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

Journal Article · Fri May 25 04:00:00 EDT 1990 · Journal of Biological Chemistry; (USA)

OSTI ID:6810005

Borden, L A; Einstein, R; Gabel, C A; Maxfield, F R ^[1]

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1. Columbia Univ., College of Physicians and Surgeons, New York, NY (USA)

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.

• OSTI ID: 6810005
• Journal Information: Journal of Biological Chemistry; (USA), Journal Name: Journal of Biological Chemistry; (USA) Vol. 265:15; ISSN 0021-9258; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
BETA DECAY RADIOISOTOPES
BIOLOGICAL MARKERS
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
BODY
CELL CONSTITUENTS
CHO CELLS
COMPARATIVE EVALUATIONS
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
FEMALE GENITALS
GONADS
HORMONES
HYDROLASES
INSULIN
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPE DILUTION
ISOTOPES
LIGANDS
LYSOSOMES
MEMBRANE PROTEINS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
OVARIES
PEPTIDE HORMONES
PH VALUE
PROTEINS
RADIOISOTOPES
RECEPTORS
SECRETION
SYNTHESIS
TRACER TECHNIQUES