CSM News Electronic Edition Volume 3, number 6 August 18, 1994 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to CSM-News@worms.cmsbio.nwu.edu. Back issues of CSM-News, the CSM Reference database and other useful information is available by anonymous ftp from worms.cmsbio.nwu.edu [165.124.233.50], via Gopher at the same address, or by World Wide Web through www.nwu.edu. This is the final CSM-News issue prior to the San Diego Dicty Meeting. See you all in San Diego! =========== Abstracts =========== PATHWAYS FOR DIF-1 METABOLISM AND THEIR REGULATION ARE CONSERVED BETWEEN CLOSELY RELATED DICTYOSTELIUM SPECIES, BUT NOT BETWEEN DISTANT MEMBERS OF THE FAMILY. Saskia van Es (1), Steve Hodgkinson (2), Pauline Schaap (1) and Robert R. Kay (2) (1) Cell Biology Unit, Institute of Molecular Plant Sciences, University of Leiden, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands. (2) Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, UK. Differentiation, in press ABSTRACT There is suggestive evidence that a conserved signalling system involving the Differentiation Inducing Factor (DIF-1) controls stalk cell differentiation in a variety of slime mould species. In the standard laboratory species, Dictyostelium discoideum, DIF-1 is inactivated first by dechlorination catalysed by DIF-1 dechlorinase, followed by several hydroxylation events, so that eventually about 12 metabolites are produced. If DIF-1 is used as a signal molecule in other species, it seems essential that they too should be able to metabolize it. We report here that the essentials of DIF-1 metabolism are conserved in D. mucoroides, the closest relative to D. discoideum; both the dechlorinase and hydroxylase enzymes are present in D. mucoroides, and living cells of both species produce a similar spectrum of metabolites from [3H]DIF-1. Furthermore, DIF-1 dechlorinase can be induced by DIF-1, as in D. discoideum, and this induction is repressed by ammonia and cAMP. DIF-1 dechlorinase could not be detected in cell extracts from D. minutum or Polysphondylium violaceum. However, living cells of both species are able to metabolize DIF-1; P. violaceum seems to produce a small amount of the mono-dechlorinated compound, DIF-3, but all other metabolites from both species appear to be unique. Thus all investigated species can metabolize DIF-1, but the exact route of metabolism is not highly conserved. -------------------------------------------------------------------- Dictyostelium amoebae that lack G-actin sequestering profilins show defects in F-actin content, cytokinesis and development Michael Haugwitz, Angelika A. Noegel, Jacques Karakesisoglou and Michael Schleicher Institute for Cell Biology, L.M.-University of Munich, Schillerstr. 42, 80336 Muenchen and Max-Planck-Institute for Biochemistry, Am Klopferspitz 18a, 82152 Martinsried, Fed. Rep. of Germany CELL, in press. To study in vivo functions of the ubiquitous actin-binding protein profilin we generated by anti-sense and gene disruption techniques Dictyostelium mutants that lack one or both of the profilin isoforms pI and pII. Whereas the single mutants (pI- or pII-m inus) showed an essentially unchanged phenotype as compared to wild-type cells, the behaviour of the double mutant (pI/II-minus) was drastically altered: Motility was significantly reduced, single cells were up to 10-times larger than wild-type cells and showed a broad rim of F-actin below the plasma membrane, the F-actin concentration was increased by about 60-70%, and development was blocked prior to fruiting body formation. Furthermore, double mutants could not be grown in shaking culture under normal conditions reflecting an impaired cytokinesis. The aberrant phenotype could be rescued by re-introducing a functional profilin I or profilin II gene. Current models describe the in vitro function of profilin as promoting actin polymerization by nucleation or as inhibiting it by sequestration. The data in this study suggest that profilin functions in Dictyostelium amoebae primarily as an actin sequestering protein. ---------------------------------------------------------------------- [End CSM-News, volume 3, number 6]