title: A sorting signal suppresses IFITM1 restriction of viral entry.
abstract: The interferon-induced transmembrane proteins (IFITMs) broadly inhibit virus infections, particularly at the viral entry level. However, despite this shared ability to inhibit fusion, IFITMs differ in the potency and breadth of viruses restricted, an anomaly that is not fully understood. Here, we show that differences in the range of viruses restricted by IFITM1 are regulated by a C-terminal non-canonical dibasic sorting signal KRXX that suppresses restriction of some viruses by governing its intracellular distribution. Replacing the two basic residues with alanine (KR/AA) increased restriction of jaagsiekte sheep retrovirus and 10A1 amphotropic murine leukemia virus. Deconvolution microscopy revealed an altered subcellular distribution for KR/AA, with fewer molecules in LAMP1-positive lysosomes balanced by increased levels in CD63-positive multivesicular bodies, where jaagsiekte sheep retrovirus pseudovirions are colocalized. IFITM1 binds to cellular adaptor protein complex 3 (AP-3), an association that is lost when the dibasic motif is altered. Although knockdown of AP-3 itself decreases some virus entry, expression of parental IFITM1, but not its KR/AA mutant, potentiates inhibition of viral infections in AP-3 knockdown cells. By using the substituted cysteine accessibility method, we provide evidence that IFITM1 adopts more than one membrane topology co-existing in cellular membranes. Because the C-terminal dibasic sorting signal is unique to human IFITM1, our results provide novel insight into understanding the species- and virus-specific antiviral effect of IFITMs.
authors.affiliation: From the Department of Molecular Microbiology and Immunology, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211.
authors.forename: Kun
authors.initials: K
authors.lastname: Li
authors.affiliation: the Key Laboratory of Molecular Microbiology and Biotechnology (Ministry of Education) and Key Laboratory of Microbial Functional Genomics (Tianjin), College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Jia
authors.affiliation: From the Department of Molecular Microbiology and Immunology, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211.
authors.forename: Minghua
authors.initials: M
authors.lastname: Li
authors.affiliation: From the Department of Molecular Microbiology and Immunology, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211.
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Zheng
authors.affiliation: From the Department of Molecular Microbiology and Immunology, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211.
authors.forename: Chunhui
authors.initials: C
authors.lastname: Miao
authors.affiliation: the Key Laboratory of Molecular Microbiology and Biotechnology (Ministry of Education) and Key Laboratory of Microbial Functional Genomics (Tianjin), College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Yunfang
authors.initials: Y
authors.lastname: Yao
authors.affiliation: the Department of Cellular and Molecular Biology, Texas Lung Injury Institute, University of Texas Health Science Center, Tyler, Texas 75708.
authors.forename: Hong-Long
authors.initials: HL
authors.lastname: Ji
authors.affiliation: the Key Laboratory of Molecular Microbiology and Biotechnology (Ministry of Education) and Key Laboratory of Microbial Functional Genomics (Tianjin), College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Yunqi
authors.initials: Y
authors.lastname: Geng
authors.affiliation: the Key Laboratory of Molecular Microbiology and Biotechnology (Ministry of Education) and Key Laboratory of Microbial Functional Genomics (Tianjin), College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Wentao
authors.initials: W
authors.lastname: Qiao
authors.affiliation: the Department of Microbiology, Immunology, and Biochemistry, University of Tennessee Health Science Center, Memphis, Tennessee 38163.
authors.forename: Lorraine M
authors.initials: LM
authors.lastname: Albritton
authors.affiliation: the McGill AIDS Centre, Lady Davis Institute, Montreal, Quebec H3T 1E2, Canada, and the Department of Microbiology and Immunology, McGill University, Montreal, Quebec H3A 2B4, Canada.
authors.forename: Chen
authors.initials: C
authors.lastname: Liang
authors.affiliation: From the Department of Molecular Microbiology and Immunology, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211, liushan@missouri.edu.
authors.forename: Shan-Lu
authors.initials: SL
authors.lastname: Liu
mesh_terms: D033963:Adaptor Protein Complex 3 / Q000378:metabolism*; D000818:Animals; D000943:Antigens, Differentiation / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002459:Cell Fusion; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D047468:Immunoprecipitation; D022141:Jaagsiekte sheep retrovirus / Q000502:physiology*; D008247:Lysosomes / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D021382:Protein Sorting Signals / Q000502:physiology*; D021381:Protein Transport; D012756:Sheep; D014777:Virus Diseases / Q000821:virology; D053586:Virus Internalization; D014779:Virus Replication
chemical_list: D033963:Adaptor Protein Complex 3; D000943:Antigens, Differentiation; D021382:Protein Sorting Signals; C062010:leu-13 antigen
keywords: Adaptor Protein; Interferon; Intracellular Trafficking; Retrovirus; Virus Entry