In the midst of the devastating COVID-19 pandemic, scientists are urgently seeking new ways to understand how viruses infiltrate and reprogram human cells. With the threat of future deadly viruses and pandemics emerging from the coronavirus family, the development of innovative therapies is crucial. One strategy for combating coronaviruses, including SARS-CoV-2 which causes COVID-19, is to target the mechanisms by which the virus hijacks our cells and coerces them to produce more viral particles. However, the vast number of human proteins that have the potential to interact with viral proteins presents a significant challenge in identifying the most relevant interactions for infection.
To address this challenge, a collaborative effort between multiple institutions has produced a valuable toolkit in fruit flies (Drosophila) called the Drosophila COVID Resource (DCR). This resource provides a convenient method for assessing key SARS-CoV-2 genes and their interactions with human proteins. Led by researchers from the University of California San Diego and the Baylor College of Medicine and Texas Children’s Hospital, the study detailing the creation and potential of the DCR was published in Cell Reports.
Viruses possess a remarkable ability to rapidly evolve, making it particularly difficult to control the SARS-CoV-2 virus. The DCR offers researchers the opportunity to quickly evaluate the functional effects of factors produced by this unique pathogen, as well as future variants. The DCR is designed as a versatile discovery system, comprising an assortment of fruit fly lines that produce each of the 29 known SARS-CoV-2 proteins and more than 230 key human targets. Additionally, it offers over 300 fly strains for assessing the counterparts to human viral targets.
During their analysis of the DCR, the researchers discovered that nine out of the ten SARS-CoV-2 proteins known as non-structural proteins (NSPs) resulted in wing defects in adult flies. These defects provide insights into how the viral proteins influence host proteins to disrupt crucial cellular processes for the virus’s benefit. An interesting finding was that one of the viral proteins, NSP8, functions as a hub by coordinating with other NSPs in a mutually reinforcing manner. NSP8 exhibited strong interactions with five of the 24 candidate human binding proteins. Notably, the human protein with the strongest interactions with NSP8 was an enzyme called arginyltransferase 1 (ATE1).
ATE1 modifies other proteins by adding the amino acid arginine, altering their functions. The researchers observed significantly higher levels of arginine-modified actin, a key cytoskeletal protein present in all human cells, in fly cells expressing both NSP8 and ATE1. Moreover, these cells formed abnormal ring-like structures coated with actin, similar to those observed in human cells infected with the SARS-CoV-2 virus. Encouragingly, when flies were treated with drugs that inhibit the activity of the human ATE1 enzyme, the effects of NSP8 were significantly reduced, suggesting a potential avenue for new therapeutics.
Termed a “fly-to-bedside” resource, the researchers believe that these initial findings represent just the beginning of drug screening possibilities. Eight of the other NSPs tested also produced distinct phenotypes, laying the groundwork for identifying additional drug candidates. The identification of new candidate drugs that target important viral-human interactions could complement existing antiviral treatments, such as Paxlovid, and provide insights into the causes of various long-COVID symptoms, ultimately leading to new treatment strategies.
The DCR represents a significant step forward in understanding the mechanisms of COVID-19 infection. By harnessing the genetic tools available in the fruit fly model system, this extensive collection of freely available reagents will facilitate a global analysis of how the SARS-CoV-2 virus interacts with human cells at molecular, tissue, and organ levels. The researchers hope that these resources will aid in the development of novel therapeutic strategies to combat the current pandemic and future health challenges posed by the SARS-CoV-2 virus and related family members.
The DCR is a valuable tool that will contribute to the ongoing fight against COVID-19 and pave the way for advancements in virology and therapeutic development. With millions of lives at stake and the potential for future pandemics, it is imperative that the scientific community continues to explore innovative approaches to combat viral infections. The DCR represents a significant step forward in understanding the intricacies of viral infections and provides hope for a healthier and more secure future.