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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Monomeric inducible nitric oxide synthase localizes to peroxisomes in hepatocytes
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Monomeric inducible nitric oxide synthase localizes to peroxisomes in hepatocytes

机译：单体诱导型一氧化氮合酶定位于肝细胞中的过氧化物酶体

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摘要

Hepatocytes are capable of repeated inducible NO synthase (NOS) expression, which occurs under inflammatory and stress conditions. This NOS expression regulates a number of cellular functions as well as cell viability. To better understand the posttranslational mechanisms that regulate the fate of NOS in these cells, we characterized the NOS distributed within peroxisomes. The selective permeabilization of membranes (plasma vs. peroxisomal) confirmed that there are cytosolic and peroxisomal pools of NOS in cytokine-stimulated hepatocytes and that the MOS protein associates with peroxisome. Detergent solubilization of the membrane fraction released NOS to the soluble fraction. NOS localized to membrane fraction is predominantly monomeric, but dimerization is partially reconstituted rapidly upon incubation with tetrahydrobiopterin. The reconstituted NOS exhibits a lower specific activity than NOS isolated from the soluble pool. Depletion of intracellular tetrahydrobiopterin with an inhibitor of de novo pterin synthesis resulted in a predominance of monomeric MOS without a greater relative distribution of MOS to the peroxisomal pool. Thus, NOS exists in a least two pools in hepatocytes: a soluble pool composed of both active dimer and monomer and a peroxisomal pool of monomeric MOS. MOS might localize to peroxisomes in long-lived cells such as hepatocytes as a protective mechanism to remove incompetent enzyme.
机译：肝细胞能够重复诱导型NO合酶（NOS）表达，这种表达在炎症和压力条件下发生。该NOS表达调节许多细胞功能以及细胞活力。为了更好地理解调节这些细胞中NOS命运的翻译后机制，我们表征了过氧化物酶体中分布的NOS。膜的选择性通透性（血浆与过氧化物酶体）证实，在细胞因子刺激的肝细胞中存在NOS的胞质和过氧化物酶体库，并且MOS蛋白与过氧化物酶体结合。膜部分的去污剂溶解将NOS释放到可溶部分。定位于膜部分的NOS主要是单体，但是在与四氢生物蝶呤孵育后，二聚化会快速地部分重构。重构的NOS的比活性低于从可溶性库中分离的NOS的比活性。用新蝶呤合成抑制剂消耗细胞内四氢生物蝶呤导致单体MOS占优势，而MOS到过氧化物酶体池的相对分布更大。因此，NOS存在于肝细胞的至少两个库中：一个由活性二聚体和单体组成的可溶性库和一个过氧化物酶体的单体MOS库。 MOS可能会定位于长寿细胞（例如肝细胞）中的过氧化物酶体，作为去除不适合的酶的保护机制。

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