Studies on the Structure and Function of the Asialoglycoprotein Receptor in the Cell, in Vitro, and in Reconstituted Membranes
The hepatocyte of mammalian liver is a highly differentiated polarized cell. The plasma membrane of the hepatocyte is also complex consisting of the following differentiated regions or domains: the perisinusoidal domain facing the liver sinusoid which is carrying blood from the gastrointestinal system of the animal via the hepatic portal vein; lateral domains between two adjacent hepatocytes; the bile canaliculus formed by the opposed membranes of two adjacent hepatocytes; desmosomes, tight and gap junctions; and the basal domain attaching the hepatocyte to its connective tissue substratum (Figure 1). Each of these domains is comprised of different sets of proteins and possibly lipids which endow the domain with its characteristic function and in some cases a recognizably characteristic morphology at the electron microscope level. The perisinusoidal domain is involved in secretion of serum proteins and the uptake of small and large molecular weight material from the blood. This domain would jontain receptors involved in the cellular uptake of hormones like insulinI, other constituents in the blood including low density lipoproteins2, and glycoproteins terminated in penultimate galactose jegidues rather than the normal sialic acid residues (asialoglycoproteins3–5). The perisinusoidal domain in addition would contain factors involved in fusion of secretory vesicles arising from the trans region of the Golgi apparatus with this area of the plasma membrane.
KeywordsBile Canaliculus Plasma Membrane Fraction Asialoglycoprotein Receptor Plasma Membrane Domain Cell BioI
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