MiR-182 modulates myocardial hypertrophic response induced by angiogenesis in heart (miRNA)
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ABSTRACT: Angiogenesis induced by placental growth factor (PlGF) in heart promotes myocardial hypertrophy through the paracrine action of endothelium-derived nitric oxide which triggers the degradation of RGS4 and subsequent activation of the Akt/mTORC1 pathway in cardiomyocytes. However, whether alterations in miRNAs contribute to the development of hypertrophy is largely undetermined. We found that miR-182 contributed to the hypertrophic response and activation of the Akt/mTORC1 pathway by suppressing the expression of Bcat2, Pink1, Adcy6, Foxo3.
Project description:Angiogenesis induced by placental growth factor (PlGF) in heart promotes myocardial hypertrophy through the paracrine action of endothelium-derived nitric oxide which triggers the degradation of RGS4 and subsequent the activation of Akt/mTORC1 pathway in cardiomyocytes. However, whether alterations in miRNAs contribute to the development of hypertrophy is largely undetermined. We found that miR-182 contributed to the hypertrophic response and activation of Akt/mTORC1 pathway by suppressing the expression of Bcat2, Pink1, Adcy6, Foxo3. miR-182 targeted genes were investigated in the mouse model of myocardial angiogenesis induced by conditional, cardiac specific expression of PlGF. We also induced angiogenesis, but blocked hypertrophy by concomitant expression of PlGF and RGS4 (PlGF/RGS4 mice). The mRNA expression profiling in PlGF and PlGF/RGS4 mice were assessed after 6 weeks of transgene expression, concurent with the development of myocardial hypertrophy.
Project description:Angiogenesis induced by placental growth factor (PlGF) in heart promotes myocardial hypertrophy through the paracrine action of endothelium-derived nitric oxide which triggers the degradation of RGS4 and subsequent activation of the Akt/mTORC1 pathway in cardiomyocytes. However, whether alterations in miRNAs contribute to the development of hypertrophy is largely undetermined. We found that miR-182 contributed to the hypertrophic response and activation of the Akt/mTORC1 pathway by suppressing the expression of Bcat2, Pink1, Adcy6, Foxo3. The expression of miRNAs and the effects of anti-miRs were investigated in the mouse model of myocardial angiogenesis induced by conditional, cardiac specific expression of PlGF. We also induced angiogenesis, but blocked hypertrophy by concomitant expression of PlGF and RGS4 (PlGF/RGS4 mice). Microarray profiling of miRNAs in LV myocardium was determined after 3 and 6 weeks of transgene expression.
Project description:Angiogenesis induced by placental growth factor (PlGF) in heart promotes myocardial hypertrophy through the paracrine action of endothelium-derived nitric oxide which triggers the degradation of RGS4 and subsequent the activation of Akt/mTORC1 pathway in cardiomyocytes. However, whether alterations in miRNAs contribute to the development of hypertrophy is largely undetermined. We found that miR-182 contributed to the hypertrophic response and activation of Akt/mTORC1 pathway by suppressing the expression of Bcat2, Pink1, Adcy6, Foxo3.
Project description:Muscle size is controlled by the PI3K-PKB/Akt-mTORC1-FoxO pathway, which integrates signals from growth factors, energy and amino acids to activate protein synthesis and inhibit protein breakdown. While mTORC1 activity is necessary for PKB/Akt-induced muscle hypertrophy, its constant activation alone induces muscle atrophy. Here we show that this paradox is based on mTORC1 activity promoting protein breakdown through the ubiquitin-proteasome system (UPS) by simultaneously inducing ubiquitin E3 ligase expression via feedback inhibition of PKB/Akt and proteasome biogenesis via Nuclear Factor Erythroid 2-Like 1 (Nrf1). Muscle growth was restored by reactivation of PKB/Akt, but not by Nrf1 knockdown, implicating ubiquitination as the limiting step. However, both PKB/Akt activation and proteasome depletion by Nrf1 knockdown led to an immediate disruption of proteome integrity with rapid accumulation of damaged material. These data highlight the physiological importance of mTORC1-mediated PKB/Akt inhibition and point to juxtaposed roles of the UPS in atrophy and proteome integrity.
Project description:Forkhead box O transcription factors are important downstream targets of AKT signalling. In the human Multiple Myeloma celline MM1.S, AKT inhibtion leads to cell death in a FOXO3 dependent fashion. We used microarrays to asses which genes are up- or downregulated by FOXO3 after AKT inhibition by MK2206.
Project description:Forkhead box O transcription factors are important downstream targets of AKT signalling. In the human Multiple Myeloma celline XG-3, AKT inhibtion leads to cell death in a FOXO3 dependent fashion. We used microarrays to asses which genes are up- or downregulated by FOXO3 after AKT inhibition by MK2206.
Project description:The mammalian FoxO transcription factors - FoxO1, FoxO3, FoxO4 - function in the nucleus to direct transcription of specific gene targets governing cellular survival, proliferation, metabolism, differentiation and oxidative defense. Activation of PI3K by extracellular growth factors leads to AKT-mediated phosphorylation of FoxO1, FoxO3 and FoxO4, resulting in their sequestration in the cytoplasm such that they are unable to regulate their gene targets. Our study identified FoxOs as novel tumor suppressors in kidney cancer (Gan et al, 2010, Cancer Cell). To understand the tumor suppression function of FoxOs in kidney cancer cells, we performed gene expression profiling in human kidney cancer cells upon FoxO1 or FoxO3 reactivation in order to identify the key transcriptomic alterations mediating FoxO tumor suppression function in kidney cancer cells. We generated RCC4 and UMRC2 cell lines (two human kidney cancer cells with low endogenous FoxO1 and FoxO3 expression) with stable expression of FoxO1(TA)ERT2 or FoxO3(TA)ERT2 construct, which expressed a fusion protein consisting of FoxO(TA) (containing three Ser/Thr AKT phosphorylation sites mutated to alanine) fused to the T2-modified estrogen receptor (ERT2) moiety. We documented that the FoxO(TA)ERT2 fusion protein sequestered FoxO(TA) in the cytoplasm and that 4OHT treatment resulted in rapid translocation of FoxO(TA)ERT2 into the nucleus. We also established stable cell lines with ERT2 expression as control cell lines. (For simplicity, ERT2, FoxO1(TA)ERT2 and FoxO3(TA)ERT2 cell lines will be referred to as EV (empty vector), FoxO1 and FoxO3, respectively, hereafter). We then conducted comparative transcriptome analysis (using the Human Genome U133 Plus 2.0 Array) of EV, FoxO1, or FoxO3-expressing RCC4 and UMRC2 cells at 12 hours with or without 100 nm 4OHT treatment (cultured in DMEM+10% FBS with puromycin selection). To enrich for more proximal actions of FoxO, we selected the 12 hour time point as time course studies revealed dramatic transcriptional changes of known FoxO targets (such as Cyclin D1), yet no discernable cellular phenotypes (apoptosis and cell cycle arrest). We generated 4 transcriptome datasets: FoxO1 RCC4, FoxO3 RCC4, FoxO1 UMRC2, and FoxO3 UMRC2 (by comparing transcriptome data with or without 4OHT treatment), and normalized these transcriptome data against 4OHT-treated EV cells, which show modest 4OHT-induced transcriptional changes.
Project description:Conversion of fibroblasts to functional cardiomyocytes represents a potential approach for restoring cardiac function following myocardial injury, but the technique thus far has been slow and inefficient. To improve the efficiency of reprogramming fibroblasts to cardiac-like myocytes (iCMs) by cardiac transcription factors (Gata4, Hand2, Mef2c, and Tbx5=GHMT), we screened 192 protein kinases and discovered that Akt/protein kinase B dramatically accelerates and amplifies this process. Approximately 50% of reprogrammed fibroblasts displayed spontaneous beating after three weeks of induction by Akt plus GHMT. Furthermore, addition of Akt1 to GHMT evoked a more mature cardiac phenotype for iCMs, as seen by enhanced polynucleation, cellular hypertrophy, gene expression, and metabolic reprogramming. Igf1 and Pi3 kinase acted upstream of Akt, whereas mTORC1 and Foxo3a acted downstream of Akt to influence fibroblast-to-cardiomyocyte reprogramming. These findings provide new insights into the molecular basis of cardiac reprogramming and represent an important step toward further application of this technique.
Project description:Akt is a serine/threonine protein kinase that is activated by a variety of growth factors or cytokines in a PI3-kinase dependent manner. Using a conditional transgenic system in which Akt signaling can be turned on or off in the adult heart, we have recently demonstrated that short-term Akt activation induces a ‘physiological’ form of cardiac hypertrophy with enhanced coronary angiogenesis and maintained contractility. Here we tested the hypothesis that induction of physiological hypertrophy by short-term Akt activation might improve contractile function in failing hearts. When Akt signaling was transiently activated in murine hearts with impaired contractility induced by pressure overload or adriamycin treatment, contractile dysfunction was attenuated in both cases. Importantly, improvement of contractility was observed before the development of cardiac hypertrophy, indicating that Akt improves contractile dysfunction independently of its growth-promoting effects. To gain mechanistic insights into Akt-mediated positive inotropic effects, transcriptional profiles in the heart were determined in a pressure overload-induced heart failure model. Biological network analysis of differentially expressed transcripts revealed significant alterations in the expression of genes associated with cell death, and these alterations were reversed by short-term Akt activation. Thus, short-term Akt activation improves contractile dysfunction in failing hearts. This beneficial effect of Akt on contractility is hypertrophy-independent and may be mediated in part by inhibition of cell death associated with heart failure. Keywords: transgenic mice, Akt1, cardiac hypertrophy after ascending aortic constriction and contractile dysfunction, DNA microarrays
Project description:Effector (Teff) and regulatory (Treg) CD4 T cells undergo metabolic reprogramming to support proliferation and immune function. While Phosphatidylinositide 3-kinase (PI3K)/Akt/mTORC1 signaling induces the glucose transporter Glut1 and aerobic glycolysis for Teff proliferation and inflammatory function, mechanisms that regulate Treg metabolism and function remain unclear. We show that TLR signals that promote Treg proliferation increase Glut1, PI3K/Akt/mTORC1 signaling, and glycolysis. However, TLR-induced mTORC1 signaling also impaired Treg suppressive capacity. Conversely, FoxP3 opposed PI3K/Akt/mTOR signaling to reduce glycolysis and anabolic metabolism while increasing oxidative and catabolic metabolism. Importantly, Glut1 expression was sufficient to increase Treg numbers but reduced suppressive capacity and FoxP3 expression. Thus, inflammatory signals and FoxP3 balance mTORC1 signaling and glucose metabolism to control Treg proliferation and suppressive function.