HPV16 E6 and E6AP differentially cooperate to stimulate or augment Wnt signaling

Area of Science:

• Molecular biology
• Cellular signaling
• Oncology

Background:

• The Wnt signaling pathway is crucial in cellular processes and implicated in cancer.
• The roles of HPV E6 and E6AP in Wnt pathway regulation remain incompletely understood.

Purpose of the Study:

• To investigate the functional interactions between HPV E6 and E6AP in the context of Wnt signaling.
• To elucidate the mechanism by which E6AP influences Wnt/beta-catenin/TCF transcription.

Main Methods:

• Cell-based assays involving coexpression of E6 and E6AP.
• Western blotting to assess protein levels (E6, beta-catenin).
• Luciferase reporter assays to measure TCF transcriptional activity.
• Proteasomal degradation assays.

Main Results:

• E6 levels decrease upon Wnt pathway activation.
• E6AP coexpression, alone or with E6, stabilizes E6 and enhances Wnt/beta-catenin/TCF transcription.
• E6AP alone increases beta-catenin levels, promotes its nuclear accumulation, and activates transcription.
• E6AP/E6 protect beta-catenin from proteasomal degradation, dependent on E6AP activity, GSK3beta, and beta-catenin phosphorylation.

Conclusions:

• E6AP is identified as a novel regulator of the Wnt signaling pathway.
• E6AP cooperates with E6 to stimulate Wnt/beta-catenin signaling.
• This interaction may play a role in HPV-associated carcinogenesis.