title: Cross-inhibition of chikungunya virus fusion and infection by alphavirus E1 domain III proteins.
abstract: Alphaviruses are small enveloped RNA viruses that include important emerging human pathogens, such as chikungunya virus (CHIKV). These viruses infect cells via a low-pH-triggered membrane fusion reaction, making this step a potential target for antiviral therapies. The E1 fusion protein inserts into the target membrane, trimerizes, and refolds to a hairpin-like conformation in which the combination of E1 domain III (DIII) and the stem region (DIII-stem) pack against a core trimer composed of E1 domains I and II (DI/II). Addition of exogenous DIII proteins from Semliki Forest virus (SFV) has been shown to inhibit E1 hairpin formation and SFV fusion and infection. Here we produced and characterized DIII and DI/II proteins from CHIKV and SFV. Unlike SFV DIII, both core trimer binding and fusion inhibition by CHIKV DIII required the stem region. CHIKV DIII-stem and SFV DIII-stem showed efficient cross-inhibition of SFV, Sindbis virus, and CHIKV infections. We developed a fluorescence anisotropy-based assay for the binding of SFV DIII-stem to the core trimer and used it to demonstrate the relatively high affinity of this interaction (Kd [dissociation constant], ∼85 nM) and the importance of the stem region. Together, our results support the conserved nature of the key contacts of DIII-stem in the alphavirus E1 homotrimer and describe a sensitive and quantitative in vitro assay for this step in fusion protein refolding.
authors: Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA.
authors: Claudia
authors: C
authors: Sánchez-San Martín
authors: Soumya
authors: S
authors: Nanda
authors: Yan
authors: Y
authors: Zheng
authors: Whitney
authors: W
authors: Fields
authors: Margaret
authors: M
authors: Kielian
mesh_terms: D018354:Alphavirus Infections / Q000503:physiopathology*; D000818:Animals; D002460:Cell Line; D002646:Chikungunya virus / Q000378:metabolism* / Q000502:physiology; D006224:Cricetinae; D004330:Drosophila; D005454:Fluorescence Polarization; D006801:Humans; D008081:Liposomes / Q000378:metabolism; D011485:Protein Binding; D012672:Semliki forest virus / Q000378:metabolism* / Q000502:physiology; D012845:Sindbis Virus / Q000502:physiology; D014759:Viral Envelope Proteins / Q000378:metabolism*; D014760:Viral Fusion Proteins / Q000378:metabolism*; D053585:Virus Attachment
chemical_list: D008081:Liposomes; D014759:Viral Envelope Proteins; D014760:Viral Fusion Proteins
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