Isolation of insulin degradation products from endosomes derived from intact rat liver

Journal Article · Sun May 15 04:00:00 EDT 1988 · J. Biol. Chem.; (United States)

OSTI ID:6925147

Hamel, F G; Posner, B I; Bergeron, J J.M.; Frank, B H; Duckworth, W C

Rats were injected with (/sup 125/I)iodoinsulin labeled at either the A14 or B26 tyrosine, and the animals were killed and livers subcellularly fractionated to yield light (early or neutral) endosomes and heavy (late or acidic) endosomes. /sup 125/I-Labeled material was extracted from endosomes and analyzed by Sephadex G-50 filtration and high performance liquid chromatography (HPLC). Radiolabeled material in both types of endosomes is comprised of high molecular weight, insulin-sized, and low molecular weight components, with B chain-labeled small molecular weight material in two peaks, one corresponding to iodotyrosine and one to small peptides. As compared with A chain label, however, less of the B chain material appears in the degradation components (both high and low molecular weight fractions) suggesting that a fragment of B chain containing the B26 residue is lost from the endosomes. Analysis on HPLC shows that significant amounts of the insulin-sized and high molecular weight material have proteolytic cleavage(s) in the B chain with an intact A chain. The B chain-derived labeled peptides elute from HPLC identically with products generated by insulin protease. These results therefore show substantial insulin degradation occurring in light endosomes prior to endosomal acidification and to receptor dissociation, suggesting receptor-bound insulin in a substrate for insulin protease.

• Research Organization: Univ. of Nebraska Medical Center, Omaha (USA)
• OSTI ID: 6925147
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 263:14; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BETA DECAY RADIOISOTOPES
BIODEGRADATION
BODY
CELL CONSTITUENTS
CHEMICAL REACTIONS
CHROMATOGRAPHY
DAYS LIVING RADIOISOTOPES
DECOMPOSITION
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
GLANDS
HORMONES
HYDROLASES
INSULIN
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPES
LIQUID COLUMN CHROMATOGRAPHY
LIVER
LYSOSOMES
MAMMALS
MEMBRANE PROTEINS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
PEPTIDE HORMONES
PEPTIDE HYDROLASES
PHAGOCYTOSIS
PROTEINS
RADIOISOTOPES
RATS
RECEPTORS
RODENTS
SEPARATION PROCESSES
SUBSTRATES
VERTEBRATES