Rapid lateral diffusion of extrajunctional acetylcholine receptors in the developing muscle membrane of Xenopus tadpole
Rapid lateral diffusion of extrajunctional acetylcholine receptors in the developing muscle membrane of Xenopus tadpole
复制标题
非洲爪蟾蝌蚪发育中肌膜中交界外乙酰胆碱受体的快速横向扩散
DOI：
10.1523/jneurosci.03-01-00225.1983
复制
发表时间：
1983
影响因子：
--
通讯作者：
M. Poo
中科院分区：
文献类型：
--
作者：
S. H. Young;M. Poo
用局部失活技术研究了非洲爪哇蝌蚪肌层细胞膜上乙酰胆碱受体(ACh)的侧向扩散。通过轻轻去除尾部皮肤，将非洲爪哇蝌蚪的肌肉细胞表面暴露在外部溶液中。ACh受体的密度通过膜去极化来监测，以响应电泳法施加的ACh脉冲。一个脉冲的α-银环蛇毒素被压力喷射到暴露的纤维表面，导致ACh受体的快速局部失活。随着时间的推移，功能性ACh受体扩散到失活区，产生ACh反应的恢复。观察到的ACh敏感性的恢复是由于ACh受体从未暴露的纤维下表面扩散到失活区：(1)长期使用毒素后没有观察到恢复，(2)用使ACh受体交联和固定的刀豆蛋白A预处理阻止了恢复，(3)沿肌细胞轴的ACh反应图显示，这种恢复不能用沿纤维纵轴的扩散来解释；(4)用纤维半径衡量恢复率后的扩散系数落在一个较小的范围内(1.5~4.0×10~(-9)cm~2/s)，与ACh受体在纤维周长周围的扩散一致。这一发现支持由神经支配引起的ACh受体的定位是通过一种“扩散陷阱”机制实现的，即神经接触区域作为膜上受体快速扩散的陷阱。
We have studied the lateral diffusion of acetylcholine (ACh) receptors in the extrajunctional region of developing myotomal muscle cell membrane of Xenopus tadpoles by a technique of local inactivation. The myotomal muscle cell surfaces of Xenopus tadpoles were exposed to external solution by gently removing the skin of the tail. The density of ACh receptors was monitored by membrane depolarizations in response to iontophoretically applied pulses of ACh. A pulse of alpha- bungarotoxin was pressure ejected onto the exposed fiber surface, resulting in a rapid local inactivation of the ACh receptors. With time, the functional ACh receptors diffused into the region of inactivation, producing a recovery of ACh response. That the observed recovery of ACh sensitivity is due to diffusion of ACh receptors from the unexposed undersurface of the fiber to the inactivated region was evidenced by the following: (1) no recovery was observed following prolonged toxin application; (2) pretreatment of the muscle cells with concanavalin A, which cross-links and immobilizes ACh receptors, prevented recovery; (3) mapping of ACh response along the muscle cell axis showed that the recovery cannot be accounted for by diffusion along the longitudinal axis of the fiber; and (4) the diffusion coefficients observed after scaling the recovery rate with fiber radius fell within a small range (1.5 to 4.0 X 10(-9) cm2/sec), consistent with diffusion of ACh receptors around the fiber circumference. This finding of rapid lateral diffusion within developing tadpole myotomal muscle membrane supports the notion that the localization of ACh receptors induced by innervation could be achieved by a “diffusion- trap” mechanism where the nerve contact region serves as a trap for rapidly diffusing receptors in the membrane.