Referenced in: none

Automatically associated channels: Slo1

Title: Distinct Orai-coupling domains in STIM1 and STIM2 define the Orai-activating site.

Authors: Xizhuo Wang, Youjun Wang, Yandong Zhou, Eunan Hendron, Salvatore Mancarella, Mark D Andrake, Brad S Rothberg, Jonathan Soboloff, Donald L Gill

Journal, date & volume: Nat Commun, 2014 , 5, 3183

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/24492416

Abstract
STIM1 and STIM2 are widely expressed endoplasmic reticulum (ER) Ca(2+) sensor proteins able to translocate within the ER membrane to physically couple with and gate plasma membrane Orai Ca(2+) channels. Although they are structurally similar, we reveal critical differences in the function of the short STIM-Orai-activating regions (SOAR) of STIM1 and STIM2. We narrow these differences in Orai1 gating to a strategically exposed phenylalanine residue (Phe-394) in SOAR1, which in SOAR2 is substituted by a leucine residue. Remarkably, in full-length STIM1, replacement of Phe-394 with the dimensionally similar but polar histidine head group prevents both Orai1 binding and gating, creating an Orai1 non-agonist. Thus, this residue is critical in tuning the efficacy of Orai activation. While STIM1 is a full Orai1-agonist, leucine-replacement of this crucial residue in STIM2 endows it with partial agonist properties, which may be critical for limiting Orai1 activation stemming from its enhanced sensitivity to store-depletion.