Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195-78290, USA.
J Neurosci. 2010 Aug 18;30(33):11004-10. doi: 10.1523/JNEUROSCI.1930-10.2010.
At the neuromuscular junction (NMJ), the dystrophin protein complex provides a scaffold that functions to stabilize acetylcholine receptor (AChR) clusters. Syntrophin, a key component of that scaffold, is a multidomain adapter protein that links a variety of signaling proteins and ion channels to the dystrophin protein complex. Without syntrophin, utrophin and neuronal nitric oxide synthase mu (nNOSmu) fail to localize to the NMJ and the AChRs are distributed abnormally. Here we investigate the contribution of syntrophin domains to AChR distribution and to localization of utrophin and nNOSmu at the NMJ. Transgenic mice expressing alpha-syntrophin lacking portions of the first pleckstrin homology (PH) domain (DeltaPH1a or DeltaPH1b) or the entire PDZ domain (DeltaPDZ) were bred onto the alpha-syntrophin null background. As expected the DeltaPDZ transgene did not restore the NMJ localization of nNOS. The DeltaPH1a transgene did restore postsynaptic nNOS but surprisingly did not restore sarcolemmal nNOS (although sarcolemmal aquaporin-4 was restored). Mice lacking the alpha-syntrophin PDZ domain or either half of the PH1 domain were able to restore utrophin to the NMJ but did not correct the aberrant AChR distribution of the alpha-syntrophin knock-out mice. However, mice expressing both the transgenic DeltaPDZ and the transgenic DeltaPH1a constructs did restore normal AChR distribution, demonstrating that both domains are required but need not be confined within the same protein to function. We conclude that the PH1 and PDZ domains of alpha-syntrophin work in concert to facilitate the localization of AChRs and nNOS at the NMJ.
在神经肌肉接头（NMJ）处，dystrophin 蛋白复合物提供了一个支架，其功能是稳定乙酰胆碱受体（AChR）簇。作为该支架的关键组成部分，syntrophin 是一种多结构域衔接蛋白，它将各种信号蛋白和离子通道与 dystrophin 蛋白复合物连接起来。没有 syntrophin，utrophin 和神经元型一氧化氮合酶 mu（nNOSmu）就无法定位于 NMJ，AChR 也会异常分布。在这里，我们研究了 syntrophin 结构域对 AChR 分布以及 utrophin 和 nNOSmu 在 NMJ 处定位的贡献。表达缺失部分第一pleckstrin 同源（PH）结构域（DeltaPH1a 或 DeltaPH1b）或整个 PDZ 结构域（DeltaPDZ）的 alpha-syntrophin 的转基因小鼠被繁殖到 alpha-syntrophin 缺失背景下。正如预期的那样，DeltaPDZ 转基因没有恢复 NMJ 处的 nNOS 定位。DeltaPH1a 转基因确实恢复了突触后 nNOS，但令人惊讶的是，它没有恢复肌膜 nNOS（尽管恢复了肌膜水通道蛋白-4）。缺乏 alpha-syntrophin PDZ 结构域或 PH1 结构域一半的小鼠能够将 utrophin 恢复到 NMJ，但不能纠正 alpha-syntrophin 敲除小鼠的异常 AChR 分布。然而，表达转基因 DeltaPDZ 和转基因 DeltaPH1a 构建体的小鼠确实恢复了正常的 AChR 分布，这表明两个结构域都需要，但不需要在同一蛋白内发挥作用。我们得出结论，alpha-syntrophin 的 PH1 和 PDZ 结构域协同作用，促进 AChR 和 nNOS 在 NMJ 处的定位。
