Recruitment of a Nicotinic Acetylcholine Receptor Mutant Lacking Cytoplasmic Tyrosine Residues in Its β Subunit into Agrin-Induced Aggregates

• Published in: Molecular and cellular neuroscience 1998-08, Vol.11 (5-6), p.324-333
• Main Authors: Meyer, Guido, Wallace, Bruce G.
• Format: Article
• Language: English
• Subjects: Agrin - physiology; Animals; Antibodies, Monoclonal; Chick Embryo; Cytoplasm; Gene Expression - physiology; Muscle Fibers, Skeletal - chemistry; Muscle Fibers, Skeletal - enzymology; Mutagenesis, Site-Directed - physiology; Phosphorylation; Receptor Protein-Tyrosine Kinases - genetics; Receptor Protein-Tyrosine Kinases - metabolism; Receptors, Cholinergic; Receptors, Nicotinic - chemistry; Receptors, Nicotinic - genetics; Receptors, Nicotinic - immunology; Species Specificity; Transfection; Tyrosine - metabolism
• ISSN: 1044-7431; 1095-9327
• DOI: 10.1006/mcne.1998.0689

During synaptogenesis at the vertebrate skeletal neuromuscular junction, acetylcholine receptors (AChRs) form high-density aggregates opposite the presynaptic terminal in response to nerve-derived agrin. Agrin has been shown to stimulate tyrosine phosphorylation of a muscle-specific receptor tyrosine kinase MuSK and of the AChR β subunit, and tyrosine kinase inhibitors and a tyrosine kinase-deficient mutant of MuSK prevent AChR aggregation. To evaluate the role of tyrosine phosphorylation of the AChR β subunit in receptor aggregation, we replaced all three putative cytoplasmic tyrosine residues of the AChR β subunit with phenylalanine residues and expressed the mutant receptors in cultured myotubes. Upon agrin treatment, transfected myotubes formed AChR aggregates that contained receptors with mutant β subunits. Thus, AChRs can be recruited into agrin-induced specializations by protein–protein interactions that do not depend on tyrosine phosphorylation of the AChR β subunit.