Brain ischemia attenuates neuropeptide biosynthesis

描述(申请人提供)：神经肽在维持大脑的正常功能和大脑对应激(如缺血)的反应中起着至关重要的作用。几乎所有已知的神经肽都是由较大的前体通过分泌途径中的一组加工酶的作用来加工的。前体形式的生物学功能可能与最终加工形式的生物学功能有很大的不同，甚至包括从促凋亡功能而不是抗凋亡功能的切换。关于神经肽的生物合成过程如何受到脑内缺血应激的影响，人们知之甚少。我们的初步研究表明，缺血导致关键神经肽加工酶的激活减弱，并以前体形式积累某些神经肽。我们的假设是：缺血对神经肽处理系统的功能状态产生不利影响，从而损害脑细胞产生某些保护性多肽因子的能力。这种由缺血引起的神经肽加工的减弱导致了脑缺血后细胞的死亡。在这项拟议的研究中，我们将首先检测缺血大鼠脑内几种关键神经肽加工酶的表达水平及其酶活性的变化。然后，我们将确定已知的神经肽的水平和分子形式，这些神经肽在脑缺血后具有调节作用，并需要本研究中研究的加工酶的作用才能进行适当的加工。利用培养细胞的体外缺血模型，我们将研究缺血应激如何影响加工酶的激活和成熟过程，以及改变神经肽的产生和分泌。同时，我们将使用定量蛋白质组学方法分析从缺血细胞分泌的多肽。最后，我们将调查神经肽加工特定缺陷的动物是否更容易受到缺血应激的影响，并确定加工缺陷神经细胞分泌的多肽是否会导致或夸大缺血细胞的死亡。这项拟议的研究将提供一种新的机制，说明缺血性中风如何通过减弱神经肽的处理来损害大脑。我们的长期目标是阐明神经肽处理介导的大脑应激反应的分子机制。

DESCRIPTION (provided by applicant): Neuropeptides play crucial roles in maintaining normal function of the brain and the brain's response to stresses, e.g. ischemia. Virtually all known neuropeptides are processed from larger precursors by the action of a set of processing enzymes in the secretory pathway. The biological function of precursor forms may differ profoundly from that of final processed forms to include even a switch from pro-apoptotic rather than anti-apoptotic function. Little is known about how the biosynthetic processing of neuropeptides may be affected by ischemic stress in the brain. Our preliminary studies indicate that ischemia causes attenuation in the activation of key neuropeptide processing enzymes and an accumulation of certain neuropeptides in precursor forms. Our hypothesis is: ischemia has adverse effects on the functional status of the neuropeptide processing system, thus impairing the ability of brain cells to produce certain protective peptide factors. This ischemia-induced attenuation of neuropeptide processing contributes to post-ischemia cell death in the brain. In the proposed study, we will first examine changes in the expression levels of several key neuropeptide processing enzymes and their enzymatic activities in ischemic rat brains. Then, we will determine the levels and molecular forms of neuropeptides that are known to have modulatory roles in the brain after ischemia and to require the action of processing enzymes investigated in this study for proper processing. Using in vitro ischemia models in cultured cells, we will investigate how ischemic stress may influence the activation and maturation processes of the processing enzymes and alter the production and secretion of neuropeptides. In parallel, we will analyze peptides secreted from ischemic cells using a quantitative proteomic approach. Finally, we will investigate if animals with specific deficiencies in neuropeptide processing may be more vulnerable to ischemic stress and determine if peptides secreted from processing-deficient neuronal cells may cause or exaggerate ischemic cells death. The proposed study will offer a novel mechanism concerning how ischemic stroke may damage the brain by attenuating neuropeptide processing. Our long-term goal is to elucidate the molecular mechanisms of neuropeptide processing-mediated stress response of the brain.