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Vol. 18, Issue 4, 1261-1271, April 2007
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Department of Biochemistry and Cell Biology and Institute of Biomembranes, Utrecht University, 3508 TD Utrecht, The Netherlands; *Biochemie-Zentrum Heidelberg, University of Heidelberg, 69120 Heidelberg, Germany;
Institut des Maladies Infectieuses, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland; ||Department of Cell Biology, University Medical Center and Institute for Biomembranes, 3584 CX Utrecht, The Netherlands; ¶Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany; and #Cell Biology and Biophysics Programme, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
Submitted March 27, 2006;
Revised December 22, 2006;
Accepted January 12, 2007
Monitoring Editor: Vivek Malhotra
The Golgi apparatus consists of a series of flattened cisternal membranes that are aligned in parallel to form stacks. Cytosolic-oriented Golgi-associated proteins have been identified that may coordinate or maintain the Golgi architecture. Here, we describe a novel GPI-anchored protein, Golgi-resident GPI-anchored protein (GREG) that has a brefeldin A-sensitive Golgi localization. GREG resides in the Golgi lumen as a cis-oriented homodimer, due to strong interactions between coiled-coil regions in the C termini. Dimerization of GREG as well as its Golgi localization depends on a unique tandem repeat sequence within the coiled-coil region. RNA-mediated interference of GREG expression or expression of GREG mutants reveals an essential role for GREG in maintenance of the Golgi integrity. Under these conditions, secretion of the vesicular stomatitis virus glycoprotein protein as a marker for protein transport along the secretory pathway is inhibited, suggesting a loss of Golgi function as well. These results imply the involvement of a luminal protein in Golgi structure and function.
The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).
Present address: Laboratory of Cellular Neurobiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129.
Address correspondence to: J. Bernd Helms (j.b.helms{at}vet.uu.nl)
Abbreviations used: GIC, Golgi-derived detergent-insoluble complex; GREG, Golgi-resident GPI-anchored protein.