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Am J Physiol Gastrointest Liver Physiol (August 14, 2008). doi:10.1152/ajpgi.00560.2007
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Submitted on November 30, 2007
Accepted on July 24, 2008

Extracellular Calcium-Sensing Receptor (CaSR) stimulates secretion of Wnt5a from Colonic Myofibroblasts to stimulate CDX2 and sucrase-isomaltase using Ror2 on intestinal epithelia

Ivan I. Pacheco1 and R John MacLeod2*

1 GIDRU/Dept of Physiology, Queen's University, Kingston, Canada
2 Dept of Physiology/GIDRU, Queen's University, Kingston, Canada

* To whom correspondence should be addressed. E-mail: rjm5{at}post.queensu.ca.

To understand whether Extracellular Calcium-Sensing Receptor (CaSR) expression on colonic myofibroblast cells (18Co) contributed to epithelial homeostasis, we activated the CaSR with 5 mM Ca2+and screened by RT-PCR Wnt family members and measured their secretion. Transcripts for Wnt 1,2,2b,3a,4,7a were either absent or unchanged while Wnt3 decreased and Wnt5a increased. We assessed Wnt5a secretion by Western blot. High Ca2+(5mM) substantially increased Wnt5a secretion; siRNA against the CaSR reduced this to constitutive amounts. Expression of Wnt5a plasmid but not Wnt1 or Wnt3a, increased caudal homeodomain factor CDX2 transcripts and protein in HT-29 adenocarcinoma cells. Wnt5a increased activity of a sucrase-isomaltase (SI) promoter in Caco-2BBE cells. Wnt5a protein stimulation of CDX2 transcripts and protein and SI reporter were increased by overexpression of wild type Ror2, a Wnt5a receptor, and reduced with siRNA against Ror2. CaSR activation of HT-29 cells increased Ror2 protein expression. Ror2 protein was expressed in mouse jejunum from crypt base to villus tip, and in the colon on surface epithelia. Our results show that activation of a G-protein coupled receptor, the CaSR, stimulates secretion of Wnt5a from myofibroblasts. Stimulation of epithelia by the CaSR increased the expression of a receptor for Wnt5a, the tyrosine kinase Ror2, suggesting existence of a unique paracrine relationship for CDX2 homoeostasis in the intestine and revealing new contributions of CaSR-activated myofibroblasts to intestinal stem cell niche micro-environments.







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