R-spondin 2 promotes acetylcholine receptor clustering at the neuromuscular junction via Lgr5.
R-spondin 2 promotes acetylcholine receptor clustering at the neuromuscular junction via Lgr5.
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DOI：
10.1038/srep28512
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发表时间：
2016-06-22
影响因子：
4.6
通讯作者：
Ohno K
中科院分区：
文献类型：
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作者：
Nakashima H;Ohkawara B;Ishigaki S;Fukudome T;Ito K;Tsushima M;Konishi H;Okuno T;Yoshimura T;Ito M;Masuda A;Sobue G;Kiyama H;Ishiguro N;Ohno K
在神经肌肉接头（NMJ）处，乙酰胆碱受体（AChR）聚集由脊髓运动神经元（SMN）衍生的聚集蛋白及其在肌肉上的受体、低密度脂蛋白受体相关蛋白4（LRP 4）和肌肉特异性受体酪氨酸激酶（MuSK）介导。此外，AChR聚集是由Wnt途径的组分介导的。SMNs的激光捕获显微切割揭示了分泌的Wnt信号传导激活剂R-spondin 2（Rspo2）在SMNs中高度表达。我们发现Rspo2在NMJ富集，并且Rspo2诱导MuSK磷酸化和AChR聚集。Rspo2需要Wnt配体，但不是聚集蛋白，促进AChR集群在培养的肌管。富含亮氨酸重复的G蛋白偶联受体5（Lgr5），一种Rspo2受体，也在NMJ积累，并通过LRP 4与MuSK相关。Lgr5是Rspo2介导的AChR在肌管中聚集所必需的。在Rspo2基因敲除小鼠中，NMJ处AChR的数量和密度降低。Rspo2基因敲除的隔膜具有改变的超微结构，具有加宽的突触裂隙和稀疏的突触小泡。在Rspo2基因敲除小鼠中，微小终板电流的频率显著降低。综上所述，我们证明，Rspo2和它的受体Lgr5是Wnt依赖和聚集蛋白的非依赖性调节AChR集群在NMJ。
At the neuromuscular junction (NMJ), acetylcholine receptor (AChR) clustering is mediated by spinal motor neuron (SMN)-derived agrin and its receptors on the muscle, the low-density lipoprotein receptor-related protein 4 (LRP4) and muscle-specific receptor tyrosine kinase (MuSK). Additionally, AChR clustering is mediated by the components of the Wnt pathway. Laser capture microdissection of SMNs revealed that a secreted activator of Wnt signaling, R-spondin 2 (Rspo2), is highly expressed in SMNs. We found that Rspo2 is enriched at the NMJ, and that Rspo2 induces MuSK phosphorylation and AChR clustering. Rspo2 requires Wnt ligands, but not agrin, for promoting AChR clustering in cultured myotubes. Leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5), an Rspo2 receptor, is also accumulated at the NMJ, and is associated with MuSK via LRP4. Lgr5 is required for Rspo2-mediated AChR clustering in myotubes. In Rspo2-knockout mice, the number and density of AChRs at the NMJ are reduced. The Rspo2-knockout diaphragm has an altered ultrastructure with widened synaptic clefts and sparse synaptic vesicles. Frequency of miniature endplate currents is markedly reduced in Rspo2-knockout mice. To conclude, we demonstrate that Rspo2 and its receptor Lgr5 are Wnt-dependent and agrin-independent regulators of AChR clustering at the NMJ.