Guanylate cyclase and cyclic GMP-dependent protein kinase regulate agrin signaling at the developing neuromuscular junction

Dev Biol. 2007 Jul 15;307(2):195-201. doi: 10.1016/j.ydbio.2007.04.021. Epub 2007 Apr 24.


During formation of the neuromuscular junction (NMJ), agrin secreted by motor axons signals the embryonic muscle cells to organize a postsynaptic apparatus including a dense aggregate of acetylcholine receptors (AChRs). Agrin signaling at the embryonic NMJ requires the activity of nitric oxide synthase (NOS). Common downstream effectors of NOS are guanylate cyclase (GC), which synthesizes cyclic GMP, and cyclic GMP-dependent protein kinase (PKG). Here we show that GC and PKG are important for agrin signaling at the embryonic NMJ of the frog, Xenopus laevis. Inhibitors of both GC and PKG reduced endogenous AChR aggregation in embryonic muscles by 50-85%, and blocked agrin-induced AChR aggregation in cultured embryonic muscle cells. A cyclic GMP analog, 8-bromo-cyclic GMP, increased endogenous AChR aggregation in embryonic muscles to 3- to 4-fold control levels. Overexpression of either GC or PKG in embryos increased AChR aggregate area by 60-170%, whereas expression of a dominant negative form of GC inhibited endogenous aggregation by 50%. These results indicate that agrin signaling in embryonic muscle cells requires the activity of GC and PKG as well as NOS.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agrin / metabolism*
  • Animals
  • Animals, Genetically Modified
  • Cyclic GMP-Dependent Protein Kinases / metabolism*
  • Green Fluorescent Proteins / genetics
  • Guanylate Cyclase / metabolism*
  • Neuromuscular Junction / embryology*
  • Neuromuscular Junction / metabolism*
  • Receptor Aggregation
  • Receptors, Cholinergic / metabolism
  • Recombinant Proteins / genetics
  • Signal Transduction
  • Xenopus Proteins / metabolism
  • Xenopus laevis / embryology
  • Xenopus laevis / genetics
  • Xenopus laevis / metabolism


  • Agrin
  • Receptors, Cholinergic
  • Recombinant Proteins
  • Xenopus Proteins
  • Green Fluorescent Proteins
  • Cyclic GMP-Dependent Protein Kinases
  • Guanylate Cyclase