Alpha 1-adrenergic and cholinergic agonists activate MAPK by separate mechanisms to inhibit secretion in lacrimal gland.
The purpose of this study was to determine the role of p42/p44 mitogen-activated protein kinase (MAPK) in alpha(1)-adrenergically and cholinergically stimulated protein secretion in rat lacrimal gland acinar cells and the pathways used by these agonists to activate MAPK. Acini were isolated by collagenase digestion and incubated with the alpha(1)-adrenergic agonist phenylephrine or the cholinergic agonist carbachol, and activation of MAPK and protein secretion were then measured. Phenylephrine and carbachol activated MAPK in a time- and concentration-dependent manner. Inhibition of MAPK significantly increased phenylephrine- and carbachol-induced protein secretion. Inhibition of EGF receptor (EGFR) with AG1478, an inhibitor of the EGFR tyrosine kinase activity, significantly increased phenylephrine- but not carbachol-induced protein secretion. Whereas phenylephrine-induced activation of MAPK was completely inhibited by AG1478, activation of MAPK by carbachol was not. Phenylephrine stimulated tyrosine phosphorylation of the EGFR, whereas carbachol stimulated p60(Src), and possibly Pyk2, to activate MAPK. We conclude that, in the lacrimal gland, activation of MAPK plays an inhibitory role in alpha(1)-adrenergically and cholinergically stimulated protein secretion and that these agonists use different signaling mechanisms to activate MAPK.
Ota
Isao
I
Schepens Eye Research Institute, Harvard Medical School, 20 Staniford Street, Boston, MA 02114, USA.
Zoukhri
Driss
D
Hodges
Robin R
RR
Rios
José D
JD
Tepavcevic
Vanja
V
Raddassi
Isabelle
I
Chen
Li Li
LL
Dartt
Darlene A
DA
D058646:Adrenergic alpha-1 Receptor Agonists; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D018679:Cholinergic Agonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; 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; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D058646:Adrenergic alpha-1 Receptor Agonists; D000316:Adrenergic alpha-Agonists; D018679:Cholinergic Agonists; D004791:Enzyme Inhibitors; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases