Concurrent strong tyrosine phosphorylation of a 42,000 MW ERK and a 100,000 MW protein is associated with IL-2 production in human Jurkat T cells.

The tyrosine phosphorylated protein(s) responsible for the signalling for interleukin-2 (IL-2) production has not been clearly defined. In this study, the relationship between IL-2 production and the protein tyrosine phosphorylation pattern of human Jurkat T cells was investigated using phosphotyrosine immunoblotting analysis. With anti-CD3 or anti-CD2 activation the cells showed only a low (anti-CD3) or a moderate (anti-CD2) level of tyrosine phosphorylation of a 42,000 MW external signal-regulated kinase (ERK), which was accompanied by undetectable (anti-CD3) or low level (anti-CD2) IL-2 production. In the presence of phorbol myristate acetate (PMA), large amounts of IL-2 were induced by both anti-CD3 and anti-CD2 stimulation, which was accompanied by strong concurrent tyrosine phosphorylation of the 42,000 MW ERK and a 100,000 MW protein. PMA alone, which induced high levels of tyrosine phosphorylation of the ERK protein, neither induced any detectable IL-2 nor increased the level of tyrosine phosphorylation of the 100,000 MW protein. These observations suggest that concurrent tyrosine phosphorylation of the 42,000 MW ERK and a 100,000 MW protein may be required for IL-2 production.