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Updated: Jan 30, 2026
Expression and Purification of Virus-like Particles for Vaccination
Published on: June 2, 2016
IFITM3 directly engages and shuttles incoming virus particles to lysosomes
Jennifer S Spence1, Ruina He2, Hans-Heinrich Hoffmann3
1Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA.
Abstract:
Interferon-induced transmembrane proteins (IFITMs 1, 2 and 3) have emerged as important innate immune effectors that prevent diverse virus infections in vertebrates. However, the cellular mechanisms and live-cell imaging of these small membrane proteins have been challenging to evaluate during viral entry of mammalian cells. Using CRISPR-Cas9-mediated IFITM-mutant cell lines, we demonstrate that human IFITM1, IFITM2 and IFITM3 act cooperatively and function in a dose-dependent fashion in interferon-stimulated cells. Through site-specific fluorophore tagging and live-cell imaging studies, we show that IFITM3 is on endocytic vesicles that fuse with incoming virus particles and enhances the trafficking of this pathogenic cargo to lysosomes. IFITM3 trafficking is specific to restricted viruses, requires S-palmitoylation and is abrogated with loss-of-function mutants. The site-specific protein labeling and live-cell imaging approaches described here should facilitate the functional analysis of host factors involved in pathogen restriction as well as their mechanisms of regulation.
Insights
Interferon-induced transmembrane proteins (IFITMs) cooperatively block viral entry. IFITM3 directs viruses to lysosomes, revealing host-pathogen interaction mechanisms.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Interferon-induced transmembrane proteins (IFITMs) are key innate immune proteins restricting viral infections.
- Understanding IFITM cellular mechanisms during viral entry is crucial but challenging.
Purpose of the Study:
- To elucidate the cooperative roles and cellular mechanisms of IFITM1, IFITM2, and IFITM3 in restricting viral entry.
- To visualize IFITM function in live mammalian cells during viral infection.
Main Methods:
- CRISPR-Cas9 gene editing to create IFITM-mutant cell lines.
- Site-specific fluorophore tagging of IFITMs.
- Live-cell imaging of viral entry and intracellular trafficking.
Main Results:
- Human IFITM1, IFITM2, and IFITM3 exhibit cooperative, dose-dependent antiviral activity in interferon-stimulated cells.
- IFITM3 localizes to endocytic vesicles, fuses with incoming viruses, and promotes their lysosomal trafficking.
- IFITM3 trafficking is virus-specific, dependent on S-palmitoylation, and impaired in loss-of-function mutants.
Conclusions:
- IFITMs function cooperatively to restrict viral entry, with IFITM3 playing a specific role in cargo trafficking to lysosomes.
- The developed live-cell imaging and labeling techniques offer a powerful platform for studying host-pathogen interactions and host restriction factors.
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