Meta-Biol

• Pathways

Asialoglycoprotein receptors 1 and 2 (ASGR1 and ASGR2) mediate the endocytosis of plasma glycoproteins whose terminal sialic acid residues on their complex carbohydrate moieties has been removed. They can bind each other to form at least a heterodimeric complex (Bischoff et al. 1988). The resultant ligand:receptor complex is internalised and transported to a sorting organelle, where receptor and ligand are disassociated. The receptor then cycles back to the cell membrane surface. Palmitoylation of ASGR1 (Cys36) and ASGR2 (Cys54, 58) is essential for efficient endocytosis of ligand by the clathrin-dependent endocytic pathway and especially for the proper dissociation and delivery of ligand to lysosomes (Saxena et al. 2002, Yik et al. 2002).