Project description:Adipose tissues serve as an energy reservoir and endocrine organ, yet the mechanisms that coordinate these functions remain elusive. Here, we show that transcriptional coregulators YAP and TAZ mediate the crosstalk between fat mass and leptin levels to maintain metabolic homeostasis. Activating YAP/TAZ in adipocytes by Lats1 and Lats2 deletion results in a profound reduction in fat mass by converting mature adipocytes into delipidated progenitor-like cells. Surprisingly, Lats1/2 knockout mice did not exhibit lipodystrophy-related metabolic dysfunction, attributed to a paradoxical increase in circulating leptin levels. Mechanistically, YAP/TAZ-TEAD signaling upregulates leptin expression by directly binding an upstream enhancer site of the leptin gene. We further show that YAP/TAZ activity is linked to, and functionally required for, leptin regulation during fasting and refeeding. These results suggest that adipocyte Hippo-YAP/TAZ plays an essential role in coordinating adipose storage capacity and systemic energy balance through dual control of adipocyte plasticity and leptin gene transcription.
Project description:Adipose tissue contributes to systemic energy homeostasis by serving as an energy reservoir and endocrine organ. Coordinated regulation of these functions is essential for metabolic health, but the mechanisms that underlie cross-talk between them have been unknown. Here we show that the transcriptional coregulators YAP and TAZ of the Hippo signaling pathway in adipose tissue control systemic energy balance. Mechanistically, we identify a YAP/TAZ-TEAD axis that upregulates leptin expression by directly binding to an upstream enhancer site of the leptin gene.
Project description:The Hippo pathway downstream effectors, Yap and Taz, play key roles in cell proliferation and tissue growth, regulating gene expression especially via interaction with Tead transcription factors. To investigate their role in skeletal muscle stem cells, we analysed gene expression changes driven by Taz and compared these to Yap mediated changes to the transcriptome by measurement of gene expression on Affymetrix microarrays. To interrogate overlapping and unique transcriptional changes driven by these Hippo effectors, satellite cell-derived myoblasts were transduced with constitutively active TAZ S89A or YAP S127A retrovirus for 24h or 48h, with empty retrovirus as control. Triplicate microarray analyses of empty vector controls, hYAP1 S127A and TAZ S89A transgenic primary myoblasts were conducted.
Project description:The Hippo pathway plays a crucial in organ size control during development and tissue homeostasis in adult life. To examine a role for Hippo signaling in the intestinal epithelium, we analyzed gene expression patterns in the mouse intestinal epithelilum transfected with siRNAs or expression plasmids for shRNAs targeting the Hippo pathway effectors, YAP and TAZ. We performed two independent series of experiments (siGFP (n=3) vs siYAP/siTAZ (n=3), and shLacZ (n=1) vs shYAP/shTAZ (n=1)). Control siRNA (siGFP), YAP/TAZ siRNAs, or expression plasmids for control shRNA (shLacZ) or YAP/TAZ shRNAs were introduced into the mouse intestinal epithelium by the newly-developed in vivo transfection method. Four days after transfection, intestinal epithelial cells were isolated from the tissues and total RNA was extracted.
Project description:The Hippo pathway is an emerging signaling cascade involved in the regulation of organ size control. It consists of evolutionally conserved protein kinases that are sequentially phosphorylated and activated. The active Hippo pathway subsequently phosphorylates a transcription coactivator, YAP, which precludes its nuclear localization and transcriptional activation. Identification of transcriptional targets of YAP in diverse cellular contexts is therefore critical to the understanding of the molecular mechanisms in which the Hippo pathway restricts tissue growth. We used microarrays to profile the gene expression patterns upon acute siRNA knockdown of Hippo pathway components in multiple mammalian cell lines and identified a set of genes representing immediate transcriptional targets of the Hippo/Yap signaling pathway. Three mammalian cell lines (HEK293T, HepG2, HaCaT) were transfected with scramble siRNA controls or siRNAs against NF2 and LATS2, two core components of the Hippo pathway, simultaneously. Total RNAs were harvested four days after transfection to reveal the gene expression pattern unsing microarry. YAP and TAZ siRNAs were also transfected along with NF2 and LATS2 siRNAs to identify YAP/TAZ-dependent transcriptional targets upon loss of NF2/LATS2.
Project description:In several developmental lineages, an increase in expression of the MYC proto-oncogene drives the transition from quiescent stem cells to transit amplifying cells. The mechanism by which MYC restricts self-renewal of adult stem cells is unknown. Here, we show that MYC activates a stereotypic transcriptional program of genes involved in protein translation and mitochondrial biogenesis in mammary epithelial cells and indirectly inhibits the YAP/TAZ co-activators that are essential for mammary stem cell self-renewal. We identify a phospholipase of the mitochondrial outer membrane, PLD6, as the mediator of MYC activity. PLD6 mediates a change in the mitochondrial fusion/fission balance that promotes nuclear export of YAP/TAZ in a LATS- and RHO-independent manner. Mouse models and human pathological data confirm that MYC suppresses YAP/TAZ activity in mammary tumors. PLD6 is also required for glutaminolysis, arguing that MYC-dependent changes in mitochondrial dynamics balance cellular energy metabolism with the self-renewal potential of adult stem cells. ChIP-Seq experiments for MYC-HA (HA-IP) performed in IMEC primary breast epithelial cells. Input-samples were sequenced as controlls.
Project description:Human cancer is often caused by dysfunctional developmental pathways, but such mechanisms do not always present clear opportunities for therapeutic intervention. This is exemplified by the Hippo tumor suppressor pathway, which is comprised of a kinase module that restrains the function of YAP/TAZ transcriptional coactivators; a pathway that becomes dysregulated in a wide array of human cancers. Hence, YAP/TAZ hyperactivation is a tumorigenic mechanism and a validated therapeutic target in oncology. In this study, we used a paralog co-targeting genetic screening strategy to identify the kinases MARK2/3 as co-dependencies of YAP/TAZ in diverse cancer contexts. We use biochemical and epistasis experiments to show that MARK2/3 phosphorylate and inhibit the activity of Hippo pathway components NF2, MST1/2, and MAP4Ks, which leads to indirect upstream control of LATS1/2 activity. In addition, MARK2/3 directly phosphorylate YAP/TAZ to shield these coactivators from LATS1/2-mediated inhibition. The net consequence of this multi-level regulation is that YAP/TAZ-dependent human cancers have an absolute requirement for MARK2/3 catalytic activity to sustain tumor cell proliferation and viability. To simulate therapeutic targeting of MARK2/3 in vivo, we adapted the EPIYA-repeat region of the CagA protein from H. pylori as a catalytic inhibitor of MARK2/3, which we show exerts potent anti-tumor activity via on-target mechanisms. Together, these findings reveal MARK2/3 as an obligate catalytic requirement for YAP/TAZ function in human cancer; kinase targets that may allow for novel pharmacology that restores Hippo-mediated tumor suppression.
Project description:Human cancer is often caused by dysfunctional developmental pathways, but such mechanisms do not always present clear opportunities for therapeutic intervention. This is exemplified by the Hippo tumor suppressor pathway, which is comprised of a kinase module that restrains the function of YAP/TAZ transcriptional coactivators; a pathway that becomes dysregulated in a wide array of human cancers. Hence, YAP/TAZ hyperactivation is a tumorigenic mechanism and a validated therapeutic target in oncology. In this study, we used a paralog co-targeting genetic screening strategy to identify the kinases MARK2/3 as co-dependencies of YAP/TAZ in diverse cancer contexts. We use biochemical and epistasis experiments to show that MARK2/3 phosphorylate and inhibit the activity of Hippo pathway components NF2, MST1/2, and MAP4Ks, which leads to indirect upstream control of LATS1/2 activity. In addition, MARK2/3 directly phosphorylate YAP/TAZ to shield these coactivators from LATS1/2-mediated inhibition. The net consequence of this multi-level regulation is that YAP/TAZ-dependent human cancers have an absolute requirement for MARK2/3 catalytic activity to sustain tumor cell proliferation and viability. To simulate therapeutic targeting of MARK2/3 in vivo, we adapted the EPIYA-repeat region of the CagA protein from H. pylori as a catalytic inhibitor of MARK2/3, which we show exerts potent anti-tumor activity via on-target mechanisms. Together, these findings reveal MARK2/3 as an obligate catalytic requirement for YAP/TAZ function in human cancer; kinase targets that may allow for novel pharmacology that restores Hippo-mediated tumor suppression.
Project description:Abstract Hippo pathway downstream effectors Yap and Taz play key roles in cell proliferation and regeneration, regulating gene expression especially via interaction with Tead transcription factors. To investigate their role in skeletal muscle stem cells, we analysed Taz in vivo and ex vivo in comparison to Yap. Taz was expressed in activated satellite cells. siRNA knockdown or constitutive expression of wildtype or constitutively active TAZ mutants showed that TAZ promoted proliferation, a function that was shared with YAP. However, at later stages of myogenesis, TAZ also enhanced myogenic differentiation of myoblasts, whereas YAP inhibits such differentiation. Functionally, while muscle growth was mildly affected in Taz (gene symbol Wwtr1-/-) knockout mice, there were no overt effect on regeneration. However, conditional knockout of Yap in satellite cells of Pax7Cre-ERT2/+ : Yapflox/flox : Rosa26Lacz mice produced a marked regeneration deficit. To identify potential mechanisms, microarray analysis showed many common Taz/Yap targets, but Taz also regulates some genes independently of Yap, including myogenic genes such as Pax7, Myf5 and Myod1. Proteomic analysis of Yap/Taz revealed many common binding partners, but Taz also interacts with proteins distinct from Yap, that are mainly involved in myogenesis and aspects of cytoskeleton organization. Neither TAZ nor YAP bind members of the Wnt destruction complex but both extensively changed expression of Wnt and Wnt-cross talking genes with known roles in myogenesis. Finally, TAZ operates through Tead4 to enhance myogenic differentiation. In summary, Taz and Yap have overlapping functions in promoting myoblast proliferation but Taz then switches to promote myogenic differentiation.