IFITM1/CD225

IFITM1, assigned CD225, is the shortest member of the interferon-induced transmembrane protein family, a cluster of small two-pass membrane proteins strongly induced by type I and type II interferons. Whereas IFITM3 resides mainly in endosomes and restricts influenza entry, IFITM1 accumulates at the plasma membrane and preferentially inhibits infection by enveloped viruses such as West Nile and SARS coronavirus through effects on membrane fusion. Historically known as 9-27 and Leu13, the molecule is abundant on endothelial cells and germ cell tumors, and IFITM1 expression in tumor cells can blunt oncolytic virus infection.