Store-dependent and -independent Modes Regulating Ca2+ Release-activated Ca2+ Channel Activity of Human Orai1 and Orai3

Zhang, Shenyuan L.; Kozak, J. Ashot; Jiang, Weihua; Yeromin, Andriy V.; Chen, Jing; Yu, Ying; Penna, Aubin; Shen, Wei; Chi, Victor; Cahalan, Michael D.

doi:10.1074/jbc.m801536200

Cited by 172 publications

(210 citation statements)

References 45 publications

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“…3D) revealed the currents were exclusively CRAC-like. Previous studies also reported constitutive coupling between Cterminal STIM1 and Orai1 (24,29,30) with a similar basal current of Ϸ3-4 pA/pF (24,30). S2ct-YFP expressed in HEK-Orai1 cells also caused constitutive Ca 2ϩ entry and 2-APB-induced Ca 2ϩ entry.…”

Section: Resultsmentioning

confidence: 94%

“…The action of 2-APB on SOCs is complex; recent studies suggest 2-APB may directly activate Orai3 channels (22)(23)(24)(25), an effect thought to be independent of STIM1. We determined that the avian genome is missing the of STIM2 was not addressed.…”

Section: Resultsmentioning

confidence: 99%

“…Its actions are complex, enhancing SOC activation at 5-10 M, yet blocking it at 50 M (20, 21). Recent evidence emphasizes the remarkable effectiveness and the complexities of 2-APB in modifying STIM protein function and Orai channel gating (22)(23)(24)(25). Although its actions are enigmatic, they indicate 2-APB is a valuable tool in deciphering the STIM-Orai coupling mechanism.…”

Section: Stim Proteins Are Sensors Of Endoplasmic Reticulum (Er) Luminalmentioning

confidence: 99%

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STIM protein coupling in the activation of Orai channels

Wang

Deng

Zhou

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

123

141

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STIM proteins are sensors of endoplasmic reticulum (ER) luminalCa 2؉ changes and rapidly translocate into near plasma membrane (PM) junctions to activate Ca 2؉ entry through the Orai family of highly Ca 2؉ -selective ''store-operated'' channels (SOCs). Dissecting the STIM-Orai coupling process is restricted by the abstruse nature of the ER-PM junctional domain. To overcome this problem, we studied coupling by using STIM chimera and cytoplasmic C-terminal domains of STIM1 and STIM2 (S1ct and S2ct) and identifying a fundamental action of the powerful SOC modifier, 2-aminoethoxydiphenyl borate (2-APB), the mechanism of which has eluded recent scrutiny. We reveal that 2-APB induces profound, rapid, and direct interactions between S1ct or S2ct and Orai1, effecting full Ca 2؉ release-activated Ca 2؉ (CRAC) current activation. The short 235-505 S1ct coiled-coil region was sufficient for functional Orai1 coupling. YFP-tagged S1ct or S2ct fragments cleared from the cytosol seconds after 2-APB addition, binding avidly to Orai1-CFP with a rapid increase in FRET and transiently increasing CRAC current 200-fold above basal levels. Functional S1ct-Orai1 coupling occurred in STIM1/STIM2 ؊/؊ DT40 chicken B cells, indicating ct fragments operate independently of native STIM proteins. The 2-APB-induced S1ct-Orai1 and S2-ct-Orai1 complexes undergo rapid reorganization into discrete colocalized PM clusters, which remain stable for >100 s, well beyond CRAC activation and subsequent deactivation. In addition to defining 2-APB's action, the locked STIMct-Orai complex provides a potentially useful probe to structurally examine coupling.calcium signaling ͉ DT40 cells ͉ CRAC channel A dynamic interplay between 2 membrane proteins, STIM and Orai, underlies an intricate coupling between Ca 2ϩ release from endoplasmic reticulum (ER) stores and Ca 2ϩ entry across the plasma membrane (PM) (1-3). The single spanning transmembrane proteins STIM1 and STIM2 function as sensors of ER luminal Ca 2ϩ changes (4-7). Depletion of luminal Ca 2ϩ within ER stores triggers STIM proteins to aggregate and undergo rapid translocation into closely juxtaposed ER-PM junctions to activate Ca 2ϩ entry through one or more of the 3-member family of PM tetra-spanning channel proteins, Orai1, Orai2, and Orai3 (8-10). The Orai proteins function as highly Ca 2ϩ -selective ''storeoperated'' channels (SOCs) (11,12). The activation of SOCs is crucial in mediating longer-term cytosolic Ca 2ϩ signals, replenishing intracellular stores, and homeostatic control of both cytosolic and ER luminal Ca 2ϩ levels (3,(11)(12)(13)(14). Orai1 coexpressed with STIM1 reconstitutes high levels of the inwardly-rectifying Ca 2ϩ release-activated Ca 2ϩ (CRAC) current (10, 15-17), the hallmark of SOCs (11,12).Despite close interactions (5, 18), the coupling mechanism between STIM and Orai proteins to activate Ca 2ϩ entry remains to be elucidated. Our approach was to examine the STIM-Orai interactions by using the reactive borate 2-aminoethoxydiphenyl borate (2-APB), a powerful modifier of SOC ...

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Stim Proteins Are Sensors Of Endoplasmic Reticulum (Er) Luminalmentioning

confidence: 99%

See 1 more Smart Citation

STIM protein coupling in the activation of Orai channels

Wang

Deng

Zhou

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

123

141

View full text Add to dashboard Cite

show abstract

“…The capability of heteromeric Orai assembly has been demonstrated biochemically (9,21,22). We initially evaluated the potential of Orai1 and Orai3 heteromerization by employing fluorescence resonance energy transfer (FRET) microscopy.…”

Section: Resultsmentioning

confidence: 99%

Plasticity in Ca ²⁺ selectivity of Orai1/Orai3 heteromeric channel

Schindl

Frischauf

Bergsmann

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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A general cellular response following depletion of intracellular calcium stores involves activation of store-operated channels (SOCs). While Orai1 forms the native Ca 2+ release-activated Ca 2+ (CRAC) channel in mast and T cells, the molecular architecture of less Ca 2+ selective SOCs is insufficiently defined. Here we present evidence that diminished Ca 2+ selectivity and robust Cs + permeation together with a reduced fast inactivation are characteristics of heteromeric Orai1 and Orai3 channels in contrast to their homomeric forms. The first extracellular loop of these Orai isoforms differs by two aspartates replacing glutamates that affect the selectivity. Co-expression of an Orai3 mutant that mimicked the first loop of Orai1 with either Orai1 or Orai3 recovered or decreased Ca 2+ selectivity, respectively. Heteromeric Orai1/3 protein assembly provides a concept for less Ca 2+ -selective SOCs.

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“…These differences underscore the importance of maximizing the STIM/Orai ratio (Scrimgeour et al, 2009;Hoover and Lewis, 2011) when studying the effects of mutations on CDI in heterologous expression systems. Effects of low STIM/Orai ratio may explain why several studies have reported that heterologous Orai1 channels activated by STIM1 do not inactivate at all, but instead potentiate during hyperpolarizing pulses (Zhang et al, 2008;Lee et al, 2009;Yuan et al, 2009).…”

Section: Effects Of Intracellular Chloride On CDImentioning

confidence: 99%