Host Factors for SARS-CoV-2 and Common Cold Coronaviruses - BiopharmaDirect

Host Factors for SARS-CoV-2 and Common Cold Coronaviruses

Brief Description

The Coronaviridae are a family of viruses that cause disease in humans ranging from mild respiratory infection to potentially lethal acute respiratory distress syndrome. Finding host factors common to multiple coronaviruses could facilitate the development of therapies to combat current and future coronavirus pandemics. Researchers conducted genome-wide CRISPR screens in cells infected by SARS-CoV-2 as well as two seasonally circulating common cold coronaviruses, OC43 and 229E. This approach correctly identified the distinct viral entry factors ACE2 (for SARS-CoV-2), aminopeptidase N (for 229E), and glycosaminoglycans (for OC43). Additionally, they identified phosphatidylinositol phosphate biosynthesis and cholesterol homeostasis as critical host pathways supporting infection by all three coronaviruses. By contrast, the lysosomal protein TMEM106B appeared unique to SARS-CoV-2 infection. Pharmacological inhibition of phosphatidylinositol kinases and cholesterol homeostasis reduced replication of all three coronaviruses. These findings offer important insights for the understanding of the coronavirus life cycle and the development of host-directed therapies.

"What is unique about our study is that we didn't just look at SARS-CoV-2, but other coronaviruses at the same time," says one of the leaders of the study, Melanie Ott, MD, Ph.D., director of the Gladstone Institute of Virology. "This gives us a good idea of drug targets that could broadly suppress many coronaviruses."

More work is needed to test the effectiveness of drugs targeting PIP and cholesterol, and whether they can effectively stop viral growth without causing dangerous side effects. The team would also like to repeat the screens using other coronaviruses—including the first SARS-CoV and MERS viruses—to determine just how universal the new targets they pinpointed are.

Ott and Puschnik agree that the current study was made possible by researchers from many labs coming together without hesitation. Puschnik has expertise in studying viral host factors, but didn't have access to a Biosafety Level 3 (BSL-3) lab required to work with SARS-CoV-2. Ott was spearheading Gladstone's effort to open such a lab earlier this year and offered to collaborate. Scientists at Synthego provided the engineered cells needed to study the viruses, and Gladstone Senior Investigator Nevan Krogan, Ph.D., helped analyze the results of the CRISPR-Cas9 screen.

Melanie Ott, MD, PhD
Senior Investigator, Gladstone Institute of Virology and Immunology
Professor
Department of Medicine
mott@gladstone.ucsf.edu

My laboratory is interested in the molecular mechanisms of viral pathogenesis. We focus on two viruses: HIV-1 and Hepatitis C Virus (HCV). Both are important public health problems and share common traits including high propensities to establish chronic infections and a lack of efficient vaccines. Our HIV efforts focus on viral transcription and latency as remaining barriers to viral eradication. We focus specifically on posttranslational modifications of the HIV transactivator Tat as potential targets to manipulate viral transcription therapeutically. In the past, we defined Tat acetylation and deacetylation as important steps in the Tat transactivation cycle and recently identified acetylation of the RNA polymerase II as an important regulatory step in transcription elongation. We are also interested in Tat-host cell interactions, specifically how Tat expression in infected T cells dysregulates immune functions and supports a premature aging syndrome observed in HIV+ individuals. Our HCV research focuses on the interaction of viral proteins with intracellular lipid droplets. These organelles play a critical role in the assembly of HCV progeny virions and are occupied in infected cells by the HCV nucleocapsid core. We recently showed that core interacts with the triglyceride-synthesizing enzyme DGAT1, and that this interaction plays a central role in the recruitment of core to lipid droplets. We are currently defining the role of lipid droplets in related viruses such as Dengue and Zika Virus and performed a comprehensive protein:protein interaction analysis of HCV proteins and hepatoma cells, which identified many novel factors involved in the infection. Both, HCV and HIV research in my laboratory includes replication studies with infectious viral clones, which are performed in the BSL3 laboratory. Recent rotation projects in the lab:

• defining the interaction of Dengue virus with lipid droplets
• characterizing a new posttranslational modification of Tat at lysine 71
• validating interaction partners of SIRT1 in T cells

Source: https://bms.ucsf.edu/people/melanie-ott-md-phd

ANDREAS PUSCHNIK, PH.D.
Biohub Fellow, Infectious Disease Initiative
andreas.puschnik@czbiohub.org

Puschnik carried out his thesis research in Jan Carette’s lab at Stanford, where he devised haploid and CRISPR genetic screens to identify host factors that are critical for viral infection. He applied these techniques to dengue, Zika, and hepatitis C, which revealed novel antiviral targets. As a Biohub Fellow, Puschnik plans to continue using CRISPR and other powerful genetic screens to study both persistent and emerging viruses as well as cellular pathways important for their virulence.