Yes-associated Protein Activation Research Articles

Pharmacological YAP activation promotes regenerative repair of cutaneous wounds

Chronic cutaneous wounds remain a persistent unmet medical need that decreases life expectancy and quality of life. Here, we report that topical application of PY-60, a small-molecule activator of the transcriptional coactivator Yes-associated protein (YAP), promotes regenerative repair of cutaneous wounds in pig and human models. Pharmacological YAP activation enacts a reversible pro-proliferative transcriptional program in keratinocytes and dermal cells that results in accelerated re-epithelization and regranulation of the wound bed. These results demonstrate that transient topical administration of a YAP activating agent may represent a generalizable therapeutic approach to treating cutaneous wounds.

Nuclear compression regulates YAP spatiotemporal fluctuations in living cells

Yes-associated protein (YAP) is a key mechanotransduction protein in diverse physiological and pathological processes; however, a ubiquitous YAP activity regulatory mechanism in living cells has remained elusive. Here, we show that YAP nuclear translocation is highly dynamic during cell movement and is driven by nuclear compression arising from cell contractile work. We resolve the mechanistic role of cytoskeletal contractility in nuclear compression by manipulation of nuclear mechanics. Disrupting the linker of nucleoskeleton and cytoskeleton complex reduces nuclear compression for a given contractility and correspondingly decreases YAP localization. Conversely, decreasing nuclear stiffness via silencing of lamin A/C increases nuclear compression and YAP nuclear localization. Finally, using osmotic pressure, we demonstrated that nuclear compression even without active myosin or filamentous actin regulates YAP localization. The relationship between nuclear compression and YAP localization captures a universal mechanism for YAP regulation with broad implications in health and biology.

TT-10 may elevate YAP and repair mouse uterine damage resulting from the inhibition effect of ibuprofen on COX2-PGE2 and YAP

Ibuprofen (IBU) is an emerging environmental contaminant that, in high doses, can damage reproductive organs in humans and other mammals. Recently, its effects on the uterus have been investigated. It is known that the COX2-PGE2 pathway and Yes-associated protein (YAP) are involved in female reproductive organ development and form a COX2-PGE2-EP2-Gas-β-catenin-YAP-COX2 positive feedback loop, in addition, TT-10, a pharmacological product, has been found to increase YAP. In this study, IBU was orally administrated to female mice for 7 d at doses of 0, 50, 100, and 200 mg/kg·bw/day (control, low, medium, and high doses, respectively). In addition, 0, 50, 100, and 200 μmol/L IBU was added in vitro to cultured uterine cells for 7 d at control, low, medium, and high doses, respectively; then, 0, 5, 10, and 20 μmol/L TT-10 were given to the in vitro uterine culture containing 100 μmol/L IBU to observe the effect of YAP activation. The results showed that medium and high doses of IBU inhibited the COX2-PGE2 pathway, decreasing YAP and increasing pYAP, leading to reduced circPVT1, elevated miR-149, and increased apoptosis, ultimately damaging the uterus. Conversely, 10 μmol/L TT-10 maximally enhanced YAP, which regulated COX2-PGE2 pathway activation, increased circPVT1, and decreased miR-149, and promoted cell proliferation, preventing uterine damage. This suggests that IBU may cause uterine damage by inhibiting the COX2-PGE2 pathway and YAP, and that appropriate doses of TT-10 may repair this damage by elevating YAP and stimulating COX2 via the feedback loop.

P-343 The role of Yes-Associated protein (YAP) activity in uterus adenogenesis process

Abstract Study question Could Yes-Associated protein(YAP) be effective in the adenogenesis process that occurs in the mouse uterus in the postnatal period? Summary answer It was observed that the YAP and phospho-YAP levels decreased in mice with inhibited gland development during adenogenesis process when compared to the control groups. What is known already The mouse uterus is composed of undifferentiated mesenchyme surrounded by a single layer of epithelium at birth. On the 5th Postnatal Day (PD), the luminal epithelium begins to bud, and the process called adenogenesis, which is termed as gland development in the uterus, begins. The gland development is evident on the PD 10th day. The uterus shows adult tissue characteristics by PD 15th-20th days. Although it has been stated that various signaling pathways are active in this process, Hippo signaling pathway role in the adenogenesis process have not been clarified yet. Study design, size, duration The uterus with normal gland development and gland development inhibited by Progesterone were evaluated for YAP and phospho-YAP, which is one of the main components of Hippo signaling pathway, by immunohistochemistry, western blotting, and q-RT-PCR methods. For experimental groups, 50 µg/g Progesterone was dissolved in 0.1 mL Sesame oil and for control groups, only 0.1 mL of Sesame oil given subcutaneously on PN 2nd-10th days. Animals were sacrificed on the PN 5th-10th and 15th days. Participants/materials, setting, methods In total of 30 newborn Balb/c female mice were used. They were divided as control (n = 15) and experimental(n = 15) groups. After the injections were finished, mice from both groups at PN5th(n = 5), PN10th(n = 5), and PN15th(n = 5) days were cervical dissociated, and uteri were collected. For immunohistochemical analyses, tissues were taken into buffered formalin, paraffin blocks were made, and the sections were taken. Protein and RNA isolations were performed from uteri for western blotting and q-RT-PCR analyses, respectively. Main results and the role of chance When YAP expression was evaluated by immunohistochemistry, western blotting and q-RT-PCR methods, there was no difference between the groups on the PN 5th day. But there was an active signaling was observed in the control groups on the PN10th day, which is very important for gland formation, and on the PN 15th day, that is effective in the maturation process. On the PN10th and 15th days, it was determined that YAP and phospho-YAP signal expression were decreased significantly in the experimental groups when compared with the control groups in immunohistochemically and protein levels. In addition, these findings were supported by mRNA analysis with YAP. Limitations, reasons for caution The study was performed in vivo mouse model. Further studies can be done with a transgenic animal model. Wider implications of the findings Considering the contribution of uterine gland development to the implantation process, errors in the development of these glands may cause infertility. This study can bring a new perspective to researching the uterus adenogenesis period and causes of infertility and treatment approaches. Trial registration number not applicable

YAP/WNT5A/FZD4 axis regulates osteogenic differentiation of human periodontal ligament cells under cyclic stretch.

To verify the role of YAP/WNT5A/FZD4 axis in stretch-induced osteogenic differentiation of hPDLCs. During orthodontic tooth movement, differentiation of human periodontal ligament cells (hPDLCs) at the tension side of the periodontal ligament mediates new bone formation. WNT5A promotes osteogenesis and its regulator Yes-associated protein (YAP) is responsive to mechanical stimulation in hPDLCs. However, the mechanisms of YAP and WNT5A in alveolar bone remodeling remain unclear. Cyclic stretch was applied to hPDLCs to mimic the orthodontic stretching force. Osteogenic differentiation was determined by alkaline phosphatase (ALP) activity, Alizarin Red staining, qRT-PCR and western blotting. To detect activation of YAP and expression of WNT5A and its receptor Frizzled-4 (FZD4), western blotting, immunofluorescence, qRT-PCR and ELISA were performed. Verteporfin, Lats-IN-1, small interfering RNAs and recombinant protein were used to explore the relationship of YAP, WNT5A and FZD4, and the effect of their relationship on stretch-induced osteogenesis of hPDLCs. WNT5A, FZD4 and nuclear localization of YAP were upregulated by cyclic stretch. YAP positively regulated WNT5A and FZD4 expression and osteogenic differentiation of hPDLCs under cyclic stretch by YAP inhibition or activation assay. Knockdown of WNT5A and FZD4 attenuated YAP-induced and stretch-induced osteogenic differentiation. Recombinant WNT5A rescued the suppressed osteogenic differentiation by YAP inhibitor in hPDLCs, whereas knockdown of FZD4 weakened the effect of WNT5A and amplified the suppression. WNT5A/FZD4 could be positively regulated by YAP and the YAP/WNT5A/FZD4 axis mediated osteogenic differentiation of hPDLCs under cyclic stretch. This study provided further insight into the biological mechanism of orthodontic tooth movement.

Lipid kinase PIP5Kα contributes to Hippo pathway activation via interaction with Merlin and by mediating plasma membrane targeting of LATS1

BackgroundThe Hippo pathway plays a critical role in controlled cell proliferation. The tumor suppressor Merlin and large tumor suppressor kinase 1 (LATS1) mediate activation of Hippo pathway, consequently inhibiting the primary effectors, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ). Phosphatidylinositol 4,5-bisphosphate (PIP2), a lipid present in the plasma membrane (PM), binds to and activates Merlin. Phosphatidylinositol 4-phosphate 5-kinase α (PIP5Kα) is an enzyme responsible for PIP2 production. However, the functional role of PIP5Kα in regulation of Merlin and LATS1 under Hippo signaling conditions remains unclear.MethodsPIP5Kα, Merlin, or LATS1 knockout or knockdown cells and transfected cells with them were used. LATS1, YAP, and TAZ activities were measured using biochemical methods and PIP2 levels were evaluated using cell imaging. Low/high cell density and serum starvation/stimulation conditions were tested. Colocalization of PIP5Kα and PIP2 with Merlin and LATS1, and their protein interactions were examined using transfection, confocal imaging, immunoprecipitation, western blotting, and/or pull-down experiments. Colony formation and adipocyte differentiation assays were performed.ResultsWe found that PIP5Kα induced LATS1 activation and YAP/TAZ inhibition in a kinase activity-dependent manner. Consistent with these findings, PIP5Kα suppressed cell proliferation and enhanced adipocyte differentiation of mesenchymal stem cells. Moreover, PIP5Kα protein stability and PIP2 levels were elevated at high cell density compared with those at low cell density, and both PIP2 and YAP phosphorylation levels initially declined, then recovered upon serum stimulation. Under these conditions, YAP/TAZ activity was aberrantly regulated by PIP5Kα deficiency. Mechanistically, either Merlin deficiency or LATS1 deficiency abrogated PIP5Kα-mediated YAP/TAZ inactivation. Additionally, the catalytic domain of PIP5Kα directly interacted with the band 4.1/ezrin/radixin/moesin domain of Merlin, and this interaction reinforced interaction of Merlin with LATS1. In accordance with these findings, PIP5Kα and PIP2 colocalized with Merlin and LATS1 in the PM. In PIP5Kα-deficient cells, Merlin colocalization with PIP2 was reduced, and LATS1 solubility increased.ConclusionsCollectively, our results support that PIP5Kα serves as an activator of the Hippo pathway through interaction and colocalization with Merlin, which promotes PIP2-dependent Merlin activation and induces local recruitment of LATS1 to the PIP2-rich PM and its activation, thereby negatively regulating YAP/TAZ activity.11kBwjrDVBy7xy7exwWkZdVideo

Insights into recent findings and clinical application of YAP and TAZ in cancer.

Decades of research have mapped out the basic mechanics of the Hippo pathway. The paralogues Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), as the central transcription control module of the Hippo pathway, have long been implicated in the progression of various human cancers. The current literature regarding oncogenic YAP and TAZ activities consists mostly of context-specific mechanisms and treatments of human cancers. Furthermore, a growing number of studies demonstrate tumour-suppressor functions of YAP and TAZ. In this Review we aim to synthesize an integrated perspective of the many disparate findings regarding YAP and TAZ in cancer. We then conclude with the various strategies for targeting and treating YAP- and TAZ-dependent cancers.

Activation of Piezo1 promotes osteogenic differentiation of aortic valve interstitial cell through YAP-dependent glutaminolysis.

Hemodynamic overload and dysregulation of cellular metabolism are involved in development of calcific aortic valve disease (CAVD). However, how mechanical stress relates to metabolic changes in CAVD remains unclear. Here, we show that Piezo1, a mechanosensitive ion channel, regulated glutaminase 1 (GLS1)-mediated glutaminolysis to promote osteogenic differentiation of valve interstitial cells (VICs). In vivo, two models of aortic valve stenosis were constructed by ascending aortic constriction (AAC) and direct wire injury (DWI). Inhibition of Piezo1 and GLS1 in these models respectively mitigated aortic valve lesion. In vitro, Piezo1 activation induced by Yoda1 and oscillatory stress triggered osteogenic responses in VICs, which were prevented by Piezo1 inhibition or knockdown. Mechanistically, Piezo1 activation promoted calcium-dependent Yes-associated protein (YAP) activation. YAP modulated GLS1-mediated glutaminolysis, which enhanced osteogenic differentiation through histone acetylation of runt-related transcription factor 2 (RUNX2) promoters. Together, our work provided a cross-talk between mechanotransduction and metabolism in the context of CAVD.

A novel protective role of lipoxin in inhibiting diabetic vascular calcification via YAP signalling: Health prevention and regulation

Vascular calcification is highly prevalent in diabetes patients, with detrimental consequences and no effective prevention and treatment strategies are currently available. Though the protective effect of lipoxin (LX) against vascular diseases has been demonstrated, its effect on diabetic vascular calcification remains unknown. AGEs dose-dependently induced calcification and the expression of osteogenesis-related markers, coupled with the activation of yes-associated protein (YAP). Mechanistically, YAP activation enhanced the AGE-induced osteogenic phenotype and calcification, but inhibition of YAP signalling alleviated this response. Further, an in vivo diabetic mouse model was established using a combination of a high-fat diet and multiple formulations of low-dose streptozotocin. Consistent with the in vitro results, diabetes promoted YAP expression and its subcellular localization in the nucleus in the arterial tunica media. The results demonstrate that LX attenuates the trans-differentiation and calcification of VSMCs in diabetes mellitus via YAP signalling, suggesting LX to be a potent therapeutic for preventing diabetic vascular calcification.

3D micropattern force triggers YAP nuclear entry by transport across nuclear pores and modulates stem cells paracrine.

Biophysical cues of the cellular microenvironment tremendously influence cell behavior by mechanotransduction. However, it is still unclear how cells sense and transduce the mechanical signals from 3D geometry to regulate cell function. Here, the mechanotransduction of human mesenchymal stem cells (MSCs) triggered by 3D micropatterns and its effect on the paracrine of MSCs are systematically investigated. Our findings show that 3D micropattern force could influence the spatial reorganization of the cytoskeleton, leading to different local forces which mediate nucleus alteration such as orientation, morphology, expression of Lamin A/C and chromatin condensation. Specifically, in the triangular prism and cuboid micropatterns, the ordered F-actin fibers are distributed over and fully transmit compressive forces to the nucleus, which results in nuclear flattening and stretching of nuclear pores, thus enhancing the nuclear import of YES-associated protein (YAP). Furthermore, the activation of YAP significantly enhances the paracrine of MSCs and upregulates the secretion of angiogenic growth factors. In contrast, the fewer compressive forces on the nucleus in cylinder and cube micropatterns cause less YAP entering the nucleus. The skin repair experiment provides the first in vivo evidence that enhanced MSCs paracrine by 3D geometry significantly promotes tissue regeneration. The current study contributes to understanding the in-depth mechanisms of mechanical signals affecting cell function and provides inspiration for innovative design of biomaterials.

Hippo (YAP)-autophagy axis protects against hepatic ischemia-reperfusion injury through JNK signaling.

Hepatic ischemia-reperfusion injury (HIRI) remains a common complication during liver transplantation (LT) in patients. As a key downstream effector of the Hippo pathway, Yes-associated protein (YAP) has been reported to be involved in various physiological and pathological processes. However, it remains elusive whether and how YAP may control autophagy activation during ischemia-reperfusion. Human liver tissues from patients who had undergone LT were obtained to evaluate the correlation between YAP and autophagy activation. Both an in vitro hepatocyte cell line and in vivo liver-specific YAP knockdown mice were used to establish the hepatic ischemia-reperfusion models to determine the role of YAP in the activation of autophagy and the mechanism of regulation. Autophagy was activated in the post-perfusion liver grafts during LT in patients, and the expression of YAP positively correlated with the autophagic level of hepatocytes. Liver-specific knockdown of YAP inhibited hepatocytes autophagy upon hypoxia-reoxygenation and HIRI ( P <0.05). YAP deficiency aggravated HIRI by promoting the apoptosis of hepatocytes both in the in vitro and in vivo models ( P <0.05). Attenuated HIRI by overexpression of YAP was diminished after the inhibition of autophagy with 3-methyladenine. In addition, inhibiting autophagy activation by YAP knockdown exacerbated mitochondrial damage through increasing reactive oxygen species ( P <0.05). Moreover, the regulation of autophagy by YAP during HIRI was mediated by AP1 (c-Jun) N-terminal kinase (JNK) signaling through binding to the transcriptional enhanced associate domain (TEAD). YAP protects against HIRI by inducing autophagy via JNK signaling that suppresses the apoptosis of hepatocytes. Targeting Hippo (YAP)-JNK-autophagy axis may provide a novel strategy for the prevention and treatment of HIRI.

Targeting the YAP/TAZ mechanotransducers in solid tumour therapeutics.

Targeting the YAP/TAZ mechanotransducers in solid tumour therapeutics.

Suppression of myeloid YAP antagonizes adverse cardiac remodeling during pressure overload stress

Inflammation is an integral component of cardiovascular disease and is thought to contribute to cardiac dysfunction and heart failure. While ischemia-induced inflammation has been extensively studied in the heart, relatively less is known regarding cardiac inflammation during non-ischemic stress. Recent work has implicated a role for Yes-associated protein (YAP) in modulating inflammation in response to ischemic injury; however, whether YAP influences inflammation in the heart during non-ischemic stress is not described. We hypothesized that YAP mediates a pro-inflammatory response during pressure overload (PO)-induced non-ischemic injury, and that targeted YAP inhibition in the myeloid compartment is cardioprotective. In mice, PO elicited myeloid YAP activation, and myeloid-specific YAP knockout mice (YAPF/F;LysMCre) subjected to PO stress had better systolic function, and attenuated pathological remodeling compared to control mice. Inflammatory indicators were also significantly attenuated, while pro-resolving genes including Vegfa were enhanced, in the myocardium, and in isolated macrophages, of myeloid YAP KO mice after PO. Experiments using bone marrow-derived macrophages (BMDMs) from YAP KO and control mice demonstrated that YAP suppression shifted polarization toward a resolving phenotype. We also observed attenuated NLRP3 inflammasome priming and function in YAP deficient BMDMs, as well as in myeloid YAP KO hearts following PO, indicating disruption of inflammasome induction. Finally, we leveraged nanoparticle-mediated delivery of the YAP inhibitor verteporfin and observed attenuated PO-induced pathological remodeling compared to DMSO nanoparticle control treatment. These data implicate myeloid YAP as an important molecular nodal point that facilitates cardiac inflammation and fibrosis during PO stress and suggest that selective inhibition of YAP may prove a novel therapeutic target in non-ischemic heart disease.

Moderate mechanical stimulation antagonizes inflammation of annulus fibrosus cells through YAP-mediated suppression of NF-κB signaling.

Intervertebral disc degeneration (IDD) is a leading cause of low back pain. The inflammatory responses caused by aberrant mechanical loading are one of the major factors leading to annulus fibrosus (AF) degeneration and IDD. Previous studies have suggested that moderate cyclic tensile strain (CTS) can regulate anti-inflammatory activities of AF cells (AFCs), and Yes-associated protein (YAP) as a mechanosensitive coactivator senses diverse types of biomechanical stimuli and translates them into biochemical signals controlling cell behaviors. However, it remains poorly understood whether and how YAP mediates the effect of mechanical stimuli on AFCs. In this study, we aimed to investigate the exact effects of different CTS on AFCs as well as the role of YAP signaling involving in it. Our results found that 5% CTS inhibited the inflammatory response and promoted cell growth through inhibiting the phosphorylation of YAP and nuclear localization of NF-κB, while 12% CTS had a significant proinflammatory effect with the inactivation of YAP activity and the activation of NF-κB signaling in AFCs. Furthermore, moderate mechanical stimulation may alleviate the inflammatory reaction of intervertebral discs through YAP-mediated suppression of NF-κB signaling in vivo. Therefore, moderate mechanical stimulation may serve as a promising therapeutic approach for the prevention and treatment of IDD.

Extracellular vesicles in fatty liver promote a metastatic tumor microenvironment

Liver metastasis is a major cause of death in patients with colorectal cancer (CRC). Fatty liver promotes liver metastasis, but the underlying mechanism remains unclear. We demonstrated that hepatocyte-derived extracellular vesicles (EVs) in fatty liver enhanced the progression of CRC liver metastasis by promoting oncogenic Yes-associated protein (YAP) signaling and an immunosuppressive microenvironment. Fatty liver upregulated Rab27a expression, which facilitated EV production from hepatocytes. In the liver, these EVs transferred YAP signaling-regulating microRNAs to cancer cells to augment YAP activity by suppressing LATS2. Increased YAP activity in CRC liver metastasis with fatty liver promoted cancer cell growth and an immunosuppressive microenvironment by M2 macrophage infiltration through CYR61 production. Patients with CRC liver metastasis and fatty liver had elevated nuclear YAP expression, CYR61 expression, and M2 macrophage infiltration. Our data indicate that fatty liver-induced EV-microRNAs, YAP signaling, and an immunosuppressive microenvironment promote the growth of CRC liver metastasis.

Epstein–Barr virus LMP1 protein promotes proliferation and inhibits differentiation of epithelial cells via activation of YAP and TAZ

Latent Epstein-Barr virus (EBV) infection promotes undifferentiated nasopharyngeal carcinomas (NPCs) in humans, but the mechanism(s) for this effect has been difficult to study because EBV cannot transform normal epithelial cells invitro and the EBV genome is often lost when NPC cells are grown in culture. Here we show that the latent EBV protein, LMP1 (Latent membrane protein 1), induces cellular proliferation and inhibits spontaneous differentiation of telomerase-immortalized normal oral keratinocytes (NOKs) in growth factor-deficient conditions by increasing the activity of the Hippo pathway effectors, YAP (Yes-associated protein) and TAZ (Transcriptional coactivator with PDZ-binding motif). We demonstrate that LMP1 enhances YAP and TAZ activity in NOKs both by decreasing Hippo pathway-mediated serine phosphorylation of YAP and TAZ and increasing Src kinase-mediated Y357 phosphorylation of YAP. Furthermore, knockdown of YAP and TAZ is sufficient to reduce proliferation and promote differentiation in EBV-infected NOKs. We find that YAP and TAZ are also required for LMP1-induced epithelial-to-mesenchymal transition. Importantly, we demonstrate that ibrutinib (an FDA-approved BTK inhibitor that blocks YAP and TAZ activity through an off-target effect) restores spontaneous differentiation and inhibits proliferation of EBV-infected NOKs at clinically relevant doses. These results suggest that LMP1-induced YAP and TAZ activity contributes to the development of NPC.

Statins improve endothelial function via suppression of epigenetic-driven EndMT.

The pleiotropic benefits of statins in cardiovascular diseases that are independent of their lipid-lowering effects have been well documented, but the underlying mechanisms remain elusive. Here we show that simvastatin significantly improves human induced pluripotent stem cell-derived endothelial cell functions in both baseline and diabetic conditions by reducing chromatin accessibility at transcriptional enhanced associate domain elements and ultimately at endothelial-to-mesenchymal transition (EndMT)-regulating genes in a yes-associated protein (YAP)-dependent manner. Inhibition of geranylgeranyltransferase (GGTase) I, a mevalonate pathway intermediate, repressed YAP nuclear translocation and YAP activity via RhoA signaling antagonism. We further identified a previously undescribed SOX9 enhancer downstream of statin-YAP signaling that promotes the EndMT process. Thus, inhibition of any component of the GGTase-RhoA-YAP-SRY box transcription factor 9 (SOX9) signaling axis was shown to rescue EndMT-associated endothelial dysfunction both in vitro and in vivo, especially under diabetic conditions. Overall, our study reveals an epigenetic modulatory role for simvastatin in repressing EndMT to confer protection against endothelial dysfunction.

Acyl-CoA thioesterase 12 suppresses YAP-mediated hepatocarcinogenesis by limiting glycerolipid biosynthesis

Cancer cells use acetate to support the higher demand for energy and lipid biosynthesis during uncontrolled cell proliferation, as well as for acetylation of regulatory proteins. Acyl-CoA thioesterase 12 (Acot12) is the enzyme that hydrolyzes acetyl-CoA to acetate in liver cytosol and is downregulated in hepatocellular carcinoma (HCC). A mechanistic role for Acot12 in hepatocarcinogenesis was assessed in mice in response to treatment with diethylnitrosamine(DEN)/carbon tetrachloride (CCl4) administration or prolonged feeding of a diet that promotes non-alcoholic steatohepatitis (NASH). Relative to controls, Acot12−/− mice exhibited accelerated liver tumor formation that was characterized by the hepatic accumulation of glycerolipids, including lysophosphatidic acid (LPA), and that was associated with reduced Hippo signaling and increased yes-associated protein (YAP)-mediated transcriptional activity. In Acot12−/− mice, restoration of hepatic Acot12 expression inhibited hepatocarcinogenesis and YAP activation, as did knockdown of hepatic YAP expression. Excess LPA produced due to deletion of Acot12 signaled through LPA receptors (LPARs) coupled to Gα12/13 subunits to suppress YAP phosphorylation, thereby promoting its nuclear localization and transcriptional activity. These findings identify a protective role for Acot12 in suppressing hepatocarcinogenesis by limiting biosynthesis of glycerolipids including LPA, which preserves Hippo signaling.

YAP promotes AP-1 expression in tubular epithelial cells in the kidney.

Chronic kidney disease (CKD) is a major health problem. Kidney fibrosis is a hallmark and final common pathway of CKD. The Hippo/yes-associated protein (YAP) pathway regulates organ size, inflammation, and tumorigenesis. Our previous study demonstrated tubular YAP activation by tubule-specific double knockout of mammalian STE20-like protein kinase 1/2 (Mst1/2) induced CKD in mice, but the underlying mechanisms remain to be fully elucidated. Activator protein (AP)-1 activation was found to promote tubular atrophy and tubulointerstitial fibrosis. Therefore, we studied whether YAP regulates AP-1 expression in the kidney. We found that expression of various AP-1 components was induced in kidneys subjected to unilateral ureteric obstruction and in Mst1/2 double knockout kidneys, and these inductions were blocked by deletion of Yap in tubular cells, with Fosl1 being most affected compared with other AP-1 genes. Inhibition of Yap also most highly suppressed Fosl1 expression among AP-1 genes in HK-2 and IMCD3 renal tubular cells. YAP bound to the Fosl1 promoter and promoted Fosl1 promoter-luciferase activity. Our results suggest that YAP controls AP-1 expression and that Fosl1 is the primary target of YAP in renal tubular cells.NEW & NOTEWORTHY Yes-associated protein (YAP) activation leads to tubular injury, renal inflammation, and fibrosis, but the underlying mechanisms are not fully understood. We now provide genetic evidence that YAP promotes activator protein-1 expression and that Fosl1 is the primary target of YAP in renal tubular cells.

Low-Intensity Pulsed Ultrasound Attenuates Periodontal Ligament Cells Apoptosis by Activating Yes-Associated Protein-Regulated Autophagy

The goal of the work described here was to determine if low-intensity pulsed ultrasound (LIPUS) has an anti-inflammatory effect on lipopolysaccharide (LPS)-induced inflammation in periodontal ligament cells (PDLCs). The mechanism underlying this effect remains to be explored and is likely related to PDLC apoptosis regulated by Yes-associated protein (YAP) and autophagy. To verify this hypothesis, we used a rat model of periodontitis and primary human PDLCs. We examined alveolar bone resorption in rats and apoptosis, autophagy and YAP activity in LPS-treated PDLCs with and without application of LIPUS by cellular immunofluorescence, transmission electron microscopy and Western blotting. Then, siRNA transfection was used to decrease YAP expression to confirm the regulatory role of YAP in the anti-apoptotic effect of LIPUS on PDLCs. We found that LIPUS attenuated alveolar bone resorption in rats and this was accompanied by YAP activation. LIPUS inhibited hPDLC apoptosis by YAP activation, and promoted autophagic degradation to help autophagy completion. These effects were reversed after YAP expression was blocked. LIPUS attenuates PDLC apoptosis by activating Yes-associated protein-regulated autophagy.