title: Intracellular receptor sorting during endocytosis: comparative immunoelectron microscopy of multiple receptors in rat liver.
abstract: Using double-label quantitative immunoelectron microscopy on ultrathin cryosections of rat liver, we have compared the endocytotic pathways of the receptors for asialoglycoprotein (ASGP-R), mannose-6-phosphate ligands (MP-R), and polymeric IgA (IgA-R). All three were found within the Golgi complex, along the entire plasma membrane, in coated pits and vesicles, and within a compartment of uncoupling of receptors and ligand ( CURL ). The receptors occurred randomly at the cell surface, in coated pits and vesicles. Within CURL tubules ASGP-R and MP-R were colocalized , but IgA-R and ASGP-R displayed dramatic microheterogeneity. Thus, in addition to its role in uncoupling and sorting recycling receptor from ligand, CURL serves as a compartment to segregate recycling receptor (e.g. ASGP-R) from receptor involved in transcytosis (e.g. IgA-R).
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex; D037263:Asialoglycoprotein Receptor; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism / Q000648:ultrastructure; D004705:Endocytosis; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D006600:Hexosephosphates / Q000378:metabolism*; D007070:Immunoglobulin A / Q000378:metabolism*; D008099:Liver / Q000502:physiology* / Q000648:ultrastructure; D008297:Male; D008360:Mannosephosphates / Q000378:metabolism*; D008854:Microscopy, Electron; D009961:Orosomucoid / Q000031:analogs & derivatives; D051381:Rats; D011919:Rats, Inbred Strains; D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000378:metabolism*
chemical_list: D000936:Antigen-Antibody Complex; D037263:Asialoglycoprotein Receptor; D006600:Hexosephosphates; D007070:Immunoglobulin A; D008360:Mannosephosphates; D009961:Orosomucoid; D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic