Hypoxia Sensing of β-Adrenergic Receptor Is Regulated by Endosomal PI3Kγ.

Background: Impaired beta-adrenergic receptor (β1 and β2AR) function following hypoxia underlies ischemic heart failure/stroke. Activation of PI3Kγ (phosphoinositide 3-kinase γ) by beta-adrenergic receptor leads to feedback regulation of the receptor by hindering beta-adrenergic receptor dephosphorylation through inhibition of PP2A (protein phosphatase 2A). However, little is known about PI3Kγ feedback mechanism in regulating hypoxia-mediated β1 and β2AR dysfunction and cardiac remodeling.

Cardiac expression of microRNA-7 is associated with adverse cardiac remodeling.

Although microRNA-7 (miRNA-7) is known to regulate proliferation of cancer cells by targeting Epidermal growth factor receptor (EGFR/ERBB) family, less is known about its role in cardiac physiology. Transgenic (Tg) mouse with cardiomyocyte-specific overexpression of miRNA-7 was generated to determine its role in cardiac physiology and pathology. Echocardiography on the miRNA-7 Tg mice showed cardiac dilation instead of age-associated physiological cardiac hypertrophy observed in non-Tg control mice.

Respiratory syncytial virus induces β-adrenergic receptor dysfunction in human airway smooth muscle cells.

Pharmacologic agonism of the β-adrenergic receptor (βAR) induces bronchodilation by activating the enzyme adenylyl cyclase to generate cyclic adenosine monophosphate (cAMP). βAR agonists are generally the most effective strategy to relieve acute airway obstruction in asthmatic patients, but they are much less effective when airway obstruction in young patients is triggered by infection with respiratory syncytial virus (RSV). Here, we investigated the effects of RSV infection on the abundance and function of βAR in primary human airway smooth muscle cells (HASMCs) derived from pediatric lung tissue.

GPCRs and Insulin Receptor Signaling in Conversation: Novel Avenues for Drug Discovery.

Type 2 diabetes is a major health issue worldwide with complex metabolic and endocrine abnormalities. Hyperglycemia, defects in insulin secretion and insulin resistance are classic features of type 2 diabetes. Insulin signaling regulates metabolic homeostasis by regulating glucose and lipid turnover in the liver, skeletal muscle and adipose tissue.

G Protein-Coupled Receptor Resensitization Paradigms.

Cellular responses to extracellular milieu/environment are driven by cell surface receptors that transmit the signal into the cells resulting in a synchronized and measured response. The ability to provide such exquisite responses to changes in external environment is mediated by the tight and yet, deliberate regulation of cell surface receptor function. In this regard, the seven transmembrane G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors that regulate responses like cardiac contractility, vision, and olfaction including platelet activation.

A unique microRNA profile in end-stage heart failure indicates alterations in specific cardiovascular signaling networks.

It is well established that the gene expression patterns are substantially altered in cardiac hypertrophy and heart failure, however, less is known about the reasons behind such global differences. MicroRNAs (miRNAs) are short non-coding RNAs that can target multiple molecules to regulate wide array of proteins in diverse pathways. The goal of the study was to profile alterations in miRNA expression using end-stage human heart failure samples with an aim to build signaling network pathways using predicted targets for the altered miRNA and to determine nodal molecules regulating individual networks.

Potential Role of microRNAs in Cardiovascular Disease: Are They up to Their Hype?

Purpose Of Review: Cardiovascular diseases remain the foremost cause of mortality globally. As molecular medicine unravels the alterations in genomic expression and regulation of the underlying atherosclerotic process, it opens new vistas for discovering novel diagnostic biomarkers and therapeutics for limiting the disease process. miRNAs have emerged as powerful regulators of protein translation by regulating gene expression at the post-transcriptional level.

Defective Resensitization in Human Airway Smooth Muscle Cells Evokes β-Adrenergic Receptor Dysfunction in Severe Asthma.

β2-adrenergic receptor (β2AR) agonists (β2-agonist) are the most commonly used therapy for acute relief in asthma, but chronic use of these bronchodilators paradoxically exacerbates airway hyper-responsiveness. Activation of βARs by β-agonist leads to desensitization (inactivation) by phosphorylation through G-protein coupled receptor kinases (GRKs) which mediate β-arrestin binding and βAR internalization. Resensitization occurs by dephosphorylation of the endosomal βARs which recycle back to the plasma membrane as agonist-ready receptors.

Gβγ-independent recruitment of G-protein coupled receptor kinase 2 drives tumor necrosis factor α-induced cardiac β-adrenergic receptor dysfunction.

Background: Proinflammatory cytokine tumor necrosis factor-α (TNFα) induces β-adrenergic receptor (βAR) desensitization, but mechanisms proximal to the receptor in contributing to cardiac dysfunction are not known.

Methods And Results: Two different proinflammatory transgenic mouse models with cardiac overexpression of myotrophin (a prohypertrophic molecule) or TNFα showed that TNFα alone is sufficient to mediate βAR desensitization as measured by cardiac adenylyl cyclase activity. M-mode echocardiography in these mouse models showed cardiac dysfunction paralleling βAR desensitization independent of sympathetic overdrive.

miRNA-548c: a specific signature in circulating PBMCs from dilated cardiomyopathy patients.

High fidelity genome-wide expression analysis has strengthened the idea that microRNA (miRNA) signatures in peripheral blood mononuclear cells (PBMCs) can be potentially used to predict the pathology when anatomical samples are inaccessible like the heart. PBMCs from 48 non-failing controls and 44 patients with relatively stable chronic heart failure (ejection fraction of ≤ 40%) associated with dilated cardiomyopathy (DCM) were used for miRNA analysis. Genome-wide miRNA-microarray on PBMCs from chronic heart failure patients identified miRNA signature uniquely characterized by the downregulation of miRNA-548 family members.

Phosphoinositide 3-kinase γ inhibits cardiac GSK-3 independently of Akt.

Activation of cardiac phosphoinositide 3-kinase α (PI3Kα) by growth factors, such as insulin, or activation of PI3Kγ downstream of heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors stimulates the activity of the kinase Akt, which phosphorylates and inhibits glycogen synthase kinase-3 (GSK-3). We found that PI3Kγ inhibited GSK-3 independently of the insulin-PI3Kα-Akt axis. Although insulin treatment activated Akt in PI3Kγ knockout mice, phosphorylation of GSK-3 was decreased compared to control mice.

G-protein coupled receptor resensitization-appreciating the balancing act of receptor function.

G-protein coupled receptors (GPCRs) are seven transmembrane receptors that are pivotal regulators of cellular responses including vision, cardiac contractility, olfaction, and platelet activation. GPCRs have been a major target for drug discovery due to their role in regulating a broad range of physiological and pathological responses. GPCRs mediate these responses through a cyclical process of receptor activation (initiation of downstream signals), desensitization (inactivation that results in diminution of downstream signals), and resensitization (receptor reactivation for next wave of activation).

Long-term α1A-adrenergic receptor stimulation improves synaptic plasticity, cognitive function, mood, and longevity.

The role of α(1)-adrenergic receptors (α(1)ARs) in cognition and mood is controversial, probably as a result of past use of nonselective agents. α(1A)AR activation was recently shown to increase neurogenesis, which is linked to cognition and mood. We studied the effects of long-term α(1A)AR stimulation using transgenic mice engineered to express a constitutively active mutant (CAM) form of the α(1A)AR.

Inhibition of protein phosphatase 2A activity by PI3Kγ regulates β-adrenergic receptor function.

Phosphoinositide 3-kinase γ (PI3Kγ) is activated by G protein-coupled receptors (GPCRs). We show here that PI3Kγ inhibits protein phosphatase 2A (PP2A) at the β-adrenergic receptor (βAR, a GPCR) complex altering G protein coupling. PI3Kγ inhibition results in significant increase of βAR-associated phosphatase activity leading to receptor dephosphorylation and resensitization preserving cardiac function.

Unique microRNA profile in end-stage heart failure indicates alterations in specific cardiovascular signaling networks.

It is well established that gene expression patterns are substantially altered in cardiac hypertrophy and heart failure, but the reasons for such differences are not clear. MicroRNAs (miRNAs) are short noncoding RNAs that provide a novel mechanism for gene regulation. The goal of this study was to comprehensively test for alterations in miRNA expression using human heart failure samples with an aim to build signaling pathway networks using predicted targets for the miRNAs and to identify nodal molecules that control these networks.

alpha1-Adrenergic receptors regulate neurogenesis and gliogenesis.

The understanding of the function of alpha(1)-adrenergic receptors in the brain has been limited due to a lack of specific ligands and antibodies. We circumvented this problem by using transgenic mice engineered to overexpress either wild-type receptor tagged with enhanced green fluorescent protein or constitutively active mutant alpha(1)-adrenergic receptor subtypes in tissues in which they are normally expressed. We identified intriguing alpha(1A)-adrenergic receptor subtype-expressing cells with a migratory morphology in the adult subventricular zone that coexpressed markers of neural stem cell and/or progenitors.

Insulin-induced activation of hypoxia-inducible factor-1 requires generation of reactive oxygen species by NADPH oxidase.

Hypoxia-inducible factor (HIF)-1 activation in response to hypoxia requires mitochondrial generation of reactive oxygen species (ROS). In contrast, the requirement of ROS for HIF-1 activation by growth factors like insulin remains unexplored. To explore that, insulin-sensitive hepatic cell HepG2 or cardiac muscle cell H9c2 cells were pretreated with NADPH oxidase inhibitor diphenyleneiodonium chloride (DPI) or apocynin and HIF-1 activation was tested by electrophoretic mobility shift and reporter gene assay.

An assessment of the role of reactive oxygen species and redox signaling in norepinephrine-induced apoptosis and hypertrophy of H9c2 cardiac myoblasts.

Cardiac myocytes, upon exposure to increasing doses of norepinephrine (NE), transit from hypertrophic to apoptotic phenotype. Since reactive oxygen species (ROS) generation is attributed to both phenomena, the authors tested whether an elevation in intracellular ROS level causes such transition. H9c2 cardiac myoblasts upon treatment with hypertrophic and apoptotic doses of NE (2 and 100 microM, respectively) transiently induced intracellular ROS at a comparable level, while 200 microM H(2)O(2), another proapoptotic agonist, showed robust and sustained ROS generation.

Isolation of a library of target-sites for sequence specific DNA binding proteins from chick embryonic heart: a potential tool for identifying novel transcriptional regulators involved in embryonic development.

Enormity of the metazoan genomes and divergence in their regulation impose a serious constraint on the comprehensive understanding of context specific gene regulation. DNA elements located in the promoter, enhancer, and other regulatory regions of the genome dictate the temporal and spatial patterns of gene activities. However, owing to the diminutive and variable nature of the regulatory DNA elements, their identification and location remains a major challenge.