Department of Cell Biology
Actins; Animals; Base Sequence; Binding Sites; COS Cells; Cattle; Cell Adhesion; Cell Line; Cytoskeleton; DNA Primers; Gene Expression; Green Fluorescent Proteins; Lamins; Luminescent Proteins; Membrane Proteins; Microfilament Proteins; Nuclear Localization Signals; Nuclear Proteins; Phenotype; Recombinant Fusion Proteins; Vinculin
Cell Biology | Life Sciences | Medicine and Health Sciences
A growing number of actin-associated membrane proteins have been implicated in motile processes, adhesive interactions, and signal transduction to the cell nucleus. We report here that supervillin, an F-actin binding protein originally isolated from bovine neutrophil plasma membranes, contains functional nuclear targeting signals and localizes at or near vinculin-containing focal adhesion plaques in COS7-2 and CV1 cells. Overexpression of full-length supervillin in these cells disrupts the integrity of focal adhesion plaques and results in increased levels of F-actin and vinculin. Localization studies of chimeric proteins containing supervillin sequences fused with the enhanced green fluorescent protein indicate that: (1) the amino terminus promotes F-actin binding, targeting to focal adhesions, and limited nuclear localization; (2) the dominant nuclear targeting signal is in the center of the protein; and (3) the carboxy-terminal villin/gelsolin homology domain of supervillin does not, by itself, bind tightly to the actin cytoskeleton in vivo. Overexpression of chimeras containing both the amino-terminal F-actin binding site(s) and the dominant nuclear targeting signal results in the formation of large nuclear bundles containing F-actin, supervillin, and lamin. These results suggest that supervillin may contribute to cytoarchitecture in the nucleus, as well as at the plasma membrane.
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Citation: J Cell Sci. 1999 Jul;112 ( Pt 13):2125-36. Link to article on publisher's website