dictyNews Electronic Edition Volume 42, number 12 April 22, 2016 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 ========= Dictyostelium discoideum RabS and Rab2 Colocalize with Golgi and Contractile Vacuole System and Regulate Osmoregulation Katherine Maringer, Azure Yarbrough, Sunder Sims-Lucas, Entsar Saheb, Sanaa Jawed, and John Bush Journal of Biosciences, in press Small molecular weight GTPase Rab2 has been shown to be a resident of pre-Golgi intermediates and required for protein transport from the ER to the Golgi complex; however, Rab2 has yet to be characterized in Dictyostelium discoideum. DdRabS i s a Dictyostelium Rab that is 80% homologous to DdRab1 which is required for protein transport between the ER and Golgi. Expression of GFP-tagged DdRab2 and DdRabS proteins showed localization to Golgi membranes and to the contractile vacuole system (CV) in Dictyostelium. Microscopic imaging indicates that the DdRab2 and DdRabS proteins localize at, and are essential for, the proper structure of Golgi membranes and the CV system. Dominant negative (DN) forms show fractionation of Golgi membranes supporting their role in the structure and function of it. DdRab2 and DdRabS proteins, and their dominant negative and constitutively active (CA) forms, affect osmoregulation of the cells, possibly by the influx and discharge of fluids, which suggests a role in the function of the CV system. This is the first evidence of GTPases being localized to both Golgi membranes and the CV system in Dictyostelium. submitted by: Azure Yarbrough [alyarbrough@ualr.edu] ——————————————————————————————————————— The small GTPases Ras and Rap1 bind to and control TORC2 activity Ankita Khanna*, Pouya Lotfi*, Anita J. Chavan, Nieves M. Montaño, Parvin Bolourani, Gerald Weeks, Zhouxin Shen, Steven P. Briggs, Henderikus Pots, Peter J.M Van Haastert, Arjan Kortholt & Pascale G. Charest. *equal contribution Scientific Reports, in press. Target of Rapamycin Complex 2 (TORC2) has conserved roles in regulating cytoskeleton dynamics and cell migration and has been linked to cancer metastasis. However, little is known about the mechanisms regulating TORC2 activity and function in any system. In Dictyostelium, TORC2 functions at the front of migrating cells downstream of the Ras protein RasC, controlling F-actin dynamics and cAMP production. Here, we report the identification of the small GTPase Rap1 as a conserved binding partner of the TORC2 component RIP3/SIN1, and that Rap1 positively regulates the RasC- mediated activation of TORC2 in Dictyostelium. Moreover, we show that active RasC binds to the catalytic domain of TOR, suggesting a mechanism of TORC2 activation that is similar to Rheb activation of TOR complex 1. Dual Ras/Rap1 regulation of TORC2 may allow for integration of Ras and Rap1 signaling pathways in directed cell migration. submitted by: Pascale Charest [pcharest@email.arizona.edu] ============================================================== [End dictyNews, volume 42, number 12]