title: Bovine papillomavirus type 2 (BPV-2) E5 oncoprotein binds to the subunit D of the V₁-ATPase proton pump in naturally occurring urothelial tumors of the urinary bladder of cattle.
abstract: BACKGROUND
  Active infection by bovine papillomavirus type 2 (BPV-2) was documented for fifteen urinary bladder tumors in cattle. Two were diagnosed as papillary urothelial neoplasm of low malignant potential (PUNLMP), nine as papillary and four as invasive urothelial cancers.
  
  
  RESULTS
  In all cancer samples, PCR analysis revealed a BPV-2-specific 503 bp DNA fragment. E5 protein, the major oncoprotein of the virus, was shown both by immunoprecipitation and immunohistochemical analysis. E5 was found to bind to the activated (phosphorylated) form of the platelet derived growth factor β receptor. PDGFβR immunoprecipitation from bladder tumor samples and from normal bladder tissue used as control revealed a protein band which was present in the pull-down from bladder cancer samples only. The protein was identified with mass spectrometry as "V₁-ATPase subunit D", a component of the central stalk of the V₁-ATPase vacuolar pump. The subunit D was confirmed in this complex by coimmunoprecipitation investigations and it was found to colocalize with the receptor. The subunit D was also shown to be overexpressed by Western blot, RT-PCR and immunofluorescence analyses. Immunoprecipitation and immunofluorescence also revealed that E5 oncoprotein was bound to the subunit D.
  
  
  CONCLUSIONS
  For the first time, a tri-component complex composed of E5/PDGFβR/subunit D has been documented in vivo. Previous in vitro studies have shown that the BPV-2 E5 oncoprotein binds to the proteolipid c ring of the V₀-ATPase sector. We suggest that the E5/PDGFβR/subunit D complex may perturb proteostasis, organelle and cytosol homeostasis, which can result in altered protein degradation and in autophagic responses.
authors.affiliation: Dipartimento di Medicina Veterinaria e Produzioni Animali, Settore Malattie Infettive, Università di Napoli Federico II, Napoli, Italia.
authors.forename: Sante
authors.initials: S
authors.lastname: Roperto
authors.affiliation: Dipartimento di Medicina Veterinaria e Produzioni Animali, Settore Patologia Generale, Università di Napoli Federico II, Napoli, Italia.
authors.forename: Valeria
authors.initials: V
authors.lastname: Russo
authors.affiliation: Dipartimento di Medicina Veterinaria e Produzioni Animali, Settore Patologia Generale, Università di Napoli Federico II, Napoli, Italia.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Borzacchiello
authors.affiliation: Dipartimento di Medicina Veterinaria e Produzioni Animali, Settore Patologia Generale, Università di Napoli Federico II, Napoli, Italia.
authors.forename: Chiara
authors.initials: C
authors.lastname: Urraro
authors.affiliation: Dipartimento di Medicina Veterinaria e Produzioni Animali, Settore Patologia Generale, Università di Napoli Federico II, Napoli, Italia.
authors.forename: Roberta
authors.initials: R
authors.lastname: Lucà
authors.affiliation: Dipartimento di Medicina Veterinaria e Produzioni Animali, Settore Patologia Generale, Università di Napoli Federico II, Napoli, Italia.
authors.forename: Iolanda
authors.initials: I
authors.lastname: Esposito
authors.affiliation: Dipartimento di Medicina Veterinaria e Produzioni Animali, Settore Patologia Generale, Università di Napoli Federico II, Napoli, Italia.
authors.forename: Marita Georgia
authors.initials: MG
authors.lastname: Riccardi
authors.affiliation: Dipartimento di Medicina Veterinaria e Produzioni Animali, Settore Patologia Generale, Università di Napoli Federico II, Napoli, Italia.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Raso
authors.affiliation: Dipartimento di Medicina Clinica e Sperimentale, Università di Catanzaro "Magna Graecia", Catanzaro, Italia.
authors.forename: Marco
authors.initials: M
authors.lastname: Gaspari
authors.affiliation: Dipartimento di Medicina Veterinaria e Produzioni Animali, Settore Patologia Generale, Università di Napoli Federico II, Napoli, Italia.
authors.forename: Dora Maria
authors.initials: DM
authors.lastname: Ceccarelli
authors.affiliation: Unit of clinical epidemiology, biostatistic and cancer registry, IRCCS CROB, Rionero in Vulture (Potenza), Italia.
authors.forename: Rocco
authors.initials: R
authors.lastname: Galasso
authors.affiliation: Dipartimento di Biologia, Università di Napoli Federico II, Napoli, Italia.
authors.forename: Franco
authors.initials: F
authors.lastname: Roperto
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D052688:Bovine papillomavirus 1 / Q000378:metabolism*; D002417:Cattle; D002418:Cattle Diseases / Q000378:metabolism; D015513:Oncogene Proteins / Q000378:metabolism*; D030361:Papillomavirus Infections / Q000378:metabolism; D017494:Proton Pumps / Q000378:metabolism*; D001743:Urinary Bladder / Q000378:metabolism; D001749:Urinary Bladder Neoplasms / Q000378:metabolism*; D014571:Urologic Neoplasms / Q000378:metabolism*; D019459:Urothelium / Q000378:metabolism*
chemical_list: D015513:Oncogene Proteins; D017494:Proton Pumps; D000251:Adenosine Triphosphatases