title: cAMP activates TRPC6 channels via the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB)-mitogen-activated protein kinase kinase (MEK)-ERK1/2 signaling pathway.
abstract: cAMP is an important second messenger that executes diverse physiological function in living cells. In this study, we investigated the effect of cAMP on canonical TRPC6 (transient receptor potential channel 6) channels in TRPC6-expressing HEK293 cells and glomerular mesangial cells. The results showed that 500 μm 8-Br-cAMP, a cell-permeable analog of cAMP, elicited [Ca(2+)](i) increases and stimulated a cation current at the whole-cell level in TRPC6-expressing HEK293 cells. The effect of cAMP diminished in the presence of the PI3K inhibitors wortmannin and LY294002 or the MEK inhibitors PD98059, U0126, and MEK inhibitor I. 8-Br-cAMP also induced phosphorylation of MEK and ERK1/2. Conversion of serine to glycine at an ERK1/2 phosphorylation site (S281G) abolished the cAMP activation of TRPC6 as determined by whole-cell and cell-attached single-channel patch recordings. Experiments based on a panel of pharmacological inhibitors or activators suggested that the cAMP action on TRPC6 was not mediated by PKA, PKG, or EPAC (exchange protein activated by cAMP). Total internal fluorescence reflection microscopy showed that 8-Br-cAMP did not alter the trafficking of TRPC6 to the plasma membrane. We also found that, in glomerular mesangial cells, glucagon-induced [Ca(2+)](i) increases were mediated through the cAMP-PI3K-PKB-MEK-ERK1/2-TRPC6 signaling pathway. In summary, this study uncovered a novel TRPC6 activation mechanism in which cAMP activates TRPC6 via the PI3K-PKB-MEK-ERK1/2 signaling pathway.
authors.affiliation: Li Ka Shing Institute of Health Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Shen
authors.forename: Hiu-Yee
authors.initials: HY
authors.lastname: Kwan
authors.forename: Xin
authors.initials: X
authors.lastname: Ma
authors.forename: Ching-On
authors.initials: CO
authors.lastname: Wong
authors.forename: Juan
authors.initials: J
authors.lastname: Du
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Yao
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005934:Glucagon / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D008297:Male; D050527:Mesangial Cells / Q000166:cytology / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*; D000074287:TRPC6 Cation Channel
chemical_list: D002118:Calcium; D000242:Cyclic AMP; D004791:Enzyme Inhibitors; D005934:Glucagon; D020930:MAP Kinase Kinase Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; C492145:Trpc6 protein, rat; C535150:MAPK1 protein, human