dictyNews Electronic Edition Volume 40, number 11 April 18, 2014 Please submit abstracts of your papers as soon as they have been accepted for publication by by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit or by sending them to dicty@northwestern.edu Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase ========= Abstracts ========= Tianzhi Luo, Vasudha Srivastava, Yixin Ren, Douglas N. Robinson Mimicking the mechanical properties of the cell cortex by the self-assembly of an actin cortex in vesicles. App. Phys. Lett. 2014, in press The composite of the actin cytoskeleton and plasma membrane plays important roles in many biological events. Here, we employed the emulsion method to synthesize artificial cells with biomimetic actin cortex in vesicles and characterized their mechanical properties. We demonstrated that the emulsion method provides the flexibility to adjust the lipid composition and protein concentrations in artificial cells to achieve the desired size distribution, internal microstructure and mechanical properties. Moreover, comparison of the cortical elasticity measured for reconstituted artificial cells to that of real cells, including those manipulated using genetic depletion and pharmacological inhibition, strongly supports that actin cytoskeletal proteins are dominant over lipid molecules in cortical mechanics. Our study indicates that the assembly of biological systems in artificial cells with purified cellular components provides a powerful way to answer biological questions. Submitted by Douglas Robinson [dnr@jhmi.edu] --------------------------------------------------------------------------- Cell signaling during development of Dictyostelium William F. Loomis Cell and Developmental Biology, University of California San Diego La Jolla, CA 92093 Developmental Biology, in press Review Continuous communication between cells is necessary for development of any multicellular organism and depends on the recognition of secreted signals. A wide range of molecules including proteins, peptides, amino acids, nucleic acids, steroids and polylketides are used as intercellular signals in plants and animals. They are also used for communication in the social amoeba Dictyostelium discoideum when the solitary cells aggregate to form multicellular structures. Many of the signals are recognized by surface receptors that are seven- transmembrane proteins coupled to trimeric G proteins, which pass the signal on to components within the cytoplasm. Dictyostelium cells have to judge when sufficient cell density has been reached to warrant transition from growth to differentiation. They have to recognize when exogenous nutrients become limiting, and then synchronously initiate development. A few hours later they signal each other with pulses of cAMP that regulate gene expression as well as direct chemotactic aggregation. They then have to recognize kinship and only continue developing when they are surrounded by close kin. Thereafter, the cells diverge into two specialized cell types, prespore and prestalk cells, that continue to signal each other in complex ways to form well proportioned fruiting bodies. In this way they can proceed through the stages of a dependent sequence in an orderly manner without cells being left out or directed down the wrong path. Submitted by Bill Loomis [wloomis@ucsd.edu] --------------------------------------------------------------------------- TSET: an ancient and widespread membrane trafficking complex Jennifer Hirst1¤*, Alexander Schlacht2¤, John P. Norcott3+, David Traynor4+, Gareth Bloomfield4, Robin Antrobus1, Robert R. Kay4, Joel B. Dacks2*, and Margaret S. Robinson1* 1University of Cambridge, Cambridge Institute for Medical Research, Cambridge, UK 2Department of Cell Biology, University of Alberta, Edmonton, Canada 3University of Cambridge, Department of Engineering, Cambridge, UK 4MRC Laboratory of Molecular Biology, Cambridge, UK eLife, in press The heterotetrameric AP and F-COPI complexes help to define the cellular map of modern eukaryotes. To search for related machinery, we developed a structure-based bioinformatics tool, and identified the core subunits of TSET, a Òmissing linkÓ between the APs and COPI. Studies in Dictyostelium indicate that TSET is a heterohexamer, with two associated scaffolding proteins. TSET is non-essential in Dictyostelium, but may act in plasma membrane turnover, and is essentially identical to the recently described TPLATE complex, TPC. However, whereas TPC was reported to be plant-specific, we can identify a full or partial complex in every eukaryotic supergroup. An evolutionary path can be deduced from the earliest origins of the heterotetramer/scaffold coat to its multiple manifestations in modern organisms, including the mammalian muniscins, descendants of the TSET medium subunits. Thus, we have uncovered the machinery for an ancient and widespread pathway, which provides new insights into early eukaryotic evolution. Submitted by Rob Kay [rrk@mrc-lmb.cam.ac.uk] --------------------------------------------------------------------------- Calcineurin-Crz1 signaling in lower eukaryotes. Thewes S Eukaryotic Cell, in press Review Calcium ions are ubiquitous intracellular messengers. An increase in the cytosolic Ca2+ concentration activates many proteins including calmodulin and the Ca2+/calmodulin-dependent protein phosphatase calcineurin. The phosphatase is conserved from yeast to man (except plants) and many target proteins of calcineurin have been identified. The most prominent and best-investigated targets, however, are the transcription factors NFAT (nuclear factor of activated T-cells) in mammals and Crz1 (calcineurin responsive zinc finger 1) in yeast. In recent years many orthologues of Crz1 have been identified and characterized in various fungi, amoebae and other lower eukaryotes. It has been shown that the functions of calcineurin-Crz1 signaling are conserved in the different organisms ranging from ion homeostasis, through cell wall biogenesis, to the building of filamentous structures. Furthermore frequency-modulated gene expression through Crz1 has been discovered as a striking new mechanism by which cells can coordinate their response to a signal. In this review I will focus on the latest findings concerning calcineurin-Crz1 signaling in fungi, amoebae and other lower eukaryotes. I will discuss the potential of Crz1 and its orthologues as putative drug targets and I will also discuss possible parallels with calcineurin-NFAT signaling in mammals. Submitted by Sascha Thewes [sascha.thewes@fu-berlin.de] ============================================================== [End dictyNews, volume 40, number 11]