The Golgi ribbon structure facilitates anterograde transport of large cargoes.
Bottom Line: Yet the purpose of this remarkable structure has been an enigma.In addition, insect cells that naturally harbor dispersed Golgi stacks have limited capacity to transport artificial oversized cargoes.These results imply that the ribbon structure is an essential requirement for transport of large cargoes in mammalian cells, and we suggest that this is because it enables the dilated rims of cisternae (containing the aggregates) to move across the stack as they transfer among adjacent stacks within the ribbon structure.
Affiliation: Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520 firstname.lastname@example.org email@example.com.Show MeSH
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Mentions: The cargo used above was artificially aggregated and may not perfectly reflect the behavior of physiologically large cargoes. Collagen I, an abundant component of the extracellular matrix, is an example of a physiological large cargo (Ricard-Blum, 2011). We repeated our experiments using Saos-2 cells that secrete endogenous collagen I (Saito et al., 2009; Lavieu et al., 2013). We took advantage of the ascorbate-dependent folding of collagen to control the wave of collagen secretion (Harwood et al., 1976; Mironov et al., 2001). Cells were cultured overnight in ascorbate-depleted media to block collagen within the ER and then, during the last 2 h, cells were pretreated with nocodazole before ascorbate was added back to allow for collagen folding and subsequent exit from the ER. We then assessed the secretion of endogenous collagen I (large cargo) and endogenous MMP2 (small cargo) simultaneously within the same samples. This allows for the direct comparison of the secretion rates of the two endogenous cargoes using a bulk biochemical secretion assay that leaves no room for biased interpretation. The rate of secretion of collagen I was strongly diminished (70% reduction) in the presence of nocodazole, whereas the secretion of MMP-2 was not altered by more than 20% (Figure 3, A and B).
Affiliation: Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520 firstname.lastname@example.org email@example.com.