科研之友
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摘要
Following attachment and internalization, mammalian reoviruses undergo intracellular proteolytic disassembly followed by viral penetration into the cytoplasm. The initiating event in reovirus disassembly is the cathepsin-mediated proteolytic degradation of viral outer capsid protein sigma 3. A single tyrosine-to-histidine mutation at amino acid 354 (Y354H) of strain type 3 Dearing (T3D) sigma 3 enhances reovirus disassembly and confers resistance to protease inhibitors such as E64. The sigma 3 amino acid sequence of strain type 3 Abney (T3A) differs from that of T3D at eight positions including Y354H. However, T3A displays disassembly kinetics and protease sensitivity comparable with T3D. We hypothesize that one or more additional sigma 3 polymorphisms suppress the Y354H phenotype and restore T3D disassembly characteristics. To test this hypothesis, we engineered a panel of reovirus variants with T3A sigma 3 polymorphisms introduced individually into T3D-sigma 3Y354H. We evaluated E64 resistance and in vitro cathepsin L susceptibility of these viruses and found that one containing a glycine-to-glutamate substitution at position 198 (G198E) displayed disassembly kinetics and E64 sensitivity similar to those properties of T3A and T3D. Additionally, viruses containing changes at positions 233 and 347 (S233L and I347T) developed de novo compensatory mutations at position 198, strengthening the conclusion that residue 198 is a key determinant of sigma 3 proteolytic susceptibility. Variants with Y354H in sigma 3 lost infectivity more rapidly than T3A or T3D following heat treatment, an effect abrogated by G198E. These results identify a regulatory network of residues that control sigma 3 cleavage and capsid stability, thus providing insight into the regulation of nonenveloped virus disassembly.
- 出版日期2012-3-9
