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Vol. 17, Issue 1, 511-524, January 2006
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Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045
Submitted July 28, 2005;
Accepted October 12, 2005
Monitoring Editor: Sean Munro
The trans-Golgi matrix consists of a group of proteins dynamically associated with the trans-Golgi and thought to be involved in anterograde and retrograde Golgi traffic, as well as interactions with the cytoskeleton and maintenance of the Golgi structure. GMx33 is localized to the cytoplasmic face of the trans-Golgi and is also present in a large cytoplasmic pool. Here we demonstrate that GMx33 is dynamically associated with the trans-Golgi matrix, associating and dissociating with the Golgi in seconds. GMx33 can be locked onto the trans-Golgi matrix by GTP
S, indicating that its association is regulated in a GTP-dependent manner like several other Golgi matrix proteins. Using live-cell imaging we show that GMx33 exits the Golgi associated with tubules and within these tubules GMx33 segregates from transmembrane proteins followed by fragmentation of the tubules into smaller tubules and vesicles. Within vesicles produced by an in vitro budding reaction, GMx33 remains segregated in a matrixlike tail region that sometimes contains Golgin-245. This trans-matrix often links a few vesicles together. Together these data suggest that GMx33 is a member of the trans-Golgi matrix and offer clues regarding the role of the trans-Golgi matrix in sorting and exit from the Golgi.
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The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).
* Present address: Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239
Present address: Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
Present address: Boulder Laboratory for 3D Electron Microscopy of Cells, Department of MCD Biology, University of Colorado, Boulder, CO 80309.
Address correspondence to: Kathryn E. Howell (kathryn.howell{at}uchsc.edu).
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