Aberrant hypertrophy in Smad3-deficient chondrocytes is rescued by restoring TAK1-ATF-2 signaling: a potential clinical implication for osteoarthritis
| Autor: | Li, Tian-Fang, Gao, Lin, Sheu, Tzong-Jen, Sampson, Erik R., Flick, Lisa M., Konttinen, Yrjo T., Chen, Di, Schwarz, Edward M., Zuscik, Michael J., Jonason, Jennifer H., O’Keefe, Regis J. |
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| Jazyk: | angličtina |
| Rok vydání: | 2010 |
| Předmět: |
Mice
Knockout Activating Transcription Factor 2 Reverse Transcriptase Polymerase Chain Reaction Blotting Western Cell Differentiation Immunohistochemistry p38 Mitogen-Activated Protein Kinases Article Transforming Growth Factor beta1 Mice Chondrocytes Osteoarthritis Disease Progression Animals Smad3 Protein Phosphorylation Cells Cultured Signal Transduction |
| Popis: | To investigate the biologic significance of Smad3 in the progression of osteoarthritis (OA), the crosstalk between Smad3 and activating transcription factor 2 (ATF-2) in the transforming growth factor beta (TGFbeta) signaling pathway, and the effects of ATF-2 overexpression and p38 activation in chondrocyte differentiation.Joint disease in Smad3-knockout (Smad3(-/-)) mice was examined by microfocal computed tomography and histologic analysis. Numerous in vitro methods including immunostaining, real-time polymerase chain reaction, Western blotting, an ATF-2 DNA-binding assay, and a p38 kinase activity assay were used to study the various signaling responses and protein interactions underlying the altered chondrocyte phenotype in Smad3(-/-) mice.In Smad3(-/-) mice, an end-stage OA phenotype gradually developed. TGFbeta-activated kinase 1 (TAK1)/ATF-2 signaling was disrupted in Smad3(-/-) mouse chondrocytes at the level of p38 MAP kinase (MAPK) activation, resulting in reduced ATF-2 phosphorylation and transcriptional activity. Reintroduction of Smad3 into Smad3(-/-) cells restored the normal p38 response to TGFbeta. Phosphorylated p38 formed a complex with Smad3 by binding to a portion of Smad3 containing both the MAD homology 1 and linker domains. Additionally, Smad3 inhibited the dephosphorylation of p38 by MAPK phosphatase 1 (MKP-1). Both ATF-2 overexpression and p38 activation repressed type X collagen expression in wild-type and Smad3(-/-) chondrocytes. P38 was detected in articular cartilage and perichondrium; articular and sternal chondrocytes expressed p38 isoforms alpha, beta, and gamma, but not delta.Smad3 is involved in both the onset and progression of OA. Loss of Smad3 abrogates TAK1/ATF-2 signaling, most likely by disrupting the Smad3-phosphorylated p38 complex, thereby promoting p38 dephosphorylation and inactivation by MKP-1. ATF-2 and p38 activation inhibit chondrocyte hypertrophy. Modulation of p38 isoform activity may provide a new therapeutic approach for OA. |
| Databáze: | OpenAIRE |
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