A heparan sulphate proteoglycan released by motor neurons and muscle cells that is crucial for the normal development or regeneration of neuromuscular junctions. As a growing axon makes contact with a muscle cell, the agrin acts as a signal to recruit essential components and start the formation of a synapse between the axon and muscle. Agrin binds to its receptor, called muscle-specific receptor tyrosine kinase (MuSK), in the muscle cell membrane and triggers a cascade of events that results in the accumulation of acetylcholine receptors beneath the muscle cell membrane. Binding of agrin to other receptors, such as laminin β2, is also required to stabilize the newly forming synaptic structure. Agrin is equally important in the natural regeneration of damaged neuromuscular junctions and also seems to have a role in the differentiation of presynaptic nerve terminals.
Subjects: Biological Sciences — Chemistry.