Wld S requires Nmnat1 enzymatic activity and N16-VCP interactions to suppress Wallerian degeneration.
Wld S requires Nmnat1 enzymatic activity and N16-VCP interactions to suppress Wallerian degeneration.
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DOI：
10.1083/jcb.200808042
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发表时间：
2009-02-23
期刊：
影响因子：
--
通讯作者：
Freeman MR
中科院分区：
文献类型：
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作者：
Avery MA;Sheehan AE;Kerr KS;Wang J;Freeman MR
慢沃勒变性(WldS)编码Ube4b/烟酰胺单核苷酸腺苷转移酶1(Nmnat1)融合蛋白，可有效抑制Weller变性，但WldS的作用机制仍存在争议。在这项研究中，我们利用果蝇研究了WldS介导的体内轴突保护作用。我们发现，Nmnat1可以保护切断的轴突免受自身破坏，但水平明显低于WldS，酶死亡版本的Nmnat1和WldS显示出严重的轴突保护功能。有趣的是，WldS的16个氨基酸的N末端结构域(称为N16)解释了WldS和Nmnat1在轴突保护活性上的差异，并且依赖N16的增强WldS的Nmnat1保护活性需要N16结合蛋白Valosin-Holding Protein(VCP)/TER94。因此，WldS介导的沃勒变性的抑制是由于VCP-N16相互作用和Nmnat1活性在体内收敛所致。令人惊讶的是，小鼠Nmnat3，一种定位于果蝇细胞细胞质的线粒体Nmnat酶，以与WldS难以区分的水平保护被切断的轴突。因此，核Nmnat活性似乎不是WldS样轴突保护所必需的。
Slow Wallerian degeneration (WldS) encodes a chimeric Ube4b/nicotinamide mononucleotide adenylyl transferase 1 (Nmnat1) fusion protein that potently suppresses Wallerian degeneration, but the mechanistic action of WldS remains controversial. In this study, we characterize WldS-mediated axon protection in vivo using Drosophila melanogaster. We show that Nmnat1 can protect severed axons from autodestruction but at levels significantly lower than WldS, and enzyme-dead versions of Nmnat1 and WldS exhibit severely reduced axon-protective function. Interestingly, a 16–amino acid N-terminal domain of WldS (termed N16) accounts for the differences in axon-sparing activity between WldS and Nmnat1, and N16-dependent enhancement of Nmnat1-protective activity in WldS requires the N16-binding protein valosin-containing protein (VCP)/TER94. Thus, WldS-mediated suppression of Wallerian degeneration results from VCP–N16 interactions and Nmnat1 activity converging in vivo. Surprisingly, mouse Nmnat3, a mitochondrial Nmnat enzyme that localizes to the cytoplasm in Drosophila cells, protects severed axons at levels indistinguishable from WldS. Thus, nuclear Nmnat activity does not appear to be essential for WldS-like axon protection.