Eligible Student Poster 49th Lorne Conference on Protein Structure and Function 2024

Structural insight into G protein coupling and activation of human Frizzled 5 receptor (#101)

Susovan Das 1 2 3 4 , Wessel Burger 1 2 3 , Hariprasad Venugopal 5 , Katrina Black 1 , Tin Nguyen 1 , Lilian Wong 1 , Hannes Schihada 6 , P Malamos 6 , Gunner Schulte 6 , Alisa Glukhova 1 2 4 5 7
  1. Structural Biology Division, Walter and Eliza Hall Institute of Medical Research (WEHI), Parkville, VICTORIA, Australia
  2. Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
  3. Department of Biochemistry and Pharmacology, University of Melbourne, Parkville, Victoria, Australia
  4. ARC Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
  5. Ramaciotti Centre for Cryo-Electron Microscopy, Monash University, Clayton, Victoria, Australia
  6. Receptor Biology & Signaling, Department of Physiology & Pharmacology, Karolinska Institutet, Stockholm, Sweden
  7. Drug Discovery Biology, , Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia

Frizzled (FZD) receptors tightly regulate different biological processes and are involved in various diseases, including multiple cancers. Wingless/Int1 (Wnt) family proteins act as ligands for FZDs. They initiate distinct signalling pathways broadly categorized into the "canonical" or beta-catenin-dependent and the "non-canonical" pathways. At least some non-canonical pathways are mediated via FZD coupling to heterotrimeric G proteins. There is no structural information on how Wnts bind to and activate full-length FZDs. However, due to high levels of constitutive activity, there are now multiple structures of FZD receptors bound to G proteins in the absence of ligands.

FZD5 significantly promotes the proliferation, DNA damage repair, and stemness of chemo-resistant triple-negative breast cancer. Additionally, FZD5 drives epithelial-mesenchymal transitions and tumorigenesis in various cancer types, highlighting its potential as a valuable therapeutic target. To understand the structural basis for FZD5 activation and G protein coupling, we determined the first cryo-electron microscopy structure of the FZD5-mGq complex to 2.7 Å resolution. The FZD5-mGq structure closely resembles those of other FZD-G protein complexes. The N-terminal CRD domain was visualized at a lower (6 Å) resolution for the first time. However, the G protein adopts a unique position relative to the receptor, and a unique density was observed at the receptor-G protein interaction site. Our future studies focus on understanding the FZD-G protein coupling and the role of CRD in FZD receptor activation.