Preston Roger J S, Morse Colin, Murden Sherina L, Brady Sara Kate, O'Donnell James S, Mumford Andrew D
Haemostasis Research Group, Institute of Molecular Medicine, Trinity College Dublin, St James Hospital, Dublin, Ireland.
Br J Haematol. 2009 Mar;144(6):946-53. doi: 10.1111/j.1365-2141.2008.07550.x. Epub 2008 Dec 26.
We report a kindred with heritable protein C (PC) deficiency in which two siblings with severe thrombosis showed a composite type I and IIb PC deficiency phenotype, identified using commercial PC assays (proband: PC antigen 42 u/dl, amidolytic activity 40 u/dl, anticoagulant activity 9 u/dl). The independent PROC nucleotide variations c.669C>A (predictive of Ser181Arg) and c.131C>T (predictive of Asn2Ile) segregated with the type I and type IIb PC deficiency phenotypes respectively, but co-segregated in the siblings with severe thrombosis. Soluble thrombomodulin (sTM)-mediated inhibition of plasma thrombin generation from an individual with PC-Asn2Ile was lower (endogenous thrombin potential (ETP) 56 +/- 1% that of ETP determined without sTM) than control plasma (ETP 15 +/- 2%) indicating reduced PC anticoagulant activity. Recombinant APC-Asn2Ile exhibited normal amidolytic activity but impaired anticoagulant activity. Protein S (PS)-dependent anticoagulant activity of recombinant APC-Asn2Ile and binding of recombinant APC-Asn2Ile to endothelial protein C receptor (EPCR) were reduced compared to recombinant wild-type APC. Asn2 lies within the omega-loop of the PC/APC Gla domain and this region is critical for calcium-induced folding and subsequent interactions with anionic phospholipids, EPCR and PS. The disruption of these interactions in this naturally-occurring PC variant highlights their collective importance in mediating APC anticoagulant activity in vivo.
我们报告了一个患有遗传性蛋白C（PC）缺乏症的家族，其中两名患有严重血栓形成的兄弟姐妹表现出I型和IIb型PC缺乏症的复合表型，这是通过商业PC检测确定的（先证者：PC抗原42 u/dl，酰胺水解活性40 u/dl，抗凝活性9 u/dl）。独立的PROC核苷酸变异c.669C>A（预测Ser181Arg）和c.131C>T（预测Asn2Ile）分别与I型和IIb型PC缺乏症表型共分离，但在患有严重血栓形成的兄弟姐妹中共同分离。可溶性血栓调节蛋白（sTM）介导的对PC-Asn2Ile个体血浆凝血酶生成的抑制作用低于对照血浆（内源性凝血酶潜力（ETP）为无sTM时测定的ETP的56±1%）（ETP为15±2%），表明PC抗凝活性降低。重组APC-Asn2Ile表现出正常的酰胺水解活性，但抗凝活性受损。与重组野生型APC相比，重组APC-Asn2Ile的蛋白S（PS）依赖性抗凝活性和重组APC-Asn2Ile与内皮蛋白C受体（EPCR）的结合减少。Asn2位于PC/APC Gla结构域的ω环内，该区域对于钙诱导的折叠以及随后与阴离子磷脂、EPCR和PS的相互作用至关重要。这种天然存在的PC变体中这些相互作用的破坏突出了它们在体内介导APC抗凝活性中的共同重要性。
