Format

Send to

Choose Destination
Biochim Biophys Acta. 1982 Nov 24;719(2):377-87.

The degradation of endogenous and exogenous proteins in cultured smooth muscle cells.

Abstract

The pathways of degradation followed by endogenous proteins in cultured smooth muscle cells were compared with the well-characterized lysosomal pathway involved in the degradation of apolipoprotein B of endocytosed LDL. Under conditions in which lysosomal activity towards 125I-labeled LDL was almost completely inhibited by chloroquine and/or ammonium chloride, the degradation of short-lived and abnormal proteins, assessed by the release of [3H]phenylalanine, was reduced by only 10-17%. The basal rate of degradation of long-lived proteins was reduced by about 30% by the same inhibitors while the accelerated proteolysis found under nutrient-poor conditions could be completely accounted for by the lysosomal system as defined by these lysosomotrophic agents. Temperature studies indicated differences between the mechanisms involved in the degradation of long-lived proteins (Ea = 18 kcal/mol) and short-lived proteins (Ea = 10 kcal/mol). Arrhenius plots for the degradation of endogenous proteins showed no transitions between 15 and 37 degrees C in contrast to the breakdown of LDL which ceased below 20 degrees C. The results indicate that the degradation of rapid-turnover proteins is largely extralysosomal and that a significant breakdown of long-lived proteins occurs also outside lysosomes.

PMID:
7150648
DOI:
10.1016/0304-4165(82)90113-1
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center