Phosphatidylserine synthase-1 and-2 are localized to mitochondria-associated membranes
Phosphatidylserine synthase-1 and-2 are localized to mitochondria-associated membranes
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DOI：
10.1074/jbc.m002865200
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发表时间：
2000-11-03
影响因子：
4.8
通讯作者：
Vance, JE
中科院分区：
文献类型：
--
作者：
Stone, SJ;Vance, JE
我们报道了哺乳动物细胞中参与磷脂酰丝氨酸生物合成的酶的亚细胞定位。几条证据表明，磷脂酰丝氨酸脱氢酶-1（PSS 1）高度富集于线粒体相关膜（MAM）中，并在很大程度上被排除在内质网（ER）之外。利用PSS 1的底物特异性，我们发现（i）MAM含有胆碱交换活性，而这种活性在ER的大部分中非常低，（ii）丝氨酸交换活性在MAM中比在ER中更大程度地被胆碱抑制，以及（iii）MAM使用磷脂酰胆碱和磷脂酰乙醇胺作为磷脂酰丝氨酸生物合成的底物，而ER仅利用磷脂酰乙醇胺。根据来自CHO-K1细胞和小鼠肝脏的蛋白质的免疫印迹，PSS 1定位于MAM，并且在稳定表达PSS 1的肝癌细胞中，该蛋白质高度富集于MAM。由于ER含有丝氨酸和乙醇胺交换活性，我们预测PSS 2将解释ER中的丝氨酸交换活性。出乎意料的是，使用免疫印迹实验，我们发现（i）CRO-Kl细胞的PSS 2仅存在于MAM中，并且（ii）PSS 2限于表达重组PSS 2的McArdle细胞的MAM。这些数据留下开放的问题，哪种酶赋予PSS活性的ER，并建议PSS的第三种亚型可能位于ER。
We report the subcellular localization of enzymes involved in phosphatidylserine biosynthesis in mammalian cells, Several lines of evidence suggest that phosphatidylserine synthase-l (PSS1) is highly enriched in mitochondria-associated membranes (MAM) and is largely excluded from the bulk of the endoplasmic reticulum (ER). Taking advantage of the substrate specificity of PSS1, we showed that (i) MAM contain choline exchange activity, whereas this activity is very low in the bulk of the ER, (ii) serine exchange activity is inhibited by choline to a much greater extent in MAM than in ER, and (iii) MAM use phosphatidylcholine and phosphatidylethanolamine as substrates for phosphatidylserine biosynthesis, whereas the ER utilizes only phosphatidylethanolamine. According to immunoblotting of proteins from both CHO-K1 cells and murine liver, PSS1 is localized to MAM, and in hepatoma cells stably expressing PSS1 this protein is highly enriched in MAM. Since the ER contains serine and ethanolamine exchange activities, we had predicted that PSS2 would account for the serine exchange activity in the ER. Unexpectedly, using immunoblotting experiments, we found that (i) PSS2 of CRO-K1 cells is present only in MAM and (ii) PSS2 is restricted to MAM of McArdle cells expressing recombinant PSS2. These data leave open the question of which enzyme imparts PSS activity to the ER and suggest that a third isoform of PSS might be located in the ER.