Subventions et des contributions :

Subvention ou bourse octroyée s'appliquant à plus d'un exercice financier. (2017-2018 à 2022-2023)

THE CASPASE PROTEOLYTIC SYSTEM
Peptidases shape all aspects of a cell's life, including its death. Cell death by apoptosis is governed by cysteinyl peptidases named caspases that alter cellular functions to provoke cell demise. Only a few of the hundreds of proteolytic events attributed to caspases have established relevance. Thus, identifying key substrates is crucial to fully understand apoptosis. The renewal of our Discovery Grant builds on knowledge made in the past years that includes a high impact discovery in the field that is the identification of the first exosite in a caspase that explains how caspase-7 selects critical substrates such as PARP-1 for proteolysis. The evolution of an exosite is a tribute to the importance of the substrates it binds. My program builds on this finding and focuses on the mechanisms of substrate recognition by caspases and its impact on apoptosis and other caspase roles. Therefore, over the next 5 years, we will expand the concept of exosites in caspases as a general modality for substrate recognition ( Project 1 ) and, because of the relevance to cellular homeostasis, study the particular cases of caspase-mediated cleavage of proteins involved in intracellular vesicle trafficking ( Project 2 ).
PROJECT 1: EXOSITES AS A FUNDAMENTAL MODALITY FOR SUBSTRATE RECOGNITION BY CASPASES
We postulate that exosites are common in caspases. To validate this hypothesis, we propose to 1) use proteomics and biochemical approaches to identify and validate the substrate repertoire that uses the caspase-7 exosite for their effective cleavage; 2) generate a transgenic mouse with a mutated caspase-7 exosite and characterize the response of cell populations and whole animals to caspase-related stimuli to establish the in vivo role of the exosite; and 3) expand exosite-mediated proteolysis to other caspases by searching for exosites in caspase-6. The generalization of exosite-mediated proteolysis will impact our view of apoptosis and caspase substrate recognition.
PROJECT 2: CASPASES AS REGULATORS OF INTRACELLULAR VESICLE TRAFFICKING
Caspases target vesicle trafficking by cleaving many proteins, the effect of which is poorly understood. Thus, this project focuses on the impact caspase activity has on vesicle trafficking in general and prototypical proteins in particular. To do so, we will 1) identify proteins involved in trafficking that are caspase substrates using proteomics and existing caspase substrate databases; and 2) study the role of individual protein cleavage on trafficking. To this end, we recently identified the SNX2 protein as a caspase substrate involved in the trafficking and signaling of the HGF tyrosine kinase receptor.
Because apoptosis is very efficacious in removing unwanted cells, understanding the cellular mechanisms behind such efficacy will shed light on the situations where it fails to work properly and alters cellular homeostasis leading to diseases.