PARKINSONISM--A METHYL-DONOR ACTION FOR MPP+

1-甲基-4-苯基-1，2，3，6-四氢吡啶（MPP+）和1-甲基-4- 苯基吡啶（Mpp+）引起帕金森病（PD）样症状。 最近，据观察，注射过量的S- 啮齿类动物脑中的腺苷甲硫氨酸（SAM）也引起PD样 方面的影响. SAM是内源性甲基供体，需要S-甲基 集团的活动。 MPTP和MPP+也需要它们的N-甲基基团 为他们的活动。 因此，像SAM一样，MPP+是主动的 MPTP的代谢产物，可以作为甲基供体。 这一理念得到加强 由于MPP+的离子状态有利于其作为甲基的作用， 供体 在我们的实验室中，我们发现MPP+，而不是MPTP，可以捐赠 甲基多巴胺（DA），这表明MPP+可以作为 甲基供体。 这种作用可能与MPP+的直接作用有关 以及缺乏MPTP的直接作用。 作为一个甲基供体，它也意味着 像SAM一样，MPP+可以甲基化磷脂（PL）和蛋白质。 的 PL和蛋白质的甲基化可能会破坏细胞膜， 胞吐作用和其他功能，这沿着甲基化的其他 细胞成分，如多巴胺（DA）可能是毒性的基础。 MPP+。 在本项目中，MPTP、MPP+和SAM作为甲基的能力 将研究和比较DA、PL和蛋白质的供体。 的方法 将涉及使用部分纯化的COMT和HPLC进行体外测定 方法，测定MPTP、MPP+和SAM甲基化DA的能力。 在脑细胞中研究PL和蛋白质的甲基化 细胞膜、细胞质和突触体。 PL的特征将使用 薄层色谱 MPP+甲基化的拮抗剂和MPP+对SAM-的影响 还将测定依赖性甲基化。 此外，效果 比较MPTP、MPP+和SAM对DA释放的影响， 甲基化DA、PL和蛋白质的能力。 如果可以证实一般甲基供体对MPP+的作用， 结果将构成一个重要的发现，这将有助于我们了解 更多关于PD以及衰老和细胞寿命，因为有一个 衰老、PD、细胞寿命和细胞凋亡之间存在密切的相互关系， 关于MPP+甲基化受到严格的调控，部分是由限制性的 SAM的存在。 稳定甲基供体（MPP+）的鉴定 将增加一种新的合理的生物化学方法， 推动了MPTP类化合物、PD和甲基化的研究; 注意到甲基化参与调节重要的 生物分子，包括核酸，蛋白质，脂类，碳水化合物， 单胺，乙酰胆碱-以及调节功能，例如， 转录沉默，衰老，胞吐，生物胺调节和 膜生物物理学

One-methyl-4-phenyl-1,2,3,6,-tetrahydropyridine (MPP+) and 1-methyl-4- phenylpyridinium (Mpp+) caused Parkinson's disease (PD)-like symptoms. Recently, it was observed that the injection of excess S- adenosylmethionine (SAM) in the brain of rodents also caused PD-like effects. SAM is the endogenous methyl donor and requires the S-methyl group for its activity. MPTP and MPP+ also require their N-methyl groups for their activities. Therefore, like SAM, MPP+, which is the active metabolite of MPTP, may serve as a methyl donors. This idea is enhanced by the fact that the ionic state of MPP+ favors its action as a methyl donor. In our laboratory we found that MPP+, but not MPTP, can donate a methyl group to dopamine (DA), which shows that MPP+ can serve as a methyl donor. Such an effect may be related to the direct action of MPP+ and the lack of direct action of MPTP. As a methyl donor, it means also that, like SAM, MPP+ may methylate phospholipids (PL) and proteins. The methylation of PL and proteins may disrupt cell membranes, affecting exocytosis and other functions, which along with the methylation of other cellular constituents, e.g. dopamine (DA) may underlie the toxicity of MPP+. In this project the ability of MPTP, MPP+ and SAM to serve as methyl donors for DA, PL and proteins will be studied and compared. The methods will involve in vitro assays, using partially purified COMT, and HPLC methods, to determine the ability of MPTP, MPP+ and SAM to methylate DA. The methylation of PL and proteins will be studied in brain cell membranes, cytosol and synaptosomes. The PL will be characterized using TLC. Antagonists to MPP+ methylation and the effects of MPP+ on SAM- dependent methylation will also be determined. In addition, the effect of MPTP, MPP+ and SAM on the release of DA will be compared with their ability to methylate DA, PL and proteins. If the role of a general methyl donor can be substantiated for MPP+ the results will constitute a significant finding that will help us to know more about PD as well as aging and cell longevity, because there is a close interrelationship between aging, PD, cell longevity and the action of MPP+. Methylation is tightly regulated, in part, by the limiting existence of SAM. The identification of a stable methyl donor (MPP+) will add a new rational biochemical approach and will generate much impetus in the study of the MPTP class of compounds, PD and methylation; noting that methylation is involved in the regulation of important biomolecules--including nucleic acids, proteins, lipids, carbohydrates, monoamines, acetylcholine--as well as regulatory function, e.g. transcriptional silence, aging, exocytosis, biogenicamines regulation and membrane biophysics.