Extracellular YB-1 blockade in experimental nephritis upregulates Notch-3 receptor expression and signaling.

BACKGROUND

Notch receptors are involved in kidney development and pathogenesis of inflammatory glomerular diseases. Given the secretion of Y-box (YB) protein-1 following cytokine stimulation and subsequent extracellular association with membrane receptor Notch-3 in vitro, we elucidated functional effects of YB-1 targeting on the Notch-3 signaling pathway.

METHODS

Rat mesangial cells were challenged with a monoclonal anti-YB-1 antibody (YB-1-mAb) and analyzed for YB-1 and Notch-3 expression. Notch-3 expression in mice with a targeted disruption of one YB-1 allele (YB-1(+/d)) was compared with their wild-type littermates. Furthermore, YB-1-mAb was applied during mesangioproliferative anti-Thy1.1 nephritis, and glomerular Notch-3, Notch target genes and YB-1 expression were analyzed by immunohistochemistry, quantitative real-time PCR and immunoblotting.

RESULTS

Upon challenge with YB-1-mAb, rat mesangial cells showed an increased expression of YB-1 and Notch-3 protein. Concordantly, we found a significant upregulation of Notch-3 expression in renal cells of YB-1(+/d) mice. YB-1-mAb treatment in anti-Thy1.1 nephritis resulted in enhanced mesangial Notch-3 expression and differential Notch target gene activation (HES2/Hey-2). Notably, YB-1 mRNA content did not differ between groups; however, glomerular YB-1 protein was significantly increased, suggesting a posttranslational mechanism.

CONCLUSION

Extracellular targeting of YB-1 potently induces glomerular Notch-3 receptor expression, Notch signaling and YB-1 stabilization, most likely via an autoregulatory feedback mechanism.