Submitted on May 19, 2006
Accepted on October 16, 2007
The Extracellular Calcium-Sensing Receptor (CaSR) on Human Esophagus and Evidence of Expression of the CaSR on the Esophageal Epithelial Cell Line (HET-1A)
Christopher J. Justinich1, Nanette Mak1, Ivan Pacheco2, Dan Mulder3, Ron W. Wells1, Michael G. Blennerhassett4, and R John MacLeod5*
1 Gastrointestinal Diseases Research Unit, Dept of Paediatrics, Queen's Univeristy, Kingston, Canada
2 Dept of Physiology, Queen's University, Kingston, Canada
3 Pediatric Gastroenterology, Queen's University, Kingston, Canada
4 Dept of Physiology/GIDRU, Queen's University, Kingston , Canada
5 Dept of Physiology/GIDRU, Queen's University, Kingston, Canada; Dept of Physiology, Queen's University, Kingston, Canada
* To whom correspondence should be addressed. E-mail: rjm5{at}post.queensu.ca.
Gastrointestinal reflux disease and eosinophilic esophagitis are characterized by basal cell hyperplasia. The extracellular calcium-sensing receptor (CaSR), a G-protein coupled receptor which may be activated by divalent agonists, is expressed throughout the gastrointestinal system. The CaSR may regulate proliferation or differentiation depending on cell type and tissue. The current experiments demonstrate the expression of the CaSR on a human esophageal epithelial cell line (HET-1A) and the location and expression of the CaSR in the human esophagus. CaSR immunoreactivity was seen in the basal layer of normal human esophagus. CaSR expression was confirmed in HET-1A cells by RT-PCR, immunocytochemistry and Western blotting. CaSR stimulation by extracellular calcium or agonists such as spermine or Mg2+, caused ERK 1&2 activation, [Ca2+]i mobilization (as assessed by microspecfluorometry using Fluo-4) and secretion of the multifunctional cytokine IL-8 (CX-CL8). HET-1A cells transiently transfected with siRNA duplex against the CaSR manifested attenuated responses to Ca2+-stimulation of pERK1&2, [Ca2+]i mobilization, and IL-8 secretion, while responses to acetylcholine remained sustained. An inhibitor of PI-PLC (U73122) blocked CaSR-stimulated [Ca2+]i release. We conclude that the CaSR is present on basal cells of the human esophagus and is present in a functional manner on the esophageal epithelial cell line, HET-1A.
