It is a major proteoglycan component in the glomerular basement membrane and may play a role in the renal filtration and cell-matrix interactions.

[19] A protein called rapsyn is then recruited to the primary MuSK scaffold, to induce the additional clustering of acetylcholine receptors (AChR).

A protein called Dok-7 has shown to be additionally required for the formation of the secondary scaffold; it is apparently recruited after MuSK phosphorylation and before acetylcholine receptors are clustered.

[20] Heparan sulfate glycosaminoglycans covalently linked to the agrin protein have been shown to play a role in the clustering of AChR.

Interference in the correct formation of heparan sulfate through the addition of chlorate to skeletal muscle cell culture results in a decrease in the frequency of spontaneous acetylcholine receptor (AChR) clustering.

It may be that rather than solely binding directly to the agrin protein core a number of components of the secondary scaffold may also interact with its heparan sulfate side-chains.

[21] A role in the retention of anionic macromolecules within the vasculature has also been suggested for agrin-linked HS at the glomerular or alveolar basement membrane.

[25][26] In addition, by its ability to activate the Hippo signaling pathway, agrin is emerging as a key proteoglycan in the tumor microenvironment.