Project description:Endothelial cells (ECs) are constantly exposed to mechanical forces in the form of fluid shear stress, extracellular stiffness, and cyclic strain. How mechanical forces are transduced to the nucleus to drive transcriptional reprogramming in ECs is poorly understood. The mechanoresponsive activity of Yes associated protein (YAP) and its role in vascular development are well described, however, whether changes to transcription or epigenetic regulation of YAP are involved in these processes remains unanswered. Our results reveal that mechanical forces sensed at cell-cell junctions by the YAP target gene, Angiomotin-like 2 (AmotL2), are directly intervened into changes in global chromatin accessibility and EZH2 activity leading to modulation of YAP-promotor activity. Functionally, shear stress induced proliferation of ECs in vivo were reliant on AmotL2 and YAP/TAZ endothelial expression. Mechanistically, uncoupling of the nuclear-cytoskeletal connection from junctions and focal adhesions led to altered nuclear morphology, chromatin accessibility and suppression of YAP-promotor activity. Our findings reveal a role for AmotL2 and nuclear-cytoskeletal force transmission in modulating the epigenetic and transcriptional regulation of YAP to maintain a mechanoenforced positive-feedback loop of vascular homeostasis.
Project description:BackgroundEndothelial cells are constantly exposed to mechanical forces in the form of fluid shear stress, extracellular stiffness, and cyclic strain. The mechanoresponsive activity of YAP (Yes-associated protein) and its role in vascular development are well described; however, whether changes to transcription or epigenetic regulation of YAP are involved in these processes remains unanswered. Furthermore, how mechanical forces are transduced to the nucleus to drive transcriptional reprogramming in endothelial cells is poorly understood. The YAP target gene, AmotL2 (angiomotin-like 2), is a junctional mechanotransducer that connects cell-cell junctions to the nuclear membrane via the actin cytoskeleton.MethodsWe applied mechanical manipulations including shear flow, stretching, and substrate stiffness to endothelial cells to investigate the role of mechanical forces in modulating YAP transcription. Using in vitro and in vivo endothelial depletion of AmotL2, we assess nuclear morphology, chromatin organization (using transposase-accessible chromatin sequencing), and whole-mount immunofluorescent staining of the aorta to determine the regulation and functionality of YAP. Finally, we use genetic and chemical inhibition to uncouple the nuclear-cytoskeletal connection to investigate the role of this pathway on YAP transcription.ResultsOur results reveal that mechanical forces sensed at cell-cell junctions by the YAP target gene AmotL2 are directly involved in changes in global chromatin accessibility and activity of the histone methyltransferase EZH2, leading to modulation of YAP promotor activity. Functionally, shear stress-induced proliferation of endothelial cells in vivo was reliant on AmotL2 and YAP/TAZ (transcriptional coactivator with PDZ-binding motif) expression. Mechanistically, uncoupling of the nuclear-cytoskeletal connection from junctions and focal adhesions led to altered nuclear morphology, chromatin accessibility, and YAP promotor activity.ConclusionsOur findings reveal a role for AmotL2 and nuclear-cytoskeletal force transmission in modulating the epigenetic and transcriptional regulation of YAP to maintain a mechano-enforced positive feedback loop of vascular homeostasis. These findings may offer an explanation as to the proinflammatory phenotype that leads to aneurysm formation observed in AmotL2 endothelial deletion models.
Project description: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 over-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.
Project description:We report that loss of CCM3/PDCD10 in fibroblasts induces FAK/Src-paxillin signalling driving actomyosin-dependent mechanotransduction leading to YAP/TAZ signalling. In vivo, loss of CCM3 in fibroblasts drives excessive tissue remodelling leading to the dissemination of breast cancer cells to distant organs.
Project description:The transcriptional regulator YAP orchestrates important cell functions, determining tissue homeostasis, organ growth control, and tumorigenesis. Mechanical stimuli are a key input to YAP activity, but the mechanisms controlling this regulation remain largely uncharacterized. We show that CAV1 positively modulates the YAP mechanoresponse to substrate stiffness through actin cytoskeleton-dependent and Hippo kinase-independent mechanisms. RHO activity is necessary but not sufficient for CAV1-dependent mechanoregulation of YAP activity. Systematic quantitative interactomic studies and image-based siRNA screenings provide evidence that this actin-dependent regulation is determined by YAP interaction with the 14-3-3 protein YWHAH. Constitutive YAP activation rescued phenotypes associated with CAV1 loss, including defective ECM remodeling. CAV1-mediated control of YAP activity was validated in vivo in a model of pancreatitis-driven acinar-to-ductal metaplasia. We propose that this CAV1-YAP mechanotransduction system controls a significant share of cell programs linked to these two pivotal regulators, with potentially broad physiological and pathological implications.
Project description:Angiogenesis, the process by which endothelial cells (ECs) form new blood vessels from existing ones, is intimately linked to the tissue's metabolic milieu and often occurs at nutrient-deficient sites. However, ECs rely on sufficient metabolic resources to support growth and proliferation. How endothelial nutrient acquisition and usage are regulated is unknown. Here we show that these processes are dictated by YAP/TAZ-TEAD – a transcriptional module whose function is highly responsive to changes in the tissue environment. ECs lacking YAP/TAZ or their transcriptional partners, TEAD1, 2, and 4 fail to divide, resulting in stunted vascular growth in mice. Conversely, activation of TAZ, the more abundant paralogue in ECs, boosts proliferation, leading to vascular hyperplasia. We find that YAP/TAZ promote angiogenesis by fueling nutrient mTORC1 signaling. By orchestrating the transcription of a repertoire of cell-surface transporters, YAP/TAZ-TEAD stimulate the import of amino acids and other essential nutrients, thereby enabling mTORC1 pathway activation. Dissociating mTORC1 from these nutrient inputs – elicited by the loss of Rag GTPases – inhibits mTORC1 activity and prevents YAP/TAZ-dependent vascular growth. These findings define a pivotal role for YAP/TAZ-TEAD in steering endothelial mTORC1 and illustrate the essentiality of coordinated nutrient fluxes in the vasculature.
Project description:Endothelial cell is the major cell type that senses and transduces mechanosignal generated by shear stress. We have recently shown that Hippo/YAP pathway is a mechanosensitive pathway that is critical for maintaining endothelial cell homeostasis. However, the transcritpional targets and biological functions of YAP in endothelial cells remain largely unknown. To evaluate YAP-dependent gene expression in endothelial cells, we performed RNA-sequencing in YAP depleted (by transfection with by YAP siRNA) and overexpressed (by infection with YAP-S127A catalytically active adenovirus) human endothelial cells. We observed that YAP critically regulates endothelial function by modulating multiple atherosclerosis-related genes. Our study provides mechanistic insights into the question how YAP regulates endothelial function and atherosclerosis by modulating endothelial transcriptional profile.
Project description:To identify YAP binding partners potentially involved in mechanotransduction, we performed a YAP co-IP/MS experiment using sparsely or densely plated MCF10A cells.
Project description:Non-canonical Wnt signaling activated by Wnt5a and Wnt11 is required for the development of second heart field cardiac progenitor cells in mice. However, the pathophysiological role of non-canonical Wnt signaling in the adult heart has not been fully elucidated. Here we show that cardiomyocyte-specific Wnt5a knockout mice exhibit improved systolic function and reduced expression of mechanosensitive genes including Nppb compared to control mice when subjected to pressure overload. In cultured cardiac myocytes, Wnt5a knockdown reduces the upregulation of Nppb gene expression and YAP nuclear translocation induced by cyclic cell stretch. Wnt5a knockdown-induced Nppb downregulation in response to cell stretch is rescued by inhibition of Hippo pathway, and the rescue effect of Hippo inhibition is canceled by YAP knockdown. These results collectively suggest that Wnt5a-YAP signaling axis mediates mechanotransduction in cardiac myocytes and contributes to the transition to heart failure.
Project description:Non-canonical Wnt signaling activated by Wnt5a and Wnt11 is required for the development of second heart field cardiac progenitor cells in mice. However, the pathophysiological role of non-canonical Wnt signaling in the adult heart has not been fully elucidated. Here we show that cardiomyocyte-specific Wnt5a knockout mice exhibit improved systolic function and reduced expression of mechanosensitive genes including Nppb compared to control mice when subjected to pressure overload. In cultured cardiac myocytes, Wnt5a knockdown reduces the upregulation of Nppb gene expression and YAP nuclear translocation induced by cyclic cell stretch. Wnt5a knockdown-induced Nppb downregulation in response to cell stretch is rescued by inhibition of Hippo pathway, and the rescue effect of Hippo inhibition is canceled by YAP knockdown. These results collectively suggest that Wnt5a-YAP signaling axis mediates mechanotransduction in cardiac myocytes and contributes to the transition to heart failure.