Self-assembly of filopodia-like structures on supported lipid bilayers.
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.
Lee
Kwonmoo
K
Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
Gallop
Jennifer L
JL
Rambani
Komal
K
Kirschner
Marc W
MW
D008841:Actin Cytoskeleton / Q000648:ultrastructure; D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008051:Lipid Bilayers; D021962:Membrane Microdomains; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009252:NADPH Dehydrogenase / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011554:Pseudopodia / Q000378:metabolism* / Q000648:ultrastructure*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins / Q000378:metabolism; D000098662:Vasodilator-Stimulated Phosphoprotein
D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; C482527:FNBP1L protein, human; D008051:Lipid Bilayers; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D018129:Phosphatidylinositol Phosphates; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D029867:Xenopus Proteins; D000098662:Vasodilator-Stimulated Phosphoprotein; C020324:fascin; C508552:Dia2 protein, mouse; D009252:NADPH Dehydrogenase