dictyNews Electronic Edition Volume 43, number 2 January 27, 2017 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. 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 ========= Co-existence of Ras activation in a chemotactic signal transduction pathway and in an autonomous wave - forming system Mary Ecke1 and Günther Gerisch1 1Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany. SmallGTPases, in press The activation of Ras is common to two activities in cells of Dictyostelium discoideum: the directed movement in a gradient of chemoattractant and the autonomous generation of propagating waves of actin polymerization on the substrate-attached cell surface. We produced large cells by electric-pulse induced fusion to simultaneously study both activities in one cell. For imaging, a fluorescent label for activated Ras was combined with labels for filamentous actin, PIP3, or PTEN. Chemotactic responses were elicited in a diffusion gradient of cyclic AMP. Waves initiated at sites separate from the front of the cell propagated in all directions. Nevertheless, the wave-forming cells were capable of recognizing the attractant gradient and managed to migrate in its direction. submitted by: Günther Gerisch [gerisch@biochem.mpg.de] ——————————————————————————————————————— The Arp2/3 inhibitory protein Arpin is dispensable for chemotaxis Irène Dang 1, Joern Linkner 2, Jun Yan 3, Daniel Irimia 3, Jan Faix 2, Alexis Gautreau 1. 1 Ecole Polytechnique, Université Paris-Saclay, CNRS UMR7654, Palaiseau 91120, France. 2 Institute for Biophysical Chemistry, Hannover Medical School, Hannover 30625, Germany. 3 Massachusetts General Hospital and Harvard Medical School, BioMEMS Resource Center, Boston, MA 02129,USA. Biology of the Cell, in press Arpin is an Arp2/3 inhibitory protein, which decreases the protrusion lifetime and hence directional persistence in the migration of diverse cells. Arpin is activated by the small GTPase Rac, which controls cell protrusion, thus closing a negative feedback loop that renders the protrusion intrinsically unstable. Because of these properties, it was proposed that Arpin might play a role in directed migration, where directional persistence has to be finetuned. We report here, however, that Arpin depleted tumor cells and Arpin knock-out Dictyostelium amoeba display no obvious defect in chemotaxis. These results do not rule out a potential role of Arpin in other systems, but argue against a general role of Arpin in chemotaxis. submitted by: Jan Faix [faix.jan@mh-hannover.de] ——————————————————————————————————————— Tipping the scales: Lessons from simple model systems on inositol imbalance in neurological disorders Anna D Frej, Grant P Otto, Robin SB Williams* European Journal of Cell Biology, In Press Inositol and inositol-containing compounds have signalling and regulatory roles in many cellular processes, suggesting that inositol imbalance may lead to wide-ranging changes in cellular functions. Indeed, changes in inositol-dependent signalling have been implicated in various diseases and cellular functions such as autophagy, and these changes have often been proposed as therapeutic targets. However, few studies have highlighted the links between inositol depletion and the downstream effects on inositol phosphates and phosphoinositides in disease states. For this research, many advances have employed simple model systems that include the social amoeba D. discoideum and the yeast S. cerevisiae, since these models enable a range of experimental approaches that are not possible in mammalian models. In this review, we discuss recent findings initiated in simple model systems and translated to higher model organisms where the effect of altered inositol, inositol phosphate and phosphoinositide levels impact on bipolar disorder, Alzheimer disease, epilepsy and autophagy. submitted by: Robin Williams [robin.williams@rhul.ac.uk] ============================================================== [End dictyNews, volume 43, number 2]