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Golgi Enzymes Are Enriched in Perforated Zones of Golgi Cisternae but Are Depleted in COPI Vesicles

2004; American Society for Cell Biology; Volume: 15; Issue: 10 Linguagem: Inglês

10.1091/mbc.e03-12-0881

1939-4586

Hee-Seok Kweon, Galina V. Beznoussenko, Massimo Micaroni, Roman Polishchuk, Alvar Trucco, Oliviano Martella, Daniele Di Giandomenico, Pierfrancesco Marra, Aurora Fusella, Alessio Di Pentima, Eric G. Berger, Willie J. C. Geerts, Abraham J. Koster, Koert N.J. Burger, Alberto Luini, Alexander A. Mirоnоv,

Lipid Membrane Structure and Behavior

In the most widely accepted version of the cisternal maturation/progression model of intra-Golgi transport, the polarity of the Golgi complex is maintained by retrograde transport of Golgi enzymes in COPI-coated vesicles. By analyzing enzyme localization in relation to the three-dimensional ultrastructure of the Golgi complex, we now observe that Golgi enzymes are depleted in COPI-coated buds and 50- to 60-nm COPI-dependent vesicles in a variety of different cell types. Instead, we find that Golgi enzymes are concentrated in the perforated zones of cisternal rims both in vivo and in a cell-free system. This lateral segregation of Golgi enzymes is detectable in some stacks during steady-state transport, but it was significantly prominent after blocking endoplasmic reticulum-to-Golgi transport. Delivery of transport carriers to the Golgi after the release of a transport block leads to a diminution in Golgi enzyme concentrations in perforated zones of cisternae. The exclusion of Golgi enzymes from COPI vesicles and their transport-dependent accumulation in perforated zones argues against the current vesicle-mediated version of the cisternal maturation/progression model.