title: Phototactic migration of Dictyostelium cells is linked to a new type of gelsolin-related protein.
abstract: The molecular and functional characterization of a 125-kDa Ca2+-extractable protein of the Triton X-100-insoluble fraction of Dictyostelium cells identified a new type of a gelsolin-related molecule. In addition to its five gelsolin segments, this gelsolin-related protein of 125 kDa (GRP125) reveals a number of unique domains, two of which are predicted to form coiled-coil regions. Another distinct attribute of GRP125 concerns the lack of sequence elements known to be essential for characteristic activities of gelsolin-like proteins, i.e. the severing, capping, or nucleation of actin filaments. The subcellular distribution of GRP125 to vesicular compartments suggests an activity of GRP125 different from actin-binding, gelsolin-related proteins. GRP125 expression is tightly regulated and peaks at the transition to the multicellular pseudoplasmodial stage of Dictyostelium development. GRP125 was found indispensable for slug phototaxis, because slugs fail to correctly readjust their orientation in the absence of GRP125. Analysis of the GRP125-deficient mutant showed that GRP125 is required for coupling photodetection to the locomotory machinery of slugs. We propose that GRP125 is essential in the natural environment for the propagation of Dictyostelium spores. We also present evidence for further representatives of the GRP125 type in Dictyostelium, as well as in heterologous cells from lower to higher eukaryotes.
authors.affiliation: Max-Planck-Institute for Biochemistry, D-82152 Martinsried, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Stocker
authors.forename: M
authors.initials: M
authors.lastname: Hiery
authors.forename: G
authors.initials: G
authors.lastname: Marriott
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002451:Cell Compartmentation; D017931:DNA Primers / Q000235:genetics; D004023:Dictyostelium / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D018260:Gelsolin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D008027:Light; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009068:Movement; D009154:Mutation; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D018260:Gelsolin; D015800:Protozoan Proteins; C117419:gelsolin-related protein, 125-kDa