Novel type II transmembrane serine proteases, MSPL and TMPRSS13, Proteolytically activate membrane fusion activity of the hemagglutinin of highly pathogenic avian influenza viruses and induce their multicycle replication.
Host cellular proteases induce influenza virus entry into cells by cleaving the viral surface envelope glycoprotein hemagglutinin (HA). However, details on the cellular proteases involved in this event are not fully available. We report here that ubiquitous type II transmembrane serine proteases, MSPL and its splice variant TMPRSS13, are novel candidates for proteases processing HA proteins of highly pathogenic avian influenza (HPAI) viruses, apart from the previously identified furin and proprotein convertases 5 and 6. HAs from all HPAI virus H5 and H7 strains have one of two cleavage site motifs, the R-X-K/R-R motif with R at position P4 and the K-K/R-K/T-R motif with K at position P4. In studies of synthetic 14-residue HPAI virus HA peptides with these cleavage site motifs, furin preferentially cleaved only HA peptides with the R-K-K-R motif in the presence of calcium and not peptides with the other motif, whereas MSPL and TMPRSS13 cleaved both types of HA peptides (those with the R/K-K-K-R motif) efficiently in the absence of calcium. Full-length recombinant HPAI virus HA with the K-K-K-R cleavage motif exhibited poor susceptibility to cleavage in the absence of MSPL or TMPRSS13 and the presence of furin in infected cells, but it was converted to mature HA subunits in transfected cells expressing MSPL or TMPRSS13, with membrane-fused giant-cell formation. This conversion and membrane fusion were suppressed by inhibitors of MSPL and TMPRSS13. Furthermore, infection with and multiplication of genetically modified live HPAI virus A/Crow/Kyoto/53/2004 (H5N1) with the K-K-K-R cleavage site motif were detected only in MSPL- and TMPRSS13-expressing cells.
Okumura
Yuushi
Y
Division of Enzyme Chemistry, Institute for Enzyme Research, The University of Tokushima, Kuramoto-cho 3-18-15, Tokushima 770-8503, Japan.
Takahashi
Etsuhisa
E
Yano
Mihiro
M
Ohuchi
Masanobu
M
Daidoji
Tomo
T
Nakaya
Takaaki
T
Böttcher
Eva
E
Garten
Wolfgang
W
Klenk
Hans-Dieter
HD
Kido
Hiroshi
H
D002460:Cell Line; D006389:Hemagglutinins, Viral / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D006801:Humans; D009980:Influenza A virus / Q000472:pathogenicity / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism*; D053586:Virus Internalization; D014779:Virus Replication
D006389:Hemagglutinins, Viral; D008565:Membrane Proteins; C458881:hemagglutinin fusogenic peptide, influenza virus; D012697:Serine Endopeptidases; C429035:TMPRSS13 protein, human