Defining the importance of phosphatidylserine synthase 2 in mice
Defining the importance of phosphatidylserine synthase 2 in mice
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DOI：
10.1074/jbc.m207734200
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发表时间：
2002-12-06
影响因子：
4.8
通讯作者：
Young, SG
中科院分区：
文献类型：
--
作者：
Bergo, MO;Gavino, BJ;Young, SG
磷脂酰丝氨酸合酶 1 (Pss1) 和磷脂酰丝氨酸合酶 2 (Pss2) 通过将丝氨酸交换为其他磷脂的头基来产生磷脂酰丝氨酸。 Pss1 和 Pss2 结构相似（类似于 32% 氨基酸同一性），但其底物特异性不同，Pss1 使用磷脂酰胆碱进行丝氨酸交换反应，而 Pss2 使用磷脂酰乙醇胺。目前尚不清楚 Pss1 和 Pss2 是否都是哺乳动物生长和发育所必需的，也没有关于这两种酶对不同组织中丝氨酸交换活动的相对贡献的数据。为了解决这些问题并定义 Pss2 的细胞类型特异性表达，我们生成了 Pss2 缺陷型小鼠，其中 Pss2 调控序列表达了 β-半乳糖苷酶标记。对 Pss2 缺陷小鼠的组织学研究显示，睾丸支持细胞中 β-半乳糖苷酶的表达水平非常高，棕色脂肪、神经元和子宫肌层中的表达水平也很高。 Pss2缺陷小鼠的睾丸提取物催化丝氨酸交换的能力降低了95%以上；在大脑和肝脏中发现了类似 90% 的减少。然而，我们发现这些组织中的磷脂含量没有任何扰动。根据 Northern 印迹判断，Pss1 的表达在 Pss2 缺陷的细胞和组织中没有上调。 Pss2缺陷小鼠的睾丸重量减少，并且一些雄性小鼠不育。我们得出的结论是，Pss2 负责体外测定中的大部分丝氨酸交换活性，但这种酶的缺乏不会导致磷脂含量的扰动或严重的发育异常。
Phosphatidylserine synthase 1 (Pss1) and phosphatidylserine synthase 2 (Pss2) produce phosphatidylserine by exchanging serine for the head groups of other phospholipids. Pss1 and Pss2 are structurally similar (similar to32% amino acid identity) but differ in their substrate specificities, with Pss1 using phosphatidylcholine for the serine exchange reaction and Pss2 using phosphatidylethanolamine. Whether Pss1 and Pss2 are both required for mammalian growth and development is not known, and no data exist on the relative contributions of the two enzymes to serine exchange activities in different tissues. To address those issues and also to define the cell type-specific expression of Pss2, we generated Pss2-deficient mice in which a beta-galactosidase marker is expressed from Pss2 regulatory sequences. Histologic studies of Pss2-deficient mice revealed very high levels of beta-galactosidase expression in Sertoli cells of the testis and high levels of expression in brown fat, neurons, and myometrium. The ability of testis extracts from Pss2-deficient mice to catalyze serine exchange was reduced by more than 95%; reductions of similar to90% were noted in the brain and liver. However, we found no perturbations in the phospholipid content of any of these tissues. As judged by Northern blots, the expression of Pss1 was not upregulated in Pss2-deficient cells and tissues. Testis weight was reduced in Pss2-deficient mice, and some of the male mice were infertile. We conclude that Pss2 is responsible for the majority of serine exchange activity in in vitro assays, but a deficiency in this enzyme does not cause perturbations in phospholipid content or severe developmental abnormalities.