Structural insights into VLDLR recognition by western equine encephalitis virus.

Area of Science:

• Virology
• Structural Biology
• Molecular Biology

Background:

• Western equine encephalitis virus (WEEV) causes severe neurological disease in humans and equids.
• Historically, WEEV utilized the very-low-density lipoprotein receptor (VLDLR) for cell entry, but current strains have altered receptor tropism.

Purpose of the Study:

• To elucidate the structural basis of WEEV interaction with VLDLR.
• To identify specific VLDLR domains involved in WEEV binding.
• To understand the molecular determinants of WEEV receptor usage shifts.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine complex structures of WEEV with VLDLR fragments.
• Biochemical assays to assess binding affinities between WEEV and VLDLR concatemers.
• Site-directed mutagenesis to investigate the role of E2 glycoprotein polymorphisms in WEEV entry.

Main Results:

• Identified direct interactions between WEEV and specific VLDLR domains (LA1, LA2, LA3, LA5).
• Cryo-EM revealed LA1 and LA2 binding within a cleft of the WEEV spike protein, while LA3 and LA5 interact with the E1 protein's DIII region.
• The VLDLR LA1-5 concatemer showed the highest binding affinity for WEEV.
• A single polymorphism in the WEEV E2 glycoprotein was found to determine receptor tropism, with specific mutations enhancing VLDLR-mediated entry.

Conclusions:

• Detailed structural insights into WEEV-VLDLR interactions.
• Understanding of how viral glycoproteins mediate receptor binding and entry.
• Identification of key viral determinants for receptor tropism shifts.
• Provides a foundation for developing targeted antiviral therapies against WEEV and related alphaviruses.