The ryanodine receptor agonist 4-chloro-3-ethylphenol blocks ORAI store-operated channels.

Bo Zeng, Gui-Lan Chen, Nikoleta Daskoulidou, Shang-Zhong Xu

文献索引：Br. J. Pharmacol. 171(5) , 1250-9, (2014)

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摘要

Depletion of the Ca(2+) store by ryanodine receptor (RyR) agonists induces store-operated Ca(2+) entry (SOCE). 4-Chloro-3-ethylphenol (4-CEP) and 4-chloro-m-cresol (4-CmC) are RyR agonists commonly used as research tools and diagnostic reagents for malignant hyperthermia. Here, we investigated the effects of 4-CEP and its analogues on SOCE.SOCE and ORAI1-3 currents were recorded by Ca(2+) imaging and whole-cell patch recordings in rat L6 myoblasts and in HEK293 cells overexpressing STIM1/ORAI1-3.4-CEP induced a significant release of Ca(2+) in rat L6 myoblasts, but inhibited SOCE. The inhibitory effect was concentration-dependent and more potent than its analogues 4-CmC and 4-chlorophenol (4-ClP). In the HEK293 T-REx cells overexpressing STIM1/ORAI1-3, 4-CEP inhibited the ORAI1, ORAI2 and ORAI3 currents evoked by thapsigargin. The 2-APB-induced ORAI3 current was also blocked by 4-CEP. This inhibitory effect was reversible and independent of the Ca(2+) release. The two analogues, 4-CmC and 4-ClP, also inhibited the ORAI1-3 channels. Excised patch and intracellular application of 4-CEP demonstrated that the action site was located extracellularly. Moreover, 4-CEP evoked STIM1 translocation and subplasmalemmal clustering through its Ca(2+) store-depleting effect via the activation of RyR, but no effect on STIM1 redistribution was observed in cells co-expressing STIM1/ORAI1-3.4-CEP not only acts as a RyR agonist to deplete the Ca(2+) store and trigger STIM1 subplasmalemmal translocation and clustering, but also directly inhibits ORAI1-3 channels. These findings demonstrate a novel pharmacological property for the chlorophenol derivatives that act as RyR agonists.© 2013 The British Pharmacological Society.