Interaction of Actin Filaments with the Plasma Membrane in Amoeba proteus: Studies Using a Cell Model and Isolated Plasma Membrane

Abstract

We prepared a cell model of Amoeba proteus by mechanical bursting to study the interaction between actin filaments (AFs) and plasma membrane (PM). The cell model prepared in the absence of Ca^{2 +} showed remarkable contraction upon addition of ATP. When the model was prepared in the presence of Ca^{2 +}, the cytoplasmic granules formed an aggregate in the central region, having moved away from PM. Although this model showed contraction upon addition of ATP in the presence of Ca²⁺, less contraction was noted. Staining with rhodamine-phalloidin revealed association of AFs with PM in the former model, and a lesser amount of association in the latter model. The interaction between AFs and PM was also studied using the isolated PM. AFs were associated with PM isolated in the absence of Ca²⁺ , but were not when Ca²⁺ was present. These results suggest that the interaction between AFs and PM is regulated by Ca²⁺.