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Interactions between the exocytic and endocytic pathways in polarized Madin-Darby canine kidney cells

E Orzech1, S Cohen, A Weiss

  • 1Department of Cell and Animal Biology, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel.

The Journal of Biological Chemistry
|May 16, 2000
PubMed

Insights

Newly synthesized polymeric immunoglobulin receptors travel through endosomes before reaching the cell surface. This suggests endosomal recycling governs polarized protein trafficking in Madin-Darby canine kidney cells.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Protein Trafficking

Background:

  • Polarized exocytosis of membrane proteins is crucial for cell function but involves poorly defined compartments.
  • Understanding the trafficking pathways of proteins like the polymeric immunoglobulin receptor (pIgR) is key to deciphering cellular organization.

Purpose of the Study:

  • To investigate the hypothesis that newly synthesized pIgR are targeted to endosomes from the trans-Golgi network before basolateral surface appearance.
  • To elucidate the role of endosomes in the polarized trafficking of both newly synthesized and endocytosed pIgR.

Main Methods:

  • Utilized an assay to measure the interaction of newly synthesized receptors with apical or basolateral endosomes loaded with horseradish peroxidase.
  • Studied wild-type and mutant polymeric immunoglobulin receptors in polarized Madin-Darby canine kidney cells.

Main Results:

  • Wild-type pIgR are targeted from the trans-Golgi network to both apical and basolateral endosomes during basolateral exocytosis.
  • Phosphorylation of a Ser residue in the pIgR cytoplasmic tail is involved in this trafficking.
  • Apically sorted pIgR mutants also utilized apical endosomes, suggesting segregation may occur there.
  • Both transcytosing and recycling receptors passed through apical endosomes.

Conclusions:

  • Endosomes serve as a convergence point for both biosynthetic and endocytic pathways for pIgR.
  • Endosomal recycling processes are critical for regulating the polarized trafficking of proteins in both apical and basolateral pathways.

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