Degradative processing of internalized insulin in isolated adipocytes

Journal Article · Tue Nov 05 04:00:00 EST 1985 · J. Biol. Chem.; (United States)

OSTI ID:6182126

Marshall, S

Based on the distribution of SVI-insulin between the cell surface and the cell interior, it was found that insulin rapidly binds (t 1/2 = 0.4 min) to surface receptors at 37 degrees C, and after an initial lag period of about 1 min, accumulates intracellularly until steady state is reached (t 1/2 = 3.5 min). At this time about 40% of the total cell-associated SVI-insulin resides in the cell interior reflecting a dynamic equilibrium between the rate of insulin endocytosis and the rate at which internalized insulin is processed and extruded from cells. Since this percentage decreased to 15% at 16 degrees C, it appears that internalization is more temperative-sensitive than the intracellular processing of insulin. When SVI-insulin was preloaded into the cell interior, it was found that internalized insulin was rapidly released to the medium at 37 degrees C (t 1/2 = 6.5 min) and consisted of both degraded products and intact insulin (as assessed by trichloroacetic acid precipitability and column chromatography). Since 75% of internalized insulin was ultimately degraded, and 25% was released intact, this indicates that degradation is the predominant pathway. To determine when incoming insulin enters a degradative compartment, cells were continually exposed to SVI-insulin and the composition of insulin in the cell interior over time was assessed. After 2 min all endocytosed insulin was intact, between 2-3 min degradation products began accumulating intracellularly, and by 15 min equilibrium was reached with 20% of internalized insulin consisting of degraded products. Degraded insulin was then released from the cell interior within 4-5 min after endocytotic uptake, since this was the earliest time chloroquine was found to inhibit the release of degradation products.

• Research Organization: Univ. of California, San Diego
• OSTI ID: 6182126
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 25; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ADIPOSE TISSUE
ANIMAL TISSUES
ANIMALS
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL PATHWAYS
BODY
CONNECTIVE TISSUE
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
HORMONES
IN VITRO
INSULIN
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGANDS
MAMMALS
NUCLEI
ODD-EVEN NUCLEI
PEPTIDE HORMONES
RADIOISOTOPES
RATS
REACTION KINETICS
RECEPTORS
RODENTS
TISSUES
TRACER TECHNIQUES
VERTEBRATES