Structural elucidation of the N- and O-glycans of human apolipoprotein(a) -: Role of O-glycans in conferring protease resistance
Structural elucidation of the N- and O-glycans of human apolipoprotein(a) -: Role of O-glycans in conferring protease resistance
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DOI：
10.1074/jbc.m102150200
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发表时间：
2001-06-22
影响因子：
4.8
通讯作者：
Thillet, J
中科院分区：
文献类型：
--
作者：
Garner, B;Merry, AH;Thillet, J
载脂蛋白（a）（apo（a））是一种多结构域糖蛋白，与低密度脂蛋白的载脂蛋白B100共价连接，形成脂蛋白（a）（Lp（a））颗粒，或作为蛋白水解片段存在。血浆apo（a）及其片段浓度升高可能促进动脉粥样硬化，但其潜在机制尚未完全阐明。影响apo（a）蛋白水解的因素也不确定。在此，我们使用外切糖苷酶消化和质谱法对人载脂蛋白（a）的Asn（N）连接和Ser/Thr（O）连接寡糖进行测序。我们还评估了apo（a）O-聚糖在保护多肽的嗜热菌蛋白酶敏感区域中的潜在作用。载脂蛋白（a）含有两个主要的N-聚糖，占总寡糖结构的17%。N-聚糖是以单唾液酸化或双唾液酸化状态存在的复杂双触角结构。O-聚糖主要（80%）由单唾液酸化核心1型结构NeuNAc 2 α-3Gal β 1 -3GalNAc代表，还检测到少量的二唾液酸化和非唾液酸化O-聚糖。通过唾液酸酶和O-糖苷酶处理去除apo（a）O-聚糖显著增加了多肽对嗜热菌蛋白酶消化的敏感性。这些研究提供了载脂蛋白（a）聚糖的第一个直接测序数据，并表明载脂蛋白（a）O-聚糖的新功能可能与Lp（a）的致动脉粥样硬化性相关。
Apolipoprotein(a) (apo(a)) is a multikringle domain glycoprotein that exists covalently linked to apolipoprotein B100 of low density lipoprotein, to form the lipoprotein(a) (Lp(a)) particle, or as proteolytic fragments. Elevated plasma concentrations of apo(a) and its fragments may promote atherosclerosis, but the underlying mechanisms are incompletely understood. The factors influencing apo(a) proteolysis are also uncertain. Here we have used exoglycosidase digestion and mass spectrometry to sequence the Asn (N)-linked and Ser/Thr (O)-linked oligosaccharides of human apo(a). We also assessed the potential role of apo(a) O-glycans in protecting thermolysin sensitive regions of the polypeptide. Apo(a) contained two major N-glycans that accounted for 17% of the total oligosaccharide structures. The N-glycans were complex biantennary structures present in either a mono- or disialylated state. The O glycans were mostly (80%) represented by the mono sialylated core type 1 structure, NeuNAc2 alpha -3Gal beta1-3GalNAc, with smaller amounts of disialylated and non-sialylated O-glycans also detected. Removal of apo(a) O-glycans by sialidase and O-glycosidase treatment dramatically increased the sensitivity of the polypeptide to thermolysin digestion. These studies provide the first direct sequencing data for apo(a) glycans and indicate a novel function for apo(a) O-glycans that is potentially related to the atherogenicity of Lp(a).