title: The signal for clathrin-mediated endocytosis of the paramyxovirus SV5 HN protein resides at the transmembrane domain-ectodomain boundary region.
abstract: The hemagglutinin-neuraminidase (HN) glycoprotein of the paramyxovirus SV5 is internalized from the cell surface via clathrin-coated pits. However, the cytoplasmic domain of SV5 HN does not contain a previously characterized internalization motif. A cell-surface-expressed chimeric protein (APK), consisting of the cytoplasmic tail, transmembrane (TM) domain, and 12 residues of the ectodomain of HN joined to the cytoplasmic protein pyruvate kinase is internalized, indicating that the N-terminal region of HN contains an internalization signal. Although SV5 HN is internalized at a rate similar to that of influenza virus hemagglutinin (HA) mutant Y543, which contains a degenerate tyrosine-based signal in its cytoplasmic tail, the elimination of the majority of the HN cytoplasmic tail, or substitution of the HN TM domain with leucine residues, did not affect the rate of HN internalization. The HN protein of the closely related virus, Newcastle disease virus (NDV), is not internalized from the cell surface. Working under the usual convention that the TM domain consists of the hydrophobic residues bounded by two charged residues, analysis of internalization of mutant and chimeric NDV HN molecules indicates that the first seven SV5 HN ectodomain residues are critical for internalization of HN. A glutamic acid residue (E37) that abuts this presumptive HN TM domain/ectodomain boundary is important for SV5 HN internalization.
authors.affiliation: Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500, USA.
authors.forename: G P
authors.initials: GP
authors.lastname: Leser
authors.forename: K J
authors.initials: KJ
authors.lastname: Ector
authors.forename: D T
authors.initials: DT
authors.lastname: Ng
authors.forename: M A
authors.initials: MA
authors.lastname: Shaughnessy
authors.forename: R A
authors.initials: RA
authors.lastname: Lamb
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D002966:Clathrin / Q000502:physiology*; D004705:Endocytosis; D019084:Fluorescent Antibody Technique, Indirect; D018698:Glutamic Acid / Q000502:physiology; D015707:HN Protein / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D018108:Respirovirus / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013997:Time Factors; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D002966:Clathrin; D015707:HN Protein; D008565:Membrane Proteins; D010446:Peptide Fragments; D010455:Peptides; D014764:Viral Proteins; C027819:polyleucine; D018698:Glutamic Acid