Bovenschen N, Rijken D C, Havekes L M, van Vlijmen B J M, Mertens K
Department of Plasma Proteins, Sanquin Research at CLB, Amsterdam, The Netherlands.
J Thromb Haemost. 2005 Jun;3(6):1257-65. doi: 10.1111/j.1538-7836.2005.01389.x.
Coagulation factor VIII (FVIII) is a heavily glycosylated heterodimeric plasma protein that consists of a heavy (domains A1-A2-B) and light chain (domains A3-C1-C2). It has been well established that the clearance of FVIII from the circulation involves mechanisms that are sensitive to the low-density lipoprotein receptor (LDLR) family antagonist receptor-associated protein (RAP), including LDLR-related protein. Because FVIII clearance in the presence of a bolus injection of RAP still occurs fairly efficient, also RAP-independent mechanisms are likely to be involved.
In the present study, we investigated the interaction of FVIII with the endocytic lectin asialoglycoprotein receptor (ASGPR) and the physiological relevance thereof.
Surface plasmon resonance studies demonstrated that FVIII dose-dependently bound to ASGPR with high affinity (Kd approximately 2 nM). FVIII subunits were different in that only the heavy chain displayed high-affinity binding to ASGPR. Studies employing a FVIII variant that lacks the B domain revealed that FVIII-ASGPR complex assembly is driven by structure elements within the B domain of the heavy chain. The FVIII heavy chain-ASGPR interaction required calcium ions and was inhibited by soluble D-galactose. Furthermore, deglycosylation of the FVIII heavy chain by endoglycosidase F completely abrogated the interaction with ASGPR. In clearance experiments in mice, the FVIII mean residence time was prolonged by the ASGPR-antagonist asialo-orosomucoid (ASOR).
We conclude that asparagine-linked oligosaccharide structures of the FVIII B domain recognize the carbohydrate recognition domains of ASGPR and that an ASOR-sensitive mechanism, most likely ASGPR, contributes to the catabolism of coagulation FVIII in vivo.
凝血因子VIII（FVIII）是一种高度糖基化的异源二聚体血浆蛋白，由重链（结构域A1 - A2 - B）和轻链（结构域A3 - C1 - C2）组成。FVIII从循环中的清除机制已被充分证实，这些机制对低密度脂蛋白受体（LDLR）家族拮抗剂受体相关蛋白（RAP）敏感，包括低密度脂蛋白受体相关蛋白。由于在大剂量注射RAP的情况下FVIII清除仍相当有效，因此可能还涉及不依赖RAP的机制。
在本研究中，我们研究了FVIII与内吞凝集素去唾液酸糖蛋白受体（ASGPR）的相互作用及其生理相关性。
表面等离子体共振研究表明，FVIII以剂量依赖性方式与ASGPR高亲和力结合（解离常数约为2 nM）。FVIII亚基有所不同，只有重链显示出与ASGPR的高亲和力结合。使用缺乏B结构域的FVIII变体进行的研究表明，FVIII - ASGPR复合物的组装由重链B结构域内的结构元件驱动。FVIII重链与ASGPR的相互作用需要钙离子，并被可溶性D - 半乳糖抑制。此外，内切糖苷酶F对FVIII重链的去糖基化完全消除了与ASGPR的相互作用。在小鼠清除实验中，ASGPR拮抗剂去唾液酸血清类黏蛋白（ASOR）延长了FVIII的平均驻留时间。
我们得出结论，FVIII B结构域的天冬酰胺连接的寡糖结构识别ASGPR的碳水化合物识别结构域，并且一种对ASOR敏感的机制，很可能是ASGPR，在体内有助于凝血因子FVIII的分解代谢。
