Alternative mRNA is favored by the A3 haplotype of the EPCR gene PROCR and generates a novel soluble form of EPCR in plasma
Alternative mRNA is favored by the A3 haplotype of the EPCR gene PROCR and generates a novel soluble form of EPCR in plasma
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DOI：
10.1182/blood-2007-08-104968
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发表时间：
2008-04-01
期刊：
影响因子：
20.3
通讯作者：
Gandrille, Sophie
中科院分区：
文献类型：
--
作者：
Saposnik, Beatrice;Lesteven, Elodie;Gandrille, Sophie
内皮细胞蛋白C受体也以可溶形式存在于血浆中（sEPCR），由ADAM 17裂解产生。在携带A3单倍型的受试者中观察到升高的sEPCR水平，其特征在于跨膜结构域中的Ser219Gly取代，使得受体对切割更敏感。由于sEPCR的产生并没有被金属蛋白酶抑制完全阻断，我们寻找了另一种机制。比较mRNA表达模式和水平在A3和非A3细胞从32人脐带静脉，我们检测到一个截短的mRNA，除了全长mRNA。这种截短的mRNA在A3人脐静脉内皮细胞中比在非A3人脐静脉内皮细胞中丰富16倍，并且编码缺乏跨膜结构域的蛋白质。我们稳定地表达了该蛋白的重组形式（rEPCR同种型）和模拟血浆sEPCR的蛋白（rEPCR sol）。纯化的重组蛋白的功能研究表明，rEPCR异构体结合重组蛋白C具有类似的亲和力比rEPCR溶胶，它也抑制APC的抗凝活性。在A3受试者的血浆中发现痕量EPCR亚型。这些结果表明，sEPCR异构体可能有助于血浆中sEPCR的调节作用。
The endothelial cell protein C receptor also exists in soluble form in plasma (sEPCR), resulting from ADAM17 cleavage. Elevated sEPCR levels are observed in subjects carrying the A3 haplotype, which is characterized by a Ser219Gly substitution in the transmembrane domain, rendering the receptor more sensitive to cleavage. Because sEPCR production is not completely blocked by metalloprotease inhibition, we looked for another mechanism. Comparing mRNA expression patterns and levels in A3 and non-A3 cells from 32 human umbilical cord veins, we detected a truncated mRNA in addition to the full-length mRNA. This truncated mRNA was 16 times more abundant in A3 human umbilical vein endothelial cells than in non-A3 human umbilical vein endothelial cells and encoded a protein lacking the transmembrane domain. We stably expressed a recombinant form of this protein (rEPCRisoform) and a protein mimicking the plasma sEPCR (rEPCRsol). Functional studies of the purified recombinant proteins revealed that the rEPCRisoform bound to recombinant protein C with similar affinity than rEPCRsol and that it also inhibited the anticoagulant activity of APC. Trace amounts of the EPCR isoform were found in the plasma of A3 subjects. These results suggest that the sEPCRisoform could contribute to the regulatory effect of sEPCR in plasma.