Grant: Operating Grant

Certain digestive enzymes (proteinases), notably the blood-clotting enzyme thrombin and the digestive enzyme, trypsin, can act like hormones to regulate inflammation by activating a unique family of cell surface G-protein-coupled proteinase-activated receptors (PARs: Fig. 1). Our CIHR-funded project and work by others has shown that PARs play important roles in diseases like arthritis and asthma. The next frontier is to understand in depth, the molecular pharmacology of these intriguing receptors and to identify the endogenous and pathogen enzymes that regulate the PARs in vivo. The central hypothesis of this proposal is that both endogenous and pathogen-derived proteinases act like hormones, via the PARs, to play an inflammatory role in vivo. Questions that drive the main aims of this proposal are: (1) What receptor mechanisms are involved in signaling via the PARs? (2) Are distinct signals activated by the different PARs in the same cell and can these pathways be selectively activated by newly designed drugs, (3) What are the tissue or pathogen-derived proteinases that might regulate PARs in vivo? and (4) Can the PARs or the PAR-activating proteinases play an inflammatory role in vivo? Using newly developed tools, the proposal will deal with the four questions with the following aims: Aim 1: Assess the molecular pharmacology of PAR signaling with a focus on the structure-function properties of PARs 2 and 4. Aim 2: Determine structure-activity relationships (SARs) for PAR stimulants that can selectively activate unique PAR-triggered signals. Aim 3: Evaluate differential signaling by PARs 1, 2 and 4 and their site-mutated isoforms in a common cell background (e.g human airway or kidney epithelial cells) Aim 4: Evaluate the role of PAR2 and its pathogen-derived activating proteinases in an in-vivo model of allergen-induced airway inflammation. The data will surface new therapeutic targets for treating inflammatory diseases like asthma.