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Different localizations and cellular behaviors of leiomodin and tropomodulin in mature cardiomyocyte sarcomeres.

Authors: Skwarek-Maruszewska, A  Boczkowska, M  Zajac, AL  Kremneva, E  Svitkina, T  Dominguez, R  Lappalainen, P 
Citation: Skwarek-Maruszewska A, etal., Mol Biol Cell. 2010 Oct 1;21(19):3352-61. doi: 10.1091/mbc.E10-02-0109. Epub 2010 Aug 4.
Pubmed: (View Article at PubMed) PMID:20685966
DOI: Full-text: DOI:10.1091/mbc.E10-02-0109

Leiomodin (Lmod) is a muscle-specific F-actin-nucleating protein that is related to the F-actin pointed-end-capping protein tropomodulin (Tmod). However, Lmod contains a unique approximately 150-residue C-terminal extension that is required for its strong nucleating activity. Overexpression or depletion of Lmod compromises sarcomere organization, but the mechanism by which Lmod contributes to myofibril assembly is not well understood. We show that Tmod and Lmod localize through fundamentally different mechanisms to the pointed ends of two distinct subsets of actin filaments in myofibrils. Tmod localizes to two narrow bands immediately adjacent to M-lines, whereas Lmod displays dynamic localization to two broader bands, which are generally more separated from M-lines. Lmod's localization and F-actin nucleation activity are enhanced by interaction with tropomyosin. Unlike Tmod, the myofibril localization of Lmod depends on sustained muscle contraction and actin polymerization. We further show that Lmod expression correlates with the maturation of myofibrils in cultured cardiomyocytes and that it associates with sarcomeres only in differentiated myofibrils. Collectively, the data suggest that Lmod contributes to the final organization and maintenance of sarcomere architecture by promoting tropomyosin-dependent actin filament nucleation.

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RGD ID: 11344944
Created: 2016-07-09
Species: All species
Last Modified: 2016-07-09
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.