dictyNews Electronic Edition Volume 38, number 29 November 16, 2012 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 ========= Structure and function of a unique pore-forming protein from a pathogenic acanthamoeba Matthias Michalek1,2, Frank D. Sšnnichsen3, Rainer Wechselberger4, Andrew J. Dingley5, Chien-Wen Hung6, Annika Kopp7, Hans Wienk4, Maren Simanski1, Rosa Herbst1, Inken Lorenzen2, Francine Marciano-Cabral8, Christoph Gelhaus1, Thomas Gutsmann7, Andreas Tholey6, Joachim Grštzinger2, Matthias Leippe1* 1 Zoological Institute, Zoophysiology, Christian-Albrechts UniversitŠt zu Kiel, Olshausenstr. 40, 24098 Kiel, Germany. 2 Institute of Biochemistry, Christian-Albrechts UniversitŠt zu Kiel, Olshausenstr. 40, 24098 Kiel, Germany. 3 Otto Diels Institute for Organic Chemistry, Christian-Albrechts UniversitŠt zu Kiel, Olshausenstr. 40, 24098 Kiel, Germany. 4 NMR Spectroscopy Research Group, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands. 5 School of Chemical Sciences and School of Biological Sciences, The University of Auckland, New Zealand. 6 Division of Systematic Proteome Research, Institute for Experimental Medicine, Christian-Albrechts UniversitŠt zu Kiel, Niemannsweg 11, 24105 Kiel, Germany. 7 Division of Biophysics, Research Center Borstel, Center for Medicine and Bioscience, 23845 Borstel, Germany. 8 Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, 1101 E. Marshall Street, Richmond, Virginia 23298-0678, USA. * To whom correspondence should be addressed: mleippe@zoologie.uni-kiel.de Nature Chemical Biology, in press Human pathogens often produce soluble protein toxins that generate pores inside membranes, resulting in death of target cells and tissue damage. In pathogenic amoebae, this has been exemplified with amoebapores of the enteric protozoan parasite Entamoeba histolytica. Here we characterize acanthaporin, to our knowledge the first pore-forming toxin to be described from acanthamoebae, which are free-living, bacteria-feeding, unicellular organisms that are opportunistic pathogens of increasing importance and cause severe and often fatal diseases. We isolated acanthaporin from extracts of virulent Acanthamoeba culbertsoni by tracking its pore-forming activity, molecularly cloned the gene of its precursor and recombinantly expressed the mature protein in bacteria. Acanthaporin was cytotoxic for human neuronal cells and exerted antimicrobial activity against a variety of bacterial strains by permeabilizing their membranes. The tertiary structures of acanthaporin«s active monomeric form and inactive dimeric form, both solved by NMR spectroscopy, revealed a currently unknown protein fold and a pH-dependent trigger mechanism of activation. Submitted by Matthias Leippe [mleippe@zoologie.uni-kiel.de] --------------------------------------------------------------------------- Daydreamer, a Ras effector and GSK-3 substrate, is important for directional sensing and cell motility Verena Kšlsch, Zhouxin Shen, Susan Lee, Katarzyna Plak, Pouya Lotfi, Jessica Chang, Pascale G. Charest, Jesus Lacal Romero, Taeck J. Jeon, Arjan Kortholt, Steven P. Briggs and Richard A. Firtel Mol Bio Cell, in press How independent signaling pathways are integrated to holistically control a biological process is not well understood. We have identified Daydreamer (DydA), a new member of the MRL (Mig10/RIAM/Lamellipodin) family of adaptor proteins that localizes to the leading edge. DydA is a putative Ras effector that is required for cell polarization and directional movement during chemotaxis. dydA- cells exhibit elevated F-actin and assembled MyoII, increased and extended PI3K activity, and extended phosphorylation of the activation loop of PKB and PKBR1, suggesting that DydA is involved in the negative regulation of these pathways. DydA is phosphorylated by GSK-3, which is required for some, but not all, of DydAŐs functions, including the proper regulation of PKB and PKBR1 and MyoII assembly. gskA- cells exhibit very strong chemotaxis phenotypes, as previously described, but exhibit an increased rate of random motility. gskA- cells have a reduced MyoII response, a reduced level of PI(3,4,5)P3 production but a highly extended recruitment of PI3K to the plasma membrane and highly extended kinetics of PKB and PKBR1 activation. Our results demonstrate that GSK-3 function is essential for chemotaxis, regulating multiple substrates and that one of these effectors, DydA, plays a key function in the dynamic regulation of chemotaxis. Submitted by Rick Firtel [rafirtel@ucsd.edu] ============================================================== [End dictyNews, volume 38, number 29]