title: Epithelial calcium-sensing receptor activation by eosinophil granule protein analog stimulates collagen matrix contraction.
abstract: BACKGROUND
  Eosinophils reside in normal gastrointestinal tracts and increase during disease states. Receptors for eosinophil-derived granule proteins (EDGPs) have not been identified, but highly cationic molecules, similar to eosinophil proteins, bind extracellular calcium-sensing receptors (CaSRs). We hypothesized that stimulation of CaSRs by eosinophil proteins activates epithelial cells.
  
  
  METHODS
  Caco2 intestinal epithelial cells, AML14.3D10 eosinophils, wild-type (WT) human embryonic kidney 293 (HEK293) cells not expressing CaSRs (HEK-WT), and CaSR-transfected HEK293 cells (HEK-CaSR) were stimulated with an eosinophil protein analog poly-L-arginine (PA) and phosphorylated extracellular signal-regulated kinase (pERK)1 and pERK2 were measured. Functional activation was measured with collagen lattice contraction assays.
  
  
  RESULTS
  Coculture of Caco2 cells with AML14.3D10 eosinophils augmented lattice contraction as compared with lattices containing Caco2 cells alone. PA stimulation of Caco2 lattices augmented contraction. HEK-CaSR stimulation with PA or Ca(2+) resulted in greater pERK activation than that of stimulated HEK-WT cells. PA stimulated greater HEK-CaSR lattice contraction than unstimulated lattices. Contraction of PA-stimulated and PA-unstimulated HEK-WT lattices did not differ.
  
  
  CONCLUSIONS
  Exposure of intestinal epithelia to the EDGP analog PA stimulates CaSR-dependent ERK phosphorylation and epithelial-mediated collagen lattice contraction. We speculate that EDGP release within the epithelial layers activates the CaSR receptor, leading to matrix contraction and tissue fibrosis.
authors.affiliation: Department of Pediatrics, Pediatric Gastroenterology, Floating Hospital for Children at Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts, USA.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Ngo
authors.forename: R John
authors.initials: RJ
authors.lastname: MacLeod
authors.forename: Vince
authors.initials: V
authors.lastname: Mukkada
authors.forename: Razan
authors.initials: R
authors.lastname: Turki
authors.forename: Glenn T
authors.initials: GT
authors.lastname: Furuta
mesh_terms: D018938:Caco-2 Cells; D002118:Calcium / Q000378:metabolism; D003094:Collagen / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D047091:Eosinophil Granule Proteins / Q000494:pharmacology*; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005355:Fibrosis; D057809:HEK293 Cells; D019073:HT29 Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology*; D010766:Phosphorylation; D044169:Receptors, Calcium-Sensing / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: C095550:CASR protein, human; D047091:Eosinophil Granule Proteins; D010455:Peptides; D044169:Receptors, Calcium-Sensing; C015462:polyarginine; D003094:Collagen; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium