Choline-dependent metabolism in PNS myelination

摘要 细胞合成胆碱的能力有限，因此细胞依赖于 蛋白质转运蛋白来输入胆碱胆碱用于合成 磷脂酰胆碱，髓鞘的结构脂质成分是从磷脂酰胆碱中提取的。 合成了磷脂酰胆碱也被代谢产生 磷脂酰肌醇，其磷酸化衍生物是重要的 调节髓鞘形成的信号脂质。胆碱参与合成 组蛋白的通用甲基供体S-腺苷甲硫氨酸（SAM） 和DNA甲基化，从而调节基因表达。考虑 胆碱在磷脂生物合成的十字路口的位置 和表观遗传调控，我们对这些基因的 胆碱输入和胆碱依赖性代谢的调节 髓鞘形成的神经胶质细胞。施万细胞的胆碱转运蛋白尚未被发现。 鉴定 我们已经确定胆碱样转运蛋白1（CTL 1）是一种重要的 雪旺氏细胞髓鞘形成的调节剂。雪旺细胞中的CTL 1缺失 （CTL 1 sc-KO）导致PNS中局灶性高髓鞘形成的早期发作。 生化分析显示，胆碱衍生的 髓鞘中的磷脂此外，CTL 1缺失损害髓鞘 基因表达，并表现出改变的DNA修饰在雪旺细胞。根据这些观察，我们 假设CTL 1是雪旺细胞胆碱转运蛋白。我们还假设胆碱依赖性 代谢进入磷脂信号和表观遗传修饰，这是重要的 髓鞘形成为此，我们将调查三个方面的胆碱代谢的雪旺细胞髓鞘。 目的1将检验CTL 1是雪旺细胞胆碱转运蛋白的假设。MALDI-TOF和串联 将进行质谱分析以直接测量输入到CTL 1 sc-KO许旺细胞中的胆碱。 还将分析CTL 1损失对磷脂酰胆碱合成的影响。在目标2中，我们将测试 假设CTL 1 sc-KO小鼠中髓鞘缺陷是由PI（3，5）P2和PI（3，4，5）P3失衡引起的 合成.这是基于观察到磷脂酰肌醇含量在CTL 1 sc-KO神经中改变 并且髓鞘形成缺陷类似于在PI（3，5）P2和PI（3，4，5）P3失调的小鼠中观察到的那些 合成.目的3将检验这样的假设，即CTL 1的缺失通过调节细胞因子的表达来改变雪旺细胞中的基因表达。 组蛋白和DNA甲基化。 包括胆碱在内的脂质代谢紊乱是许多遗传性疾病的潜在机制 与PNS髓鞘形成缺陷有关。此外，磷脂的膳食补充剂已被广泛应用于食品中。 被认为是治疗PNS神经病的潜在治疗选择。因此，本研究的结果 将为理解胆碱代谢在发育中的意义提供重要的见解。 治疗PNS神经病变的治疗策略。

ABSTRACT Cells have a limited capacity to synthesize choline, thus cells depend on protein transporters to import choline. Choline is used to synthesize phosphatidylcholine, from which structural lipid components of myelin are synthesized. Phosphatidylcholine is also metabolized to generate phosphotidylinositols, whose phosphorylated derivatives are important signaling lipids that regulate myelination. Choline is involved in synthesis of the universal methyl donor, S-adenosylmethionine (SAM) for histone and DNA methylation, thus regulating gene expression. Considering the position of choline at the crossroad for the biosynthesis of phospholipids and epigenetic regulation, we have very little to no understanding of the regulation of choline import and choline-dependent metabolism in myelinating glial cells. Choline transporter for Schwann cells has not been identified. We have identified choline-like-transporter 1 (CTL1) as an important regulator of Schwann cell myelination. CTL1 deletion in Schwann cells (CTL1sc-KO) results in early onset of focal hyper-myelination in the PNS. Biochemical analysis revealed an overall decrease in choline-derived   phospholipids in the myelin. Furthermore, CTL1 loss impaired myelin gene expression and exhibited altered DNA modifications in Schwann cells. From these observations, we hypothesize that CTL1 is a Schwann cell choline transporter. We also hypothesize that choline-dependent metabolism feeds into the phospholipid signaling and epigenetic modifications that are important for myelination. To this end, we will investigate three aspects of choline metabolism in Schwann cell myelination. Aim 1 will test the hypothesis that CTL1 is a Schwann cell choline transporter. MALDI-TOF and tandem mass spectrometry will be performed to directly measure choline import into CTL1sc-KO Schwann cells. Impact of CTL1 loss on phosphatidylcholine synthesis will also be analyzed. In Aim 2, we will test the hypothesis that myelin defects in CTL1sc-KO mice results from imbalance in PI(3,5)P2 and PI(3,4,5)P3 synthesis. This is based on the observation that phosphatidylinositol contents are altered in CTL1sc-KO nerve and the myelination defects resemble those seen in mice with dysregulated PI(3,5)P2 and PI(3,4,5)P3 synthesis. Aim 3 will test the hypothesis that CTL1 loss alters gene expression in Schwann cells by modulating histone and DNA methylation. Perturbed lipid metabolism, including choline, is an underlying mechanism in many hereditary diseases associated with PNS myelination defects. Furthermore, dietary supplement of phospholipids has been considered as a potential therapeutic option for treating PNS neuropathies. Therefore, results from this study will provide important insights into understanding the implication of choline metabolism in developing therapeutic strategies to treat PNS neuropathies.