Protein kinase Cα1, a major regulator of TCR-CD28-activated signal transduction leading to IL-2 gene transcription and secretion

Abstract

The aim of this study was to investigate the influence of protein kinase C (PKC) α and β on the TCR-CD28-stimulated protein kinase cascades participating in regulation of IL-2 gene transcription and secretion. Inhibition of the synthesis of PKCα and β by specific phosphorothioate-modified antisense oligonucleotides (ODN) resulted in suppression of phosphorylation and activation of Raf-1, mitogen-activated extracellular-regulated kinase kinases and extracellular-regulated kinases in stimulated Jurkat T cells. Furthermore, a marked reduction of IκB kinase-α-catalyzed IκBα phosphorylation was observed in both PKCα- and β-specific antisense oligonucleotide-treated cells. In sharp contrast, TCR-CD28-stimulated phosphorylation and activation of the Jun-N-terminal kinase (JNK) cascade was specifically suppressed upon treatment with PKCβ-specific antisense ODN, suggesting that PKCβ was a specific upstream regulator of the JNK protein kinase cascade. Significant inhibition of high-affinity NF-AT binding and transactivation, IL-2 gene expression, reduction of IL-2 mRNA synthesis, and, most impressively, a complete suppression of IL-2 secretion were observed in PKCβ antisense ODN-treated cells. The data indicate a highly specific function of PKCβ for regulation of TCR-CD28 induced-signaling, IL-2 gene expression and secretion in Jurkat T cells.