Rapid activation of MAP kinase by estrogen in the bone cell line.
We examined the effect of estrogen on mitogen-activated protein kinase (MAPK) in osteoblastic cells. Rat ROS 17/2.8 cells were exposed to 17beta-estradiol (E2) and MAPK activity in the cells was measured by an in vitro phosphorylation assay. E2 treatment caused a rapid and transient MAPK activation within 5 min. Insulin-like growth factor-I, which acts via their membrane receptors, caused a similar effect, but it required 10 min to reach the maximum level. Western blot analyses with anti-MAPK and anti-phosphotyrosine antibodies demonstrated that the E2 activation of MAPK was accompanied by phosphorylation of the enzyme. The concentration range (10 nM-1 pM) of E2 needed for this MAPK activation was less than that (1 microM-0.1 nM) needed for the transcriptional activation via the nuclear estrogen receptor (ER). These data provide the first evidence of MAPK activation by E2 through phosphorylation, which may be mediated through a putative plasma membrane receptor in the cultured bone cells.
Endoh
H
H
Molecular Medicine Lab, Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co., Ltd., Tsukuba, Ibaraki, Japan. endoh@yamanouchi.co.jp
Sasaki
H
H
Maruyama
K
K
Takeyama
K
K
Waga
I
I
Shimizu
T
T
Kato
S
S
Kawashima
H
H
D000818:Animals; D000906:Antibodies / Q000276:immunology; D015153:Blotting, Western; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000276:immunology / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation; D004958:Estradiol / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D010006:Osteoblasts / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000276:immunology; D051381:Rats; D011960:Receptors, Estrogen / Q000378:metabolism
D000906:Antibodies; D011960:Receptors, Estrogen; D019000:Phosphotyrosine; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D017871:Calcium-Calmodulin-Dependent Protein Kinases