TMPRSS12 Is an Activating Protease for Subtype B Avian Metapneumovirus
Bingling Yun1, Yao Zhang1, Yongzhen Liu1
1Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Nan Gang District, Harbin, Heilongjiang Province, People's Republic of China.
Abstract:
The entry of avian metapneumovirus (aMPV) into host cells initially requires the fusion of viral and cell membranes, which is exclusively mediated by fusion (F) protein. Proteolysis of aMPV F protein by endogenous proteases of host cells allows F protein to induce membrane fusion; however, these proteases have not been identified. Here, we provide the first evidence that the transmembrane serine protease TMPRSS12 facilitates the cleavage of subtype B aMPV (aMPV/B) F protein. We found that overexpression of TMPRSS12 enhanced aMPV/B F protein cleavage, F protein fusogenicity, and viral replication. Subsequently, knockdown of TMPRSS12 with specific small interfering RNAs (siRNAs) reduced aMPV/B F protein cleavage, F protein fusogenicity, and viral replication. We also found a cleavage motif in the aMPV/B F protein (amino acids 100 and 101) that was recognized by TMPRSS12. The histidine, aspartic acid, and serine residue (HDS) triad of TMPRSS12 was shown to be essential for the proteolysis of aMPV/B F protein via mutation analysis. Notably, we observed TMPRSS12 mRNA expression in target organs of aMPV/B in chickens. Overall, our results indicate that TMPRSS12 is crucial for aMPV/B F protein proteolysis and aMPV/B infectivity and that TMPRSS12 may serve as a target for novel therapeutics and prophylactics for aMPV.
Importance:
Proteolysis of the aMPV F protein is a prerequisite for F protein-mediated membrane fusion of virus and cell and for aMPV infection; however, the proteases used in vitro and vivo are not clear. A combination of analyses, including overexpression, knockdown, and mutation methods, demonstrated that the transmembrane serine protease TMPRSS12 facilitated cleavage of subtype B aMPV (aMPV/B) F protein. Importantly, we located the motif in the aMPV/B F protein recognized by TMPRSS12 and the catalytic triad in TMPRSS12 that facilitated proteolysis of the aMPV/B F protein. This is the first report on TMPRSS12 as a protease for proteolysis of viral envelope glycoproteins. Our study will shed light on the mechanism of proteolysis of aMPV F protein and pathogenesis of aMPV.
Insights
The transmembrane serine protease TMPRSS12 is crucial for avian metapneumovirus (aMPV) infection by cleaving the viral fusion (F) protein. Targeting TMPRSS12 could lead to new treatments for aMPV.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- Avian metapneumovirus (aMPV) entry into host cells requires fusion mediated by its F protein.
- Proteolysis of the aMPV F protein is essential for membrane fusion and viral infection.
- The specific host proteases responsible for aMPV F protein cleavage remain unidentified.
Purpose of the Study:
- To identify the host protease responsible for avian metapneumovirus subtype B (aMPV/B) F protein cleavage.
- To elucidate the mechanism by which this protease facilitates aMPV/B infection.
- To explore the potential of this protease as a therapeutic target for aMPV.
Main Methods:
- Overexpression and knockdown (using small interfering RNAs - siRNAs) of the transmembrane serine protease TMPRSS12 in host cells.
- Analysis of aMPV/B F protein cleavage, fusogenicity, and viral replication under varying TMPRSS12 levels.
- Site-directed mutagenesis to identify the cleavage motif in aMPV/B F protein and the catalytic triad in TMPRSS12.
Main Results:
- TMPRSS12 was identified as the host protease that cleaves the aMPV/B F protein.
- Overexpression of TMPRSS12 enhanced F protein cleavage, fusogenicity, and viral replication, while knockdown reduced these processes.
- A specific cleavage motif (amino acids 100-101) on the aMPV/B F protein and the catalytic HDS triad of TMPRSS12 were essential for proteolysis.
Conclusions:
- TMPRSS12 plays a critical role in aMPV/B F protein processing and subsequent viral infectivity.
- TMPRSS12 is the first reported viral protease for viral envelope glycoproteins.
- TMPRSS12 represents a promising target for developing novel therapeutics and prophylactics against aMPV infections.
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