Biomolecular NMR & Protein Research - Research Activities

Bivalent Bridged Polypeptides for Tumour-targeting, Imaging and Controllable Therapeutic Intervention

Antifungal Strategies Targeting Candida albicans Signalling and Infection-induced Blood Coagulation (sepsis)

Development of Bivalent/Multivalent Polypeptide Systems for the Study of Biological Signalling Networks

Bivalent Bridged Polypeptides for Tumour-targeting, Imaging and Controllable Therapeutic Intervention

Contact: Feng Ni
Tel.: (514) 496-6729
E-mail: feng.ni@cnrc-nrc.gc.ca

The Biomolecular NMR and Protein Research Group envisages that the next generation of bio-pharmaceuticals for effective treatment of cancer will be "smart" molecular medicines that include a controllable therapeutic intervention element, and that may at the same time contain a target-homing functionality for tumour-specific delivery, and a molecular beacon or contrast agent for imaging. The group utilizes the strategy of linking weak-binding (monovalent) peptides to create high-affinity bivalent conjugates for the design of either therapeutic (inhibitory) or target-homing polypeptides. One unique advantage of bivalent ligand designs is the potential for switching functional binding on/off, paving the way for the fabrication of nano-molecular devices that can be activated selectively at sites of need. The group identifies monovalent peptides either by dissecting a functionally or structurally defined protein-protein interface or through screening of phage-displayed peptide libraries. Using these methods, the Group has identified potent bivalent polypeptides binding to human cathepsin B as well as many monovalent peptide binders for two other established tumor markers, human progranulin and human clusterin. The group plans to evaluate the in-vivo efficacy of bivalent homing peptides using mouse models and couple the homing peptides to magnetic nanoparticles (MNPs) to achieve both in-vivo availability and more effective targeting through multivalency.

Antifungal Strategies Targeting Candida albicans Signalling and Infection-induced Blood Coagulation (sepsis)

Contact: Feng Ni
Tel.: (514) 496-6729
E-mail: feng.ni@cnrc-nrc.gc.ca

C. albicans can cause severe blood-borne infections, leading to inflammation of the endothelium, activation of blood coagulation and ultimately septic shock. During disseminated infection, invading Candida cells can trigger blood coagulation through the generation of active factor Xa and the prothrombinase, which converts prothrombin into thrombin. The Biomolecular NMR and Protein Research Group aims to design multifunctional molecules containing homing moieties to deliver therapeutic anticoagulants as part of new treatment strategies for Candida infection. The group has developed a new generation of potent bivalent inhibitors of thrombin containing only genetically-encodable amino acids that can incorporate both targeting and therapeutic peptides in one molecule. This work is being extended to the design of direct thrombin inhibitors (DTIs) that contain targeting moieties to circulating blood components to enable disease- or site-specific delivery of therapeutic anticoagulants.

The Biomolecular NMR and Protein Research Group also examines protein-ligand interactions involving the C. albicans Rho-family of small GTPases, especially CaCdc42 and Rho1, known to play a key role in host colonization and invasion by the fungal pathogen. Analysis of the cell signaling interactions of CaCdc42 by use of NMR and fluorescence spectroscopy revealed a bivalent mechanism that promotes low-affinity binding to high-affinity protein-protein interactions. This newly-identified bivalent mechanism of the Cdc42-effector interaction is being used to guide the design of small-molecule inhibitors of yeast Rho GTPases as specific antifungal agents.

Development of Bivalent/Multivalent Polypeptide Systems for the Study of Biological Signalling Networks

Contact: Dmitri Tolkatchev
Tel.: (514) 496-7617
E-mail: dmitri.tolkatchev@cnrc-nrc.gc.ca

The Biomolecular NMR and Protein Research Group started a new international collaboration with the RIKEN Genomic Sciences Center, Japan on a three-year (2005-2007) research program entitled "Functional-Proteomics Approaches for Comprehensive Analyses of Molecular Interactions". This collaborative research brings together two complementary approaches to understand protein function, both via the discovery of ligands targeting specific proteins or protein structures. RIKEN focuses on non-peptide organic compounds and the use of surface-plasmon resonance (SPR), mass spectrometry and NMR spectroscopy to characterize protein-ligand interactions. The Biomolecular NMR and Protein Research Group uses structure-based design and combinatorial selection to discover polypeptide ligands as inhibitors of selected proteins with critical regulatory functions. The ultimate goal is to identify weak spots of cellular machineries and signaling networks, which can be regulated or attacked by designer molecular devices or therapeutic agents. In this regard, bivalent polypeptides will be explored together with NMR spectroscopy as sensors for the ranking of small-molecule binding to target proteins. This will be followed by the design of universal linkers and the matching linker-binding proteins to create nanomoleclular conjugates for selective manipulation of signaling protein networks. Functional information emerging from these studies will be used for refining or focusing small-molecule discovery efforts to 'druggable' protein-protein interactions.

Related Information

Institutes:

• NRC Biotechnology Research Institute