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Media type:
E-Article
Title:
Morphologic Characterization of the Pathway of Transferrin Endocytosis and Recycling in Human KB Cells
Contributor:
Willingham, Mark C.;
Hanover, John A.;
Dickson, Robert B.;
Pastan, Ira
imprint:
National Academy of Sciences of the United States of America, 1984
Published in:Proceedings of the National Academy of Sciences of the United States of America
Language:
English
ISSN:
0027-8424
Origination:
Footnote:
Description:
<p>The pathway of transferrin uptake and recycling was investigated in KB cells to attempt to identify the organelles involved in the return of transferrin to the cell surface. Comparison was made with the pathway of internalization of epidermal growth factor (EGF), which has been shown to terminate in lysosomes. A horseradish peroxidase conjugate of transferrin (TF-HRP) was incubated with KB cells at 4 degrees C and, at various times after warming to 37 degrees C, the location of TF-HRP was examined at the electron microscopic level. Transferrin, like EGF, was found to enter cells via coated pits and to move to the Golgi region in receptosomes (endosomes). Transferrin was located in the tubular elements of the transreticular portion of the Golgi but not in Golgi stacks. Interestingly, transferrin was not concentrated in the coated pits of the Golgi. In contrast, EGF was highly concentrated there. Transferrin was next detected in tubular elements 5,000 angstrom in width and up to (≈ 600 angstrom in length) that were closely associated with microtubules and in dumbbell-shaped structures. In contrast, EGF was not detected in these structures. These results suggest that those organelles containing transferrin, but not EGF, participate in the return of receptor-bound transferrin to the cell surface.</p>