1,25-Dihydroxyvitamin D3 down-regulates aggrecan proteoglycan expression in immortalized rat chondrocytes through a post-transcriptional mechanism

• Published in: The Journal of biological chemistry 1991-12, Vol.266 (36), p.24804-24808
• Main Authors: W E Horton, Jr, R Balakir, P Precht, C T Liang
• Format: Article
• Language: English
• Subjects: Aggrecans; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Blotting, Northern; Calcitriol - pharmacology; Cartilage - cytology; Cartilage - metabolism; Cells, Cultured; Chondroitin Sulfate Proteoglycans - metabolism; Dactinomycin - pharmacology; Down-Regulation; Extracellular Matrix Proteins; Fundamental and applied biological sciences. Psychology; Glycoproteins; Lectins, C-Type; Proteins; Proteoglycans - genetics; Proteoglycans - metabolism; Rats; RNA Processing, Post-Transcriptional; RNA, Messenger - drug effects; RNA, Messenger - metabolism; Transcription, Genetic
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)54300-3

We have examined the effects of various analogs of vitamin D on the expression of the aggrecan proteoglycan by an immortalized rat chondrocyte cell line. The active metabolite of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), produced a concentration-dependent reduction in the synthesis of aggrecan as monitored by histochemical staining of the matrix, incorporation of [35S]sulfate, and the level of aggrecan core protein. Other analogs of vitamin D were much less potent or had no activity whatsoever. The reduced expression of aggrecan was caused by a dramatic decrease in the steady-state level of the mRNA coding for the aggrecan core protein. A nuclear run-off analysis revealed that the rate of transcription of the aggrecan gene was not significantly altered by 1,25(OH)2D3 treatment, suggesting that the metabolite was acting through a post-transcriptional mechanism. Experiments using the transcriptional inhibitor actinomycin D also supported a nondirect effect of 1,25(OH)2D3 on the expression of the aggrecan gene. These results suggest that the vitamin D metabolite activates a new pattern of gene expression which results in a more rapid turnover of the aggrecan mRNA. This system should be useful for characterizing the regulation of chondrocyte gene expression by vitamin D.