Identification, Characterization, and Intracellular Distribution of Cofilin in Dictyostelium discoideum

Abstract

We identified and purified an actin monomer-binding protein of apparent molecular weight of 15,000 from Dictyostelium discoideum. The 15-kDa protein depolymerized actin filaments in a pH-dependent manner. The protein also had an activity to decrease apparent viscosity of actin solutions in a dose-dependent manner. This activity was inhibited by phosphatidyl inositides. Molecular cloning of genes encoding this protein revealed that the protein is 42% identical in its primary sequence to yeast cofilin. We concluded that the 15-kDa protein is cofilin of this organism. D. discoideum cells contain two cofilin genes (DCOF1 and DCOF2) whose nucleotide sequences were entirely identical in their exsons while the promoter and intron regions were different. Promoter assay experiments revealed that DCOF1 is expressed both in vegetative and differentiating cells and that DCOF2 is not expressed under any conditions examined. Gene disruption experiments suggested that DCOF1 might be essential for the proliferation of D. discoideum cells whereas the disruption of DCOF2 was proven not to alter any phenotypes. Indirect immunofluorescence microscopic observations showed that cofilin is distributed diffusely throughout cytoplasm in vegetative cells. In flattened cells under starvation stress, cofilin localized at dramatically reorganizing actin-cytoskeletons in ruffling membranes of the leading edge, but not at rigid actin meshwork in focal adhesion plaques. These results suggest that cofilin may be involved in dynamic reorganization of membranous actin cytoskeletons.

Cofilin expression induces cofilin-actin rod formation and disrupts synaptic structure and function in Aplysia synapses

“…3 B and C). It is also possible that cofilin may induce F-actin bundling (34), and this F-actin bundle is subsequently sheared to form rod-like structures. In this aspect, relatively long filament-like structures could be regarded as F-actin bundles induced by cofilin overexpression.…”

Identification and characterization of a low temperature regulated gene encoding an actin‐binding protein from wheat

“…Sequence analysis revealed that Wcor719 encodes a protein with significant homology with ABP. This group of proteins is involved in the regulation of different cellular processes such as cytokinesis, cell locomotion, cytoplasmic streaming and actin assembly in the membrane cytoskeleton, and recently in signal transduction events [3][4][5][6][7]. The high expression of a gene with these characteristics suggests a possible function in regulating the structure of actin filaments during cold acclimation.…”

F-actin and G-actin binding are uncoupled by mutation of conserved tyrosine residues in maize actin depolymerizing factor (ZmADF)

“…Binding to actin is regulated by phosphoinositides (24) and phosphorylation (25)(26)(27). Overexpression of cofilin in mammalian cells caused disruption of pre-existing actin structures and induced cytoplasmic actin bundles (27), whereas overexpression of the endogenous cofilin in Dictyostelium discoideum stimulated cell movement and membrane ruffling (28). Thus, the ADF group of proteins performs a critical role in modulating the dynamics of the actin cytoskeleton.…”

“…The actin depolymerizing factor (ADF) group of proteins, which includes cofilin (11)(12)(13)(14), vertebrate ADF (15) or destrin (16,17), depactin (18), actophorin (19) and, more recently, maize ADF, ZmADF (previously named maize actin binding protein, ZmABP, in refs. 9 and 20) interact with both monomeric and filamentous actin, in vitro, and sever filaments (9,17,(21)(22)(23).…”