A SOLUBLE FORM OF THE GLYCOLIPID-ANCHORED RECEPTOR FOR UROKINASE-TYPE PLASMINOGEN-ACTIVATOR IS SECRETED FROM PERIPHERAL-BLOOD LEUKOCYTES FROM PATIENTS WITH PAROXYSMAL-NOCTURNAL HEMOGLOBINURIA
A SOLUBLE FORM OF THE GLYCOLIPID-ANCHORED RECEPTOR FOR UROKINASE-TYPE PLASMINOGEN-ACTIVATOR IS SECRETED FROM PERIPHERAL-BLOOD LEUKOCYTES FROM PATIENTS WITH PAROXYSMAL-NOCTURNAL HEMOGLOBINURIA
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DOI：
10.1111/j.1432-1033.1992.tb17200.x
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发表时间：
1992-09-01
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影响因子：
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通讯作者：
DANO, K
中科院分区：
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作者：
PLOUG, M;ERIKSEN, J;DANO, K
细胞尿激酶型纤溶酶原激活物(UPA)受体(UPAR)是一种糖脂锚定的膜蛋白，被认为参与细胞迁移和肿瘤侵袭过程中细胞周围蛋白的降解。在本研究中，我们鉴定并鉴定了两种保留了配体结合能力的可溶性形式的uPAR。一种变异体是在体外用磷脂酰肌醇特异性磷脂酶C(PLC)或内蛋白酶Asp-N处理完整的正常细胞而产生的。另一种可溶性的uPAR变异体是从干细胞疾病阵发性睡眠性血红蛋白尿症(PNH)患者的外周血白细胞体内分泌的，并在这些PNH患者的血浆和培养的PNH白细胞的条件培养液中发现。在正常情况下，我们没有发现任何证据表明血浆中有任何与人uPA结合的可溶性uPA结合对应物的脱落或分泌。与正常白细胞不同，受PNH影响的细胞不在细胞表面表达uPAR，尽管它们确实含有明显正常水平的uPAR特异性mRNA。PNH细胞分泌的uPAR在SDS/PAGE中的迁移率略高于PtdIns特异性PLC或洗涤剂增溶的uPAR，但与截短的重组变异体相似，其C末端靠近建议的糖脂结合位点，表明分泌的蛋白质已被蛋白质水解性加工用于糖脂结合。在PNH患者的血浆中存在这种分泌型、亲水性的UPAR，这支持了PNH疾病的损害要么存在于糖脂生物合成中，要么存在于一种尚未确定的转氨酶的功能中，该酶假定切割并组装截断的UPAR和预先形成的糖脂部分。
The cellular urokinase-type plasminogen-activator (uPA) receptor (uPAR) is a glycolipid-anchored membrane protein thought to be involved in pericellular proteolysis during cell migration and tumor invasion. In the present study, we have identified and characterized two soluble forms of uPAR which have retained their ligand-binding capability. One variant was generated in vitro by treatment of intact normal cells with either a phosphatidylinositol-specific phospholipase C (PLC) or endoproteinase Asp-N. The other soluble uPAR variant was secreted in vivo from peripheral blood leukocytes affected by the stem-cell disorder paroxysmal nocturnal hemoglobinuria (PNH), and was found in the plasma from these PNH patients as well as in the conditioned medium from cultured PNH leukocytes. Under normal conditions, we find no evidence for any shedding or secretion of a soluble uPA-binding counterpart to human uPAR in plasma. Unlike normal leukocytes, the PNH-affected cells do not express uPAR on the cell surface, although they do contain apparently normal levels of uPAR-specific mRNA. The secreted uPAR derived from PNH cells has a mobility in SDS/PAGE that is slightly higher than that of uPAR solubilized by PtdIns-specific PLC or detergent, but resembles that of a truncated, recombinant uPAR variant, which has its C-terminus close to the proposed glycolipid-attachment site, suggesting that the secreted protein has been proteolytically processed for glycolipid attachment. The presence in plasma from PNH patients of such a secreted, hydrophilic form of uPAR lends support to the hypothesis that the lesion underlying the PNH disorder resides either in glycolipid biosynthesis or in the function of an as-yet-unidentified transamidating enzyme assumed to cleave and assemble the truncated uPAR with the preformed glycolipid moiety.