Assembly and secretion of fibrinogen. Degradation of individual chains

Hep G2 cells produce surplus A alpha and gamma fibrinogen chains. These excess chains, which are not secreted, exist primarily as free gamma chains and as an A alpha-gamma complex. We have determined the intracellular location and the degradative fate of these polypeptides by treatment with endoglyc...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of biological chemistry 1992-11, Vol.267 (32), p.23151-23158
Main Authors: ROY, S, YU, S, BANERJEE, D, OVERTON, O, MUKHOPADHYAY, G, ODDOUX, C, GRIENINGER, G, REDMAN, C
Format: Article
Language:English
Subjects:
Ammonium Chloride - pharmacology
Analytical, structural and metabolic biochemistry
Animals
assembly
Biochemistry & Molecular Biology
Biological and medical sciences
Cell Line
Chickens
Chloroquine - pharmacology
fibrinogen
Fibrinogen - biosynthesis
Fibrinogen - metabolism
Fundamental and applied biological sciences. Psychology
Glycoproteins
Hep G2 cells
Humans
Kinetics
Leupeptins - pharmacology
Life Sciences & Biomedicine
Liver - metabolism
Lysosomes - drug effects
Lysosomes - enzymology
Macromolecular Substances
man
Methionine - metabolism
Proteins
Science & Technology
secretion
Sulfur Radioisotopes
Transfection
Tumor Cells, Cultured
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Hep G2 cells produce surplus A alpha and gamma fibrinogen chains. These excess chains, which are not secreted, exist primarily as free gamma chains and as an A alpha-gamma complex. We have determined the intracellular location and the degradative fate of these polypeptides by treatment with endoglycosidase-H and by inhibiting lysosomal enzyme activity, using NH4Cl, chloroquine, and leupeptin. Free gamma chain and the gamma component of A alpha-gamma are both cleaved by endoglycosidase-H, indicating that the gamma chains accumulate in a pre-Golgi compartment. Lysosomal enzyme inhibitors did not affect the disappearance of free gamma chains but inhibited A alpha-gamma by 50%, suggesting that A alpha-gamma is degraded in lysosomes. The degradative fate of individual chains was determined in transfected COS cells which express but do not secrete single chains. Leupeptin did not affect B beta chain degradation, had very little affect on gamma chain, but markedly inhibited A alpha chain degradation. Antibody to immunoglobulin heavy chain-binding protein (GRP 78) co-immunoprecipitated B beta but not A alpha or gamma chains. Preferential binding of heavy chain-binding protein to B beta was also noted in Hep G2 cells and in chicken hepatocytes. Taken together these studies indicate that B beta and gamma chains are degraded in the endoplasmic reticulum, but only B beta is bound to BiP. By contrast A alpha chains and the A alpha-gamma complex undergo lysosomal degradation.
ISSN:0021-9258
1083-351X
DOI:10.1016/s0021-9258(18)50069-7