title: Identification of protein tyrosine phosphatase receptor gamma extracellular domain (sPTPRG) as a natural soluble protein in plasma.
abstract: BACKGROUND
  PTPRG is a widely expressed protein tyrosine phosphatase present in various isoforms. Peptides from its extracellular domain have been detected in plasma by proteomic techniques. We aim at characterizing the plasmatic PTPRG (sPTPRG) form and to identify its source.
  
  
  RESULTS
  The expression of sPTPRG was evaluated in human plasma and murine plasma and tissues by immunoprecipitation and Western blotting. The polypeptides identified have an apparent Mr of about 120 kDa (major band) and 90 kDa (minor band) respectively. Full length PTPRG was identified in the 100.000×g pelleted plasma fraction, suggesting that it was present associated to cell-derived vesicles (exosomes). The release of sPTPRG by HepG2 human hepatocellular carcinoma cell line was induced by ethanol and sensitive to metalloproteinase and not to Furin inhibitors. Finally, increased levels of the plasmatic ∼120 kDa isoform were associated with the occurrence of liver damage.
  
  
  CONCLUSIONS
  These results demonstrate that sPTPRG represent a novel candidate protein biomarker in plasma whose increased expression is associated to hepatocyte damage. This observation could open a new avenue of investigation in this challenging field.
authors.affiliation: Department of Pathology and Diagnostics, University of Verona, Verona, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Moratti
authors.affiliation: Department of Pathology and Diagnostics, University of Verona, Verona, Italy.
authors.forename: Marzia
authors.initials: M
authors.lastname: Vezzalini
authors.affiliation: Department of Pathology and Diagnostics, University of Verona, Verona, Italy.
authors.forename: Luisa
authors.initials: L
authors.lastname: Tomasello
authors.affiliation: Clinical Chemistry and Hematology Laboratory St. Bortolo Hospital, Vicenza, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Giavarina
authors.affiliation: Department of Pathology and Diagnostics, University of Verona, Verona, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Sorio
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000097:blood; D000431:Ethanol / Q000494:pharmacology; D055354:Exosomes / Q000378:metabolism; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D008297:Male; D051379:Mice; D020033:Protein Isoforms / Q000097:blood; D020543:Proteome; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5 / Q000097:blood* / Q000737:chemistry*
chemical_list: D015415:Biomarkers; D020033:Protein Isoforms; D020543:Proteome; D000431:Ethanol; C516850:PTPRG protein, human; C516851:Ptprg protein, mouse; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5