A composite role of vitronectin and urokinase in the modulation of cell morphology upon expression of the urokinase receptor
A composite role of vitronectin and urokinase in the modulation of cell morphology upon expression of the urokinase receptor
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DOI：
10.1074/jbc.c700214200
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发表时间：
2008-05-30
影响因子：
4.8
通讯作者：
Behrendt, Niels
中科院分区：
文献类型：
--
作者：
Hillig, Thore;Engelholm, Lars H.;Behrendt, Niels
尿激酶受体，尿激酶受体（uPAR），是一种糖基磷脂酰肌醇锚定的膜蛋白，参与细胞周围的蛋白水解和细胞粘附，迁移和细胞形态的调节。直接基质粘附是通过uPAR与玻连蛋白的结合介导的，并且该事件之后是下游效应，包括细胞骨架组织的变化。然而，目前还不清楚是否通过uPAR-玻连蛋白的粘附是唯一的事件能够启动这些形态学重排或uPAR和整合素之间的横向相互作用是否可以诱导相同的反应。在这份报告中，我们表明，这两个触发机制可以操作，uPAR依赖的细胞形态的调制确实可以独立于直接玻连蛋白结合发生。野生型uPAR在HEK 293细胞上的表达导致明显的玻连蛋白粘附和细胞骨架重排，而突变型uPAR，具有缺陷的玻连蛋白结合的uPAR（W32 A），未能诱导这两种现象。然而，饱和后的uPAR（W32 A）与蛋白酶配体，pro-uPA，或其受体结合域，诱导细胞骨架重排的能力得到恢复，虽然这并没有拯救uPAR-玻连蛋白的结合和粘附能力。另一方面，使用其他uPAR变体，我们可以证明uPAR-玻连蛋白粘附确实能够且足以诱导相同的形态学重排。这与细胞表达不同的单位点突变体，uPAR（Y 57 A），在合成的uPAR结合肽的存在下，以及与野生型uPAR，进行细胞骨架重排，即使在uPA缺乏血清培养。用含Arg-Gly-Asp的肽阻断整合素可抵消启动uPAR依赖性细胞骨架重排所需的基质接触，而在所有情况下Rac信号通路的失活抑制了相同事件的发生。
The urokinase receptor, urokinase receptor (uPAR), is a glycosylphosphatidylinositol-anchored membrane protein engaged in pericellular proteolysis and cellular adhesion, migration, and modulation of cell morphology. A direct matrix adhesion is mediated through the binding of uPAR to vitronectin, and this event is followed by downstream effects including changes in the cytoskeletal organization. However, it remains unclear whether the adhesion through uPAR-vitronectin is the only event capable of initiating these morphological rearrangements or whether lateral interactions between uPAR and integrins can induce the same response. In this report, we show that both of these triggering mechanisms can be operative and that uPAR-dependent modulation of cell morphology can indeed occur independently of a direct vitronectin binding. Expression of wild-type uPAR on HEK293 cells led to pronounced vitronectin adhesion and cytoskeletal rearrangements, whereas a mutant uPAR, uPAR(W32A) with defective vitronectin binding, failed to induce both phenomena. However, upon saturation of uPAR(W32A) with the protease ligand, pro-uPA, or its receptor-binding domain, the ability to induce cytoskeletal rearrangements was restored, although this did not rescue the uPAR-vitronectin binding and adhesion capability. On the other hand, using other uPAR variants, we could show that uPAR-vitronectin adhesion is indeed capable and sufficient to induce the same morphological rearrangements. This was shown with cells expressing a different single-site mutant, uPAR(Y57A), in the presence of a synthetic uPAR-binding peptide, as well as with wildtype uPAR, which underwent cytoskeletal rearrangements even when cultivated in uPA-deficient serum. Blocking of integrins with an Arg-Gly-Asp-containing peptide counteracted the matrix contacts necessary to initiate the uPAR-dependent cytoskeletal rearrangements, whereas inactivation of the Rac signaling pathway in all cases suppressed the occurrence of the same events.