Calcium Signals and Protein Tyrosine Kinases Are Required for the Induction of c- jun in Jurkat Cells Stimulated by the T Cell-Receptor Complex and Oxidative Signals

Abstract

The regulation of c-jun plays an important role in T cell activation, proliferation, and expression of interleukin-2. In the present study, we determined whether Ca²⁺ signals and the activity of protein tyrosine kinases (PTKs) were required for the induction of c-jun in Jurkat cells stimulated with cross-linked anti-T cell receptor/CD3 antibodies or exposed to oxidative stress in the form of micromolar concentrations of H₂O₂. Jurkat cells exhibited rapid elevations in intracellular calcium [Ca²⁺]_i levels in response to H₂O₂ and cross-linked anti-CD3 antibodies that mainly reflected the influx of extracellular Ca²⁺. The Ca²⁺ flux in response to oxidative signals was distinguished by an exquisite sensitivity to inhibition with Ni²⁺, suggesting the involvement of cation channels. PTK activity was needed for [Ca²⁺]_i elevations in response to both oxidative and anti-CD3 signals, although H₂O₂ induction of [Ca²⁺]_i increases was more resistant to inhibition by genistein than anti-CD3 [Ca²⁺]_i responses. Both oxidative signals and anti-CD3 stimulation induced increased levels of c-jun and c-fos mRNA. The increased expression of c-jun with H₂0₂ was preceded by [Ca²⁺]_i increases and accompanied by activation of c-Jun aminoterminal kinases (JNKs), as well as increased AP-1 binding activity. Induction of c-jun with oxidative signals and anti-CD3 was also shown to be crucially dependent on [Ca²⁺]_i elevations because the chelation of [Ca²⁺]_i with BAPTA resulted in a dose-dependent inhibition of c-jun expression. Furthermore, inhibition studies demonstrated that the optimal induction of c-jun mRNA in response to oxidative signals required PTK as well as protein kinase C (PKC). Thus, these findings suggest that both [Ca²⁺]_i signals and the activity of PTKs are essential for the optimal expression of c-jun in response to TCR/CD3 signals and changes in redox potentials.