Acidification-dependent dissociation of endocytosed insulin precedes that of endocytosed proteins bearing the mannose 6-phosphate recognition marker Academic Article uri icon

Overview

MeSH Major

  • Endocytosis
  • Hexosephosphates
  • Insulin
  • Mannosephosphates
  • Receptor, Insulin
  • Receptors, Cell Surface

abstract

  • A key step in the sorting of endocytosed ligands from their receptors is dissociation, which is triggered by the acidic pH of endosomes. To determine whether dissociation occurs synchronously for all ligands, we compared in Chinese hamster ovary cells the intracellular dissociation of insulin, which dissociates between pH 6.3 and 7.0, with that of lysosomal hydrolases bearing the mannose 6-phosphate recognition marker (Man-6-P proteins), which dissociate around pH 5.8. Chinese hamster ovary cells were pulsed for 2 min with 125I-insulin, acid-washed to remove surface binding, and chased. During a 40-min period, about 50% of the internalized 125I-insulin was released intact via a retrocytotic pathway. Retrocytosis was not inhibited by monensin, suggesting that the release was not dependent on acidic endosomes. The remaining insulin dissociated from its receptor in an acidification-sensitive manner and was eventually degraded. Dissociation was 70% complete within 5 min of internalization. When cells were similarly incubated with 125I-Man-6-P proteins, about 35% of the internalized radioactivity was released during a 1-h chase, reflecting proteolytic maturation of the Man-6-P proteins. Dissociation of Man-6-P proteins was acidification-dependent (i.e. inhibited by monensin), and was 50% complete after about 11 min. The results indicate that acidification-dependent dissociation of ligands does not occur in a single step and suggest that multiple endocytic compartments are involved in receptor/ligand sorting.

publication date

  • May 25, 1990

Research

keywords

  • Academic Article

Identity

Language

  • eng

PubMed ID

  • 2160460

Additional Document Info

start page

  • 8497

end page

  • 504

volume

  • 265

number

  • 15