Phosphoinositide 3-kinase regulation of T cell receptor-mediated interleukin-2 gene expression in normal T cells.

Phosphoinositide (PI) 3-kinase has been implicated in T cell receptor (TCR) signaling, either as a positive or a negative regulatory molecule. Here, we show that for normal mouse lymph node T cells, PI 3-kinase activity is required for interleukin-2 (IL-2) production following TCR-mediated activation. Furthermore, in normal T cells, inhibition of PI 3-kinase prevented activation of enzymes in the extracellular signal-regulated protein kinase (ERK) signaling pathway (MEK-1 and ERK-2). Overexpression of a dominant-negative mutant of PI 3-kinase and pharmacological inhibitors of PI 3-kinase prevented transcriptional activation of AP-1 and NF-AT, transcription factors regulated by ERK-2 and pivotal for IL-2 gene expression. Although a constitutively active form of Akt kinase, a downstream mediator of PI 3-kinase function, enhanced TCR-induced IL-2 gene transcription, it could not bypass the requirement for PI 3-kinase activity. Therefore, PI 3-kinase is likely to be involved in signaling for IL-2 production in at least two steps in the TCR-initiated signaling pathway.