Expression, Localization, and Biochemical Characterization of Nicotinamide Mononucleotide Adenylyltransferase 2
Expression, Localization, and Biochemical Characterization of Nicotinamide Mononucleotide Adenylyltransferase 2
复制标题
DOI：
10.1074/jbc.m110.178913
复制
发表时间：
2010-12-17
影响因子：
4.8
通讯作者：
Yu, Gang
中科院分区：
文献类型：
--
作者：
Mayer, Paul R.;Huang, Nian;Yu, Gang
烟酰胺单核苷酸(NMN)腺基转移酶2(Nmnat2)催化NMN和ATP合成NAD。Nmnat2转录本主要在大脑中表达；我们在此报告Nmnat2是一种在神经元中表达的低丰度蛋白。以往的研究表明，Nmnat2基因定位于高尔基体。由于Nmnat2不包含信号序列、脂结合结构域或跨膜结构域，我们研究了这种相互作用的性质。这些实验表明，Nmnat2在体外是棕榈酰化的，这种修饰是膜结合所必需的。令人惊讶的是，外源性Nmnat2对神经元是有毒的，这表明蛋白质水平必须受到严格调控。为了分析Nmnat2在神经元中的定位(以前的实验依赖于HeLa细胞中的外源表达)，对小鼠大脑进行了分离，结果表明Nmnat2富含在包括突触终末在内的许多膜间隔中。在HeLa细胞中，除了高尔基体外，Nmnat2还定位于含有Rab7的晚期内小体。这些研究表明，Nmnat2是一种神经元蛋白，通过棕榈酰化作用外周附着在膜上，并提示Nmnat2通过内体途径运输到突触终末。
Nicotinamide mononucleotide (NMN) adenylyltransferase 2 (Nmnat2) catalyzes the synthesis of NAD from NMN and ATP. The Nmnat2 transcript is expressed predominately in the brain; we report here that Nmnat2 is a low abundance protein expressed in neurons. Previous studies indicate that Nmnat2 localizes to Golgi. As Nmnat2 is not predicted to contain a signal sequence, lipid-binding domain, or transmembrane domain, we investigated the nature of this interaction. These experiments reveal that Nmnat2 is palmitoylated in vitro, and this modification is required for membrane association. Surprisingly, exogenous Nmnat2 is toxic to neurons, indicating that protein levels must be tightly regulated. To analyze Nmnat2 localization in neurons (previous experiments relied on exogenous expression in HeLa cells), mouse brains were fractionated, showing that Nmnat2 is enriched in numerous membrane compartments including synaptic terminals. In HeLa cells, in addition to Golgi, Nmnat2 localizes to Rab7-containing late endosomes. These studies show that Nmnat2 is a neuronal protein peripherally attached to membranes via palmitoylation and suggest that Nmnat2 is transported to synaptic terminals via an endosomal pathway.