SLP-76 and Vav function in separate, but overlapping pathways to augment interleukin-2 promoter activity

SLP-76 and Vav, two hematopoietic cell specific molecules, are critical for T cell development and activation. Following T cell antigen receptor stimu lation, SLP-76 and Vav both undergo tyrosine phosphorylation and associate with each other via the SH2 domain of Vav and phosphorylated tyrosines of S LP-76, Furthermore, SLP-76 and Vav have a synergistic effect on interleukin (IL)-2 promoter activity in T cells. In this report, we show that two tyro sines, Tyr-113 and Tyr-128, of SLP-76 are required for its binding to Vav, both in vitro and in intact cells. Surprisingly, we find also that the inte raction between SLP-76 and Vav is not required for their cooperation in aug menting IL-2 promoter activity, as the two molecules appear to function in different signaling pathways upstream of IL-2 gene expression. Overexpressi on of SLP-76 in the Jurkat T cell line potentiates the activities of both n uclear factor of activated T cells and AP-1 transcription factors, In contr ast, overexpression of Vav leads to enhanced nuclear factor of activated T cells activity without affecting AP-1, Additionally, overexpression of Vav, but not SLP-76, augments CD28-induced IL-2 promoter activity. These findin gs suggest that the synergy between SLP-76 and Vav in regulating IL-2 gene expression reflects the cooperation between different signaling pathways.