Abstract
It is unclear how the two principal functions of the Golgi complex, processing and transport, are spatially organized. Studying such spatial organization by optical imaging is challenging, partially due to the dense packing of stochastically oriented Golgi stacks. Using super-resolution microscopy and markers such as Giantin, we developed a method to identify en face and side views of individual nocodazole-induced Golgi mini-stacks. Our imaging uncovered that Golgi enzymes preferentially localize to the cisternal interior, appearing as a central disk or inner-ring, whereas components of the trafficking machinery reside at the periphery of the stack, including the cisternal rim. Interestingly, conventional secretory cargos appeared at the cisternal interior during their intra-Golgi trafficking and transiently localized to the cisternal rim before exiting the Golgi. In contrast, bulky cargos were found only at the rim. Our study therefore directly demonstrates the spatial separation of processing and transport functions within the Golgi complex.
Highlights
The Golgi complex is one of the most important processing and sorting stations along the secretory and endocytic pathway (Glick and Luini, 2011; Klumperman, 2011; Lu and Hong, 2014)
GPP130 and Golgin84 localize to the cisternal rim of the Golgi mini-stack
We found that the orientation of a mini-stack can be identified by Golgi markers, such as Giantin, Golgin84 and GPP130
Summary
The Golgi complex is one of the most important processing and sorting stations along the secretory and endocytic pathway (Glick and Luini, 2011; Klumperman, 2011; Lu and Hong, 2014). In mammalian cells, it consists of a network of laterally linked Golgi stacks. It has been hypothesized that the two principal functions of the Golgi, processing and transport, are spatially organized for optimal efficiency (Patterson et al, 2008) Such molecular organization across the Golgi stack has not been directly demonstrated. We found that Golgi enzymes and components of trafficking machinery are spatially separated to the interior and periphery, respectively, of the Golgi stack, while secretory cargos with bulky sizes are excluded from the interior during their intra-Golgi transition
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