Abstract
Extracellular signal-regulated kinases 1 and 2 (ERK1/2) are a group of kinases that play an important role in proliferation and differentiation. In megakaryocyte-like human erythroleukemia (HEL) cells, ERK2 was found to be predominantly expressed and strongly activated by prostaglandin (PG) E2, thrombin, and epinephrine. On the other hand, adenosine, ADP, ATP, and UTP did not significantly increase ERK1/2 phosphorylation. However, of the agonists tested, only ADP was able to stimulate thymidine uptake. Pretreatment with pertussis toxin abolished the PGE2 response but had less of an effect on thrombin. PGE2- and thrombin-induced ERK1/2 activation was mimicked by 4-β-phorbol-12-myristate-13-acetate and ionomycin and blocked by mitogen-activated protein kinase kinase inhibitor 1,4 diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene but displayed differential sensitivity to protein kinase C inhibitor bisindolylmaleimide I and Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid. Analogs of cAMP or agents that stimulate cAMP production were either weak or ineffective activators. Further studies indicate that the effect of thrombin was blocked by the phosphoinositide 3-kinase inhibitor wortmannin but not by agents inhibiting tyrosine kinase activity. On the contrary, herbimycin, but not wortmannin, attenuated the effect of PGE2. Collectively, these results indicate that ERK1/2 are selectively activated by G protein-coupled receptors and not functionally associated with proliferation in HEL cells. ERK1/2 activation in response to PGE2 and thrombin is mediated by distinctive types of G proteins and is differentially regulated by multiple pathways, including calcium mobilization, protein kinase C, phosphoinositide 3-kinase, and tyrosine kinases.
Footnotes
-
This work was supported in part by a grant from the National Science Council in Taiwan (NSC-86-2314-B-041-010). Portions of this work have been reported in abstract form (Southeast Asian-Western Pacific Regional Meeting of Pharmacologists, Nov 1–5, 1999).
Abbreviations
- ERK
- extracellular signal-regulated kinases
- MAPK
- mitogen-activated protein kinase
- HEL
- erythroleukemia
- BAPTA/AM
- 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid/acetoxymethyl ester
- U0126
- 1,4 diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene
- PG
- prostaglandin
- ANOVA
- analysis of variance
- PMA
- 4-β-phorbol-12-myristate-13-acetate
- [Ca2+]i
- cytosolic free Ca2+concentration
- PI 3-kinase
- phosphoinositide 3-kinase
- MEK
- mitogen-activated protein kinase kinase
- Received June 21, 2001.
- Accepted October 17, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|