Cytokine regulation of cartilage-derived retinoic acid-sensitive protein (CD-RAP) in primary articular chondrocytes: suppression by IL-1, bfGF, TGFbeta and stimulation by IGF-1.
Cartilage-derived retinoic acid-sensitive protein (CD-RAP) is a secreted protein identified in our laboratory by RT-PCR and differential display [U.H. Dietz, L.J. Sandell. Cloning of a retinoic acid-sensitive mDNA expressed in cartilage and during chondrogenesis. J. Biol. Chem. 271 (1996) 3311-3316]. It is synthesized by chondrocytes throughout development and down-regulated by retinoic acid in coordination with type II collagen gene expression. To further explore the regulation CD-RAP in primary articular chondrocytes, we examined effects of selected cytokines on CD-RAP gene expression compared to their effects on type II collagen expression. Northern blot analysis showed that expression of CD-RAP mRNA was suppressed by bFGF, IL-1beta and retinoic acid in coordination with type II collagen mRNA. TGF-beta decreased CD-RAP expression while increasing type II collagen mRNA whereas both mRNAs were up-regulated by IGF-1. In chondrocytes dedifferentiated with retinoic acid, IGF-1 induced re-expression of both CD-RAP and type II collagen mRNAs. The mechanism of stimulation of CD-RAP by IGF-1 was further investigated. An mRNA stability assay revealed that IGF-1 had no effect on CD-RAP or type II collagen mRNA half life, suggesting that the enhancement by IGF-1 is due to increased gene transcription. To study the transcriptional mechanism, we used the 5'-flanking region of the CD-RAP gene fused to a promoter-less reporter plasmid encoding luciferase. Deletion analysis of the CD-RAP promoter indicated that an IGF-1-responsive element is present between nucleotides -475 and -458. These data indicate that CD-RAP expression can be regulated by cytokines known to influence chondrocyte metabolism and that IGF-1 up-regulates CD-RAP gene expression through a transcriptional mechanism.
Kondo
S
S
Department of Orthopaedic Surgery, Washington University School of Medicine at Barnes-Jewish Hospital, St. Louis, MO 63110, USA.
Cha
S H
SH
Xie
W F
WF
Sandell
L J
LJ
D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D003094:Collagen / Q000235:genetics; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007375:Interleukin-1 / Q000494:pharmacology*; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000235:genetics; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D007375:Interleukin-1; D011506:Proteins; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D016222:Fibroblast Growth Factor 2; D007334:Insulin-Like Growth Factor I; D003094:Collagen