Dicty News Electronic Edition Volume 19, number 6 August 31, 2002 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu. Back issues of Dicty-News, the Dicty Reference database and other useful information is available at DictyBase--http://dictybase.org. ============= Abstracts ============= The evolution of development in the cellular slime molds. John Bonner Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08540, USA Evolution and Development, in press. How might the successive stages in the life cycle of Dictyostelium discoideum have evolved? It has been estimated that cellular slime molds must have come into being something in the order of a billion years ago and during this vast span of time have evolved into the complex forms we find today. First I will compare the various stages of the D. discoideum life cycle with other forms that exist today, whose mature state corresponds to one of the earlier stages of the development of D. discoideum. This is a component of my larger argument that each stage of D. discoideum development is adaptive. Those simpler forms would not exist today if they were not competing successfully in their natural environment. Finally, I discuss the possible evolutionary sequence of the steps in the development of D. discoideum. ----------------------------------------------------------------------------- Receptor-Dependent and Tyrosine Phosphatase-Mediated Inhibition of GSK3 Regulates Cell Fate Choice Leung Kim 1, Adrian Harwood 2, and Alan R. Kimmel 1,3 1 Laboratory of Cellular and Developmental Biology (Bldg. 50/3351), NIDDK National Institutes of Health, Bethesda, MD 20892-8028, USA 2 MRC Laboratory for Molecular Cell Biology & Dept of Biology, University College London, London, WCIE 6BT, UK Developmental Cell, On Press Summary Asymmetric body axis formation is central to metazoan development. Dictyostelium establishes an anterior/posterior axis utilizing 7-TM cAMP morphogen receptors (CARs) and GSK3-mediated signal transductions that has a parallel with metazoan Wnt/Frizzled-GSK3 pathways. In Dictyostelium, GSK3 promotes posterior cell patterning but inhibits anterior cell differentiation. Tyrosine kinase ZAK1 mediates GSK3 activation. We now show that CAR4 regulates a tyrosine phosphatase that inhibits GSK3 activity. We have also identified essential phospho-tyrosines in GSK3, confirmed their role in activated/de-activated regulation and cell fate decisions, and relate them to the predicted 3D-structure of GSK3b. CARs differentially regulate GSK3 activity by selectively activating a tyrosine phosphatase or kinase for pattern formation. The findings may provide a comparative understanding of CAR-GSK3 and Wnt/Frizzled-GSK3 pathways. ----------------------------------------------------------------------------- Loss of the F-actin binding and vesicle associated protein comitin leads to a phagocytosis defect Thomas Schreiner1), Martina R. Mohrs1), Rosemarie Blau-Wasser1), Alfred von Krempelhuber2), Michael Steinert3), Michael Schleicher4) and Angelika A. Noegel 1) * 1) Center for Biochemistry, Medical Faculty, University of Cologne, 50931 Koeln, Germany, 2) Max-Planck-Institut fuer Biochemie, 82152 Martinsried, Germany, 3) Institut fr Molekulare Infektionsbiologie, Universitt Wrzburg, 97070 Wuerzburg, Germany, 4) Institut fr Zellbiologie, Ludwig-Maximilians- Universitaet, 80336 Muenchen, Germany Eukaryotic Cell Abstract Comitin is an F-actin binding and membrane associated protein from Dictyostelium which is present on Golgi and vesicle membranes and changes its localization in response to agents affecting the cytoskeleton. To investigate its in vivo functions we have generated knock out mutants by gene replacement. Based on comitin's in vitro functions we examined properties related to vesicular transport and microfilament function. Whereas cell growth, pinocytosis, secretion, chemotaxis, motility and development were unaltered, comitin minus cells were impaired in the early steps of phagocytosis of yeast particles and of E. coli, whereas uptake of latex beads was unaffected. Furthermore, the lack of comitin positively affected survival of pathogenic bacteria. Mutant cells also showed an altered response to hyperosmotic shock in comparison to wild type. The redistribution of comitin during hyperosmotic shock in wild type cells and its presence on early phagosomes suggest a direct involvement of comitin in these processes. ----------------------------------------------------------------------------- Functions of LIM proteins in cell polarity and chemotactic motility Bharat Khurana*+1, Taruna Khurana*+2, Nandkumar Khaire and Angelika A. Noegel Center for Biochemistry, Medical Faculty, University of Cologne, Joseph- Stelzmann-Str. 52, D-50931 Cologne, FRG +present address: 1Laboratory of Viral Diseases Building 4, Room 131 National Institute of Allergy and Infectious Diseases (NIAID) 2Laboratory of Cellular and Developmental Biology Building 50, Room 3345 National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) National Institutes of Health, Bethesda, Maryland 20892-8028, USA EMBO Journal Abstract LimC and LimD are two novel LIM proteins of Dictyostelium, which are comprised of double- and single-copy of LIM domains, respectively. Green fluorescent protein (GFP)-fused LimC and LimD proteins preferentially accumulate at areas of the cell-cortex where they colocalize with actin and associate transiently with cytoskeleton-dependent dynamic structures like phagosomes, macropinosomes and pseudopods. Furthermore, both LimC and LimD interact directly with F-actin in vitro. Mutant cells that lack either LimC or LimD or both exhibit normal growth. They are, however, significantly impaired in growth under stress conditions and are highly sensitive towards osmotic shock, suggesting that LimC and LimD contribute towards the maintenance of the cortical strength. Moreover, we noted an altered morphology and F-actin distribution in LimD- and LimC/D- mutants and changes in chemotactic motility associated with an increased pseudopod formation. Our results reveal both unique and overlapping roles for LimC and LimD and suggest that both act directly on the actin cytoskeleton and provide rigidity to the cortex. ----------------------------------------------------------------------------- [End Dicty News, volume 19, number 6]