Abstract
The Golgi apparatus in mammalian cells is composed of flattened cisternae that are densely packed to form stacks. We have used the Golgi stacking protein GRASP65 as a tool to modify the stacking state of Golgi cisternae. We established an assay to measure protein transport to the cell surface in post-mitotic cells in which the Golgi was unstacked. Cells with an unstacked Golgi showed a higher transport rate compared to cells with stacked Golgi membranes. Vesicle budding from unstacked cisternae in vitro was significantly increased compared to stacked membranes. These results suggest that Golgi cisternal stacking can directly regulate vesicle formation and thus the rate of protein transport through the Golgi. The results further suggest that at the onset of mitosis, unstacking of cisternae allows extensive and rapid vesiculation of the Golgi in preparation for its subsequent partitioning.
Highlights
Proteins and lipids are exchanged between Golgi cisternae by transient tubular connections and vesicles that form at the rims of one cisterna and fuse with the in the secretory pathway [1,2,3]
In this study we investigated the biological role of Golgi cisternal stacking in the regulation of protein transport through the Golgi
The data presented here indicate that vesicles form more efficiently from unstacked cisternae, leading to an increased rate of protein transport through the Golgi apparatus to the cell surface
Summary
Proteins and lipids are exchanged between Golgi cisternae by transient tubular connections and vesicles that form at the rims of one cisterna and fuse with the in the secretory pathway [1,2,3]. Trafficking through the Golgi may be mediated by cisternal maturation, or vesicular transport [4,5,6]. The maturation model proposes that cargo is transported by modification of the cisternae, while Golgi enzymes are recycled via retrograde transport of COPI vesicles. In the vesicular transport model, Golgi cisternae remain stable and cargo is transported through them by COPI vesicles. In both cases, the budding rate of vesicles determines the rate of transport across the Golgi [7]. In the vesicular transport model, vesicles carry cargo while in the maturation model, vesicles are essential to maintain the correct location of Golgi resident proteins
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