Intact ArfGAP function is required for the generation of COPI vesicles.
Stephen Lewis (1), Pak Phi Poon (1), Richard Singer (2), Gerald Johnston (1), Anne Spang (3)
(1) Microbiology & Immunology, Dalhousie University, 5850 College Street, Halifax, NS, B3H 1X5, Canada;
(2) Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 1X5, Canada;
(3) Friedrich Miescher Laboratorium, Max-Planck-Gesellschaft, Spemannstrasse 39 D-72076, Tubingen, Germany
The small GTPase Arf and the heptameric coatomer complex (COPI) are required for the generation of retrograde transport vesicles. Arf activity for vesicular transport is regulated by Arf guanine exchange factors (ArfGEFs) and Arf GTPase-activating proteins (ArfGAPs). The Saccharomyces cerevisiae ArfGAPs Gcs1 and Glo3 have been shown to provide essential overlapping function for retrograde vesicular transport from the Golgi apparatus to the endoplasmic reticulum. In this study, we have investigated previously identified protein-protein interactions between the Glo3 ArfGAP and the coatomer proteins Sec21 (gamma-COP) and Sec27 (beta'-COP), and have found that Glo3 is a component of COPI vesicles. Furthermore, we find that a Glo3 protein lacking measurable ArfGAP activity exerts a negative effect on retrograde transport, even in the presence of the Gcs1 ArfGAP. Finally, we present evidence supporting a role for ArfGAP function in the generation of COPI retrograde transport vesicles.
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