dictyNews Electronic Edition Volume 43, number 11 May 19, 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 ========= A Tripeptidyl peptidase 1 is a binding partner of GPHR (Golgi pH regulator) in Dictyostelium Maria Stumpf1, Rolf Müller1, Berthold Gaßen1, Regina Wehrstedt1, Petra Fey2, Malte A. Karow1, Ludwig Eichinger1, Gernot Glöckner1, Angelika A. Noegel1 1Institute of Biochemistry I, Medical Faculty, University Hospital Cologne, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Köln, Germany; 2dictyBase, Northwestern University, Biomedical Informatics Center and Center for Genetic Medicine, Chicago, Illinois, USA Disease Models & Mechanisms, in press Mutations in tripeptidyl peptidase 1 (TPP1) have been associated with late infantile neuronal ceroid lipofuscinosis (NCL2), a neurodegenerative disorder. TPP1 is a lysosomal serine protease, which removes tripeptides from the amino terminus of proteins and is composed of an N-terminal prodomain and a catalytic domain. It is conserved in mammals, amphibians, fish and the amoeba Dictyostelium discoideum. D. discoideum harbors at least six genes encoding tripeptidyl peptidase 1, tpp1A to tpp1F. We identified TPP1F as binding partner of Dictyostelium GPHR (Golgi pH regulator), which is an evolutionary highly conserved intracellular transmembrane protein. For the interaction, a region encompassing the DUF3735 (GPHR_N) domain of GPHR was responsible. In TPP1F the binding site was located in the prodomain. The Tpp1F gene is transcribed throughout development and translated into a polypeptide of approximately 65 kDa. TPP1 activity was demonstrated for TPP1F-GFP immunoprecipitated from D. discoideum cells. Its activity could be inhibited by addition of the recombinant DUF3735 domain of GPHR. Knockout tpp1F mutants did not display a particular phenotype and TPP1 activity was not abrogated, which is presumably due to expression of Tpp1B showing the highest expression levels of all Tpp1 genes during growth. The GPHR interaction was not restricted to TPP1F but occurred also with TPP1B. Based on previous reports showing that the majority of the TPP1 mutations in NCL2 resulted in reduction or loss of enzyme activity, our findings may help to create new reagents with which one can affect the activity of the protein and ameliorate the disease. submitted by: Ludwig Eichinger [ludwig.eichinger@uni-koeln.de] ——————————————————————————————————————— Multiple Dictyostelid Species Destroy Biofilms of Klebsiella oxytoca and Other Gram Negative Species Dean Sanders1, Katarzyna D. Borys2, Fikrullah Kisa3, Sheryl A. Rakowski4, Marcela Lozano, Marcin Filutowicz5 https://doi.org/10.1016/j.protis.2017.04.001 Dictyostelids are free-living phagocytes that feed on bacteria in diverse habitats. When bacterial prey is in short supply or depleted, they undergo multicellular development culminating in the formation of dormant spores. In this work, we tested isolates representing four dictyostelid species from two genera (Dictyostelium and Polysphondylium) for the potential to feed on biofilms preformed on glass and polycarbonate surfaces. The abilities of dictyostelids were monitored for three hallmarks of activity: 1) spore germination on biofilms, 2) predation on biofilm enmeshed bacteria by phagocytic cells and 3) characteristic stages of multicellular development (streaming and fructification). We found that all dictyostelid isolates tested could feed on biofilm enmeshed bacteria produced by human and plant pathogens: Klebsiella oxytoca, Pseudomonas aeruginosa, Pseudomonas syringae, Erwinia amylovora 1189 (biofilm former) and E. amylovora 1189 Δams (biofilm deficient mutant). However, when dictyostelids were fed planktonic E. amylovora Δams the bacterial cells exhibited an increased susceptibility to predation by one of the two dictyostelid strains they were tested against. Taken together, the qualitative and quantitative data presented here suggest that dictyostelids have preferences in bacterial prey which affects their efficiency of feeding on bacterial biofilms. submitted by: Marcin Filutowicz [msfiluto@wisc.edu] ============================================================== [End dictyNews, volume 43, number 11]