Hematopoietic progenitor kinase 1 is a critical component of prostaglandin E2-mediated suppression of the anti-tumor immune response
Prostaglandin E(2) (PGE(2)) is the predominant eicosanoid product released by macrophages at the site of inflammation. Binding of PGE(2) to its cognate 7 transmembrane-spanning G protein-coupled receptors (GPCRs) activates signaling pathways, leading to the synthesis of the Fos transcription factor. Because the Ste20 serine/threonine protein kinase (S/TPK) is a critical signal transducer for the G protein-coupled pheromone receptor in Saccharomyces cerevisiae, we postulated that the PGE(2) GPCRs may activate one of the Ste20 mammalian orthologs. We demonstrate here that the catalytic activity of a hematopoietic cell-restricted, Ste20-related S/TPK, HPK1, is positively regulated by exposure to physiological concentrations of PGE(2). Furthermore, ectopic expression studies implicated HPK1 as a negative regulator of PGE(2)-induced transcription of the fos gene. Our data suggest that PGE(2)-induced activation of HPK1 may represent a novel negative regulatory pathway capable of modulating PGE(2)-mediated gene transcription.