title: Calsequestrin-1 Regulates Store-Operated Ca2+ Entry by Inhibiting STIM1 Aggregation.
abstract: OBJECTIVE
  Stromal interacting molecule-1 (STIM1) aggregation and redistribution to plasma membrane to interact with Orai1 constitute the core mechanism of store-operated Ca2+ entry (SOCE). Previous study has revealed that calsequestrin-1 (CSQ1) regulates SOCE in HEK293 cells through interacting with STIM1 and inhibiting STIM1/Orai1 interaction. Here, we further investigate how CSQ1/STIM1 interaction affects SOCE.
  
  
  METHODS
  Using confocal microscopy, STIM1 aggregation and co-localizations with CSQ1 or Orai1 upon Ca2+ store depletion by thapsigargin were measured and quantified by Imaris software in HeLa cells transfected with different CSQ1 mutants. The interactions of CSQ1/STIM1 and STIM1/Orai1, and internal Ca2+ changes were detected by co-immunoprecipitation and Fura2, respectively.
  
  
  RESULTS
  Wt-CSQ1 overexpression significantly reduced STIM1 clustering in the perimembrane and cytosolic regions, whereas over-expression of a C-terminal amino acid 362-396 deletion mutant (C35) did not. Consistently, a significant depression of SOCE, increased CSQ1 monomerization and CSQ1/STIM1 interaction, and a reduced STIM1/Orai1 association were observed in wt-CSQ1 but not in C35-transfected cells. Additionally, mutant lacking C-terminal AA 388-396 deletion exerted weaker potency in inhibiting STIM1 aggregation and association with Orai1 than wt-CSQ1.
  
  
  CONCLUSIONS
  Our results demonstrate that CSQ1 monomers suppress SOCE by interacting with STIM1 and attenuating STIM1 aggregation via its C-terminal amino acid 362-396.
authors.forename: Lane
authors.initials: L
authors.lastname: Zhang
authors.forename: Limin
authors.initials: L
authors.lastname: Wang
authors.forename: Shu
authors.initials: S
authors.lastname: Li
authors.forename: Jingyi
authors.initials: J
authors.lastname: Xue
authors.forename: Dali
authors.initials: D
authors.lastname: Luo
mesh_terms: D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D002155:Calsequestrin; D002413:Cations, Divalent / Q000032:analysis / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D024101:Mitochondrial Proteins / Q000032:analysis / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000032:analysis / Q000378:metabolism*; D000071740:ORAI1 Protein / Q000032:analysis / Q000378:metabolism; D066329:Protein Aggregates; D060066:Protein Interaction Maps; D000071737:Stromal Interaction Molecule 1 / Q000032:analysis / Q000378:metabolism*
chemical_list: C503129:CASQ1 protein, human; D002135:Calcium-Binding Proteins; D002155:Calsequestrin; D002413:Cations, Divalent; D024101:Mitochondrial Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D066329:Protein Aggregates; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D002118:Calcium