MPK38 expression is upregulated in immature T cells activated by concanavalin A

We have previously identified a cDNA clone from a murine teratocarcinoma PCC4 cDNA library, which we have termed MPK38 for murine protein kinase 38. MPK38 is a new member of the SNF1 serine/threonine kinase family. To understand the role of the MPK38 in thymocytes, we have investigated the level of MPK38 expression by Northern blot analysis. Interestingly, incubation of thymocytes at 37 degrees C resulted in the loss of the MPK38 transcript, however the transcript could be reinduced by treatment with Con A or PHA, but not with PMA and growth factors such as IL-2, IL-7, TGF-beta, TNF-alpha, and EGF. In addition, stimulation of mature T cells from the spleen with Con A failed to reinduce the MPK38 transcript, indicating a developmental regulation of MPK38 expression, whereas non-T cell populations significantly reinduced the transcript. These results suggest that MPK38 may play a functional role as one of the signal regulators in early T cell activation and, potentially, certain lineages of hematopoietic cell activation induced by Con A.