HPV16 E5 protein disrupts the c-Cbl-EGFR interaction and EGFR ubiquitination in human foreskin keratinocytes

Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202-5120, USA.
Oncogene (Impact Factor: 8.56). 05/2005; 24(15):2585-8. DOI: 10.1038/sj.onc.1208453
Source: PubMed

ABSTRACT The E5 protein of human papillomavirus type 16 (HPV16) is a small hydrophobic protein, which localizes to the cell membrane, Golgi apparatus and endosomes. HPV16 E5 enhances the activation of the epidermal growth factor (EGFR). The activated EGFR is downregulated through the endocytic pathway, where E5 has been shown to inhibit endosomal acidification and trafficking. Ubiquitination of the activated EGFR plays a role in this downregulation. c-Cbl is a ubiquitin ligase that associates with the activated EGFR and targets it for degradation. Since E5 has been shown to form a complex with the EGFR, we tested the hypothesis that E5 affects the interaction of c-Cbl with the EGFR. We found a significant decrease of c-Cbl bound to the EGFR and of ubiquitinated EGFR in the presence of E5. E5 did not affect c-Cbl steady-state level, phosphorylation or translocation to the membrane. This novel result suggests that HPV16 E5 may, at least in part, upregulate EGFR-mediated signal transduction by inhibiting the interaction of c-Cbl with the EGFR, thereby decreasing c-Cbl-mediated degradation of the EGFR.

  • Source
    • "High-risk HPV E5 binds the 16 kDa component of the vacuolar ATPase, decreases the acidity of endosomes, decreases trafficking through the endocytic pathway and increases ligand-dependent signaling through the EGF receptor (Conrad et al., 1993; Hwang et al., 1995; Straight et al., 1995; Thomsen et al., 2000). While this latter may be due to the decreased degradation of the EGFR in the endosomes or to decreased trafficking through the endosome pathway, it may also be due to E5-mediated disruption of the interaction of c-Cbl, an ubiquitin ligase, with the EGFR (Straight et al., 1995; Thomsen et al., 2000; Zhang et al., 2005a). Alternatively, the increased signaling may be due to E5-mediated upregulation of surface gangliosides (Suprynowicz et al., 2008). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The oncogenic potential of papillomaviruses (PVs) has been appreciated since the 1930s yet the mechanisms of virally-mediated cellular transformation are still being revealed. Reasons for this include: a) the oncoproteins are multifunctional, b) there is an ever-growing list of cellular interacting proteins, c) more than one cellular protein may bind to a given region of the oncoprotein, and d) there is only limited information on the proteins encoded by the corresponding non-oncogenic PVs. The perspective of this review will be to contrast the activities of the viral E6 and E7 proteins encoded by the oncogenic human PVs (termed high-risk HPVs) to those encoded by their non-oncogenic counterparts (termed low-risk HPVs) in an attempt to sort out viral life cycle-related functions from oncogenic functions. The review will emphasize lessons learned from the cell culture studies of the HPVs causing mucosal/genital tract cancers.
    Virology 03/2012; 424(2):77-98. DOI:10.1016/j.virol.2011.12.018 · 3.28 Impact Factor
  • Source
    • "The diverse functions proposed for E5 include protecting the cell against apoptosis (Kabsch and Alonso, 2002; Zhang, Spandau, and Roman, 2002), interfering with cell-cell communication (Oelze et al., 1995), and inhibition of antigen presentation in infected cells (Zhang et al., 2003). The most commonly accepted model is that the E5 gene product potentiates the signaling of the epidermal growth factor receptor (EGFR) by slowing EGFR endocytic trafficking and degradation (Straight, Herman, and McCance, 1995; Straight et al., 1993; Zhang et al., 2005). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Anogenital cancers and head and neck cancers are causally associated with infection by high-risk human papillomavirus (HPV). The mechanism by which high-risk HPVs contribute to oncogenesis is poorly understood. HPV16 encodes three genes (HPV16 E5, E6, and E7) that can transform cells when expressed independently. HPV16 E6 and E7 have well-described roles causing genomic instability and unregulated cell cycle progression. The role of HPV16 E5 in cell transformation remains to be elucidated. Expression of HPV16 E5 results in enlarged, polyploid nuclei that are dependent on the level and duration of HPV16 E5 expression. Live cell imaging data indicate that these changes do not arise from cell-cell fusion or failed cytokinesis. The increase in nuclear size is a continual process that requires DNA synthesis. We conclude that HPV16 E5 produces polyploid cells by endoreplication. These findings provide insight into how HPV16 E5 can contribute to cell transformation.
    Virology 09/2010; 405(2):342-51. DOI:10.1016/j.virol.2010.06.025 · 3.28 Impact Factor
  • Source
    • "The mechanism driving EGFR overexpression in adenosquamous carcinomas remains to be determined. Previous studies have shown that EGFR could be regulated by EGFR gene amplification [28] or by HPV oncoproteins, namely the HPV E5 and E6, which are linked with increased EGFR levels, through inhibition of EGFR internalization and degradation [34,35]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Adenosquamous carcinoma of the uterine cervix is an infrequent but aggressive subtype of cervical cancer. A better understanding of its biological behaviour is warranted to define more accurate prognosis and therapeutic targets. Currently, the blockage of receptor tyrosine kinase (RTKs) activity is an efficient therapeutic strategy for many different cancers. The objective of this study was to investigate EGFR, PDGFRA and VEGFR2 RTKs overexpression and activating gene mutations in a cohort of 30 adenosquamous carcinomas of the uterine cervix. EGFR, PDGFRA and VEGFR2 immunohistochemistry was performed in all samples, followed by DNA isolation from the gross macroscopically dissection of the neoplastic area. Screening for EGFR (exons 18-21) and PDGFRA (exons 12, 14 and 18) mutations was done by PCR--single-strand conformational polymorphism (PCR-SSCP). Despite the presence of EGFR immunohistochemical positive reactions in 43% (13/30) of the samples, no EGFR activating mutations in the hotspot region (exons 18-21) were identified. A silent base substitution (CAG>CAA) in EGFR exon 20 at codon 787 (Q787Q) was found in 17 cases (56%). All PDGFRA immunohistochemical reactions were positive and consistently observed in the stromal component, staining fibroblasts and endothelial cells, as well as in the cytoplasm of malignant cells. No activating PDGFRA mutations were found, yet, several silent mutations were observed, such as a base substitution in exon 12 (CCA>CCG) at codon 567 (P567P) in 9 cases and in exon 18 (GTC>GTT) at codon 824 (V824V) in 4 cases. We also observed the presence of base substitutions in intron 14 (IVS14+3G>A and IVS14+49G>A) in two different cases, and in intron 18 (IVS18-50insA) in 4 cases. VEGFR2 positivity was observed in 22 of 30 cases (73.3%), and was significantly associated with lack of metastasis (p=0.038). This is the most extensive analysis of EGFR, PDGFRA and VEGFR2 in cervical adenosquamous carcinomas. Despite the absence of EGFR and PDGFRA activating mutations, the presence of overexpression of these three important therapeutic targets in a subset of cases may be important in predicting the sensitivity of adenosquamous carcinoma to specific anti-RTKs drugs.
    BMC Cancer 07/2009; 9:212. DOI:10.1186/1471-2407-9-212 · 3.32 Impact Factor
Show more


1 Download
Available from