We investigated the expression pattern and underlying mechanism that controls hepatocyte growth factor (HGF) receptor (c-met) expression in normal kidney and a variety of kidney cells. Immunohistochemical staining showed widespread expression of c-met in mouse kidney, a pattern closely correlated with renal expression of Sp1 and Sp3 transcription factors. In vitro, all types of kidney cells tested expressed different levels of c-met, which was tightly proportional to the cellular abundances of Sp1 and Sp3. Both Sp1 and Sp3 bound to the multiple GC boxes in the promoter region of the c-met gene. Coimmunoprecipitation suggested a physical interaction between Sp1 and Sp3. Functionally, Sp1 markedly stimulated c-met promoter activity. Although Sp3 only weakly activated the c-met promoter, its combination with Sp1 synergistically stimulated c-met transcription. Conversely, deprivation of Sp proteins by transfection of decoy Sp1 oligonucleotide or blockade of Sp1 binding with mithramycin A inhibited c-met expression. The c-met receptor in all types of kidney cells was functional and induced protein kinase B/Akt phosphorylation in a distinctly dynamic pattern after HGF stimulation. These results indicate that members of the Sp family of transcription factors play an important role in regulating constitutive expression of the c-met gene in all types of renal cells. Our findings suggest that HGF may have a broader spectrum of target cells and possess wider implications in kidney structure and function than originally thought.
"Sp family members, Sp1–4, have been shown to play important roles during differentiation and development of human cells, as well as in cell cycle regulation. Sp1, Sp3 and Sp4 interact with several proteins involved in cell cycle regulation, such as E2F family members and retinoblastoma-like proteins (Rb and P130), as well as interacting with each other (e.g, Sp1 binds to both Sp3 and Sp4) (Karlseder et al., 1996; Rotheneder et al., 1999; Chang et al., 2001; Zhang et al., 2003). Thus the possibility exists that part of the ability of these factors (specifically Sp3 and Sp4) to enhance IE62-mediated transactivation may be due to their ability to recruit additional cellular factors involved in transcriptional activation. "
"As shown in Figure 2, c and d, c-met protein levels were significantly reduced in the kidneys lysates of Ksp-met−/−mice, compared with controls. Notably, renal c-met expression was not completely abolished because c-met is ubiquitously expressed in all kidney cells.11 Immunohistochemical staining also revealed a significant reduction of c-met protein in renal tubular epithelium of the Ksp-met−/−mice under cisplatin-stimulated conditions, compared to the controls (Figure 2, e and f). "
[Show abstract][Hide abstract] ABSTRACT: Hepatocyte growth factor is a pleiotrophic protein that promotes injury repair and regeneration in multiple organs. Here, we show that after acute kidney injury (AKI), the HGF receptor, c-met, was induced predominantly in renal tubular epithelium. To investigate the role of tubule-specific induction of c-met in AKI, we generated conditional knockout mice, in which the c-met gene was specifically disrupted in renal tubules. These Ksp-met(-/-) mice were phenotypically normal and had no appreciable defect in kidney morphology and function. However, in AKI induced by cisplatin or ischemia/reperfusion injury, the loss of tubular c-met substantially aggravated renal injury. Compared with controls, Ksp-met(-/-) mice displayed higher serum creatinine, more severe morphologic lesions, and increased apoptosis, which was accompanied by an increased expression of Bax and Fas ligand and decreased phosphorylation/activation of Akt. In addition, ablation of c-met in renal tubules promoted chemokine expression and renal inflammation after AKI. Consistently, ectopic expression of hepatocyte growth factor in vivo protected the kidneys against AKI in control mice, but not in Ksp-met(-/-) counterparts. Thus, our results suggest that tubule-specific c-met signaling is crucial in conferring renal protection after AKI, primarily by its anti-apoptotic and anti-inflammatory mechanisms.Kidney International advance online publication, 29 May 2013; doi:10.1038/ki.2013.102.
Kidney International 05/2013; 84(3). DOI:10.1038/ki.2013.102 · 8.56 Impact Factor
"Abbreviations used: ER␣, estrogen receptor ␣; FU, 5Ј-fluorouridine; HDAC, histone deacetylase. the nucleus of various cell types (Birnbaum et al., 1995; Pombo et al., 1998; Ross et al., 2002; Sapetschnig et al., 2002, 2004; Spann et al., 2002; Zhang et al., 2003; Spengler et al., 2005). However, no colocalization study of Sp1 and Sp3 in the same image has yet been performed. "
[Show abstract][Hide abstract] ABSTRACT: Sp1 and Sp3 are ubiquitously expressed mammalian transcription factors that activate or repress the expression of a variety of genes and are thought to compete for the same DNA binding site. We used indirect immunofluorescence microscopy and image deconvolution to show that Sp1 and Sp3 are organized into distinct nonoverlapping domains in human breast and ovarian cells. Domains of Sp1 and Sp3 infrequently associate with sites of transcription. Sp3 partitions with the tightly bound nuclear protein fraction of hormone responsive MCF-7 breast cancer cells, whereas only a subpopulation of Sp1 is found in that fraction. Both Sp1 and Sp3 are bound to the nuclear matrix, and the nuclear matrix-associated sites of Sp1 and Sp3 are different. Indirect immunofluorescence studies demonstrate that Sp1 and Sp3 associate with histone deacetylases 1 and 2 and with the estrogen receptor alpha, albeit at low frequencies in MCF-7 cells. Chromatin immunoprecipitation (ChIP) and re-ChIP assays revealed that although both Sp1 and Sp3 bind to the estrogen-responsive trefoil factor 1 promoter in MCF-7 cells, they do not occupy the same promoter. Our results demonstrate the different features of Sp1 and Sp3, providing further evidence that Sp3 is not a functional equivalent of Sp1.
Molecular Biology of the Cell 10/2005; 16(9):4073-83. DOI:10.1091/mbc.E05-05-0388 · 4.47 Impact Factor
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