Determinants of binding and internalization of tissue-type plasminogen activator by human vascular smooth muscle and endothelial cells.
Determinants of binding and internalization of tissue-type plasminogen activator by human vascular smooth muscle and endothelial cells.
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DOI：
10.1016/s0021-9258(19)38651-x
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发表时间：
1993-06
期刊：
影响因子：
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通讯作者：
S. Grobmyer;A. Kuo;M. W. Orishimo;S. S. Okada-S.;D. Cines;E. Barnathan
中科院分区：
文献类型：
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作者：
S. Grobmyer;A. Kuo;M. W. Orishimo;S. S. Okada-S.;D. Cines;E. Barnathan
血管成形术引起的血管损伤通常伴随着平滑肌细胞（SMC）增殖、迁移和细胞外基质的积累。由于纤溶酶原激活剂及其受体可能是重要的细胞迁移和纤溶酶原激活剂的清除，我们研究了结合，内化和降解的放射性标记的组织型纤溶酶原激活剂（t-PA）的人血管平滑肌细胞的外植体培养。在4 ℃时，t-PA与SMC的结合是快速的、特异的、可饱和的，并可被纤溶酶原激活物抑制剂1型（派-1）抗体所抑制。在37摄氏度下，标记的t-PA被SMC内化和降解，但不被人脐静脉内皮细胞内化和降解。内化和降解由低密度脂蛋白受体相关蛋白/α 2-巨球蛋白受体（LRP）介导，因为这些过程被抗LRP抗体、重组LRP相关蛋白、尿激酶型纤溶酶原激活剂-PAI-1复合物和乳铁蛋白抑制。与派-1复合后对内化最重要的t-PA部分可能在指和/或表皮生长因子结构域中或在氨基酸117处的碳水化合物中，因为预先形成的t-PA、派-1复合物或在细胞表面上形成的复合物的内化被过量的活性位点封闭的野生型t-PA抑制，而不是由缺少这些结构域的活性位点封闭的t-PA变体。这些研究与t-PA最初与SMC相关派-1结合，随后通过LRP内化的模型一致。SMC可能在清除血管壁内t-PA-派-1复合物中起重要作用。
Vascular injury induced by angioplasty is often followed by smooth muscle cell (SMC) proliferation, migration, and accumulation of extracellular matrix. Since plasminogen activators and their receptors may be important both in cell migration and the clearance of plasminogen activators, we studied the binding, internalization, and degradation of radiolabeled tissue-type plasminogen activator (t-PA) by explant cultures of human vascular SMC. Binding of t-PA to SMC at 4 degrees C was rapid, specific, saturable, and inhibitable by antibodies to plasminogen activator inhibitor type 1 (PAI-1). At 37 degrees C, labeled t-PA was internalized and degraded by SMC but not by human umbilical vein endothelial cells. Internalization and degradation was mediated by the low density lipoprotein receptor related protein/alpha 2-macroglobulin receptor (LRP) in that these processes were inhibited by an anti-LRP antibody, recombinant LRP-associated protein, urokinase-type plasminogen activator-PAI-1 complexes, and lactoferrin. The portion of t-PA most important for internalization after complexing with PAI-1 is likely to be in the finger and/or epidermal growth factor domains or in the carbohydrate at amino acid 117, in that the internalization of preformed t-PA.PAI-1 complexes or complexes formed on the cell surface was inhibited by an excess of active site-blocked wild type t-PA, but not by an active site blocked t-PA variant missing these domains. These studies are consistent with a model in which t-PA binds initially to SMC-associated PAI-1 with subsequent t-PA.PAI-1 internalization via LRP. SMC may play an important role in clearing t-PA-PAI-1 complexes from within the vessel wall.