Activation of MEK 1/2 and p42/44 MAPK by angiotensin II in hepatocyte nucleus and their potentiation by ethanol.
Hepato-subcellular effect of angiotensin II (Ang II) and ethanol on the p42/44 mitogen-activated protein kinase (MAPK) and MAPK kinase (MEK 1/2) was investigated in the nucleus of rat hepatocytes. Hepatocytes were treated with ethanol (100 mM) for 24h and stimulated with Ang II (100 nM, 5 min). The levels of p42/44 MAPK and MEK 1/2 were monitored in the nuclear fraction using antibodies. Ang II itself caused significant accumulation of phosphorylated p42/44 MAPK (phospho-p42/44 MAPK) in the nucleus without any significant translocation of p42/44 MAPK protein thereby suggesting activation of p42/44 MAPK in the nucleus. Ang II caused marked accumulation of phosphorylated MEK 1/2 (phospho-MEK 1/2) in the nucleus without any significant accumulation of MEK 1/2 protein. Ratio of phospho-MEK 1/2 to MEK 1/2 protein in the nucleus after Ang II treatment was 2.4 times greater than control suggesting phosphorylation of MEK 1/2 inside the nucleus. Ethanol had no effect on the protein level or the activation of p42/44 MAPK in the nucleus. Ethanol treatment potentiated nuclear activation of p42/44 MAPK by Ang II but not translocation of p42/44 MAPK protein. This was accompanied by potentiation of Ang II-stimulated accumulation of phospho-MEK 1/2 in the nucleus by ethanol. MEK 1/2 inhibitor, U-0126 inhibited Ang II response and its potentiation by ethanol. These results suggest that Ang II-mediated accumulation of phospho-p42/44 MAPK in the hepatocyte nucleus involves MEK 1/2-dependent activation and this effect is potentiated by ethanol.
Aroor
Annayya R
AR
Department of Medical Pharmacology and Physiology, School of Medicine, University of Missouri, Columbia, MO 65212, USA.
Lee
Youn Ju
YJ
Shukla
Shivendra D
SD
D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D002478:Cells, Cultured; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D000431:Ethanol / Q000494:pharmacology*; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology; D048369:MAP Kinase Kinase 1 / Q000378:metabolism*; D048370:MAP Kinase Kinase 2 / Q000378:metabolism*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000804:Angiotensin II; D000431:Ethanol; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2