Abstract

Ca(2+)-release-activated Ca(2+) (CRAC) channels generate sustained Ca(2+) signals that are essential for a range of cell functions, including antigen-stimulated T lymphocyte activation and proliferation. Recent studies have revealed that the depletion of Ca(2+) from the endoplasmic reticulum (ER) triggers the oligomerization of stromal interaction molecule 1 (STIM1), the ER Ca(2+) sensor, and its redistribution to ER-plasma membrane (ER-PM) junctions where the CRAC channel subunit ORAI1 accumulates in the plasma membrane and CRAC channels open. However, how the loss of ER Ca(2+) sets into motion these coordinated molecular rearrangements remains unclear. Here we define the relationships among [Ca(2+)](ER), STIM1 redistribution and CRAC channel activation and identify STIM1 oligomerization as the critical [Ca(2+)](ER)-dependent event that drives store-operated Ca(2+) entry. In human Jurkat leukaemic T cells expressing an ER-targeted Ca(2+) indicator, CRAC channel activation and STIM1 redistribution follow the same function of [Ca(2+)](ER), reaching half-maximum at approximately 200 microM with a Hill coefficient of approximately 4. Because STIM1 binds only a single Ca(2+) ion, the high apparent cooperativity suggests that STIM1 must first oligomerize to enable its accumulation at ER-PM junctions. To assess directly the causal role of STIM1 oligomerization in store-operated Ca(2+) entry, we replaced the luminal Ca(2+)-sensing domain of STIM1 with the 12-kDa FK506- and rapamycin-binding protein (FKBP12, also known as FKBP1A) or the FKBP-rapamycin binding (FRB) domain of the mammalian target of rapamycin (mTOR, also known as FRAP1). A rapamycin analogue oligomerizes the fusion proteins and causes them to accumulate at ER-PM junctions and activate CRAC channels without depleting Ca(2+) from the ER. Thus, STIM1 oligomerization is the critical transduction event through which Ca(2+) store depletion controls store-operated Ca(2+) entry, acting as a switch that triggers the self-organization and activation of STIM1-ORAI1 clusters at ER-PM junctions.

View details for DOI 10.1038/nature07065

View details for Web of Science ID 000257860300056

View details for PubMedID 18596693

School of Medicine

Showing 1-3 of 3 Results

Stephan Maxeiner

Basic Life Sci Res Assoc, Molecular and Cellular Physiology

Theodoros Tsetsenis

Basic Life Sci Res Assoc, Molecular and Cellular Physiology

Minnie Wu

Basic Life Sci Research Associate, Molecular and Cellular Physiology

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