Complex formation of sphingomyelin synthase 1 with glucosylceramide synthase increases sphingomyelin and decreases glucosylceramide levels
Complex formation of sphingomyelin synthase 1 with glucosylceramide synthase increases sphingomyelin and decreases glucosylceramide levels
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DOI：
10.1074/jbc.ra118.002048
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发表时间：
2018-11-09
影响因子：
4.8
通讯作者：
Yamashita, Atsushi
中科院分区：
文献类型：
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作者：
Hayashi, Yasuhiro;Nemoto-Sasaki, Yoko;Yamashita, Atsushi
鞘脂，包括鞘磷脂（SM）和葡糖神经酰胺（GlcCer），通过向神经酰胺（Cer）添加极性头部基团而产生。鞘磷脂合酶1（SMS 1）和葡糖神经酰胺合酶（GCS）是分别催化Cer转化为SM和GlcCer的关键酶。GlcCer的合成被认为主要发生在顺式高尔基体中，SM的合成被认为发生在内侧/反式高尔基体中;然而，已知SMS 1和GCS部分共定位于脑池，特别是内侧/反式高尔基体中。在这里，我们报告说，SMS 1和GCS可以形成一个异聚体复合物，其中的N末端的SMS 1和GCS的C末端是非常接近的。SMS 1的N-末端不育基序的缺失降低了SMS 1-GCS复合物的稳定性，导致体内SM合成的显著减少。相比之下，化学诱导的异源二聚化增强了SMS 1活性，这取决于复合物的量和稳定性的增加。通过不同长度的接头将SMS 1 N末端融合到GCS C末端增加了体内SM合成并减少了GlcCer合成。这些结果表明，形成的SMS 1-GCS异聚体复合物增加SM合成和减少GlcCer合成。重要的是，SMS 1-GCS复合物对相对Cer水平的这种调节通过CRISPR/Cas9介导的SMS 1或GCS敲除结合HEK 293 T细胞中Cer转运蛋白的药理学抑制来证实。我们的研究结果表明，SMS 1和GCS之间的复合物的形成是一个关键机制的一部分，控制在高尔基体的Cer的代谢命运。
Sphingolipids, including sphingomyelin (SM) and glucosylceramide (GlcCer), are generated by the addition of a polar head group to ceramide (Cer). Sphingomyelin synthase 1 (SMS1) and glucosylceramide synthase (GCS) are key enzymes that catalyze the conversion of Cer to SM and GlcCer, respectively. GlcCer synthesis has been postulated to occur mainly in cis-Golgi, and SM synthesis is thought to occur in medial/trans-Golgi; however, SMS1 and GCS are known to partially co-localize in cisternae, especially in medial/trans-Golgi. Here, we report that SMS1 and GCS can form a heteromeric complex, in which the N terminus of SMS1 and the C terminus of GCS are in close proximity. Deletion of the N-terminal sterile -motif of SMS1 reduced the stability of the SMS1-GCS complex, resulting in a significant reduction in SM synthesis in vivo. In contrast, chemical-induced heterodimerization augmented SMS1 activity, depending on an increase in the amount and stability of the complex. Fusion of the SMS1 N terminus to the GCS C terminus via linkers of different lengths increased SM synthesis and decreased GlcCer synthesis in vivo. These results suggest that formation of the SMS1-GCS heteromeric complex increases SM synthesis and decreases GlcCer synthesis. Importantly, this regulation of relative Cer levels by the SMS1-GCS complex was confirmed by CRISPR/Cas9-mediated knockout of SMS1 or GCS combined with pharmacological inhibition of Cer transport protein in HEK293T cells. Our findings suggest that complex formation between SMS1 and GCS is part of a critical mechanism controlling the metabolic fate of Cer in the Golgi.