Department of Environmental & Health Chemistry, Chung-Ang University, Dongjak-Ku, Seoul, South Korea.
Cell Signal. 2010 May;22(5):865-70. doi: 10.1016/j.cellsig.2010.01.012. Epub 2010 Jan 21.
Ceramide serves as a second messenger produced from sphingomyelin by the activation of sphingomyelinase (SMase). Here, we suggest that neutral SMase 2 (nSMase2) may regulate dopamine (DA) uptake. nSMase2 siRNA-transfected PC12 cells showed lower levels of nSMase activity and ceramide than scramble siRNA-transfected and control cells. Interestingly, transfection of nSMase2 siRNA or pretreatment with the nSMase2-specific inhibitor GW4869 resulted in decreased DA uptake. Reciprocally, exposure of PC12 cells to cell-permeable C(6)-ceramide induced a concentration-dependent increase in DA uptake. Removal of extracellular calcium by EGTA increased DA uptake in scramble-transfected and control cells, but not in nSMase2 siRNA-transfected or GW4869-pretreated cells. Moreover, siRNA-transfected cells showed higher levels of intracellular calcium than scramble cells, while C(6)-ceramide treatment resulted in decreased intracellular calcium compared to vehicle treatment alone. Taken together, these data suggest that nSMase2 may increase DA uptake through inducing ceramide production and thereby decreasing intracellular calcium levels.
神经酰胺作为第二信使，由鞘磷脂在神经鞘磷脂酶（SMase）的激活下产生。在这里，我们提出中性鞘磷脂酶 2（nSMase2）可能调节多巴胺（DA）摄取。与 scramble siRNA 转染和对照细胞相比，nSMase2 siRNA 转染的 PC12 细胞中的 nSMase 活性和神经酰胺水平较低。有趣的是，nSMase2 siRNA 的转染或 nSMase2 特异性抑制剂 GW4869 的预处理导致 DA 摄取减少。相反，PC12 细胞暴露于细胞通透性 C（6）-神经酰胺导致 DA 摄取呈浓度依赖性增加。用 EGTA 去除细胞外钙可增加 scramble 转染和对照细胞中的 DA 摄取，但不能增加 nSMase2 siRNA 转染或 GW4869 预处理细胞中的 DA 摄取。此外，siRNA 转染的细胞比 scramble 细胞表现出更高的细胞内钙水平，而 C（6）-神经酰胺处理导致细胞内钙水平相对于单独用载体处理降低。综上所述，这些数据表明 nSMase2 可能通过诱导神经酰胺产生并从而降低细胞内钙水平来增加 DA 摄取。
