Disease relevance of COF1

• We also demonstrate that cofilin interacts with the large cytoplasmic domains of the alpha1, alpha2 and alpha3 isoforms of Na,K-ATPase, but not with those of glucose transporter 1, glucose transporter 4, cystic fibrosis transmembrane conductance regulator and plasma membrane Ca-ATPase [1].

High impact information on COF1

• Cofilin promotes rapid actin filament turnover in vivo [2].
• On the basis of similar results obtained by DAip1 overexpression and effects of latrunculin-A treatment, we propose a function for DAip1 in the control of actin depolymerization in vivo, probably through interaction with cofilin [3].
• The Ala120-equivalent mutation in yeast cofilin affected cell growth, whereas that of the Phe82-equivalent had no effect in yeast [4].
• Side chain hydroxyl groups of Ser119, Ser120 and Tyr82 in cofilin form hydrogen bonds with main chain carbonyl moieties from the helix, causing the kink [4].
• However, fluid phase endocytosis is defective in act1-159 strains. act1-159 is synthetically lethal with cofilin and profilin mutants, supporting the conclusion that mutations in all of these genes impair the polymerization/ depolymerization cycle [5].

Biological context of COF1

• A complete disruption of the COF1 gene was created in diploid cells [6].
• Several temperature sensitive (ts-) mutants were independently created by the random mutagenesis of COF1 with hydroxylamine [7].
• Gene disruption and tetrad analysis showed that gene COF1 is essential for yeast cell growth [8].
• Isolation of a yeast essential gene, COF1, that encodes a homologue of mammalian cofilin, a low-M(r) actin-binding and depolymerizing protein [8].
• A gene on a multicopy plasmid which suppresses the ts-phenotype of cof1-101, a typical ts-cofilin mutant, was isolated [7].

Anatomical context of COF1

• Cofilin is an essential component of the yeast cortical cytoskeleton [6].
• RESULTS: A proteolytic study of phosphorylated porcine cofilin and expression of a mutated cofilin in cultured cells revealed that Ser-3 is the unique phosphorylation site [9].
• To this end, we constructed a hybrid protein targeting cofilin, an actin depolymerizing protein, to late endosomes [10].
• 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 [11].
• Cofilin reduced FRET from tryptophan residues to 4-azido-2-nitrophenyl-putrescine (ANP) at Gln41 in skeletal muscle F-but not in G-actin [12].

Associations of COF1 with chemical compounds

• RESULTS: When COF1 was over-expressed in yeast cells under the GAL1 promoter in a medium containing galactose as a sole carbon source, the cells did not survive [7].
• The NH2-terminal 16kD of Abp1p, a 65-kD yeast protein identified by its ability to bind to actin filaments, is 23% identical to yeast cofilin [6].
• S3D-cofilin, in which Ser-3 was replaced with Asp, did not bind in vitro to actin while S3A-cofilin did [9].
• To facilitate the imaging of actin filaments and to avoid the use of rhodamine phalloidin, which competes with cofilin, alpha-actin was labeled with tetramethylrhodamine cadaverine (TRC) at Gln41 [13].
• However, following the interprotomer cross-linking of Gln41 to Cys374 in F-actin by ANP, cofilin binding did not change FRET from the tryptophan residues to ANP [12].

Physical interactions of COF1

• Through systematic mutagenesis of Aip1 surfaces, we identify two well-separated F-actin-binding sites, one of which contributes to actin filament binding and disassembly specifically in the presence of cofilin [14].

Regulatory relationships of COF1

• Aip1 and cofilin promote rapid turnover of yeast actin patches and cables: a coordinated mechanism for severing and capping filaments [14].

Other interactions of COF1

• In this study, we demonstrate using viscosity, sedimentation, and actin assembly rate assays that yeast cofilin (16 kD) possesses all of these properties [6].
• Thus, cofilin and Abp1p are structurally related but functionally distinct components of the yeast membrane cytoskeleton [6].
• Here, we analyze the in vivo function of a ubiquitous actin-interacting protein, Aip1, suggested to work with cofilin [14].
• In agreement with these observations, we found that like the Arp2/3 complex and the myosins-I, cofilin was essential for the endocytic uptake in vivo, whereas profilin was dispensable [15].
• S3D-porcine cofilin did not complement the lethality associated with delta cof1 mutations in Saccharomyces cerevisiae while wild-type and S3A-cofilin did [9].

Analytical, diagnostic and therapeutic context of COF1

• Immunofluorescence experiments showed that, like Abp1p, cofilin is associated with the membrane actin cytoskeleton [6].
• Indirect immunofluorescence microscopic observations showed that cofilin is distributed diffusely throughout cytoplasm in vegetative cells [11].
• Molecular cloning of genes encoding this protein revealed that the protein is 42% identical in its primary sequence to yeast cofilin [11].
• Mapping the G-actin binding surface of cofilin using synchrotron protein footprinting [16].
• These results are generally consistent with, and complementary to, the results of previous site-directed mutagenesis studies and extend our understanding of the G-actin binding surface of cofilin [16].

References