Digitoxin Suppresses Store Operated Calcium Entry by Modulating Phosphorylation and the Pore Region of Orai1

Title:Digitoxin Suppresses Store Operated Calcium Entry by Modulating Phosphorylation and the Pore Region of Orai1

Volume: 18 Issue: 6

Author(s): Lijuan Zhou, Xiangxiang Chi, Yaping Zhu, Tian Zhang, Jindou Liu, Guolin Ma, Lian He, Shuce Zhang, Ping Gao, Yubin Zhou*, Jin Liu*Youjun Wang

Affiliation:

• Institute of Biosciences and Technology, College of Medicine, Texas A&M University, Houston, TX 77030,United States

• Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875,China

Keywords: Calcium signalling, fluorescence imaging, digitoxin, SOCE, Orai1, phosphorylation.

Abstract: Background: Store-operated calcium entry (SOCE), primarily mediated by Orai1 and stromal interaction molecule 1 (STIM1), is a major Ca2+ influx pathway that has been linked to human diseases including myopathy, epilepsy, immunodeficiency, and cancer. Despite of the recent rapid progress of dissecting molecular mechanisms underlying SOCE activation, the development of therapies against dysfunctional SOCE significantly lags behind, partly due to the lack of more specific pharmacological tools and poor understanding of currently available SOCE modifiers, including the a newly identified SOCE inhibitor, digitoxin.

Objective and methods: Capitalizing on Ca2+ imaging and pharmacological tools, we aimed to systemically delineate the mechanism of action of digitoxin by defining how it impinges on Orai1 to exert its suppressive effect on SOCE.

Results: The SOCE-suppressive function of digitoxin is dependent on S27-S30 residues of wild-type Orai1. With 8h-incubation of digitoxin with STIM1-prebound Orai1 or a constitutively active mutant Orai1-ANSGA, its inhibition was no longer dependent on S27-S30 residues. Instead, the inhibition may involve the pore region of Orai1 channels, as V102C mutant at the pore region would greatly diminish or abolish the inhibition on pre-activated Orai1.

Conclusions: Our study identified two regions that are critical for the inhibition on Orai1 channels, providing valuable hotspots for future design of SOCE inhibitors.

Cite this article as:

Zhou Lijuan , Chi Xiangxiang , Zhu Yaping , Zhang Tian , Liu Jindou , Ma Guolin , He Lian , Zhang Shuce , Gao Ping , Zhou Yubin *, Liu Jin *, Wang Youjun , Digitoxin Suppresses Store Operated Calcium Entry by Modulating Phosphorylation and the Pore Region of Orai1, Current Molecular Medicine 2018; 18 (6) . https://dx.doi.org/10.2174/1566524018666181113111316