Rapid synthesis of acetylcholine receptors at neuromuscular junctions. (Reannouncement with new availability information)
The rate of acetylcholine receptor (AChR) degradation in mature, innervated mammalian neuromuscular junctions has recently been shown to be biphasic; up to 20% are rapidly turned over whereas the remainder are lost more slowly. In order to maintain normal junctional receptor density, synthesis and insertion of AChRs should presumably be sufficiently rapid to replace both the RTOs and the stable receptors. The authors have tested this prediction by blocking pre-existing AChRs in the mouse sternomastoid muscle with alpha bungarotoxin and monitoring the subsequent appearance of new junctional AChRs at intervals of 3 h to 20 days by labelling them. The results show that new receptors were initially inserted rapidly. The rate of increase of new binding sites gradually slowed down during the remainder of the time period studied. Control observations excluded possible artifacts of the experimental procedure including incomplete blockade of AChRs, dissociation of toxin receptor complexes, or experimentally induced alteration of receptor synthesis. The present demonstration of rapid synthesis and incorporation of AChRs at innervated neuromuscular junctions provides support for the concept of a subpopulation of rapidly turned over AChRs. The RTOs may serve as precursors for the large population of stable receptors and have an important role in the metabolism of the neuromuscular synapse.
- Research Organization:
- Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Neurology
- OSTI ID:
- 117862
- Report Number(s):
- AD-A-246093/9/XAB; CNN: Contract DAMD17-85-C-5069; TRN: 52750493
- Resource Relation:
- Other Information: PBD: 1988
- Country of Publication:
- United States
- Language:
- English
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