Submitted April 21, 2008
Accepted November 3, 2008
Genetic disruption of p38
Tyr-323 phosphorylation prevents TCR-mediated p38 activation and impairs IFN-
production
Ludmila Jirmanova, Dandapantula N Sarma, Dragana Jankovic, Paul R Mittelstadt, and Jonathan D Ashwell*
Laboratory of Immune Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
* Corresponding author; email: jda{at}pop.nci.nih.gov.
T cells possess a p38 activation alternative pathway in which stimulation via the antigen receptor (TCR) induces phosphorylation of p38
and 
on Tyr-323. To assess the contribution of this pathway to normal T cell function, we generated p38 "knock-in" mice in which Tyr-323 was replaced with Phe (p38Y323F). TCR-mediated stimulation failed to activate p38Y323F as measured by phosphorylation of the Thr-Glu-Tyr activation motif and p38 catalytic activity. Cell cycle entry was delayed in TCR-stimulated p38Y323F T cells, which also produced less IFN-
than wild type T cells in response to TCR-mediated but not TCR-independent stimuli. p38Y323F mice immunized with T helper 1 (Th1)-inducing antigens generated normal Th1 effector cells, but these cells produced less IFN- than wild type cells when stimulated through the TCR. Thus, the Tyr-323-dependent pathway and not the classic MAP kinase cascade is the physiologic means of p38 activation through the TCR, and is necessary for normal Th1 function but not Th1 generation.
