ABSTRACT
Objecfive To investigate the change of V-ATPase B subunits on epithelial to mesenchymal transition (EMT)in rat renal tubular epithelial cells (NRK52E) stimulated by transforming growth factor β1 (TGF-β1). Methods NRK52E cells were stimulated by TGF-β1 (10 μg/L)for O h(control),12 h,24 h,48 h,72 h after sefrum-free culture for 24 h.The mRNA and protein expression of E-cadherin,α-SMA,B2 and B1 subunits of V-ATPase were detected by real-time PCR,Western blotting and immunofluorescence. Results After stimulated by TGF-β1 (10 μg/L)for 48 h,the expression of α-SMA was markedly increased(P<0.05),but the expression of E-cadherin was dramatically decreased(P<0.05).Meanwhile,the expressions of V-ATPase subunit B2 was significantly increased (P<0.05).However,the B1 subunit distributed rarely in NRK 52E cells,and did not increase after TGF-β1 stimulation.Double-label immunofluoerscence staining also showed that the V-ATPase B2 subunit was increased in the cytosol.tending to accumulate to the cell membrane after TGF-β1 stimulation. Conclusions The main isoform of V-ATPase distributed in NRK52E cells is B2 subunit.B2 subunit is increased alone with TGF-β1-induced EMT.It may suggest that V-ATPase B2 subunit may play a potential role in TGF-β1-induced tubular EMT and renal fibrosis.
ABSTRACT
By using differential display, we identified one of the genes encoding the multi-subunit complex protein V-ATPase, c subunit gene (ATP6L), and showed alterations of the gene expression by oxidative stresses. Expression of the ATP6L gene in Neuro-2A cells was increased by the treatment with H2O2 and incubation in hypoxic chamber, implying that the expression of the ATP6L gene is regulated by oxidative stresses. To examine mechanisms involved in the regulation of the gene expression by oxidative stresses, the transcriptional activity of the rat ATP6L promoter was studied. Transcription initiation site was determined by primer extension analysis and DNA sequencing, and promoter of the rat ATP6L and its deletion clones were constructed in reporter assay vector. Significant changes of the promoter activities in Neuro-2A cells were observed in two regions within the proximal 1 kbp promoter, and one containing a suppressor was in -195 to -220, which contains GC box that is activated by binding of Sp1 protein. The suppression of promoter activity was lost in mutants of the GC box. We confirmed by electrophoretic mobility shift and supershift assays that Sp1 protein specifically binds to the GC box. The promoter activity was not changed by the H2O2 treatment and incubation in hypoxic chamber, however, H2O2 increased the stability of ATP6L mRNA. These data suggest that the expression of the ATP6L gene by oxidative stresses is regulated at posttranscriptional level, whereas the GC box is important in basal activities of the promoter.