The kinetics of mannose 6-phosphate receptor trafficking in the endocytic pathway in HEp-2 cells: the receptor enters and rapidly leaves multivesicular endosomes without accumulating in a prelysosomal compartment.
We have previously shown that in HEp-2 cells, multivesicular bodies (MVBs) processing internalized epidermal growth factor-epidermal growth factor receptor complexes mature and fuse directly with lysosomes in which the complexes are degraded. The MVBs do not fuse with a prelysosomal compartment enriched in mannose 6-phosphate receptor (M6PR) as has been described in other cell types. Here we show that the cation-independent M6PR does not become enriched in the endocytic pathway en route to the lysosome, but if a pulse of M6PR or an M6PR ligand, cathepsin D, is followed, a significant fraction of these proteins are routed from the trans-Golgi to MVBs. Accumulation of M6PR does not occur because when the ligand dissociates, the receptor rapidly leaves the MVB. At steady state, most M6PR are distributed within the trans-Golgi and trans-Golgi network and in vacuolar structures distributed in the peripheral cytoplasm. We suggest that these M6PR-rich vacuoles are on the return route from MVBs to the trans-Golgi network and that a separate stable M6PR-rich compartment equivalent to the late endosome/prelysosome stage does not exist on the endosome-lysosome pathway in these cells.
Hirst
J
J
Medical Research Council Laboratory for Molecular Cell Biology, University College, London WC1E 6BQ, United Kingdom.
Futter
C E
CE
Hopkins
C R
CR
D001692:Biological Transport; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology; D002402:Cathepsin D / Q000378:metabolism; D002451:Cell Compartmentation; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008247:Lysosomes / Q000378:metabolism; D017527:Receptor, IGF Type 2 / Q000378:metabolism*; D011990:Receptors, Transferrin / Q000378:metabolism; D014407:Tumor Cells, Cultured
D017527:Receptor, IGF Type 2; D011990:Receptors, Transferrin; D066246:ErbB Receptors; D002402:Cathepsin D