Christopher Overall
Nevan Krogan
Christopher Overall is a Full Professor, Distinguished University Scholar and Canada Research Chair Laureate in Protease Proteomics and Systems Biology at the University of British Columbia.
Dr. Overall is best known for developing proteomic methodology to discover protease substrates in vivo, thereby establishing the field of degradomics. He has used these techniques to reveal new biological roles for proteases in immunity and disease, most recently in the COVID-19 pandemic by SARS-CoV-2 proteases, developing two new molecular correctors to cure MALT1 protease deficiency in a primary immunodeficiency, and now in One Health Strategies for investigation of viral zoonosis. By generating clinically relevant insights into how proteases dampen disease-fighting defence systems involved in inflammation and immunodeficiency, degradomics has revealed an unexplored layer of complexity in the hierarchy of cell and immune regulation, greatly adding to our understanding of protease function and drug targeting.
Escaping Immune Surveillance by Viral Proteolysis: Tunnelling Nanotubes and Gasdermin D Pores Leads to Extracellular Secretion and Activity of SARS-CoV-2 3CLpro (MPro)
Dr. Overall and his group identified and validated >200 host cell substrates of SARS-CoV-2 3CLpro/Mpro that they mechanistically investigated to reveal new pathways to evade host cell antiviral defences. Inactive Catalytic Domain Capture and MS identified interactors and substrates in the interactome of SARS-CoV-2 3CLpro/Main protease. Of 259 3CLpro interactors, 145 were associated with the cytoskeleton of which we determined kcat/kM for 139 3CLpro cut-sites from which they identified 29 efficiently cleaved substrates. They validated these as substrates in vitro, in SARS-CoV-2-infected human lung cells, and in mouse infection models.
OAS1 p46 is cleaved and inactivated by 3CLpro yet cannot escape RNaseL activation, which is activated by a novel proteolytic removal of its inhibitory domain. 3CLpro cleavage of adherens junction proteins initiated cytoskeletal rearrangement, activated zonular signalling and removed subcellular localization motifs to trigger translocation of nuclear TRIM28 and NUMA1 to adherens junctions, and YAP1 in the hippo pathway, to the nucleus.
Surprising, they discovered that 3CLpro and nucleocapsid protein are secreted from SARS-CoV-2 infected cells by unconventional protein secretion through GSDMD/E pores formed by viral 3CLpro activation at LH270↓271NF, generating a pore-forming N-terminal domain (GSDMD 1–270) that leads to 3CLpro release from cells.
Viral protease-induced cytoskeletal remodelling rapidly generated tunnelling nanotubes that connected lung epithelial cells and contained virus colocalized with 3CLpro substrates. TNTs form a conduit for transmission of SARS-CoV-2 and cellular proteins to non-infected recipient cells that are concealed from protective antibody and immune cell recognition. Moreover, 3CLpro escapes from infected cells and inactivates IFN-lambda.