Volume 21, No 2, Feb 2011

ISSN: 1001-0602 
EISSN: 1748-7838 2018 
impact factor 17.848* 
(Clarivate Analytics, 2019)

Volume 21 Issue 2, February 2011: 305-315

ORIGINAL ARTICLES

Graded activation of CRAC channel by binding of different numbers of STIM1 to Orai1 subunits

Zhengzheng Li^1,*, Lin Liu^2,*, Yongqiang Deng^1,*, Wei Ji¹, Wen Du¹, Pingyong Xu¹, Liangyi Chen¹ and Tao Xu^1,2

¹National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China;

²College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China Correspondence: Tao Xu, Liangyi Chen,(xutao@ibp.ac.cn; chen_liangyi@yahoo.com)

The Ca²⁺ release-activated Ca²⁺ (CRAC) channel pore is formed by Orai1 and gated by STIM1 after intracellular Ca²⁺ store depletion. To resolve how many STIM1 molecules are required to open a CRAC channel, we fused different numbers of Orai1 subunits with functional two-tandem cytoplasmic domains of STIM1 (residues 336-485, designated as S domain). Whole-cell patch clamp recordings of these chimeric molecules revealed that CRAC current reached maximum at a stoichiometry of four Orai1 and eight S domains. Further experiments indicate that two-tandem S domains specifically interact with the C-terminus of one Orai1 subunit, and CRAC current can be gradually increased as more Orai1 subunits can interact with S domains or STIM1 proteins. Our data suggest that maximal opening of one CRAC channel requires eight STIM1 molecules, and support a model that the CRAC channel activation is not in an “all-or-none” fashion but undergoes a graded process via binding of different numbers of STIM1.

The Ca²⁺ release-activated Ca²⁺ (CRAC) channel pore is formed by Orai1 and gated by STIM1 after intracellular Ca²⁺ store depletion. To resolve how many STIM1 molecules are required to open a CRAC channel, we fused differen

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