title: Junctophilin-4, a component of the endoplasmic reticulum-plasma membrane junctions, regulates Ca2+ dynamics in T cells.
abstract: Orai1 and stromal interaction molecule 1 (STIM1) mediate store-operated Ca(2+) entry (SOCE) in immune cells. STIM1, an endoplasmic reticulum (ER) Ca(2+) sensor, detects store depletion and interacts with plasma membrane (PM)-resident Orai1 channels at the ER-PM junctions. However, the molecular composition of these junctions in T cells remains poorly understood. Here, we show that junctophilin-4 (JP4), a member of junctional proteins in excitable cells, is expressed in T cells and localized at the ER-PM junctions to regulate Ca(2+) signaling. Silencing or genetic manipulation of JP4 decreased ER Ca(2+) content and SOCE in T cells, impaired activation of the nuclear factor of activated T cells (NFAT) and extracellular signaling-related kinase (ERK) signaling pathways, and diminished expression of activation markers and cytokines. Mechanistically, JP4 directly interacted with STIM1 via its cytoplasmic domain and facilitated its recruitment into the junctions. Accordingly, expression of this cytoplasmic fragment of JP4 inhibited SOCE. Furthermore, JP4 also formed a complex with junctate, a Ca(2+)-sensing ER-resident protein, previously shown to mediate STIM1 recruitment into the junctions. We propose that the junctate-JP4 complex located at the junctions cooperatively interacts with STIM1 to maintain ER Ca(2+) homeostasis and mediate SOCE in T cells.
authors.affiliation: Department of Physiology, David Geffen School of Medicine at the University of California, Los Angeles, Los Angeles, CA 90095;
authors.forename: Jin Seok
authors.initials: JS
authors.lastname: Woo
authors.affiliation: Department of Physiology, David Geffen School of Medicine at the University of California, Los Angeles, Los Angeles, CA 90095;
authors.forename: Sonal
authors.initials: S
authors.lastname: Srikanth
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Miyuki
authors.initials: M
authors.lastname: Nishi
authors.affiliation: Department of Physiology, David Geffen School of Medicine at the University of California, Los Angeles, Los Angeles, CA 90095;
authors.forename: Peipei
authors.initials: P
authors.lastname: Ping
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takeshima
authors.affiliation: Department of Physiology, David Geffen School of Medicine at the University of California, Los Angeles, Los Angeles, CA 90095; ygwack@mednet.ucla.edu.
authors.forename: Yousang
authors.initials: Y
authors.lastname: Gwack
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D007365:Intercellular Junctions / Q000378:metabolism; D019169:Jurkat Cells; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071737:Stromal Interaction Molecule 1; D013601:T-Lymphocytes / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D015220:Calcium Channels; C481843:Jph4 protein, mouse; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C100757:Stim1 protein, mouse; D000071737:Stromal Interaction Molecule 1
keywords: ER–PM junctions; Orai1; STIM1; junctophilins; store-operated Ca2+ entry