Abstract
Store-operated Ca2+ entry fulfills a crucial role in controlling Ca2+ signals in almost all cells. The Ca2+-sensing stromal interaction molecule (STIM) proteins in the endoplasmic reticulum (ER) undergo complex conformational changes in response to depleted ER luminal Ca2+, allowing them to unfold and become trapped in ER-plasma membrane (PM) junctions. Dimers of STIM proteins trap and gate the plasma membrane Orai Ca2+ channels within these junctions to generate discrete zones of high Ca2+ and regulate sensitive Ca2+-dependent intracellular signaling pathways. The STIM-Orai activating region (SOAR) of STIM1 becomes exposed upon store depletion and promotes trapping of Orai1 at the PM. Residue Phe-394 within SOAR forms an integral part of the high-affinity Orai1-interacting site. Our results demonstrate that only a single active site within the dimeric SOAR domain of STIM1 is required for the activation of Orai1 channel activity. This unimolecular model is strongly supported by evidence of variable STIM1:Orai1 stoichiometry reported in many studies. We hypothesize that unimolecular coupling promotes cross-linking of channels, localizing Ca2+ signals, and regulating channel activity. We have also identified a key “nexus” region in Orai1 near the C-terminal STIM1-binding site that can be mutated to constitutively activate Ca2+ entry, mimicking STIM1 activated channels. This suggests that STIM1 mediates gating of Orai1 in an allosteric manner via interaction with the Orai1 C-terminus alone. This model suggests the dual role of STIM1 in regulating both localization and gating of Orai1 channels and has important implications for the regulation of SOCE-mediated downstream signaling and the kinetics of channel activation.
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References
Amcheslavsky A, Wood ML, Yeromin AV, Parker I, Freites JA, Tobias DJ, Cahalan MD (2015) Molecular biophysics of Orai store-operated Ca2+ channels. Biophys J 108:237–246
Cai X, Zhou Y, Nwokonko RM, Loktionova NA, Wang X, Xin P, Trebak M, Wang Y, Gill DL (2016) The Orai1 store-operated calcium channel functions as a hexamer. J Biol Chem 291:25764–25775
Covington ED, MM W, Lewis RS (2010) Essential role for the CRAC activation domain in store-dependent oligomerization of STIM1. Mol Biol Cell 21:1897–1907
Derler I, Plenk P, Fahrner M, Muik M, Jardin I, Schindl R, Gruber HJ, Groschner K, Romanin C (2013) The extended transmembrane Orai1 N-terminal (ETON) region combines binding interface and gate for Orai1 activation by STIM1. J Biol Chem 288:29025–29034
Derler I, Jardin I, Romanin C (2016) Molecular mechanisms of STIM/Orai communication. Am J Physiol Cell Physiol 310:C643–C662
Fahrner M, Muik M, Schindl R, Butorac C, Stathopulos P, Zheng L, Jardin I, Ikura M, Romanin C (2014) A coiled-coil clamp controls both conformation and clustering of stromal interaction molecule 1 (STIM1). J Biol Chem 289:33231–33244
Gudlur A, Quintana A, Zhou Y, Hirve N, Mahapatra S, Hogan PG (2014) STIM1 triggers a gating rearrangement at the extracellular mouth of the ORAI1 channel. Nat Commun 5:5164
Hoover PJ, Lewis RS (2011) Stoichiometric requirements for trapping and gating of Ca2+ release-activated Ca2+ (CRAC) channels by stromal interaction molecule 1 (STIM1). Proc Natl Acad Sci U S A 108:13299–13304
Hou X, Pedi L, Diver MM, Long SB (2012) Crystal structure of the calcium release-activated calcium channel Orai. Science 338:1308–1313
Kar P, Parekh AB (2015) Distinct spatial Ca2+ signatures selectively activate different NFAT transcription factor isoforms. Mol Cell 58:232–243
Korzeniowski MK, Popovic MA, Szentpetery Z, Varnai P, Stojilkovic SS, Balla T (2009) Dependence of STIM1/Orai1-mediated calcium entry on plasma membrane phosphoinositides. J Biol Chem 284:21027–21035
Li Z, Lu J, Xu P, Xie X, Chen L, Xu T (2007) Mapping the interacting domains of STIM1 and Orai1 in CRAC channel activation. J Biol Chem 282:29448–20456
Li Z, Liu L, Deng Y, Ji W, Du W, Xu P, Chen L, Xu T (2011) Graded activation of CRAC channel by binding of different numbers of STIM1 to Orai1 subunits. Cell Res 21:305–315
Lis A, Zierler S, Peinelt C, Fleig A, Penner R (2010) A single lysine in the N-terminal region of store-operated channels is critical for STIM1-mediated gating. J Gen Physiol 136:673–686
Ma G, Wei M, He L, Liu C, Wu B, Zhang SL, Jing J, Liang X, Senes A, Tan P, Li S, Sun A, Bi Y, Zhong L, Si H, Shen Y, Li M, Lee MS, Zhou W, Wang J, Wang Y, Zhou Y (2015) Inside-out Ca(2+) signalling prompted by STIM1 conformational switch. Nat Commun 6:7826
Maus M, Jairaman A, Stathopulos PB, Muik M, Fahrner M, Weidinger C, Benson M, Fuchs S, Ehl S, Romanin C, Ikura M, Prakriya M, Feske S (2015) Missense mutation in immunodeficient patients shows the multifunctional roles of coiled-coil domain 3 (CC3) in STIM1 activation. Proc Natl Acad Sci U S A 112:6206–6211
McNally BA, Somasundaram A, Jairaman A, Yamashita M, Prakriya M (2013) The C- and N-terminal STIM1 binding sites on Orai1 are required for both trapping and gating CRAC channels. J Physiol 591:2833–2850
Muik M, Fahrner M, Derler I, Schindl R, Bergsmann J, Frischauf I, Groschner K, Romanin C (2009) A cytosolic homomerization and a modulatory domain within STIM1 C-terminus determine coupling to ORAI1 channels. J Biol Chem 284:8421–8426
Mullins FM, Lewis RS (2016) The inactivation domain of STIM1 is functionally coupled with the Orai1 pore to enable Ca2+-dependent inactivation. J Gen Physiol 147:153–164
Mullins FM, Yen M, Lewis RS (2016) Orai1 pore residues control CRAC channel inactivation independently of calmodulin. J Gen Physiol 147:137–152
Palty R, Stanley C, Isacoff EY (2015) Critical role for Orai1 C-terminal domain and TM4 in CRAC channel gating. Cell Res 25:963–980
Park CY, Hoover PJ, Mullins FM, Bachhawat P, Covington ED, Raunser S, Walz T, Garcia KC, Dolmetsch RE, Lewis RS (2009) STIM1 clusters and activates CRAC channels via direct binding of a cytosolic domain to Orai1. Cell 136:876–890
Perni S, Dynes JL, Yeromin AV, Cahalan MD, Franzini-Armstrong C (2015) Nanoscale patterning of STIM1 and Orai1 during store-operated Ca2+ entry. Proc Natl Acad Sci U S A 112:E5533–E5542
Prakriya M, Lewis RS (2015) Store-operated calcium channels. Physiol Rev 95:1383–1436
Putney JW Jr., Steinckwich-Besancon N, Numaga-Tomita T, Davis FM, Desai PN, D’Agostin DM, Wu S, Bird GS (2016) The functions of store-operated calcium channels. Biochim Biophys Acta. doi: 10.1016/j.bbamcr.2016.11.028
Rothberg BS, Wang Y, Gill DL (2013) Orai channel pore properties and gating by STIM: implications from the Orai crystal structure. Sci Signal 6:pe9
Scrimgeour N, Litjens T, Ma L, Barritt GJ, Rychkov GY (2009) Properties of Orai1 mediated store-operated current depend on the expression levels of STIM1 and Orai1 proteins. J Physiol 587:2903–2918
Shim AH, Tirado-Lee L, Prakriya M (2015) Structural and functional mechanisms of CRAC channel regulation. J Mol Biol 427:77–93
Soboloff J, Rothberg BS, Madesh M, Gill DL (2012) STIM proteins: dynamic calcium signal transducers. Nat Rev Mol Cell Biol 13:549–565
Stathopulos PB, Schindl R, Fahrner M, Zheng L, Gasmi-Seabrook GM, Muik M, Romanin C, Ikura M (2013) STIM1/Orai1 coiled-coil interplay in the regulation of store-operated calcium entry. Nat Commun 4:2963
Takahashi Y, Murakami M, Watanabe H, Hasegawa H, Ohba T, Munehisa Y, Nobori K, Ono K, Iijima T, Ito H (2007) Essential role of the N-terminus of murine Orai1 in store-operated Ca2+ entry. Biochem Biophys Res Commun 356:45–52
Tirado-Lee L, Yamashita M, Prakriya M (2015) Conformational changes in the Orai1 C-terminus evoked by STIM1 binding. PLoS One 10:e0128622
Wang X, Wang Y, Zhou Y, Hendron E, Mancarella S, Andrake MD, Rothberg BS, Soboloff J, Gill DL (2014) Distinct Orai-coupling domains in STIM1 and STIM2 define the Orai-activating site. Nat Commun 5:3183
Yang X, Jin H, Cai X, Li S, Shen Y (2012) Structural and mechanistic insights into the activation of Stromal interaction molecule 1 (STIM1). Proc Natl Acad Sci U S A 109:5657–5662
Yen M, Lokteva LA, Lewis RS (2016) Functional analysis of Orai1 concatemers supports a hexameric stoichiometry for the CRAC channel. Biophys J 111:1897–1907
Yuan JP, Zeng W, Dorwart MR, Choi YJ, Worley PF, Muallem S (2009) SOAR and the polybasic STIM1 domains gate and regulate Orai channels. Nat Cell Biol 11:337–343
Zheng H, Zhou MH, Hu C, Kuo E, Peng X, Hu J, Kuo L, Zhang SL (2013) Differential roles of the C and N termini of Orai1 protein in interacting with stromal interaction molecule 1 (STIM1) for Ca2+ release-activated Ca2+ (CRAC) channel activation. J Biol Chem 288:11263–11272
Zhou Y, Meraner P, Kwon HT, Machnes D, Oh-hora M, Zimmer J, Huang Y, Stura A, Rao A, Hogan PG (2010) STIM1 gates the store-operated calcium channel ORAI1 in vitro. Nat Struct Mol Biol 17:112–116
Zhou Y, Srinivasan P, Razavi S, Seymour S, Meraner P, Gudlur A, Stathopulos PB, Ikura M, Rao A, Hogan PG (2013) Initial activation of STIM1, the regulator of store-operated calcium entry. Nat Struct Mol Biol 20:973–981
Zhou Y, Trebak M, Gill DL (2015a) Calcium signals tune the fidelity of transcriptional responses. Mol Cell 58:197–199
Zhou Y, Wang X, Wang X, Loktionova NA, Cai X, Nwokonko RM, Vrana E, Wang Y, Rothberg BS, Gill DL (2015b) STIM1 dimers undergo unimolecular coupling to activate Orai1 channels. Nat Commun 6:8395
Zhou Y, Cai X, Loktionova NA, Wang X, Nwokonko RM, Wang X, Wang Y, Rothberg BS, Trebak M, Gill DL (2016) The STIM1-binding site nexus remotely controls Orai1 channel gating. Nat Commun 7:13725
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Nwokonko, R.M., Cai, X., Loktionova, N.A., Wang, Y., Zhou, Y., Gill, D.L. (2017). The STIM-Orai Pathway: Conformational Coupling Between STIM and Orai in the Activation of Store-Operated Ca2+ Entry. In: Groschner, K., Graier, W., Romanin, C. (eds) Store-Operated Ca²⁺ Entry (SOCE) Pathways. Advances in Experimental Medicine and Biology, vol 993. Springer, Cham. https://doi.org/10.1007/978-3-319-57732-6_5
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DOI: https://doi.org/10.1007/978-3-319-57732-6_5
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