CSM News Electronic Edition Volume 6, number 1 January 13, 1996 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to CSM-News@worms.cmsbio.nwu.edu. Back issues of CSM-News, the CSM Reference database and other useful information is available by anonymous ftp from worms.cmsbio.nwu.edu [165.124.233.50], via Gopher at the same address, or by World Wide Web at the URL "http://worms.cmsbio.nwu.edu/dicty.html" ================ Jobs Available ================ POSITION OPEN: 2 PhD Studentships INSTITUTION: Max-Planck-Institute for Medical Research ADDRESS: Dept. of Biophysics Max-Planck-Institute for Medical Research Jahnstr. 29 D-69120-Heidelberg Germany CONTACT PERSON: Dietmar Manstein PHONE: (+49-6221) 486 212 FAX: (+49-6221) 486 437 EMAIL: manstein@mpimf-heidelberg.mpg.de DATE OF AVAILABILITY: Immediately DURATION: 2 (+1) years SALARY: A13/2 JOB DESCRIPTION: The laboratory uses the lower eukaryote Dictyostelium discoideum as a model system for cell motility and for the production and characterisation of myosin and dynamin. We use a multifaceted approach combining biophysical, biochemical and molecular biology techniques (e.g. enzyme kinetics, X-ray crystallography, single-molecule fluorescence light microscopy techniques, site-directed mutagenesis, gene targeting) to study the functional behaviour and the regulation of these mechano-enzymes in vitro and in vivo. APPLICATION REQUIREMENTS: To apply, send a c.v., and a cover letter that includes a brief statement of your career goals and research interests. APPLICATION DEADLINE: None ========== Abstract ========== cGMP accumulation induced by hypertonic stress in Dictyostelium discoideum Masakazu Oyama Department of Life Science, Faculty of Science, Himeji Institute of Technology, Shosha 2167, Himeji, Hyogo 671-22 Japan J. Biol. Chem., in press Summary The change in extracellular osmolarity from 0.07 osM to 0.38 osM caused rapid cell shrinkage and loss of pseudopodes in Dictyostelium discoideum amoebae and induced elevation of total (cellular+extracellular) cGMP with a 2.5 min lag. cGMP accumulation reached a peak at 10 to 15 min after the change, and then the total cGMP gradually decreased. cGMP first accumulated intracellularly and was then secreted. A roughly identical osmotic concentration was required for the accumulation when the effect of KCl and glucose was tested. The non-osmolytes, formamide and ethanol, did not induce the accumulation. We concluded that hypertonic stress induces cGMP accumulation in D. discoideum amoebae. The hypertonic stress-induced accumulation of cGMP was observed in a streamer F mutant (NP368) that lacks cGMP-specific phosphodiesterase. While Dictyostelium cells also have non-specific phosphodiesterases that degrade both cGMP and cAMP, hypertonic stress induced only a small increase in cAMP in wild type and streamer F cells. These results suggest that hypertonic stress-induced accumulation of cGMP is due to the activation of guanylate cyclase rather than the inhibition of phosphodiesterases. Binding of folic acid to the specific receptors on the cell surface induces a rapid transient accumulation of cGMP that reaches a peak at 10 sec. When cells were stimulated by folic acid after the addition of 0.31 M glucose, rapid transient cGMP acumulation was observed immediately after the stimulation by folic acid and prolonged cGMP accumulation was induced 2-3 min after the addition of glucose irrespective of the timing of folic acid stimulation. These results suggest that the hypertonic stress-induced and the receptor-mediated accumulation proceed independently of one another. 2,3-dimercapto-1-propanol, a thiol-reducing reagent, induces prolonged cGMP accumulation similar to hypertonic stress. However, the hypertonic stress-induced cGMP accumulation was enhanced by EDTA and was not suppressed by folic acid and cAMP. These characteristics are distinct from the reducing reagent-induced accumulation that is suppressed by EDTA, folic acid and cAMP. These findings show that hypertonic stress has a unique effect on the activation of guanylate cyclase. --------------------------------------------------------------------- [End CSM News, volume 6, number 1]