E6 proteins from high-risk HPV, low-risk HPV, and animal papillomaviruses activate the Wnt/β-catenin pathway through E6AP-dependent degradation of NHERF1

PLoS Pathog. 2019 Apr 19;15(4):e1007575. doi: 10.1371/journal.ppat.1007575. eCollection 2019 Apr.

Abstract

High-risk human papillomavirus (HPV) E6 proteins associate with the cellular ubiquitin ligase E6-Associated Protein (E6AP), and then recruit both p53 and certain cellular PDZ proteins for ubiquitination and degradation by the proteasome. Low-risk HPV E6 proteins also associate with E6AP, yet fail to recruit p53 or PDZ proteins; their E6AP-dependent targets have so far been uncharacterized. We found a cellular PDZ protein called Na+/H+ Exchanger Regulatory Factor 1 (NHERF1) is targeted for degradation by both high and low-risk HPV E6 proteins as well as E6 proteins from diverse non-primate mammalian species. NHERF1 was degraded by E6 in a manner dependent upon E6AP ubiquitin ligase activity but independent of PDZ interactions. A novel structural domain of E6, independent of the p53 recognition domain, was necessary to associate with and degrade NHERF1, and the NHERF1 EB domain was required for E6-mediated degradation. Degradation of NHERF1 by E6 activated canonical Wnt/β-catenin signaling, a key pathway that regulates cell growth and proliferation. Expression levels of NHERF1 increased with increasing cell confluency. This is the first study in which a cellular protein has been identified that is targeted for degradation by both high and low-risk HPV E6 as well as E6 proteins from diverse animal papillomaviruses. This suggests that NHERF1 plays a role in regulating squamous epithelial growth and further suggests that the interaction of E6 proteins with NHERF1 could be a common therapeutic target for multiple papillomavirus types.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Female
  • Humans
  • Oncogene Proteins, Viral / genetics
  • Oncogene Proteins, Viral / metabolism*
  • Papillomaviridae / isolation & purification
  • Papillomavirus Infections / genetics
  • Papillomavirus Infections / metabolism*
  • Papillomavirus Infections / virology
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism*
  • Phylogeny
  • Proteasome Endopeptidase Complex
  • Proteolysis
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Sodium-Hydrogen Exchangers / genetics
  • Sodium-Hydrogen Exchangers / metabolism*
  • Tumor Cells, Cultured
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • Uterine Cervical Neoplasms / genetics
  • Uterine Cervical Neoplasms / metabolism
  • Uterine Cervical Neoplasms / virology
  • Wnt1 Protein / genetics
  • Wnt1 Protein / metabolism*
  • beta Catenin / genetics
  • beta Catenin / metabolism*

Substances

  • CTNNB1 protein, human
  • DNA-Binding Proteins
  • E6 protein, Human papillomavirus type 16
  • E6 protein, Human papillomavirus type 18
  • Oncogene Proteins, Viral
  • Phosphoproteins
  • Repressor Proteins
  • Sodium-Hydrogen Exchangers
  • WNT1 protein, human
  • Wnt1 Protein
  • beta Catenin
  • sodium-hydrogen exchanger regulatory factor
  • UBE3A protein, human
  • Ubiquitin-Protein Ligases
  • Proteasome Endopeptidase Complex