Lysophospholipid metabolism and signalling - role of lysophospholipases

生物活性脂肪(脂)影响许多生物过程，包括细胞生长、死亡和迁移。溶血磷脂酸(LPA)是一种具有生物活性的溶血磷脂，主要由溶血磷脂降解酶(溶血磷脂酶)、自体趋化蛋白产生。我们的工作在哺乳动物的自体趋化蛋白-LPA途径和能量代谢之间建立了联系。我们发现，自体趋化蛋白受到营养物质和胰岛素的影响，自体趋化蛋白-LPA途径阻碍了线粒体的功能，线粒体是细胞的动力源。目前尚不清楚这一途径是如何准确影响线粒体的维持和功能的。磷脂磷酸酶3(LPP3)是一种分解LPA的溶血磷脂酶。LPP3对胚胎的形成是必不可少的，并因其在血管发育和功能中的作用而广为人知。LPP3存在于高能量代谢的组织中，包括肌肉和脂肪，并与糖代谢有关。然而，LPP3、线粒体功能和能量代谢之间的关系在很大程度上尚不清楚。这项研究的总体目标是研究自体趋化蛋白和LPP3在哺乳动物能量代谢和线粒体维持和功能中的作用。利用培养的哺乳动物脂肪和肌肉细胞暴露于LPA，以及自体趋化素水平降低的小鼠的脂肪和肌肉组织，我们将测试自体趋化蛋白-LPA途径是否影响线粒体的融合和裂变。这个过程被称为线粒体动力学，与线粒体的能量代谢和功能有关。线粒体结构将通过电子显微镜进行评估。参与线粒体动力学的蛋白质将使用免疫印迹技术进行测量。荧光显微镜将使我们能够看到活细胞中线粒体的融合和分裂。通过阻断不同的LPA受体，我们将确定哪些受体参与了自体趋化蛋白-LPA介导的线粒体动力学变化。我们还将评估自体趋化蛋白-LPA是否通过有丝分裂改变线粒体的降解。利用小鼠和大鼠，我们将确定LPP3水平和活性是否会随着喂食/禁食的反应而变化。我们将使用培养的脂肪和肌肉细胞来评估不同的能量底物和饥饿如何影响LPP3。我们还将使用显微镜监测LPP3定位到细胞室的变化。LPP3的增加和减少对养分吸收和氧化的影响将使用标记底物和线粒体呼吸测量法进行检测。肌肉和脂肪特异性地增加LPP3的小鼠将被用来验证LPP3是否改变了活生物体中这些组织的能量代谢。全面的代谢物分析将通过质谱仪进行。还将评估线粒体的动力学和降解情况。这项研究将为自体趋化蛋白和LPP3的生物学作用提供新的见解，并阐明这些溶血磷脂酶如何影响能量代谢和线粒体的维持和功能。

Bioactive fats (lipids) influence many biological processes including cell growth, death, and migration. Lysophosphatidic acid (LPA) is a bioactive lysophospholipid that is mainly produced by the lysophospholipid degrading enzyme (lysophospholipase), autotaxin. Our work established a connection between the autotaxin-LPA pathway and energy metabolism in mammals. We showed that autotaxin is influenced by nutrients and insulin and that the autotaxin-LPA pathway hinders the function of mitochondria, the powerhouses of the cell. It remains unclear how this pathway precisely influences mitochondrial maintenance and function. Lipid phosphate phosphatase 3 (LPP3) is a lysophospholipase that breaks down LPA. LPP3 is essential for embryo formation and is best known for its role in blood vessel development and function. LPP3 is present in tissues with high energy metabolism including muscle and adipose and was implicated in sugar metabolism. However, the relationship between LPP3, mitochondrial function and energy metabolism is largely unexplored. The overall goal of this research is to examine the role of autotaxin and LPP3 in mammalian energy metabolism and mitochondrial maintenance and function. Using cultured mammalian fat and muscle cells exposed to LPA and fat and muscle tissue from mice with reduced autotaxin levels, we will test whether the autotaxin-LPA pathway affects the fusion and fission of mitochondria. This process, termed mitochondrial dynamics, is linked to mitochondrial energy metabolism and function. Mitochondrial structure will be assessed by electron microscopy. Proteins involved in mitochondrial dynamics will be measured using immunoblotting technique. Fluorescence microscopy will allow us to visualize mitochondrial fusion and fission in live cells. By blocking distinct LPA receptors, we will determine which receptors are involved in autotaxin-LPA mediated changes in mitochondrial dynamics. We will also assess whether autotaxin-LPA alters mitochondrial degradation through mitophagy. Using mice and rats, we will determine whether LPP3 levels and activity change in response to feeding/fasting. We will employ cultured fat and muscle cells to assess how different energy substrates and starvation affect LPP3. We will also monitor changes in LPP3 localization to cellular compartments using microscopy. The effect of increased and decreased LPP3 on nutrient uptake and oxidation will be examined using labeled substrates and mitochondrial respirometry. Mice with muscle and fat-specific increases in LPP3 will be used to verify whether LPP3 changes energy metabolism in these tissues in the living organism. Comprehensive metabolite analysis will be performed by mass spectrometry. Mitochondrial dynamics and degradation will also be assessed. This research will provide new insight into the biological role of autotaxin and LPP3 and elucidate how these lysophospholipases impact energy metabolism and mitochondrial maintenance and function.