Kinetic analysis of the interaction between vitronectin and the urokinase receptor
Kinetic analysis of the interaction between vitronectin and the urokinase receptor
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DOI：
10.1074/jbc.m111225200
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发表时间：
2002-03-15
影响因子：
4.8
通讯作者：
Loskutoff, DJ
中科院分区：
文献类型：
--
作者：
Okumura, Y;Kamikubo, Y;Loskutoff, DJ
虽然尿激酶受体（uPAR）结合到玻连蛋白（VN），并促进细胞粘附到这种基质蛋白，这种相互作用的生化细节仍然不清楚。在BIAcore实验中使用VN变体以详细检查uPAR-VN相互作用并将其与VN与其他配体的相互作用进行比较。肝素和纤溶酶原结合到含有肝素结合结构域的VN片段，表明该结构域在重组肽中具有功能活性。然而，当uPAR与该结构域一起孵育时，没有检测到显著的结合，并且肝素和纤溶酶原都不与其竞争结合VN。事实上，uPAR仅结合到含有生长调节素B（SMB）结构域的片段，结合到该结构域的单克隆抗体（mAb）与uPAR竞争结合VN。单克隆抗体8 E6也抑制uPAR与VN的结合，并且该mAb显示识别SMB结构域附近区域中的硫酸化酪氨酸残基56和59。通过酸处理破坏该位点消除了mAb 8 E6结合，但对uPAR结合没有影响。因此，VN中似乎存在uPAR的单个结合位点，并且其位于SMB结构域中，并且与mAb 8 E6识别的表位不同。mAb 8 E6对uPAR与VN结合的抑制作用可能是空间位阻的结果。
Although the urokinase receptor (uPAR) binds to vitronectin (VN) and promotes the adhesion of cells to this matrix protein, the biochemical details of this interaction remain unclear. VN variants were employed in BIAcore experiments to examine the uPAR-VN interaction in detail and to compare it to the interaction of VN with other ligands. Heparin and plasminogen bound to VN fragments containing the heparin-binding domain, indicating that this domain was functionally active in the recombinant peptides. However, no significant binding was detected when uPAR was incubated with this domain, and neither heparin nor plasminogen competed with it for binding to VN. In fact, uPAR only bound to fragments containing the somatomedin B (SMB) domain, and monoclonal antibodies (mAbs) that bind to this domain competed with uPAR for binding to VN. Monoclonal antibody 8E6 also inhibited uPAR binding to VN, and this mAb was shown to recognize sulfated tyrosine residues 56 and 59 in the region adjacent to the SMB domain. Destruction of this site by acid treatment eliminated mAb 8E6 binding but had no effect on uPAR binding. Thus, there appears to be a single binding site for uPAR in VN, and it is located in the SMB domain and is distinct from the epitope recognized by mAb 8E6. Inhibition of uPAR binding to VN by mAb 8E6 probably results from steric hindrance.