Cardiomyopathy Mutations in Metavinculin Disrupt Regulation of Vinculin-Induced F-Actin Assemblies |
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| Institution: | 1. Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA;2. Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY 10065, USA;3. Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY 10025, USA;4. Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA;1. University of New South Wales (UNSW), Kensington, NSW 2052, Australia;2. Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia;1. VIB-VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium;2. Structural Biology Brussels, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium;3. Department of Computer Science, Purdue University, West Lafayette, IN 47907, USA;4. Department of Biological Sciences, Purdue University, Hockmeyer Structural Biology Building, 249 S. Martin Jischke Dr West Lafayette, IN 47907, USA;5. Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudosok korutja 2, 1117 Budapest, Hungary;1. First Department of Cardiology, Medical School, National and Kapodistrian, University of Athens, Athens, Greece;2. Department of Computer Science and Engineering, University of Ioannina, Ioannina, Greece;1. MTA-DE Laboratory of Protein Dynamics, Department of Biochemistry and Molecular Biology, University of Debrecen, Debrecen, Hungary;2. Department of Organic Chemistry, University of Debrecen, Debrecen, Hungary;3. Department of Biochemistry, University of Cambridge, UK;1. Laboratory for Muscle Plasticity, Department of Orthopedics, University of Zurich, Balgrist Campus, Zurich, Switzerland;2. Department of Orthopedic Surgery, Balgrist University Hospital, Zurich, Switzerland |
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| Abstract: | Debilitating heart conditions, notably dilated and hypertrophic cardiomyopathies (CMs), are associated with point mutations in metavinculin, a larger isoform of the essential cytoskeletal protein vinculin. Metavinculin is co-expressed with vinculin at sub-stoichiometric ratios in cardiac tissues. CM mutations in the metavinculin tail domain (MVt) occur within the extra 68-residue insert that differentiates it from the vinculin tail domain (Vt). Vt binds actin filaments (F-actin) and promotes vinculin dimerization to bundle F-actin into thick fibers. While MVt binds to F-actin in a similar manner to Vt, MVt is incapable of F-actin bundling and inhibits Vt-mediated F-actin bundling. We performed F-actin co-sedimentation and negative-stain EM experiments to dissect the coordinated roles of metavinculin and vinculin in actin fiber assembly and the effects of three known metavinculin CM mutations. These CM mutants were found to weakly induce the formation of disordered F-actin assemblies. Notably, they fail to inhibit Vt-mediated F-actin bundling and instead promote formation of large assemblies embedded with linear bundles. Computational models of MVt bound to F-actin suggest that MVt undergoes a conformational change licensing the formation of a protruding sub-domain incorporating the insert, which sterically prevents dimerization and bundling of F-actin by Vt. Sub-domain formation is destabilized by CM mutations, disrupting this inhibitory mechanism. These findings provide new mechanistic insights into the ability of metavinculin to tune actin organization by vinculin and suggest that dysregulation of this process by CM mutants could underlie their malfunction in disease. |
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