Characterization and fine-structural localization of actin- and fibronectin-like proteins in planaria (Dugesia lugubris s.l.).

Actin- and fibronectin-like proteins were characterized in the planarian, Dugesia lugubris s.l., by sodium dodecyl sulphate polyacrylamide gel electrophoresis and immunoblotting analysis using antisera to vertebrate actin and fibronectin. These antisera recognized protein bands of 42 kDa and 220 kDa, respectively. In addition, the immunohistochemical distribution of both actin- and fibronectin-like material was examined by using immuno-electron microscopy. Actin-like protein was localized in myofibrils in various differentiation stages, and in the peripheral cytoplasm and lamellipodia of cells that were migrating. The fibronectin-like component was associated with the extracellular matrix in the fibrillar structures and with the surface of the migrating cells. Our data suggest that similar cellular and molecular mechanisms are involved in cell-matrix interactions and in the morphogenesis of living organisms at different evolutionary levels.