title: Filamin-regulated F-actin assembly is essential for morphogenesis and controls phototaxis in Dictyostelium.
abstract: Dictyostelium strains lacking the F-actin cross-linking protein filamin (ddFLN) have a severe phototaxis defect at the multicellular slug stage. Filamins are rod-shaped homodimers that cross-link the actin cytoskeleton into highly viscous, orthogonal networks. Each monomer chain of filamin is comprised of an F-actin-binding domain and a rod domain. In rescue experiments only intact filamin re-established correct phototaxis in filamin minus mutants, whereas C-terminally truncated filamin proteins that had lost the dimerization domain and molecules lacking internal repeats but retaining the dimerization domain did not rescue the phototaxis defect. Deletion of individual rod repeats also changed their subcellular localization, and mutant filamins in general were less enriched at the cell cortex as compared with the full-length protein and were increasingly present in the cytoplasm. For correct phototaxis ddFLN is only required at the tip of the slug because expression under control of the cell type-specific extracellular-matrix protein A (ecmA) promoter and mixing experiments with wild type cells supported phototactic orientation. Likewise, in chimeric slugs wild type cells were primarily found at the tip of the slug, which acts as an organizer in Dictyostelium morphogenesis.
authors.affiliation: Institut für Biochemie I, Zentrum Molekulare Medizin Köln, Medizinische Fakultät, Universität zu Köln, 50931 Köln, Germany.
authors.forename: Nandkumar
authors.initials: N
authors.lastname: Khaire
authors.forename: Rolf
authors.initials: R
authors.lastname: Müller
authors.forename: Rosemarie
authors.initials: R
authors.lastname: Blau-Wasser
authors.forename: Ludwig
authors.initials: L
authors.lastname: Eichinger
authors.forename: Michael
authors.initials: M
authors.lastname: Schleicher
authors.forename: Matthias
authors.initials: M
authors.lastname: Rief
authors.forename: Tad A
authors.initials: TA
authors.lastname: Holak
authors.forename: Angelika A
authors.initials: AA
authors.lastname: Noegel
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D003285:Contractile Proteins / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004023:Dictyostelium / Q000378:metabolism*; D019281:Dimerization; D005109:Extracellular Matrix / Q000378:metabolism; D064448:Filamins; D017353:Gene Deletion; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008027:Light; D008840:Microfilament Proteins / Q000378:metabolism*; D009154:Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D000199:Actins; D003285:Contractile Proteins; D064448:Filamins; D008840:Microfilament Proteins; D049452:Green Fluorescent Proteins