Identification and characterization of multiple corticotropin-releasing factor type 2 receptor isoforms in the rat esophagus.
The rat esophagus shares some cellular features with skin squamous epithelium and striated muscle that express high levels of corticotropin-releasing factor type 2 (CRF2) receptors or their cognate ligand urocortin (Ucn) 1, 2, and 3. We investigated the expression and cell signaling of CRF2 receptors and ligands in the rat esophagus and lower esophageal sphincter (LES) by RT-PCR and quantitative PCR in normal and corticosterone-treated whole esophageal tissue, laser capture microdissected layers, and isolated esophageal cells. The expression of CRF2 receptor protein and intracellular cAMP and ERK1/2 responses to CRF agonists and CRF2 antagonist were determined in cultured esophageal cells and HEK-293 cells transfected with CRF2b receptors. CRF2 was abundantly expressed in the mucosa and longitudinal muscle layers of the esophagus and LES, whereas CRF1 expression was scarce. CRF2b wild-type transcript was predominantly expressed in the esophagus, and in addition, several new CRF2 splice variants including six CRF2a isoforms were identified. Expression of Ucn 1, Ucn 2, and to a smaller extent Ucn 3, but not CRF mRNA, was detected in the esophagus and LES. Ucn 1 and Ucn 2 stimulated dose-dependent cAMP production and ERK1/2 phosphorylation in the esophageal cells, whereas CRF and CRF1 agonist, cortagine, had less potent effects. In addition, Ucn 2-stimulated cAMP and ERK responses were blocked by the CRF2 antagonist, astressin2-B. These data established the presence of a prominent CRF2 signaling system in the esophagus and LES-encompassing multiple CRF2 receptor variants and Ucn, suggesting a functional role in secretomotor activity and epithelial and muscle cell proliferation.
Wu
S Vincent
SV
Center for Ulcer Research and Education, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles 90073, USA, and Division of Gastroenterology, Taipei Veterans General Hospital, Taiwan. vwu@ucla.edu
Yuan
Pu-qing
PQ
Wang
Lixin
L
Peng
Yen L
YL
Chen
Chih-Yen
CY
Taché
Yvette
Y
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003345:Corticosterone / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004947:Esophagus / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018019:Receptors, Corticotropin-Releasing Hormone / Q000235:genetics* / Q000378:metabolism*; D054832:Urocortins
C101531:CRF receptor type 2; D020033:Protein Isoforms; D018019:Receptors, Corticotropin-Releasing Hormone; D054832:Urocortins; D003346:Corticotropin-Releasing Hormone; D000242:Cyclic AMP; D020929:Mitogen-Activated Protein Kinase Kinases; D003345:Corticosterone