Live-cell imaging reveals sequential oligomerization and local plasma membrane targeting of stromal interaction molecule 1 after Ca2+ store depletion

Jen Liou, Marc Fivaz, Takanari Inoue, Tobias Meyer

Research output: Contribution to journalArticle

446 Scopus citations

Abstract

Stromal interaction molecule 1 (STIM1) has recently been identified by our group and others as an endoplasmic reticulum (ER) Ca2+ sensor that responds to ER Ca2+ store depletion and activates Ca2+ channels in the plasma membrane (PM). The molecular mechanism by which STIM1 transduces signals from the ER lumen to the PM is not yet understood. Here we developed a live-cell FRET approach and show that STIM1 forms oligomers within 5 s after Ca2+ store depletion. These oligomers rapidly dissociated when ER Ca2+ stores were refilled. We further show that STIM1 formed oligomers before its translocation within the ER network to ER-PM junctions. A mutant STIM1 lacking the C-terminal polybasic PM-targeting motif oligomerized after Ca2+ store depletion but failed to form puncta at ER-PM junctions. Using fluorescence recovery after photobleaching measurements to monitor STIM1 mobility, we show that STIM1 oligomers translocate on average only 2 μm to reach ER-PM junctions, arguing that STIM1 ER-to-PM signaling is a local process that is suitable for generating cytosolic Ca2+ gradients. Together, our live-cell measurements dissect the STIM1 ER-to-PM signaling relay into four sequential steps: (i) dissociation of Ca2+, (ii) rapid oligomerization, (iii) spatially restricted translocation to nearby ER-PM junctions, and (iv) activation of PM Ca2+ channels.

Original languageEnglish (US)
Pages (from-to)9301-9306
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume104
Issue number22
DOIs
Publication statusPublished - May 29 2007

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Keywords

  • Ca release-activated Ca
  • Fluorescence recovery after photobleaching
  • FRET
  • Store-operated Ca influx

ASJC Scopus subject areas

  • Genetics
  • General

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