The Mekk2 Participate In And Modulation Of T Cell Receptor Signal Transduction, As Well As Corticosteroids Human Lung Fibroblasts Mapk

1. MEKK2 Is Required for T-cell Receptor Signals in JNK Activation and Interleukin-2 Gene ExpressionThe c-Jun N-terminal kinases (JNKs) are members of the mitogen-activated protein kinase (MAPK) gene family and are essential for cell proliferation, differentiation, and apoptosis. Previously we found that activation of JNK in T-cells required co stimulation of both T-cell receptor and auxiliary receptors such as CD28. In this study, we want to demonstrate that MEK kinase (MEKK) 2 was a major upstream MAPK kinase kinase for the JNK cascade in T-cells.Northern Blot was used to analyses MEKK2 mRNA in tissues with a 1-kilobase-cDNA probe from the N-terminal region of human MEKK2. Jakurt and COS-1 Cells were transfected by electroporation and Lipo-fectAMINE with various Plasmids. JNK and MEKK2 kinase activities were tested in Vitro Kinase Assay incorporated with P- ATP. Luciferase Reporter Gene Assay was performed for analysis IL-2 and AP-1 expressionsThe results indicated that MEKK2 was ubiquitously expressed, with the highest level in peripheral blood leukocytes. In T cells, MEKK2 was found to be a strong activator of JNK and to activate JNK-dependent AP-1 reporter gene expression. MEKK2 also synergized with anti-CD3 antibody to activate JNK in T cells, and stimulation of T cells led to induction of MEKK2 tyrosine phosphorylation. Significantly, the JNK activation induced by anti-CD3 and anti-CD28 antibodies, but not by 12-O-tetradecano-ylphorbol-13-acetate and Ca²⁺ ionophore A23187. It was inhibited by dominant negative MEKK2 mutants. AP-1 and interleukin-2 reporter gene induction in T-cells was also inhibited by dominant negative MEKK2 mutants. Taken together, our results showed that human MEKK2 is a key signaling molecule for T-cell receptor/CD3-mediated JNK MAPK activation and interleukin-2 gene expression.