The 55-kD protein is a new actin-bundling protein purified from HeLa cells (Yamashiro-Matsumura, S., and F. Matsumura, 1985, J. Biol. Chem., 260:5087-5097). We have prepared monoclonal antibodies against the 55-kD protein and examined its intracellular localization, as well as its spatial relationships with other components of microfilaments in cultured cells by double-label immunofluorescence. The localization of the 55-kD protein is similar to that of actin. The antibody to the 55-kD protein stained strongly both microspikes and stress fibers. The 55-kD protein was found from the basal portions to the extremities of microspikes while alpha-actinin was localized only in the basal portions. In stress fibers, the 55-kD protein was found rather continuously in comparison to the periodic localizations of alpha-actinin and tropomyosin. Although fimbrin is located in microspikes and ruffling membranes, fimbrin is hardly found in stress fibers unlike the 55-kD protein. These observations coupled with the actin-bundling activity of the 55-kD protein imply that the 55-kD protein is involved in the formation of microfilament bundles in both microspikes and stress fibers.
Intracellular localization of the 55-kD actin-bundling protein in cultured cells: spatial relationships with actin, alpha-actinin, tropomyosin, and fimbrin.
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S Yamashiro-Matsumura, F Matsumura; Intracellular localization of the 55-kD actin-bundling protein in cultured cells: spatial relationships with actin, alpha-actinin, tropomyosin, and fimbrin.. J Cell Biol 1 August 1986; 103 (2): 631–640. doi: https://doi.org/10.1083/jcb.103.2.631
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