title: Regulation of 90-kilodalton ribosomal S6 kinase phosphorylation in the rat pineal gland.
abstract: In this study we investigated diurnal changes in the activation state of the 90-kDa ribosomal S6 kinase (p90RSK) in the rat pineal gland. In animals housed under a lighting regimen with 12 h of light, we found an increase in phosphorylated p90RSK during the dark phase, and this increase was abolished by treatment with propranolol or continuous exposure to light. To determine the intracellular mechanism involved, rat pinealocytes were treated with norepinephrine. Norepinephrine caused a parallel increase in phosphorylated p42/44 MAPK (p42/44(MAPK)) and p90RSK that was reduced by prazosin or propranolol, indicating involvement of both alpha(1)- and beta-adrenergic receptors. Treatment with dibutyryl cGMP, 4beta-phorbol 12-myristate 13-acetate, or ionomycin mimicked norepinephrine-stimulated p90RSK phosphorylation, whereas dibutyryl cAMP caused a decrease in p90RSK phosphorylation. Inhibition of p42/44(MAPK) activation by UO126 was effective in reducing norepinephrine-stimulated p90RSK phosphorylation. Moreover, UO126 had an inhibitory effect on norepinephrine-stimulated arylalkyl-N-acetyltransferase activity. These results indicate that the adrenergically regulated nocturnal increase in p90RSK phosphorylation is mainly mediated through a cGMP-->p42/44(MAPK)-dependent mechanism.
authors.affiliation: Departments of Physiology and Medicine, Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada T6G 2H7. anho@ualberta.ca
authors.forename: A K
authors.initials: AK
authors.lastname: Ho
authors.forename: M
authors.initials: M
authors.lastname: Mackova
authors.forename: C
authors.initials: C
authors.lastname: Cho
authors.forename: C L
authors.initials: CL
authors.lastname: Chik
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism; D002940:Circadian Rhythm; D006152:Cyclic GMP / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006706:Homeostasis; D008027:Light; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D010766:Phosphorylation; D010870:Pineal Gland / Q000187:drug effects / Q000201:enzymology* / Q000528:radiation effects; D011433:Propranolol / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000502:physiology; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000032:analysis / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D004791:Enzyme Inhibitors; D018340:Receptors, Adrenergic, alpha-1; D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D001191:Arylamine N-Acetyltransferase; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020929:Mitogen-Activated Protein Kinase Kinases; D006152:Cyclic GMP; D009638:Norepinephrine