Several agrin (AGRN) ligands require the presence of its heparan-sulfate sidechains and probably represent interactions with them. Membrane-associated ligands include the neural cell adhesion molecule NCAM1 (Burg et al. 1995, Tsen et al. 1995, Cole & Halfter 1996 - see REACT_19071) and PTPRS (receptor protein tyrosine phosphatase sigma) (Aricescu et al. 2002).