title: Autocrine regulation of T-cell activation by ATP release and P2X7 receptors.
abstract: T-cell activation requires the influx of extracellular calcium, although mechanistic details regarding such activation are not fully defined. Here, we show that P2X(7) receptors play a key role in calcium influx and downstream signaling events associated with the activation of T cells. By real-time PCR and immunohistochemistry, we find that Jurkat T cells and human CD4(+) T cells express abundant P2X(7) receptors. We show, using a novel fluorescent microscopy technique, that T-cell receptor (TCR) stimulation triggers the rapid release of ATP (<100 microM). This release of ATP is required for TCR-mediated calcium influx, NFAT activation, and interleukin-2 (IL-2) production. TCR activation up-regulates P2X(7) receptor gene expression. Removal of extracellular ATP by apyrase or alkaline phosphatase treatment, inhibition of ATP release with the maxi-anion channel blocker gadolinium chloride, or siRNA silencing of P2X(7) receptors blocks calcium entry and inhibits T-cell activation. Moreover, lymphocyte activation is impaired in C57BL/6 mice that express poorly functional P2X(7) receptors, compared to control BALB/c mice, which express fully functional P2X(7) receptors. We conclude that ATP release and autocrine, positive feedback through P2X(7) receptors is required for the effective activation of T cells.
authors.affiliation: Department of Surgery, University of California San Diego, San Diego, California, USA.
authors.forename: Linda
authors.initials: L
authors.lastname: Yip
authors.forename: Tobias
authors.initials: T
authors.lastname: Woehrle
authors.forename: Ross
authors.initials: R
authors.lastname: Corriden
authors.forename: Mark
authors.initials: M
authors.lastname: Hirsh
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Inoue
authors.forename: Vhe
authors.initials: V
authors.lastname: Ferrari
authors.forename: Paul A
authors.initials: PA
authors.lastname: Insel
authors.forename: Wolfgang G
authors.initials: WG
authors.lastname: Junger
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D019898:Autocrine Communication / Q000502:physiology*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics / Q000378:metabolism; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D051379:Mice; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7
chemical_list: D007376:Interleukin-2; D050778:NFATC Transcription Factors; C546468:P2RX7 protein, human; C546469:P2rx7 protein, mouse; D034741:RNA, Small Interfering; D011948:Receptors, Antigen, T-Cell; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate; D002118:Calcium