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Human alpha-synemin interacts directly with vinculin and metavinculin
Ning Sun1, David R Critchley, Denise Paulin
1Muscle Biology Group, Department of Biochemistry, Biophysics and Molecular Biology and of Animal Science, Iowa State University, Ames, IA 50011-3260, USA.
The Biochemical Journal
|November 22, 2007
Summary
Alpha-synemin, a variant of the intermediate filament protein synemin, directly binds vinculin and metavinculin. This interaction links muscle intermediate filaments to cell adhesion junctions like costameres.
Area of Science:
- Cell Biology
- Muscle Physiology
- Protein Interactions
Background:
- Synemin is a large intermediate filament (IF) protein found in muscle cells.
- Synemin associates with desmin and vimentin to form heteropolymeric IFs.
- Human synemin exists as alpha- and beta-splice variants, with alpha-synemin possessing an additional SNTIII domain.
Purpose of the Study:
- To investigate the functional differences between alpha- and beta-synemin splice variants.
- To determine if the SNTIII domain of alpha-synemin interacts with vinculin and metavinculin.
- To elucidate the role of alpha-synemin in linking IFs to cellular adhesion structures.
Main Methods:
- In vitro protein-protein interaction assays.
- In vivo co-immunoprecipitation assays.
- Transient expression and co-localization studies in mammalian cells.
Main Results:
- The SNTIII domain of alpha-synemin directly interacts with both vinculin and metavinculin in vitro.
- SNTIII interacts with vinculin in vivo, an interaction enhanced by PtdIns(4,5)P(2).
- Alpha-synemin, via SNTIII, co-localizes with vinculin in focal adhesions, unlike beta-synemin.
Conclusions:
- Alpha-synemin, but not beta-synemin, binds vinculin and metavinculin.
- This interaction facilitates the connection of heteropolymeric IFs to muscle adhesion junctions, such as costameres.
- The SNTIII domain is crucial for alpha-synemin's role in muscle cell structure and function.
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