[Show abstract][Hide abstract] ABSTRACT: Matrix metalloproteinase (MMP)-13 has a pivotal, rate-limiting function in cartilage remodeling and degradation due to its specificity for cleaving type II collagen. The proximal MMP13 promoter contains evolutionarily conserved E26 transformation-specific sequence binding sites that are closely flanked by AP-1 and Runx2 binding motifs, and interplay among these and other factors has been implicated in regulation by stress and inflammatory signals. Here we report that ELF3 directly controls MMP13 promoter activity by targeting an E26 transformation-specific sequence binding site at position -78 bp and by cooperating with AP-1. In addition, ELF3 binding to the proximal MMP13 promoter is enhanced by IL-1β stimulation in chondrocytes, and the IL-1β-induced MMP13 expression is inhibited in primary human chondrocytes by siRNA-ELF3 knockdown and in chondrocytes from Elf3(-/-) mice. Further, we found that MEK/ERK signaling enhances ELF3-driven MMP13 transactivation and is required for IL-1β-induced ELF3 binding to the MMP13 promoter, as assessed by chromatin immunoprecipitation. Finally, we show that enhanced levels of ELF3 co-localize with MMP13 protein and activity in human osteoarthritic cartilage. These studies define a novel role for ELF3 as a procatabolic factor that may contribute to cartilage remodeling and degradation by regulating MMP13 gene transcription.
[Show abstract][Hide abstract] ABSTRACT: Growth arrest and DNA damage-inducible protein 45β (GADD45β) is expressed in normal and early osteoarthritic articular cartilage. We recently reported that GADD45β enhances CCAAT/enhancer binding protein β (C/EBPβ) activation in vitro. This study was undertaken in order to determine whether GADD45β is expressed with C/EBPβ in aging articular cartilage. We also investigated whether the synergistic expression of GADD45β and C/EBPβ may be involved in the mechanism of chondrocyte senescence. Senescence-accelerated mice (SAMP1) were used as a model of aging. GADD45β, C/EBPβ, and p21 were analyzed by immunohistochemistry. A luciferase reporter assay using ATDC5 cells was performed in order to examine p21 as a target gene of the GADD45β/C/EBPβ cascade. GADD45β exhibited increased expression in the aging articular cartilage of SAMP1 mice compared to that in control mice. The co-localization of GADD45β and C/EBPβ was confirmed by double immunostaining. The synergistic mechanisms of GADD45β and C/EBPβ on the gene regulation of p21, a molecule related to cellular senescence, were verified by a p21-luciferase reporter assay. Co-expression of C/EBPβ and p21 was confirmed. These observations suggest that the synergism between GADD45β and C/EBPβ may play an important role in cellular senescence in the aging articular cartilage.
Pathology - Research and Practice 02/2011; 207(4):225-31. DOI:10.1016/j.prp.2011.01.007 · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: GADD45beta (growth arrest- and DNA damage-inducible) interacts with upstream regulators of the JNK and p38 stress response kinases. Previously, we reported that the hypertrophic zone of the Gadd45beta(-/-) mouse embryonic growth plate is compressed, and expression of type X collagen (Col10a1) and matrix metalloproteinase 13 (Mmp13) genes is decreased. Herein, we report that GADD45beta enhances activity of the proximal Col10a1 promoter, which contains evolutionarily conserved AP-1, cAMP-response element, and C/EBP half-sites, in synergism with C/EBP family members, whereas the MMP13 promoter responds to GADD45beta together with AP-1, ATF, or C/EBP family members. C/EBPbeta expression also predominantly co-localizes with GADD45beta in the embryonic growth plate. Moreover, GADD45beta enhances C/EBPbeta activation via MTK1, MKK3, and MKK6, and dominant-negative p38alphaapf, but not JNKapf, disrupts the combined trans-activating effect of GADD45beta and C/EBPbeta on the Col10a1 promoter. Importantly, GADD45beta knockdown prevents p38 phosphorylation while decreasing Col10a1 mRNA levels but does not affect C/EBPbeta binding to the Col10a1 promoter in vivo, indicating that GADD45beta influences the transactivation function of DNA-bound C/EBPbeta. In support of this conclusion, we show that the evolutionarily conserved TAD4 domain of C/EBPbeta is the target of the GADD45beta-dependent signaling. Collectively, we have uncovered a novel molecular mechanism linking GADD45beta via the MTK1/MKK3/6/p38 axis to C/EBPbeta-TAD4 activation of Col10a1 transcription in terminally differentiating chondrocytes.
[Show abstract][Hide abstract] ABSTRACT: GADD45β (growth arrest- and DNA damage-inducible) interacts with upstream regulators of the JNK and p38 stress response kinases.
Previously, we reported that the hypertrophic zone of the Gadd45β−/− mouse embryonic growth plate is compressed, and expression of type X collagen (Col10a1) and matrix metalloproteinase 13 (Mmp13) genes is decreased. Herein, we report that GADD45β enhances activity of the proximal Col10a1 promoter, which contains evolutionarily conserved AP-1, cAMP-response element, and C/EBP half-sites, in synergism with C/EBP
family members, whereas the MMP13 promoter responds to GADD45β together with AP-1, ATF, or C/EBP family members. C/EBPβ expression also predominantly co-localizes
with GADD45β in the embryonic growth plate. Moreover, GADD45β enhances C/EBPβ activation via MTK1, MKK3, and MKK6, and dominant-negative
p38αapf, but not JNKapf, disrupts the combined trans-activating effect of GADD45β and C/EBPβ on the Col10a1 promoter. Importantly, GADD45β knockdown prevents p38 phosphorylation while decreasing Col10a1 mRNA levels but does not affect C/EBPβ binding to the Col10a1 promoter in vivo, indicating that GADD45β influences the transactivation function of DNA-bound C/EBPβ. In support of this conclusion, we show
that the evolutionarily conserved TAD4 domain of C/EBPβ is the target of the GADD45β-dependent signaling. Collectively, we
have uncovered a novel molecular mechanism linking GADD45β via the MTK1/MKK3/6/p38 axis to C/EBPβ-TAD4 activation of Col10a1 transcription in terminally differentiating chondrocytes.
Journal of Biological Chemistry 03/2010; 285(11):8395-8407. · 4.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Synoviolin is an E3 ubiquitin ligase, and its overexpression is implicated in the pathogenesis of rheumatoid arthritis (RA). We reported previously that Ets binding site 1 (EBS-1) within the synoviolin promoter is crucial for the expression of synoviolin, and GA binding protein (GABP) binds to this site. This study was undertaken to elucidate the precise mechanisms of transcriptional regulation via EBS-1.
We performed purification and identification of complex components that bind to EBS-1 and inspected their contributions to the transcriptional regulation of synoviolin in rheumatoid synovial cells. We biochemically purified proteins that had EBS-1 binding activity and identified the proteins using liquid chromatography tandem mass spectrometry analysis. The identified proteins were verified to recruit and form the complex on EBS-1 using electrophoretic mobility shift assay and coimmunoprecipitation assay. Furthermore, their transcription activities were tested by reporter assays and RNA interference experiments.
We identified interleukin enhancer binding factor 3 (ILF-3) as a novel factor in the complex. ILF-3 was demonstrated to activate the synoviolin promoter via association with GABPalpha in rheumatoid synovial cells. In addition, further activation was observed with ILF-2 and GABPbeta, previously reported interactants of ILF-3 and GABPalpha, respectively. Moreover, ILF-3-knockdown experiments showed reduced expression of the synoviolin gene.
Our findings indicate that ILF-3, which has been known to regulate IL-2 expression in T cells, up-regulates synoviolin expression with GABPalpha in rheumatoid synovial cells. ILF-3 might be a target for RA treatment through its effect on IL-2 in T cells and synoviolin in rheumatoid synovial cells.
[Show abstract][Hide abstract] ABSTRACT: In osteoarthritis (OA), adult articular chondrocytes undergo phenotypic modulation in response to alterations in the environment owing to mechanical injury and inflammation. These processes not only stimulate the production of enzymes that degrade the cartilage matrix but also inhibit repair. With the use of in vitro and in vivo models, new genes, not known previously to act in cartilage, have been identified and their roles in chondrocyte differentiation during development and in dysregulated chondrocyte function in OA have been examined. These new genes include growth arrest and DNA damage (GADD)45beta and the epithelial-specific ETS (ESE)-1 transcription factor, induced by bone morphogenetic protein (BMP)-2 and inflammatory cytokines, respectively. Both genes are induced by NF-kappaB, suppress COL2A1 and upregulate matrix meatalloproteinase-13 (MMP-13) expression. These genes have also been examined in mouse models of OA, in which discoidin domain receptor 2 is associated with MMP-13-mediated remodelling, in order to understand their roles in physiological cartilage homoeostasis and joint disease.
Annals of the rheumatic diseases 12/2008; 67 Suppl 3(Suppl 3):iii75-82. DOI:10.1136/ard.2008.098764 · 10.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Our previous study suggested that growth arrest and DNA damage–inducible protein 45β (GADD45β) prolonged the survival of hypertrophic chondrocytes in the developing mouse embryo. This study was undertaken, therefore, to investigate whether GADD45β plays a role in adult articular cartilage.
Gene expression profiles of cartilage from patients with late-stage osteoarthritis (OA) were compared with those from patients with early OA and normal controls in 2 separate microarray analyses. Histologic features of cartilage were graded using the Mankin scale, and GADD45β was localized by immunohistochemistry. Human chondrocytes were transduced with small interfering RNA (siRNA)–GADD45β or GADD45β-FLAG. GADD45β and COL2A1 messenger RNA (mRNA) levels were analyzed by real-time reverse transcriptase–polymerase chain reaction, and promoter activities were analyzed by transient transfection. Cell death was detected by Hoechst 33342 staining of condensed chromatin.
GADD45β was expressed at higher levels in cartilage from normal donors and patients with early OA than in cartilage from patients with late-stage OA. All chondrocyte nuclei in normal cartilage immunostained for GADD45β. In early OA cartilage, GADD45β was distributed variably in chondrocyte clusters, in middle and deep zone cells, and in osteophytes. In contrast, COL2A1, other collagen genes, and factors associated with skeletal development were up-regulated in late OA, compared with early OA or normal cartilage. In overexpression and knockdown experiments, GADD45β down-regulated COL2A1 mRNA and promoter activity. NF-κB overexpression increased GADD45β promoter activity, and siRNA-GADD45β decreased cell survival per se and enhanced tumor necrosis factor α–induced cell death in human articular chondrocytes.
These observations suggest that GADD45β might play an important role in regulating chondrocyte homeostasis by modulating collagen gene expression and promoting cell survival in normal adult cartilage and in early OA.
[Show abstract][Hide abstract] ABSTRACT: The epithelium-specific ETS (ESE)-1 transcription factor is induced in chondrocytes by interleukin-1beta (IL-1beta). We reported previously that early activation of EGR-1 by IL-1beta results in suppression of the proximal COL2A1 promoter activity by displacement of Sp1 from GC boxes. Here we report that ESE-1 is a potent transcriptional suppressor of COL2A1 promoter activity in chondrocytes and accounts for the sustained, NF-kappaB-dependent inhibition by IL-1beta. Of the ETS factors tested, this response was specific to ESE-1, since ESE-3, which was also induced by IL-1beta, suppressed COL2A1 promoter activity only weakly. In contrast, overexpression of ETS-1 increased COL2A1 promoter activity and blocked the inhibition by IL-1beta. These responses to ESE-1 and ETS-1 were confirmed using siRNA-ESE1 and siRNA-ETS1. In transient cotransfections, the inhibitory responses to ESE-1 and IL-1beta colocalized in the -577/-132 bp promoter region, ESE-1 bound specifically to tandem ETS sites at -403/-381 bp, and IL-1-induced binding of ESE-1 to the COL2A1 promoter was confirmed in vivo by ChIP. Our results indicate that ESE-1 serves a potent repressor function by interacting with at least two sites in the COL2A1 promoter. However, the endogenous response may depend upon the balance of other ETS factors such as ETS-1, and other IL-1-induced factors, including EGR-1 at any given time. Intracellular ESE-1 staining in chondrocytes in cartilage from patients with osteoarthritis (OA), but not in normal cartilage, further suggests a fundamental role for ESE-1 in cartilage degeneration and suppression of repair.
[Show abstract][Hide abstract] ABSTRACT: Synoviolin, also called HRD1, is an E3 ubiquitin ligase and is implicated in endoplasmic reticulum -associated degradation. In mammals, Synoviolin plays crucial roles in various physiological and pathological processes, including embryogenesis and the pathogenesis of arthropathy. However, little is known about the molecular mechanisms of Synoviolin in these actions. To clarify these issues, we analyzed the profile of protein expression in synoviolin-null cells. Here, we report that Synoviolin targets tumor suppressor gene p53 for ubiquitination. Synoviolin sequestrated and metabolized p53 in the cytoplasm and negatively regulated its cellular level and biological functions, including transcription, cell cycle regulation and apoptosis. Furthermore, these p53 regulatory functions of Synoviolin were irrelevant to other E3 ubiquitin ligases for p53, such as MDM2, Pirh2 and Cop1, which form autoregulatory feedback loops. Our results provide novel insights into p53 signaling mediated by Synoviolin.
The EMBO Journal 02/2007; 26(1):113-22. DOI:10.1038/sj.emboj.7601490 · 10.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Synoviolin is an endoplasmic reticulum (ER)-resident E3 ubiquitin ligase which plays a critical role in ER-associated degradation (ERAD). We found that Synoviolin is a novel causative factor for rheumatoid arthritis (RA), which is especially up-regulated in proliferating synovial cells in the disease. We attempted to examine the role of Synoviolin in ER stress-induced apoptosis and proliferation of synovial cells. RA synovial cells (RSCs) were refractory to ER stress-induced apoptosis compared with HEK293 or HeLa cells. RSCs were also more resistant to the apoptosis than synovial cells from osteoarthritis patients, significantly. Down-regulation of Synoviolin by siRNA increased the susceptibility to ER stress-induced apoptosis in RSCs. Knock-down of Synoviolin by siRNA did not only induce apoptosis of RSCs but also inhibited their proliferation in vitro. These data suggest that RSCs are extraordinarily refractory to ER stress-induced apoptosis, and we termed this special property 'hyper-ERAD'. Since Synoviolin is overexpressed in RSCs, and is known to play a critical role in the ERAD system as E3 ubiquitin ligase, hyper-ERAD is likely to present in these cells. Subsequently, the hyper-ERAD may cause synovial hyperplasia through its anti-apoptotic effect in RA. Further analyses are necessary to address this point, however, resistance to ER stress-induced apoptosis, or hyper-ERAD is a noteworthy new cellular characteristic of RSCs.
International Journal of Molecular Medicine 08/2006; 18(1):113-7. DOI:10.3892/ijmm.18.1.113 · 2.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To analyze the differences in gene expression profiles of chondrocytes in intact and damaged regions of cartilage from the same knee joint of patients with osteoarthritis (OA) of the knee.
We compared messenger RNA expression profiles in regions of intact and damaged cartilage (classified according to the Mankin scale) obtained from patients with knee OA. Five pairs of intact and damaged regions of OA cartilage were evaluated by oligonucleotide array analysis using a double in vitro transcription amplification technique. The microarray data were confirmed by real-time quantitative polymerase chain reaction (PCR) amplification and were compared with previously published data.
About 1,500 transcripts, which corresponded to 8% of the expressed transcripts, showed > or = 2-fold differences in expression between the cartilage tissue pairs. Approximately 10% of these transcripts (n = 151) were commonly expressed in the 5 patient samples. Accordingly, 114 genes (35 genes expressed in intact > damaged; 79 genes expressed in intact < damaged) were selected. The expression of some genes related to the wound-healing process, including cell proliferation and interstitial collagen synthesis, was higher in damaged regions than in intact regions, similar to the findings for genes that inhibit matrix degradation. Comparisons of the real-time quantitative PCR data with the previously reported data support the validity of our microarray data.
Differences between intact and damaged regions of OA cartilage exhibited a similar pattern among the 5 patients examined, indicating the presence of common mechanisms that contribute to cartilage destruction. Elucidation of this mechanism is important for the development of effective treatments for OA.
[Show abstract][Hide abstract] ABSTRACT: Chondrogenesis is the earliest phase of skeletal development, involving mesenchymal cell recruitment and migration, condensation of progenitors, and chondrocyte differentiation, and maturation and resulting in the formation of cartilage and bone during endochondral ossification. This process is controlled exquisitely by cellular interactions with the surrounding matrix, growth and differentiation factors, and other environmental factors that initiate or suppress cellular signaling pathways and transcription of specific genes in a temporal-spatial manner. Vertebrate limb development is controlled by interacting patterning systems involving prominently the fibroblast growth factor (FGF), bone morphogenetic protein (BMP), and hedgehog pathways. Both positive and negative signaling kinases and transcription factors, such as Sox9 and Runx2, and interactions among them determine whether the differentiated chondrocytes remain within cartilage elements in articular joints or undergo hypertrophic maturation prior to ossification. The latter process requires extracellular matrix remodeling and vascularization controlled by mechanisms that are not understood completely. Recent work has revealed novel roles for mediators such as GADD45beta, transcription factors of the Dlx, bHLH, leucine zipper, and AP-1 families, and the Wnt/beta-catenin pathway that interact at different stages during chondrogenesis.
[Show abstract][Hide abstract] ABSTRACT: Synoviolin is an E3 ubiquitin ligase localized in the endoplasmic reticulum (ER) and serving as ER-associated degradation system. Analysis of transgenic mice suggested that synoviolin gene dosage is implicated in the pathogenesis of arthropathy. Complete deficiency of synoviolin is fatal embryonically. Thus, alternation of Synoviolin could cause breakdown of ER homeostasis and consequently lead to disturbance of cellular homeostasis. Hence, the expression level of Synoviolin appears to be important for its biological role in cellular homeostasis under physiological and pathological conditions. To examine the control of protein level, we performed promoter analysis to determine transcriptional regulation. Here we characterize the role of synoviolin transcription in cellular homeostasis. The Ets binding site (EBS), termed EBS-1, from position -76 to -69 of the proximal promoter, is responsible for synoviolin expression in vivo and in vitro. Interestingly, transfer of EBS-1 decoy into NIH 3T3 cells conferred not only the repression of synoviolin gene expression but also a decrease in cell number. Fluorescence-activated cell sorter analysis using annexin V staining confirmed the induction of apoptosis by EBS-1 decoy and demonstrated recovery of apoptosis by overexpression of Synoviolin. Our results suggest that transcriptional regulation of synoviolin via EBS-1 plays an important role in cellular homeostasis. Our study provides novel insight into the transcriptional regulation for cellular homeostasis.