Role of cAMP inhibition of p44/p42 mitogen-activated protein kinase in potentiation of protein secretion in rat lacrimal gland.
We previously found that addition of cAMP and a Ca(2+)/PKC-dependent agonist causes synergism or potentiation of protein secretion from rat lacrimal gland acini. In the present study we determined whether cAMP decreases p44/p42 mitogen-activated protein kinase (MAPK) activity in the lacrimal gland. Since we know that activation of MAPK attenuates protein secretion stimulated by Ca(2+)- and PKC-dependent agonists, we also determined whether this activation causes potentiation of secretion. Freshly prepared rat lacrimal gland acinar cells were incubated with dibutyryl cAMP (DBcAMP), carbachol (a cholinergic agonist), phenylephrine (an alpha(1)-adrenergic agonist), or epidermal growth factor (EGF). The latter three agonists are known to activate p44/p42 MAPK. p44/p42 MAPK activity and protein secretion were measured. As measured by Western blot analysis, DBcAMP inhibited both basal and agonist-stimulated p44/p42 MAPK activity. Cellular cAMP levels were increased by 1) using two different cell-permeant cAMP analogs, 2) activating adenylyl cyclase (L-858051), or 3) activation of G(s)-coupled receptors (VIP). The cell-permeant cAMP analogs, L-858051, and VIP inhibited basal p44/p42 MAPK activity by 50, 40, and 40%, respectively. DBcAMP and VIP inhibited carbachol- and EGF-stimulated MAPK activity. cAMP, but not VIP, inhibited phenylephrine-stimulated MAPK activity. Potentiation of secretion was detected when carbachol, phenylephrine, or EGF was simultaneously added with DBcAMP. We conclude that increasing cellular cAMP levels inhibits p44/p42 MAPK activity and that this could account for potentiation of secretion obtained when cAMP was elevated and Ca(2+) and PKC were increased by agonists.
Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA.
Chika
C
Funaki
Robin R
RR
Hodges
Darlene A
DA
Dartt
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D005576:Colforsin / Q000031:analogs & derivatives / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D003563:Cyclic CMP / Q000031:analogs & derivatives / Q000378:metabolism; D004224:Diterpenes; D004305:Dose-Response Relationship, Drug; D020536:Enzyme Activators / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000378:metabolism; D066298:In Vitro Techniques; D007765:Lacrimal Apparatus / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
D000316:Adrenergic alpha-Agonists; D018679:Cholinergic Agonists; D004224:Diterpenes; D020536:Enzyme Activators; D010726:Phosphodiesterase Inhibitors; C055627:L 858051; D005576:Colforsin; D010656:Phenylephrine; D003563:Cyclic CMP; D014660:Vasoactive Intestinal Peptide; D004815:Epidermal Growth Factor; C053441:dibutyryl cyclic-3',5'-cytidine monophosphate; D002217:Carbachol; D000242:Cyclic AMP; D010544:Peroxidases; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010727:Phosphoric Diester Hydrolases; D000262:Adenylyl Cyclases; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine