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Crystal structure of inhibitor-bound human MSPL that can activate high pathogenic avian influenza
Ayako Ohno1, Nobuo Maita2, Takanori Tabata3
1Department of Nutritional Physiology, Institute of Medical Nutrition, Tokushima University Graduate School, Tokushima, Japan.
Abstract:
Infection of certain influenza viruses is triggered when its HA is cleaved by host cell proteases such as proprotein convertases and type II transmembrane serine proteases (TTSP). HA with a monobasic motif is cleaved by trypsin-like proteases, including TMPRSS2 and HAT, whereas the multibasic motif found in high pathogenicity avian influenza HA is cleaved by furin, PC5/6, or MSPL. MSPL belongs to the TMPRSS family and preferentially cleaves [R/K]-K-K-R↓ sequences. Here, we solved the crystal structure of the extracellular region of human MSPL in complex with an irreversible substrate-analog inhibitor. The structure revealed three domains clustered around the C-terminal α-helix of the SPD. The inhibitor structure and its putative model show that the P1-Arg inserts into the S1 pocket, whereas the P2-Lys and P4-Arg interacts with the Asp/Glu-rich 99-loop that is unique to MSPL. Based on the structure of MSPL, we also constructed a homology model of TMPRSS2, which is essential for the activation of the SARS-CoV-2 spike protein and infection. The model may provide the structural insight for the drug development for COVID-19.
Insights
We determined the crystal structure of human MSPL, a protease crucial for influenza virus entry. This reveals unique interactions and provides a model for TMPRSS2, aiding COVID-19 drug development.
Area of Science:
- Biochemistry
- Structural Biology
- Virology
Background:
- Influenza virus hemagglutinin (HA) cleavage by host proteases like TMPRSS family members is essential for viral infection.
- Different HA motifs are cleaved by specific proteases, including TMPRSS2, HAT, furin, PC5/6, and MSPL.
- MSPL, a TMPRSS family protease, cleaves specific multibasic sequences in high-pathogenicity avian influenza HA.
Purpose of the Study:
- To elucidate the structural basis of MSPL protease activity.
- To understand the molecular interactions of MSPL with its inhibitors.
- To provide a structural model for TMPRSS2 for potential drug development against SARS-CoV-2.
Main Methods:
- X-ray crystallography was used to determine the structure of the extracellular region of human MSPL in complex with an inhibitor.
- Substrate-analog inhibitor design and synthesis.
- Homology modeling of TMPRSS2 based on the MSPL structure.
Main Results:
- The crystal structure of human MSPL revealed three domains associated with its C-terminal α-helix.
- The inhibitor binds to MSPL, with key interactions involving the P1-Arg in the S1 pocket and P2-Lys/P4-Arg with the unique 99-loop.
- A homology model of TMPRSS2 was constructed, offering insights into its interaction with the SARS-CoV-2 spike protein.
Conclusions:
- The MSPL structure provides detailed insights into its substrate-binding mechanism, particularly the role of the unique 99-loop.
- The MSPL-inhibitor complex structure can guide the design of novel protease inhibitors.
- The TMPRSS2 homology model may facilitate the development of therapeutics targeting SARS-CoV-2 entry.
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