{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T11:21:02Z","timestamp":1787570462933,"version":"build-2736575974"},"reference-count":50,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T00:00:00Z","timestamp":1787529600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:p>Interferon-induced transmembrane proteins (IFITMs) are small interferon-stimulated membrane proteins that can limit viral entry, but their effects depend on the virus, entry route, and experimental context. This Mini Review focuses on IFITM3 at the viral fusion-pore checkpoint, defined here as the transition at which hemifusion either proceeds to fusion-pore opening and viral-content release or stalls before productive entry. Work on influenza virus supports a model in which IFITM3 remodels late-endosomal membranes, prolongs or kinetically stabilizes hemifusion-like intermediates, and raises the activation-energy barrier to fusion-pore formation. Type I interferon signaling, host biological variation, IFITM3 polymorphisms, and post-translational regulation shape IFITM3 abundance and localization, whereas endolysosomal cholesterol homeostasis modifies the membrane environment encountered by incoming virions; whether altered sterol handling also changes IFITM3 turnover remains unresolved. The fusion-pore checkpoint is presented as a working model supported most directly by mechanistic studies of influenza A virus. Coronavirus studies and a Nipah virus entry model illustrate how IFITM phenotypes can shift among restriction, neutrality, and context-dependent support. We therefore interpret IFITM activity as an entry-route-dependent membrane phenotype and outline practical criteria for assigning these outcomes in viral entry studies.<\/jats:p>","DOI":"10.3389\/fimmu.2026.1928879","type":"journal-article","created":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T10:33:01Z","timestamp":1787567581000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["IFITM3 at the viral fusion-pore checkpoint: membrane energetics and entry-route-dependent outcomes"],"prefix":"10.3389","volume":"17","author":[{"given":"Luyu","family":"Mao","sequence":"first","affiliation":[{"name":"College of Veterinary Medicine, Northeast Agricultural University","place":["Harbin, Heilongjiang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Siqi","family":"Wang","sequence":"additional","affiliation":[{"name":"College of Veterinary Medicine, Northeast Agricultural 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