Determinants and Mechanisms of the Low Fusogenicity and High Dependence on Endosomal Entry of Omicron Subvariants.
mBio
; 14(1): e0317622, 2023 02 28.
Artículo
en Inglés
| MEDLINE | ID: covidwho-2193471
ABSTRACT
The rapid spread and strong immune evasion of the SARS-CoV-2 Omicron subvariants has raised serious concerns for the global COVID-19 pandemic. These new variants exhibit generally reduced fusogenicity and increased endosomal entry pathway utilization compared to the ancestral D614G variant, the underlying mechanisms of which remain elusive. Here, we show that the C-terminal S1 mutations of the BA.1.1 subvariant, H655Y and T547K, critically govern the low fusogenicity of Omicron. Notably, H655Y also dictates the enhanced endosome entry pathway utilization. Mechanistically, T547K and H655Y likely stabilize the spike trimer conformation as suggested by increased molecular interactions in structural modeling and enhanced S1 shedding of their reversion mutants K547T and Y655H in viral producer cells. Importantly, the H655Y mutation also determines the low fusogenicity and enhanced dependence on the endosomal entry pathway of other Omicron subvariants, including BA.2, BA.2.12.1, BA.4/5, and BA.2.75. Together, these results uncover mechanisms governing Omicron subvariant entry and provide insights into altered Omicron tissue tropism and pathogenesis. IMPORTANCE Omicron has been shown to predominantly use the endosomal entry pathway, resulting in reduced lung tropism and reduced disease severity; however, the underlying mechanism is not fully understood. In addition, whether the most recent Omicron subvariants, including BA.5 and BA.2.75, use the same pathway as their ancestor for entry is currently not known. In this study, we show that T547K and H655Y mutations in the C terminus of the S1 subunit critically determine the enhanced dependence on the endosomal entry pathway as well as the reduced cell-cell fusion activity of Omicron BA.1, BA.1.1, and other subvariants. Further experiments and molecular modeling suggest that H655Y and K547T stabilize the spike trimer conformation, likely contributing to the decreased fusogenicity and endosomal entry. Our work uncovers novel mechanisms underlying the distinct entry pathway of Omicron subvariants and advances our understanding of their biological characteristics.
Palabras clave
Texto completo:
Disponible
Colección:
Bases de datos internacionales
Base de datos:
MEDLINE
Asunto principal:
COVID-19
Tipo de estudio:
Estudio pronóstico
Tópicos:
Variantes
Límite:
Humanos
Idioma:
Inglés
Revista:
MBio
Año:
2023
Tipo del documento:
Artículo
País de afiliación:
Mbio.03176-22
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