M_r 42,000 ARIA: A Protein That May Regulate the Accumulation of Acetylcholine Receptors at Developing Chick Neuromuscular Junctions

Excerpt

At the neuromuscular junction (NMJ), as at other chemical synapses, the number and distribution of neurotransmitter receptors are critical factors determining the response to presynaptic stimulation. A cardinal event in the formation of the NMJ is the accumulation of acetylcholine receptors (AChRs) in the muscle membrane opposed to the nerve terminal. At the mature junction, receptors are packed in the postsynaptic membrane at a density in excess of 10,000μm2. The localization is striking in that more than 70÷ of the receptors are restricted to the endplate, a region that comprises less than 0.1÷ of the muscle-surface membrane. In this paper, we review our work directed at elucidating the structure, function, and biological role of a protein purified from chick brain on the basis of its ability to increase the rate of insertion of AChRs into the surface membrane of cultured chick myotubes. This protein, which we designate an ARIA for...