title: Activation of the mitogen-activated protein kinase cascade by pertussis toxin-sensitive and -insensitive pathways in cultured ventricular cardiomyocytes.
abstract: The involvement of pertussis toxin (PTX)-sensitive and -insensitive pathways in the activation of the mitogen-activated protein kinase (MAPK) cascade was examined in ventricular cardiomyocytes cultured from neonatal rats. A number of agonists that activate heterotrimeric G-protein-coupled receptors stimulated MAPK activity after exposure for 5 min. These included foetal calf serum (FCS), endothelin-1 (these two being the most effective of the agonists examined), phenylephrine, endothelin-3, lysophosphatidic acid, carbachol, isoprenaline and angiotensin II. Activation of MAPK and MAPK kinase (MEK) by carbachol returned to control levels within 30-60 min, whereas activation by FCS was more sustained. FPLC on Mono Q showed that carbachol and FCS activated two peaks of MEK and two peaks of MAPK (p42MAPK and p44MAPK). Pretreatment of cells with PTX for 24 h inhibited the activation of MAPK by carbachol, FCS and lysophosphatidic acid, but not that by endothelin-1, phenylephrine or isoprenaline. Involvement of G-proteins in the activation of the cardiac MAPK cascade was demonstrated by the sustained (PTX-insensitive) activation of MAPK (and MEK) after exposure of cells to AlF4-. AlF4- activated PtdIns hydrolysis, as did endothelin-1, endothelin-3, phenylephrine and FCS. In contrast, the effect of lysophosphatidic acid on PtdIns hydrolysis was small and carbachol was without significant effect even after prolonged exposure. We conclude that PTX-sensitive (i.e. Gi/G(o)-linked) and PTX-insensitive (i.e. Gq/Gs-linked) pathways of MAPK activation exist in neonatal ventricular myocytes. FCS may stimulate the MAPK cascade through both pathways.
authors.affiliation: Department of Cardiac Medicine, National Heart and Lung Institute (University of London), U.K.
authors.forename: M A
authors.initials: MA
authors.lastname: Bogoyevitch
authors.forename: A
authors.initials: A
authors.lastname: Clerk
authors.forename: P H
authors.initials: PH
authors.lastname: Sugden
mesh_terms: D017607:Aluminum Compounds / Q000494:pharmacology; D001769:Blood; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000819:agonists / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D002853:Chromatography, Liquid; D004789:Enzyme Activation; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D006352:Heart Ventricles / Q000166:cytology / Q000201:enzymology*; D006868:Hydrolysis; D008563:Membrane Lipids / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D037342:Pertussis Toxin; D010716:Phosphatidylinositols / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000819:agonists / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
chemical_list: D017607:Aluminum Compounds; D008563:Membrane Lipids; D010716:Phosphatidylinositols; D010566:Virulence Factors, Bordetella; D002217:Carbachol; D037342:Pertussis Toxin; D011505:Protein-Tyrosine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019204:GTP-Binding Proteins; D005459:Fluorides; C032311:aluminum fluoride