p38 mitogen-activated protein kinase inhibits calcium-dependent chloride secretion in T84 colonic epithelial cells.
We have previously shown that Ca(2+)-dependent Cl(-) secretion across intestinal epithelial cells is limited by a signaling pathway involving transactivation of the epidermal growth factor receptor (EGFR) and activation of ERK mitogen-activated protein kinase (MAPK). Here, we have investigated a possible role for p38 MAPK in regulation of Ca(2+)-dependent Cl(-) secretion. Western blot analysis of T(84) colonic epithelial cells revealed that the muscarinic agonist carbachol (CCh; 100 microM) stimulated phosphorylation and activation of p38 MAPK. The p38 inhibitor SB-203580 (10 microM) potentiated and prolonged short-circuit current (I(sc)) responses to CCh across voltage-clamped T(84) cells to 157.4 +/- 6.9% of those in control cells (n = 21; P < 0.001). CCh-induced p38 phosphorylation was attenuated by the EGFR inhibitor tyrphostin AG-1478 (0.1 nM-10 microM) and by the Src family kinase inhibitor PP2 (20 nM-2 microM). The effects of CCh on p38 phosphorylation were mimicked by thapsigargin (TG; 2 microM), which specifically elevates intracellular Ca(2+), and were abolished by the Ca(2+) chelator BAPTA-AM (20 microM), implying a role for intracellular Ca(2+) in mediating p38 activation. SB-203580 (10 microM) potentiated I(sc) responses to TG to 172.4 +/- 18.1% of those in control cells (n = 18; P < 0.001). When cells were pretreated with SB-203580 and PD-98059 to simultaneously inhibit p38 and ERK MAPKs, respectively, I(sc) responses to TG and CCh were significantly greater than those observed with either inhibitor alone. We conclude that Ca(2+)-dependent agonists stimulate p38 MAPK in T(84) cells by a mechanism involving intracellular Ca(2+), Src family kinases, and the EGFR. CCh-stimulated p38 activation constitutes a similar, but distinct and complementary, antisecretory signaling pathway to that of ERK MAPK.
Keely
Stephen J
SJ
Department of Medicine, University of California, San Diego, California 92103, USA. skeely@ucsd.edu
Barrett
Kim E
KE
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D066246:ErbB Receptors / Q000819:agonists / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018721:Muscarinic Agonists / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D002712:Chlorides; D004791:Enzyme Inhibitors; D018721:Muscarinic Agonists; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic; D066246:ErbB Receptors; D019061:src-Family Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium