Rapsyn clusters neuronal acetylcholine receptors but is inessential for formation of an interneuronal cholinergic synapse.

Published

Journal Article

Nicotinic acetylcholine receptors (AChRs) are clustered at high density in the postsynaptic membranes of skeletal neuromuscular junctions and cholinergic interneuronal synapses. A cytoplasmic protein, rapsyn, is essential for AChR clustering in muscle. Here, we asked whether rapsyn mediates neuronal AChR clustering at cholinergic synapses in a mammalian sympathetic ganglion, the superior cervical ganglion (SCG). Several observations supported this possibility: (1) AChR clusters containing the alpha3-5 and beta2 subunits, homologs of the muscle AChR subunits, are present at SCG synapses; (2) rapsyn RNA is readily detectable in the SCG; and (3) expression of recombinant rapsyn in heterologous cells induces aggregation of coexpressed neuronal AChR subunits. However, rapsyn protein was undetectable at ganglionic synaptic sites. Moreover, aggregates of neuronal AChRs induced in heterologous cells by full-length rapsyn remained intracellular, whereas rapsyn-induced clusters of muscle AChRs reached the cell surface. Additional studies revealed a second rapsyn RNA species in SCG generated by alternative splicing and competent to encode a novel short rapsyn isoform. However, this isoform clustered neither neuronal nor muscle AChRs in heterologous cells. Most telling, the number, size, and density of AChR clusters in SCG did not differ significantly between neonatal mice bearing a targeted mutation of the rapsyn gene and littermate controls. Thus, rapsyn is dispensable for clustering of ganglionic neuronal nicotinic AChRs.

Full Text

Cited Authors

  • Feng, G; Steinbach, JH; Sanes, JR

Published Date

  • June 1998

Published In

Volume / Issue

  • 18 / 11

Start / End Page

  • 4166 - 4176

PubMed ID

  • 9592096

Pubmed Central ID

  • 9592096

Electronic International Standard Serial Number (EISSN)

  • 1529-2401

International Standard Serial Number (ISSN)

  • 0270-6474

Digital Object Identifier (DOI)

  • 10.1523/JNEUROSCI.18-11-04166.1998

Language

  • eng