Lysophospholipid metabolism and signalling - role of lysophospholipases

生物活性脂肪（脂质）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）自分泌运动因子产生。我们的工作建立了autotaxin-LPA途径与哺乳动物能量代谢之间的联系。我们发现，自分泌运动因子受营养素和胰岛素的影响，自分泌运动因子-LPA途径阻碍了线粒体的功能，线粒体是细胞的动力。目前尚不清楚这种途径如何精确地影响线粒体的维持和功能。脂质磷酸磷酸酶3（LPP 3）是分解LPA的溶血磷脂酶。LPP 3是胚胎形成所必需的，并以其在血管发育和功能中的作用而闻名。LPP 3存在于具有高能量代谢的组织中，包括肌肉和脂肪，并且涉及糖代谢。然而，LPP 3，线粒体功能和能量代谢之间的关系在很大程度上是未知的。 本研究的总体目标是研究autotaxin和LPP 3在哺乳动物能量代谢和线粒体维护和功能中的作用。使用暴露于LPA的培养的哺乳动物脂肪和肌肉细胞以及来自具有降低的自分泌运动因子水平的小鼠的脂肪和肌肉组织，我们将测试自分泌运动因子-LPA途径是否影响线粒体的融合和分裂。这一过程被称为线粒体动力学，与线粒体能量代谢和功能有关。将通过电子显微镜评估线粒体结构。将使用免疫印迹技术测量涉及线粒体动力学的蛋白质。荧光显微镜将使我们能够可视化活细胞中的线粒体融合和分裂。通过阻断不同的LPA受体，我们将确定哪些受体参与自分泌运动因子-LPA介导的线粒体动力学变化。我们还将评估自分泌运动因子-LPA是否通过线粒体自噬改变线粒体降解。使用小鼠和大鼠，我们将确定LPP 3水平和活性是否会随进食/禁食而变化。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LPP 3。我们还将使用显微镜监测LPP 3定位到细胞区室的变化。将使用标记底物和线粒体呼吸测定法检查LPP 3增加和减少对营养素吸收和氧化的影响。具有LPP 3的肌肉和脂肪特异性增加的小鼠将用于验证LPP 3是否改变活生物体中这些组织中的能量代谢。将通过质谱法进行全面的代谢物分析。还将评估线粒体动力学和降解。这项研究将为autotaxin和LPP 3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.