dictyNews Electronic Edition Volume 36, number 5 Feb 11, 2011 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 ========= Abstracts ========= The dual-specificity protein phosphatase MkpB, homologous to mammalian MKP phosphatases, is required for D. discoideum postaggregative development and cisplatin response Ver—nica Moncho-Amor, Mar’a Galardi-Castilla, Rosario Perona and Leandro Sastre Differentiation, in press Dual-specificity protein phosphatases participate in signal transduction pathways inactivating mitogen-activated protein kinases (MAP Kinases). These signaling pathways are of critical importance in the regulation of numerous biological processes, including cell proliferation, differentiation and development. The social amoeba Dictyostelium discoideum harbors 14 genes coding for proteins containing regions very similar to the dual-specificity protein phosphatase domain. One of these genes, mkpB, additionally codes for a region similar to the Rhodanase domain, characteristic of animal MAP Kinase-phosphatases, in its N-terminal region. Cells that over-express this gene show increased protein phosphatase activity. mkpB is expressed in D. discoideum amoeba at growth but it is greatly induced at 12 hours of multi-cellular development. Although it is expressed in all the cells of developmental structures, mkpB mRNA is enriched in cells with a distribution typical of anterior-like cells. Cells that express a catalytically inactive mutant of MkpB grow and aggregate like wild-type cells but show a greatly impaired post-aggregative development. In addition, the expression of cell-type specific genes is very delayed, indicating that this protein plays an important role in cell differentiation and development. Cells expressing the MkpB catalytically inactive mutant show increased sensitivity to cisplatin, while cells over-expressing wild type MkpB, or MkpA, proteins or mutated in the MAP kinase erkB gene are more resistant to this chemotherapeutic drug, as also shown in human tumor cells. Submitted by Leandro Sastre [lsastre@iib.uam.es] -------------------------------------------------------------------------------- Legionella pneumophila infection is enhanced in a RacH-null mutant of Dictyostelium Alessandra Balest, Barbara Peracino and Salvatore Bozzaro Communicative and integrative Biology, in press Recently we reported that Dictyostelium cells ingest Legionella pneumophila by macropinocytosis, whereas other bacteria, such as Escherichia coli, Mycobacterium avium, Neisseria meningitidis or Salmonella typhimurium, are taken up by phagocytosis.1 In contrast to phagocytosis, macropinocytosis is partially inhibited by PI3K or PTEN inactivation, whereas both processes are sensitive to PLC inhibition. Independently from reduced uptake, L. pneumophila proliferates more efficiently in PI3K-null than in wild type cells. PI3K inactivation also overcomes the resistance to infection conferred by constitutively expressing the endo-lysosomal iron transporter Nramp1. We have shown this to be due to altered recruitment of the V-H+ ATPase, but not Nramp1, in the Legionella- containing vacuole (LCV) early during infection.1 As further evidence for impaired LCV acidification we examine here the effects of disrupting the small G protein RacH on Legionella infection. Submitted by: salvatore bozzaro [salvatore.bozzaro@unito.it] ============================================================== [End dictyNews, volume 36, number 5]