title: DRAK2, a lymphoid-enriched DAP kinase, regulates the TCR activation threshold during thymocyte selection.
abstract: DAP kinases are a family of serine/threonine kinases known to regulate intrinsic apoptotic processes. DAP-related apoptotic kinase-2 (DRAK2) is highly expressed in lymphoid organs, with differential expression during thymocyte development. Low levels of transcript were observed in CD4/CD8 double-positive (DP) and double-negative populations, whereas single-positive thymocytes possessed elevated levels. Ex vivo stimulation of DP thymocytes with phorbol myristate acetate or antibodies that activate the TCR complex led to the accumulation of DRAK2 in a protein kinase C- and MAP Kinase-dependent fashion. Although DAP kinase family members are thought to potentiate apoptosis, ectopic expression of DRAK2 using retroviral transduction of primary T cells and NIH3T3 fibroblasts failed to decrease rates of survival, suggesting that DRAK2 expression is not sufficient to promote apoptosis. Rather, our results demonstrate that DRAK2 is a primary response gene activated by TCR stimulation in DP thymocytes. Further, we observed that DRAK2 controlled the threshold for calcium signaling in the thymus since positively selected Drak2-deficient thymocytes displayed a reduced requirement for TCR cross-linking. These findings are consistent with a role for DRAK2 in thymocyte selection and lymphoid maturation, and demonstrate that DRAK2 transduces non-apoptotic signals during thymocyte differentiation.
authors.affiliation: Department of Molecular Biology and Biochemistry, Center for Immunology, University of California-Irvine, Irvine, CA 92697-3900, USA.
authors.forename: Monica L
authors.initials: ML
authors.lastname: Friedrich
authors.forename: Ben G
authors.initials: BG
authors.lastname: Wen
authors.forename: Gretchen
authors.initials: G
authors.lastname: Bain
authors.forename: Barbara L
authors.initials: BL
authors.lastname: Kee
authors.forename: Carol
authors.initials: C
authors.lastname: Katayama
authors.forename: Cornelis
authors.initials: C
authors.lastname: Murre
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Hedrick
authors.forename: Craig M
authors.initials: CM
authors.lastname: Walsh
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D020013:Calcium Signaling / Q000235:genetics / Q000276:immunology; D002470:Cell Survival / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000235:genetics / Q000276:immunology*; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology*; D051379:Mice; D041681:NIH 3T3 Cells; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000276:immunology*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology
chemical_list: D011948:Receptors, Antigen, T-Cell; C495197:Drak2 protein, mouse; D017346:Protein Serine-Threonine Kinases