IHG-1 Amplifies TGF-β1 Signaling and Is Increased in Renal Fibrosis
Induced in high glucose-1 (IHG-1) is an evolutionarily conserved gene transcript upregulated by high extracellular glucose concentrations, but its function is unknown. Here, it is reported that the abundance of IHG-1 mRNA is nearly 10-fold higher in microdissected, tubule-rich renal biopsies from pa...
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Published in | Journal of the American Society of Nephrology Vol. 19; no. 9; pp. 1672 - 1680 |
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Main Authors | , , , , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Hagerstown, MD
Lippincott Williams & Wilkins
01.09.2008
American Society of Nephrology |
Subjects | |
Online Access | Get full text |
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Summary: | Induced in high glucose-1
(IHG-1) is an evolutionarily conserved gene transcript upregulated by high extracellular glucose concentrations, but its function is unknown. Here, it is reported that the abundance of IHG-1 mRNA is nearly 10-fold higher in microdissected, tubule-rich renal biopsies from patients with diabetic nephropathy compared with control subjects. In the diabetic nephropathy specimens,
in situ
hybridization localized IHG-1 to tubular epithelial cells along with TGF-β1 and activated Smad3, suggesting a possible role in the development of tubulointerstitial fibrosis. Supporting this possibility, IHG-1 mRNA and protein expression also increased with unilateral ureteral obstruction. In the HK-2 proximal tubule cell line, overexpression of IHG-1 increased TGF-β1–stimulated expression of connective tissue growth factor and fibronectin. IHG-1 was found to amplify TGF-β1–mediated transcriptional activity by increasing and prolonging phosphorylation of Smad3. Conversely, inhibition of endogenous IHG-1 with small interference RNA suppressed transcriptional responses to TGF-β1. In summary, IHG-1, which increases in diabetic nephropathy, may enhance the actions of TGF-β1 and contribute to the development of tubulointerstitial fibrosis. |
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Bibliography: | J.H.'s current affiliation is Division of Experimental Pathology, Lund University, University Hospital, Malmö, Sweden. M.K.'s current affiliation is Division of Nephrology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan. Correspondence: Dr. Madeline Murphy, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland. Phone: +353-1-7166818; Fax: +353-1-7166713; E-mail: madeline.murphy@ucd.ie Published online ahead of print. Publication date available at www.jasn.org. |
ISSN: | 1046-6673 1533-3450 |
DOI: | 10.1681/asn.2007101080 |