title: The cytoplasmic domain of Marburg virus GP modulates early steps of viral infection.
abstract: Marburg virus infection is mediated by the only viral surface protein, GP, a trimeric type I transmembrane protein. While its ectodomain mediates receptor binding and fusion of viral and cellular membranes and its transmembrane domain is essential for the recruitment of GP into budding particles by the matrix protein VP40, the role of the short cytoplasmic domain has remained enigmatic. Here we show that a missing cytoplasmic domain did not impair trimerization, intracellular transport, or incorporation of GP into infectious Marburg virus-like particles (iVLPs) but altered the glycosylation pattern as well as the recognition of GP by neutralizing antibodies. These results suggest that subtle conformational changes took place in the ectodomain. To investigate the function of the cytoplasmic domain during viral entry, a novel entry assay was established to monitor the uptake of filamentous VLPs by measuring the occurrence of luciferase-labeled viral nucleocapsids in the cytosol of target cells. This quantitative assay showed that the entry process of VLPs incorporating GP missing its cytoplasmic domain (GPΔCD) was impaired. Supporting these results, iVLPs incorporating a mutant GP missing its cytoplasmic domain were significantly less infectious than iVLPs containing wild-type GP. Taken together, the data indicate that the absence of the short cytoplasmic domain of Marburg virus GP may induce conformational changes in the ectodomain which impact the filoviral entry process.
authors.affiliation: Institut für Virologie, Philipps Universität Marburg, Marburg, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Mittler
authors.forename: Larissa
authors.initials: L
authors.lastname: Kolesnikova
authors.forename: Bettina
authors.initials: B
authors.lastname: Hartlieb
authors.forename: Robert
authors.initials: R
authors.lastname: Davey
authors.forename: Stephan
authors.initials: S
authors.lastname: Becker
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D003593:Cytoplasm; D019084:Fluorescent Antibody Technique, Indirect; D006031:Glycosylation; D057809:HEK293 Cells; D006801:Humans; D008156:Luciferases; D029024:Marburgvirus / Q000378:metabolism / Q000472:pathogenicity / Q000502:physiology*; D009154:Mutation; D017434:Protein Structure, Tertiary; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D014763:Viral Matrix Proteins / Q000378:metabolism; D053586:Virus Internalization
chemical_list: D000911:Antibodies, Monoclonal; C081324:GP-protein, Marburg virus; C080981:VP40 protein, virus; D014759:Viral Envelope Proteins; D014760:Viral Fusion Proteins; D014763:Viral Matrix Proteins; D008156:Luciferases