title: Glycosylation at hemagglutinin Asn-167 protects the H6N1 avian influenza virus from tryptic cleavage at Arg-201 and maintains the viral infectivity.
abstract: Cleavage of the hemagglutinin (HA) precursor (HA0) by trypsin, which produces the active HA1 and HA2 complex, is a critical step for activating the avian influenza virus (AIV). However, other tryptic cleavage sites on HA might also cause HA degradation and affect the virulence. Otherwise, HA is modified by glycosylation in the host cell. The conjugated glycans on HA may hinder the antigenic epitopes, and thus prevent the virus from being recognized and attacked by the antibodies. In this study, we observed that glycosylation at the Asn-167 (N167) site on the HA1 of the H6N1 AIV strain A/chicken/Taiwan/2838V/00 (2838V) protected Arg-201 (R201) from tryptic cleavage. The 2838V HA protein became sensitive to tryptic cleavage, whereas the glycans at N167 were removed by N-glycosidase F (PNGase-F). Furthermore, the infectivity of 2838V decreased when pretreated with PNGase-F and trypsin. Our observations suggest that the inaccessibility of the R201 residue of HA1 for tryptic cleavage, which is sterically hindered by glycosylation at N167, is a crucial factor for determining the infectivity of the AIV.
authors.affiliation: Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Jie-Long
authors.initials: JL
authors.lastname: He
authors.affiliation: School of Veterinary Medicine, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Yi-Chung
authors.initials: YC
authors.lastname: Chiu
authors.affiliation: Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Shih-Chung
authors.initials: SC
authors.lastname: Chang
authors.affiliation: School of Veterinary Medicine, National Taiwan University, Taipei 10617, Taiwan. Electronic address: chingho@ntu.edu.tw.
authors.forename: Ching-Ho
authors.initials: CH
authors.lastname: Wang
authors.affiliation: Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei 10617, Taiwan. Electronic address: juang@ntu.edu.tw.
authors.forename: Rong-Huay
authors.initials: RH
authors.lastname: Juang
mesh_terms: D000818:Animals; D001120:Arginine / Q000378:metabolism; D001216:Asparagine / Q000378:metabolism; D002460:Cell Line; D002642:Chick Embryo; D006031:Glycosylation; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006868:Hydrolysis; D009980:Influenza A virus / Q000502:physiology*; D014357:Trypsin / Q000378:metabolism*
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D001216:Asparagine; D001120:Arginine; D014357:Trypsin
keywords: Avian influenza virus; Glycosylation; Hemagglutinin; Monoclonal antibody; Tryptic cleavage