Extracellular matrix-bound angiopoietin-like 4 inhibits endothelial cell adhesion, migration, and sprouting and alters actin cytoskeleton
Extracellular matrix-bound angiopoietin-like 4 inhibits endothelial cell adhesion, migration, and sprouting and alters actin cytoskeleton
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DOI：
10.1161/01.res.0000250758.63358.91
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发表时间：
2006-11-24
影响因子：
20.1
通讯作者：
Monnot, Catherine
中科院分区：
文献类型：
--
作者：
Cazes, Aurelie;Galaup, Ariane;Monnot, Catherine
血管生成素样蛋白4（Angiopoietin-like 4，ANGPTL 4）是一种分泌性蛋白，属于血管生成素家族，参与血管生成和代谢调节。我们先前报道了缺氧诱导血管生成素4在内皮细胞和人缺血组织外周动脉疾病。我们在小鼠后肢缺血模型中观察到血管中mRNA的上调与缺血组织中全长蛋白的积累相关。然后我们研究了它在内皮细胞中的功能。响应于缺氧，内源性ANGPTL 4在内皮下细胞外基质（ECM）中积累。虽然分泌的蛋白质经历蛋白水解，导致培养基中存在截短的片段，但只有全长ANGPTL 4与ECM相互作用。竞争和直接结合测定表明ANGPTL 4与ECM的强烈相互作用是肝素/硫酸乙酰肝素蛋白聚糖依赖性的。ANGPTL 4的基质相关和可溶形式之间的平衡表明ECM在调节其生物利用度中的作用。ECM结合的全长蛋白质的血管生成功能使用与来自ANGPTL 4转染的HEK 293细胞的条件ECM相关的形式或纯化的固定化蛋白质进行研究。我们发现，基质相关的和固定的ANGPTL 4限制形成肌动蛋白应力纤维和粘着内皮细胞中的焦点接触，并抑制其粘附。固定化ANGPTL 4还降低内皮细胞的运动性并抑制发芽和管形成。总之，这些发现表明缺氧内皮细胞在ECM中积累ANGPTL 4，这反过来又通过自分泌途径负调节其血管生成能力。
Angiopoietin-like 4 (ANGPTL4) is a secreted protein that belongs to the angiopoietin family and is involved in angiogenesis and metabolism regulation. We previously reported the induction of angptl4 by hypoxia in endothelial cells and in human ischemic tissues from peripheral artery disease. We here observed in a mouse model of hindlimb ischemia that the mRNA upregulation in the vessels correlates with the accumulation of the full-length protein in ischemic tissues. We then investigated its functions in endothelial cells. In response to hypoxia, endogenous ANGPTL4 accumulates in the subendothelial extracellular matrix (ECM). Although the secreted protein undergoes proteolysis leading to truncated fragments present in the medium, only full-length ANGPTL4 interacts with the ECM. Competition and direct binding assays indicate that the strong interaction of ANGPTL4 with the ECM is heparin/heparan sulfate proteoglycan dependent. The balance between matrix-associated and soluble forms of ANGPTL4 points to the role of the ECM in the regulation of its bioavailability. The angiogenic function of the ECM-bound full-length protein was investigated using either the form associated with the conditioned ECM from ANGPTL4-transfected HEK293 cells or the purified immobilized protein. We show that matrix-associated and immobilized ANGPTL4 limit the formation of actin stress fibers and focal contacts in the adhering endothelial cells and inhibit their adhesion. Immobilized ANGPTL4 also decreases motility of endothelial cells and inhibits the sprouting and tube formation. Altogether, these findings show that hypoxic endothelial cells accumulate ANGPTL4 in the ECM, which in turn negatively regulates their angiogenic capacities through an autocrine pathway.