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 [log in to unmask]
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 [[log in to unmask]]
———————————————————————————————————————


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 [[log in to unmask]]
==============================================================
[End dictyNews, volume 42, number 12]