Structure, Biosynthesis & Function of Glycoproteins

这项研究计划的目的是获得对磷酸甘露醇的分子理解。 靶向系统，作用于将新合成的酸性水解酶输送到溶酶体。 这种细胞内蛋白运输途径的缺陷会导致严重的溶酶体储存性疾病。一把钥匙 这一途径的步骤是甘露糖残基在高甘露糖链上的选择性磷酸化。 UDP-GlcNAc的酸性水解酶：溶酶体酶N-乙酰氨基葡萄糖-1-磷酸转移酶 (Ptase)。该转移酶是一种由两个基因编码的六聚体蛋白。我们证实，α/β亚基识别酸性水解酶的共同蛋白质决定因素，并介导 酶的催化功能。Y亚基增强了α/β亚基的活性，使其成为 酸性水解酶。具体目标1旨在确定结合的α/β亚基的结构域 酸性水解酶的蛋白质决定因素。目的2重点研究Man-6-P受体同源的作用 (MRH)-在增强a/p对选定的水解酶活性方面的伽马亚基的结构域。目标3 旨在了解阿尔法/贝塔基因缺失小鼠神经退行性变的生理学基础。目标4 目的是确定Ptase如何定位于顺式高尔基体小室。目标5是定义基本角色 GGA2(用于高尔基体定位、Y-EAR、ARF结合)外壳蛋白在维持新生儿中的表达 生存能力。此函数不能由GGA1和GGA3取代，从而确定GGA没有完全 多余的。这些研究将利用编码三种GGA的基因被破坏的小鼠。

The objective of this research proposal is to obtain a molecular understanding of the phosphomannosyl targeting system which functions In the delivery of newly synthesized acid hydrolases to lysosomes. Defects in this intracellular protein transport pathway give rise to severe lysosomal storage diseases. A key step in this pathway is the selective phosphorylation of mannose residues on the high mannose glycans of the acid hydrolases by UDP-GlcNAc: lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (Ptase). This transferase is an alpha2betagamma2 hexameric protein encoded by two genes. We established that the alpha/beta subunits recognize the common protein determinant of the acid hydrolases as well as mediating the catalytic function of the enzyme. The y subunit enhances the activity of the alpha/beta subunits toward a subset of the acid hydrolases. Specific Aim 1 is directed toward identifying the domain of the alpha/beta subunits that binds the protein determinant of the acid hydrolases. Aim 2 focuses on the role of the Man-6-P receptor homology (MRH)-domain of the gamma subunits in enhancing the activity of the a/p toward selected hydrolases. Aim 3 seeks to understand the physiologic basis for the development of neurodegeneration in alpha/beta null mice. Aim 4 is to determine how Ptase is localized to the cis-Golgi subcompartment. Aim 5 is to define the essential role of the GGA2 (for Golgi-localized, y-ear containing, ARF-binding) coat protein in maintaining neonatal viability. This function cannot be replaced by GGA1 and GGA3, establishing that the GGAs are not fully redundant. These studies will utilize mice with disruption of the genes encoding the three GGAs.