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Keywords:

  • Amoeba proteus;
  • F-actin organization;
  • cell adhesion;
  • cell nucleus

Abstract

Adhesion and movement ofAmoeba proteusare both dependent on the appropriate arrangement of the F-actin cytoskeleton and on the presence of the cell nucleus. In this study the F-actin organization was examined by routine FITC-phalloidin staining and confocal laser microscopy in intact amoebae and in their nucleated and anucleated fragments, at different levels of cell adherence to the substratum. In the adhering and migrating intact cells and nucleated cell fragments dot-like aggregates of F-actin are scattered over the ventral side at sites close to the substratum. In the case of de-adhesion of nucleated specimens this pattern disappears and F-actin is accumulated in the cell centre and/or dispersed in the cytoplasm. The same actin distribution, without ventral dots, is found in the anucleated fragments which usually fail to attach to the substratum. Re-adhesion of anucleated fragments, induced by a modified substratum or spontaneous, is accompanied by restoration of actin dots at the lower cell side. It is concluded that: (1) adhering specimens ofA. proteusdisplay the same dot-like actin pattern on the ventral cell side, as many metazoan motile cells; (2) organization or disorganization of this pattern may occur independently of the presence of the cell nucleus, under the control of cell adhesion to the substratum.