Work

Cycloheximide stabilizes insulin-like growth factor-binding protein-1 (IGFBP-1) mRNA and inhibits IGFBP-1 transcription in H4-II-E rat hepatoma cells

Year: 1993

Type: article

Abstract: The insulin-like growth factor-binding proteins (IGFBPs) are a family of six proteins that modulate the biological activity of IGF-I and IGF-II and determine their bioavailability to tissues. One of the IGFBPs, IGFBP-1, is distinctive in the dynamic response of its levels in human plasma to metabolic changes. Parallel changes occur in IGFBP-1 mRNA and IGFBP-1 transcription in rat liver. Using the well differentiated H4-II-E rat hepatoma cell line as a model system, we demonstrated previously that IGFBP-1 transcription is positively regulated by dexamethasone and negatively regulated by insulin. We now examine the effect of the protein synthesis inhibitor, cycloheximide, on the hormonal regulation of IGFBP-1 gene expression. Preincubation of H4-II-E cells with 10.7 microM cycloheximide for 1.5 h did not prevent the induction of IGFBP-1 mRNA and IGFBP-1 transcription (determined in nuclear run-on assays) by dexamethasone. By contrast, cycloheximide treatment abolished the decrease in IGFBP-1 mRNA induced by insulin. Insulin rapidly decreased IGFBP-1 transcription in the absence of cycloheximide (> 50% inhibition in 20 min) and caused a similar decrease in cells pretreated with cycloheximide. Cycloheximide alone also decreased IGFBP-1 transcription. Similar results were observed with a second protein synthesis inhibitor, anisomycin, which also prevented the insulin-induced decrease in IGFBP-1 mRNA without abolishing the insulin-induced inhibition of IGFBP-1 transcription. These results suggest that although insulin decreases IGFBP-1 gene transcription in the presence of protein synthesis inhibitors, IGFBP-1 mRNA levels are maintained because of stabilization of the mRNA. Stabilization was demonstrated directly in actinomycin D-treated cells, where the t1/2 of IGFBP-1 mRNA increased from approximately 2 to approximately 20 h in the presence of cycloheximide; insulin did not affect IGFBP-1 mRNA turnover. Thus, cycloheximide-sensitive labile proteins contribute to the maintenance of basal IGFBP-1 promoter activity and the rapid turnover of IGFBP-1 mRNA, which determine the dynamic regulation of IGFBP-1 gene expression.

Source: Journal of Biological Chemistry

DOI: 10.1016/s0021-9258(19)85469-8

Authors: G.T. Ooi, D.R. Brown, D.S. Suh, L.Y. Tseng, M.M. Rechler

Institutions: National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases

Language: English

Topic: Growth Hormone and Insulin-like Growth Factors

Subfield: Endocrinology, Diabetes and Metabolism

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: hybrid

Estimated APC paid: $3,430