Tyrosine-phosphorylated Vav1 as a point of integration for T-cell receptor- and CD28-mediated activation of JNK, p38, and interleukin-2 transcription.
In this study we identified tyrosine-phosphorylated Vav1 as an early point of integration between the signaling routes triggered by the T-cell receptor and CD28 in human T-cell leukemia cells. Costimulation resulted in a prolonged and sustained phosphorylation and membrane localization of Vav1 in comparison to T-cell receptor activation alone. T-cell stimulation induced the recruitment of Vav1 to an inducible multiprotein T-cell activation signaling complex at the plasma membrane. Vav1 activated the mitogen-activated protein kinases JNK and p38. The Vav1-mediated activation of JNK employed a pathway involving Rac, HPK1, MLK3, and MKK7. The costimulation-induced activation of p38 was inhibited by dominant negative forms of Vav1, Rac, and MKK6. Here we show that Vav1 also induces transcription factors that bind to the CD28RE/AP element contained in the interleukin-2 promoter. A detailed mutational analysis of Vav1 revealed a series of constitutively active and nonfunctional forms of Vav1. Almost all inactive versions were mutated in their Dbl homology domain and behaved as dominant negative mutants that impaired costimulation-induced activation of JNK, p38, and CD28RE/AP-dependent transcription. In contrast to NF-AT-dependent transcription, Vav1-mediated transcriptional induction of the CD28RE/AP element in the interleukin-2 promoter could only partially be inhibited by cyclosporin A, suggesting a dual role of Vav1 for controlling Ca(2+)-dependent and -independent events.
Hehner
S P
SP
German Cancer Research Center (DKFZ), Department of Immunochemistry, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
Hofmann
T G
TG
Dienz
O
O
Droge
W
W
Schmitz
M L
ML
D018106:CD28 Antigens / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D018797:Cell Cycle Proteins; D004789:Enzyme Activation; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics*; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051567:Proto-Oncogene Proteins c-vav; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction; D014158:Transcription, Genetic; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases
D018106:CD28 Antigens; D018797:Cell Cycle Proteins; D007376:Interleukin-2; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D011948:Receptors, Antigen, T-Cell; C496618:VAV1 protein, human; D014443:Tyrosine; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium