dictyNews Electronic Edition Volume 26, number 8 March 10, 2006 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 ============= Blebbing of Dictyostelium cells in response to chemoattractant Paul D Langridge and Robert R. Kay Experimental Cell Research Stimulation of Dictyostelium cells with a high uniform concentration of the chemoattractant cyclic-AMP induces a series of morphological changes, including cell rounding and subsequent extension of pseudopodia in random directions. Here we report that cyclic-AMP also elicits blebs and analyse their mechanism of formation. The surface area and volume of cells remain constant during blebbing indicating that blebs form by the redistribution of cytoplasm and plasma membrane rather than the exocytosis of internal membrane coupled to a swelling of the cell. Blebbing occurs immediately after a rapid rise and fall in submembraneous F-actin, but the blebs themselves contain little F-actin as they expand. A mutant with a partially inactivated Arp2/3 complex has a greatly reduced rise in F-actin content, yet shows a large increase in blebbing. This suggests that bleb formation is not enhanced by the preceding actin dynamics, but is actually inhibited by them. In contrast, cells that lack myosin-II completely fail to bleb. We conclude that bleb expansion is likely to be driven by hydrostatic pressure produced by cortical contraction involving myosin-II. As blebs are induced by chemoattractant we speculate that hydrostatic pressure is one of the forces driving pseudopod extension during movement up a gradient of cyclic-AMP. Submitted by: Paul Langridge [pl@mrc-lmb.cam.ac.uk] ----------------------------------------------------------------------------- The Dictyostelium KinomeÑAnalysis of the Protein Kinases from a Simple Model Organism Jonathan M. Goldberg1*, Gerard Manning2*, Allen Liu1, Petra Fey3, Karen E. Pilcher3, Yanji Xu1, Janet L. Smith1 *These authors contributed equally to this work. 1 Boston Biomedical Research Institute, Watertown, Massachusetts,USA 2 Razavi-Newman Center for Bioinformatics, Salk Institute for Biological Studies, La Jolla, California, USA 3 Center for Genetic Medicine, Northwestern University, Chicago, Illinois, USA PLoS Genetics, in press Dictyostelium discoideum is a widely studied model organism with both unicellular and multicellular forms in its developmental cycle. The Dictyostelium genome encodes 285 predicted protein kinases, similar to the count of the much more advanced Drosophila. It contains members of most kinase classes shared by fungi and metazoans, as well as many previously thought to be metazoan specific, indicating that they have been secondarily lost from the fungal lineage. This includes the entire tyrosine kinaseÐlike (TKL) group, which is expanded in Dictyostelium and includes several novel receptor kinases. Dictyostelium lacks tyrosine kinase group kinases, and most tyrosine phosphorylation appears to be mediated by TKL kinases. About half of Dictyostelium kinases occur in subfamilies not present in yeast and metazoa, suggesting that protein kinases have played key roles in the adaptation of Dictyostelium to its habitat. This study offers insights into kinase evolution and provides a focus for signaling analysis in this system. Submitted by: Janet Smith [janet.l.smith@gmail.com] ============================================================================== [End dictyNews, volume 26, number 8]