The Dynamics of Golgi Enzymes in Mammalian Cells Supports Cisternal Maturation

Rizzo, Ricardo (2014). The Dynamics of Golgi Enzymes in Mammalian Cells Supports Cisternal Maturation. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f05b

Abstract

The Golgi apparatus is organised as a ‘ribbon’ of interconnected stacks of membranous cisternae that have characteristic enzyme compositions that define where cargo proteins are glycosylated during their transport towards the plasma membrane in mammalian cells. There are two classes of Golgi transport schemes: one based on stable cisternae, and the other on ‘maturing’ cisternae. With the stable cisternae model, the Golgi resident proteins (e.g., glycosylating enzymes) always remain in the same cisterna and the secretory cargo is transported forwards in vesicles, to move progressively from one cisterna to the next. According to the maturation scheme, new cisternae form at the cis-Golgi face, and then ‘move forward’ through the stack; at the same time, the cisternae ‘mature’ by acquiring, and then losing, the glycosylating enzymes, which recycle backwards in step with cargo progression. Here, the cargo remains stable within the cisterna, and is transported forwards within the advancing cisternae. While the maturation mechanism has significant experimental support, the crucial evidence that Golgi enzymes recycle through the stack in mammalian cells remains missing. In the present study, I designed experiments based on the use of Golgi-resident enzyme constructs that can be reversibly polymerised to distinguish the maturing versus stable cisternae models. The data strongly fit with the predictions of the cisternal maturation model.

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