Activation of Extracellular-Signal Regulated Kinase by Epidermal Growth Factor Is Potentiated by cAMP-Elevating Agents in Primary Cultures of Adult Rat Hepatocytes

作者：Moteki Hajime; Kimura Mitsutoshi^*; Ogihara Masahiko

来源：Biological & Pharmaceutical Bulletin, 2011, 34(10): 1542-1552.

• epidermal growth factor
• extracellular-signal regulated kinase
• hepatocyte
• alpha(2)-adrenergic agonist
• beta(2)-adrenergic agonist
• cross-talk

We investigated the effects of alpha- and beta-adrenergic agonists on epidermal growth factor (EGF)-stimulated extracellular-signal regulated kinase (ERK) isoforms in primary cultures of adult rat hepatocytes. Hepatocytes were isolated and cultured with EGF (20 ng/ml) and/or alpha(1)-, alpha(2)- and beta(2)-adrenergic agonists. Phosphorylated ERK isoforms (ERK1; p44 mitogen-activated protein kinase (MAPK) and ERK2; p42 MAPK) were detected by Western blotting analysis using anti-phospho-ERK1/2 antibody. The results show that EGF induced a 2.5-fold increase in ERK2-, but not ERK1-, phosphorylation within 3 min. This EGF-induced ERK2 activation was abolished by treatment with the EGF-receptor kinase inhibitor AG1478 (10(-7)m) or the MEK (MAPK kinase) inhibitor PD98059 (10(-6) m). The alpha(2)-adrenergic and beta(2)-adrenergic agonists, UK14304 (10(-6)m) and metaproterenol (10(-6)M), respectively, had no effect in the absence of EGF, but metaproterenol significantly potentiated EGF-induced ERK2 phosphorylation. Moreover, the cell-permeable cAMP analog 8-bromo cAMP (10(-7) m), also potentiated EGF-induced ERK2 phosphorylation. The effects of these analogs were antagonized by the protein kinase A (PKA) inhibitor H-89 (10(-7) m). These results suggest that direct or indirect activation of PKA represents a positive regulatory mechanism for EGF stimulation of ERK2 induction.

• 出版日期2011-10