dictyNews Electronic Edition Volume 37, number 11 November 4, 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 ========= Dynamin A, Myosin IB and Abp1 couple phagosome maturation to F-actin binding Navin Gopaldass, Devang Patel, Ramona Kratzke, Regis Dieckmann, Stephanie Hausherr, Monica Hagedorn, Roger Monroy, Julia Krueger, Eva M. Neuhaus, Eik Hoffmann, Katja Hille, Sergei A. Kuznetsov and Thierry Soldati Traffic, in press The role of actin, class I myosins and dynamin in endocytic uptake processes is well characterized, but their role during endo-phagosomal membrane trafficking and maturation is less clear. In Dictyostelium, knock out of Myosin IB leads to a defect in membrane protein recycling from endosomes back to the plasma membrane. Here, we show that actin plays a central role in the morphology and function of the endocytic pathway. Indeed, Latrunculin B induces endosome tubulation, a phenotype also observed in dynamin A-null cells. Knock out of Dynamin A impairs phagosome acidification whereas knock out of Myosin IB delays re-neutralisation, a phenotype mimicked by a low dose of Latrunculin B. As a read out for actin-dependent processes during maturation, we monitored the capacity of purified phagosomes to bind F-actin in vitro, and correlated this with the presence of actin-binding and membrane trafficking proteins. Phagosomes isolated from myoB-null cells showed increased binding to F-actin, especially late phagosomes. In contrast, early phagosome from dymA-null cells showed reduced binding to F-actin while late phagosomes were unaffected. We provide evidence that Abp1 is the main F-actin binding protein in this assay and is central for the interplay between Dynamin A and Myosin IB during phagosome maturation. Submitted by Thierry Soldati [thierry.soldati@unige.ch] -------------------------------------------------------------------------------------- Amoeboid cells use protrusions for walking, gliding and swimming Peter J.M. Van Haastert Department of Cell Biochemistry, University of Groningen, Nijenborg 7, 9747AG Groningen, The Netherlands PLoS One, in press Amoeboid cells crawl using pseudopods, which are convex extensions of the cell surface. In many laboratory experiments, cells move on a smooth substrate, but in the wild cells may experience obstacles of other cells or dead material, or may even move in liquid. To understand how cells cope with heterogeneous environments we have investigated the pseudopod life cycle of wild type and mutant cells moving on a substrate and when suspended in liquid. We show that the same pseudopod cycle can provide three types of movement that we address as walking, gliding and swimming. In walking the extending pseudopod will adhere firmly to the substrate, which allows cells to generate forces to bypass obstacles. Mutant cells with compromised adhesion can move much faster than wild type cells on a smooth substrate (gliding), but can not move effectively against obstacles that provide resistance. In a liquid, when swimming, the extending pseudopods convert to side-bumps that move rapidly to the rear of the cells. Calculations suggest that these bumps provide sufficient drag force to mediate the observed forward swimming of the cell. Submitted by Peter Van Haastert [p.j.m.van.haastert@rug.nl] ============================================================== [End dictyNews, volume 37, number 11]