Cloning and Subcellular Localization of GalNAc Transferase

1.我们已经获得了一个cDNA克隆的人类同源的UDP-N-乙酰半乳糖胺：多肽N-乙酰半乳糖胺转移酶（GalNAc转移酶）。人GalNAc转移酶的AcDNA序列与牛的同源性较高，与最近发现的人同工酶T1完全相同.根据获得的cDNA序列合成了23个氨基酸残基的多肽，并成功制备了抗该多肽的鼠单克隆抗体（GNT-1）. GNT-1与胰腺、唾液腺、支气管腺和乳腺等外分泌器官的导管上皮细胞反应。GNT-1与唾液腺和胃粘液细胞无反应性。这些结果表明，导管上皮细胞和粘液细胞具有不同类型的GalNAc转移酶。值得注意的是，胃壁细胞和胰腺Langerhans岛的大量细胞与GNT-1有良好的反应性，提示这些细胞除了产生粘蛋白外，还产生O-糖基化蛋白. GNT-1蛋白免疫印迹结果显示GalNAc转移酶T1的表达不仅在不同的器官类型和细胞类型之间存在差异，而且在不同的细胞分化程度之间也存在差异

1. We have obtained a cDNA clone of the human homologue of the UDP-N-acctylgalactosamine : polypeptide N-acetylgalactosaminyltransferase (GalNAc transferase). AcDNA sequence for human GalNAc transferase showed high homology with its bovine homelogue and was identical to human isozyme Tlthat was recently reported.2. Twenty-three residues peptide was synthesized based on the obtained cDNA sequence and a mouse monoclonal antibody to the peptide (GNT-1) was successfully produced.3. GNT-1 reacted with ductal epithelial cells of the exocrine organs including pancreas, salivary gland, bronchial gland, and mammary gland. Oherewise, GNT-1 had no reactivity with mucus cells of salivary gland and stomach. These results suggest that ductal epithelial cells and mucus cells have different types of GalNAc transferase. It was noteworthy that parietal cells of stomach and a large number of cells in Langerhans islands of pancreas showed nice reactivity with GNT-1, suggesting these cells produce O-glycosylated protein except for mucin.4. Western immunoblotting with GNT-1 showed that the expression of GalNAc transferase T1 varies not only among organ types and cell type, but also according to cell differentiation.5.Based on the results deceribed above, we plan to study the expression of GalNAc transferase T1 in various kinds of gastrointstinal disease and produce a monoclonal antibody to GalNAc transferase T2