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      E-Cadherin Expression Is Regulated by miR-192/215 by a Mechanism That Is Independent of the Profibrotic Effects of Transforming Growth Factor-β

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          Abstract

          OBJECTIVE

          Increased deposition of extracellular matrix (ECM) within the kidney is driven by profibrotic mediators including transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF). We investigated whether some of their effects may be mediated through changes in expression of certain microRNAs (miRNAs).

          RESEARCH DESIGN AND METHODS

          Proximal tubular cells, primary rat mesangial cells, and human podocytes were analyzed for changes in the expression of key genes, ECM proteins, and miRNA after exposure to TGF-β (1–10 ng/μl). Tubular cells were also infected with CTGF-adenovirus. Kidneys from diabetic apoE mice were also analyzed for changes in gene expression and miRNA levels.

          RESULTS

          TGF-β treatment was associated with morphologic and phenotypic changes typical of epithelial-mesenchymal transition (EMT) including increased fibrogenesis in all renal cell types and decreased E-cadherin expression in tubular cells. TGF-β treatment also modulated the expression of certain miRNAs, including decreased expression of miR-192/215 in tubular cells, mesangial cells, which are also decreased in diabetic kidney. Ectopic expression of miR-192/215 increased E-cadherin levels via repressed translation of ZEB2 mRNA, in the presence and absence of TGF-β, as demonstrated by a ZEB2 3′-untranslated region luciferase reporter assay. However, ectopic expression of miR-192/215 did not affect the expression of matrix proteins or their induction by TGF-β. In contrast, CTGF increased miR-192/215 levels, causing a decrease in ZEB2, and consequently increased E-cadherin mRNA.

          CONCLUSIONS

          These data demonstrate the linking role of miRNA-192/215 and ZEB2 in TGF-β/CTGF–mediated changes in E-cadherin expression. These changes appear to occur independently of augmentation of matrix protein synthesis, suggesting that a multistep EMT program is not necessary for fibrogenesis to occur.

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          Most cited references20

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          The two-handed E box binding zinc finger protein SIP1 downregulates E-cadherin and induces invasion.

          Transcriptional downregulation of E-cadherin appears to be an important event in the progression of various epithelial tumors. SIP1 (ZEB-2) is a Smad-interacting, multi-zinc finger protein that shows specific DNA binding activity. Here, we report that expression of wild-type but not of mutated SIP1 downregulates mammalian E-cadherin transcription via binding to both conserved E2 boxes of the minimal E-cadherin promoter. SIP1 and Snail bind to partly overlapping promoter sequences and showed similar silencing effects. SIP1 can be induced by TGF-beta treatment and shows high expression in several E-cadherin-negative human carcinoma cell lines. Conditional expression of SIP1 in E-cadherin-positive MDCK cells abrogates E-cadherin-mediated intercellular adhesion and simultaneously induces invasion. SIP1 therefore appears to be a promoter of invasion in malignant epithelial tumors.
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            MicroRNA-192 in diabetic kidney glomeruli and its function in TGF-beta-induced collagen expression via inhibition of E-box repressors.

            Key features of diabetic nephropathy (DN) include the accumulation of extracellular matrix proteins such as collagen 1-alpha 1 and -2 (Col1a1 and -2). Transforming growth factor beta1 (TGF-beta), a key regulator of these extracellular matrix genes, is increased in mesangial cells (MC) in DN. By microarray profiling, we noted that TGF-beta increased Col1a2 mRNA in mouse MC (MMC) but also decreased mRNA levels of an E-box repressor, deltaEF1. TGF-beta treatment or short hairpin RNAs targeting deltaEF1 increased enhancer activity of upstream E-box elements in the Col1a2 gene. TGF-beta also decreased the expression of Smad-interacting protein 1 (SIP1), another E-box repressor similar to deltaEF1. Interestingly, we noted that SIP1 is a target of microRNA-192 (miR-192), a key miR highly expressed in the kidney. miR-192 levels also were increased by TGF-beta in MMC. TGF-beta treatment or transfection with miR-192 decreased endogenous SIP1 expression as well as reporter activity of a SIP1 3' UTR-containing luciferase construct in MMC. Conversely, a miR-192 inhibitor enhanced the luciferase activity, confirming SIP1 to be a miR-192 target. Furthermore, miR-192 synergized with deltaEF1 short hairpin RNAs to increase Col1a2 E-box-luc activity. Importantly, the in vivo relevance was noted by the observation that miR-192 levels were enhanced significantly in glomeruli isolated from streptozotocin-injected diabetic mice as well as diabetic db/db mice relative to corresponding nondiabetic controls, in parallel with increased TGF-beta and Col1a2 levels. These results uncover a role for miRs in the kidney and DN in controlling TGF-beta-induced Col1a2 expression by down-regulating E-box repressors.
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              p53-Responsive micrornas 192 and 215 are capable of inducing cell cycle arrest.

              microRNAs provide a novel layer of regulation for gene expression by interfering with the stability and/or translation of specific target mRNAs. Overall levels of microRNAs are frequently down-regulated in cancer cells, and reducing general microRNA processing increases cancerogenesis in transgenic models, suggesting that at least some microRNAs might act as effectors in tumor suppression. Accordingly, the tumor suppressor p53 up-regulates miR-34a, a microRNA that contributes to apoptosis and acute senescence. Here, we used array hybridization to find that p53 induces two additional, mutually related clusters of microRNAs, leading to the up-regulation of miR-192, miR-194, and miR-215. The same microRNAs were detected at high levels in normal colon tissue but were severely reduced in many colon cancer samples. On the other hand, miR-192 and its cousin miR-215 can each contribute to enhanced CDKN1A/p21 levels, colony suppression, cell cycle arrest, and cell detachment from a solid support. These effects were partially dependent on the presence of wild-type p53. Antagonizing endogenous miR-192 attenuated 5-fluorouracil-induced accumulation of p21. Hence, miR-192 and miR-215 can act as effectors as well as regulators of p53; they seem to suppress cancerogenesis through p21 accumulation and cell cycle arrest.
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                Author and article information

                Journal
                Diabetes
                diabetes
                diabetes
                Diabetes
                Diabetes
                American Diabetes Association
                0012-1797
                1939-327X
                July 2010
                14 April 2010
                : 59
                : 7
                : 1794-1802
                Affiliations
                [1] 1Juvenile Diabetes Research Foundation Danielle Alberti Memorial Centre for Diabetes Complications, Diabetes Division, Baker IDI Heart and Diabetes Institute, Victoria, Australia;
                [2] 2Academic and Children's Renal Unit, University of Bristol, Bristol, U.K.;
                [3] 3Centre for Cancer Biology, SA Pathology, and Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia;
                [4] 4Department of Medicine, University of Sydney, Sydney, New South Wales, Australia.
                Author notes
                Corresponding author: Phillip Kantharidis, phillip.kantharidis@ 123456bakeridi.edu.au .
                Article
                1736
                10.2337/db09-1736
                2889781
                20393144
                69eed3ed-3078-403d-86fe-5b32e768e1bc
                © 2010 by the American Diabetes Association.

                Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.

                History
                : 2 December 2009
                : 26 March 2010
                Funding
                Funded by: National Institutes of Health
                Award ID: NHMRC367620
                Award ID: NHMRC526663
                Categories
                Complications

                Endocrinology & Diabetes
                Endocrinology & Diabetes

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