Golgi enzymes are enriched in perforated zones of golgi cisternae but are depleted in COPI vesicles |
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Authors: | Kweon Hee-Seok Beznoussenko Galina V Micaroni Massimo Polishchuk Roman S Trucco Alvar Martella Oliviano Di Giandomenico Daniele Marra Pierfrancesco Fusella Aurora Di Pentima Alessio Berger Eric G Geerts Willie J C Koster Abraham J Burger Koert N J Luini Alberto Mironov Alexander A |
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Institution: | Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, 66030 Santa Maria Imbaro (Chieti), Italy. |
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Abstract: | 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. |
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