title: p38MAPK inhibition enhances basal and norepinephrine-stimulated p42/44MAPK phosphorylation in rat pinealocytes.
abstract: Interaction between p38MAPK and p42/44MAPK in rat pinealocytes was examined by determining the effects of p38MAPK inhibitors on the phosphorylation of p42/44MAPK using Western blot analysis. Treatment with SB202190, a specific inhibitor of p38MAPK, increased p42/44MAPK phosphorylation in a concentration-dependent manner. SB202190 also enhanced the magnitude and the duration of norepinephrine-activated p42/44MAPK phosphorylation. The effect of SB202190 on p42/44MAPK phosphorylation was abolished by PD98059 or UO126, inhibitors of MEK, suggesting that SB202190 is acting upstream of MEK in activating p42/44MAPK. The SB202190-induced phosphorylation of p42/44MAPK was not blocked by inhibitors of cGMP-dependent kinase (KT5823), protein kinase C (calphostin C) or Ca2+/calmodulin dependent kinase (KN93) suggesting that these pathways may not be involved in the effect of SB202190. SB202190 further increased p42/44MAPK phosphorylation that was stimulated by 8-bromo-cGMP, 4beta phorbol 12-myristate 13-acetate, or ionomycin. In contrast, inhibition of p42/44MAPK phosphorylation by dibutyryl-cAMP persisted when p42/44MAPK phosphorylation was increased by SB202190. Furthermore, inhibition of p42/44MAPK phosphorylation had no effect on p38MAPK activation. These results suggest that inhibition of p38MAPK causes activation of p42/44MAPK and acts synergistically with norepinephrine in the regulation of p42/44MAPK activation in rat pinealocytes.
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Alberta, Edmonton, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Mackova
authors.forename: J R
authors.initials: JR
authors.lastname: Man
authors.forename: C L
authors.initials: CL
authors.lastname: Chik
authors.forename: A K
authors.initials: AK
authors.lastname: Ho
mesh_terms: D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015870:Gene Expression; D006873:Hydroquinones / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008387:Marine Toxins; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics; D009638:Norepinephrine / Q000494:pharmacology*; D010080:Oxazoles / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D010870:Pineal Gland / Q000201:enzymology*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D004791:Enzyme Inhibitors; D006873:Hydroquinones; D007093:Imidazoles; D008387:Marine Toxins; D010080:Oxazoles; D011725:Pyridines; C084037:dephostatin; C059041:calyculin A; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; D009638:Norepinephrine