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。它在从发热到繁殖的许多过程中起着关键作用。它是如此重要，以至于不能制造花生四烯酸的动物，比如猫，必须是食肉动物，然后从它们吃的肉中获取花生四烯酸。然而，人类可以从含有亚油酸的植物油中制造亚油酸。在我们体内，花生四烯酸隐藏在我们的细胞壁内。一种叫做磷脂酶A2的特殊蛋白质负责向我们的细胞提供花生四烯酸。在磷脂酶A2家族中，胞质磷脂酶A2是非常重要的，可能是因为它在我们体内无处不在。因此，了解胞质磷脂酶A2是如何工作的，对于理解生命本身赖以维持的生理机制是非常有帮助的。我们合理地理解了胞质磷脂酶A2是如何释放花生四烯酸的。然而，我们并不真正知道胞质磷脂酶A2是如何停止释放花生四烯酸的。这一点非常重要，因为花生四烯酸不足或过多都可能是致命的。我们的研究项目旨在了解胞质磷脂酶A2如何停止向花生四烯酸释放。在这方面，我们建议定义两种途径，使胞质磷脂酶A2的活性下降。***第一种方法意味着通过添加磷酸基团对胞质磷脂酶A2进行直接修饰。这可能导致花生四烯酸释放显著减少。第二种方法涉及花生四烯酸本身，它可能会诱导胞质磷脂酶A2停止释放它。这种溯及性抑制从未有过文献记载。我们能够以纯形式设计胞质磷脂酶A2，因此可以对后者进行许多测试。因此，我们期望使用生物化学分子生物学技术来定义两个重要的停止信号，通过这些信号，胞质磷脂酶A2的活性被关闭。***好处是巨大的，因为1)它将提供花生四烯酸如何释放的关键方面，2)它将培养生物化学和脂质谱领域的高素质人才，这是加拿大科学界中代表性不足的研究领域。***总之，该项目将为胞质磷脂酶A2的调控，特别是其与膜的相互作用提供重要的见解。这也将为了解脂质介质的生物合成及其在生理中的作用提供有用的数据，并可能确定花生四烯酸是胞质磷脂酶A2释放的中心调节剂

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.**