Nitric oxide synthase activity is required for postsynaptic differentiation of the embryonic neuromuscular junction.
Agrin, a synapse-organizing protein externalized by motor axons at the neuromuscular junction (NMJ), initiates a signaling cascade in muscle cells leading to aggregation of postsynaptic proteins, including acetylcholine receptors (AChRs). We examined whether nitric oxide synthase (NOS) activity is required for agrin-induced aggregation of postsynaptic AChRs at the embryonic NMJ in vivo and in cultured muscle cells. Inhibition of NOS reduced AChR aggregation at embryonic Xenopus NMJs by 50-90%, whereas overexpression of NOS increased AChR aggregate area 2- to 3-fold at these synapses. NOS inhibitors completely blocked agrin-induced AChR aggregation in cultured embryonic muscle cells. Application of NO donors to muscle cells induced AChR clustering in the absence of agrin. Our results indicate that NOS activity is necessary for postsynaptic differentiation of embryonic NMJs and that NOS is a likely participant in the agrin-MuSK signaling pathway of skeletal muscle cells.
Schwarte
Russell C
RC
Department of Pathology and Anatomy, Eastern Virginia Medical School, Norfolk, VA 23501, USA.
Godfrey
Earl W
EW
D018171:Agrin / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D002478:Cells, Cultured; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D009469:Neuromuscular Junction / Q000196:embryology* / Q000201:enzymology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011940:Receptor Aggregation / Q000187:drug effects; D011950:Receptors, Cholinergic / Q000378:metabolism; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013569:Synapses / Q000201:enzymology; D014982:Xenopus laevis / Q000196:embryology* / Q000378:metabolism*
D018171:Agrin; D020030:Nitric Oxide Donors; D011950:Receptors, Cholinergic; D011994:Recombinant Proteins; D019001:Nitric Oxide Synthase