Matrix metalloproteinases in angiogenesis: a moving target for therapeutic intervention
Matrix metalloproteinases in angiogenesis: a moving target for therapeutic intervention
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DOI：
10.1172/jci6870
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发表时间：
1999-05-01
影响因子：
15.9
通讯作者：
Stetler-Stevenson, WG
中科院分区：
文献类型：
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作者：
Stetler-Stevenson, WG
请参阅本期1227-1230页和1231-1236页本系列的其他文章。在血管膜、纤维蛋白凝块、I型胶原或基底膜基质中。在这些试验中，内皮细胞获得迁移或侵袭表型，重组细胞外基质，并在某些情况下重现微血管的管状形态，完成管腔形成。在许多早期研究中，细胞外基质被视为内皮细胞侵袭的屏障。MMP活性的主要作用是消除这种屏障并允许内皮细胞迁移。最近的研究挑战了这一概念，并表明细胞与细胞外基质的相互作用深刻地影响细胞行为。这些相互作用不仅影响MMP的产生，而且受到MMP活性的调节和调节。用外源性pro-MMP-2处理内皮细胞诱导与血管生成反应一致的剂量依赖性形态学变化（即管形成）（8）然而，这种作用达到平台期，并且进一步加入MMP-2开始逆转管形成。这些作用依赖于MMP-2活性，并被TIMP-2抑制。这表明，外源性pro-MMP-2被内皮细胞激活。但是内皮细胞如何激活pro-MMP-2呢？在二维I型胶原凝胶上培养的毛细血管内皮细胞产生低的组成性水平的pro-MMP-2，该蛋白酶几乎没有内源性激活。然而，当置于三维I型胶原凝胶中时，pro-MMP-2稳态转录水平显著增加（9）。在培养三天后，MMP-2分泌和活化的增加是显著的。这种对MMP-2表达和激活的影响与MT-1-MMP转录和表达的增强是协调的。MT-1-MMP介导的pro-MMP-2活化的当前模型涉及TIMP-2作为受体（图1a和参考文献7）。pro-MMP-2与MT-1-MMP/TIMP-2复合物的结合将该pro-MMP-2定位在细胞表面，并且激活是由第二个不含TIMP-2的MT-1-MMP分子在Asn 37-Leu 38键上的蛋白水解作用启动的。MMP-2前肽（10）。pro-MMP-2与TIMP-2的结合是由存在于大多数可溶性MMP中的COOH末端血红素样结构域（通常称为PEX）介导的。MMPs的PEX结构域的结构由反平行β折叠组成的四叶螺旋桨组成。TIMP-2结合结构域通过突变分析定位于MMP-2 PEX结构域的模块III和IV的连接处（11）。哈斯等人的研究(9)提出了相关数据，支持MT-1-MMP在三维胶原I凝胶中培养的内皮细胞产生的pro-MMP-2活化中的直接作用。这些细胞上或重建的基底膜中的培养物没有增强MMP-2的产生或MT-1-MMP介导的活化。这是一个有趣的对比，因为许多人认为基底膜是内皮细胞必须穿过以启动血管生成反应的第一个屏障。MMP激活的其他机制是否在与基底膜和/或临时基质接触的内皮细胞中起作用？当大鼠内皮细胞培养较长时间时
See other articles in this series on pages 1227–1230 and 1231–1236 in this issue. in amnionic membranes, fibrin clots, type I collagen, or basement membrane matrices. In these assays, endothelial cells acquire a migratory or invasive phenotype, reorganize the extracellular matrix, and in some cases recapitulate the tubular morphology of microvessels complete with lumen formation. In many early studies, the extracellular matrix was viewed as a barrier to endothelial cell invasion. The principal role of MMP activity was to remove this barrier and allow endothelial cell migration. Recent studies challenge this notion and suggest that cell–extracellular matrix interactions profoundly influence cell behavior. These interactions not only influence MMP production but are subject to modulation and regulation by MMP activity. In this way, MMP activity can directly and indirectly mediate the angiogenic response.Treatment of endothelial cells with exogenous pro-MMP-2 induces a dose-dependent morphologic change consistent with an angiogenic response (ie, tube formation)(8) However, this effect reaches a plateau, and addition of further MMP-2 begins to reverse tube formation. These effects are dependent on MMP-2 activity and are inhibited by TIMP-2. This suggests that exogenous pro-MMP-2 is activated by the endothelial cells. But how do endothelial cells activate pro-MMP-2? Capillary endothelial cells cultured on twodimensional type I collagen gels produce low, constitutive levels of pro-MMP-2 with little endogenous activation of this protease. However, when placed in threedimensional type I collagen gels, there is a marked increase in pro-MMP-2 steady-state transcript levels (9). After three days in culture, the increase in MMP-2 secretion and activation is pronounced. This effect on MMP-2 expression and activation is coordinate with enhancement of MT-1-MMP transcription and expression. The current model for MT-1-MMP–mediated activation of pro-MMP-2 involves TIMP-2 as a receptor (Figure 1a and ref. 7). Binding of pro-MMP-2 to the MT-1-MMP/TIMP-2 complex localizes this pro-MMP-2 on the cell surface, and activation is initiated by the proteolytic action of a second, TIMP-2–free MT-1-MMP molecule at the Asn37-Leu38 bond of the MMP-2 propeptide (10). Binding of pro-MMP-2 to TIMP-2 is mediated by the COOH-terminal hemopexin-like domain (often referred to as PEX), present in most soluble MMPs. The structure of the PEX domain of MMPs consists of a four-bladed propeller composed of antiparallel β sheets. The TIMP-2 binding domain is localized by mutational analysis to the junction of modules III and IV of the MMP-2 PEX domain (11). The study by Haas et al.(9) presents correlative data that supports a direct role for MT-1-MMP in the activation of pro-MMP-2 produced by endothelial cells cultured in three-dimensional collagen I gel. Culture of these cells on or in reconstituted basement membrane did not enhance MMP-2 production or MT-1-MMP–mediated activation. This is an interesting contrast, as many view basement membrane as the first barrier that endothelial cells must cross to initiate an angiogenic response. Are other mechanisms of MMP activation operative in endothelial cells in contact with basement membrane and/or provisional matrix? When rat endothelial cells are cultured for longer periods