Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA.
Exp Cell Res. 2010 Jan 1;316(1):78-91. doi: 10.1016/j.yexcr.2009.09.027. Epub 2009 Oct 2.
The ceramide synthase (CerS) enzymes are key regulators of ceramide homeostasis. CerS1 is central to regulating C18 ceramide which has been shown to be important in cancer and the response to chemotherapeutic drugs. Previous work indicated that some drugs induced a novel and specific translocation of CerS1 from the endoplasmic reticulum to the Golgi apparatus. We now show that diverse stresses such as UV light, DTT, as well as drugs with different mechanisms of action induce CerS1 translocation. The stresses cause a specific cleavage of the CerS1 enzyme, and the cleavage is dependent on the action of the proteasome. Inhibition of proteasome function inhibits stress-induced CerS1 translocation, indicating that this proteolytic cleavage precedes the translocation. Modulation of protein kinase C activity shows that it plays a central role in regulating CerS1 translocation. Analysis of the C-terminus of the CerS1 protein shows that several KxKxx motifs are not involved in regulating stress induced translocation. The study suggests that diverse stresses initiate responses through different signaling pathways, which ultimately converge to regulate CerS1 localization. The data provide an increasingly detailed understanding of the regulation of this important enzyme in normal and stressed cells and support the idea that it is uniquely regulated with respect to the other CerS enzymes.
神经酰胺合酶(CerS)酶是神经酰胺动态平衡的关键调节因子。CerS1 是调节 C18 神经酰胺的核心,已被证明在癌症和化疗药物反应中很重要。先前的工作表明,一些药物诱导 CerS1 从内质网向高尔基体的新型和特异性易位。我们现在表明,多种应激如紫外线、DTT 以及具有不同作用机制的药物都会诱导 CerS1 易位。这些应激会导致 CerS1 酶的特异性切割,并且切割依赖于蛋白酶体的作用。蛋白酶体功能抑制剂抑制应激诱导的 CerS1 易位,表明这种蛋白水解切割先于易位。蛋白激酶 C 活性的调节表明其在调节 CerS1 易位中起着核心作用。对 CerS1 蛋白 C 端的分析表明,几个 KxKxx 基序不参与调节应激诱导的易位。该研究表明,多种应激通过不同的信号通路引发反应,最终汇聚调节 CerS1 定位。该数据提供了对正常和应激细胞中这种重要酶的调节的越来越详细的理解,并支持这样一种观点,即它相对于其他 CerS 酶具有独特的调节。