The SARS-CoV-2 main protease causes mitochondrial dysfunction in a yeast model

Saccharomyces cerevisiae has proven to be an invaluable model organism for studying mitochondrial function owing to its genetic tractability and the high conservation of mitochondrial processes among eukaryotes, including humans. Yeasts are easy to culture and manipulate genetically, which allows rapid generation of mutant strains and detailed dissection of mitochondrial pathways. In addition, the ability of yeasts to survive without functional mitochondria allows the study of mutations that are lethal to organisms that are dependent on aerobic metabolism. Taking advantage of these benefits, we investigated the toxicity of SARS-CoV-2 main protease (Mpro) expression in yeast under conditions that enforce mitochondria-dependent aerobic metabolism. Our results showed that Mpro expression was highly toxic and significantly impaired yeast growth. Pronounced changes in the morphology and mitochondrial function were observed, indicating that mitochondrial pathways are exceptionally sensitive to Mpro activity. These results provide insights that may be relevant for understanding the effects of Mpro in more complex eukaryotic systems. Increasing amounts of data suggest that in cells infected with Betacoronavirus pandemicum (SARS-CoV-2), mitochondria are central to understanding COVID-19 pathogenesis. In human and rodent cells multiple mitochondrial changes, both structural and functional, have been found to have far-reaching consequences. These include hijacked mitochondria, reprogrammed metabolism, decreased oxidative phosphorylation (OXPHOS), increased reactive oxygen species (ROS) production, elevated mitochondrial iron levels, loss of mitochondrial integrity, cell death, disturbed autophagy, a reduced mitochondrial antiviral response (MAVS) and a type 1 interferon (IFN) response (see [1] [2] [3] ). Twenty out of 27 viral proteins have been implicated in these processes and have been shown to interact with host mitochondria 4, 5 . The SARS-CoV-2 main protease (Mpro), also known as 3-chymotrypsin-like protease (3CLpro), is a dimeric cysteine protease that is responsible for the cleavage of the viral polyproteins pp1a and pp1b, which are required for viral replication and transcription 6 . This enzyme shows no homology to human proteases and is thus an interesting drug target. As viral proteases cleave host proteins to hinder host immune responses and promote viral replication, numerous host proteins are predicted, via both computational and experimental methods, to be targeted by Mpro 7 . The human proteins confirmed to be cleaved include RNA polymerase II-associated protein 1 (RPAP1), Interleukin-1 receptor-associated kinase 1 (IRAK-1), nucleotide-binding oligomerization domain-like receptor (NLR), Solute carrier family 25 member 22 (SLC25A22) 7 . Among other processes, Mpro activity has been shown to influence human cell transcription and translation, apoptosis, the DNA damage response, lipid metabolism, vesicle trafficking, and the innate immune..