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J Mol Biol. 2015 Aug 28;427(17):2782-98. doi: 10.1016/j.jmb.2015.07.005. Epub 2015 Jul 10.

Metavinculin Tunes the Flexibility and the Architecture of Vinculin-Induced Bundles of Actin Filaments.

Author information

1
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095-1569, USA.
2
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA.
3
Bioinformatics and Structural Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA.
4
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095-1569, USA; Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095-1570, USA.
5
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095-1569, USA; Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095-1570, USA. Electronic address: margot@chem.ucla.edu.

Abstract

Vinculin is an abundant protein found at cell-cell and cell-extracellular matrix junctions. In muscles, a longer splice isoform of vinculin, metavinculin, is also expressed. The metavinculin-specific insert is part of the C-terminal tail domain, the actin-binding site of both isoforms. Mutations in the metavinculin-specific insert are linked to heart disease such as dilated cardiomyopathies. Vinculin tail domain (VT) both binds and bundles actin filaments. Metavinculin tail domain (MVT) binds actin filaments in a similar orientation but does not bundle filaments. Recently, MVT was reported to sever actin filaments. In this work, we asked how MVT influences F-actin alone or in combination with VT. Cosedimentation and limited proteolysis experiments indicated a similar actin binding affinity and mode for both VT and MVT. In real-time total internal reflection fluorescence microscopy experiments, MVT's severing activity was negligible. Instead, we found that MVT binding caused a 2-fold reduction in F-actin's bending persistence length and increased susceptibility to breakage. Using mutagenesis and site-directed labeling with fluorescence probes, we determined that MVT alters actin interprotomer contacts and dynamics, which presumably reflect the observed changes in bending persistence length. Finally, we found that MVT decreases the density and thickness of actin filament bundles generated by VT. Altogether, our data suggest that MVT alters actin filament flexibility and tunes filament organization in the presence of VT. Both of these activities are potentially important for muscle cell function. Perhaps MVT allows the load of muscle contraction to act as a signal to reorganize actin filaments.

KEYWORDS:

actin; adhesion; metavinculin; severing; vinculin

PMID:
26168869
PMCID:
PMC4540644
DOI:
10.1016/j.jmb.2015.07.005
[Indexed for MEDLINE]
Free PMC Article

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