Stoichiometric requirements for trapping and gating of Ca2+ release-activated Ca2+ (CRAC) channels by stromal interaction molecule 1 (STIM1)

Store-operated Ca2+ entry depends critically on physical interactions of the endoplasmic reticulum (ER) Ca2+ sensor stromal interaction molecule 1 (STIM1) and the Ca2+ release-activated Ca2+ (CRAC) channel protein Orai1. Recent studies support a diffusion-trap mechanism in which ER Ca2+ depletion causes STIM1 to accumulate at ER-plasma membrane (PM) junctions, where it binds to Orai1, trapping and activating mobile CRAC channels in the overlying PM. To determine the stoichiometric requirements for CRAC channel trapping and activation, we expressed mCherry-STIM1 and Orai1-GFP at varying ratios in HEK cells and quantified CRAC current (ICRAC) activation and the STIM1:Orai1 ratio at ER-PM junctions after store depletion. By competing for a limited amount of STIM1, high levels of Orai1 reduced the junctional STIM1:Orai1 ratio to a lower limit of 0.3–0.6, indicating that binding of one to two STIM1s is sufficient to immobilize the tetrameric CRAC channel at ER-PM junctions. In cells expressing a constant amount of STIM1, CRAC current was a highly nonlinear bell-shaped function of Orai1 expression and the minimum stoichiometry for channel trapping failed to evoke significant activation. Peak current occurred at a ratio of ∼2 STIM1:Orai1, suggesting that maximal CRAC channel activity requires binding of eight STIM1s to each channel. Further increases in Orai1 caused channel activity and fast Ca2+-dependent inactivation to decline in parallel. The data are well described by a model in which STIM1 binds to Orai1 with negative cooperativity and channels open with positive cooperativity as a result of stabilization of the open state by STIM1.

[1]  P. Rosenberg,et al.  The role of store-operated calcium influx in skeletal muscle signaling. , 2011, Cell calcium.

[2]  Tao Xu,et al.  Graded activation of CRAC channel by binding of different numbers of STIM1 to Orai1 subunits , 2011, Cell Research.

[3]  Elizabeth D. Covington,et al.  Essential Role for the CRAC Activation Domain in Store-dependent Oligomerization of STIM1 , 2010, Molecular biology of the cell.

[4]  Y. Gwack,et al.  A novel EF-hand protein, CRACR2A, is a cytosolic Ca2+ sensor that stabilizes CRAC channels in T cells , 2010, Nature Cell Biology.

[5]  P. Hogan,et al.  Molecular basis of calcium signaling in lymphocytes: STIM and ORAI. , 2010, Annual review of immunology.

[6]  Y. Gwack,et al.  The Intracellular Loop of Orai1 Plays a Central Role in Fast Inactivation of Ca2+ Release-activated Ca2+ Channels* , 2009, The Journal of Biological Chemistry.

[7]  W. Nickel,et al.  A Conserved, Lipid‐Mediated Sorting Mechanism of Yeast Ist2 and Mammalian STIM Proteins to the Peripheral ER , 2009, Traffic.

[8]  M. Chvanov,et al.  Role of phosphoinositides in STIM1 dynamics and store-operated calcium entry , 2009, The Biochemical journal.

[9]  R. Dolmetsch,et al.  STIM1 and calmodulin interact with Orai1 to induce Ca2+-dependent inactivation of CRAC channels , 2009, Proceedings of the National Academy of Sciences.

[10]  P. Worley,et al.  Molecular determinants of fast Ca2+-dependent inactivation and gating of the Orai channels , 2009, Proceedings of the National Academy of Sciences.

[11]  C. Romanin,et al.  A Ca2+ Release-activated Ca2+ (CRAC) Modulatory Domain (CMD) within STIM1 Mediates Fast Ca2+-dependent Inactivation of ORAI1 Channels*♦ , 2009, The Journal of Biological Chemistry.

[12]  G. Barritt,et al.  Properties of Orai1 mediated store‐operated current depend on the expression levels of STIM1 and Orai1 proteins , 2009, The Journal of physiology.

[13]  Marko Popovic,et al.  Dependence of STIM1/Orai1-mediated Calcium Entry on Plasma Membrane Phosphoinositides* , 2009, The Journal of Biological Chemistry.

[14]  Elizabeth D. Covington,et al.  STIM1 Clusters and Activates CRAC Channels via Direct Binding of a Cytosolic Domain to Orai1 , 2009, Cell.

[15]  Joseph P. Yuan,et al.  SOAR and the polybasic STIM1 domains gate and regulate the Orai channels , 2009, Nature Cell Biology.

[16]  Shenyuan L. Zhang,et al.  The CRAC channel consists of a tetramer formed by Stim-induced dimerization of Orai dimers , 2008, Nature.

[17]  Murali Prakriya,et al.  Oligomerization of STIM1 couples ER calcium depletion to CRAC channel activation , 2008, Nature.

[18]  H. Kahr,et al.  Dynamic Coupling of the Putative Coiled-coil Domain of ORAI1 with STIM1 Mediates ORAI1 Channel Activation* , 2008, Journal of Biological Chemistry.

[19]  O. Mignen,et al.  Orai1 subunit stoichiometry of the mammalian CRAC channel pore , 2008, The Journal of physiology.

[20]  Tao Xu,et al.  Mapping the Interacting Domains of STIM1 and Orai1 in Ca2+ Release-activated Ca2+ Channel Activation* , 2007, Journal of Biological Chemistry.

[21]  S. Feske.  Calcium signalling in lymphocyte activation and disease , 2007, Nature Reviews Immunology.

[22]  Tobias Meyer,et al.  Live-cell imaging reveals sequential oligomerization and local plasma membrane targeting of stromal interaction molecule 1 after Ca2+ store depletion , 2007, Proceedings of the National Academy of Sciences.

[23]  Tao Xu,et al.  Aggregation of STIM1 underneath the plasma membrane induces clustering of Orai1. , 2006, Biochemical and biophysical research communications.

[24]  M. Ikura,et al.  Stored Ca2+ Depletion-induced Oligomerization of Stromal Interaction Molecule 1 (STIM1) via the EF-SAM Region , 2006, Journal of Biological Chemistry.

[25]  M. Iino,et al.  Coupling of STIM1 to store-operated Ca2+ entry through its constitutive and inducible movement in the endoplasmic reticulum , 2006, Proceedings of the National Academy of Sciences.

[26]  JoAnn Buchanan,et al.  The elementary unit of store-operated Ca2+ entry: local activation of CRAC channels by STIM1 at ER–plasma membrane junctions , 2006, The Journal of cell biology.

[27]  JoAnn Buchanan,et al.  Ca2+ store depletion causes STIM1 to accumulate in ER regions closely associated with the plasma membrane , 2006, The Journal of cell biology.

[28]  Richard S Lewis,et al.  Regulation of CRAC Channel Activity by Recruitment of Silent Channels to a High Open-probability Gating Mode , 2006, The Journal of general physiology.

[29]  Rebecca R. Boyles,et al.  Large Store-operated Calcium Selective Currents Due to Co-expression of Orai1 or Orai2 with the Intracellular Calcium Sensor, Stim1* , 2006, Journal of Biological Chemistry.

[30]  J. Soboloff,et al.  Orai1 and STIM Reconstitute Store-operated Calcium Channel Function* , 2006, Journal of Biological Chemistry.

[31]  M. Nadler,et al.  Amplification of CRAC current by STIM1 and CRACM1 (Orai1) , 2006, Nature Cell Biology.

[32]  T. Deerinck,et al.  STIM1 is a Ca2+ sensor that activates CRAC channels and migrates from the Ca2+ store to the plasma membrane , 2005, Nature.

[33]  Tobias Meyer,et al.  STIM Is a Ca2+ Sensor Essential for Ca2+-Store-Depletion-Triggered Ca2+ Influx , 2005, Current Biology.

[34]  S. Wagner,et al.  STIM1, an essential and conserved component of store-operated Ca2+ channel function , 2005, The Journal of cell biology.

[35]  J. Putney,et al.  Store-operated calcium channels. , 2005, Physiological reviews.

[36]  E. Sigel,et al.  Subunit Arrangement of γ-Aminobutyric Acid Type A Receptors* , 2001, The Journal of Biological Chemistry.

[37]  Christopher C. Goodnow,et al.  Differential activation of transcription factors induced by Ca2+ response amplitude and duration , 1997, Nature.

[38]  R. Lewis,et al.  Rapid inactivation of depletion-activated calcium current (ICRAC) due to local calcium feedback , 1995, The Journal of general physiology.

[39]  R. Dolmetsch,et al.  Signaling between intracellular Ca2+ stores and depletion-activated Ca2+ channels generates [Ca2+]i oscillations in T lymphocytes , 1994, The Journal of general physiology.

[40]  R. Penner,et al.  Calcium release‐activated calcium current in rat mast cells. , 1993, The Journal of physiology.

[41]  M. Tanouye,et al.  Tandem linkage of Shaker K+ channel subunits does not ensure the stoichiometry of expressed channels. , 1992, Biophysical journal.

[42]  M. Ikura,et al.  Stored Ca 2 Depletion-induced Oligomerization of Stromal Interaction Molecule 1 ( STIM 1 ) via the EF-SAM Region AN INITIATION MECHANISM FOR CAPACITIVE Ca 2 ENTRY * , 2006 .

[43]  Tobias Meyer,et al.  STIM Is a Ca 2+ Sensor Essential for Ca 2+ -Store-Depletion-Triggered Ca 2+ Influx , 2005 .