Kinetics of c-Fos induction depends upon strength of TCR stimulation. (63.13)

Abstract

Abstract Induction of immediate early genes (like Fos, Jun) in response to T cell receptor stimulation with different MHC-peptide (MHC-p) dose and potency is not well understood. Our aim is to study the kinetics of c-Fos induction in T cells in response to antigen dose and potency. Our model system is AND TCR transgenic mice, whose T cells are specific for moth Cytochrome-C (MCC) peptide. We study the impact of MHC-p potency using altered peptide ligands (APLs). To study c-Fos induction we crossed AND mice to c-Fos-EGFP transgenic mice that express a fusion protein of c-Fos and EGFP driven by the Fos promoter. We observed that upon stimulation of TCR, expression of c-Fos starts after ~30 min, peaks at 3hrs and plateaus for another 2hrs. Strong agonists induce c-Fos even without co-stimulatory molecules where as weak agonists fail to do so. Co-stimulation enhances the percentage of cells responding as well as the level of c-Fos expression. Highering or lowering the peptide dose reduces the expression level of c-Fos. Inhibiton of Calcineurin has no effect on c-Fos expression. Experiment with MAPK inhibitors indicates that all the three MAP Kinases- ERK, p38 and JNK regulate c-Fos induction. ERK primarily regulate c-fos expression in the case of strong agonists (MCC and L98A) where as JNK primarily regulates c-fos expression in case of weak agonists (K99A). We are looking at other regulators of c-Fos induction in response to APLs.