Dahlbäck B, Hildebrand B
Department of Clinical Chemistry, University of Lund, Malmö General Hospital, Sweden.
Proc Natl Acad Sci U S A. 1994 Feb 15;91(4):1396-400. doi: 10.1073/pnas.91.4.1396.
Recently, our laboratory described a defect in anticoagulant response to activated protein C (APC). This response, APC resistance, was shown to be inherited and associated with familial thrombophilia. As other possible mechanisms were excluded, APC resistance was hypothesized to be due to deficiency of a previously unrecognized cofactor of APC. The aim of the present study was to isolate and characterize this factor. Plasma from an individual with pronounced inherited APC resistance was used as test plasma in a biological assay which monitored APC cofactor activity during its isolation from normal plasma. A purification procedure was devised that yielded a protein which was shown to be identical to coagulation factor V. It proved impossible to separate the APC cofactor activity from factor V, even by affinity chromatography using a monoclonal antibody against factor V. The affinity-purified factor V corrected the poor anticoagulant response to APC of APC-resistant plasma in a dose-dependent manner. Because the APC-resistant plasma contained normal levels of factor V procoagulant activity, the results indicated APC resistance to be due to a selective defect in the anticoagulant function of factor V. The present results show factor V not only to express procoagulant properties after its activation by thrombin but also to play an important part in the anticoagulant system as cofactor to APC.
最近，我们实验室描述了对抗活化蛋白C（APC）的抗凝反应存在缺陷。这种反应，即APC抵抗，被证明是遗传性的，且与家族性血栓形成倾向相关。由于排除了其他可能的机制，推测APC抵抗是由于一种先前未被认识的APC辅因子缺乏所致。本研究的目的是分离并鉴定该因子。在一项生物学检测中，将一名具有明显遗传性APC抵抗个体的血浆用作测试血浆，该检测在从正常血浆中分离APC辅因子活性的过程中监测其活性。设计了一种纯化程序，得到一种蛋白质，结果显示其与凝血因子V相同。事实证明，即使使用抗因子V单克隆抗体进行亲和层析，也无法将APC辅因子活性与因子V分开。亲和纯化的因子V以剂量依赖的方式纠正了APC抵抗血浆对APC抗凝反应不佳的情况。由于APC抵抗血浆中因子V促凝活性水平正常，结果表明APC抵抗是由于因子V抗凝功能的选择性缺陷所致。目前的结果表明，因子V不仅在被凝血酶激活后表现出促凝特性，而且作为APC的辅因子在抗凝系统中也起着重要作用。
