title: hnRNP-K is a nuclear target of TCR-activated ERK and required for T-cell late activation.
abstract: Sustained extracellular signal-regulated kinase (ERK)-signaling plays a critical role in T-cell-mediated IL-2 production. Although many downstream targets are known for ERK, details remain unknown about which molecules play functional roles in IL-2 production. Here, we addressed this question using proteomic analysis of nuclear proteins from TCR-activated T cells and identified hnRNP-K as one of the ERK targets essential for IL-2 production. hnRNP-K was previously shown by others to be a direct substrate of ERK and form complexes with multiple signaling proteins as well as DNA and RNA. Our data showed a clear ERK-dependent increase in one form of hnRNP-K after TCR stimulation. Small interfering RNA-mediated gene knockdown of hnRNP-K expression abrogated IL-2 production by T cells. Moreover, reduction of hnRNP-K expression caused a notable increase in proteolysis of Vav1, a binding target of hnRNP-K. Since Vav1 is an essential molecule for T-cell activation, the data suggest that ERK signaling is required for T-cell activation partly by inhibiting activation-induced proteolysis of Vav1.
authors.affiliation: Department of Medicine, Immunotherapy Center, Medical College of Georgia, Augusta, GA 30912-2600, USA.
authors.forename: Jing-Wen
authors.initials: JW
authors.lastname: Chang
authors.forename: Toru
authors.initials: T
authors.lastname: Koike
authors.forename: Makio
authors.initials: M
authors.lastname: Iwashima
mesh_terms: D000818:Animals; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D034641:Heterogeneous-Nuclear Ribonucleoprotein K / Q000378:metabolism*; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D051567:Proto-Oncogene Proteins c-vav / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
chemical_list: D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D007376:Interleukin-2; D051567:Proto-Oncogene Proteins c-vav; D011948:Receptors, Antigen, T-Cell; C496618:VAV1 protein, human; D048049:Extracellular Signal-Regulated MAP Kinases