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dictyNews Volume 42 Number 12
dictyNews
Electronic Edition
Volume 42, number 12
April 22, 2016
Please submit abstracts of your papers as soon as they have been
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or by using the form at
http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit.
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Abstracts
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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]
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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]
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[End dictyNews, volume 42, number 12]
