Dicty News Electronic Edition Volume 22, number 2 January 30, 2004 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 ============= Developmental cell death in Dictyostelium does not require paracaspase. Roisin-Bouffay C, Luciani MF, Klein G, Levraud JP, Adam M, Golstein P. Centre d'Immunologie de Marseille-Luminy, INSERM-CNRS-Univ.Med., 13288 Marseille cedex 9. J Biol Chem. 2003 Dec 17 [Epub ahead of print], 2004 in press Apoptotic cell death often requires caspases. Caspases are part of a family of related molecules including also paracaspases and metacaspases. Are molecules of this family generally involved in cell death ? More specifically, do non-apoptotic caspase-independent types of cell death require para- or metacaspases ? Dictyostelium discoideum lends itself well to answering these questions, since (1) it undergoes non-apoptotic developmental cell death, of a vacuolar autophagic type, and (2) it bears neither caspase nor metacaspase genes and apparently only one paracaspase gene. This only paracaspase gene can be inactivated by homologous recombination. Paracaspase-null clones were thus obtained in each of four distinct Dictyostelium strains. These clones were tested in two systems, developmental stalk cell death in vivo and vacuolar autophagic cell death in a monolayer system mimicking developmental cell death. Compared to parent cells, all paracaspase-null cells showed unaltered cell death, in both test systems. In addition, paracaspase inactivation led to no alteration in development or interaction with a range of bacteria. Thus, in Dictyostelium, vacuolar programmed cell death in development and in a monolayer model in vitro would seem not to require paracaspase. To our knowledge, this is the first instance of developmental, programmed cell death shown to be independent of any caspase, para- or metacaspase. These results have implications as to the relationship in evolution between cell death and the caspase family. Submitted by: Pierre Golstein [golstein@ciml.univ-mrs.fr] ----------------------------------------------------------------------------- Molecular engineering of a backwards-moving myosin motor Georgios Tsiavaliaris, Setsuko Fujita-Becker, & Dietmar J. Manstein Nature, in press All members of the diverse myosin superfamily have a highly conserved globular motor domain that contains the actin and nucleotide binding sites and produces force and movement. The light chain binding domain connects the motor domain to a variety of functionally specialized tail domains and amplifies small structural changes in the core motor domain via rotation of a lever arm. Myosins move on polarised actin filaments either forwards to the barbed (+) or backwards to the pointed (-) end. Here, we describe the engineering of an artificial backwards moving myosin from three pre-existing molecular building blocks: a forward-moving class I myosin motor domain, a directional inverter formed by a 4-helix bundle segment of human guanylate binding protein-1, and an artificial lever arm formed by two a-actinin repeats. Our results prove that reverse-direction movement of myosins can be achieved simply by rotating the direction of the lever arm 180¡. Submitted by: Dietmar Manstein [Manstein.Dietmar@mh-hannover.de] ----------------------------------------------------------------------------- Calmodulin-dependent cyclic nucleotide phosphodiesterase (PDE1) is a pharmacological target of DIF-1, an anti-tumor agent isolated from Dictyostelium Kasumi Shimizu, Taku Murata, Toshiro Tagawa, Katsunori Takahashi, Ryoki Ishikawa, Yumiko Abe, Kohei Hosaka, and Yuzuru Kubohara* *Biosignal Research Center, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, Maebashi 371-8512, Japan. Accepted for publication in Cancer Research Abstract The differentiation-inducing factor-1 (DIF-1) isolated from Dictyostelium discoideum is a potent anti-proliferative agent that induces growth arrest and differentiation in mammalian cells in vitro. However, the specific target molecule(s) of DIF-1 has not been identified. In this study, we have tried to identify the target molecule(s) of DIF-1 in mammalian cells, examining the effects of DIF-1 and its analogs on the activity of some candidate enzymes. DIF-1 at 10-40 micro M dose-dependently suppressed cell growth and increased the intracellular cAMP concentration in K562 leukemia cells. It was then found that DIF-1 at 0.5-20 micro M inhibited the calmodulin (CaM)-dependent cyclic nucleotide phosphodiesterase (PDE1) in vitro in a dose-dependent manner. Kinetic analysis revealed that DIF-1 acted as a competitive inhibitor of PDE1 versus the substrate cAMP. Since DIF-1 did not significantly affect the activity of other PDEs or CaM-dependent enzymes and, in addition, an isomer of DIF-1 was a less potent inhibitor, we have concluded that PDE1 is a pharmacological and specific target of DIF-1. Submitted by: Yuzuru Kubohara [kubohara@showa.gunma-u.ac.jp] =============================================================================== [End Dicty News, volume 22, number 2]