Segregation of transferrin to a mildly acidic (pH 6.5) para-Golgi compartment in the recycling pathway

Cell. 1984 Jul;37(3):789-800. doi: 10.1016/0092-8674(84)90414-8.


To study the intracellular sorting of internalized ligands and receptors, we examined the pathways of two ligands: transferrin, which is recycled, and alpha 2-macroglobulin (alpha 2M), which is degraded. In CHO cells the two ligands rapidly segregate into different intracellular compartments. Within 5 min fluorescein-labeled transferrin (F-Tf) is found in a large round juxtanuclear structure. Rhodamine-labeled alpha 2M is found in a punctate pattern. Ultra-structural localization studies demonstrate that colloidal gold-alpha 2M is found predominantly in endocytic vesicles, while ferritin-transferrin is found in small vesicles and tubular structures in a region adjacent to the Golgi complex. Using image intensified fluorescence microscopy and digital image analysis, we determined that the F-Tf containing structure has a pH of 6.4 +/- 0.2, while endocytic vesicles containing F-alpha 2M have a pH of 5.4 +/- 0.1. Our study defines a mildly acidic compartment, distinct from endocytic vesicles, that is involved in the recycling of internalized components back to the cell surface.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Biological Transport
  • Cell Compartmentation
  • Cell Line
  • Cell Membrane / metabolism
  • Cricetinae
  • Endocytosis
  • Female
  • Golgi Apparatus / metabolism*
  • Hydrogen-Ion Concentration
  • Kinetics
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Membrane Proteins / metabolism
  • Ovary
  • Receptors, Cell Surface / metabolism
  • Receptors, Immunologic / metabolism
  • Receptors, Transferrin
  • Transferrin / metabolism*
  • alpha-Macroglobulins / metabolism*


  • Low Density Lipoprotein Receptor-Related Protein-1
  • Membrane Proteins
  • Receptors, Cell Surface
  • Receptors, Immunologic
  • Receptors, Transferrin
  • Transferrin
  • alpha-Macroglobulins