Distribution of membrane glyco proteins among the organelles of a single identified neuron of aplysia 2. isolation and characterization of glyco protein associated with vesicles
Ambron, R.T.; Sherbany, A.A.; Schwartz, J.H.
Brain Research 207(1): 33-48
ISSN/ISBN: 0006-8993 DOI: 10.1016/0006-8993(81)90677-6
Glycoprotein-I (MW 180,000) is associated with a vesicle fraction from the cytoplasm of R2, the giant cholinergic neuron in the abdominal ganglion. EM has shown that R2 contains lucent and compound vesicles. Anisomycin, an inhibitor of protein synthesis, provided evidence that Component-I is a constituent of somatic compound vesicles. In the presence of the drug, [3H]N-acetylgalactosamine injected into R2 is incorporated almost exclusively into Component-I. Quantitative EM radioautography of treated cells shows a marked increase in the proportion of silver grains over compound vesicles and a decrease in labeling of other organelles compared with untreated cells. Analysis of Component-I, isolated using the chaotropic agent lithium diiodosalicylate, shows it to contain fucose, N-acetylgalactosamine and N-acetylglucosamine. Proteolytic digestion with pronase yields a complex pattern of glycopeptides. The proportion of [3H]N-acetylgalactosamine in these glycopeptides is altered in the presence of anisomycin. These results together with radioautographic analyses suggest that large carbohydrate chains are elaborated within the endoplasmic reticulum and that smaller chains are added in the Golgi region or on the membrane of the compound vesicle.