The ryanodine receptor agonist 4-chloro-3-ethylphenol blocks ORAI store-operated channels: 4-Chloro-3-ethylphenol inhibits ORAI channels

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

Abstract

Background
Depletion of the Ca2+ store by ryanodine receptor (RyR) agonists induces store‐operated Ca2+ 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.

Experimental Approach
SOCE and ORAI1‐3 currents were recorded by Ca2+ imaging and whole‐cell patch recordings in rat L6 myoblasts and in HEK293 cells overexpressing STIM1/ORAI1‐3.

Key Results
4‐CEP induced a significant release of Ca2+ 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 Ca2+ 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 Ca2+ store‐depleting effect via the activation of RyR, but no effect on STIM1 redistribution was observed in cells co‐expressing STIM1/ORAI1‐3.

Conclusion and Implications
4‐CEP not only acts as a RyR agonist to deplete the Ca2+ 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.

Citation

Zeng, B., Chen, G.-L., Daskoulidou, N., & Xu, S.-Z. (2014). The ryanodine receptor agonist 4-chloro-3-ethylphenol blocks ORAI store-operated channels: 4-Chloro-3-ethylphenol inhibits ORAI channels. British Journal of Pharmacology, 171(5), 1250-1259. https://doi.org/10.1111/bph.12528

• Journal Article Type: Article
• Acceptance Date: Nov 6, 2013
• Online Publication Date: Feb 27, 2014
• Publication Date: 2014-03
• Deposit Date: Apr 25, 2019
• Journal: British Journal of Pharmacology
• Print ISSN: 0007-1188
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 171
• Issue: 5
• Pages: 1250-1259
• DOI: https://doi.org/10.1111/bph.12528
• Keywords: Ryanodine receptors; Store-operated Ca2+ channels; STIM1; ORAI; 4-chloro-3-ethylphenol; 4-chloro-m-cresol
• Public URL: https://hull-repository.worktribe.com/output/1647133
• Publisher URL: https://bpspubs.onlinelibrary.wiley.com/doi/full/10.1111/bph.12528