REGULATION OF MUCIN GLYCOPROTEIN BIOSYNTHESIS

O-糖基化代表粘蛋白的关键功能决定簇， 这种糖蛋白赋予粘液层独特的保护作用， 的天性. 然而，在我们对这一问题的理解上， 调节O-糖基化起始的事件。 之甚少 已知粘蛋白（脱粘蛋白）的蛋白质核心的表达 是被控制的 我们假设脱粘蛋白的表达是 以组织特异性方式调节， 变异蛋白质核心的糖基化有助于异质性 在粘蛋白结构中观察到。 为了验证这一假设，我们建议 鉴定和表征编码RSMG脱粘蛋白cDNA。 这些cdna 将用于推导脱粘蛋白的氨基酸序列， 将被用作探针，以确定组织和细胞 编码粘蛋白的蛋白质核心的转录物的分布。 也不清楚为什么一些蛋白质变成O-糖基化，而 其他的则不会被修改。 我们假设O- 蛋白质内的糖基化由分子信号指导， 包含在mRNA编码的信息中， 糖蛋白的蛋白质核心。 为了验证这一假设，我们建议 表达血型糖蛋白A（一种充分表征的O-糖基化蛋白），或 富含谷氨酰胺/谷氨酸的蛋白质（缺乏 糖）在异源细胞系（中国人卵巢细胞）中的表达 并确定每个重组体中哪些潜在的受体位点 分子被糖基化。 特定序列和构象 血型糖蛋白A和谷氨酰胺/谷氨酸富集蛋白的结构域将 测定它们促进或抑制O-糖基化的能力。 这些研究将使我们能够确定信号的性质 其指导O-糖基化。 这些信息将大大有助于 尝试通过重组来工程化生物活性O-糖基化蛋白 DNA方法。 此外，对正常的 O-糖基化的过程可以提供对特定形式的 被认为与粘蛋白畸变有关的病理学- 糖蛋白生物合成

O-glycosylation represents a crucial functional determinant of mucins, the glycoproteins which endow the mucus coat with its unique protective qualities. However, a critical gap remains in our understanding of the events which regulate the initiation of O-glycosylation. Little is known about how the expression of the protein core of mucin (apomucin) is controlled. We hypothesized that the expression of apomucin is regulated in a tissue-specific manner and that differential glycosylation of variant protein cores contributes to the heterogeneity observed in mucin structure. To test this hypothesis we propose to identify and characterize cDNAs which encode RSMG apomucin. These cDNAs will be used to deduce the amino acid sequence of the apomucin(s) and will be used as a probe to determine the tissue and cellular distribution of transcripts which encode the protein core of the mucin. It is also unclear why some proteins become O-glycosylated whereas others do not become modified. We hypothesize that the sites of O- glycosylation within a protein are directed by molecular signals which are embodied within the information contained in the mRNA encoding the protein core of the glycoprotein. To test this hypothesis we propose to express glycophorin A (a well-characterized O-glycosylated protein), or glutamine/glutamic acid-rich protein (a protein which is devoid of saccharide) in a heterologous cell line (Chinese Hamster Ovary cells) and determine which potential acceptor sites in each recombinant molecule become glycosylated. Specific sequence and conformational domains of glycophorin A and glutamine/glutamic acid-rich protein will be assayed for their ability to promote or inhibit O-glycosylation. These studies will enable us to determine the nature of the signals which direct O-glycosylation. This information would greatly facilitate attempts to engineer bioactive O-glycosylated proteins by recombinant DNA methods. In addition, a more thorough understanding of the normal process of O-glycosylation may provide insight into specific forms of pathology which are thought to be related to aberrations of mucin- glycoprotein biosynthesis.