In Khaperskyy lab, we study virus-host interactions and cellular stress responses.
Our goal is to understand how cells respond to virus infection and other stresses to identify molecular pathways that can be targeted for host-directed antiviral therapies and cancer treatments.
Currently, there are two main research themes in the laboratory:
Functions of stress granules in intrinsic immune responses
Intrinsic immune responses are the cell’s first line of defense against invading pathogens. In virus-infected cells these responses are activated following detection of pathogen-associated molecular patterns (PAMPs) that are normally absent from uninfected cells (e.g. viral genomic RNA).
One of the activated responses is the transient translation arrest. This arrest interferes with viral gene expression because viruses are dependent on host translation machinery for their own protein synthesis. Following translation arrest, polysome-free messenger ribonucleoproteins recruit RNA-binding proteins with self-aggregating properties which nucleate the formation of stress granules (SGs) in the cytoplasm of virus-infected cells.
Many viruses evolved countermeasures that prevent translation arrest and SG formation. Interestingly, SG inhibition is often blocked by viruses even when global translation arrest is induced, suggesting that in addition to being the indicators of global translation arrest, SGs themselves may have antiviral functions. Characterizing the functional role of SG formation in innate immune responses is one of our research objectives.
McCormick, C. and Khaperskyy, D.A. (2017) Translation inhibition and stress granules in the antiviral immune response. Nat. Rev. Immunol. 10:647-660.
Khaperskyy, D.A., Emara, M. M., Johnston, B.P., Anderson, P., Hatchette, T.F., and McCormick, C. (2014) Influenza A virus host shutoff disables antiviral stress-induced translation arrest. PLoS Pathog. 10: e1004217.
Khaperskyy, D.A., Hatchette, T.F., and McCormick, C. (2012) Influenza A virus inhibits cytoplasmic stress granule formation. FASEB J. 26: 1629-39.
Influenza A virus host shutoff
To gain preferential access to the protein synthesis machinery and to disrupt induction of antiviral responses by infected cell many viruses block host gene expression. This blockade is called host shutoff and it is mediated by viral factors that either destroy host messenger RNAs (mRNAs) or interfere with their synthesis.
Influenza A virus (IAV) encodes a host shutoff endonuclease PA-X, and our recent work in collaboration with the laboratory of Dr. Marta Gaglia at Tufts University (Boston, MA) revealed that PA-X cleaves cellular mRNAs but not the other types of host RNA (e.g. ribosomal RNA) or viral mRNAs.
A short 61 amino acid C-terminal region of PA-X, termed X-ORF, is highly conserved in mammalian and avian IAV strains and is necessary for PA-X shutoff activity. Our studies demonstrated that the X-ORF mediates nuclear accumulation of PA-X, and that PA-X can degrade both cytoplasmic and nuclear host mRNAs.
Our ongoing collaboration with Gaglia lab is aimed at understanding the specificity of PA-X and the role of X-ORF in RNA target selection.
Khaperskyy, D.A., Schmaling, S., Larkins-Ford, J., McCormick, C., and Gaglia, M.M. (2016) Selective degradation of host RNA polymerase II transcripts by influenza A virus PA-X host shutoff protein. PLoS Pathog. 12: e1005427.
Khaperskyy, D.A. and McCormick, C. (2015) Timing Is Everything: Coordinated Control of Host Shutoff by Influenza A Virus NS1 and PA-X Proteins. J Virol. 89:6528-31.