A protein homologous to the Torpedo postsynaptic 58K protein is present at the myotendinous junction.
A protein homologous to the Torpedo postsynaptic 58K protein is present at the myotendinous junction.
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DOI：
10.1083/jcb.110.6.2061
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发表时间：
1990-06
期刊：
影响因子：
--
通讯作者：
Peng HB
中科院分区：
文献类型：
--
作者：
Chen Q;Sealock R;Peng HB
58 K蛋白是电鳐电器官富含乙酰胆碱受体（AChR）的突触后膜上富集的一种外周膜蛋白。由于它与乙酰胆碱受体共存于电细胞和骨骼肌的突触后膜，因此被认为参与了乙酰胆碱受体簇的形成和维持。用抗电鳐电器官58 K蛋白的单克隆抗体对爪蟾肌节肌肉进行SDS-PAGE分析，发现一条表观分子量为48 kD的单一蛋白带。用该抗体，用免疫荧光技术检测该蛋白在肌节肌纤维中的分布。我们发现，48 K蛋白集中在这些肌纤维的肌腱接头（MTJs）。MTJ还富含talin和黏着斑蛋白。通过用针对talin和48 K蛋白的抗体双标记肌纤维，发现这两种蛋白质共定位于MTJ的膜内陷处。在培养的肌节肌细胞中，48 K蛋白和talin也共定位于膜-肌原纤维相互作用的位点。然而，48 K蛋白在非肌细胞中的粘着斑部位没有发现，而非肌细胞中的粘着斑部位富含塔林。这些数据表明，48 K蛋白是专门参与在MTJ的肌原纤维肌动蛋白丝与质膜的相互作用。除了MTJ定位，48 K蛋白也存在于体内和体外的AChR簇。因此，这种蛋白质由MTJ和神经肌肉接头共享。
The 58K protein is a peripheral membrane protein enriched in the acetylcholine receptor (AChR)-rich postsynaptic membrane of Torpedo electric organ. Because of its coexistence with AChRs in the postsynaptic membrane in both electrocytes and skeletal muscle, it is thought to be involved in the formation and maintenance of AChR clusters. Using an mAb against the 58K protein of Torpedo electric organ, we have identified a single protein band in SDS-PAGE analysis of Xenopus myotomal muscle with an apparent molecular mass of 48 kD. With this antibody, the distribution of this protein was examined in the myotomal muscle fibers with immunofluorescence techniques. We found that the 48K protein is concentrated at the myotendinous junctions (MTJs) of these muscle fibers. The MTJ is also enriched in talin and vinculin. By double labeling muscle fibers with antibodies against talin and the 48K protein, these two proteins were found to colocalize at the membrane invaginations of the MTJ. In cultured myotomal muscle cells, the 48K protein and talin are also colocalized at sites of membrane-myofibril interaction. The 48K protein is, however, not found at focal adhesion sites in nonmuscle cells, which are enriched in talin. These data suggest that the 48K protein is specifically involved in the interaction of myofibrillar actin filaments with the plasma membrane at the MTJ. In addition to the MTJ localization, 48K protein is also present at AChR clusters both in vivo and in vitro. Thus, this protein is shared by both the MTJ and the neuromuscular junction.