The Fli-1 Transcription Factor Regulates the Expression of CCL5/RANTES

Abstract

The Fli-1 transcription factor, an Ets family member, is implicated in the pathogenesis of systemic lupus erythematosus (SLE) in human patients and murine models of lupus. Lupus-prone mice with reduced Fli-1 expression have significantly less nephritis, prolonged survival and decreased infiltrating inflammatory cells into the kidney. Inflammatory chemokines, including CCL5, are critical for attracting inflammatory cells. In this study, decreased CCL5 mRNA expression was observed in kidneys of lupus prone NZM2410 mice, with reduced Fli-1 expression. CCL5 protein expression was significantly decreased in endothelial cells transfected with Fli-1 specific siRNA compared to controls. Fli-1 binds to endogenous Ets binding sites in the distal region of the CCL5 promoter. Transient transfection assays demonstrate that Fli-1 drives transcription from the CCL5 promoter in a dose-dependent manner. Both Ets1, another Ets family member, and Fli-1 drive transcription from the CCL5 promoter, although Fli-1 transactivation was significantly stronger. Ets1 acts as a dominant negative transcription factor to Fli-1, indicating that they may have at least one DNA binding site in common. Systematic deletion of DNA binding sites demonstrates the importance of the sites located within a 225bp region of the promoter. Mutation of the Fli-1 DNA binding domain significantly reduces transactivation of the CCL5 promoter by Fli-1. We have identified a novel regulator of transcription for CCL5. These results suggest that Fli-1 is a novel and critical regulator of proinflammatory chemokines and affects the pathogenesis of disease through the regulation of factors that recruit inflammatory cells to sites of inflammation.

Acetylation impacts Fli‐1‐driven regulation of granulocyte colony stimulating factor

“…In previous reports, we have demonstrated that a decrease of Fli‐1 in endothelial cells results in a significant reduction of expression levels, both mRNA and protein, of several inflammatory mediators . G‐CSF plays a role in the regulation of neutrophils and in patients with SLE a subset of the neutrophil population expresses increased inflammatory cytokines and cytotoxicity of endothelial cells .…”

“…Mutation of the third tryptophan abolishes DNA binding of Ets1 to the enhancer within Maloney sarcoma virus and mutation of this conserved amino acid abolishes binding of Fli‐1 to the Ets binding domain and reduces activity within the collagen α2(I) promoter . Increasing evidence has demonstrated that the Fli‐1 transcription factor is a key regulator of a number of inflammatory cytokines and chemokines , suggesting that Fli‐1 may be more important in inflammation than previously recognized. A critical role for Fli‐1 was demonstrated in the pathogenesis of SLE and the development of lupus nephritis .…”

FLI1 Levels Impact CXCR3 Expression and Renal Infiltration of T Cells and Renal Glycosphingolipid Metabolism in the MRL/lpr Lupus Mouse Strain

“…MRL/lpr Fli1 +/+ immune cells, including T cells, do not readily migrate to the kidney when transferred into MRL/lpr Fli1 +/− mice (10). Chemokines Ccl2 ( Mcp-1 ), Ccl3 ( Mip-1α ), Ccl4 ( Mip-1β ) and Ccl5 ( Rantes ) are significantly decreased at the message level in the kidneys of MRL/lpr Fli1 +/− compared to Fli1 +/+ mice and FLI1 was demonstrated to regulate the promoter activity of several different cytokine genes in endothelial cells (8, 9, 12, 13). Here we demonstrated that the expression Cxcl9 and Cxcl10 , CXCR3 ligands, also are significantly decreased in the kidneys of MRL/lpr Fli1 +/− compared to the Fli1 +/+ mice.…”

“…The putative ETS sites in hCXCR3 tested for FLI1 binding were chosen based on numerous studies, including some from our laboratory, demonstrating that FLI1 binds and acts through conserved canonical ETS sites that are more proximal to the transcription start site (9, 12, 17, 34–41). However, we recently demonstrated that FLI1 also can regulate promoters through more distal sites (12, 13). Alternatively, FLI1 may indirectly regulate Cxcr3 transcription.…”

“…NZM2410 mice with reduced FLI1 levels ( Fli1 +/− ) were shown to have decreased numbers of renal infiltrating inflammatory cells (11). Recent studies demonstrated that FLI1 regulates the expression of MCP-1, RANTES and IL-6 (9, 12, 13). Together, these studies suggest that globally reducing FLI1 levels in lupus mouse strains improves disease by decreasing renal chemokine production and thus, inflammatory infiltration.…”