Structural determinants of rotavirus proteolytic activation.

Area of Science:

• Virology
• Structural Biology
• Molecular Mechanisms of Infection

Background:

• Rotavirus (RV) is a major cause of severe childhood diarrhea.
• RV infectivity depends on the proteolysis of its VP4 spike protein by host proteases.
• The precise structural basis for VP4 activation by proteolysis remains unclear.

Purpose of the Study:

• To elucidate the structural mechanism by which VP4 proteolysis by trypsin-like proteases activates rotavirus for cell entry.
• To understand the role of structural constraints in regulating VP4 activation.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to visualize uncleaved and cleaved RV virions.
• Advanced image processing techniques were utilized to analyze structural differences.

Main Results:

• The non-proteolyzed VP4 spike protein's conformation is restricted by surrounding loops.
• These loops link the spike head's lectin domains to its body.
• Proteolysis removes these loops, releasing the structural constraint and allowing conformational changes necessary for membrane penetration.

Conclusions:

• The identified loops act as regulatory elements for VP4 activation.
• Proteolysis precisely times and localizes VP4 activation for efficient rotavirus infection.
• This mechanism ensures viral activation occurs only within the host intestinal lumen.