Mitochondrial rRNA Methylation: Effects of ethanol/SAMe

描述(由申请人提供)：建议调查长期摄入酒精会导致肝脏S-腺苷-L-蛋氨酸(Adomet)水平下降的假说，以及这种缺陷会导致线粒体核糖体组装受损和蛋白质合成受抑。已发表的数据表明，乙醇对肝脏中的氧化磷酸化有显著影响。酒精摄入会导致必需多肽水平的降低，这些多肽仅由线粒体基因组编码，用于组装电子传输链(ETC)复合体。其结果是，它们的活性受到抑制，三磷酸腺苷的产生减少，对这一现象的机制的研究(S)揭示了乙醇引起的全功能线粒体核糖体(有丝分裂体)数量的减少以及分离后线粒体核糖体解离的增加，这表明乙醇介导的线粒体多肽翻译水平的效应可能是酒精性肝病进展过程中能量代谢受损的机制之一。线粒体核糖体的组装需要核编码蛋白和线粒体 编码的核糖体RNA(RRNA)颗粒。它还需要rRNA中少量核苷酸的位点特异性甲基化，这是一个利用Adomet的过程。已公布的数据表明，长期摄入乙醇会导致细胞腺多角体耗尽，这可能会对核糖体组装产生重大影响。此外，我们小组的研究表明，慢性酒精喂养2岁的雄性大鼠14天后，电子传递链复合体I的活性显著下降，并可通过同时使用Adomet来改善。拟议的研究将：(A)研究rRNA甲基化对核糖体组装和功能的意义；(B)研究慢性酒精摄入对rRNA甲基化的影响；以及(C)对线粒体rRNA甲基转移酶活性的影响。(B)和(C)项研究的影响也将被调查。希望这些分析将为线粒体蛋白翻译在ALD进展中的作用提供一个独特的见解。

DESCRIPTION (provided by applicant): It is proposed to investigate the hypothesis that chronic ethanol feeding results in decreased levels of hepatic S-adenosy-L-methionine (Adomet) and that this deficiency results in impaired mitochondrial ribosome assembly and depressed protein synthesis. Published data has demonstrated that ethanol has a pronounced effect upon oxidative phosphorylation in the liver. Ethanol consumption results in decreased levels of essential polypeptides encoded for: exclusively by the mitochondrial genome-that are utilized in the assembly of electron transport chain (ETC) complexes. As a consequence, their activities are depressed and ATP production decreases, investigations is to the mechanism(s) responsible for the phenomenon revealed an ethanol-elicited decrease in the number of fully functioning mitochondrial ribosomes (mitoribosomes) along with an increased tendency for them to dissociate upon isolation, This suggests that iethanol-mediated effects at the level of mitochondrial polypeptide translation may be one of the underlying imechanisms involved in the impairment of energy metabolism seen during the progression of alcoholic liver disease (ALD). Assembly of mitochondrial ribosomes requires nuclear encoded proteins and mitochondriaUy encoded ribosomal RNA (rRNA) particles. It also requires site-specific methylation of a small number of nucleotides within the rRNA, a process that utilizes Adomet. Published data has shown that chronic ethanol consumption results in depletion of cellular Adomet, which may have significant consequences for ribosome assembly. Further, studies from our group have shown that chronic ethanol-feeding to 2 year old male rats for 14 days results in a significant decrease in the activity of complex I of the electron transport chain and that this can be ameliorated by concomitant treatment with Adomet. The proposed studies will (a) investigate the significance of rRNA methylation upon ribosome assembly and function; (b) investigate the effect of chronic ethanol-feeding upon rRNA methylation; and (c) upon the activity of mitochondrial rRNA methyltransferases. The effect of Adomet feeding upon the studies in (b) and (c) will also be investigated. It is hoped that these analyses will provide a unique insight into the role of mitochondrial protein translation I the progression of ALD.