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

BackgroundActive 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.Methods and FindingsIn 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.ConclusionFor 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.

Bovine Papillomavirus Type 13 Expression in the Urothelial Bladder Tumours of Cattle

“…This is the first report of BPV‐13 infection associated with urothelial tumours of the urinary bladder in cattle. To date, urothelial tumours in veterinary oncology have been associated exclusively with infection of BPV‐1 and BPV‐2, agents known to belong to Deltapapillomavirus genus, species 4 (Campo et al., ; Borzacchiello et al., ; Nasir and Campo, ; Roperto et al., , ,b, ; Lunardi et al., ). Furthermore, this is the first study which shows the presence of BPV‐13 in Europe, thus demonstrating it is a worldwide virus.…”

Molecular and Phylogenetic Analysis of Bovine Papillomavirus Type 1: First Report in Iraqi Cattle

“…Furthermore, reductions in the expression of major histocompatibility complex class I (MHCI) molecules on the cell surface enable the virus to evade immunosurveillance, leading to the inhibition of intracellular transport by means of abnormal connexin expression [ 5 ]. Reference [ 12 ] documented a tricomponent complex composed of E5/PDGF β R/subunit D in vivo. E5 oncoprotein was previously shown to bind to the proteolipidic D component of V1-ATPase proton pump.…”

“…E5 oncoprotein was previously shown to bind to the proteolipidic D component of V1-ATPase proton pump. Reference [ 12 ] suggests that the E5/PDGF β R/subunit D complex may perturb proteostasis, organelle, and cytosol homeostasis, which can result in altered protein degradation and in autophagic responses. Reference [ 13 ] proposed that E2 has a role in the initiation of BPV DNA replication by support E1 binding to the BPV origin via DNA-protein and protein-protein interactions.…”

Pteridium spp. and Bovine Papillomavirus: Partners in Cancer

“…BPV E5 also interferes with cellular homeostasis by hampering the functions of cytosolic organelles, e.g., by interfering with the acidification of the Golgi complex ( 48 ). The E5 protein also forms tri-component complexes with PDGFRβ and the V 1 -ATPase D subunit, which are hypothesized to interfere with cellular proteostasis and autophagy ( 49 ). Furthermore, the BPV E5 protein constitutively activates c-Src ( 50 ) and activates phosphatidylinositol-3-kinase (PI3K) signaling independently of PDGFRβ ( 51 ).…”