STIM1 dimers undergo unimolecular coupling to activate Orai1 channels

Yandong Zhou (), Xizhuo Wang, Xianming Wang, Natalia A. Loktionova, Xiangyu Cai, Robert M. Nwokonko, Erin Vrana, Youjun Wang, Brad S. Rothberg and Donald L. Gill ()
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Yandong Zhou: The Pennsylvania State University College of Medicine
Xizhuo Wang: The Pennsylvania State University College of Medicine
Xianming Wang: The Pennsylvania State University College of Medicine
Natalia A. Loktionova: The Pennsylvania State University College of Medicine
Xiangyu Cai: The Pennsylvania State University College of Medicine
Robert M. Nwokonko: The Pennsylvania State University College of Medicine
Erin Vrana: The Pennsylvania State University College of Medicine
Youjun Wang: College of Life Sciences, Beijing Normal University
Brad S. Rothberg: Temple University School of Medicine
Donald L. Gill: The Pennsylvania State University College of Medicine

Nature Communications, 2015, vol. 6, issue 1, 1-10

Abstract: Abstract The endoplasmic reticulum (ER) Ca2+ sensor, STIM1, becomes activated when ER-stored Ca2+ is depleted and translocates into ER–plasma membrane junctions where it tethers and activates Orai1 Ca2+ entry channels. The dimeric STIM1 protein contains a small STIM-Orai-activating region (SOAR)—the minimal sequence sufficient to activate Orai1 channels. Since SOAR itself is a dimer, we constructed SOAR concatemer–dimers and introduced mutations at F394, which is critical for Orai1 coupling and activation. The F394H mutation in both SOAR monomers completely blocks dimer function, but F394H introduced in only one of the dimeric SOAR monomers has no effect on Orai1 binding or activation. This reveals an unexpected unimolecular coupling between STIM1 and Orai1 and argues against recent evidence suggesting dimeric interaction between STIM1 and two adjacent Orai1 channel subunits. The model predicts that STIM1 dimers may be involved in crosslinking between Orai1 channels with implications for the kinetics and localization of Orai1 channel opening.

Date: 2015
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DOI: 10.1038/ncomms9395

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