Abstract
Filopodia are finger-like protrusive structures, containing actin bundles. By incubating frog egg extracts with supported lipid bilayers containing phosphatidylinositol 4,5 bisphosphate, we have reconstituted the assembly of filopodia-like structures (FLSs). The actin assembles into parallel bundles, and known filopodial components localize to the tip and shaft. The filopodia tip complexes self-organize--they are not templated by preexisting membrane microdomains. The F-BAR domain protein toca-1 recruits N-WASP, followed by the Arp2/3 complex and actin. Elongation proteins, Diaphanous-related formin, VASP, and fascin are recruited subsequently. Although the Arp2/3 complex is required for FLS initiation, it is not essential for elongation, which involves formins. We propose that filopodia form via clustering of Arp2/3 complex activators, self-assembly of filopodial tip complexes on the membrane, and outgrowth of actin bundles.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Actin Cytoskeleton / ultrastructure
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Actin-Related Protein 2-3 Complex / metabolism
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Actins / metabolism*
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Animals
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Carrier Proteins / metabolism
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Cell Adhesion Molecules / metabolism
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Cell Membrane / metabolism
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Humans
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Kinetics
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Lipid Bilayers*
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Membrane Microdomains
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Mice
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Microfilament Proteins / metabolism
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Microtubule-Associated Proteins / metabolism
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NADPH Dehydrogenase / metabolism
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Phosphatidylinositol Phosphates / metabolism
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Phosphoproteins / metabolism
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Pseudopodia / metabolism*
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Pseudopodia / ultrastructure*
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Recombinant Fusion Proteins / metabolism
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Signal Transduction
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Vasodilator-Stimulated Phosphoprotein
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Wiskott-Aldrich Syndrome Protein, Neuronal / metabolism
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Xenopus
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Xenopus Proteins / metabolism
Substances
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Actin-Related Protein 2-3 Complex
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Actins
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Carrier Proteins
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Cell Adhesion Molecules
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FNBP1L protein, human
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Lipid Bilayers
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Microfilament Proteins
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Microtubule-Associated Proteins
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Phosphatidylinositol Phosphates
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Phosphoproteins
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Recombinant Fusion Proteins
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Wiskott-Aldrich Syndrome Protein, Neuronal
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Xenopus Proteins
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Vasodilator-Stimulated Phosphoprotein
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fascin
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Dia2 protein, mouse
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NADPH Dehydrogenase