HPV16 E6 augments Wnt signaling in an E6AP-dependent manner

Area of Science:

• Oncology
• Virology
• Molecular Biology

Background:

• The Wnt/beta-catenin pathway is frequently dysregulated in various cancers.
• Human Papillomavirus (HPV) oncoproteins, particularly HPV16 E6, are implicated in cervical carcinogenesis.
• Understanding the interplay between HPV oncoproteins and cellular signaling pathways is crucial for cancer research.

Purpose of the Study:

• To investigate the effect of HPV16 E6 on the Wnt/beta-catenin signaling pathway.
• To determine the specific mechanisms by which E6 influences Wnt signaling.
• To elucidate the role of E6-associated protein (E6AP) in this process.

Main Methods:

• Luciferase reporter assays to measure Wnt/beta-catenin/TCF-dependent signaling.
• Epistasis experiments to assess the involvement of key pathway components (GSK3beta, APC).
• Analysis of beta-catenin expression, stability, and cellular localization.
• Experiments with E6 mutants and E6AP knockdown to evaluate E6AP's role.

Main Results:

• Ectopically expressed HPV16 E6 dose-dependently augmented Wnt/beta-catenin/TCF signaling.
• This augmentation was independent of E6's p53-degrading activity or binding to PDZ targets.
• E6 did not affect beta-catenin's expression, stability, or cellular distribution.
• The ubiquitin ligase E6AP was essential for E6-mediated enhancement of Wnt signaling.

Conclusions:

• The HPV16 E6 oncoprotein potentiates the Wnt/beta-catenin signaling pathway.
• This potentiation is dependent on the E6/E6AP complex, specifically involving the ubiquitin ligase E6AP.
• The E6/E6AP-mediated augmentation of Wnt signaling may play a significant role in HPV-induced carcinogenesis.