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Alternative p38 activation pathway mediated by T cell receptor–proximal tyrosine kinases


Signaling-responsive MAP kinases (MAPKs) are key in mediating immune responses and are activated through the phosphorylation of a Thr-X-Tyr motif by upstream MAPK kinases. Here we show that T cells stimulated through the T cell receptor (TCR) used an alternative mechanism in which p38 was phosphorylated on Tyr323 and subsequently autophosphorylated residues Thr180 and Tyr182. This required the TCR-proximal tyrosine kinase Zap70 but not the adaptor protein LAT, which was required for activation of extracellular signal–regulated protein kinase MAPKs. TCR activation of p38 lacking Tyr323 was diminished, and blocking of p38 activity prevented p38 dual phosphorylation in normal T cells but not in B cells. Thus, phosphorylation of Tyr323 dependent on the tyrosine kinase Lck and mediated by Zap70 serves as an important mechanism for TCR activation of p38 in T cells.

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We thank S. Gutkind for critical review of this manuscript.

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Competing interests

The authors declare no competing financial interests.

Correspondence to Jonathan D Ashwell.

Supplementary information

Supplementary Fig. 1

SB203580 inhibits T cell p38 autophosphorylation. (PDF 148 kb)

Supplementary Fig. 2

Zap70 phosphorylates p38 on Try-323. (PDF 53 kb)

Supplementary Fig. 3

Specificity of affinity-purified anti-phospho-323 p38 antibody. (PDF 92 kb)

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Figure 1: The p38 from activated T cells but not B cells autophosphorylates.
Figure 2: Analysis of TCR-induced p38 and Erk phosphorylation in wild-type and signaling-defective Jurkat T cells.
Figure 3: Lck, Fyn, and Zap70 activate p38 even in the absence of Tyr182 phosphorylation.
Figure 4: Tyr323 phosphorylation and activation of p38.
Figure 5: Phosphorylation of Tyr323 by p38 in vivo.
Figure 6: TCR-induced p38 phosphorylation is Zap70 dependent, and Tyr323 is required for TCR- but not PMA-mediated activation of T cell p38.