A Direct Interaction between Actin and Vimentin Filaments Mediated by the Tail Domain of Vimentin*
- ‡Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218, the §Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, and the ¶Howard Hughes Medical Institute graduate training program and Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, Maryland 21218
- 1 To whom correspondence should be addressed: Dept. of Chemical and Biomolecular Engineering, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218. Tel.: 410-516-7006; Fax: 410-516-5510; E-mail: wirtz{at}jhu.edu.
Abstract
The assembly and organization of the three major eukaryotic cytoskeleton proteins, actin, microtubules, and intermediate filaments, are highly interdependent. Through evolution, cells have developed specialized multifunctional proteins that mediate the cross-linking of these cytoskeleton filament networks. Here we test the hypothesis that two of these filamentous proteins, F-actin and vimentin filament, can interact directly, i.e. in the absence of auxiliary proteins. Through quantitative rheological studies, we find that a mixture of vimentin/actin filament network features a significantly higher stiffness than that of networks containing only actin filaments or only vimentin filaments. Maximum inter-filament interaction occurs at a vimentin/actin molar ratio of 3 to 1. Mixed networks of actin and tailless vimentin filaments show low mechanical stiffness and much weaker inter-filament interactions. Together with the fact that cells featuring prominent vimentin and actin networks are much stiffer than their counterparts lacking an organized actin or vimentin network, these results suggest that actin and vimentin filaments can interact directly through the tail domain of vimentin and that these inter-filament interactions may contribute to the overall mechanical integrity of cells and mediate cytoskeletal cross-talk.
Footnotes
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↵2 The abbreviations used are: F-actin, filamentous actin; IF, intermediate filament; FL, full-length; ΔT, tailless; EM, electron microscopy.
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↵* This work was funded by NASA Grant NAG9-1563, National Institutes of Health Grant GM075305, and the Howard Hughes Medical Institute. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. S1.
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- Received June 7, 2006.
- Revision received August 7, 2006.
- The American Society for Biochemistry and Molecular Biology, Inc.
