Cloning and characterization of the mammalian brain-specific, Mg2+-dependent neutral sphingomyelinase
Cloning and characterization of the mammalian brain-specific, Mg2+-dependent neutral sphingomyelinase
复制标题
DOI：
10.1073/pnas.97.11.5895
复制
发表时间：
2000-05-23
影响因子：
11.1
通讯作者：
Stoffel, W
中科院分区：
文献类型：
--
作者：
Hofmann, K;Tomiuk, S;Stoffel, W
鞘磷脂酶降解鞘磷脂被认为是第二信使神经酰胺的主要来源，由于缺乏中性鞘磷脂酶（nSMases）的分子数据，对各种酸性和中性鞘磷脂酶在神经酰胺信号池中作用的研究受到阻碍。然而，其无处不在的表达模式与之前的研究结果相反，即鞘磷脂酶活性主要存在于脑组织中。通过使用一种改进的数据库搜索方法，结合系统发育分析，我们确定了第二个哺乳动物nSMase（nSMase2）的主要表达在大脑中。nSMase2的鞘磷脂酶活性具有中性pH最适值，依赖于Mg2+离子，并被不饱和脂肪酸和磷脂酰丝氨酸激活。免疫荧光显示神经元特异性点状核周染色，其与许多细胞系中的高尔基体标记物共定位。nSM酶2与cca 1（一种参与3Y1成纤维细胞接触抑制的大鼠蛋白）的可能同一性表明该酶在细胞周期停滞中的作用。两种哺乳动物nSM酶都是Mg 2+依赖性磷酸水解酶超家族的成员，其也包含核酸酶，肌醇磷酸酶和细菌毒素。
The enzymatic breakdown of sphingomyelin by sphingomyelinases is considered the major source of the second messenger ceramide, Studies on the contribution of the Various described acidic and neutral sphingomyelinases to the signaling pool of ceramide have been hampered by the lack of molecular data on the neutral sphingomyelinases (nSMases), We recently identified a mammalian nSMase, an integral membrane protein with remote similarity to bacterial sphingomyelinases. However, its ubiquitous expression pattern is in contrast to previous findings that sphingomyelinase activity is found mainly in brain tissues. By using an improved database search method, combined with phylogenetic analysis, we identified a second mammalian nSMase (nSMase2) with predominant expression in the brain. The sphingomyelinase activity of nSMase2 has a neutral pH optimum, depends on Mg2+ ions, and is activated by unsaturated fatty acids and phosphatidylserine. Immunofluorescence reveals a neuron-specific punctate perinuclear staining, which colocalizes with a Golgi marker in a number of cell lines, The likely identity of nSMase2 with cca1, a rat protein involved in contact inhibition of 3Y1 fibroblasts, suggests a role for this enzyme in cell cycle arrest, Both mammalian nSMases are members of a superfamily of Mg2+-dependent phosphohydrolases, which also contains nucleases, inositol phosphatases, and bacterial toxins.