Endocytosed cation-independent mannose 6-phosphate receptor traffics via the endocytic recycling compartment en route to the trans-Golgi network and a subpopulation of late endosomes

Mol Biol Cell. 2004 Feb;15(2):721-33. doi: 10.1091/mbc.e03-07-0497. Epub 2003 Oct 31.

Abstract

Although the distribution of the cation-independent mannose 6-phosphate receptor (CI-MPR) has been well studied, its intracellular itinerary and trafficking kinetics remain uncertain. In this report, we describe the endocytic trafficking and steady-state localization of a chimeric form of the CI-MPR containing the ecto-domain of the bovine CI-MPR and the murine transmembrane and cytoplasmic domains expressed in a CHO cell line. Detailed confocal microscopy analysis revealed that internalized chimeric CI-MPR overlaps almost completely with the endogenous CI-MPR but only partially with individual markers for the trans-Golgi network or other endosomal compartments. After endocytosis, the chimeric receptor first enters sorting endosomes, and it then accumulates in the endocytic recycling compartment. A large fraction of the receptors return to the plasma membrane, but some are delivered to the trans-Golgi network and/or late endosomes. Over the course of an hour, the endocytosed receptors achieve their steady-state distribution. Importantly, the receptor does not start to colocalize with late endosomal markers until after it has passed through the endocytic recycling compartment. In CHO cells, only a small fraction of the receptor is ever detected in endosomes bearing substrates destined for lysosomes (kinetically defined late endosomes). These data demonstrate that CI-MPR takes a complex route that involves multiple sorting steps in both early and late endosomes.

Publication types

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

MeSH terms

  • Animals
  • CHO Cells
  • Cattle
  • Cell Membrane / metabolism*
  • Cricetinae
  • Cricetulus
  • Endocytosis / physiology*
  • Endosomes / metabolism*
  • Golgi Apparatus / metabolism
  • Mice
  • Microscopy, Confocal
  • Protein Transport / physiology
  • Receptor, IGF Type 2 / metabolism*
  • Recombinant Proteins / metabolism*

Substances

  • Receptor, IGF Type 2
  • Recombinant Proteins