title: Molecular Determinants for STIM1 Activation During Store- Operated Ca2+ Entry.
abstract: BACKGROUND
  STIM/ORAI-mediated store-operated Ca2+ entry (SOCE) mediates a myriad of Ca2+-dependent cellular activities in mammals. Genetic defects in STIM1/ORAI1 lead to devastating severe combined immunodeficiency; whereas gain-offunction mutations in STIM1/ORAI1 are intimately associated with tubular aggregate myopathy. At molecular level, a decrease in the Ca2+ concentrations within the lumen of endoplasmic reticulum (ER) initiates multimerization of the STIM1 luminal domain to switch on the STIM1 cytoplasmic domain to engage and gate ORAI channels, thereby leading to the ultimate Ca2+ influx from the extracellular space into the cytosol. Despite tremendous progress made in dissecting functional STIM1-ORAI1 coupling, the activation mechanism of SOCE remains to be fully characterized.
  
  
  OBJECTIVE
  Building upon a robust fluorescence resonance energy transfer assay designed to monitor STIM1 intramolecular autoinhibition, we aimed to systematically dissect the molecular determinants required for the activation and oligomerization of STIM1.
  
  
  RESULTS
  Here we showed that truncation of the STIM1 luminal domain predisposes STIM1 to adopt a more active conformation. Replacement of the single transmembrane (TM) domain of STIM1 by a more rigid dimerized TM domain of glycophorin A abolished STIM1 activation. But this adverse effect could be partially reversed by disrupting the TM dimerization interface. Moreover, our study revealed regions that are important for the optimal assembly of hetero-oligomers composed of full-length STIM1 with its minimal STIM1-ORAI activating region, SOAR.
  
  
  CONCLUSIONS
  Our study clarifies the roles of major STIM1 functional domains in maintaining a quiescent configuration of STIM1 to prevent preactivation of SOCE.
authors.affiliation: Center for Translational Cancer Research, Institute of Biosciences and Technology, Texas A&M University, Houston, TX 77030. United States.
authors.forename: G
authors.initials: G
authors.lastname: Ma
authors.affiliation: Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875. China.
authors.forename: S
authors.initials: S
authors.lastname: Zheng
authors.affiliation: Center for Translational Cancer Research, Institute of Biosciences and Technology, Texas A&M University, Houston, TX 77030. United States.
authors.forename: Y
authors.initials: Y
authors.lastname: Ke
authors.affiliation: Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875. China.
authors.forename: L
authors.initials: L
authors.lastname: Zhou
authors.affiliation: Center for Translational Cancer Research, Institute of Biosciences and Technology, Texas A&M University, Houston, TX 77030. United States.
authors.forename: L
authors.initials: L
authors.lastname: He
authors.affiliation: Center for Epigenetic and Disease Prevention, Institute of Biosciences and Technology, Texas A&M University, Houston, TX 77030. United States.
authors.forename: Y
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Center for Translational Cancer Research, Institute of Biosciences and Technology, Texas A&M University System Health Science Center, 2121 W. Holcombe Blvd., Houston, TX 77030. United States.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Center for Translational Cancer Research, Institute of Biosciences and Technology, Texas A&M University System Health Science Center, 2121 W. Holcombe Blvd., Houston, TX 77030. United States.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhou
mesh_terms: D000595:Amino Acid Sequence; D001221:Aspartate Carbamoyltransferase / Q000737:chemistry / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D004080:Dihydroorotase / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating; D018613:Microscopy, Confocal; D008958:Models, Molecular; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D015398:Signal Transduction; D000071737:Stromal Interaction Molecule 1 / Q000819:agonists / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: C033626:CAD trifunctional enzyme; D015220:Calcium Channels; D000071737:Stromal Interaction Molecule 1; D001221:Aspartate Carbamoyltransferase; D004080:Dihydroorotase; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing); D002118:Calcium
keywords: Calcium signaling; FRET; ORAI1; STIM1; calcium
  release-activated calcium channel; imaging; protein-protein interaction; store-operated calcium entry