1,25-Dihydroxyvitamin D3 down-regulates aggrecan proteoglycan expression in immortalized rat chondrocytes through a post-transcriptional mechanism.
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.
Horton
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WE
National Institute on Aging, Gerontology Research Center, Baltimore, Maryland 21224.
Balakir
R
R
Precht
P
P
Liang
C T
CT
D053674:Aggrecans; D000818:Animals; D015152:Blotting, Northern; D002117:Calcitriol / Q000494:pharmacology*; D002356:Cartilage / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D011508:Chondroitin Sulfate Proteoglycans / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D015536:Down-Regulation; D016326:Extracellular Matrix Proteins; D037181:Lectins, C-Type; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D014158:Transcription, Genetic
C508321:Acan protein, rat; D053674:Aggrecans; D011508:Chondroitin Sulfate Proteoglycans; D016326:Extracellular Matrix Proteins; D037181:Lectins, C-Type; D011509:Proteoglycans; D012333:RNA, Messenger; D003609:Dactinomycin; D002117:Calcitriol