Molecular modelling studies on Frizzled receptors and orphan GPCRs
Abstract
G protein-coupled receptors (GPCRs) mediate effects of many endogenous and exogenous substances such as small molecules, peptides, lipids, ions, and odorants. According to homology, GPCRs were grouped into Classes A, B, C, F, adhesion receptors, and other 7 transmembrane (TM) spanning receptors. In mammals, there are 10 Frizzleds (FZDs, FZD1-10), belonging to class F of GPCRs. This group of receptors is activated by the WNT family of lipoglycoproteins through interaction with the extracellular cysteine-rich domain (CRD). FZDs are critically involved in processes such as embryonic development, stem cell regulation, and adult tissue homeostasis. Deregulation of FZDs and associated pathways leads to pathogenesis, such as cancer and neurologic disorders; thus, making them attractive drug targets.
Our group is instrumental in promoting the understanding of molecular underpinnings of FZD activation including ligand-induced and constitutive activity. So far, our work has identified microswitch residues, that are important for FZD activation, has described mechanisms of FZD interaction with ligands, co-receptors and intracellular partners, and has developed FZD-centered assays helping to decipher mechanisms of FZD activation and signal initiation by analysis of ligand binding, receptor dynamics and effector coupling. We foresee that understanding the molecular details of receptor conformational changes will provide the basis to understand how FZDs define pathway selectivity in a class-wide manner, i. e. how FZDs can for example couple to the scaffold protein DVL or heterotrimeric G proteins.
An integral part of this understanding on a molecular level are computational modelling techniques such as molecular dynamics (MD) simulations and docking calculations. Planned projects for the upcoming allocation period include
- Investigations of the interactions and complex conformations of FZDs with its effector proteins.
- Discovery and description of FZD-targeting small molecule modulators. This has been successfully done for one FZD (results will be published soon) and will now be repeated for another member of the family.
- Description of allosteric mechanisms in FZD-activation and signal transduction.
- Investigations towards the modulation of FZDs and their signalling by its microenvironment.
Most of these projects will be pursued using MD simulations (usually all atom but we might also employ coarse grained simulations for larger systems or use enhanced sampling methods) as well as a project using mostly large library docking screens. All computationally derived insights will be confirmed in wet-lab experiments, for example, by mutating residues that form essential interactions in the models and evaluating the effect of these mutations in the wet-lab experiments. Several publications describing the successful integration of the experimental, structural and computational work in the lab have been published in the recent years, with more results being published soon, thereby continuing the strong publication record of recent years.
In addition to these investigations targeting FZDs, a small part of the allocation will be dedicated towards the investigation of molecular mechanisms of orphan GPCRs involved in metabolic diseases. This will mostly be done using MD simulations and will be pursued under supervision of Assistant Professor Paweł Kozielewicz.
