Tropomyosin isoform 3 promotes the formation of filopodia by regulating the recruitment of actin-binding proteins to actin filaments

Tropomyosins are believed to function in part by stabilizing actin filaments. However, accumulating evidence suggests that fundamental differences in function exist between tropomyosin isoforms, which contributes to the formation of functionally distinct filament populations. We investigated the fun...

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Bibliographic Details
Published in:Experimental cell research 2011-02, Vol.317 (3), p.249-261
Main Authors: Creed, Sarah J., Desouza, Melissa, Bamburg, James R., Gunning, Peter, Stehn, Justine
Format: Article
Language:English
Subjects:
Actin
Actin Cytoskeleton - metabolism
Actins - metabolism
Animals
Cell Line
Cellular biology
Fascin
Filopodia
Gene expression
Humans
Isoform
Microfilament Proteins - metabolism
Molecular biology
Molecular weight
Protein Isoforms
Protein Transport
Proteins
Pseudopodia - metabolism
Rats
Tropomyosin
Tropomyosin - genetics
Tropomyosin - physiology
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Summary:Tropomyosins are believed to function in part by stabilizing actin filaments. However, accumulating evidence suggests that fundamental differences in function exist between tropomyosin isoforms, which contributes to the formation of functionally distinct filament populations. We investigated the functions of the high-molecular-weight isoform Tm3 and examined the molecular properties of Tm3-containing actin filament populations. Overexpression of the Tm3 isoform specifically induced the formation of filopodia and changes in actin solubility. We observed alterations in actin-binding protein recruitment to filaments, co-incident with changes in expression levels, which can account for this functional outcome. Tm3-associated filaments recruit active actin depolymerizing factor and are bundled into filopodia by fascin, which is both up-regulated and preferentially associated with Tm3-containing filaments in the Tm3 overexpressing cells. This study provides further insight into the isoform-specific roles of different tropomyosin isoforms. We conclude that variation in the tropomyosin isoform composition of microfilaments provides a mechanism to generate functionally distinct filament populations.
ISSN:0014-4827
1090-2422
DOI:10.1016/j.yexcr.2010.10.019