MG-160. A novel sialoglycoprotein of the medial cisternae of the Golgi apparatus [published eeratum appears in J Biol Chem 1989 Mar 5;264(7):4264]

• Published in: The Journal of biological chemistry Vol. 264; no. 1; pp. 646 - 653
• Main Authors: Gonatas, J O, Mezitis, S G, Stieber, A, Fleischer, B, Gonatas, N K
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 05-01-1989
• Subjects: Adrenal Gland Neoplasms - ultrastructure; Animals; Antibodies, Monoclonal; Brain - ultrastructure; Cell Line; Enzyme-Linked Immunosorbent Assay; Golgi apparatus; Golgi Apparatus - ultrastructure; Liver - ultrastructure; Microscopy, Electron; Neurons - ultrastructure; Pheochromocytoma - ultrastructure; pheochromocytoma cells; Pituitary Gland, Anterior - ultrastructure; Rats; Sialoglycoproteins - analysis; Sialoglycoproteins - immunology
• ISSN: 0021-9258; 1083-351X

A monoclonal antibody (mAb 10A8), derived from mice immunized with fractions of the Golgi apparatus from rat brain neurons,
was exploited to isolate and partially characterize a novel glycoprotein of 160 kDa apparent molecular mass which was localized
by immunoelectron microscopy in medial cisternae of the Golgi apparatus of neurons, glia, pituitary cells, and rat pheochromocytoma
(PC 12). The yield of immunoaffinity purified protein was 0.9 microgram/g of rat brain and represented 3% of the Golgi protein;
the protein contained asparagine-linked carbohydrates and sialic acid and N-acetylglucosamine residues; unreduced protein
had a greater electrophoretic mobility (130 kDa) consistent with the presence of intrachain disulfide bonds. The bulk of the
glycoprotein resided within the membrane and/or luminal face of the Golgi cisternae. After extraction with Triton X-114, the
glycoprotein was found in both aqueous and detergent phases. The monoclonal antibody did not inhibit the activities of Golgi
enzymes or the uptake of nucleotide sugars by intact Golgi vesicles. The findings indicate that the 160-kDa glycoprotein is
a specific constituent of medial Golgi cisternae. The results of this study lend support to the hypothesis that the distributions
of glycosyltransferases in the Golgi apparatus are cell specific, since in neurons this sialic acid containing glycoprotein
is found in medial rather than in trans and/or in the trans Golgi reticulum cisternae, where sialyltransferases have been
localized in other cells. Alternatively, resident neuronal Golgi sialoglycoproteins may acquire sialic acid in trans elements
of the apparatus and then shuttle back in medial cisternae.