Dicty News Electronic Edition Volume 24, number 9 April 8, 2005 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 Dicty-News, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. ============= Abstracts ============= Sphingosine-1-phosphate lyase regulates sensitivity of human cells to select chemotherapy drugs in a p38-dependant manner Junxia Min1, Paul P. Van Veldhoven2, Lei Zhang3, Marie H. Hanigan4, Hannah Alexander1 and Stephen Alexander1* 1Division of Biological Sciences, University of Missouri, Columbia, MO 6521-7400 2Katholieke Universiteit Leuven, Departement Moleculaire Celbiologie, Afdeling Farmakologie, B-3000 Leuven, Belgium. 3Tufts University, New England Medical Center, Boston, MA 4Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73190. Molecular Cancer Research, in press Resistance to cisplatin is a common problem that limits its usefulness in cancer therapy. Molecular genetic studies in the model organism Dictyostelium discoideum have established that modulation of sphingosine kinase or sphingosine-1-phosphate (S-1-P) lyase, by disruption or overexpression, results in altered cellular sensitivity to this widely used drug. Parallel changes in sensitivity were observed for the related compound carboplatin, but not for other chemotherapy drugs tested. Sensitivity to cisplatin could also be potentiated pharmacologically with dimethylsphingosine, a sphingosine kinase inhibitor. We now have validated these studies in cultured human cell lines. HEK293 or A549 lung cancer cells expressing human S-1-P lyase (hSPL) show an increase in sensitivity to cisplatin and carboplatin as predicted from the earlier model studies. The hSPL overexpressing (hSPL-OE) cells were also more sensitive to doxorubicin but not vincristine or chlorambucil. Studies using inhibitors to specific MAP kinases show that the increased cisplatin sensitivity in the hSPL-OE cells is mediated by p38, and to a lesser extent by JNK MAPKs. p38 is not involved in vincristine or chlorambucil cytotoxicity. Measurements of MAPK phosphorylation and enzyme activity, as well as siRNA inhibition studies, show that the response to the drug is accompanied by up-regulation of p38 and JNK and the lack of ERK up-regulation. These studies confirm an earlier model proposing a mechanism for the drug specificity observed in the studies with D. discoideum, and supports the idea that the sphingosine kinases and S-1-P lyase are potential targets for improving the efficacy of cisplatin therapy for human tumors. Submitted by: Steve Alexander [AlexanderSt@missouri.edu] ----------------------------------------------------------------------------- Evolutionary origin of cAMP-based chemoattraction in the social amoebae Elisa Alvarez-Curto1, Daniel E. Rozen1,3, Alysson V. Ritchie1, Celine Fouquet1 Sandra L. Baldauf2 and Pauline Schaap1*. 1School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK 2Department of Biology, University of York, PO Box 373, York YO10 5YW, UK 3Current address: Department of Biology, Emory University, 1510 Clifton Road, Atlanta, GA 30322, USA *Corresponding author: School of Life Sciences, University of Dundee MSI/WTB complex, Dundee DD1 5EH, UK; Phone: 44 1382 348078; Fax: 44 1382 345386; E-mail:p.schaap@dundee.ac.uk Proc. Natl. Acad. Sci. USA, in press. Phenotypic novelties can arise if integrated developmental pathways are expressed at new developmental stages and are then recruited to serve new functions. We analyse the origin of a novel developmental trait of Dictyostelid amoebae: the evolution of cAMP as a developmental chemoattractant. We show that cAMP's role to attract starving amoebae arose through recruitment of a pathway that originally evolved to coordinate fruiting body morphogenesis. Orthologues of the high-affinity cAMP receptor, cAR1, were identified in a selection of species that span the Dictyostelid phylogeny. The cAR1 orthologue from the basal species D.minutum restored aggregation and development when expressed in an aggregation-defective mutant of the derived species D.discoideum that lacks high-affinity cARs, thus demonstrating that the D. minutum cAR is a fully functional cAMP receptor. cAR1 orthologues from basal species are expressed during fruiting body formation and only this process, and not aggregation, was disrupted by abrogation of cAR1 function. This is in contrast to derived species, where cAR1 is also expressed during aggregation and critically regulates this process. Our data show that coordination of fruiting body formation is the ancestral function of extracellular cAMP signalling, while its derived role in aggregation evolved by recruitment of a pre-existing pathway to an earlier stage of development. This most likely occured by addition of distal cis-regulatory regions to existing cAMP signaling genes. Submitted by: Pauline Schaap [p.schaap@dundee.ac.uk] ============================================================================== [End Dicty News, volume 24, number 9]