Study on the mode of carbohydrate recognition by functional analysis of mannan-binding protein as a multi-functional protein.

甘露聚糖结合蛋白（Mannan-binding protein，MBP）是一种对甘露糖、岩藻糖和N-乙酰氨基葡萄糖具有特异性的C型血清凝集素，与宿主动物体内病原微生物的清除有关。虽然猪已被提出是一个有吸引力的来源，异种移植的组织和器官，很少有人知道猪MBP。在我们以前的研究中，磷酸甘露聚糖，而不是甘露聚糖，被发现是一种有效的抑制剂的C1q独立的杀菌活性的新生仔猪血清对一些粗糙的菌株的革兰氏阴性菌。在这里，我们表明，一种新的磷酸甘露聚糖结合凝集素（PMBL）的33 kDa的还原条件下，从新生儿和成年猪血清中分离和表征。猪PMBL通过与磷酸甘露聚糖和甘露聚糖结合触发的凝集素途径激活补体系统，与MBP不同，其被含甘露糖6-磷酸的寡糖有效抑制。我们的观察表明，猪PMBL在猪的免疫系统中起着关键作用。 ...更多信息 从新生儿阶段到成年期，在先天免疫防御中发挥重要作用。MBP主要在肝脏中合成，并且以两种形式天然存在，血清MBP（S-MBP）和细胞内MBP（I-MBP）。S-MBP通过凝集素途径激活与MBP相关的丝氨酸蛋白酶相关的补体。另一方面，I-MBP的亚细胞定位及其功能意义尚不清楚。在这里，我们证明了I-MBP显示出明显的积累在细胞质颗粒，并主要定位在ER和参与COPII囊泡介导的ER到高尔基体的运输。然而，无论是突变体（C236S/C244S）I-MBP，缺乏碳水化合物结合活性，或野生型I-MBP在衣霉素处理的细胞亚细胞定位显示出同样弥漫的细胞质分布，这表明，独特的积累I-MBP在ER和COPII囊泡介导的N-聚糖-凝集素相互作用。这些结果强烈表明，I-MBP可能作为货物运输凝集素促进ER到高尔基体的交通在糖蛋白质量控制。此外，我们正在制备识别人结肠直肠癌SW 1116细胞表面表达的MBP-配体寡糖的单克隆抗体。少

Mannan-binding protein (MBP) is a C-type serum lectin specific for mannose, fucose and N-acetylglucosamine, and is associated with the removal of pathogenic microorganisms from the host animals. While the pig has been proposed to be an attractive source of xeno transplantable tissues and organs, little is known about porcine MBP. In our previous studies, phosphomannan, but not mannan, was found to be an effective inhibitor of the C1q-independent bactericidal activity of newborn piglet serum against some rough strains of gram-negative bacteria. Here we show that a novel phosphomannan-binding lectin (PMBL) of 33 kDa under reducing conditions was isolated from both newborn and adult porcine serum and characterized. Porcine PMBL activated the complement system via the lectin pathway triggered by binding with both phosphomannan and mannan, which, unlike MBP, was effectively inhibited by mannose 6-phosphate-containing oligosaccharides. Our observations suggest that porcine PMBL plays a criti … More cal role in the innate immune defense from the newborn stage to adulthood. MBP is mainly synthesized in the liver and occurs naturally in two forms, serum MBP (S-MBP) and intracellular MBP (I-MBP). S-MBP activates complement in association with MBP-associated serine proteases via the lectin pathway. On the other hand, the subcellular localization of I-MBP and its functional implication have not been clarified yet. Here, we demonstrated that I-MBP shows distinct accumulation in cytoplasmic granules, and is predominantly localized in the ER and involved in COPII vesicle-mediated ER-to-Golgi transport. However, the subcellular localization of either a mutant (C236S/C244S) I-MBP, which lacks carbohydrate-binding activity, or the wild-type I-MBP in tunicamycin-treated cells shows an equally diffuse cytoplasmic distribution, suggesting that the unique accumulation of I-MBP in the ER and COPII vesicles is mediated by an N-glycan-lectin interaction. These results strongly indicate that I-MBP may function as a cargo transport lectin facilitating ER-to-Golgi traffic in glycoprotein quality control. In addition, we are preparing monoclonal antibodies recognizing MBP-ligand oligosaccharides expressed on the surfaces of a human colorectal carcinoma SW1116 cells. Less