Ultrastructural cytoskeleton alterations and modification of actin expression in the NIH/3T3 cell line after transformation with Ha-ras-activated oncogene. |
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Authors: | L Lombardi D Ballinari I Bongarzone M Migliari P Mondellini C Traversari S Modina |
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Institution: | Division of Experimental Oncology A, University of Milan, Italy. |
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Abstract: | Cytoskeleton alterations of NIH/3T3 fibroblast monolayers transfected with Ha-ras-activated oncogene were studied by immunofluorescence, immunoelectron microscopy, and immunoelectrophoretic analysis of actin isoforms. Transformation foci were found to consist of cells with a round shape and rare stress fibers that spread sparsely, forming rare focal contacts and fibronexuses. The loss of stress fibers in transformed cells was confirmed by staining with rhodamine-phalloidin and with a fluorescinated anti-non-muscle cell actin antibody. The transformed cells were anchored to the substrate prominently by filaments that contained fibronectin, as showed by immunoelectron microscopy. A down-regulation of alpha-actin isoform was observed by immunofluorescence and immunoblotting analysis using a specific monoclonal antibody. The diffuse distribution of alpha-actin, lacking a specific association with stress fibers, challenges the hypothesis of a connection between alpha-actin down-regulation and stress fiber loss. |
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