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Beta-COP localizes mainly to the cis-Golgi side in exocrine pancreas.
- Source :
-
The Journal of cell biology [J Cell Biol] 1993 Apr; Vol. 121 (1), pp. 49-59. - Publication Year :
- 1993
-
Abstract
- We examined the distribution of the non-clathrin-coated vesicle-associated coat protein beta-COP in rat exocrine pancreatic cells by immunogold cytochemistry. Labeling for beta-COP was found in the Golgi region (48%) where it was associated with vesicles and buds of approximately 50 nm, showing a characteristic approximately 10-nm-thick coat. The other half of the label was present in the cytoplasm, not associated with visible coats or membranes, with a minor fraction present on small clusters of tubules and vesicles. Clathrin-coated vesicles were typically located at the trans-side of the Golgi complex, and showed a thicker coat of approximately 18 nm. Of the total beta-COP labeling over the Golgi region, 68% occurred on the cis-side, 6% on the cisternae, 17% on the rims of the cisternae, and only 9% on the trans-side. For clathrin these figures were 16, 2, 4, and 78%, respectively. At the cis-Golgi side beta-COP was present in transitional areas (TA), on so-called peripheral elements (PE), consisting of tubules and vesicles located between the cup-shaped transitional elements (TE) of the RER and the cis-most Golgi cisternae. Label for Sec23p was also present in TA but was located closer to the TE, while beta-COP labeled PE were located near the cis-Golgi cisternae. Upon energy depletion, Golgi associated beta-COP was almost exclusively (86%) in spherical aggregates of 200-500 nm in diameter, whereas the cis-side (6%), the cisternae (1%), the rims (4%) and trans-side (3%) of the Golgi complex, were barely labeled; 50% of the total label remained in the cytoplasm. The aggregates were predominantly located at the cis-side of the Golgi stack, next to, but distinct from the Sec23p positive TA, that were devoid of beta-COP and had only a few recognizable vesicles left. Incubation with aluminum fluoride resulted in fragmentation of the Golgi complex into large clusters of beta-COP positive vesicles, while 50% of the label remained in the cytoplasm, as in control cells. After 10 min of Brefeldin A treatment 91% of beta-COP was cytoplasmic and only 7% associated with membranes of the Golgi complex. The total label for beta-COP over exocrine cells remained unchanged during the incubation with either of the drugs, indicating that the drugs induce reallocation of beta-COP. Our data suggest that beta-COP plays a role in membrane transport at the cis-side of the Golgi complex.
- Subjects :
- Aluminum pharmacology
Animals
Biological Transport
Brefeldin A
Clathrin analysis
Coatomer Protein
Cyclopentanes pharmacology
Energy Metabolism
Fluorides pharmacology
Male
Microscopy, Immunoelectron
Pancreas metabolism
Pancreas ultrastructure
Rats
Rats, Wistar
Aluminum Compounds
Golgi Apparatus chemistry
Membrane Proteins analysis
Microtubule-Associated Proteins analysis
Pancreas chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9525
- Volume :
- 121
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- The Journal of cell biology
- Publication Type :
- Academic Journal
- Accession number :
- 8458872
- Full Text :
- https://doi.org/10.1083/jcb.121.1.49