title: Protein kinase D orchestrates the activation of DRAK2 in response to TCR-induced Ca2+ influx and mitochondrial reactive oxygen generation.
abstract: DRAK2 is a serine/threonine kinase highly enriched in lymphocytes that raises the threshold for T cell activation and maintains T cell survival following productive activation. T cells lacking DRAK2 are prone to activation under suboptimal conditions and exhibit enhanced calcium responses to AgR stimulation. Despite this, mice lacking DRAK2 are resistant to organ-specific autoimmune diseases due to defective autoreactive T cell survival. DRAK2 kinase activity is induced by AgR signaling, and in this study we show that the induction of DRAK2 activity requires Ca(2+) influx through the Ca(2+) release-activated Ca(2+) channel formed from Orai1 subunits. Blockade of DRAK2 activity with the protein kinase D (PKD) inhibitor Gö6976 or expression of a kinase-dead PKD mutant prevented activation of DRAK2, whereas a constitutively active PKD mutant promoted DRAK2 function. Knockdown of PKD in T cells strongly blocked endogenous DRAK2 activation following TCR ligation, implicating PKD as an essential intermediate in the activation of DRAK2 by Ca(2+) influx. Furthermore, we identify DRAK2 as a novel substrate of PKD, and demonstrate that DRAK2 and PKD physically interact under conditions that activate PKD. Mitochondrial generation of reactive oxygen intermediates was necessary and sufficient for DRAK2 activation in response to Ca(2+) influx. Taken together, DRAK2 and PKD form a novel signaling module that controls calcium homeostasis following T cell activation.
authors.affiliation: Institute for Immunology, University of California, Irvine, Irvine, CA 92697, USA.
authors.forename: Ryan H
authors.initials: RH
authors.lastname: Newton
authors.forename: Sabrina
authors.initials: S
authors.lastname: Leverrier
authors.forename: Sonal
authors.initials: S
authors.lastname: Srikanth
authors.forename: Yousang
authors.initials: Y
authors.lastname: Gwack
authors.forename: Michael D
authors.initials: MD
authors.lastname: Cahalan
authors.forename: Craig M
authors.initials: CM
authors.lastname: Walsh
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling / Q000235:genetics / Q000276:immunology*; D002999:Clone Cells; D004789:Enzyme Activation / Q000235:genetics / Q000276:immunology; D006706:Homeostasis / Q000235:genetics / Q000276:immunology; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008928:Mitochondria / Q000276:immunology* / Q000378:metabolism*; D011493:Protein Kinase C / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology
chemical_list: D051017:Apoptosis Regulatory Proteins; D017382:Reactive Oxygen Species; D011948:Receptors, Antigen, T-Cell; C089212:protein kinase D; C495197:Drak2 protein, mouse; D017346:Protein Serine-Threonine Kinases; C115489:STK17B protein, human; D011493:Protein Kinase C