The degradation (by distinct pathways) of human D-amino acid oxidase and its interacting partner pLG72-two key proteins in D-serine catabolism in the brain
The degradation (by distinct pathways) of human D-amino acid oxidase and its interacting partner pLG72-two key proteins in D-serine catabolism in the brain
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DOI：
10.1111/febs.12616
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发表时间：
2014-02-01
期刊：
影响因子：
5.4
通讯作者：
Sacchi, Silvia
中科院分区：
文献类型：
--
作者：
Cappelletti, Pamela;Campomenosi, Paola;Sacchi, Silvia
人 D-氨基酸氧化酶（EC 1.4.3.3；hDAAO）是一种在哺乳动物大脑中显着富集的过氧化物酶体黄素酶。 hDAAO 已被提议在 D-丝氨酸的分解代谢中发挥重要作用（与丝氨酸消旋酶；EC 5.1.1.18），D-丝氨酸是一种“非典型”关键信号分子，充当 N-甲基-D-天冬氨酸型谷氨酸受体 (NMDAr) 的变构激活剂。 hDAAO 及其相互作用伙伴 pLG72 与精神分裂症有关，精神分裂症是一种高度致残的精神疾病，人们普遍认为其中发生了 NMDA 介导的神经传递功能障碍。我们之前证明，D-丝氨酸细胞浓度取决于 hDAAO 和 pLG72 表达水平，并且新合成的 hDAAO 与其胞浆中的调节剂相互作用，逐渐不稳定和失活。为了深入了解调节细胞 D-丝氨酸水平的机制，我们研究了稳定表达增强型黄色荧光蛋白-hDAAO（过氧化物酶体）、hDAAO 增强型黄色荧光蛋白（胞质）或 pLG72-增强型青色荧光蛋白（线粒体）蛋白的 U87 胶质母细胞瘤细胞中 hDAAO 和 pLG72 的降解途径。 hDAAO 是一种长寿命蛋白质：这种黄素蛋白的过氧化物酶体部分通过溶酶体/内体途径降解（阻断该途径会增加细胞 hDAAO 活性并降低 D-丝氨酸水平），而胞质部分则被泛素化并靶向蛋白酶体。相比之下，pLG72 显示出快速周转（t(1/2) 大约为 25-40 分钟）并通过蛋白酶体系统降解，尽管未泛素化。 pLG72 的过度表达增加了 hDAAO 的周转，进而对 D-丝氨酸过度消耗发挥保护作用。
Human D-amino acid oxidase (EC 1.4.3.3; hDAAO) is a peroxisomal flavoenzyme significantly enriched in the mammalian brain. hDAAO has been proposed to play (with serine racemase; EC 5.1.1.18) an essential role in the catabolism of D-serine, an 'atypical' key signalling molecule that acts as allosteric activator of the N-methyl-D-aspartate-type glutamate receptor (NMDAr). hDAAO and its interacting partner pLG72 have been related to schizophrenia, a highly disabling psychiatric disorder in which a dysfunction of NMDA-mediated neurotransmission is widely assumed to occur. We previously demonstrated that the D-serine cellular concentration depends on hDAAO and pLG72 expression levels and that newly-synthesized hDAAO interacts with its modulator in the cytosol, being progressively destabilized and inactivated. To obtain insight into the mechanisms regulating cellular D-serine levels, we investigated the degradation pathways of hDAAO and pLG72 in U87 glioblastoma cells stably expressing enhanced yellow fluorescent protein-hDAAO (peroxisomal), hDAAO-enhanced yellow fluorescent protein (cytosolic) or pLG72-enhanced cyan fluorescent protein (mitochondrial) proteins. hDAAO is a long-lived protein: the peroxisomal fraction of this flavoprotein is degraded via the lysosomal/endosomal pathway (and blocking this pathway increases the cellular hDAAO activity and decreases D-serine levels), whereas the cytosolic portion is ubiquitinated and targeted to the proteasome. By contrast, pLG72 shows a rapid turnover (t(1/2) approximate to 25-40 min) and is degraded via the proteasome system, albeit not ubiquitinated. Overexpression of pLG72 increases the turnover of hDAAO, in turn playing a protective role against excessive D-serine depletion.