Y-box protein 1 mediates PDGF-B effects in mesangioproliferative glomerular disease

The pivotal role of PDGF-B for mesangioproliferative glomerular disease is well established. Here, Y-box protein-1 (YB-1) was identified as a downstream signaling target of PDGF-B. In healthy kidney cells, YB-1 was located predominantly within the nuclear compartment. Subsequent to PDGF-B infusion and in the course of anti-Thy1.1-induced mesangioproliferative glomerulonephritis, relocalization of YB-1 into the cytoplasm was observed. In experimental models that lack profound mesangial cell proliferation (e.g., Puromycin-nephrosis, passive Heyman nephritis, spontaneous normotensive nephrosclerosis, hyperlipidemic diabetic nephropathy), YB-1 remained nuclear. This translocation coincided with upregulation of YB-1 protein levels within the mesangial compartment. Increased YB-1 expression and subcellular shuttling was dependent on PDGF-B signaling via the mitogen-activated protein kinase pathway because these alterations were prevented by specific PDGF aptamers and the mitogen-activated protein kinase pathway inhibitor U0126. Furthermore, PDGF-B strongly induced YB-1 expression in vitro. This induction was important because RNAi-dependent knockdown of YB-1 abolished the mitogenic PDGF-B effect. Taken together, YB-1 seems to represent a specific and necessary PDGF-B target in mesangioproliferative glomerular disease.