title: Modulation of DRAK2 autophosphorylation by antigen receptor signaling in primary lymphocytes.
abstract: Death-associated protein-related apoptotic kinase-2 (DRAK2), a member of the death-associated protein-like family of serine/threonine kinases, is highly expressed in lymphoid organs and is a negative regulator of T cell activation. To investigate the regulation of DRAK2 activity in primary lymphocytes, we employed mass spectrometry to identify sites of autophosphorylation on DRAK2. These studies have revealed a key site of autophosphorylation on serine 12. Using a phospho-specific antibody to detect Ser(12) phosphorylation, we found that autophosphorylation is induced by antigen receptor stimulation in T and B cells. In Jurkat T cells, resting B cells and thymocytes, DRAK2 was hypophosphorylated on Ser(12) but rapidly phosphorylated with antigen receptor ligation. This increase in phosphorylation was dependent on intracellular calcium mobilization, because BAPTA-AM blocked DRAK2 kinase activity, whereas the SERCA inhibitor thapsigargin promoted Ser(12) phosphorylation. Our results show that DRAK2 kinase activity is regulated in a calcium-dependent manner and that Ser(12) phosphorylation is necessary for optimal suppression of T cell activation by this kinase, suggesting a potential feedback loop may act to modulate the activity of this kinase following antigen receptor signaling.
authors.affiliation: Center for Immunology and Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, California 92697.
authors.forename: Monica L
authors.initials: ML
authors.lastname: Friedrich
authors.affiliation: Departments of Physiology & Biophysics and Developmental & Cell Biology, University of California, Irvine, Irvine, California 92697.
authors.forename: Meng
authors.initials: M
authors.lastname: Cui
authors.affiliation: Center for Immunology and Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, California 92697.
authors.forename: Jeniffer B
authors.initials: JB
authors.lastname: Hernandez
authors.affiliation: Center for Immunology and Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, California 92697.
authors.forename: Brian M
authors.initials: BM
authors.lastname: Weist
authors.affiliation: Center for Immunology and Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, California 92697.
authors.forename: Hilde-Marie
authors.initials: HM
authors.lastname: Andersen
authors.affiliation: Cell Signaling Technology, Inc., Danvers, Massachusetts 01923.
authors.forename: Xiaowu
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Departments of Physiology & Biophysics and Developmental & Cell Biology, University of California, Irvine, Irvine, California 92697; Cancer Research Institute, University of California, Irvine, Irvine, California 92697 and. Electronic address: lanhuang@uci.edu.
authors.forename: Lan
authors.initials: L
authors.lastname: Huang
authors.affiliation: Center for Immunology and Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, California 92697; Cancer Research Institute, University of California, Irvine, Irvine, California 92697 and. Electronic address: cwalsh@uci.edu.
authors.forename: Craig M
authors.initials: CM
authors.lastname: Walsh
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D020013:Calcium Signaling / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D011948:Receptors, Antigen, T-Cell; C495197:Drak2 protein, mouse; D017346:Protein Serine-Threonine Kinases; C115489:STK17B protein, human