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A crescent-shaped ALIX dimer targets ESCRT-III CHMP4 filaments
Ricardo Pires1, Bettina Hartlieb, Luca Signor
1Unit of Virus Host Cell Interactions (UVHCI) UMI 3265, Université Joseph Fourier-EMBL-CNRS, 6 rue Jules Horowitz, 38042 Grenoble, Cedex 9, France.
Structure (London, England : 1993)
|June 16, 2009
Summary
Dimeric ALIX, a protein involved in membrane remodeling, functions as the active scaffolding form. This dimer interacts with ESCRT-III CHMP4 polymers, impacting viral budding and cellular processes.
Area of Science:
- Molecular and Cell Biology
- Structural Biology
- Virology
Background:
- ALIX protein is crucial for membrane remodeling in processes like viral budding and cytokinesis.
- ALIX interacts with ESCRT-III CHMP4, a key component in these cellular events.
Purpose of the Study:
- To investigate the role of ALIX dimerization in its function.
- To determine the structural basis of ALIX dimerization and its interaction with CHMP4.
Main Methods:
- Small-angle X-ray scattering (SAXS) for structural analysis.
- Site-directed mutagenesis to study dimerization interfaces.
- In vivo coexpression studies.
- In vitro filament formation assays.
Main Results:
- ALIX dimerizes in solution and in vivo, adopting an elongated crescent shape.
- Mutations disrupting dimerization lead to monomeric conformations.
- Dimeric ALIX colocalizes with CHMP4B and influences HIV-1 budding.
- ALIX bridges CHMP4 filaments, suggesting a scaffolding role.
Conclusions:
- Dimeric ALIX is the active form, essential for recruiting and organizing ESCRT-III CHMP4 polymers.
- ALIX dimerization is critical for its function in membrane remodeling and viral egress.
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