title: TMPRSS2 and TMPRSS4 facilitate trypsin-independent spread of influenza virus in Caco-2 cells.
abstract: Proteolysis of influenza virus hemagglutinin by host cell proteases is essential for viral infectivity, but the proteases responsible are not well defined. Recently, we showed that engineered expression of the type II transmembrane serine proteases (TTSPs) TMPRSS2 and TMPRSS4 allows hemagglutinin (HA) cleavage. Here we analyzed whether TMPRSS2 and TMPRSS4 are expressed in influenza virus target cells and support viral spread in the absence of exogenously added protease (trypsin). We found that transient expression of TMPRSS2 and TMPRSS4 resulted in HA cleavage and trypsin-independent viral spread. Endogenous expression of TMPRSS2 and TMPRSS4 in cell lines correlated with the ability to support the spread of influenza virus in the absence of trypsin, indicating that these proteases might activate influenza virus in naturally permissive cells. Indeed, RNA interference (RNAi)-mediated knockdown of both TMPRSS2 and TMPRSS4 in Caco-2 cells, which released fully infectious virus without trypsin treatment, markedly reduced the spread of influenza virus, demonstrating that these proteases were responsible for efficient proteolytic activation of HA in this cell line. Finally, TMPRSS2 was found to be coexpressed with the major receptor determinant of human influenza viruses, 2,6-linked sialic acids, in human alveolar epithelium, indicating that viral target cells in the human respiratory tract express TMPRSS2. Collectively, our results point toward an important role for TMPRSS2 and possibly TMPRSS4 in influenza virus replication and highlight the former protease as a potential therapeutic target.
authors.affiliation: Institute of Virology, Hannover Medical School, 30625 Hannover, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Bertram
authors.forename: Ilona
authors.initials: I
authors.lastname: Glowacka
authors.forename: Paulina
authors.initials: P
authors.lastname: Blazejewska
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Soilleux
authors.forename: Paul
authors.initials: P
authors.lastname: Allen
authors.forename: Simon
authors.initials: S
authors.lastname: Danisch
authors.forename: Imke
authors.initials: I
authors.lastname: Steffen
authors.forename: So-Young
authors.initials: SY
authors.lastname: Choi
authors.forename: Youngwoo
authors.initials: Y
authors.lastname: Park
authors.forename: Heike
authors.initials: H
authors.lastname: Schneider
authors.forename: Klaus
authors.initials: K
authors.lastname: Schughart
authors.forename: Stefan
authors.initials: S
authors.lastname: Pöhlmann
mesh_terms: D056809:Alveolar Epithelial Cells / Q000378:metabolism / Q000821:virology; D001483:Base Sequence; D018938:Caco-2 Cells; D017931:DNA Primers / Q000235:genetics; D055785:Gene Knockdown Techniques; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000502:physiology; D054884:Host-Pathogen Interactions / Q000502:physiology; D006801:Humans; D016676:Macrophages, Alveolar / Q000378:metabolism / Q000821:virology; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D009975:Orthomyxoviridae / Q000472:pathogenicity* / Q000502:physiology; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics / Q000502:physiology*; D012794:Sialic Acids / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism; D014779:Virus Replication / Q000502:physiology
chemical_list: D017931:DNA Primers; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D008565:Membrane Proteins; D012333:RNA, Messenger; D012794:Sialic Acids; D012697:Serine Endopeptidases; C421305:TMPRSS2 protein, human; C528837:TMPRSS4 protein, human; C055645:hepsin; D014357:Trypsin