Involvement of phosphatidylinositol 3-kinase in cAMP- and cGMP-induced duodenal epithelial CFTR activation in mice.
Although phosphatidylinositol 3-kinase (PI3K) is essential for several cellular signal transductions, its role in the regulation of cystic fibrosis transmembrane conductance regulator (CFTR) activity in intestinal epithelial cells is poorly understood. Therefore, the possible involvement of PI3K in the regulation of cAMP- and cGMP-induced duodenal epithelial CFTR activation was investigated in the present study. Forskolin and 8-bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP) markedly stimulated duodenal mucosal HCO(3)(-) secretion and short-circuit current (I(sc)) in CFTR wild-type mice, which was significantly inhibited by CFTR(inh)-172, a highly potent and specific CFTR inhibitor. Forskolin and 8-Br-cGMP failed to stimulate duodenal HCO(3)(-) secretion and I(sc) in CFTR knockout mice. Moreover, forskolin- and 8-Br-cGMP-stimulated duodenal HCO(3)(-) secretion and I(sc) were significantly reduced by wortmannin and LY294002, two selective PI3K inhibitors that are structurally and mechanistically different. Forskolin and 8-Br-cGMP induced CFTR phosphorylation and shifted CFTR proteins to the plasma membrane of duodenal epithelial cells, which were inhibited by wortmannin and LY294002. Forskolin and 8-Br-cGMP not only increased the activity of PI3K but also induced the phosphorylation of Akt, a signaling molecule downstream of PI3K, which were again inhibited by wortmannin and LY294002. Together, our results obtained from functional, biochemical, and morphological studies demonstrate that PI3K pathway plays an important role in the regulation of cAMP- and cGMP-induced duodenal epithelial CFTR channel activity and intracellular trafficking.
Tuo
Biguang
B
Dept. of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Dalian Road 149, Zunyi 563003, China. tuobiguang@yahoo.com.cn
Wen
Guorong
G
Zhang
Yalin
Y
Liu
Xuemei
X
Wang
Xue
X
Liu
Xiaoqiang
X
Dong
Hui
H
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism*; D004386:Duodenum / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D015398:Signal Transduction; D013194:Staining and Labeling; D013997:Time Factors
D001639:Bicarbonates; D002712:Chlorides; D005576:Colforsin; D000242:Cyclic AMP; D006152:Cyclic GMP; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; C016276:8-bromocyclic GMP