Department of Cellular Signaling, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawińskiego 5, PL 02-106 Warszawa, Poland.
Pharmacol Rep. 2009 Nov-Dec;61(6):1078-85. doi: 10.1016/s1734-1140(09)70170-7.
alpha-Synuclein (ASN), a small presynaptic protein that is abundant in the brain, is implicated in the pathogenesis of neurodegenerative disorders including Parkinson's and Alzheimer's disease. The central domain of alpha-synuclein, the non-amyloid beta component of the Alzheimer's disease amyloid (NAC) is probably responsible for its toxicity. However, the molecular mechanism of alpha-synuclein action remains largely elusive. The present study examined the effect of alpha-synuclein and the NAC peptide on nitric oxide synthase (NOS) activity in rat brain cortical and hippocampal slices using a radiochemical technique. Moreover, nitrite levels in brain slices incubated in the presence of alpha-synuclein were measured using the Griess reaction. ASN and the NAC stimulated NOS activity by about 70% and 40%, respectively. beta-Synuclein, a homologous protein of ASN that lacks the NAC domain, had no effect on NOS activity. Under the same experimental conditions, alpha-synuclein increased nitrite levels by 27%. alpha-Synuclein and the NAC affected the activity of constitutive neuronal isoform of NOS, but had no impact on the endothelial or inducible NOS isoforms. The effect of alpha-synuclein and the NAC peptide on NOS activity was inhibited by MK-801 and APV, antagonists of the NMDA receptor. These results indicate that the NMDA receptor plays an important role in alpha-synuclein-evoked nitric oxide synthesis. We suggest that nitric oxide liberated by the over-activated neuronal isoform of NOS could react with superoxide to form peroxynitrite, which modulates the function of a variety of biomolecules including proteins, lipids, and DNA.
α-突触核蛋白（ASN）是一种丰富存在于大脑中的小突触前蛋白，与包括帕金森病和阿尔茨海默病在内的神经退行性疾病的发病机制有关。α-突触核蛋白的中心结构域，即阿尔茨海默病淀粉样蛋白的非淀粉样β成分（NAC），可能与其毒性有关。然而，α-突触核蛋白的作用的分子机制在很大程度上仍然难以捉摸。本研究使用放射化学技术研究了α-突触核蛋白和 NAC 肽对大鼠大脑皮质和海马切片中一氧化氮合酶（NOS）活性的影响。此外，使用格里斯反应测量了在存在α-突触核蛋白的情况下孵育的脑切片中的亚硝酸盐水平。ASN 和 NAC 分别使 NOS 活性增加约 70%和 40%。β-突触核蛋白是 ASN 的同源蛋白，缺乏 NAC 结构域，对 NOS 活性没有影响。在相同的实验条件下，α-突触核蛋白使亚硝酸盐水平增加了 27%。α-突触核蛋白和 NAC 影响组成型神经元同工型的 NOS 活性，但对内皮型或诱导型 NOS 同工型没有影响。MK-801 和 APV 抑制了α-突触核蛋白和 NAC 肽对 NOS 活性的影响，MK-801 和 APV 是 NMDA 受体的拮抗剂。这些结果表明，NMDA 受体在α-突触核蛋白诱导的一氧化氮合成中起重要作用。我们认为，过激活的神经元同工型 NOS 释放的一氧化氮可能与超氧化物反应形成过氧亚硝酸盐，从而调节包括蛋白质、脂质和 DNA 在内的多种生物分子的功能。
