本研究計畫發現在HEL細胞可經由不同之路徑調節ERK之活性。實驗結果顯示BAPTA,Wortmannin與U0126可阻斷ERK之活化。利用Genistein亦發現其可降低PGE2之作用,但卻對Thrombin之作用較無影響。這些結果顯示PGE主要經由Tyrosine kinases與Ca/sup 2+/活化ERK,而Thrombin受體則需要Protein kinase C,PI-3 kinase和Ca/sup 2+/之參與。 Extracellular signal-regulated kinase (ERK) is a group of proline-directed kinases regulated by growth factors and G protein coupled receptor agonists and thought to play an important role in proliferation and differentiation. Previous experiments in human erythroleukemia (HEL) cells have demonstrated the occurrence and activation of ERK by PGE/sub 2/ and thrombin in a manner dependent on G proteins and protein kinase C. Further exploration of ERK activation in this megakaryocytic cell line has shown that effects of PGE/sub 2/ and thrombin were inhibited after treating cells with BAPTA, a calcium chelator, and U0126, a MAP kinase inhibitor. Treatment of cells with genistein, a tyrosine kinase inhibitor, resulted in reduction of ERK activation by PGE2 but not that of thrombin. A role of PI-3 kinase was also indicated by the data that wortmannin significantly inhibits ERK stimulation. Taken together, these data suggest that ERK could be regulated by multiple pathways and PGE/sub 2/ mediates its effect via mechanisms dependent on tyrosine kinases and Ca/sup 2+/. In contrast, protein kinase C, PI-3 kinase, and Ca/sup 2+/ seem to play a more important role in linking thrombin receptor to stimulation of ERK.
