眼外肌神经肌肉接头的分子组织：与骨骼肌原型的部分保守及差异

Molecular organization of the extraocular muscle neuromuscular junction: partial conservation of and divergence from the skeletal muscle prototype.

作者信息

Khanna Sangeeta, Richmonds Chelliah R, Kaminski Henry J, Porter John D

机构信息

Department of Ophthalmology, Case Western Reserve University and The Research Institute of University Hospitals of Cleveland, Cleveland, Ohio 44106-5068, USA.

出版信息

Invest Ophthalmol Vis Sci. 2003 May;44(5):1918-26. doi: 10.1167/iovs.02-0890.

DOI:10.1167/iovs.02-0890

PMID:12714624

Abstract

PURPOSE

The phenotypically novel extraocular muscles (EOMs) exhibit fundamental differences in innervation and neuromuscular junction (NMJ) morphology from other skeletal muscles. In the current study, the morphology and molecular organization of NMJs of EOM singly innervated (SIF) and multiply innervated (MIF) fiber types were evaluated and the distribution of molecules involved in formation and maintenance of NMJs were specifically characterized.

METHODS

Adult mouse EOM NMJ organization was examined by immunofluorescence and confocal microscopy. Differential cellular localization of components of two established synaptic signaling pathways, (1) neuregulin and erbB receptors 2, 3, and 4 and (2) agrin, MuSK, and rapsyn and select NMJ-associated structural proteins were studied for EOM SIF and MIF populations. Endplate topography and structure were also studied, using both confocal microscopy and transmission electron microscopy, with NMJ morphologic organization correlated with specific EOM fiber types.

RESULTS

Confocal fluorescence microscopy demonstrated that, for NMJs of both EOM SIFs and MIFs, components of neuregulin and agrin pathways and the major components of the junctional dystrophin-glycoprotein complex (DGC) colocalized with acetylcholine receptor (AChR) aggregates. However, EOM exhibited novel fiber-type-specific extrasynaptic localization of two key DGC signaling-related molecules: alpha-dystrobrevin 1 (global MIFs) and syntrophin beta1 (global MIFs and orbital MIFs and SIFs).

CONCLUSIONS

The data establish that the molecular organization of EOM SIF and MIF NMJs includes the same signaling and structural molecules previously characterized for other skeletal muscles. By contrast, divergence in other aspects of the synaptic and nonsynaptic sarcolemmal organization of EOM fiber types may underlie the unique responses of these muscles in a variety of neuromuscular disorders.

摘要

目的

表型上独特的眼外肌（EOMs）在神经支配和神经肌肉接头（NMJ）形态上与其他骨骼肌存在根本差异。在本研究中，评估了单神经支配（SIF）和多神经支配（MIF）纤维类型的眼外肌神经肌肉接头的形态和分子组织，并对参与神经肌肉接头形成和维持的分子分布进行了具体表征。

方法

通过免疫荧光和共聚焦显微镜检查成年小鼠眼外肌神经肌肉接头组织。研究了两种已确立的突触信号通路的成分在细胞定位上的差异，（1）神经调节蛋白和erbB受体2、3和4，以及（2）聚集蛋白、肌肉特异性激酶（MuSK）和rapsyn，以及选择的与神经肌肉接头相关的结构蛋白在眼外肌SIF和MIF群体中的情况。还使用共聚焦显微镜和透射电子显微镜研究了终板的地形和结构，神经肌肉接头的形态组织与特定的眼外肌纤维类型相关。

结果

共聚焦荧光显微镜显示，对于眼外肌SIF和MIF的神经肌肉接头，神经调节蛋白和聚集蛋白通路的成分以及连接性肌营养不良蛋白 - 糖蛋白复合物（DGC）的主要成分与乙酰胆碱受体（AChR）聚集体共定位。然而，眼外肌在两种关键的与DGC信号相关分子上表现出新型的纤维类型特异性突触外定位：α - 肌营养不良蛋白短链1（整体MIFs）和肌养蛋白β1（整体MIFs以及眼眶MIFs和SIFs）。