Lymphocyte activation

Releasing the block

Science's STKE  28 Sep 1999:
Vol. 1999, Issue 1, pp. tw5
DOI: 10.1126/stke.1999.1.tw5

The inhibitory effect of cyclic adenosine 3',5'-monophosphate (cAMP) on lymphocyte activation is mediated through cAMP-dependent protein kinase (protein kinase A/PKA). Lymphocyte activation is also negatively regulated by a subgroup of protein tyrosine phosphatases (PTPases) that inactivate MAP kinases. The hematopoietic PTPase, HePTP, is known to bind to and rapidly deactivate the MAP kinases Erk1, Erk2, and p38. Hence, HePTP reduces transcription activation from Erk/p38-dependent promoters. Saxena et al. now report that HePTP is phosphorylated by PKA. This phosphorylation event reduced HePTP interaction with its bound MAP kinase. Release from this inhibition resulted in MAP kinase activation and transcription from the c-fos promoter. Hence, crosstalk between the cAMP/PKA pathway and MAP kinase activation pathways may occur through PTPases in immune cells.

Saxena, M., Williams, S., Tasken, K., Mustelin, T. (1999) Crosstalk between cAMP-dependent kinase and MAP kinase through a protein tyrosine phosphatase. Nature Cell Biol. 1: 305-310. Online Journal