Phg2, a Kinase Involved in Adhesion and Focal Site Modeling inDictyostelium

Abstract

The amoeba Dictyostelium is a simple genetic system for analyzing substrate adhesion, motility and phagocytosis. A new adhesion-defective mutant named phg2 was isolated in this system, and PHG2 encodes a novel serine/threonine kinase with a ras-binding domain. We compared the phenotype of phg2 null cells to other previously isolated adhesion mutants to evaluate the specific role of each gene product. Phg1, Phg2, myosin VII, and talin all play similar roles in cellular adhesion. Like myosin VII and talin, Phg2 also is involved in the organization of the actin cytoskeleton. In addition, phg2 mutant cells have defects in the organization of the actin cytoskeleton at the cell-substrate interface, and in cell motility. Because these last two defects are not seen in phg1, myoVII, or talin mutants, this suggests a specific role for Phg2 in the control of local actin polymerization/depolymerization. This study establishes a functional hierarchy in the roles of Phg1, Phg2, myosinVII, and talin in cellular adhesion, actin cytoskeleton organization, and motility.

Dictyostelium ACAP-A is an ArfGAP involved in cytokinesis, cell migration and actin cytoskeleton dynamics

“…Instead, ACAP-A-GFP appeared still mainly in the cytosol and slightly enriched in pericentrosomal regions in some cells. Like in mammalian cells, in Dictyostelium cytokinesis is dependent on the remodeling of the actin cytoskeleton, and many mutants with altered actin cytoskeleton exhibit cytokinesis defects (Gebbie et al, 2004). Our observations suggest that, like ACAP proteins in mammalian cells, ACAP-A may be specifically required to regulate the organization of the actin cytoskeleton.…”

“…Incubation of Dictyostelium cells in phosphate buffer induces numerous thin filopodial extensions, which are not observed in some mutants defective in genes controlling actin cytoskeleton remodeling (Gebbie et al, 2004). In this condition, acapA 2 cells formed filopodia that were short (87% filopodia #2 mm) in comparison to those observed in WT cells (83% filopodia .2 mm) (Fig.…”

Calcium mobilization stimulatesDictyostelium discoideumshear-flow-induced cell motility

“…(1) Heterotrimeric G proteins are essential for cAMP and folic acid signal transduction but are dispensable for mechanosensitivity. (2) The phg2 kinase is required for vegetative cell explorative or shearflow-induced motility but not during multicellular development, hence for cAMP chemotaxis (Gebbie et al, 2004).…”

Selective membrane exclusion in phagocytic and macropinocytic cups

“…All Dictyostelium cells used in this study were derived from the subclone DH1-10 (Cornillon et al, 2000) of the DH1 strain (Caterina et al, 1994). The 1 (Lefkir et al, 2003) and myoVII (Gebbie et al, 2004) knockout strains have been described previously. The myoK (Schwarz et al, 2000) knockout cells were a gift from T. Soldati (University of Geneva, Switzerland).…”