Low-density-lipoprotein receptors in human fibroblasts are not degraded in lysosomes

L. A.F. Casciola, K. I. Grant, W. Gevers, G. A. Coetzee, D. R. Van Der Westhuyzen

Research output: Contribution to journalArticlepeer-review


The rate of degradation of low-density-lipoprotein (LDL) receptors was measured in cultured human skin fibroblasts by [35S]methionine pulse-chase experiments. The half-life of LDL receptors was unaltered by inclusion of LDL in the medium (t( 1/2 ) 11 h). Neither lysosomotropic inhibitors (chloroquine or NH4Cl) nor leupeptin inhibited the rate of receptor degradation in the absence of ligand. In cells incubated at 18°C to inhibit the delivery of internalized ligands from endocytic vesicles to lysosomes, receptor degradation continued but at the expected rate of about six times lower than that at 37°C. Mutant LDL receptors defective in internalization were degraded at the same rate as normal receptors, suggesting that receptor internalization and recycling are not required for basal turnover. We conclude that the rate-limiting steps for, and probably the whole pathway of, degradation of normal LDL receptors does not take place in lysosomes.

Original languageEnglish (US)
Pages (from-to)681-683
Number of pages3
JournalBiochemical Journal
Issue number2
StatePublished - 1989
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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