title: Positive and negative regulation of JNK1 by protein kinase C and p42(MAP kinase) in adult rat hepatocytes.
abstract: The role of protein kinase C (PKC) and p42(MAP kinase) signaling in the regulation of proliferation and apoptosis was investigated in freshly isolated and primary cultured rat hepatocytes. Acute treatment of freshly isolated hepatocytes with phenylephrine and EGF caused rapid phasic activations of p42(MAP kinase) and JNK1. Acute pre-treatment of hepatocytes with the PKC inhibitors sphingosine, chelerythrine and bis-indolylmaleimide abolished the ability of phenylephrine, but not EGF, to activate p42(MAP kinase) and JNK1. Acute pretreatments with all of the PKC inhibitors alone increased JNK1 basal activity approximately 2-fold. Acute treatments of primary cultures of hepatocytes with an inhibitor of MEK1 activation (PD98059) also caused inhibition of p42(MAP kinase) and a approximately 2-fold activation of JNK1. These data demonstrate that PKC can function as both a proximal activator and a distal inhibitor of signaling through the JNK1/SAP kinase pathway. Treatments (4 h) of primary cultured hepatocytes with sphingosine, chelerythrine, bis-indolylmaleimide and PD98059 did not induce apoptosis as judged by propidium iodide staining. Similar acute treatments of HepG2 cells rapidly induced cell death. These data demonstrate that acute inhibition of either PKC or p42(MAP kinase) function is sufficient to rapidly induce apoptosis in transformed, but not in non-transformed hepatocytes.
authors.affiliation: Department of Medicine, Medical College of Virginia, Richmond 23298-0058, USA.
authors.forename: W D
authors.initials: WD
authors.lastname: Jarvis
authors.forename: K L
authors.initials: KL
authors.lastname: Auer
authors.forename: M
authors.initials: M
authors.lastname: Spector
authors.forename: G
authors.initials: G
authors.lastname: Kunos
authors.forename: S
authors.initials: S
authors.lastname: Grant
authors.forename: P
authors.initials: P
authors.lastname: Hylemon
authors.forename: R
authors.initials: R
authors.lastname: Mikkelsen
authors.forename: P
authors.initials: P
authors.lastname: Dent
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D048369:MAP Kinase Kinase 1; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D010656:Phenylephrine / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004791:Enzyme Inhibitors; D010656:Phenylephrine; D004815:Epidermal Growth Factor; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases