dictyNews Electronic Edition Volume 38, number 1 January 6, 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 HAPPY 2012! ========= Abstracts ========= Bimodal distribution of motility and cell fate in Dictyostelium discoideum Pavana Goury Sistla1, Vidyanand Nanjundiah2, Gopal Pande1 1 Centre for Cellular and Molecular Biology, Uppal Road Hyderabad 500 007, India 2 Developmental Biology and Genetics Laboratory, Indian Institute of Science, Bangalore, 560012, India International Journal of Developmental Biology, in press Several differences between presumptive spore and presumptive stalk cells have been reported during the development of Dictyostelium discoideum from unicellular amoebae into multi-cellular fruiting bodies. In this paper we have examined whether cell motility-related properties are also among them. Cell speeds and localisation of motility-related signalling molecules in single cells were monitored by live cell imaging and immunostaining under three conditions: (a) in nutrient medium during growth, (b) immediately following transfer to starvation medium and (c) in nutrient medium that was re-introduced after a brief period of starvation. Cells moved randomly under all three conditions but the mean speed increased following transfer from nutrient medium to starvation medium. Further, the distribution of speeds in starvation medium was bimodal: about 20% of the cells moved significantly faster ('fast cells') than the remaining 80% ('slow cells'). Both changes occurred rapidly, i.e. by 15min of transfer to starvation medium; they reverted within 15min after restoration of the nutrient medium. The distribution and organization of the cell motility-related molecules F-actin, PTEN and PI3 kinase was different in slow and fast cells. Our data indicate that fast cells were capable of making more pseudopods and could readily redistribute their cytoskeletal apparatus and associated molecules, leading to a higher speed. Among starved cells, the calcium content of slow cells was significantly lower than that of fast cells. The slow/fast distinction was absent in Polysphondylium pallidum, a cellular slime mould that lacks the presumptive stalk and spore cell classes, and also in trishanku (triA-), a mutant of D. discoideum in which the prestalk and prespore states are unstable. We infer that very soon after the transition from growth to starvation, a switch is triggered in some D. discoideum cells, that separates them into two functional classes: (a) cells that continue to move at (slow) speeds that are seen in nutrient containing conditions, and whose calcium content remains at relatively low levels; and (b) cells that move significantly faster than pre-starvation cells and whose calcium levels are relatively higher. This switch may be the earliest step in the generation of the prespore and prestalk cell categories. The existence of the switch is in accordance with a previously postulated bistable mechanism underlying cell motility. Submitted by Pavana Goury Sistla [pavanags@ccmb.res.in] -------------------------------------------------------------------------------------- Cell-derived microvesicles and antitumoral multidrug resistance Irene Tatischeff Laboratoire Acides Nucleiques et Biophotonique (ANBioPhi), UPMC/CNRS, 4 Place Jussieu, Case Courrier 138, F-75252 Paris Cedex 05, France Comptes rendus Biologies, in press. Antitumoral chemotherapeutic treatments are often impaired by innate or acquired multidrug resistance (MDR). After four decades of MDR research, having underlined its complexity, new knowledge about the mechanisms of tumor resistance to antineoplastic drugs is a prerequisite for improving chemotherapy. Following our observations with a non-pathogenic eukaryotic microorganism, Dictyostelium discoideum, I suggest that MDR in tumor cells might be the consequence of a detoxification mechanism, mediated by cell-derived microvesicles. Recently published observations with tumoral human cells support this hypothesis. First, these cell-derived vesicles might impair chemotherapeutic efficiency of many structurally-different antineoplastic agents by preventing them to reach their intracellular target, followed by their expulsion outside the tumor cells, as observed for Dictyostelium cells. Secondly, beside their newly recognized function of intercellular communication, the cell-derived vesicles might also act as intercellular transporters of multidrug resistance proteins. Experiments are suggested for checking the hypothesis of cell-derived vesicles mediating multidrug resistance. Submitted by Irene Tatischeff [irene.tatischeff@upmc.fr] -------------------------------------------------------------------------------------- A Gbg Effector, ElmoE, Transduces GPCR Signaling to the Actin Network during Chemotaxis Jianshe Yan,1 Vassil Mihaylov,3 Xuehua Xu,1 Joseph A. Brzostowski, 2 Hongyan Li,1 Lunhua Liu,3 Timothy D. Veenstra,4 Carole A. Parent, 3 and Tian Jin1,* Developmental Cell (2012), doi:10.1016/j.devcel.2011.11.007 Activation of G protein-coupled receptors (GPCRs) leads to the dissociation of heterotrimeric G-proteins into Ga and Gbg subunits, which go on to regulate various effectors involved in a panoply of cellular responses. During chemotaxis, Gbg subunits regulate actin assembly and migration, but the protein(s) linking Gbg to the actin cytoskeleton remains unknown. Here, we identified a Gbg effector, ElmoE in Dictyostelium, and demonstrated that it is required for GPCR-mediated chemotaxis. Remarkably, ElmoE associates with Gbg and Dock-like proteins to activate the small GTPase Rac, in a GPCR-dependent manner, and also associates with Arp2/3 complex and F-actin. Thus, ElmoE serves as a link between chemoattractant GPCRs, G-proteins and the actincytoskeleton. The pathway, consisting of GPCR, Gbg, Elmo/Dock, Rac, and Arp2/3, spatially guides the growth of dendritic actin networks in pseudopods of eukaryotic cells during chemotaxis. Submitted by Jianshe Yan [yanjia@niaid.nih.gov] ============================================================== [End dictyNews, volume 38, number 1]