Proteomic analysis glomeruli of PAN-treated rats

Podocytes are terminally differentiated cells at the kidney filtration barrier and exposed to considerable mechanical strain. Podocyte injury causes morphological changes as a result of cytoskeletal reorganizations and failure of the filtration barrier. The transcriptional co-activators YAP/TAZ are tightly controlled through hippo signaling and responsive to mechanical cues. Here, we show that YAP is upregulated upon podocyte injury to activate YAP-dependent target genes. This activation preceded the development of proteinuria. In contrast, similar perturbations of cells in culture did not reveal increased YAP activity but showed a downregulation of YAP/TAZ activity when cells were grown on stiff surface. However, culture of cells on soft matrix or inhibition of stress fiber formation allowed recapitulation of the damage-induced YAP upregulation indicating a mechanotransduction-dependent mechanism of YAP hyper-activity. Interestingly, increased expression of YAP targets was confirmed in renal biopsies from patients with glomerular disease. Consistently, pharmacological inhibition of YAP/TEAD activity ameliorated glomerular disease in vivo. These data suggest that perturbation of the mechanosensitive hippo signaling pathway may be a therapeutic principle in podocyte disease.