dictyNews Electronic Edition Volume 29, number 8 Sptember 15, 2007 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. ========= Abstracts ========= A GPCR involved in post aggregation events in Dictyostelium discoideum Yogikala Prabhu, Subhanjan Mondal, Ludwig Eichinger and Angelika A. Noegel Center for Biochemistry, Medical Faculty and Center for Molecular Medicine Cologne, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Koeln, Germany Developmental Biology, in press Dictyostelium has 55 genes encoding seven-transmembrane G-protein-coupled receptors (GPCR) that belong to five of the six GPCR families. GrlA is one of the 17 family 3 GPCRs in Dictyostelium all of which resemble GABAB receptors from higher eukaryotes. GrlA is a 90 kDa protein present on the plasma membrane and on membranes of the ER. It has a large extracellular domain with homology to bacterial periplasmic proteins. The GrlA message is present throughout development and shows increased levels during the post aggregation stages. Inactivation of the grlA gene does not severely affect the growth phase, however, it leads to a delay in the development at the post aggregation stage. GrlA deficient strains show an altered DIF-1 response specific to the prestalk specific ecmA and ecmB gene, reduced car2 and pkaC transcript levels and form a reduced number of spores. Germination of the spores was as in wild type. Transcriptional profiling supported the defect in the sporulation pathway as a large number of genes involved in the biogenesis and organization of the extracellular matrix and the sporulation process were significantly down regulated in the mutant. Submitted by: Angelika Noegel [noegel@uni-koeln.de] -------------------------------------------------------------------------------- Expression of zinc transporter family genes in Dictyostelium Nobuya Sunaga†, Meri Monna, Nao Shimada, Mai Tsukamoto and Takefumi Kawata1,* 1Department of Biology, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan TEL & FAX: +81-47-472-5156 †Present address: Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, Minami-Ohsawa 1-1, Hachioji, Tokyo 192-0397, Japan *Corresponding author Int. J. Dev. Biol., in press Regulation of the zinc ion concentration is physiologically important to control the activities of a variety of cellular molecules. A BLAST search against a conserved domain of known zinc transporters identified twelve putative zinc transporter family genes in the Dictyostelium genome. Phylogenetic analysis revealed the presence of three zinc transporter subfamilies in Dictyostelium. One subfamily of proteins, the ZntA-D proteins, has weak homology to the STAT3-inducible LIV-1 protein. In addition, in situ hybridization revealed that Dd-STATa is necessary for the differentiation of pstAB cells, which are where zntA~D genes are expressed. Thus, Dd-STATa may control stalk cell differentiation through some members of the zinc transporter family genes during Dictyostelium development. Submitted by: Takefumi Kawatae [tkawata@bio.sci.toho-u.ac.jp] -------------------------------------------------------------------------------- Developmental Commitment in Dictyostelium discoideum Mariko Katoh, Guokai Chen, Emily Roberge, Gad Shaulsky and Adam Kuspa Departments of Genetics and Biochemistry, Baylor College of Medicine, Houston, TX, USA Eukaryotic Cell, in press Upon starvation, Dictyostelium cells halt cell proliferation, aggregate into multicellular organisms, form migrating slugs and undergo morphogenesis into fruiting bodies while differentiating into dormant spores and dead stalk cells. At almost any developmental stage cells can be forced to dedifferentiate when they are dispersed and diluted into nutrient broth. However, migrating slugs can traverse lawns of bacteria for days without dedifferentiating, ignoring abundant nutrients and continuing development. We now show that developing Dictyostelium cells revert to the growth phase only when bacteria are supplied during the first 4-6 hours of development, but after this time, cells continue to develop regardless of the presence of food. We postulate that the cells’ inability to revert to the growth phase after 6 hours represents a commitment to development. We show that the onset of commitment correlates with the cells’ loss of phagocytic function. By examining mutant strains, we also show that commitment requires extracellular cAMP signaling. Moreover, cAMP pulses are sufficient to induce both commitment and the loss of phagocytosis in starving cells, whereas starvation alone is insufficient. Finally, we show that inhibition of development by food prior to commitment is independent of contact between the cells and the bacteria and that small soluble molecules, probably amino acids, inhibit development first few hours and subsequently the cells become unable to react to the molecules and commit to development. We propose that commitment serves as a checkpoint that ensures the completion of cooperative aggregation of developing Dictyostelium cells once it has begun, dampening the response to nutritional cues that might inappropriately block development. Submitted by: Gad Shaulsky [gadi@bcm.tmc.edu] -------------------------------------------------------------------------------- Dictyostelium Hip1r contributes to spore shape and requires epsin for phosphorylation and localization Shannon Lea Repass1, Rebecca J. Brady1, and Theresa J. O'Halloran1,* 1 Department of Molecular Cell and Developmental Biology, The University of Texas at Austin, Austin, TX 78712 *corresponding author Journal of Cell Science, in press Clathrin-coated pits assemble on the plasma membrane to select and sequester proteins within coated vesicles for delivery to intracellular compartments. While a host of clathrin associated proteins have been identified, much less is known regarding the interactions between clathrin associated proteins or how individual proteins influence the function of other proteins. In this study, we present evidence of a functional relationship between two clathrin associated proteins in Dictyostelium, Hip1r and epsin. Hip1r null cells form fruiting bodies that yield defective spores that lack the organized fibrils typical of wild type spores. This spore coat defect leads to round, rather than ovoid, spores in Hip1r null cells that exhibit decreased viability. Like Hip1r null cells, epsin null cells also construct fruiting bodies with round spores, but these spores are more environmentally robust. Double null cells that harbor deletions in both epsin and Hip1r form fruiting bodies with spores identical in shape and viability to Hip1r single null cells. In growing amoeba, Hip1r is phosphorylated and localizes to punctae on the plasma membrane that also contain epsin. Both the phosphorylation state and localization of Hip1r into membrane punctae require epsin. Moreover, expression of the NH2-terminal ENTH domain of epsin is sufficient to restore both the phosphorylation and the restricted localization of Hip1r within plasma membrane punctae. Results from this study reveal a novel interaction between two clathrin associated proteins during cellular events in both growing and developing Dictyostelium cells. Submitted by: Terry O'Halloran [t.ohalloran@mail.utexas.edu] ============================================================== [End dictyNews, volume 29, number 8]