The mammalian 43-kD acetylcholine receptor-associated protein (RAPsyn) is expressed in some nonmuscle cells

Linda Musil, D. E. Frail, J. P. Merlie

Research output: Contribution to journalArticle

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Abstract

Torpedo electric organ and vertebrate neuromuscular junctions contain the receptor-associated protein of the synapse (RAPsyn) (previously referred to as the 43K protein), a nonactin, 43,000-M(r) peripheral membrane protein associated with the cytoplasmic face of postsynaptic membranes at areas of high nicotinic acetylcholine receptor (AChR) density. Although not directly demonstrated, several lines of evidence suggest that RAPsyn is involved in the synthesis and/or maintenance of such AChR clusters. Microscopic and biochemical studies had previously indicated that RAPsyn expression is restricted to differentiated, AChR-synthesizing cells. Our recent finding that RAPsyn is also produced in undifferentiated myocytes (Frail, D.E., L.S. Musil, A. Bonanno, and J.P. Merlie. 1989. Neuron. 2:1077-1086) led us to examine whether RAPsyn is synthesized in cell types that never express AChR (i.e., cells of other than skeletal muscle origin). Various primary and established rodent cell lines were metabolically labeled with [35S]methionine, and extracts were immunoprecipitated with a monospecific anti-RAPsyn serum. Analysis of these immunoprecipitates by SDS-PAGE revealed detectable RAPsyn synthesis in some (notably fibroblast and Leydig tumor cell lines and primary cardiac cells) but not all (hepatocyte- and lymphocyte-derived) cell types. These results were further substantiated by peptide mapping studies of RAPsyn immunoprecipitated from different cells and quantitation of RAPsyn-encoding mRNA levels in mouse tissues. RAPsyn synthesized in both muscle and nonmuscle cells was shown to be tightly associated with membranes. These findings demonstrate that RAPsyn is not specific to skeletal muscle-derived cells and imply that it may function in a capacity either in addition to or instead of AChR clustering.

Original languageEnglish (US)
Pages (from-to)1833-1840
Number of pages8
JournalJournal of Cell Biology
Volume108
Issue number5
StatePublished - 1989
Externally publishedYes

Fingerprint

Cholinergic Receptors
Synapses
Proteins
Muscle Cells
Skeletal Muscle
Electric Organ
Torpedo
Peptide Mapping
Membranes
Neuromuscular Junction
Nicotinic Receptors
Tumor Cell Line
Methionine
Cluster Analysis
Vertebrates
Blood Proteins
Polyacrylamide Gel Electrophoresis
Hepatocytes
Rodentia
Membrane Proteins

ASJC Scopus subject areas

  • Cell Biology

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The mammalian 43-kD acetylcholine receptor-associated protein (RAPsyn) is expressed in some nonmuscle cells. / Musil, Linda; Frail, D. E.; Merlie, J. P.

In: Journal of Cell Biology, Vol. 108, No. 5, 1989, p. 1833-1840.

Research output: Contribution to journalArticle

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