Posts Tagged: signal transduction

PI3K and Calcium Signaling in Cardiovascular Disease

PI3K and Calcium Signaling in Cardiovascular Disease

Alessandra Ghigo, Muriel Laffargue, Mingchuan Li, Emilio Hirsch

Class I PI3Ks (phosphoinositide 3-kinases). Class I PI3Ks are obligate heterodimers composed by a p110 catalytic module and an adaptor subunit. Depending on the nature of the adaptor and of the activating membrane receptor, class I PI3Ks can be subgrouped into class IA and IB. Class IA includes PI3Kα, β, and δ, which are coupled to a p85 regulatory subunit and are engaged by tyrosine kinase receptors (RTKs). On the contrary, the unique member of class IB, PI3Kγ, binds to either p101 or p87 that, by tethering p110γ to the Gβγ subunit of G protein-coupled receptors (GPCRs), ensure the full enzyme activation. All class I isoenzymes phosphorylate PIP2 PtdIns(4,5)P2 to produce PIP3 that, in turn, serves as a docking site for intracellular effectors carrying a lipid-binding domain, such as Akt (protein kinase B). Activated Akt ultimately initiates a wide spectrum of biological events, ranging from proliferation, survival, and metabolic regulation. [Powerpoint File]

PI3K and Calcium Signaling in Cardiovascular Disease

PI3K and Calcium Signaling in Cardiovascular Disease

Alessandra Ghigo, Muriel Laffargue, Mingchuan Li, Emilio Hirsch

PI3K (phosphoinositide 3-kinase)-mediated compartmentalization of β-adrenergic receptors-dependent Ca2+ responses in cardiomyocytes. Class IB PI3Kγ restrains Ca2+ signaling in response to β-adrenergic stimuli via a kinase-unrelated mechanism. This relies on the ability of PI3Kγ to anchor PDE (phosphodiesterase)3 or 4 to their activator PKA in specific subcellular compartments and to promote PKA-mediated activation of PDEs (active PDE3/4). The ensuing cyclic AMP (cAMP) reduction limits PKA-mediated phosphorylation and activation of Ca2+-handling proteins, including L-type Ca2+ channel (LTCC) and PLN (phospholamban; left). In heart failure, a functional decay in PI3Kγ-directed protein–protein interactions limits PDE activity (inactive PDE3/4), leading to abnormal cAMP accumulation and uncontrolled PKA activity close to LTCC and PLN, which culminate in arrhythmogenic Ca2+ release events (right). PLN indicates phospholamban; and SR, sarcoplasmic reticulum. [Powerpoint File]

Protein Interactions at Endothelial Junctions and Signaling Mechanisms Regulating Endothelial Permeability

Protein Interactions at Endothelial Junctions and Signaling Mechanisms Regulating Endothelial Permeability

Yulia A. Komarova, Kevin Kruse, Dolly Mehta, Asrar B. Malik

Mechanotransduction at adherens junctions (AJs). The mechanosensory complex in endothelial cells is composed of vascular endothelial (VE)-cadherin, platelet endothelial cell adhesion molecule (PECAM)-1, and vascular endothelial growth factor receptor (VEGFR) 2. Mechanosensing of shear stress occurs through PECAM-1–dependent activation of Fyn, which in turn facilitates VEGFR2-mediated signaling in a ligand-independent manner and activates phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K). PI3K activates both Rac1 and endothelial nitric oxide synthase (eNOS) signaling pathways. Rac1 relieves tension at AJs, whereas NO concomitantly promotes vasorelaxation of smooth muscle cells. PECAM-1–dependent sensing of shear stress also promotes α2β1 integrin signaling and consequently activation of protein kinase A (PKA) in atheroresistant regions. PKA phosphorylates RhoA and decreases RhoA-dependent cellular stiffness allowing the endothelial cell to align in the direction of blood flow. GPCR indicates G-protein–coupled receptor; and sGC, soluble guanylyl cyclase. [Powerpoint File]

Protein Interactions at Endothelial Junctions and Signaling Mechanisms Regulating Endothelial Permeability

Protein Interactions at Endothelial Junctions and Signaling Mechanisms Regulating Endothelial Permeability

Yulia A. Komarova, Kevin Kruse, Dolly Mehta, Asrar B. Malik

Role of actomyosin apparatus in stabilizing adherens junctions (AJs). A, Domain structure of nonmuscle myosin-II (NM-II). The NM-II consists of a globular head domain containing both actin-binding and motor domains, essential light chains (ELCs), regulatory light chains (RLCs), and heavy chains. NM-II possesses a head-to-tail interaction in the absence of phosphorylation. Phosphorylation of regulatory light chain at Thr18/Ser19 by myosin light chain kinase (MLCK) unfolds the molecule, enabling assembly of antiparallel filaments through interactions between their rod domains. Activation of Rho-associated kinase (ROCK), which inhibits phosphatase activity of myosin light chain phosphatase (MLCP) in a phosphorylation-dependent manner, also favors RLC phosphorylation. NM-II filaments bind to actin filaments, which slide along each other, and cause a cell contraction. Modified from Vicente-Manzanares et al415 with permission of the publisher. Copyright ©2009, Nature Publishing Group. B, Proposed mechanism of regulation of NM-II activity at AJs in confluent endothelium. NM-II regulates attachment of the vascular endothelial (VE)-cadherin adhesion complex to the actin cytoskeleton, thereby generating mechanical tension required for binding of α-catenin to both β-catenin and f-actin. NM-II phosphorylation is controlled by MLCK and MLCP activities. In the model, we propose that Src and Cdc42 pathways cooperate in regulating NM-II activity at AJs. Cdc42 facilitates activation of NM-II through myotonic dystrophy kinase–related Cdc42-binding kinase (MRCK)–dependent phosphorylation of MLCP, whereas Src phosphorylates MLCK at sites of VE-cadherin adhesion. CaM indicates calmodulin; GAP, GTPase-activating protein; and GEF, guanine nucleotide exchange factor. [Powerpoint File]

Protein Interactions at Endothelial Junctions and Signaling Mechanisms Regulating Endothelial Permeability

Protein Interactions at Endothelial Junctions and Signaling Mechanisms Regulating Endothelial Permeability

Yulia A. Komarova, Kevin Kruse, Dolly Mehta, Asrar B. Malik

Composition of interendothelial junctions. A, Schematic representation of interendothelial junctions composed of tight junctions (TJs), adherens junctions (AJs), and gap junctions (GJs). TJs are mediated by adhesion proteins such as claudins, occludin, and junctional adhesion molecules (JAMs), whereas the zona occludin proteins (ZO-1, ZO-2, and ZO-3) connect adhesion molecules to the actin cytoskeleton. AJs are composed of vascular endothelial (VE)-cadherin and associated β- and p120-catenins. α-catenin binds β-catenin to connect AJs to the actin cytoskeleton. GJs are composed of 2 connexin hexamers forming hemichannels. B, VE-cadherin mediates adhesion by trans-dimerization of tryptophan 2 and tryptophan 4 residues in a hydrophobic pocket of the opposing VE-cadherin molecule. Ribbon presentations of VE-cadherin trans-dimer. C, Strand swap dimerization occurs through the insertion of a tryptophan residue into the hydrophobic binding pocket of the opposing cadherin. D, Trans-dimerization (between endothelial cell [EC] 1 and EC1 of opposing cadherins) orients VE-cadherin molecules and facilitates cis interactions (between EC1 and EC2 of neighboring cadherins). Panels B, C, and D are modified from Brasch et al115 with permission of the publisher. Copyright ©2012, Elsevier. [Powerpoint File]

The Expanding Complexity of Estrogen Receptor Signaling in the Cardiovascular System

The Expanding Complexity of Estrogen Receptor Signaling in the Cardiovascular System

Sara Menazza, Elizabeth Murphy

Nongenomic estrogen receptor (ER) signaling. A, Rapid ER signaling in vascular endothelial cells. ERs localize to caveolae by direct binding to caveolin-1 and scaffold protein striatin. On estrogen binding, ERs and the G protein form a complex leading to activation of tyrosine kinase Src, serine/threonine kinase phosphatidylinositol-3-OH kinase (PI3K; binding the subunit p38a), activation of protein kinase B (Akt), and mitogen-activated protein kinase (MAPK). Kinases then directly activate endothelial nitric oxide synthase (eNOS) by serine 1177 phosphorylation. The increased production of nitric oxide (NO) promotes endothelial cell vasodilatation, proliferation, and migration. B, Rapid ER signaling in vascular smooth muscle cells. ERs localize to caveolae by direct binding to caveolin-1 and scaffold protein striatin. On estrogen binding, ERs activate several phosphatases leading to inhibition of kinases and finally resulting in a decrease of cell proliferation and migration. MKP-1 indicates mitogen-activated protein kinase phosphatase-1; PP2A, protein phosphatase 2A; PTEN, phosphatase and tensin homolog; and SHP-1, Src homology region 2 domain-containing phosphatase-1. [Powerpoint File]

The Expanding Complexity of Estrogen Receptor Signaling in the Cardiovascular System

The Expanding Complexity of Estrogen Receptor Signaling in the Cardiovascular System

Sara Menazza, Elizabeth Murphy

Effects of estrogen on the heart. Estrogen has many pleiotropic effects on the cardiovascular system. Estrogen can impact cardiovascular health and disease by direct effects: (1) on the vascular endothelial cells promoting vasorelaxation, cell proliferation, and migration; (2) on vascular smooth muscle cells decreasing cell proliferation and migration; and (3) on cardiomyocytes reducing low-density lipoprotein (LDL)-cholesterol level and protecting against insulin resistance, infarct size, and ischemia–reperfusion injury and cardiac hypertrophy. [Powerpoint File]

The Expanding Complexity of Estrogen Receptor Signaling in the Cardiovascular System

The Expanding Complexity of Estrogen Receptor Signaling in the Cardiovascular System

Sara Menazza, Elizabeth Murphy

Genomic estrogen receptor (ER) signaling. A, Direct binding to DNA. Estrogen binding to ERs promotes receptor translocation to the nuclei. ERs bind to the consensus estrogen response element (ERE) in the DNA, mediating its genomic effects. Coactivators and corepressors are recruited to activate or inhibit gene. B, Indirectly binding DNA through other transcription factors. ERs can tether transcription factors (TF) such as API and Sp1 regulating gene expressions. C and D, Ligand-independent binding. ERs can be phosphorylated by kinases signaling (such as p38, extracellular-signal-regulated kinase [ERK], and activation of protein kinase B [Akt]) activated by plasma membrane ERs signaling. Specific serine site phosphorylation of ERs can trigger its binding to DNA, thus activating the transcription via ligand-independent binding or via ERE-binding. MAPK indicates mitogen-activated protein kinase; and PI3K, phosphatidylinositol-3-OH kinase. [Powerpoint File]

The Expanding Complexity of Estrogen Receptor Signaling in the Cardiovascular System

The Expanding Complexity of Estrogen Receptor Signaling in the Cardiovascular System

Sara Menazza, Elizabeth Murphy

Orphan G-protein–coupled receptor (GRP30) activation via endothelium-independent or endothelium-dependent mechanisms. A, Endothelium-independent effect is mediated by a large conductance calcium-activated potassium channel leading to an increase in potassium efflux. This effect results in coronary artery relaxation. BK indicates Ca2+- and voltage-activated K+ channels. B, Endothelium-dependent mechanism. Estrogen binding to GPR30 leads to activation of endothelial nitric oxide (NO) synthase raising the production of NO in coronary endothelial cells to relax these arteries. [Powerpoint File]

Regulation of Signal Transduction by Reactive Oxygen Species in the Cardiovascular System

Regulation of Signal Transduction by Reactive Oxygen Species in the Cardiovascular System

David I. Brown, Kathy K. Griendling

Redox signaling pathways in migration and adhesion. Dark gray, redox modified proteins. AngII indicates angiotensin II; DAG, diacyl-glycerol; ECM, extracellular matrix; IP3, inositol trisphosphate; Jnk, c-Jun N-terminal kinase; LMW-PTP, low molecular weight protein tyrosine phosphatase; MLCP, myosin light chain phosphatase; PI3K, phosphoinositide 3-kinase; PIP2, phosphatidylinositol 4,5-bisphosphate; PKC, protein kinase C; PLC, phospholipase C; ROK, Rho-associated protein kinase; ROS, reactive oxygen species; SOS, son of sevenless homolog 1; Src, Proto-oncogene tyrosine-protein kinase Src; and SSH1L, Slingshot homolog 1. [Powerpoint File]

Regulation of Signal Transduction by Reactive Oxygen Species in the Cardiovascular System

Regulation of Signal Transduction by Reactive Oxygen Species in the Cardiovascular System

David I. Brown, Kathy K. Griendling

Redox signaling pathways in hypertrophy and proliferation. Dark gray, Redox modified proteins. AngII indicates angiotensin II; AP1, activator protein 1; ASK1, apoptosis signal-regulating kinase 1; AT1R, angiotensin II type 1 receptor; DAG, diacyl-glycerol; ERK1/2, extracellular signal-regulated kinase 1/2; Ets-1, v-ets avian erythroblastosis virus E2 oncogene homolog 1; IP3, inositol triphosphate; JAK, janus kinase; MAPKAPK2, mitogen-activated protein kinase-activated protein kinase 2; MEK3/6, MAPK/ERK kinase 3/6; NF-κB, nuclear factor-κB; PDGF, platelet-derived growth factor; PI3K, phosphoinositide 3-kinase; PIP2, phosphatidylinositol 4,5-bisphosphate; PKC, protein kinase C; PLC, phospholipase C; PP3, phosphatase calcineurin; PTEN, phosphatase and tensin homolog; RyR, ryanodine receptor; SOD, superoxide dismutase; SERCA, sarcoendoplasmic reticulum calcium transport ATPase; Src, Proto-oncogene tyrosine-protein kinase Src; STAT, signal transducer and activator of transcription; and Trx, thioredoxin (Illustration credit: Ben Smith). [Powerpoint File]

Regulators of G-Protein Signaling in the Heart and Their Potential as Therapeutic Targets

Regulators of G-Protein Signaling in the Heart and Their Potential as Therapeutic Targets

Peng Zhang, Ulrike Mende

Regulation of G-protein–mediated signaling by RGS proteins. See text for detail on the G-protein activation/inactivation cycle. RGS proteins regulate G-protein–mediated signaling through (1) marked acceleration of Gα GTPase activity, which decreases both Gα- and Gβγ-mediated downstream effects, and (2) competition with downstream effectors for binding to activated Gα, which inhibits only Gα-mediated signal generation. Please note that this illustration depicts the traditional view of GPCR-induced, G-protein–mediated signal transduction. It does not incorporate GPCR-independent G-protein activation147 or G-protein–independent GPCR effects.148 Furthermore, full dissociation of Gα and Gβγ subunits may not be required to trigger downstream effects.149 [Powerpoint File]

Regulation of Cell Survival and Death by Pyridine Nucleotides

Regulation of Cell Survival and Death by Pyridine Nucleotides

Shin-ichi Oka, Chiao-Po Hsu, Junichi Sadoshima

Sirt1-mediated protein deacetylation. Sirt1 hydrolyzes NAD+ to generate ADP-ribose units and nicotinamide. The acetyl group of the Sirt1 target proteins is removed and attached to the ADP-ribose to generate 2-O-acetyl-ADP-ribose. [Powerpoint File]

The Fire Within: Cardiac Inflammatory Signaling in Health and Disease

The Fire Within: Cardiac Inflammatory Signaling in Health and Disease

Matthew Coggins, Anthony Rosenzweig

A schematic representation of some of the stimuli, receptors, and downstream signaling events involved in inflammation. The pathways depicted for recognition of viral RNA and DNA, and generation of interferons (IFNs), are typical of immune cells and have not been fully characterized in cardiomyocytes or cardiac fibroblasts. In immune cells, features particular to viral RNA are recognized by RIG-I and other members of the RIG-I–like receptor family. These proteins then interact with the adaptor protein mitochondrial antiviral signaling protein (MAVS) on the mitochondrial membrane. Through intermediates not shown, MAVS may lead to activation of the transcription factor IFN regulatory factor (IRF)-3. RIG-I can also activate the inflammasome through complex formation with ASC and procaspase-1. The other pathways depicted have been better-characterized in cardiomyocytes. Cell surface toll-like receptors (TLR) are activated by pathogen-associated molecular patterns or danger-associated molecular patterns to initiate intracellular signaling. For simplicity, the pathway shown is typical of TLR4. Binding of tumor necrosis factor (TNF)-α to its receptor leads to recruitment of the TNF receptor-associated death domain TRADD (adapted from Gordon et al3) and activation of the TNF receptor-associated protein complex. The type-1 IFNs bind to a receptor with two subunits (IFN-α receptor-1 and IFN-α receptor-2), which leads to activation of tyrosine kinases JAK1 and TYK2, which phosphorylate the transcription factors STAT1 and STAT2. The activated STAT proteins associate with IRF-9 and regulate the expression of a large number of IFN-stimulated genes (adapted from Sun et al36). Many inflammatory pathways ultimately converge on NFκB signaling. The IKK complex, including IKKα, IKKβ, and IKKγ (NEMO), leads to phosphorylation of the inhibitory subunit, IκB, leading to its degradation and allowing NFκB to translocate to the nucleus, where it induces transcription of target genes. Importantly, many of these target genes drive inflammation, whereas others regulate (generally inhibit) cell death. Thus NFκB itself illustrates the duality of inflammatory signaling, which complicates attempts to exploit these mechanisms as therapeutic targets. [Powerpoint File]

Overview of Pyridine Nucleotides Review Series

Overview of Pyridine Nucleotides Review Series

Michinari Nakamura, Aruni Bhatnagar, Junichi Sadoshima

Schematic of pyridine nucleotides biosynthesis and their functions. Pyridine nucleotides are involved in a wide variety of cellular functions, including energy production, metabolism, redox reactions, survival/death, and ion channels under normal and pathological conditions. Trp indicates tryptophan; Na, nicotinic acid; QA, quinolinic acid; NaMN, nicotinic acid mononucleotide; Nam, nicotinamide; NMN, nicotinamide mononucleotide; NR, nicotinamide riboside; Nampt, nicotinamide phosphoribosyltransferase; Nmnat, Nam/Na mononucleotide adenylyl transferase; NADK, NAD kinase; NaPRT, Na phosphoribosyltransferase; QAPRT, quinolate phosphoribosyltransferase; NaMNAT, nicotinic acid mononucleotide adenylyltransferase; NaAD, nicotinic acid adenine dinucleotide; NaDS, NAD synthase; Trx, thioredoxin; Nox, NADPH oxidase; GSH, glutathione; Redox, reduction-oxidation; ROS, reactive oxygen species; PARP, poly(ADP-ribose) polymerases; MART, mono-ADP-ribose transferase; cADP, cyclic ADP-ribose synthase; ETC, electron transport chain. [Powerpoint File]