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Sorting of mannose 6-phosphate receptors and lysosomal membrane proteins in endocytic vesicles.
- Source :
-
The Journal of cell biology [J Cell Biol] 1988 Dec; Vol. 107 (6 Pt 2), pp. 2491-501. - Publication Year :
- 1988
-
Abstract
- The intracellular distributions of the cation-independent mannose 6-phosphate receptor (MPR) and a 120-kD lysosomal membrane glycoprotein (lgp120) were studied in rat hepatoma cells. Using quantitative immunogold cytochemistry we found 10% of the cell's MPR located at the cell surface. In contrast, lgp120 was not detectable at the plasma membrane. Intracellularly, MPR mainly occurred in the trans-Golgi reticulum (TGR) and endosomes. lgp120, on the other hand, was confined to endosomes and lysosomes. MPR was present in both endosomal tubules and vacuoles, whereas lgp120 was confined to the endosomal vacuoles. In cells incubated for 5-60 min with the endocytic tracer cationized ferritin, four categories of endocytic vacuoles could be discerned, i.e., vacuoles designated MPR+/lgp120-, MPR+/lgp120+, MPR-/lgp120+, and vacuoles nonimmunolabeled for MPR and lgp120. Tracer first reached MPR+/lgp120-, then MPR+/lgp120+, and finally MPR-/lgp120+ vacuoles, which are assumed to represent lysosomes. To study the kinetics of appearance of endocytic tracers in MPR-and/or lgp120-containing pools in greater detail, cells were allowed to endocytose horse-radish peroxidase (HRP) for 5-90 min. The reduction in detectability of MPR and lgp120 antigenicity on Western blots, due to treatment of cell homogenates with 3'3-diaminobenzidine, was followed in time. We found that HRP reached the entire accessible pool of MPR almost immediately after internalization of the tracer, while prolonged periods of time were required for HRP to maximally access lgp120. The combined data suggest that MPR+/lgp120+ vacuoles are endocytic vacuoles, intermediate between MPR+/lgp120-endosomes and MPR-/lgp120+ lysosomes, and represent the site where MPR is sorted from lgp120 destined for lysosomes. We propose that MPR is sorted from lgp120 by selective lateral distribution of the receptor into the tubules of this compartment, resulting in the retention of lgp120 in the vacuoles and the net transport of lgp120 to lysosomes.
- Subjects :
- Animals
Blotting, Western
Carcinoma, Hepatocellular
Carrier Proteins analysis
Endocytosis
Golgi Apparatus analysis
Horseradish Peroxidase metabolism
Immunohistochemistry
Kinetics
Liver Neoplasms
Lysosomes ultrastructure
Membrane Glycoproteins analysis
Microscopy, Electron
Rats
Receptor, IGF Type 2
Tumor Cells, Cultured
Carrier Proteins metabolism
Hexosephosphates metabolism
Lysosomes metabolism
Mannosephosphates metabolism
Membrane Glycoproteins metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9525
- Volume :
- 107
- Issue :
- 6 Pt 2
- Database :
- MEDLINE
- Journal :
- The Journal of cell biology
- Publication Type :
- Academic Journal
- Accession number :
- 2849607
- Full Text :
- https://doi.org/10.1083/jcb.107.6.2491