Involvement of Acid β-Glucosidase 1 in the Salvage Pathway of Ceramide Formation
Involvement of Acid β-Glucosidase 1 in the Salvage Pathway of Ceramide Formation
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DOI：
10.1074/jbc.m802790200
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发表时间：
2009-05-08
影响因子：
4.8
通讯作者：
Hannun, Yusuf A.
中科院分区：
文献类型：
--
作者：
Kitatani, Kazuyuki;Sheldon, Kely;Hannun, Yusuf A.
蛋白激酶 C (PKC) 的激活促进神经酰胺形成的补救途径，并且酸性鞘磷脂酶部分涉及为该途径提供底物 (Zeidan, Y. H., 和 Hannun, Y. A. (2007) J. Biol. Chem. 282, 11549-11561)。在本研究中，我们检查了酸性 β-葡萄糖苷酶 1 (GBA1)（水解葡萄糖神经酰胺形成溶酶体神经酰胺）是否参与 PKC 调节的回收鞘氨醇形成神经酰胺。用强效 PKC 激活剂佛波醇 12-肉豆蔻酸酯 13-乙酸酯 (PMA) 处理 MCF-7 细胞后，葡萄糖神经酰胺水平下降。通过小干扰 RNA 沉默 GBA1 可显着减弱酸性葡萄糖脑苷脂酶活性，并使 PMA 诱导的神经酰胺形成减少 50%。沉默 GBA1 可阻止 PMA 诱导的葡萄糖神经酰胺降解和神经酰胺生物合成来源鞘氨醇的生成。相反，GBA1 的强制表达会增加神经酰胺水平。这些观察结果表明 GBA1 激活可以通过挽救途径产生 PMA 诱导的神经酰胺形成的来源（鞘氨醇）。接下来，确定了 PMA 的直接效应子 PKC δ 在神经酰胺形成中的作用。通过减弱 PKC δ 的表达，细胞无法触发 PMA 诱导的神经酰胺、鞘磷脂和葡萄糖神经酰胺水平的变化。因此，PKC δ 激活被认为可以刺激鞘磷脂和葡萄糖神经酰胺的降解，从而导致神经酰胺形成的补救途径。总的来说，GBA1 被认为是神经酰胺形成调节的新来源，而 PKC δ 是该途径的上游调节因子。
Activation of protein kinase C (PKC) promotes the salvage pathway of ceramide formation, and acid sphingomyelinase has been implicated, in part, in providing substrate for this pathway (Zeidan, Y. H., and Hannun, Y. A. (2007) J. Biol. Chem. 282, 11549-11561). In the present study, we examined whether acid beta-glucosidase 1 (GBA1), which hydrolyzes glucosylceramide to form lysosomal ceramide, was involved in PKC-regulated formation of ceramide from recycled sphingosine. Glucosylceramide levels declined after treatment of MCF-7 cells with a potent PKC activator, phorbol 12-myristate 13-acetate (PMA). Silencing GBA1 by small interfering RNAs significantly attenuated acid glucocerebrosidase activity and decreased PMA-induced formation of ceramide by 50%. Silencing GBA1 blocked PMA-induced degradation of glucosylceramide and generation of sphingosine, the source for ceramide biosynthesis. Reciprocally, forced expression of GBA1 increased ceramide levels. These observations indicate that GBA1 activation can generate the source (sphingosine) for PMA-induced formation of ceramide through the salvage pathway. Next, the role of PKC delta, a direct effector of PMA, in the formation of ceramide was determined. By attenuating expression of PKC delta, cells failed to trigger PMA-induced alterations in levels of ceramide, sphingomyelin, and glucosylceramide. Thus, PKC delta activation is suggested to stimulate the degradation of both sphingomyelin and glucosylceramide leading to the salvage pathway of ceramide formation. Collectively, GBA1 is identified as a novel source of regulated formation of ceramide, and PKC delta is an upstream regulator of this pathway.