Karlsson Helen, Lindqvist Helen, Tagesson Christer, Lindahl Mats
Division of Occupational and Environmental Medicine, Department of Molecular and Clinical Medicine, Faculty of Health Sciences, Linköping University, Sweden.
J Proteome Res. 2006 Oct;5(10):2685-90. doi: 10.1021/pr060180x.
Apo M is a recently discovered human lipoprotein thought to be involved in the metabolism of lipids and lipoprotein particles. Here, a proteomic approach was applied to examine the glycosylation pattern of apo M in human LDL. We treated LDL proteins with N-glycosidase or neuraminidase, studied mobility shifts of Apo M by two-dimensional gel electrophoresis, and different isoforms were then identified with mass spectrometry. This way, we demonstrated the presence of five isoforms of apo M in LDL: three that are both N-glycosylated and sialylated, one that is N-glycosylated but not sialylated, and one that is neither N-glycosylated nor sialylated. As judged from the examination of LDL from 20 healthy human subjects, the three N-glycosylated and sialylated forms are most abundant (80-100% of the total apo M in LDL) whereas the unsialylated and unglycosylated variants constitute at most 20%. Comparative analysis showed that the same five isoforms of apo M are also present in HDL. Further studies aiming at elucidating the role of apo M in health and disease will have to take this polymorphism of apo M proteins into account.
载脂蛋白M是一种最近发现的人类脂蛋白，被认为参与脂质和脂蛋白颗粒的代谢。在此，我们应用蛋白质组学方法来检测人低密度脂蛋白（LDL）中载脂蛋白M的糖基化模式。我们用N - 糖苷酶或神经氨酸酶处理LDL蛋白，通过二维凝胶电泳研究载脂蛋白M的迁移率变化，然后用质谱法鉴定不同的异构体。通过这种方式，我们证明了LDL中存在五种载脂蛋白M异构体：三种同时进行了N - 糖基化和唾液酸化，一种进行了N - 糖基化但未进行唾液酸化，一种既未进行N - 糖基化也未进行唾液酸化。从对20名健康人类受试者的LDL检测结果来看，三种N - 糖基化和唾液酸化形式最为丰富（占LDL中总载脂蛋白M的80 - 100%），而未进行唾液酸化和糖基化的变体最多占20%。比较分析表明，高密度脂蛋白（HDL）中也存在相同的五种载脂蛋白M异构体。旨在阐明载脂蛋白M在健康和疾病中作用的进一步研究将不得不考虑载脂蛋白M蛋白的这种多态性。
