The role of E3 in pH protection during alphavirus assembly and exit
Autor(es): Uchime Onyinyechukwu, Fields Whitney, Kielian Margaret
Resumo: Alphaviruses are small enveloped viruses whose surface is covered by spikes composed of trimers of E2/E1 glycoprotein heterodimers. During virus entry, the E2/E1 dimer dissociates within the acidic endosomal environment, freeing the E1 protein to mediate fusion of the viral - endosome membranes. E2 is synthesized as a precursor, p62, which is cleaved by furin in the late secretory pathway to produce mature E2 - a small peripheral glycoprotein, E3. The immature p62/E1 dimer is acid resistant, but since p62 is cleaved before exit from the acidic secretory pathway, low pH-dependent binding of E3 to the spike complex is believed to prevent premature fusion. Based on analysis of the structure of the Chikungunya virus E3/E2/E1 complex, we hypothesized that interactions of E3 residues Y47 - Y48 with E2 are important in this binding. We then directly tested the in vivo role of E3 in pH protection by alanine substitutions of E3 Y47 - Y48 (Y47/48A) in Semliki Forest virus. The mutant was nonviable - was blocked in E1 transport to the plasma membrane - virus production. Although the Y47/48A mutant initially formed the p62/E1 heterodimer, the dimer dissociated during transport through the secretory pathway. Neutralization of the pH in the secretory pathway successfully rescued dimer association, E1 transport, - infectious particle production. Further mutagenesis identified the critical contact as the cation-? interaction of E3 Y47 with E2. Thus, E3 mediates pH protection of E1 during virus biogenesis via interactions strongly dependent on Y47 at the E3-E2 interface.
Imprenta: Journal of Virology, v. 87, n. 18, p. 10255-10262, 2013
Identificador do objeto digital: 10.1128/JVI.01507-13
Descritores: Chikungunya virus - Biosynthesis ; Chikungunya virus - Cell ; Chikungunya virus - DNA ; Chikungunya virus - Molecular structure ; Chikungunya virus - Pathogenesis ; Chikungunya virus - Proteins ; Chikungunya Virus - Virus
Data de publicação: 2013
