Organization of pp60src and selected cytoskeletal proteins within adhesion plaques and junctions of Rous sarcoma virus-transformed rat cells.

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Abstract
The localization of pp60src within adhesion structures of epithelioid rat kidney cells transformed by the Schmidt-Ruppin strain of Rous sarcoma virus was compared to the organization of actin, .alpha.-actinin, vinculin (a 130,000-dalton protein), tubulin and the 58,000-dalton intermediate filament protein. The adhesion structures included both adhesion plaques and previously uncharacterized adhesive regions formed at cell-cell junctions. These later structures were named adhesion junctions. Both adhesion plaques and adhesion junctions were identified by interference-reflection microscopy and compared to the location of pp60src and the various cytoskeletal proteins by double fluorescene. The src gene product was found within both adhesion plaques and adhesion junctions. Actin, .alpha.-actinin and vinculin were also localized within the same pp60src-containing adhesion structures. Tubulin and the 58,000-dalton intermediate filament protein were not associated with either adhesion plaques or adhesion junctions. Both adhesion plaques and adhesion junctions were isolated as substratum-bound structures and characterized by scanning electron microscopy. Immunofluorescence revealed that pp60src, actin, .alpha.-actinin and vinculin were organized within specific regions of the adhesion junctions. Heavy accumulations of actin and .alpha.-actinin were found on both sides of the junctions with a narrow gap of unstained material at the midline; the pp60src stain was more intense in this central region. Antibody to vinculin stained double narrow lines defining the periphery of the junctional complexes but was excluded from the intervening region. The distribution of vinculin relative to pp60src within adhesion plaques suggested an inverse relationship between the presence of these 2 proteins. Overall, these results establish a close link between the src gene product and components of the cytoskeleton and implicate the adhesion plaques and adhesion junctions in the mechanism of Rous sarcoma virus-induced tranformation.