TY - JOUR
T1 - Intracellular segregation of asialoglycoproteins and their receptor
T2 - A prelysosomal event subsequent to dissociation of the ligand-receptor complex
AU - Wolkoff, A. W.
AU - Klausner, R. D.
AU - Ashwell, G.
AU - Harford, J.
PY - 1984
Y1 - 1984
N2 - Rat hepatocytes in monolayer culture rapidly internalized asialoglycoproteins and the receptors to which they are bound. Subsequent to endocytosis, the receptor-ligand complex is dissociated within an acidic endosome (Harford, J., K. Bridges, G. Ashwell, and R.D. Klausner, 1983, J. Biol. Chem. 258:3191-3197; Harford, J., A.W. Wolkoff, G. Ashwell, and R.D. Klausner, 1983, J. Cell Biol. 96:1824-1828). Here we show that addition of the proton ionophore monensin to the cells after dissociation has occurred results in intracellular rebinding of ligand molecules. With increasing time inside the cell, the ability of ligand to reassociate with receptor progressively decreases consistent with a segregation of receptor and ligand. The combination of colchicine and cytochalasin B appears to retard the process of segregation. In contrast, removal of sodium from the medium, while inhibiting degradation of ligand, does not affect the decrease in monensin-mediated rebinding. Nonetheless, both sodium deprivation and treatment with colchicine plus cytochalasin B result in the ligand remaining in a low density, nonlysosomal subcellular fraction. Thus, segregation, like dissociation, appears to occur in a pre-lysosomal endocytic compartment. Perturbation of the endocytic pathway by reduced temperature (18°C) was also explored. Our data are consistent with two temperature-sensitive steps: receptor-ligand dissociation is inhibited and there is an independent temperature-sensitive step involved in delivery of ligand to lysosomes. This second effect was localized as being beyond the point in the pathway sensitive to sodium deprivation.
AB - Rat hepatocytes in monolayer culture rapidly internalized asialoglycoproteins and the receptors to which they are bound. Subsequent to endocytosis, the receptor-ligand complex is dissociated within an acidic endosome (Harford, J., K. Bridges, G. Ashwell, and R.D. Klausner, 1983, J. Biol. Chem. 258:3191-3197; Harford, J., A.W. Wolkoff, G. Ashwell, and R.D. Klausner, 1983, J. Cell Biol. 96:1824-1828). Here we show that addition of the proton ionophore monensin to the cells after dissociation has occurred results in intracellular rebinding of ligand molecules. With increasing time inside the cell, the ability of ligand to reassociate with receptor progressively decreases consistent with a segregation of receptor and ligand. The combination of colchicine and cytochalasin B appears to retard the process of segregation. In contrast, removal of sodium from the medium, while inhibiting degradation of ligand, does not affect the decrease in monensin-mediated rebinding. Nonetheless, both sodium deprivation and treatment with colchicine plus cytochalasin B result in the ligand remaining in a low density, nonlysosomal subcellular fraction. Thus, segregation, like dissociation, appears to occur in a pre-lysosomal endocytic compartment. Perturbation of the endocytic pathway by reduced temperature (18°C) was also explored. Our data are consistent with two temperature-sensitive steps: receptor-ligand dissociation is inhibited and there is an independent temperature-sensitive step involved in delivery of ligand to lysosomes. This second effect was localized as being beyond the point in the pathway sensitive to sodium deprivation.
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U2 - 10.1083/jcb.98.2.375
DO - 10.1083/jcb.98.2.375
M3 - Article
C2 - 6319424
AN - SCOPUS:0021337903
SN - 0021-9525
VL - 98
SP - 375
EP - 381
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 2
ER -