TGF-β Suppresses Ift88 Expression in Chondrocytic ATDC5 Cells

• Published in: Journal of cellular physiology 2015-11, Vol.230 (11), p.2788-2795
• Main Authors: Kawasaki, Makiri, Ezura, Yoichi, Hayata, Tadayoshi, Notomi, Takuya, Izu, Yayoi, Noda, Masaki
• Format: Article
• Language: English
• Subjects: Animals; Cartilage diseases; Cartilage, Articular - metabolism; Cell culture; Chondrocytes; Chondrocytes - metabolism; Cilia; Cilia - metabolism; Cilia - pathology; Collagen (type II); Cycloheximide; Extracellular matrix; Gene expression; Gene Expression Regulation - drug effects; IFT88 gene; Inhibitors; Matrix protein; Mice; mRNA stability; Osteoarthritis; Osteoarthritis - genetics; Osteoarthritis - metabolism; Osteoarthritis - pathology; Phosphorylation; Post-transcription; Protein biosynthesis; Protein synthesis; Protein transport; Proteins; Signal Transduction; siRNA; Transforming Growth Factor beta - administration & dosage; Transforming Growth Factor beta - metabolism; Transforming growth factor-b; Tumor Suppressor Proteins - biosynthesis; Tumor Suppressor Proteins - genetics; Tumor Suppressor Proteins - metabolism
• ISSN: 0021-9541; 1097-4652
• DOI: 10.1002/jcp.25005

Ift88 is an intraflagella transport protein, critical for the cilium, and has been shown to be required for the maintenance of chondrocytes and cartilage. However, how Ift88 is controlled by cytokines that play a role in osteoarthritis is not well understood. Therefore, we examined the effects of TGF‐β on the expression of Ift88. We used ATDC5 cells as chondrocytes and analyzed the effects of TGF‐β on gene expression. TGF‐β treatment suppresses the levels of Ift88 mRNA in a dose‐dependent manner starting from as low as 0.5 ng/mL and reaching the nadir at around 2 ng/mL. TGF‐β treatment also suppresses the protein levels of Ift88. TGF‐β suppression of Ift88 is still observed when the cells are cultured in the presence of a transcriptional inhibitor while the TGF‐β suppression is weakened in the presence of a protein synthesis inhibitor, cycloheximide. TGF‐β treatment suppresses the levels of Ift88 mRNA stability suggesting the presence of posttranscriptional regulation. TGF‐β treatment reduces the number of cilia positive cells and suppresses average length of cilia. Knockdown of Ift88 by siRNA enhances TGF‐β‐induced increase in type II collagen mRNA expression in ATDC5 cells revealing the suppressive role of Ift88 on TGF‐β‐induced regulation of extracellular matrix protein expression. TGF‐β also suppresses Ift88 mRNA expression in primary culture of rib chondrocytes. These data indicate that TGF‐β regulates Ift88 gene expression at least in part via posttrascriptional manner. J. Cell. Physiol. 9999: 2788–2795, 2015. © 2015 Wiley Periodicals, Inc.