Aberrant activation, nuclear localization, and phosphorylation of yes-associated protein-1 in the embryonic kidney and Wilms tumor

Abstract

Background The Yes-associated-protein-1 (YAP1) is a novel, direct regulator of stem cell genes both in development and cancer. FAT4 is an upstream regulator that induces YAP1 cytosolic sequestering by phosphorylation (p-Ser 127) and therefore inhibits YAP1-dependent cellular proliferation. We hypothesized that loss of FAT4 signaling would result in expansion of the nephron progenitor population in kidney development and that YAP1 subcellular localization would be dysregulated in Wilms tumor (WT), an embryonal malignancy that retains gene expression profiles and histologic features reminiscent of the embryonic kidney. Methods Fetal kidneys from Fat4−/− mice were harvested at e18.5 and markers of nephron progenitors were investigated using immunohistochemical analysis. To examine YAP1 subcellular localization in WT, a primary WT cell line (VUWT30) was analyzed by immunofluorescence. Forty WT specimens evenly distributed between favorable and unfavorable histology (n = 20 each), and treatment failure or success (n = 20 each) was analyzed for total and phosphorylated YAP1 using immunohistochemistry and Western blot. Results Fat4−/− mouse fetal kidneys exhibit nuclear YAP1 with increased proliferation and expansion of nephron progenitor cells. In contrast to kidney development, subcellular localization of YAP1 is dysregulated in WT, with a preponderance of nuclear p-YAP1. By Western blot, median p-YAP1 quantity was 5.2-fold greater in unfavorable histology WT (P = 0.05). Conclusions Fetal kidneys in Fat4−/− mice exhibit a phenotype reminiscent of nephrogenic rests, a WT precursor lesion. In WT, YAP1 subcellular localization is dysregulated and p-YAP1 accumulation is a novel biomarker of unfavorable histology.

Fat4 suppression induces Yap translocation accounting for the promoted proliferation and migration of gastric cancer cells

“…Based on previous studies, 6,17 we predicted that the decreased ratio of p-Yap/Yap may be due to the nuclear translocation of Yap from the cytoplasm in GC cells. We therefore extracted cytoplasmic proteins and nuclear proteins from GC cell lysates, and assessed the expression levels of Fat4, p-Yap and total Yap.…”

“…Whereas these phenotypes may be ascribed to the aberrant ratios of p-Yap/Yap and p-LATS1/LATS1, the underlying pathways dysregulated in GC remain unclear, although Fat4 commonly regulates tissue development via the Hippo pathway. [5][6][7] In order to further understand the mechanism by which Fat4 regulates GC cell proliferation and migration, we investigated the Hippo signaling pathway and interrelated critical elements.…”

“…5 Therefore further studies investigating the regulatory mechanisms between Fat4 and the Hippo pathway are necessary. Fat4 plays a critical role in tissue development, for example the kidney, 6 by modulating Yap and modifying Wnt9b/b-catenin thereby regulating the differentiation of progenitors and renewal program of the kidney. 7 In addition, Fat4 interacts with PCP pathway proteins and disrupts oriented cell division, leading to dysfunction of multiple organs including the renal cyst, neural tube and inner ear.…”

“…18 Mutations in Fat4 are considered as a major cause of reduced expression, and lead to the aberrant activation of Yap and its translocation into the nucleus. 6,17 Intriguingly, cytoplasmic Yap was reported to suppress Wnt/b-catenin signaling via binding and preventing b-catenin nuclear translocation. 19 In the contrast, however, Rosenbluh and colleagues 20 found that Yap1 exists in a complex with b-catenin sustaining the survival and transformation of b-catenin dependent cancers.…”

The nuclear lamina is mechano-responsive to ECM elasticity in mature tissue

“…on A-type lamins or emerin; Ho et al, 2013;Swift et al, 2013b) or, conceivably, by protein modifications (e.g. YAP1 nuclear localization can be stimulated by phosphorylation of the protein; Murphy et al, 2014). Additionally, transient breakdown of the nuclear envelope in laminopathic cells, perhaps as a consequence of a reduced robustness under conditions of mechanical stress, has been shown to allow the ingress of transcription factors such as RelA (De Vos et al, 2011).…”