JNK mitogen-activated protein kinase limits calcium-dependent chloride secretion across colonic epithelial cells.
Neuroimmune agonists induce epithelial Cl(-) secretion through elevations in intracellular Ca2+ or cAMP. Previously, we demonstrated that epidermal growth factor receptor (EGFR) transactivation and subsequent ERK MAPK activation limits secretory responses to Ca2+-dependent, but not cAMP-dependent, agonists. Although JNK MAPKs are also expressed in epithelial cells, their role in regulating transport function is unknown. Here, we investigated the potential role for JNK in regulating Cl(-) secretion in T(84) colonic epithelial cells. Western blot analysis revealed that a prototypical Ca2+-dependent secretagogue, carbachol (CCh; 100 microM), induced phosphorylation of both the 46-kDa and 54-kDa isoforms of JNK. This effect was mimicked by thapsigargin (TG), which specifically elevates intracellular Ca2+, but not by forskolin (FSK; 10 microM), which elevates cAMP. CCh-induced JNK phosphorylation was attenuated by the EGFR inhibitor, tyrphostin-AG1478 (1 microM). Pretreatment of voltage-clamped T(84) cells with SP600125 (2 microM), a specific JNK inhibitor, potentiated secretory responses to both CCh and TG but not to FSK. The effects of SP600125 on CCh-induced secretion were not additive with those of the ERK inhibitor, PD98059. Finally, in apically permeabilized T(84) cell monolayers, SP600125 potentiated CCh-induced K+ conductances but not Na+/K+ATPase activity. These data demonstrate a novel role for JNK MAPK in regulating Ca2+ but not cAMP-dependent epithelial Cl(-) secretion. JNK activation is mediated by EGFR transactivation and exerts its antisecretory effects through inhibition of basolateral K+ channels. These data further our understanding of mechanisms regulating epithelial secretion and underscore the potential for exploitation of MAPK-dependent signaling in treatment of intestinal transport disorders.
Donnellan
Fergal
F
Dept. of Molecular Medicine, Royal College of Surgeons in Ireland, RCSI Education and Research Ctr., Smurfit Bldg., Beaumont Hospital, Dublin 9, Ireland.
Keating
Niamh
N
Geoghegan
Paul
P
Murray
Frank E
FE
Harvey
Brian J P
BJ
Keely
Stephen J
SJ
D000598:Amino Acids, Cyclic / Q000378:metabolism; D000873:Anthracenes / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D016764:Cell Polarity / Q000502:physiology; D002712:Chlorides / Q000378:metabolism*; D018679:Cholinergic Agonists / Q000494:pharmacology; D003106:Colon / Q000166:cytology / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000201:enzymology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D011799:Quinazolines; D019284:Thapsigargin / Q000494:pharmacology; D020032:Tyrphostins / Q000494:pharmacology
D000598:Amino Acids, Cyclic; D000873:Anthracenes; D002712:Chlorides; D018679:Cholinergic Agonists; D004791:Enzyme Inhibitors; D005419:Flavonoids; D011799:Quinazolines; D020032:Tyrphostins; C101044:RTKI cpd; C432165:pyrazolanthrone; D019284:Thapsigargin; D002217:Carbachol; D048031:JNK Mitogen-Activated Protein Kinases; D011188:Potassium; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D002118:Calcium