RESUMO
Dictyostelium discoideum harbors a short (CRN12) and a long coronin (CRN7) composed of one and two beta-propellers, respectively. They are primarily present in the cell cortex and cells lacking CRN12 (corAâ») or CRN7 (corBâ») have defects in actin driven processes. We compared the characteristics of a mutant cell line (corAâ»/corBâ») lacking CRN12 and CRN7 with the single mutants focusing on cytokinesis, phagocytosis, chemotaxis and development. Cytokinesis, uptake of small particles, and developmental defects were not enhanced in the corAâ»/corBâ» strain as compared to the single mutants, whereas motility and phagocytosis of yeast particles were more severely impaired. It appears that although both proteins affect the same processes they do not act in a redundant manner. Rather, they often act antagonistically, which is in accordance with their proposed roles in the actin cytoskeleton where CRN12 acts in actin disassembly whereas CRN7 stabilizes actin filaments and protects them from disassembly.
Assuntos
Actinas , Citoesqueleto , Dictyostelium/metabolismo , Proteínas dos Microfilamentos , Actinas/metabolismo , Animais , Quimiotaxia/fisiologia , Citocinese/fisiologia , Citoesqueleto/metabolismo , Dictyostelium/crescimento & desenvolvimento , Dictyostelium/ultraestrutura , Escherichia coli , Deleção de Genes , Legionella pneumophila , Proteínas dos Microfilamentos/genética , Proteínas dos Microfilamentos/metabolismo , Fagocitose/fisiologia , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Saccharomyces cerevisiae , TransfecçãoRESUMO
Dictyostelium discoideum Coronin7 (DdCRN7) together with human Coronin7 (CRN7) and Pod-1 of Drosophila melanogaster and Caenorhabditis elegans belong to the coronin family of WD-repeat domain-containing proteins. Coronin7 proteins are characterized by two WD-repeat domains that presumably fold into two beta-propeller structures. DdCRN7 shares highest homology with human CRN7, a protein with roles in membrane trafficking. DdCRN7 is present in the cytosol and accumulates in cell surface projections during movement and phago- and pinocytosis. Cells lacking CRN7 have altered chemotaxis and phagocytosis. Furthermore, loss of CRN7 affects the infection process by the pathogen Legionella pneumophila and allows a more efficient internalization of bacteria. To provide a mechanism for CNR7 action, we studied actin-related aspects. We could show that CRN7 binds directly to F-actin and protects actin filaments from depolymerization. CRN7 also associated with F-actin in vivo. It was present in the Triton X-100-insoluble cytoskeleton, colocalized with F-actin, and its distribution was sensitive to drugs affecting the actin cytoskeleton. We propose that the CRN7 role in chemotaxis and phagocytosis is through its effect on the actin cytoskeleton.
Assuntos
Actinas/química , Dictyostelium/metabolismo , Proteínas dos Microfilamentos/química , Adesão Celular , Movimento Celular , Quimiotaxia , AMP Cíclico/metabolismo , Citoesqueleto/metabolismo , Glutationa Transferase/metabolismo , Humanos , Legionella pneumophila/metabolismo , Modelos Biológicos , Mutação , Fagocitose , Pinocitose , Estrutura Terciária de ProteínaRESUMO
Coronins are highly conserved among species, but their function is far from being understood in detail. Here we will introduce members of the family of coronin like proteins from Drosophila melanogaster, Caenorhabditis elegans and the social amoeba Dictyostelium discoideum. Genetic data from D. discoideum and D. melanogaster revealed that coronins in general are important regulators of many actin-dependent processes.
