-Palmitoylation and Sterol Interactions Mediate Antiviral Specificity of IFITMs.

Interferon-induced transmembrane proteins (IFITM1, 2, and 3) are important antiviral proteins that are active against many viruses, including influenza A virus (IAV), dengue virus (DENV), Ebola virus (EBOV), Zika virus (ZIKV), and severe acute respiratory syndrome coronavirus (SARS-CoV). IFITM proteins exhibit specificity in activity, but their distinct mechanisms of action and regulation are unclear. Since -palmitoylation and cholesterol homeostasis are crucial for viral infections, we investigated IFITM interactions with cholesterol by photoaffinity cross-linking in mammalian cells along with molecular dynamic simulations and nuclear magnetic resonance analysis in vitro.

Chemical approaches for investigating site-specific protein S-fatty acylation.

Protein S-fatty acylation or S-palmitoylation is a reversible and regulated lipid post-translational modification (PTM) in eukaryotes. Loss-of-function mutagenesis studies have suggested important roles for protein S-fatty acylation in many fundamental biological pathways in development, neurobiology, and immunity that are also associated with human diseases. However, the hydrophobicity and reversibility of this PTM have made site-specific gain-of-function studies more challenging to investigate.

Site-Specific Lipidation Enhances IFITM3 Membrane Interactions and Antiviral Activity.

Interferon-induced transmembrane proteins (IFITMs) are -palmitoylated proteins in vertebrates that restrict a diverse range of viruses. -palmitoylated IFITM3 in particular engages incoming virus particles, prevents their cytoplasmic entry, and accelerates their lysosomal clearance by host cells. However, how -palmitoylation modulates the structure and biophysical characteristics of IFITM3 to promote its antiviral activity remains unclear.