Martin P T, Ettinger A J, Sanes J R
Department of Anatomy and Neurobiology, Washington University School of Medicine, St.Louis, MO 63110, USA.
Science. 1995 Jul 21;269(5222):413-6. doi: 10.1126/science.7618109.
The basal lamina that ensheaths skeletal muscle fibers traverses the synaptic cleft at the neuromuscular junction. Synaptic and extrasynaptic portions of the basal lamina contain different laminin beta chains: beta 2 (or s) at synapses and beta 1 (or B1) extrasynaptically. Laminin beta 2 is also confined to synapselike patches on myotube surfaces in vitro, whereas beta 1 is present throughout the extracellular matrix. This differential localization of laminin beta chains was analyzed by expression of chimeric beta 1-beta 2 molecules in cultured mouse myotubes. A 16-amino acid carboxyl-terminal sequence in beta 2 was necessary for synaptic localization, and an amino-terminal domain in beta 1 promoted association with extracellular fibrils. The synaptic targeting sequence of beta 2 contains a site previously shown to be adhesive for motor neurons.
包裹骨骼肌纤维的基底层穿过神经肌肉接头处的突触间隙。基底层的突触和突触外部分含有不同的层粘连蛋白β链：突触处为β2（或s），突触外为β1（或B1）。层粘连蛋白β2在体外也局限于肌管表面的突触样斑块，而β1则存在于整个细胞外基质中。通过在培养的小鼠肌管中表达嵌合的β1-β2分子，分析了层粘连蛋白β链的这种差异定位。β2中一个16个氨基酸的羧基末端序列是突触定位所必需的，而β1中的一个氨基末端结构域促进了与细胞外纤维的结合。β2的突触靶向序列包含一个先前已证明对运动神经元有粘附作用的位点。
