Metavinculin Tunes the Flexibility and the Architecture of Vinculin-Induced Bundles of Actin Filaments.
Metavinculin Tunes the Flexibility and the Architecture of Vinculin-Induced Bundles of Actin Filaments.
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DOI：
10.1016/j.jmb.2015.07.005
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发表时间：
2015-08-28
影响因子：
5.6
通讯作者：
Quinlan ME
中科院分区：
文献类型：
--
作者：
Oztug Durer ZA;McGillivary RM;Kang H;Elam WA;Vizcarra CL;Hanein D;De La Cruz EM;Reisler E;Quinlan ME
Vinculin is an abundant protein found at cell-cell and cell-extracellular matrix junctions. In muscles, a longer splice-isoform of vinculin, metavinculin, is also expressed. The metavinculin-specific insert is part of the C-terminal tail domain, the actin-binding site of both isoforms. Mutations in the metavinculin-specific insert are linked to heart disease such as dilated cardiomyopathies. Vinculin tail domain (VT) both binds and bundles actin filaments. Metavinculin tail domain (MVT) binds actin filaments in a similar orientation but does not bundle filaments. Recently, MVT was reported to sever actin filaments. In this work, we asked how MVT influences F-actin alone or in combination with VT. Cosedimentation and limited proteolysis experiments indicated a similar actin binding affinity and mode for both VT and MVT. In real time TIRF microscopy experiments MVT’s severing activity was negligible. Instead, we found that MVT binding caused a two-fold reduction in F-actin’s bending persistence length and increased susceptibility to breakage. Perhaps MVT allows the load of muscle contraction to act as a signal to reorganize actin filaments. Using mutagenesis and site-directed labeling with fluorescence probes, we determined that MVT alters actin interprotomer contacts and dynamics, which presumably reflect the observed changes in bending persistence length. Finally, we found that MVT decreases the density and thickness of actin filament bundles generated by VT. Altogether, our data suggest that MVT alters actin filament flexibility and tunes filament organization in the presence of VT. Both of these activities are potentially important for muscle cell function.
