Interaction of single-chain urokinase with its receptor induces the appearance and disappearance of binding epitopes within the resultant complex for other cell surface proteins
Interaction of single-chain urokinase with its receptor induces the appearance and disappearance of binding epitopes within the resultant complex for other cell surface proteins
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DOI：
10.1182/blood.v88.2.542.bloodjournal882542
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发表时间：
1996-07-15
期刊：
影响因子：
20.3
通讯作者：
Cines, DB
中科院分区：
文献类型：
--
作者：
Higazi, AAR;Upson, RH;Cines, DB
尿激酶型纤溶酶原激活物（uPA）与其糖基磷脂酰肌醇锚定受体（uPAR）的结合启动某些细胞类型中的信号转导、粘附和迁移。为了确定这些活动中的一些是否可能是由uPA/uPAR复合物和其他细胞表面蛋白之间的关联介导的，我们研究了由重组可溶性uPA受体（suPAR）和单链uPA（scuPA）组成的复合物与不表达糖基磷脂酰肌醇（GPI）锚定蛋白的细胞系（LM-TK成纤维细胞）的结合，以消除内源性uPA受体的潜在竞争。scuPA诱导suPAR与LM-TK-细胞的结合。未标记的复合物抑制标记的suPAR/scuPA的结合，但不单独加入scuPA或suPAR，表明细胞结合：已形成的网站不存在于任何组件。复合物的结合被低分子量UPA（LMW-uPA）抑制，表明暴露了通常在双链uPA（tcuPA）的分离的B链中发现的表位，但隐藏在可溶性scuPA中。LMW-uPA的结合不依赖于其催化位点，并且与ifs酶活性的保留相关。另外的细胞结合表位通过scuPA的氨基末端片段在suPAR自身内产生，scuPA自身不与LM-TK细胞结合。当scuPA与suPAR结合时，α（2）-巨球蛋白受体/LDL受体相关蛋白（α（2）MR/LRP）的结合位点被静止，而细胞相关的玻连蛋白和血小板反应蛋白的结合位点被诱导。与此雅阁，在suPAR存在下，细胞相关tcuPA和tcuPA-PAI-1复合物的内化和降解效率较低。此外，几乎没有检测到suPAR的降解，表明细胞结合的复合物在胞吞作用的初始阶段解离，因此，scuPA与其受体的相互作用引起复合物内的多种功能变化，包括scuPA中参与其从细胞表面清除的表位的消失和促进其与参与细胞粘附和信号传导的蛋白质结合的新表位的产生。转导(C)1996年，美国血液学会。
Binding of urokinase-type plasminogen activator (uPA) to its glycosylphosphatidylinositol-anchored receptor (uPAR) initiates signal transduction, adhesion, and migration in certain cell types. To determine whether some of these activities may be mediated by associations between the uPA/uPAR complex and other cell surface proteins, we studied the binding of complexes composed of recombinant soluble uPA receptor (suPAR) and single chain uPA (scuPA) to a cell line (LM-TK fibroblasts) that does not express glycosylphosphatidylinositol (GPI)-anchored proteins to eliminate potential competition by endogenous uPA receptors. scuPA induced the binding of suPAR to LM-TK- cells. Binding of labeled suPAR/scuPA was inhibited by unlabeled complex, but not by scuPA or suPAR added separately, indicating cellular binding:sites had been formed that are not present in either component. Binding of the complex was inhibited by low molecular weight UPA (LMW-uPA) indicating exposure of an epitope found normally in the isolated B chain of two chain uPA (tcuPA), but hidden in soluble scuPA. Binding of LMW-uPA was independent of its catalytic site and was associated with retention of ifs enzymatic activity. Additional cell binding epitopes were generated within suPAR itself by the aminoterminal fragment of scuPA, which itself does not bind to LM-TK- cells. When scuPA bound to suPAR, a binding site for alpha(2)-macroglobulin receptor/LDL receptor-related protein (alpha(2)MR/LRP) was rest, while binding sites for cell-associated vitronectin and thrombospondin were induced. In accord with this, the internalization and degradation of cell-associated tcuPA and tcuPA-PAI-1 complexes proceeded less efficiently in the presence of suPAR. Further, little degradation of suPAR was detected, suggesting that cell-bound complex dissociated during the initial stages of endocytosis, Thus, the interaction of scuPA with its receptor causes multiple functional changes within the complex including the disappearance of an epitope in scuPA involved in its clearance from the cell surface and the generation of novel epitopes that promote its binding to proteins involved in cell adhesion and signal transduction. (C) 1996 by The American Society of Hematology.