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Membrane-induced bundling of actin filaments.

ABSTRACT: Dynamic interplay between the plasma membrane and underlying cytoskeleton is essential for cellular shape change. Spatial organization of actin filaments, whose growth generates membrane deformations during motility 1, phagocytosis 2, endocytosis 3, and cytokinesis 4, is mediated by specific protein-protein interactions that branch, crosslink, and bundle filaments into networks that interact with the membrane. Although membrane curvature has been found to influence binding of proteins with curvature-sensitive domains 5, the direct effect of membrane elasticity on cytoskeletal network organization is not clear. Here we show through in vitro reconstitution and elastic modeling that a lipid bilayer can drive the emergence of bundled actin filament protrusions from branched actin filament networks, thus playing a role normally attributed to actin-binding proteins. Formation of these filopodium-like protrusions with only a minimal set of purified proteins points to an active participation of the membrane in organizing actin filaments at the plasma membrane. In this way, elastic interactions between the membrane and cytoskeleton can cooperate with accessory proteins to drive cellular shape change.

SUBMITTER: Liu AP

PROVIDER: S-EPMC2739388 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Membrane-induced bundling of actin filaments.

Liu Allen P AP Richmond David L DL Maibaum Lutz L Pronk Sander S Geissler Phillip L PL Fletcher Daniel A DA

Nature physics 20080801

Dynamic interplay between the plasma membrane and underlying cytoskeleton is essential for cellular shape change. Spatial organization of actin filaments, whose growth generates membrane deformations during motility 1, phagocytosis 2, endocytosis 3, and cytokinesis 4, is mediated by specific protein-protein interactions that branch, crosslink, and bundle filaments into networks that interact with the membrane. Although membrane curvature has been found to influence binding of proteins with curva ...[more]

PMID: 19746192

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Project description:Targeted deletion of mXinalpha results in cardiac hypertrophy and cardiomyopathy with conduction defects (Gustafson-Wagner, E., Sinn, H. W., Chen, Y.-L., Wang, D.-Z., Reiter, R. S., Lin, J. L.-C., Yang, B., Williamson, R. A., Chen, J. N., Lin, C.-I., and Lin, J. J.-C. (2007) Am. J. Physiol. 293, H2680-H2692). To understand the underlying mechanisms leading to such cardiac defects, the functional domains of mXinalpha and its interacting proteins were investigated. Interaction studies using co-immunoprecipitation, pull-down, and yeast two-hybrid assays revealed that mXinalpha directly interacts with beta-catenin. The beta-catenin-binding site on mXinalpha was mapped to amino acids 535-636, which overlaps with the known actin-binding domains composed of the Xin repeats. The overlapping nature of these domains provides insight into the molecular mechanism for mXinalpha localization and function. Purified recombinant glutathione S-transferase- or His-tagged mXinalpha proteins are capable of binding and bundling actin filaments, as determined by co-sedimentation and electron microscopic studies. The binding to actin was saturated at an approximate stoichiometry of nine actin monomers to one mXinalpha. A stronger interaction was observed between mXinalpha C-terminal deletion and actin as compared with the interaction between full-length mXinalpha and actin. Furthermore, force expression of green fluorescent protein fused to an mXinalpha C-terminal deletion in cultured cells showed greater stress fiber localization compared with force-expressed GFP-mXinalpha. These results suggest a model whereby the C terminus of mXinalpha may prevent the full-length molecule from binding to actin, until the beta-catenin-binding domain is occupied by beta-catenin. The binding of mXinalpha to beta-catenin at the adherens junction would then facilitate actin binding. In support of this model, we found that the actin binding and bundling activity of mXinalpha was enhanced in the presence of beta-catenin.

Dataset Information

Membrane-induced bundling of actin filaments.

Publications

Membrane-induced bundling of actin filaments.

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