Regulated Secretion of Acid Sphingomyelinase IMPLICATIONS FOR SELECTIVITY OF CERAMIDE FORMATION
Regulated Secretion of Acid Sphingomyelinase IMPLICATIONS FOR SELECTIVITY OF CERAMIDE FORMATION
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DOI：
10.1074/jbc.m110.125609
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发表时间：
2010-11-12
影响因子：
4.8
通讯作者：
Hannun, Yusuf A.
中科院分区：
文献类型：
--
作者：
Jenkins, Russell W.;Canals, Daniel;Hannun, Yusuf A.
酸性鞘磷脂酶（aSMase）基因通过共同蛋白质前体的差异运输产生两种不同的酶，溶酶体鞘磷脂酶（L-SMase）和分泌型鞘磷脂酶（S-SMase）。然而，S-SMase的调节和它的作用在马槟榔碱诱导的神经酰胺形成仍然不清楚。为了确定S-SMase在细胞鞘脂代谢中的作用，用炎性细胞因子处理用V5-aSMase（WT）稳定转染的MCF 7乳腺癌细胞。白细胞介素-1 β和肿瘤坏死因子-α诱导S-SMase分泌和活性的时间和剂量依赖性增加，与细胞C-16-神经酰胺的选择性升高一致。为了确定S-SMase的作用，我们利用了aSMase的突变体（S508 A），该突变体显示保留L-SMase活性，但在分泌方面有缺陷。相对于载体对照MCF 7，表达V5-aSMaseWT的MCF 7表现出增加的S-SMase和L-SMase活性，以及升高的特定长链和极长链神经酰胺种类的细胞水平。有趣的是，在V5-aSM酶（S508 A）MCF 7中仅某些非常长链的神经酰胺的水平升高是明显的。S508 A突变体的分泌在对IL-1 β的反应中也是有缺陷的，C-16-神经酰胺的调节产生也是如此。综上所述，这些数据支持Ser（508）在调节S-SMase分泌中的关键作用，并且它们表明S-SMase和L-SMase的不同代谢作用。
The acid sphingomyelinase (aSMase) gene gives rise to two distinct enzymes, lysosomal sphingomyelinase (L-SMase) and secretory sphingomyelinase (S-SMase), via differential trafficking of a common protein precursor. However, the regulation of S-SMase and its role in cytokine-induced ceramide formation remain ill defined. To determine the role of S-SMase in cellular sphingolipid metabolism, MCF7 breast carcinoma cells stably transfected with V5-aSMase(WT) were treated with inflammatory cytokines. Interleukin-1 beta and tumor necrosis factor-alpha induced a time-and dose-dependent increase in S-SMase secretion and activity, coincident with selective elevations in cellular C-16-ceramide. To establish a role for S-SMase, we utilized a mutant of aSMase (S508A) that is shown to retain L-SMase activity, but is defective in secretion. MCF7 expressing V5-aSMaseWT exhibited increased S-SMase and L-SMase activity, as well as elevated cellular levels of specific long-chain and very long-chain ceramide species relative to vector control MCF7. Interestingly, elevated levels of only certain very long-chain ceramides were evident in V5-aSMase(S508A) MCF7. Secretion of the S508A mutant was also defective in response to IL-1 beta, as was the regulated generation of C-16-ceramide. Taken together, these data support a crucial role for Ser(508) in the regulation of S-SMase secretion, and they suggest distinct metabolic roles for S-SMase and L-SMase.