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Regulation of heavy subunit chain of gamma-glutamylcysteine synthetase by tumor necrosis factor-alpha in lens epithelial cells: role of LEDGF/p75.
Am J Physiol Cell Physiol. 2006 Feb; 290(2):C554-66.AJ

Abstract

TNF-alpha induces oxidative stress by generating reactive oxygen species (ROS). This molecule elevates the expression of gamma-glutamylcysteine synthetase heavy subunit (gamma-GCS-HS). Lens epithelium-derived growth factor (LEDGF)/p75, a transcriptional protein, is inducible by oxidative stress and protects cells from various stresses by upregulating stress-responsive genes. This paper presents evidence that TNF-alpha elevates the expression of LEDGF and that LEDGF is one of the transactivators of gamma-GCS-HS gene. An analysis of the gamma-GCS-HS promoter sequence (-819 to +518 nt) revealed the presence of putative sites for LEDGF binding. Gel mobility assay confirmed the binding of LEDGF to the heat shock element (nGAAn) and the stress response element (A/TGGGGA/T) present in gamma-GCS-HS promoter. Transactivation experiments showed activation of gamma-GCS-HS promoter in cells overexpressing LEDGF or treated with a sublethal dose of TNF-alpha (20 ng/ml). Downregulation of gamma-GCS-HS promoter activity in cells transfected with LEDGF small interfering RNA validated the finding. Notably, cells treated with TNF-alpha (20 ng/ml) for 24 h had an increased abundance of LEDGF and gamma-GCS-HS mRNA and protein. In contrast, cells treated with TNF-alpha for longer periods or with higher concentrations of TNF-alpha showed reduced expression of LEDGF and gamma-GCS-HS and increased cellular death with higher ROS levels. Cells overexpressing LEDGF revealed elevated GSH levels (10-15%), a condition that may potentially eliminate the insult to cells induced by TNF-alpha. Thus TNF-alpha regulation of LEDGF may be physiologically important, as elevated expression of LEDGF increases the expression of endogenous gamma-GCS-HS gene, the catalytic subunit of the regulating enzyme in GSH biosynthesis that may constitute a protective mechanism in limiting oxidative stress induced by inflammatory cytokines.

Authors+Show Affiliations

Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, Nebraska 68198-5840, USA.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

16403949

Citation

Takamura, Yoshihiro, et al. "Regulation of Heavy Subunit Chain of Gamma-glutamylcysteine Synthetase By Tumor Necrosis Factor-alpha in Lens Epithelial Cells: Role of LEDGF/p75." American Journal of Physiology. Cell Physiology, vol. 290, no. 2, 2006, pp. C554-66.
Takamura Y, Fatma N, Kubo E, et al. Regulation of heavy subunit chain of gamma-glutamylcysteine synthetase by tumor necrosis factor-alpha in lens epithelial cells: role of LEDGF/p75. Am J Physiol, Cell Physiol. 2006;290(2):C554-66.
Takamura, Y., Fatma, N., Kubo, E., & Singh, D. P. (2006). Regulation of heavy subunit chain of gamma-glutamylcysteine synthetase by tumor necrosis factor-alpha in lens epithelial cells: role of LEDGF/p75. American Journal of Physiology. Cell Physiology, 290(2), C554-66.
Takamura Y, et al. Regulation of Heavy Subunit Chain of Gamma-glutamylcysteine Synthetase By Tumor Necrosis Factor-alpha in Lens Epithelial Cells: Role of LEDGF/p75. Am J Physiol, Cell Physiol. 2006;290(2):C554-66. PubMed PMID: 16403949.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Regulation of heavy subunit chain of gamma-glutamylcysteine synthetase by tumor necrosis factor-alpha in lens epithelial cells: role of LEDGF/p75. AU - Takamura,Yoshihiro, AU - Fatma,Nigar, AU - Kubo,Eri, AU - Singh,Dhirendra P, PY - 2006/1/13/pubmed PY - 2006/3/11/medline PY - 2006/1/13/entrez SP - C554 EP - 66 JF - American journal of physiology. Cell physiology JO - Am. J. Physiol., Cell Physiol. VL - 290 IS - 2 N2 - TNF-alpha induces oxidative stress by generating reactive oxygen species (ROS). This molecule elevates the expression of gamma-glutamylcysteine synthetase heavy subunit (gamma-GCS-HS). Lens epithelium-derived growth factor (LEDGF)/p75, a transcriptional protein, is inducible by oxidative stress and protects cells from various stresses by upregulating stress-responsive genes. This paper presents evidence that TNF-alpha elevates the expression of LEDGF and that LEDGF is one of the transactivators of gamma-GCS-HS gene. An analysis of the gamma-GCS-HS promoter sequence (-819 to +518 nt) revealed the presence of putative sites for LEDGF binding. Gel mobility assay confirmed the binding of LEDGF to the heat shock element (nGAAn) and the stress response element (A/TGGGGA/T) present in gamma-GCS-HS promoter. Transactivation experiments showed activation of gamma-GCS-HS promoter in cells overexpressing LEDGF or treated with a sublethal dose of TNF-alpha (20 ng/ml). Downregulation of gamma-GCS-HS promoter activity in cells transfected with LEDGF small interfering RNA validated the finding. Notably, cells treated with TNF-alpha (20 ng/ml) for 24 h had an increased abundance of LEDGF and gamma-GCS-HS mRNA and protein. In contrast, cells treated with TNF-alpha for longer periods or with higher concentrations of TNF-alpha showed reduced expression of LEDGF and gamma-GCS-HS and increased cellular death with higher ROS levels. Cells overexpressing LEDGF revealed elevated GSH levels (10-15%), a condition that may potentially eliminate the insult to cells induced by TNF-alpha. Thus TNF-alpha regulation of LEDGF may be physiologically important, as elevated expression of LEDGF increases the expression of endogenous gamma-GCS-HS gene, the catalytic subunit of the regulating enzyme in GSH biosynthesis that may constitute a protective mechanism in limiting oxidative stress induced by inflammatory cytokines. SN - 0363-6143 UR - https://www.unboundmedicine.com/medline/citation/16403949/Regulation_of_heavy_subunit_chain_of_gamma_glutamylcysteine_synthetase_by_tumor_necrosis_factor_alpha_in_lens_epithelial_cells:_role_of_LEDGF/p75_ L2 - http://www.physiology.org/doi/full/10.1152/ajpcell.00398.2005?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -