Cross-talk between N-terminal and C-terminal domains in stromal interaction molecule 2 (STIM2) determines enhanced STIM2 sensitivity

Scott M. Emrich, Ryan E. Yoast, Ping Xin, Xuexin Zhang, Trayambak Pathak, Robert Nwokonko, Maxime F. Gueguinou, Krishna P. Subedi, Yandong Zhou, Indu S. Ambudkar, Nadine Hempel, Khaled Machaca, Donald L. Gill, Mohamed Trebak

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Store-operated Ca2+ entry (SOCE) is a ubiquitous pathway for Ca2+ influx across the plasma membrane (PM). SOCE is mediated by the endoplasmic reticulum (ER)-associated Ca2+-sensing proteins stromal interaction molecule 1 (STIM1) and STIM2, which transition intoan active conformation in response toERCa2+store depletion, thereby interacting with and gating PM-associated ORAI1 channels. Although structurally homologous, STIM1 and STIM2 generate distinct Ca2+ signatures in response to varying strengths of agonist stimulation. The physiological functions of these Ca2+ signatures, particularly under native conditions, remain unclear. To investigate the structural properties distinguishing STIM1 and STIM2 activation of ORAI1 channels under native conditions, here we used CRISPR/Cas9 to generate STIM1-/-, STIM2-/-, and STIM1/2-/- knockouts in HEK293 and colorectalHCT116cells.Weshow that depending on cell type, STIM2 can significantly sustain SOCE in response to maximal store depletion. Utilizing the SOCE modifier 2-aminoethoxydiphenyl borate (2-APB), we demonstrate that 2-APB-activated store-independent Ca2+ entry is mediated exclusively by endogenous STIM2. Using variants that either stabilize or disrupt intramolecular interactions of STIM C termini, we show that the increased flexibility of the STIM2 C terminus contributes to its selective store-independent activation by 2-APB. However,STIM1 variants with enhanced flexibility in the C terminus failed to supportitsstore- independentactivation.STIM1/STIM2chimericconstructs indicated that coordination between N-terminal sensitivity and C-terminal flexibility is required for specific store-independent STIM2 activation. Our results clarify the structural determinants underlying activation of specificSTIMisoforms, insights that are potentially useful for isoform-selective drug targeting.

Original languageEnglish (US)
Pages (from-to)6318-6332
Number of pages15
JournalJournal of Biological Chemistry
Issue number16
StatePublished - Apr 19 2019

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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