YAP-mediated mechanotransduction determines the podocyte’s response to damage

Abstract

Podocytes are terminally differentiated cells of the kidney filtration barrier. They are subjected to physiological filtration pressure and considerable mechanical strain, which can be further increased in various kidney diseases. When injury causes cytoskeletal reorganization and morphological alterations of these cells, the filtration barrier may become compromised and allow proteins to leak into the urine (a condition called proteinuria). Using time-resolved proteomics, we showed that podocyte injury stimulated the activity of the transcriptional coactivator YAP and the expression of YAP target genes in a rat model of glomerular disease before the development of proteinuria. Although the activities of YAP and its ortholog TAZ are activated by mechanical stress in most cell types, injury reduced YAP and TAZ activity in cultured human and mouse podocyte cell lines grown on stiff substrates. Culturing these cells on soft matrix or inhibiting stress fiber formation recapitulated the damage-induced YAP up-regulation observed in vivo, indicating a mechanotransduction-dependent mechanism of YAP activation in podocytes. YAP overexpression in cultured podocytes increased the abundance of extracellular matrix-related proteins that can contribute to fibrosis. YAP activity was increased in mouse models of diabetic nephropathy, and the YAP target was highly expressed in renal biopsies from glomerular disease patients. Although overexpression of human YAP in mice induced mild proteinuria, pharmacological inhibition of the interaction between YAP and its partner TEAD in rats ameliorated glomerular disease and reduced damage-induced mechanosignaling in the glomeruli. Thus, perturbation of YAP-dependent mechanosignaling is a potential therapeutic target for treating some glomerular diseases.

FAK controls the mechanical activation of YAP, a transcriptional regulator required for durotaxis

“…Furthermore, mRNA expression of CTGF in active myrFAK HSCs is 50% higher than in Y397FAK for both 4 and 25 kPa substrate rigidities. Changes in expression of CTGF have been observed in response to alterations in stiffness in other cell types to a similar extent (5, 25, 26). The observed YAP nuclear localization correlates with the high CTGF expression in myrFAK cells and with the low expression in Y397FAK cells (Fig.…”

Protein half‐life determines expression of proteostatic networks in podocyte differentiation

“…MS-based proteomics allows the development of comprehensive and detailed maps of protein expression by various cell types (74,75), including podocytes (76). In fact, these analyses revealed that podocyte proteins are strongly subjected to posttranslational modifications, including phosphorylation (9,(77)(78)(79), ubiquitination (70), and proteolytic processing (66), and undergo rapid proteome remodeling when injured (5). Previously, we reported that podocyte differentiation markedly reduces proteasomal activity (9), and podocyte injury increases proteasome expression and activity (80).…”

“…A significant fraction of disorders affect the podocytes resulting in an altered actinbased cytoskeleton and disturbed cellular polarity (1). Podocyte cell culture models represent widely used tools in glomerular research (2,3) as environmental cues and gene and protein expression can be easily manipulated in vitro for mechanistic analyses (4,5).…”

Angiotensin II regulates phosphorylation of actin‐associated proteins in human podocytes

“…LCP1 expression is not over-represented in podocytes and seemed to be low (57,58); however, a low expression level does not exclude an important role in the regulation or modulation of AngIIdependent actin cytoskeleton rearrangements in podocytes. In this context, it is of special interest that podocytes not only express LCP but also T-plastin; therefore, it will be interesting to investigate whether the expression of both plastins and/or the phosphorylation of LCP1 is increased during podocyte injury.…”