title: Esophageal cancer-related gene-4 (ECRG4) interactions with the innate immunity receptor complex.
abstract: OBJECTIVE
  The human c2orf40 gene encodes a tumor suppressor gene called esophageal cancer-related gene-4 (ECRG4) with pro- and anti-inflammatory activities that depend on cell surface processing. Here, we investigated its physical and functional association with the innate immunity receptor complex.
  
  
  METHODS
  Interactions between ECRG4 and the innate immunity receptor complex were assessed by flow cytometry, immunohistochemistry, confocal microscopy, and co-immunoprecipitation. Phage display was used for ligand targeting to cells that overexpress the TLR4-MD2-CD14.
  
  
  RESULTS
  Immunoprecipitation and immunohistochemical studies demonstrate a physical interaction between ECRG4 and TLR4-MD2-CD14 on human granulocytes. Flow cytometry shows ECRG4 on the cell surface of a subset of CD14(+) and CD16(+) leukocytes. In a cohort of trauma patients, the C-terminal 16 amino acid domain of ECRG4 (ECRG4(133-148)) appears to be processed and shed, presumably at a thrombin-like consensus sequence. Phage targeting this putative ligand shows that this peptide sequence internalizes into cells through the TLR4/CD14/MD2 complex, but modulates inflammation through non-canonical, NFκB signal transduction.
  
  
  CONCLUSIONS
  ECRG4 is present on the surface of human monocytes and granulocytes. Its interaction with the human innate immunity receptor complex supports a role for cell surface activation of ECRG4 during inflammation and implicates this receptor in its mechanism of action.
authors.affiliation: Division of Trauma, Surgical Critical Care, Burns, and Acute Care Surgery, Department of Surgery, University of California, San Diego, San Diego, CA, USA.
authors.forename: Sonia
authors.initials: S
authors.lastname: Podvin
authors.forename: Xitong
authors.initials: X
authors.lastname: Dang
authors.forename: Morgan
authors.initials: M
authors.lastname: Meads
authors.forename: Arwa
authors.initials: A
authors.lastname: Kurabi
authors.forename: Todd
authors.initials: T
authors.lastname: Costantini
authors.forename: Brian P
authors.initials: BP
authors.lastname: Eliceiri
authors.forename: Andrew
authors.initials: A
authors.lastname: Baird
authors.forename: Raul
authors.initials: R
authors.lastname: Coimbra
mesh_terms: D000328:Adult; D005260:Female; D006098:Granulocytes / Q000276:immunology*; D057809:HEK293 Cells; D006801:Humans; D007113:Immunity, Innate; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D051218:Lymphocyte Antigen 96 / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000276:immunology*; D009363:Neoplasm Proteins / Q000235:genetics / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000276:immunology; D025521:Tumor Suppressor Proteins; D055815:Young Adult
chemical_list: C476999:ECRG4 protein, human; C495377:LY96 protein, human; D018950:Lipopolysaccharide Receptors; D051218:Lymphocyte Antigen 96; D009363:Neoplasm Proteins; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D025521:Tumor Suppressor Proteins