Targeting a Human Acyltransferase for Broad-Spectrum Antivirals

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Abstract SARS CoV-2 and related coronaviruses hijack host proteins to facilitate cell entry, replication and immune suppression. Targeting hijacked host proteins is an attractive strategy for development of broad-spectrum antiviral drugs because the same proteins are often targeted by multiple viruses. A global SARS-CoV-2/human protein/protein interaction analysis recently revealed one such target: the human acyltransferase DHHC5, which catalyzes palmitoylation of proteins to regulate trafficking in the endocytic pathway, was shown to interact with the SARS-CoV-2 Spike protein. This finding was exciting in itself, but in light of multiple lines of evidence indicating that DHHC5’s role in localizing proteins at the plasma membrane is hijacked by diverse pathogens to gain entry into the cell, it is compelling rationale for developing DHHC5 inhibitors to test as antivirals. We propose to develop selective DHHC5 inhibitors as lead molecules to test in animal models of coronavirus infection. Currently, the tools for a small molecule drug discovery effort for this target are lacking: there is very little structural information on DHHC family members and no robust HTS assays. The goals of this R21 proposal are to develop and validate the tools needed for discovery of DHHC5 inhibitors and initiate a lead discovery program. To address this, we will develop and validate a robust, quantitative high throughput DHHC5 enzymatic assay based on a coupled fluorescence polarization immunoassay (FPIA) that will serve as a critical tool for screening and performing hit-to-lead/SAR studies. We will use the assay to screen a diversity library, validate the hits and prioritize them based on physicochemical properties, potency, selectivity, mechanism of action and functional activity. Additionally, we will produce a cocrystal structure of DHHC5 in complex with a validated hit molecule. Completion of these aims will establish technical feasibility for pursuing a structure-driven design approach to discover lead molecules targeting DHHC5, which could ultimately result in the development of antivirals with broad spectrum activity against SARS-CoV-2 and coronavirus pathogens that emerge in the future.