Angiopoietin-like 4 Modifies the Interactions between Lipoprotein Lipase and Its Endothelial Cell Transporter GPIHBP1
Angiopoietin-like 4 Modifies the Interactions between Lipoprotein Lipase and Its Endothelial Cell Transporter GPIHBP1
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DOI：
10.1074/jbc.m114.623769
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发表时间：
2015-05-08
影响因子：
4.8
通讯作者：
Davies, Brandon S. J.
中科院分区：
文献类型：
--
作者：
Chi, Xun;Shetty, Shwetha K.;Davies, Brandon S. J.
背景：脂蛋白脂肪酶（LPL）的功能通过与其转运体GPIHBP1和抑制剂血管生成素样4 （ANGPTL4）的相互作用而改变。结果：ANGPTL4使gpihbp1结合的LPL失活。灭活的LPL不能结合GPIHBP1。结论：ANGPTL4失活使LPL对GPIHBP1的亲和力降低，导致LPL解离。意义：了解ANGPTL4在生理背景下与LPL的相互作用对于阐明ANGPTL4在甘油三酯代谢中的作用至关重要。从血浆甘油三酯中释放脂肪酸用于组织摄取的过程严重依赖于脂蛋白脂肪酶（LPL）。LPL对血浆甘油三酯的水解可被血管生成素样4蛋白（ANGPTL4）破坏，ANGPTL4已被证明能在体外使LPL失活。然而，在体内，LPL经常在毛细血管内皮细胞表面与糖基磷脂酰肌醇锚定的高密度脂蛋白结合蛋白1 （GPIHBP1）络合。GPIHBP1负责运输LPL穿过毛细血管内皮细胞，并在脂解过程中将LPL锚定在毛细血管壁上。在这种情况下，ANGPTL4如何与LPL相互作用尚不清楚。在本研究中，我们研究了内皮细胞表面ANGPTL4与LPL-GPIHBP1复合物的相互作用。我们发现，ANGPTL4能够结合内皮细胞表面与GPIHBP1复合物的LPL并使其失活。一旦失活，LPL与GPIHBP1分离。我们还发现，angptl4失活的LPL不能结合GPIHBP1。在4℃条件下，ANGPTL4能够结合LPL，但不能使LPL失活，这表明仅结合不足以使ANGPTL4具有抑制活性。我们观察到，尽管ANGPTL4本身和全长ANGPTL4的n端卷曲结构域与LPL的结合具有相似的亲和力，但n端片段对游离LPL和gpihbp1结合的LPL都具有更强的失活能力。这些结果使我们得出结论，ANGPTL4可以结合并灭活与GPIHBP1配合的LPL，并且ANGPTL4使LPL失活大大降低了LPL对GPIHBP1的亲和力。
Background: Lipoprotein lipase (LPL) function is modified by interactions with its transporter GPIHBP1 and the inhibitor angiopoietin-like 4 (ANGPTL4). Results: ANGPTL4 inactivated GPIHBP1-bound LPL. Inactivated LPL could not bind GPIHBP1. Conclusion: ANGPTL4 inactivation of LPL reduces the affinity of LPL for GPIHBP1 causing dissociation. Significance: Understanding ANGPTL4's interactions with LPL in a physiological context is vital to clarifying ANGPTL4's role in triglyceride metabolism.The release of fatty acids from plasma triglycerides for tissue uptake is critically dependent on the enzyme lipoprotein lipase (LPL). Hydrolysis of plasma triglycerides by LPL can be disrupted by the protein angiopoietin-like 4 (ANGPTL4), and ANGPTL4 has been shown to inactivate LPL in vitro. However, in vivo LPL is often complexed to glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) on the surface of capillary endothelial cells. GPIHBP1 is responsible for trafficking LPL across capillary endothelial cells and anchors LPL to the capillary wall during lipolysis. How ANGPTL4 interacts with LPL in this context is not known. In this study, we investigated the interactions of ANGPTL4 with LPL-GPIHBP1 complexes on the surface of endothelial cells. We show that ANGPTL4 was capable of binding and inactivating LPL complexed to GPIHBP1 on the surface of endothelial cells. Once inactivated, LPL dissociated from GPIHBP1. We also show that ANGPTL4-inactivated LPL was incapable of binding GPIHBP1. ANGPTL4 was capable of binding, but not inactivating, LPL at 4 degrees C, suggesting that binding alone was not sufficient for ANGPTL4's inhibitory activity. We observed that although the N-terminal coiled-coil domain of ANGPTL4 by itself and full-length ANGPTL4 both bound with similar affinities to LPL, the N-terminal fragment was more potent in inactivating both free and GPIHBP1-bound LPL. These results led us to conclude that ANGPTL4 can both bind and inactivate LPL complexed to GPIHBP1 and that inactivation of LPL by ANGPTL4 greatly reduces the affinity of LPL for GPIHBP1.