Dynamics of the cytoskeleton in Amoeba proteus. III. Influence of microinjected antibodies on the organization and function of the microfilament system.

Affinity-purified antibodies against actin, myosin, alpha-actinin and vinculin cross-reacted with corresponding proteins from Amoeba proteus in immunoblotting experiments. Antibody staining of cells fixed during locomotion revealed different distribution patterns with a local concentration of anti-actin in the intermediate and of anti-myosin in the uroid region. Anti-alpha-actinin labeled a thin layer at the internal face of the plasma membrane, whereas anti-vinculin was distinctly concentrated at the base of advancing pseudopodia. Microinjection of different control solutions or antibodies against actin, myosin and alpha-actinin neither influenced the normal morphology and motile activity of amoebae nor changed the cellular distribution pattern of complementary antigens. However, antibodies against vinculin disorganized controlled locomotion and altered the spatial morphology of the microfilament system as well as the localization of the vinculin antigen thus pointing to a function of this protein in adhesion and locomotion of A. proteus. The results of the present paper show similarities to observations on mammalian tissue culture cells.