we pinpointed a structural mechanism for STIM1 stabilization driven by complementary charge interactions between an electropositive patch on the core EFSAM domain and the S-nitrosylated nonconserved region of STIM1. Finally, using live cells, we found that the enhanced luminal domain stability conferred by either Cys49 and Cys56S-nitrosylation or incorporation of negatively charged residues into the EFSAM electropositive patch in the full-length STIM1 context significantly suppresses SOCE. Collectively, our results suggest that S-nitrosylation of STIM1 inhibits SOCE by interacting with an electropositive patch on the EFSAM core, which modulates the thermodynamic stability of the STIM1 luminal domain.

Keywords: S-nitrosylation; calcium signaling; electrostatics; nitric oxide; nuclear magnetic resonance (NMR); store operated calcium entry; stromal interaction molecule 1 (STIM1); thermodynamics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Calcium / metabolism*
  • Calcium Signaling
  • Cysteine / chemistry
  • Cysteine / metabolism
  • EF Hand Motifs
  • HEK293 Cells
  • Humans
  • Models, Molecular
  • Neoplasm Proteins / chemistry
  • Neoplasm Proteins / metabolism*
  • Nitroso Compounds / chemistry
  • Nitroso Compounds / metabolism
  • Protein Domains
  • Protein Stability
  • Sarcoplasmic Reticulum / metabolism
  • Sequence Alignment
  • Stromal Interaction Molecule 1 / chemistry
  • Stromal Interaction Molecule 1 / metabolism*
  • Thermodynamics

Substances

  • Neoplasm Proteins
  • Nitroso Compounds
  • STIM1 protein, human
  • Stromal Interaction Molecule 1
  • Cysteine
  • Calcium