Abstract
Treatment of cultured human skin fibroblasts with cycloheximide retarded the down-regulation of low density lipoprotein (LDL) receptor activity caused by 25-hydroxycholesterol. The rate of LDL receptor degradation, measured directly by means of [35S]methionine pulse-chase experiments, was also markedly inhibited by cycloheximide (or puromycin), suggesting that continuous synthesis of a short-lived mediator protein(s) was necessary for normal LDL receptor turnover. In the absence of cycloheximide, both the up- and down-regulation of LDL receptor activity took place with a half-time of approximately 12 hr. Pulse-chase measurements with [35S]methionine yielded a receptor half-life (t 1/2 ) of 11.7 ± 2.2 hr (n = 10) in up-regulated cells; the t 1/2 in the partially down-regulated state was similar. The presence of LDL or 25-hydroxycholesterol did not alter this degradation rate. Regulation of LDL receptor activity under these various culture conditions therefore probably occurred solely as a result of changes in the rate of receptor synthesis. The cycloheximide-sensitive factor(s) that influences receptor turnover apparently did not play a regulatory role in the up- or down-regulation of the LDL receptor.
Original language | English (US) |
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Pages (from-to) | 1481-1489 |
Number of pages | 9 |
Journal | Journal of Lipid Research |
Volume | 29 |
Issue number | 11 |
State | Published - 1988 |
Externally published | Yes |
ASJC Scopus subject areas
- Biochemistry
- Endocrinology
- Cell Biology