Agrin (Agrn)

Isoform 1: heparan sulfate basal lamina glycoprotein that plays a central role in the formation and the maintenance of the neuromuscular junction (NMJ) and directs key events in postsynaptic differentiation. This neuron-specific (z+) isoform is a part of the AGRN-LRP4 receptor complex that induces the phosphorylation and activation of MUSK.

The activation of MUSK in myotubes induces the formation of NMJ by regulating different procedures including the transcription of certain genes and the clustering of AChR in the postsynaptic membrane. Calcium ions are required for maximum AChR clustering.