Paumen M B, Ishida Y, Muramatsu M, Yamamoto M, Honjo T
Department of Medical Chemistry, Faculty of Medicine, Kyoto University, Yoshida, Sakyo-ku, 606 Kyoto, Japan.
J Biol Chem. 1997 Feb 7;272(6):3324-9. doi: 10.1074/jbc.272.6.3324.
To identify cell death-induced genes, we employed a subtractive hybridization approach and isolated a cDNA encoding a mouse homolog of carnitine palmitoyltransferase I (CPT I), an enzyme that resides at the outer mitochondrial membrane and facilitates passage of long-chain fatty acids into mitochondria for beta-oxidation. Induced expression of CPT I mRNA was observed upon programmed cell death in the murine hematopoietic cell lines LyD9 and WEHI-231. To elucidate the role of CPT I in programmed cell death, we examined the effects of long-chain fatty acids and found that the addition of palmitate or stearate to cultured cells led to activation of a death program with a morphology resembling that of apoptosis. Other naturally occurring fatty acids, including myristate and palmitoleate, had no effect. Since both palmitate and stearate are sphingolipid precursors, the effect of these fatty acids on sphingolipid metabolism was tested. Our results indicate that apoptosis induced by palmitate or stearate is correlated with de novo synthesis of ceramide. Inhibition of CPT I by etomoxir enhanced palmitate-induced cell death and led to a further increase in ceramide synthesis.
为了鉴定细胞死亡诱导基因，我们采用了消减杂交方法，分离出一个编码肉碱棕榈酰转移酶I（CPT I）小鼠同源物的cDNA，CPT I是一种位于线粒体外膜的酶，可促进长链脂肪酸进入线粒体进行β氧化。在小鼠造血细胞系LyD9和WEHI-231发生程序性细胞死亡时，观察到CPT I mRNA的诱导表达。为了阐明CPT I在程序性细胞死亡中的作用，我们检测了长链脂肪酸的作用，发现向培养细胞中添加棕榈酸或硬脂酸会导致一种形态类似于凋亡的死亡程序的激活。其他天然存在的脂肪酸，包括肉豆蔻酸和棕榈油酸，没有作用。由于棕榈酸和硬脂酸都是鞘脂前体，因此测试了这些脂肪酸对鞘脂代谢的影响。我们的结果表明，棕榈酸或硬脂酸诱导的凋亡与神经酰胺的从头合成相关。依托莫昔对CPT I的抑制增强了棕榈酸诱导的细胞死亡，并导致神经酰胺合成进一步增加。
