CSM-News, Electronic Edition Volume 1, number 3 29 May 1993 The electronic edition of the CSM News serves the Cellular Slime Mold community by rapidly disseminating information of interest to investigators who use cellular slime molds as experimental organisms. We would all appreciate it if you would send us the title, author list and abstracts of papers which use cellular slime molds as soon as they are accepted for publication. To date the response has been quite good. Keep it up. Send abstracts or other announcements you might have to r-chisholm@nwu.edu. ==================================================================== Announcements ------------- MEETING NOTICE The 1994 Dictyostelium meeting will be held at UCSD and is being organized by Rick Firtel and Bill Loomis. The meeting will start Sunday evening, August 21, and will end Friday morning, August 26. Accommodations will be available for those who would like to arrive early or stay on after the meeting ends. Information and registration forms will be mailed in January, 1994, and an advertisement will be placed in Nature. We expect everyone attending to enjoy a great meeting and have a fun time in La Jolla. The weather will be great at that time of year. Rick and Bill -------------------------------------------------------------- UPDATE #3 FOR FRANKE CSM REFERENCE DATABASE AVAILABLE Update #3 to the Franke database of Dictyostelium references is now available for download by anonymous ftp from worms.cmsbio.nwu.edu [129.105.233.50]. Be sure to download the readme.txt file. It contains useful information. The database and updates are located in the directory pub/dicty/reference_database. When the original database and three updates are merged you should have all known references to the Dictyostelium literature through April 1993 Current Contents. Many thanks to Richard Sucgang and Jacob Franke for this effort! ----------------------------------------------------------------- BIOLOGISTS GUIDE TO INTERNET If you are new to the world of computer network information you should download a copy of the file named "biologists.guide.to.internet" from the "pub/dicty" directory by anonymous ftp to worms.cmsbio.nwu.edu. This file, prepared by Una Smith of Yale, provides a good overview and fairly comprehensive list of the resources available to biologists over the Internet. If you aren't aware of this stuff get this file. You'll be amazed by what is available! ================================================================== Abstracts of Recently Accepted Papers ------------------------------------- Phototaxis genes on linkage group V in Dictyostelium discoideum. P.K. DARCY, Z. WILCZYNSKA AND P.R. FISHER Microbiology Department, La Trobe University, Bundoora 3083, Melbourne, AUSTRALIA. Telephone: 03 4792496. FAX: 03 4791222 Key Words: Phototransduction genes, Dictyostelium , Linkage Group V. FEMS Microbiol. Letters In Press. During the course of mapping and complementation analysis of phototaxis ( pho ) mutations in Dictyostelium discoideum we have assigned to linkage group V three mutant pho alleles belonging to complementation groups phoG and phoK. These are the first genetic markers with an easily recognizable phenotype to be found on this linkage group. ====================================================================== Endo-lysosomal acidification in Dictyostelium discoideum amoebae. Effects of two endocytosis inhibitors: caffeine and cycloheximide. Laurence Aubry, Gerard Klein, Michel Satre Laboratoire de Biologie Cellulaire, DBMS/BC, CEN-G,38041 Grenoble/France. Accepted, Eur.J. Cell Biol. Abstract Fluid-phase endocytosis (pinocytosis) is highly active in amoebae of the cellular slime mould Dictyostelium discoideum as it provides an efficient entry of nutrients in axenic strains. Detailed kinetic analyses were conducted using fluorescein labelled dextran (FITC-dextran) as fluid-phase marker and pH probe. Cells were first pulsed with FITC-dextran during a short period then chased by suspension in probe free medium. Chase kinetics were characterised by a lag phase of about 40 min before pseudo-first order FITC-dextran efflux and thus reflected the progression of the probe cohort through the various endosomal compartments along the endosomal pathway. Temporal evolution of endo-lysosomal pH showed a rapid acidification (T1/2 = 10 min) to pH 5.0 followed by an increase up to pH 6.2-6.3. The effects of cycloheximide and caffeine, two inhibitors of endocytosis in Dictyostelium amoebae, on the evolution of endosomal pH during fluid-phase endocytosis, have been investigated. Cycloheximide fully blocked the cellular transit of FITC-dextran but acidification of endo-lysosomal compartments still took place. Caffeine increased endo-lysosomal pH, probably as a consequence of an elevation of cytosolic Ca2+. Furthermore, it allowed the functional identification of a caffeine-insensitive terminal segment of the endocytic pathway. It corresponded to a recycling, post-lysosomal compartment at pH 6.2-6.3 with an apparent volume of 160 microm3/amoebae. ================================================================= DEVELOPMENTALLY REGULATED CHANGES IN 1,2-DIACYLGLYCEROL IN DICTYOSTELIUM: REGULATION BY LIGHT AND G PROTEINS Andrew B. Cubitt, Suranganie Dharmawardhane, and Richard A. Firtel J. Biol. Chem., in press ABSTRACT We have measured 1,2-diacylglycerol (DG) mass during Dictyostelium development. DG levels are initially high in vegetative cells, decrease upon starvation, increase during aggregation, and rise dramatically during culmination, concomitant with SpiA (a spore-cell-specific gene) expression. These results are consistent with DG being involved inculmination-stage morphological changes and cell-type differentiation. Mutant analysis shows that the rise in DG during aggregation requires cAMP signaling pathways, but is not directly regulated through these processes but via developmental programs induced through cAMP. DG accumulation during aggregation is ~8-fold higher than would be expected from inositol lipid hydrolysis (1), suggesting that DG is produced from sources in addition to PtdIns(4,5)P2. Our data suggest that during aggregation, although some DG is formed through phospholipase D activity, other pathways (e.g. de novo synthesis) may be more important regulators of DG accumulation. During culmination, DG accumulation correlated with the formation of phosphatidic acid and phosphatidylethanol suggesting the activation of phospholipase D. During this time, the [3H]-palmitate labeling of a number of phospholipids decreased rapidly, suggesting a rapid metabolism of phospholipids at this time. Exposure of slugs developed in the dark to light, which initiates culmination, causes rapid DG accumulation, suggesting the activation of phospholipid hydrolysis. The temporal pattern and level of DG accumulation is altered in Galpha1 null and overexpressing strains, suggesting that Galpha1 is upstream from DG formation during culmination. These results demonstrate that specific pathways of DG formation are under developmental control, and suggest a possible link between light, the activation of DG production, and induction of culmination. =================================================================== [End CSM-News, Volume 1, number 3]