ADHESION-DEPENDENT F-ACTIN PATTERN IN AMEBA-PROTEUS AS A COMMON FEATURE OF AMEBAS AND THE METAZOAN MOTILE CELLS

Adhesion and movement of Amoeba proteus are both dependent on the appr opriate 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 dif ferent levels of cell adherence to the substratum. In the adhering and migrating intact cells and nucleated cell fragments dot-like aggregat es of F-actin are scattered over the ventral side at sites close to th e substratum. In the case of de-adhesion of nucleated specimens this p attern disappears and F-actin is accumulated in the cell centre and/or dispersed in the cytoplasm. The same actin distribution, without vent ral dots, is found in the anucleated fragments which usually fail to a ttach 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) adher ing specimens of A. proteous display the same dot-like actin pattern o n the ventral cell side? as many metazoan motile cells; (2) organizati on or disorganization of this pattern may occur independently of the p resence of the cell nucleus, under the control of cell adhesion to the substratum. (C) 1997 Academic Press Limited.