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.
Domain analysis of supervillin, an F-actin bundling plasma membrane protein with functional nuclear localization signals
J.D. Wulfkuhle, I.E. Donina, N.H. Stark, R.K. Pope, K.N. Pestonjamasp, M.L. Niswonger, E.J. Luna; Domain analysis of supervillin, an F-actin bundling plasma membrane protein with functional nuclear localization signals. J Cell Sci 1 July 1999; 112 (13): 2125–2136. doi: https://doi.org/10.1242/jcs.112.13.2125
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