title: 2-Aminoethoxydiphenyl Borate Potentiates CRAC Current by Directly Dilating the Pore of Open Orai1.
abstract: 2-Aminoethoxydiphenyl borate (2-APB) elicits potentiation current (Ip) on Ca(2+) release-activated Ca(2+) (CRAC) channels. An accurate investigation into this modulation mechanism would reveal how STIM1-dependent channel gating is enhanced, and benefit the future immune enhancer development. Here, we directly probed the pore diameter of CRAC channels and found that 2-APB enlarged the pore size of STIM1-activated Orai1 from 3.8 to 4.6 Å. We demonstrated that ions with small sizes, i.e., Ca(2+) and Na(+), mediated prominent 2-APB-induced Ip on the wildtype (WT) Orai1 channels of narrow pore sizes, while conducted decreased or no Ip on Orai1-V102C/A/G mutant channels with enlarged pore diameters. On the contrary, large Cs(+) ions blocked the WT channels, while displayed large 2-APB induced Ip on pore-enlarged Orai1-V102C/A/G mutant channels, and the potentiation ratio was highest on Orai1-V102C with an intermediate pore size. Furthermore, we showed that 2-APB potentiated Cs(+) current on constitutively active Orai1-V102C/A/G mutants independent of STIM1. Our data suggest that 2-APB directly dilates the pore of open Orai1 channels, both ion size and pore diameter jointly determine the amplitude of Ip on CRAC channels, and the generation of Ip requires the open state of Orai1, not STIM1 itself.
authors.affiliation: National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Xu
authors.affiliation: National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.|University of Chinese Academy of Science, Beijing 100049, China.
authors.forename: Sher
authors.initials: S
authors.lastname: Ali
authors.affiliation: National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.|College of Life Science, Sichuan Normal University, Chengdu 610101, China.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, WA, USA.
authors.forename: Haijie
authors.initials: H
authors.lastname: Yu
authors.affiliation: Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Mingshu
authors.initials: M
authors.lastname: Zhang
authors.affiliation: National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Jingze
authors.initials: J
authors.lastname: Lu
authors.affiliation: National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Xu
mesh_terms: D001896:Boron Compounds / Q000737:chemistry / Q000378:metabolism*; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D000071739:Calcium Release Activated Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling; D057809:HEK293 Cells; D006801:Humans; D007114:Immunization; D015640:Ion Channel Gating; D017136:Ion Transport; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D009363:Neoplasm Proteins / Q000378:metabolism*; D000071740:ORAI1 Protein / Q000235:genetics / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D012964:Sodium / Q000737:chemistry / Q000378:metabolism; D000071737:Stromal Interaction Molecule 1 / Q000378:metabolism*
chemical_list: D001896:Boron Compounds; D000071739:Calcium Release Activated Calcium Channels; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D012964:Sodium; C109986:2-aminoethoxydiphenyl borate; D002118:Calcium