Exploring an aggregon in the Wnt pathway regulator conductin/axin2 as target for cancer therapy

• Applicant: Dr. Dominic Bernkopf
• Subject Area: Cell Biology ; Structural Biology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 456050310

Conductin/axin2 is a negative feedback regulator of the oncogenic Wnt/beta-catenin signaling pathway. Although conductin is highly expressed in colorectal cancer due to pathologic hyperactivity of the Wnt pathway, here it fails to control signaling activity and to prevent cancer growth. Recently, I discovered an aggregon in the conductin RGS domain that reduces conductin activity by interfering with its polymerization. Targeting this aggregon by a synthetic peptide (p182-195-R9) promotes conductin polymerization, inhibits Wnt signaling and suppresses growth of colorectal cancer cells in vitro. Thus, p182-195-R9-induced amplification of conductin activity may allow exploiting the high conductin expression levels in colorectal cancer for targeted therapy. Here, I want to investigate inhibition of colorectal cancer growth by p182-195-R9 in vivo using mouse models. Moreover, the effects of p182-195-R9 treatment on self-renewal and differentiation of cancer stem cells and intestinal stem cells will be assessed in 3D organoid cultures. For deeper mechanistic insights into RGS domain aggregation and its inhibition, we aim at determining the X-ray crystal structure of the conductin RGS domain alone and in complex with p182-195-R9. Studying conductin polymerization from the perspective of biomolecular condensation (a process of liquid-liquid phase separation forming membraneless organelles) may reveal how aggregation interferes with conductin polymer assembly. In addition, we will screen libraries of FDA-approved drugs and drug-like compounds for small-molecule aggregation inhibitors, which could serve as p182-195-R9 alternatives in the future. Finally yet importantly, we want to screen for conductin interactors that physiologically regulate Wnt signaling by targeting the aggregon. In summary, this study aims at understanding the aggregation mechanism and how aggregation impairs conductin assembly, characterizing p182-195-R9 as tool for interrogating the Wnt/beta-catenin signaling pathway, and exploring its potential for colorectal cancer therapy. Furthermore, identifying conductin interactors targeting the aggregon will reveal new aspects of Wnt signaling regulation and, potentially, unexpected connections with other pathways.

• DFG Programme: Research Grants