Site-specific lipidation enhances IFITM3 membrane interactions and antiviral activity

Garst, Emma; Lee, Hwayoung; Das, Tandrila; Bhattacharya, Shibani; Percher, Avital; Wiewiora, Rafal; Witte, Isaac P.; Li, Yumeng; Goger, Michael; Peng, Tao; Im, Wonpil; Hang, Howard C.

Interferon-induced transmembrane proteins (IFITMs) are S-palmitoylated proteins in vertebrates that restrict a diverse range of viruses. S-palmitoylated IFITM3 in particular directly engages incoming virus particles, prevents their cytoplasmic entry, and accelerates their lysosomal clearance by host cells. However, the precise molecular mechanisms of action for IFITM-mediated viral restriction are still unclear. To investigate how site-specific S-palmitoylation controls IFITM3 antiviral activity, here we employed computational, chemical, and biophysical approaches to demonstrate that site-specific lipidation of IFITM3 at highly conserved cysteine 72 modulates its conformation and interaction with lipid membranes leading to enhanced antiviral activity of IFITM3 in mammalian cells. Collectively, our results demonstrate that site-specific S-palmitoylation of IFITM3 directly alters its biophysical properties and activity in cells to prevent virus infection.