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How tropomyosin regulates lamellipodial actin‐based motility: a combined biochemical and reconstituted motility approach
Author(s) -
Bugyi Beáta,
Didry Dominique,
Carlier MarieFrance
Publication year - 2010
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2009.316
Subject(s) - tropomyosin , microbiology and biotechnology , lamellipodium , pseudopodia , cofilin , actin , mdia1 , motility , biology , protein filament , actin cytoskeleton , chemistry , biophysics , cell migration , cytoskeleton , biochemistry , cell
At the leading edge of migrating cells, protrusive forces are developed by the assembly of actin filaments organised in a lamellipodial dendritic array at the front and a more distal lamellar linear array. Whether these two arrays are distinct or functionally linked and how they contribute to cell migration is an open issue. Tropomyosin severely inhibits lamellipodium formation and facilitates the lamellar array while enhancing migration, by a mechanism that is not understood. Here we show that the complex in vivo effects of tropomyosin are recapitulated in the reconstituted propulsion of neural Wiskott–Aldrich syndrome protein (N‐WASP)‐functionalised beads, which is based on the sole formation of a dendritic array of actin‐related protein (Arp)2/3‐branched filaments. Actin‐depolymerising factor (ADF) and tropomyosin control the length of the actin tail. By competing with Arp2/3 during filament branching, tropomyosin displays opposite effects on propulsion depending on the surface density of N‐WASP. Tropomyosin binding to the dendritic array is facilitated following filament debranching, causing its enrichment at the rear of the actin tail, like in vivo . These results unveil the mechanism by which tropomyosin generates two morphologically and dynamically segregated actin networks from a single one.