Binding of SARS-CoV-2 protein ORF9b to mitochondrial translocase TOM70 prevents its interaction with chaperone HSP90

Autor(es)

Ayinde, Kehinde S. ; Pinheiro, Glaucia M. S. ; Ramos, Carlos H. I.

• Tipo de documento: Artigo Científico
• Fonte: Biochimie; v. 200, p. 8-pg., 2022-09-01.

Resumo

The emergence of the COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a great threat to global health. ORF9b, an important accessory protein of SARS-CoV-2, plays a critical role in the viral host interaction, targeting TOM70, a member of the mitochondrial translocase of the outer membrane complex. The assembly between ORF9b and TOM70 is implicated in disrupting mitochondrial antiviral signaling, leading to immune evasion. We describe the expression, purification, and characterization of ORF9b alone or coexpressed with the cytosolic domain of human TOM70 in E. coli. ORF9b has 97 residues and was purified as a homodimer with an molecular mass of 22 kDa as determined by SEC-MALS. Circular dichroism experiments showed that Orf9b alone exhibits a random conformation. The ORF9b-TOM70 complex characterized by CD and differential scanning calorimetry showed that the complex is folded and more thermally stable than free TOM70, indicating strong binding. Importantly, proteineprotein interaction assays demonstrated that full-length human Hsp90 is capable of binding to free TOM70 but not to the ORF9b-TOM70 complex. To narrow down the nature of this inhibition, the isolated C-terminal domain of Hsp90 was also tested. These results were used to build a model of the mechanism of inhibition, in which ORF9b efficiently targets two sites of interaction between TOM70 and Hsp90. The findings showed that ORF9b complexed with TOM70 prevents the interaction with Hsp90, and this is one major explanation for SARS-CoV-2 evasion of host innate immunity via the inhibition of the interferon activation pathway. (c) 2022 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved. (AU)

• Processo FAPESP: 17/26131-5 - Chaperoma: estudo da relação entre a estrutura dos seus componentes e a manutenção da proteostase
• Beneficiário: Carlos Henrique Inacio Ramos
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 18/11948-9 - Estudo do mecanismo de interação das co-chaperonas "J-domain proteins" com seus substratos e com a chaperona Hsp70
• Beneficiário: Glaucia Melina Squizato Pinheiro de Castro
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado