Local cytosolic Ca2+ elevations are required for stromal interaction molecule 1 (STIM1) de-oligomerization and termination of store-operated Ca2+ entry

J Biol Chem. 2011 Oct 21;286(42):36448-59. doi: 10.1074/jbc.M111.269415. Epub 2011 Aug 31.


The Ca(2+) depletion of the endoplasmic reticulum (ER) activates the ubiquitous store-operated Ca(2+) entry (SOCE) pathway that sustains long-term Ca(2+) signals critical for cellular functions. ER Ca(2+) depletion initiates the oligomerization of stromal interaction molecules (STIM) that control SOCE activation, but whether ER Ca(2+) refilling controls STIM de-oligomerization and SOCE termination is not known. Here, we correlate the changes in free luminal ER Ca(2+) concentrations ([Ca(2+)](ER)) and in STIM1 oligomerization, using fluorescence resonance energy transfer (FRET) between CFP-STIM1 and YFP-STIM1. We observed that STIM1 de-oligomerized at much lower [Ca(2+)](ER) levels during store refilling than it oligomerized during store depletion. We then refilled ER stores without adding exogenous Ca(2+) using a membrane-permeable Ca(2+) chelator to provide a large reservoir of buffered Ca(2+). This procedure rapidly restored pre-stimulatory [Ca(2+)](ER) levels but did not trigger STIM1 de-oligomerization, the FRET signals remaining elevated as long as the external [Ca(2+)] remained low. STIM1 dissociation evoked by Ca(2+) readmission was prevented by SOC channel inhibition and was associated with cytosolic Ca(2+) elevations restricted to STIM1 puncta, indicating that Ca(2+) acts on a cytosolic target close to STIM1 clusters. These data indicate that the refilling of ER Ca(2+) stores is not sufficient to induce STIM1 de-oligomerization and that localized Ca(2+) elevations in the vicinity of assembled SOCE complexes are required for the termination of SOCE.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism*
  • Chelating Agents / pharmacology
  • Endoplasmic Reticulum / genetics
  • Endoplasmic Reticulum / metabolism*
  • Fluorescence Resonance Energy Transfer / methods
  • HeLa Cells
  • Humans
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Protein Multimerization / drug effects
  • Protein Multimerization / physiology*
  • Stromal Interaction Molecule 1


  • Chelating Agents
  • Membrane Proteins
  • Neoplasm Proteins
  • STIM1 protein, human
  • Stromal Interaction Molecule 1
  • Calcium