Vischer U M, Wagner D D
Center for Hemostasis and Thrombosis Research, New England Medical Center, Boston, MA 02111.
Blood. 1994 Jun 15;83(12):3536-44.
We investigated the intracellular site of pro-von Willebrand factor (pro-vWF) cleavage and multimerization, as well as the fate of the propolypeptide (von Willebrand antigen II) after cleavage. Analysis of subcellular fractions of endothelial cells metabolically labeled with sulfate showed that both cleavage and covalent multimerization occur after sulfation and precede the formation of Weibel-Palade bodies. Because sulfation is a processing step localized to the trans-Golgi network (TGN), our results indicate that multimerization and prosequence cleavage also occur in this organelle. After cleavage, the propolypeptide remains noncovalently associated with the mature vWF subunit. This association is promoted by a high calcium concentration and an acidic pH (conditions thought to prevail in the TGN) and explains the 1:1 stoichiometry of the propolypeptide and mature vWF found in Weibel-Palade bodies. The propolypeptide remains an integral part of the large multimeric vWF aggregates in the Weibel-Palade body until secretion. When secretion occurs under slightly acidic conditions, such as may be found in poorly perfused wounds, the propolypeptide remains associated with the endothelial surface-bound vWF, and may thus participate in the wound healing process.
我们研究了血管性血友病因子原（pro-vWF）的切割和多聚化的细胞内位点，以及切割后前肽（血管性血友病抗原II）的去向。对用硫酸盐进行代谢标记的内皮细胞亚细胞组分的分析表明，切割和共价多聚化均发生在硫酸化之后且在魏尔-帕拉德小体形成之前。由于硫酸化是定位于反式高尔基体网络（TGN）的一个加工步骤，我们的结果表明多聚化和前序列切割也发生在这个细胞器中。切割后，前肽与成熟的vWF亚基保持非共价结合。这种结合受高钙浓度和酸性pH（据认为在TGN中占主导的条件）的促进，并解释了在魏尔-帕拉德小体中发现的前肽与成熟vWF的1:1化学计量比。在前肽在魏尔-帕拉德小体中保持为大多聚体vWF聚集体的一个组成部分直至分泌。当在诸如灌注不良的伤口中可能出现的微酸性条件下发生分泌时，前肽仍与内皮表面结合的vWF相关联，因此可能参与伤口愈合过程。
