Golgi enzymes are enriched in perforated zones of golgi cisternae but are depleted in COPI vesicles.
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.
Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, 66030 Santa Maria Imbaro (Chieti), Italy.
Hee-Seok
HS
Kweon
Galina V
GV
Beznoussenko
Massimo
M
Micaroni
Roman S
RS
Polishchuk
Alvar
A
Trucco
Oliviano
O
Martella
Daniele
D
Di Giandomenico
Pierfrancesco
P
Marra
Aurora
A
Fusella
Alessio
A
Di Pentima
Eric G
EG
Berger
Willie J C
WJ
Geerts
Abraham J
AJ
Koster
Koert N J
KN
Burger
Alberto
A
Luini
Alexander A
AA
Mironov
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D022181:COP-Coated Vesicles / Q000201:enzymology*; D002474:Cell-Free System; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology; D006056:Golgi Apparatus / Q000201:enzymology* / Q000648:ultrastructure*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D046529:Microscopy, Electron, Transmission; D051381:Rats