These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Transferrin receptors and cation-independent mannose-6-phosphate receptors deliver their ligands to two distinct subpopulations of multivesicular endosomes.
    Author: Woods JW, Goodhouse J, Farquhar MG.
    Journal: Eur J Cell Biol; 1989 Oct; 50(1):132-43. PubMed ID: 2558886.
    Abstract:
    The distribution of transferrin receptors (Tf-R) was determined in Clone 9 hepatocytes and compared to that of 215 kDa, cation-independent mannose-6-phosphate receptors (M6P-R) by double labeling. Cells were allowed to take up exogenous human transferrin (Tf) for 5 to 30 min, after which Tf, Tf-R, and M6P-R were localized by immunofluorescence using specific antibodies. All these proteins were found to be concentrated in the juxtanuclear or Golgi region. When Clone 9 cells were treated with NH4Cl to trap M6P-R in endosomes (Brown, W. J., J. Goodhouse, M. G. Farquhar: J. Cell Biol. 103, 1235-1247 (1986)), the distribution of the two receptors differed: Tf-R remained the same as in controls, but M6P-R were localized in large vacuolated endosomes. To carry out double labeling experiments at the electron microscope level, transferrin gold conjugates (Tf-Au) were prepared, and M6P-R were detected by immunoperoxidase labeling. Tf-Au binding to the cell surface was specific as it was reduced approximately 70 to 79% in the presence of excess native Tf. When Clone 9 cells were incubated with Tf-Au at 37 degrees C for 5 to 30 min, or binding of Tf-Au was carried out at 4 degrees C followed by warming to 37 degrees C, Tf-Au was found within a peripheral tubulovesicular network and within multivesicular endosomes that were not labeled with anti-M6P-R. Other multivesicular endosomes of similar size and morphology were heavily labeled for M6P-R but contained little or no Tf-Au. Tf-Au and M6P-R were also found in separate endosomes in cells treated with NH4Cl. Native Tf was localized in the same compartments as Tf-Au by immunoperoxidase labeling of both Clone 9 cells and mouse myeloma cells. We conclude that in Clone 9 hepatocytes, Tf/Tf-R internalized from the cell surface and M6P-R bearing newly synthesized lysosomal enzymes from the Golgi deliver their ligands to two different subpopulations of multivesicular endosomes. The endosomal subpopulation visited by Tf/Tf-R is known to correspond kinetically to early endosomes. The endosomal subpopulation heavily labeled for M6P-R presumably represent a later endosomal compartment which serves as the junction point where endocytosed ligands and newly synthesized lysosomal enzymes enroute to lysosomes meet.
    [Abstract] [Full Text] [Related] [New Search]