S-Palmitoylation and Sterol Interactions Mediate Antiviral Specificity of IFITMs

Abstract

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 S-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. These studies suggest that cholesterol can directly interact with S-palmitoylated IFITMs in cells and alter the conformation of IFITMs in membrane bilayers. Notably, we discovered that the S-palmitoylation levels regulate differential IFITM protein interactions with cholesterol in mammalian cells and specificity of antiviral activity toward IAV, SARS-CoV-2, and EBOV. Our studies suggest that modulation of IFITM S-palmitoylation levels and cholesterol interaction influence host susceptibility to different viruses.

The Integral Membrane Protein ZMPSTE24 Protects Cells from SARS-CoV-2 Spike-Mediated Pseudovirus Infection and Syncytia Formation

“…One possibility is that ZMPSTE24 controls membrane fluidity by directly or indirectly altering lipid content in the cell, which could then affect IFITM accumulation or activity at the sites of viral-host cell membrane fusion. Alternatively, ZMPSTE24 could bind cholesterol, as IFITM3 has been shown to do ( 60 , 61 ), either on its own or together with the IFITMs, in a way that contributes to blocking viral host-cell fusion. Further studies examining whether ZMPSTE24 affects membrane composition, and/or whether loss of ZMPSTE24 prevents membrane stiffening by the IFITM proteins, could help explain the interdependence of the IFITMs and ZMPSTE24.…”

Revealing the characteristics of ZIKV infection through tissue-specific transcriptome sequencing analysis

“…Also, 62 genes were specifically differentially expressed after 12 h of treatment in JEG-3 cells (Supplementary Table 26 ). For example, IFITM1 is a member of interferon family that induced antiviral proteins, which restricts cellular entry by diverse viral pathogens, such as influenza A virus, Ebola virus and SARS-CoV-2 [ 69 ]. Besides, 148 genes were specifically differentially expressed in placenta cells after 24 h of infections (Supplementary Table 27 ).…”

Identification of potential modulators of IFITM3 by in-silico modeling and virtual screening

“…The top binding site was found to have residues important for post translational modifications, like Lys83, Lys104 which get ubiquitinated and Cys71, Cys72 which get Palmitoylated. Lys104 is also a part of CARC motif which is important for cholesterol binding 14 , 15 . This site was also found to have good druggable score.…”

“…The top hits from both FDA and Super Natural II datasets interact with the Lys104 which is part of the cholesterol binding site in IFITM3 (Figs. 4 , 5 , 6 , 7 ) 15 . Top hits from the FDA dataset (Supplementary Fig.…”

“…IFITM3 was shown to interact with cholesterol through residues from amphipathic helix (residues 59–68) and cholesterol binding domain (CARC motif; residues 104–113). This interaction with cholesterol is required for its antiviral activity 14 , 15 .…”