Cellular and molecular mechanisms involved in the regulation of group IVA phospolipase A2

花生四烯酸是一种主要存在于动物体内的脂肪酸。它在许多过程中发挥着关键作用，从发烧到生殖。这一点非常重要，不能做到这一点的动物，如猫，是强制性的肉食性动物，然后从它们吃的肉中获得花生四烯酸。然而，人类可以用含有亚油酸的植物油来制作它。在我们的体内，花生四烯酸隐藏在我们的细胞壁中。被称为磷脂酶A2的特殊蛋白质负责为我们的细胞提供花生四烯酸。在磷脂酶A2家族中，胞浆磷脂酶A2是非常重要的，可能是因为它在我们的身体中无处不在。因此，了解胞质磷脂酶A2是如何工作的，对于理解维持生命本身的生理机制是非常有帮助的。 我们合理地理解了胞浆磷脂酶A2是如何释放花生四烯酸的。然而，我们并不知道胞浆磷脂酶A2是如何停止释放花生四烯酸的。这一点非常重要，因为花生四烯酸过少或过多都可能是致命的。我们的研究计划旨在了解胞浆磷脂酶A2如何停止释放到花生四烯酸。在这方面，我们建议定义两种降低胞浆磷脂酶A2活性的方法。 第一种方式意味着通过添加磷酸基团直接修饰胞浆磷脂酶A2。这可能会导致花生四烯酸释放显著减少。第二种方式涉及花生四烯酸本身，它可能会诱导胞浆磷脂酶A2停止释放它。这种具有追溯效力的抑制从未被记录在案。我们能够设计出纯形式的胞浆磷脂酶A2，因此可以对后者进行许多测试。因此，我们期望利用生化分子生物学技术定义两个重要的停止信号，通过它们来关闭胞质磷脂酶A2的活性。 好处是巨大的，因为1)它将提供有关花生四烯酸如何释放的关键方面，2)它将培训生物化学和脂类质谱学领域的高素质人员，这是一个在加拿大科学界很少代表的研究领域。 总之，该项目将对胞浆磷脂酶A2的调节提供重要的见解，特别是关于它与细胞膜的相互作用。这也将为理解脂质介质的生物合成及其在生理学中的作用提供有用的数据，并可能确定花生四烯酸是胞浆磷脂酶A2释放的中央调节因子。

Arachidonic acid is fatty acid mainly found in animals. It plays critical roles in many processes, from fever to reproduction. It is so important that animals that can't make it, such as the cat, are obligatory carnivorous and then get the arachidonic acid from the meat they eat. Humans can however make it from vegetable oil containing linoleic acid. In our body, arachidonic acid is hidden within our cell walls. Special proteins named phospholipases A2 are responsible for providing arachidonic acid to our cells. Among the phospholipases A2 family, the cytosolic phospholipase A2 is very important, probably because it is found everywhere in our body. Thus, understanding how the cytosolic phospholipase A2 works is very helpful in order to understand the physiological mechanisms by which life itself is sustained. We reasonably understand how the cytosolic phospholipase A2 releases arachidonic acid. However, we do not really know how the cytosolic phospholipase A2 stops releasing arachidonic acid. This is very important because not enough or too much arachidonic acid can be lethal. Our research program aims at understanding how the cytosolic phospholipase A2 stops releasing to arachidonic acid. In this regard, we are proposing to define 2 ways by which the activity of cytosolic phospholipase A2 is turned down. The first way implies a direct modification of the cytosolic phospholipase A2 by adding a phosphate group. This likely leads to a significant decrease in arachidonic acid release. The second way involves arachidonic acid itself, which might induce the cytosolic phospholipase A2 to stop releasing it. Such a retroactive inhibition has never been documented. We were able to engineer the cytosolic phospholipase A2 in a pure form and can therefore perform many tests on the latter. We thus anticipate to define, using biochemistry molecular biology techniques, two important stop signals by which the activity of the cytosolic phospholipase A2 is turned off. The benefits are immense as 1) it will provide key aspects on how arachidonic acid is released and 2) it will train highly qualified personnel in the field of biochemistry and mass spectrometry of lipids, a research area that is poorly represented among the Canadian scientific community. In conclusion, this project will provide important insights on the regulation of the cytosolic phospholipase A2, notably about its interaction with the membranes. It will also provide useful data for the understanding of lipid mediator biosynthesis and their role in physiology and might define arachidonic acid as a central regulator of cytosolic phospholipase A2 release.