The primary role of B cells, antibody production and antigen elimination, is controlled by the B cell receptor (BCR) complex. BCR crosslinking activates a recently discovered and powerful signaling system mediated by the ER membrane proteins, STIM1 and STIM2. Interacting directly with the PM, STIM proteins expose a reactive domain that avidly binds and traps a specialized family of channel proteins, Orai1, Orai2, and Orai3. The Orai1 channels are exceedingly selective Ca2+ channels that, upon direct binding to STIM sensors, become activated to conduct Ca2+ ions into the junctional cytosolic space. This highly controlled entry of Ca2+ is crucial for two reasons: (i) to replenish Ca2+ within the ER preventing cell stress from protein misfolding, and allowing Ca2+ release signals to be maintained;(ii) to provide longer term and spatially defined Ca2+ signals mediating control over transcription, growth, or apoptosis. The STIM-Orai signaling pathway has particular significance in B cells - the precise coordination of Ca2+ release and entry signals mediates oscillatory Ca2+ signals, the amplitude and duration of which determine how B cells respond to BCR antigen-binding to undergo either proliferation, anergy, or apoptosis. The work combines molecular, biophysical, and cellular approaches to study STIM and Orai proteins using the DT40 B cell line and HEK293 human kidney-derived cells. DT40 B cells retain functional BCR-coupled signaling machinery and we have lines in which each STIM and Orai protein is knocked out. Using these cells our three specific aims are: 1. To examine the distinct functional roles of STIM1 and STIM2 proteins in mediating Ca2+ entry signals. 2. To ascertain how STIM1 and STIM2 proteins interact with and control Orai Ca2+ channels. 3: To examine the STIM-Orai Ca2+ signaling microenvironment in B cells. The studies dissect a novel Ca2+ signaling process fundamentally connected to the BCR-coupled machinery, exerting crucial regulatory control over B cell function. The STIM-Orai signaling pathway and its central role in Ca2+ signal generation in B cells provides a novel and important pharmacological target. The size and duration of Ca2+ signals are primary determinants of B cell fate in response to BCR activ- ation - cell division, maintenance, or, in the case of self-recognition, cell death. Defining the mechanistic operation of this long-acting Ca2+ signaling pathway and examining its pharmacological modification by the borate, 2-APB, provides a target through which B cell function and development can be modified providing the potential to control major immunological diseases including primary B cell deficiencies, lymphoproliferative disorders such as chronic lymphocytic leukemia, and autoimmune diseases.
B cells, the crucial blood cells that produce antibodies and provide immunity, are fundamentally controlled by calcium signals generated by the binding of antigens to the B cell surface. An entirely new signaling pathway involving important regulatory proteins that move throughout the cell, trigger calcium signals that cause control of key B cell functions including growth and differentiation. These new signaling pathways provide vital new targets to pharmacologically control B cell function and development, providing the means to control major immunological diseases including lymphoproliferative disorders such as chronic lymphocytic leukemia and autoimmune diseases.
| Zhou, Yandong; Cai, Xiangyu; Loktionova, Natalia A et al. (2016) The STIM1-binding site nexus remotely controls Orai1 channel gating. Nat Commun 7:13725 |
| Wei, Ming; Zhou, Yandong; Sun, Aomin et al. (2016) Molecular mechanisms underlying inhibition of STIM1-Orai1-mediated Ca2+ entry induced by 2-aminoethoxydiphenyl borate. Pflugers Arch 468:2061-2074 |
| Zhou, Yandong; Wang, Xizhuo; Wang, Xianming et al. (2015) STIM1 dimers undergo unimolecular coupling to activate Orai1 channels. Nat Commun 6:8395 |
| Wang, Xizhuo; Wang, Youjun; Zhou, Yandong et al. (2014) Distinct Orai-coupling domains in STIM1 and STIM2 define the Orai-activating site. Nat Commun 5:3183 |
| Hendron, Eunan; Wang, Xizhuo; Zhou, Yandong et al. (2014) Potent functional uncoupling between STIM1 and Orai1 by dimeric 2-aminodiphenyl borinate analogs. Cell Calcium 56:482-92 |
| Gandhirajan, Rajesh Kumar; Meng, Shu; Chandramoorthy, Harish C et al. (2013) Blockade of NOX2 and STIM1 signaling limits lipopolysaccharide-induced vascular inflammation. J Clin Invest 123:887-902 |
| Rothberg, Brad S; Wang, Youjun; Gill, Donald L (2013) Orai channel pore properties and gating by STIM: implications from the Orai crystal structure. Sci Signal 6:pe9 |
| Mancarella, Salvatore; Potireddy, Santhi; Wang, Youjun et al. (2013) Targeted STIM deletion impairs calcium homeostasis, NFAT activation, and growth of smooth muscle. FASEB J 27:893-906 |
| Soboloff, Jonathan; Rothberg, Brad S; Madesh, Muniswamy et al. (2012) STIM proteins: dynamic calcium signal transducers. Nat Rev Mol Cell Biol 13:549-65 |
| Mancarella, Salvatore; Wang, Youjun; Gill, Donald L (2011) Signal transduction: STIM1 senses both Ca²+ and heat. Nat Chem Biol 7:344-5 |
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