CaSR stimulates secretion of Wnt5a from colonic myofibroblasts to stimulate CDX2 and sucrase-isomaltase using Ror2 on intestinal epithelia.
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 Ca(2+), screened by RT-PCR Wnt family members, and measured their secretion. Transcripts for Wnt 1, 2, 2b, 3a, 4, and 7a were either absent or unchanged whereas Wnt3 decreased and Wnt5a increased. We assessed Wnt5a secretion by Western blot. High Ca(2+) (5 mM) substantially increased Wnt5a secretion; small interfering RNA (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 microenvironments.
Pacheco
Ivan I
II
Department of Physiology, Queen's University, Ontario, Canada.
Macleod
R John
RJ
D000818:Animals; D000071616:CDX2 Transcription Factor; D018938:Caco-2 Cells; D003106:Colon / Q000166:cytology; D005347:Fibroblasts / Q000502:physiology; D019073:HT29 Cells; D018398:Homeodomain Proteins / Q000502:physiology*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D057050:Receptor Tyrosine Kinase-like Orphan Receptors; D044169:Receptors, Calcium-Sensing / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology*; D013394:Sucrase-Isomaltase Complex / Q000502:physiology*; D015854:Up-Regulation; D051153:Wnt Proteins / Q000378:metabolism*; D000071818:Wnt-5a Protein; D051176:beta Catenin / Q000502:physiology
C095550:CASR protein, human; D000071616:CDX2 Transcription Factor; C491270:CDX2 protein, human; D018398:Homeodomain Proteins; D011518:Proto-Oncogene Proteins; D044169:Receptors, Calcium-Sensing; D011956:Receptors, Cell Surface; C085389:WNT5A protein, human; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; D051176:beta Catenin; C078717:ROR2 protein, human; D057050:Receptor Tyrosine Kinase-like Orphan Receptors; D013394:Sucrase-Isomaltase Complex