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Distribution and substrate specificity of intracellular proteolytic processing enzyme(s) for paramyxovirus fusion
N Kawahara1, X Z Yang, T Sakaguchi
1Department of Bacteriology, Hiroshima University School of Medicine, Japan.
Abstract:
Intracellular proteolytic processing of fusion glycoprotein precursors (F0) of paramyxoviruses, i.e. a virulent strain of Newcastle disease virus (NDV), parainfluenza virus type 3 (PIV3) and simian virus 5 (SV5), was examined in NALM6 and BSC40 cells and compared with that in LLCMK2 cells to investigate the distribution of the virus-activating protease(s) among the cells and its substrate specificity. BSC40 cells lack a processing endoprotease of the neuropeptide precursor, pro-opiomelanocortin (POMC), which possesses multiple cleavage sites at pairs of basic residues, Lys-Arg and Arg-Arg, a motif similar to that found in the cleavage site of the F0 proteins. In NALM6 cells, only small amounts of the F0 protein of virulent NDV was cleaved whereas those of PIV3 and SV5 were efficiently cleaved. In BSC40 cells the F0 proteins of these three viruses were cleaved normally as well as in LLCMK2 cells. The processing inhibitors monensin, chloroquine and A23187 suppressed the F0 cleavage in the three cell types. These results indicate that both NALM6 and BSC40 cells possess virus-activating proteases similar to that of LLCMK2 cells, but suggest that the enzyme of NALM6 may be slightly different in its substrate specificity from those of BSC40 and LLCMK2. The results also suggest that the virus-activating proteases are different in their distribution and substrate specificity from the processing enzyme of POMC.
Insights
This study investigated paramyxovirus fusion glycoprotein (F0) processing in different cell lines. Results show cell-specific differences in protease activity and substrate specificity, impacting viral activation.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Paramyxoviruses require intracellular proteolytic cleavage of their fusion glycoprotein precursors (F0) for infectivity.
- The distribution and substrate specificity of the proteases responsible for F0 cleavage are not fully understood.
- Pro-opiomelanocortin (POMC) processing shares cleavage site motifs with F0 proteins, offering a comparative model.
Purpose of the Study:
- To investigate the cellular distribution and substrate specificity of virus-activating proteases involved in paramyxovirus F0 processing.
- To compare F0 processing in NALM6 and BSC40 cells with LLCMK2 cells, examining differences in protease activity.
Main Methods:
- Examined intracellular proteolytic processing of fusion glycoprotein precursors (F0) from Newcastle disease virus (NDV), parainfluenza virus type 3 (PIV3), and simian virus 5 (SV5).
- Utilized NALM6, BSC40, and LLCMK2 cell lines for comparative analysis of F0 cleavage.
- Employed processing inhibitors (monensin, chloroquine, A23187) to assess the role of cellular processing pathways.
Main Results:
- NALM6 cells showed efficient cleavage of PIV3 and SV5 F0 but limited cleavage of virulent NDV F0.
- BSC40 and LLCMK2 cells efficiently cleaved F0 proteins from all three viruses, indicating the presence of similar virus-activating proteases.
- Processing inhibitors significantly suppressed F0 cleavage across all tested cell types.
Conclusions:
- NALM6 and BSC40 cells possess virus-activating proteases comparable to LLCMK2 cells, but NALM6 proteases exhibit slightly different substrate specificity.
- The distribution and substrate specificity of virus-activating proteases differ from the processing enzyme of POMC.
- Cellular context influences the efficiency and specificity of paramyxovirus F0 processing.