Modulation of Amyloid Precursor Protein Cleavage by Cellular Sphingolipids*
Modulation of Amyloid Precursor Protein Cleavage by Cellular Sphingolipids*
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DOI：
10.1074/jbc.m309832200
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发表时间：
2004-03
影响因子：
4.8
通讯作者：
N. Sawamura;Mihee Ko;Wenxin Yu;K. Zou;K. Hanada;Toshiharu Suzuki;J. Gong;K. Yanagisawa;M. Michikawa
中科院分区：
文献类型：
--
作者：
N. Sawamura;Mihee Ko;Wenxin Yu;K. Zou;K. Hanada;Toshiharu Suzuki;J. Gong;K. Yanagisawa;M. Michikawa
脂筏及其成分胆固醇调节β-淀粉样蛋白前体蛋白（APP）的加工。然而，鞘脂（脂筏的另一个主要成分）在APP加工中的作用仍未确定。本文报道了丝氨酸棕榈酰基转移酶特异性抑制剂处理鞘脂缺乏对中国仓鼠卵巢细胞APP加工的影响，丝氨酸棕榈酰基转移酶LCB1亚基缺陷突变株LY-B。丝氨酸棕榈酰基转移酶是催化鞘脂生物合成的第一步。我们发现，在鞘脂缺乏的细胞中，可溶性APPα (sAPPα)的分泌和α-位点c端裂解片段的产生显著增加，而β-裂解活性保持不变，ϵ-cleavage活性降低，但APP总水平不变。鞘脂缺乏细胞中淀粉样β-蛋白42的分泌增加，而淀粉样β-蛋白40的分泌则没有增加。所有这些改变在鞘脂缺乏的细胞中通过添加外源性鞘氨醇和在LY-B细胞中通过转染cLCB1而恢复。鞘脂缺乏增加了MAPK/ERK活性，而MAPK激酶特异性抑制剂PD98059恢复了sAPPα水平，表明鞘脂缺乏通过激活MAPK/ERK途径增强了sAPPα的分泌。这些结果提示，不仅细胞内胆固醇水平，鞘脂水平也可能通过调节APP的裂解参与阿尔茨海默病的病理过程。
Lipid rafts and their component, cholesterol, modulate the processing of β-amyloid precursor protein (APP). However, the role of sphingolipids, another major component of lipid rafts, in APP processing remains undetermined. Here we report the effect of sphingolipid deficiency on APP processing in Chinese hamster ovary cells treated with a specific inhibitor of serine palmitoyltransferase, which catalyzes the first step of sphingolipid biosynthesis, and in a mutant LY-B strain defective in the LCB1 subunit of serine palmitoyltransferase. We found that in sphingolipid-deficient cells, the secretion of soluble APPα (sAPPα) and the generation of C-terminal fragment cleaved at α-site dramatically increased, whereas β-cleavage activity remained unchanged, and the ϵ-cleavage activity decreased without alteration of the total APP level. The secretion of amyloid β-protein 42 increased in sphingolipid-deficient cells, whereas that of amyloid β-protein 40 did not. All of these alterations were restored in sphingolipid-deficient cells by adding exogenous sphingosine and in LY-B cells by transfection with cLCB1. Sphingolipid deficiency increased MAPK/ERK activity and a specific inhibitor of MAPK kinase, PD98059, restored sAPPα level, indicating that sphingolipid deficiency enhances sAPPα secretion via activation of MAPK/ERK pathway. These results suggest that not only the cellular level of cholesterol but also that of sphingolipids may be involved in the pathological process of Alzheimer's disease by modulating APP cleavage.