Transcription factor β-catenin plays a key role in fluid flow shear stress-mediated glomerular injury in solitary kidney

Abstract

Increased fluid flow shear stress (FFSS) in solitary kidney alters podocyte function in vivo. FFSS-treated cultured podocytes show upregulated AKT-GSK3β-β-catenin signaling. The present study was undertaken to confirm (i) the activation of β-catenin signaling in podocytes in vivo using unilaterally nephrectomized (UNX) TOPGAL mice with the β-galactosidase reporter gene for β-catenin activation, (ii) β-catenin translocation in FFSS-treated mouse podocytes, and (iii) β-catenin signaling using publicly available data from UNX mice. The UNX of TOPGAL mice resulted in glomerular hypertrophy and increased the mesangial matrix consistent with hemodynamic adapta-tion. Uninephrectomized TOPGAL mice showed an increased β-galactosidase expression at 4 weeks but not at 12 weeks, as assessed using immunofluorescence microscopy (p < 0.001 at 4 weeks; p = 0.16 at 12 weeks) and X-gal staining (p = 0.008 at 4 weeks; p = 0.65 at 12 weeks). Immunofluorescence microscopy showed a significant increase in phospho-β-catenin (Ser552, p = 0.005) at 4 weeks but not at 12 weeks (p = 0.935) following UNX, and the levels of phospho-β-catenin (Ser675) did not change. In vitro FFSS caused a sustained increase in the nuclear translocation of phospho-β-catenin (Ser552) but not phospho-β-catenin (Ser675) in podocytes. The bioinformatic analysis of the GEO dataset, #GSE53996, also identified β-catenin as a key upstream regulator. We conclude that transcription factor β-catenin mediates FFSS-induced podocyte (glomerular) injury in solitary kidney.