Journal of Molecular and Cellular Cardiology RSS feed: Current Issue. The Journal of Molecular and Cellular Cardiology publishes work advancing knowledge of the mechanisms responsible for both normal and diseased cardiovascular function. To this end papers are published in all relevant areas. These include (but are not limited to): structural biology; genetics; proteomics; morphology; stem cells; molecular biology; metabolism; biophysics; electrophysiology; pharmacology and physiology. Papers are encouraged with both basic and translational approaches. The journal is directed not only to basic scientists but also to clinical cardiologists who wish to follow the rapidly advancing frontiers of basic knowledge of the heart and circulation. JMCC Early Career Author's Prize The incoming Editor-in-Chief, David Eisner, and Roberto Bolli, President of the ISHR, are pleased to make the following announcement: We are delighted to announce a new prize designed to recognize outstanding papers published by early career authors in the Journal of Molecular and Cellular Cardiology. The first prize (sponsored jointly by ISHR and the publishers, Elsevier) will comprise $750. Two runners up will receive commendations and $250 each. The winners will be announced in the JMCC. Entries for the JMCC Young Authors Prize are invited from early career scientists who are either the first or last author of a paper published in JMCC in a given year. Applicants must have received their research degree (MD, PhD or equivalent) less than 6 years before submitting the paper. In the case of candidates who have both a MD and PhD the date of the most recently awarded degree is the relevant one. US National Institutes of Health (NIH) voluntary posting ("Public Access") policy Journal of Molecular and Cellular Cardiology and Elsevier facilitate the author's response to the NIH Public Access Policy. For more details please see the Guide for authors http://www.jmmc-online.com/?rss=yesElsevier Inc.en © 2011 Published by Elsevier Inc. All rights reserved. Journal of Molecular and Cellular Cardiology0022-2828522February 2012 © 2011 Published by Elsevier Inc. All rights reserved. healthpermissions@elsevier.comhttp://www.jmmc-online.com/article/PIIS0022282812000120/abstract?rss=yesEditorial Board10.1016/S0022-2828(12)00012-0Journal of Molecular and Cellular Cardiology 52, 2 (2012)2012-02-01Journal of Molecular and Cellular Cardiology2012-02-01522S0022-2828(12)X0002-6iihttp://www.jmmc-online.com/article/PIIS0022282811004627/abstract?rss=yesThe complex functions of cells are controlled by a surprisingly small number of second messengers. Therefore, in order to allow diverse stimuli to produce stimuli-specific cellular outcomes, it is essential that signalling is compartmentalised. In the cardiac myocyte, evidence for this fundamental principle was first presented some 3 decades ago for two of the most universal of second messengers, Ca2+ and cyclic AMP, with the recognition that the dyad was the localised site of Ca2+-induced Ca2+ release , and that β-adrenoceptor (AR) agonists and prostaglandin E1 increase cAMP in distinct cellular compartments, only the former having access to intracellular targets which regulate cardiac contractility . This seminal work has formed the basis for our current understanding of localised signalling. We now know that the diversity of cellular responses achieved with a limited pool of second messengers is made possible through organisation of essential signal components in particular organelles and in specific membrane-based structures including t-tubules, lipid rafts/caveolae, and costameres. In addition to these physical compartments, scaffolding proteins (such as A kinase anchoring proteins, caveolins and focal adhesion kinase) facilitate the formation of multi-protein complexes which create further segregation and refinement in signalling.Local signalling in myocytesSarah Calaghan, Derek Steele, James N. Weiss10.1016/j.yjmcc.2011.10.019Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-10-31Journal of Molecular and Cellular Cardiology2011-10-31522S0022-2828(12)X0002-6Guest Editors' Introduction295297http://www.jmmc-online.com/article/PIIS002228281100174X/abstract?rss=yesAbstract: The development of local control theories in cardiac excitation–contraction coupling solved a major problem in the calcium-induced calcium release (CICR) hypothesis. Local control explained how regeneration, inherent in the CICR mechanism, might be limited spatially to enable graded Ca release (and force production). The key lies in the stochastic recruitment of individual calcium release units (couplons or CRUs) where adjacent CRUs are partially uncoupled by the distance between them. In the CRU, individual groups of sarcoplasmic reticulum calcium release channels (RyRs) are very close to the surface membrane where calcium influx, controlled by membrane depolarization, leads to high local Ca levels that enable a high speed response from RyRs that have a very low probability to opening at resting Ca levels. However, calcium diffusion from an activated CRU results in adjacent CRUs being exposed to much lower levels of Ca and probability of activation. This effectively uncouples the CRUs and limits overall regenerative gain to enable stability without compromising sensitivity. Nevertheless, it is still unclear how the CRU terminates its release of calcium on the physiological timescale, and possible mechanisms (and problems) are briefly reviewed. We suggest that modulation in RyR gating may serve to control average SR Ca levels to regulate other metabolic functions of the sarco(endo)plasmic reticulum beyond regulating contractility. This article is part of a special issue entitled "Local Signaling in Myocytes."Research highlights: ► The background to the development of local control (LC) theories for cardiac excitation–contraction coupling is described. ► LC theories solve the problem of uncontrolled cell-wide regeneration during calcium-induced calcium release (CICR). ► Evidence for LC of CICR includes cytoplasmic Ca sparks and local sarcoplasmic reticulum (SR) calcium depletions (‘blinks’). ► Termination of local CICR remains unclear and key processes contributing to stochastic attrition are discussed. ► Ryanodine receptor gating modulates mean SR Ca levels which may regulate other cellular functions beyond contractility.Local control in cardiac E–C couplingM.B. Cannell, Cherrie H.T. Kong10.1016/j.yjmcc.2011.04.014Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-05-10Journal of Molecular and Cellular Cardiology2011-05-10522S0022-2828(12)X0002-6Local Ca2+ Signaling298303http://www.jmmc-online.com/article/PIIS002228281100263X/abstract?rss=yesAbstract: Evidence obtained in recent years indicates that, in cardiac myocytes, release of Ca2+ from the sarcoplasmic reticulum (SR) is regulated by changes in the concentration of Ca2+ within the SR. In this review, we summarize recent advances in our understanding of this regulatory role, with a particular emphasis on dynamic and local changes in SR [Ca2+]. We focus on five important questions that are to some extent unresolved and controversial. These questions concern: (1) the importance of SR [Ca2+] depletion in the termination of Ca2+ release; (2) the quantitative extent of depletion during local release events such as Ca2+ sparks; (3) the influence of SR [Ca2+] refilling on release refractoriness and the propensity for pathological Ca2+ release; (4) dynamic changes in SR [Ca2+] during propagating Ca2+ waves; and (5) the speed of Ca2+ diffusion within the SR. With each issue, we discuss data supporting alternative viewpoints, and we identify fundamental questions that are being actively investigated. We conclude with a discussion of experimental and computational advances that will help to resolve controversies. This article is part of a special issue entitled "Local Signaling in Myocytes."Highlights: ► Changes in sarcoplasmic reticulum (SR) calcium regulate calcium release in heart cells. ► Under many circumstances, regulatory changes in SR calcium are transient and local. ► Studies that established the importance of local changes in SR calcium are described. ► Unresolved and controversial issues requiring further study are discussed.Dynamic local changes in sarcoplasmic reticulum calcium: Physiological and pathophysiological rolesEric A. Sobie, W.J. Lederer10.1016/j.yjmcc.2011.06.024Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-07-11Journal of Molecular and Cellular Cardiology2011-07-11522S0022-2828(12)X0002-6Local Ca2+ Signaling304311http://www.jmmc-online.com/article/PIIS0022282811002252/abstract?rss=yesAbstract: Calmodulin (CaM) acts as a common Ca2+ sensor for many signaling pathways, transducing local Ca2+ signals into specific cellular outcomes. Many of CaM's signaling functions can be explained by its unique biochemical properties, including high and low affinity Ca2+-binding sites with slow and fast kinetics, respectively. CaM is expected to have a limited spatial range of action, emphasizing its role in local Ca2+ signaling. Interactions with target proteins further fine-tune CaM signal transduction. Here, we focus on only three specific cellular targets for CaM signaling in cardiac myocytes: the L-type Ca2+ channel, the ryanodine receptor, and the IP3 receptor. We elaborate a working hypothesis that each channel is regulated by two distinct functional populations of CaM: dedicated CaM and promiscuous CaM. Dedicated CaM is typically tethered to each channel and directly regulates channel activity. In addition, a local pool of promiscuous CaM appears poised to sense local Ca2+ signals and trigger downstream pathways such as Ca2+/CaM dependent-protein kinase II and calcineurin. Understanding how promiscuous CaM coordinates multiple distinct signaling pathways remains a challenge, but is aided by the use of mathematical modeling and a new generation of fluorescent biosensors.This article is part of a special issue entitled "Local Signaling in Myocytes."Research highlights: ► Calmodulin (CaM) acts as a local Ca2+ sensor with a limited range of action. ► Ca2+-sensitive ion channels are regulated by dedicated and promiscuous CaMs. ► CaM modulates the sensitivity of CaMKII and calcineurin to local Ca2+ signals.Calmodulin binding proteins provide domains of local Ca2+ signaling in cardiac myocytesJeffrey J. Saucerman, Donald M. Bers10.1016/j.yjmcc.2011.06.005Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-06-13Journal of Molecular and Cellular Cardiology2011-06-13522S0022-2828(12)X0002-6Local Ca2+ Signaling312316http://www.jmmc-online.com/article/PIIS0022282811001805/abstract?rss=yesAbstract: No other inorganic molecule known in biology is considered as versatile as Ca2+. In a vast majority of cell types, Ca2+ acts as a universal second messenger underlying critical cellular processes varying from gene transcription to cell death. Although the role of Ca2+ in myocyte contraction has been known for over a century, it was only more recently that this divalent cation has been implicated in mediating reactive signal transduction to promote cardiac hypertrophy. However, it remains unclear how Ca2+-dependent signaling pathways are regulated/activated in a cardiac myocyte given the prevailing conditions throughout the cytosol where Ca2+ concentration oscillates between 100nM and upwards of 1–2μM during each contractile cycle. In this review we will examine three hypotheses put forward to explain how Ca2+ might still function as a hypertrophic signaling molecule in cardiac myocytes and discuss the current literature that supports each of these views. This article is part of a special issue entitled “Local Signaling in Myocytes.”Research highlights: ► How myocytes differentiate between contractile and reactive signaling Ca2+ remains a mystery. ► We hypothesize three possibilities and discuss recent work that supports each scenario. ► We present a model in which microdomain Ca2+ and elevated diastolic Ca2+ mobilize reactive cardiac signaling.Unraveling the secrets of a double life: Contractile versus signaling Ca2+ in a cardiac myocyteSanjeewa A. Goonasekera, Jeffery D. Molkentin10.1016/j.yjmcc.2011.05.001Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-05-19Journal of Molecular and Cellular Cardiology2011-05-19522S0022-2828(12)X0002-6Local Ca2+ Signaling317322http://www.jmmc-online.com/article/PIIS0022282811003361/abstract?rss=yesAbstract: In the light of the knowledge accumulated over the years, it becomes clear that intracellular cAMP is not uniformly distributed within cardiomyocytes and that cAMP compartmentation is required for adequate processing and targeting of the information generated at the membrane. Localized cAMP signals may be generated by interplay between discrete production sites and restricted diffusion within the cytoplasm. In addition to specialized membrane structures that may limit cAMP spreading, degradation of the second messenger by cyclic nucleotide phosphodiesterases (PDEs) appears critical for the formation of dynamic microdomains that confer specificity of the response to various hormones. This review will cover the role of the different cAMP-PDE isoforms in this process. This article is part of a Special Issue entitled “Local Signaling in Myocytes.”Highlights: ► Intracellular cAMP is not uniformly distributed within cardiomyocytes. ► Cyclic AMP microdomains confer specificity of the response to various hormones. ► Degradation of cAMP by phosphodiesterases is critical for the formation of cAMP microdomains.PDEs create local domains of cAMP signalingDelphine Mika, Jérôme Leroy, Grégoire Vandecasteele, Rodolphe Fischmeister10.1016/j.yjmcc.2011.08.016Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-08-25Journal of Molecular and Cellular Cardiology2011-08-25522S0022-2828(12)X0002-6Cyclic Nucleotides and Gaseous Signaling Molecules323329http://www.jmmc-online.com/article/PIIS0022282811003178/abstract?rss=yesAbstract: Cyclic guanosine 3′5′monophosphate (cGMP) is the common downstream second messenger of natriuretic peptides and nitric oxide. In cardiac myocytes, the physiological effects of cGMP are exerted through the activation of protein kinase G (PKG) signaling, and the activation and/or inhibition of phosphodiesterases (PDEs), providing an integration point between cAMP and cGMP signals. Specificity of cGMP signals is achieved through compartmentalization of cGMP synthesis by guanylate cyclases, and cGMP hydrolysis by PDEs. Increasing evidence suggests that cGMP-dependent signaling pathways play an important role in inhibiting cardiac remodeling, through the inhibition Ca2+ handling upstream of pathological Ca2+-dependent signaling pathways. Thus, enhancing cardiac myocyte cGMP signaling represents a promising therapeutic target for treatment of cardiovascular disease. This article is part of a Special Issue entitled “Local Signaling in Myocytes.”Highlights: ► cGMP is an important intracellular second messenger in cardiac myocytes. ► cGMP signaling specificity through compartmentalization of synthesis and hydrolysis. ► cGMP signals cross-talk with cAMP signals through phosphodiesterases. ► cGMP-dependent signaling pathways inhibit cardiac remodeling.Nitric oxide synthase and cyclic GMP signaling in cardiac myocytes: From contractility to remodelingJoanna Hammond, Jean-Luc Balligand10.1016/j.yjmcc.2011.07.029Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-08-08Journal of Molecular and Cellular Cardiology2011-08-08522S0022-2828(12)X0002-6Cyclic Nucleotides and Gaseous Signaling Molecules330340http://www.jmmc-online.com/article/PIIS0022282811003828/abstract?rss=yesAbstract: Constitutive nitric oxide synthases (NOSs) are ubiquitous enzymes that play a pivotal role in the regulation of myocardial function in health and disease. The discovery of both a neuronal NOS (nNOS) and an endothelial NOS (eNOS) isoform in the myocardium and the availability of genetically modified mice with selective eNOS or nNOS gene deletion have been of crucial importance for understanding the role of constitutive nitric oxide (NO) production in the myocardium. eNOS and nNOS are homologous in structure and utilize the same co-factors and substrates; however, they differ in their subcellular localization, regulation, and downstream signaling, all of which may account for their distinct effects on excitation–contraction coupling. In particular, eNOS-derived NO has been reported to increase left ventricular (LV) compliance, attenuate beta-adrenergic inotropy and enhance parasympathetic/muscarinic responses, and mediate the negative inotropic response to β3 adrenoreceptor stimulation via cGMP-dependent signaling. Conversely, nNOS-derived NO regulates basal myocardial inotropy and relaxation by inhibiting the sarcolemmal Ca2+ current (ICa) and promoting protein kinase A-dependent phospholamban (PLN) phosphorylation, independent of cGMP. By inhibiting the activity of myocardial oxidase systems, nNOS regulates the redox state of the myocardium and contributes to maintain eNOS “coupled” activity. After myocardial infarction, up-regulation of myocardial nNOS attenuates adverse remodeling and prevents arrhythmias whereas uncoupled eNOS activity in murine models of left ventricular pressure overload accelerates the progress towards heart failure. Here we review the evidence in support of the idea that NOS subcellular localization, mode of activation, and downstream signaling account for the diverse and highly specialized actions of NO in the heart. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► Different from plasmalemmal eNOS, sarcoplasmic nNOS facilitates basal myocardial relaxation and attenuates contraction. ► nNOS promotes PKA-dependent phospholamban phosphorylation and inhibits L-type Ca2+ channel activity. ► nNOS modulates myocardial oxidases and maintains eNOS ‘coupling’ to produce NO. ► nNOS is up-regulated and translocates to sarcolemma in diseased heart and attenuates its adverse remodeling. ► eNOS is ‘uncoupled’ and contributes to oxidative stress in failing myocardium.Sub-cellular targeting of constitutive NOS in health and diseaseYin Hua Zhang, Barbara Casadei10.1016/j.yjmcc.2011.09.006Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-09-19Journal of Molecular and Cellular Cardiology2011-09-19522S0022-2828(12)X0002-6Cyclic Nucleotides and Gaseous Signaling Molecules341350http://www.jmmc-online.com/article/PIIS0022282811001817/abstract?rss=yesAbstract: The cAMP-dependent protein kinase A (PKA) is targeted to specific compartments in the cardiac myocyte by A-kinase anchoring proteins (AKAPs), a diverse set of scaffold proteins that have been implicated in the regulation of excitation–contraction coupling and cardiac remodeling. AKAPs bind not only PKA, but also a large variety of structural and signaling molecules. In this review, we discuss the basic concepts underlying compartmentation of cAMP and PKA signaling, as well as a few of the individual AKAPs that have been shown to be functionally relevant in the heart. This article is part of a Special Issue entitled "Local Signaling in Myocytes".Research highlights: ► In this review, we discuss A-kinase anchoring proteins expressed in the heart. ► AKAPs are important for cAMP compartmentation. ► AKAP scaffold proteins confer specificity and fidelity to cAMP signaling.AKAPs: The architectural underpinnings of local cAMP signalingMichael D. Kritzer, Jinliang Li, Kimberly Dodge-Kafka, Michael S. Kapiloff10.1016/j.yjmcc.2011.05.002Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-05-19Journal of Molecular and Cellular Cardiology2011-05-19522S0022-2828(12)X0002-6Cyclic Nucleotides and Gaseous Signaling Molecules351358http://www.jmmc-online.com/article/PIIS0022282811002148/abstract?rss=yesAbstract: Endogenous carbon monoxide (CO) is generated through the heme oxygenase-catalysed degradation of heme and is now established as an important, biologically active molecule capable of modulating a number of signalling pathways. Such pathways include those involving nitric oxide/guanylate cyclase, reactive oxygen species (ROS) and MAP kinases. In the heart, up-regulation of the inducible form of heme oxygenase (HO-1) following stresses such as ischemia/reperfusion provides cardioprotection, and much evidence indicates that CO accounts for many of these beneficial effects. One target of CO appears to be the L-type Ca2+ channel; CO inhibits recombinant and native forms of this cardiac channel via mitochondria-derived ROS, which likely contributes to the protective effects of CO. In stark contrast, exposure to exogenous CO is toxic: chronic, low-level exposure can lead to myocardial injury and fibrosis, whereas acute exposure is associated with life-threatening arrhythmias. The molecular mechanisms accounting for such effects remain to be elucidated, but require future study before the potentially beneficial effects of CO therapy can be safely exploited. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Research highlights: ► The protective and deleterious effects of carbon monoxide (CO) in the myocardium are considered. ► Endogenous CO is clearly protective against ischemia/reperfusion injury. ► Protective effects of CO likely involve multiple second messenger pathways and ion channels. ► At higher concentrations, CO is cardiotoxic and pro-arrhythmic. ► The pro-arrhythmic effects of CO are likely to involve regulation of alternative ion channels.Carbon monoxide: A vital signalling molecule and potent toxin in the myocardiumChris Peers, Derek S. Steele10.1016/j.yjmcc.2011.05.013Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-05-27Journal of Molecular and Cellular Cardiology2011-05-27522S0022-2828(12)X0002-6Cyclic Nucleotides and Gaseous Signaling Molecules359365http://www.jmmc-online.com/article/PIIS0022282811002719/abstract?rss=yesAbstract: Compartmentation of signalling allows multiple stimuli to achieve diverse cellular responses with only a limited pool of second messengers. This spatial control of signalling is achieved, in part, by cellular structures which bring together elements of a particular cascade. One such structure is the caveola, a flask-shaped lipid raft. Caveolae are well-recognised as signalosomes, platforms for assembly of signalling complexes of receptors, effectors and their targets, which can facilitate efficient and specific cellular responses. Here we extend this simple model and present evidence to show how the protein and lipid profiles of caveolae, as well as their characteristic morphology, define their roles in creating local signalling domains in the cardiac myocyte. This article is part of a Special Issue entitled “Local Signaling in Myocytes.”Highlights: ► Caveolae are protein compartments that control the production of cAMP and NO. ► Some signalling pathways exploit the lipid (PIP2) environment of caveolae. ► Caveolae can buffer increases in membrane tension during stretch. ► Caveolae are key components of GPCR and mechanotransductive signalling in the heart.Caveolae create local signalling domains through their distinct protein content, lipid profile and morphologyRobert D. Harvey, Sarah C. Calaghan10.1016/j.yjmcc.2011.07.007Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-07-18Journal of Molecular and Cellular Cardiology2011-07-18522S0022-2828(12)X0002-6Membrane Microdomains366375http://www.jmmc-online.com/article/PIIS0022282811003348/abstract?rss=yesAbstract: Influx of Ca2+ through L-type Ca2+ channels (LTCCs) contributes to numerous cellular processes in cardiomyocytes including excitation–contraction (EC) coupling, membrane excitability, and transcriptional regulation. Distinct subpopulations of LTCCs have been identified in cardiac myocytes, including those at dyadic junctions and within different plasma membrane microdomains such as lipid rafts and caveolae. These subpopulations of LTCCs exhibit regionally distinct functional properties and regulation, affording precise spatiotemporal modulation of L-type Ca2+ current (ICa,L). Different subcellular LTCC populations demonstrate variable rates of Ca2+-dependent inactivation and sometimes coupled gating of neighboring channels, which can lead to focal, persistent ICa,L. In addition, the assembly of spatially defined macromolecular signaling complexes permits compartmentalized regulation of ICa,L by a variety of neurohormonal pathways. For example, β-adrenergic receptor subtypes signal to different LTCC subpopulations, with β2-adrenergic activation leading to enhanced ICa,L through caveolar LTCCs and β1-adrenergic stimulation modulating LTCCs outside of caveolae. Disruptions in the normal subcellular targeting of LTCCs and associated signaling proteins may contribute to the pathophysiology of a variety of cardiac diseases including heart failure and certain arrhythmias. Further identifying the characteristic functional properties and array of regulatory molecules associated with specific LTCC subpopulations will provide a mechanistic framework to understand how LTCCs contribute to diverse cellular processes in normal and diseased myocardium. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► L-type Ca2+ channels regulate diverse cellular processes in the heart. ► Different L-type Ca2+ channel subpopulations exist in cardiomyocytes. ► Function and regulation of L-type Ca2+ channels depend on subcellular localization. ► Altered localization of L-type Ca2+ channels plays a role in heart disease.Different subcellular populations of L-type Ca2+ channels exhibit unique regulation and functional roles in cardiomyocytesJabe M. Best, Timothy J. Kamp10.1016/j.yjmcc.2011.08.014Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-08-25Journal of Molecular and Cellular Cardiology2011-08-25522S0022-2828(12)X0002-6Membrane Microdomains376387http://www.jmmc-online.com/article/PIIS0022282811002537/abstract?rss=yesAbstract: Inotropy and lusitropy in the ventricular myocyte can be efficiently induced by activation of β1-, but not β2-, adrenoceptors (ARs). Compartmentation of β2-AR-derived cAMP-dependent signalling underlies this functional discrepancy. Here we investigate the mechanism by which caveolae (specialised sarcolemmal invaginations rich in cholesterol and caveolin-3) contribute to compartmentation in the adult rat ventricular myocyte. Selective activation of β2-ARs (with zinterol/CGP20712A) produced little contractile response in control cells but pronounced inotropic and lusitropic responses in cells treated with the cholesterol-depleting agent methyl-β-cyclodextrin (MBCD). This was not linked to modulation of L-type Ca2+ current, but instead to a discrete PKA-mediated phosphorylation of phospholamban at Ser16. Application of a cell-permeable inhibitor of caveolin-3 scaffolding interactions mimicked the effect of MBCD on phosphorylated phospholamban (pPLB) during β2-AR stimulation, consistent with MBCD acting via caveolae. Biosensor experiments revealed β2-AR mobilisation of cAMP in PKA II signalling domains of intact cells only after MBCD treatment, providing a real-time demonstration of cAMP freed from caveolar constraint. Other proteins have roles in compartmentation, so the effects of phosphodiesterase (PDE), protein phosphatase (PP) and phosphoinositide-3-kinase (PI3K) inhibitors on pPLB and contraction were compared in control and MBCD treated cells. PP inhibition alone was conspicuous in showing robust de-compartmentation of β2-AR-derived signalling in control cells and a comparatively diminutive effect after cholesterol depletion. Collating all evidence, we promote the novel concept that caveolae limit β2-AR-cAMP signalling by providing a platform that not only attenuates production of cAMP but also prevents inhibitory modulation of PPs at the sarcoplasmic reticulum. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► We investigate the mechanism(s) by which caveolae compartmentalise β2-AR signalling. ► Disrupting caveolae reveals β2-AR cAMP signals in the PKA-RII compartment. ► Disrupting caveolae promotes a selective PKA-mediated phosphorylation of PLB. ► Phosphatases (PP) 1/2a (but not PDE 2/3/4) contribute to caveolar β2-AR compartmentation. ► We propose that intact caveolae attenuate cAMP production and limit inhibitory modulation of PP at the SR.Caveolae compartmentalise β2-adrenoceptor signals by curtailing cAMP production and maintaining phosphatase activity in the sarcoplasmic reticulum of the adult ventricular myocyteDavid A. MacDougall, Shailesh R. Agarwal, Elizabeth A. Stopford, Hongjin Chu, Jennifer A. Collins, Anna L. Longster, John Colyer, Robert D. Harvey, Sarah Calaghan10.1016/j.yjmcc.2011.06.014Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-06-27Journal of Molecular and Cellular Cardiology2011-06-27522S0022-2828(12)X0002-6Membrane Microdomains388400http://www.jmmc-online.com/article/PIIS0022282811002276/abstract?rss=yesAbstract: Orchestrated excitation–contraction coupling in heart muscle requires adequate spatial arrangement of systems responsible for ion movement and metabolite turnover. Co-localization of regulatory and transporting proteins into macromolecular complexes within an environment of microanatomical cell components raises intracellular diffusion barriers that hamper the mobility of metabolites and signaling molecules. Compared to substrate diffusion in the cytosol, diffusional restrictions underneath the sarcolemma are much larger and could impede ion and nucleotide movement by a factor of 103–105. Diffusion barriers thus seclude metabolites within the submembrane space enabling rapid and vectorial effector targeting, yet hinder energy supply from the bulk cytosolic space implicating the necessity for a shunting transfer mechanism. Here, we address principles of membrane protein compartmentation, phosphotransfer enzyme-facilitated interdomain energy transfer, and nucleotide signal dynamics at the subsarcolemma–cytosol interface. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► Transducers and effectors are co-localized for vectorial response to environmental signals. ► Membrane macromolecular units are secluded by diffusion barriers limiting metabolite mobility. ► Membrane complexes comprise local nucleotide sensors able to adjust energy demand. ► Phosphotransfer reactions shunt diffusion barriers and actively modulate nucleotide signals. ► Diffusion barriers permit transmission of only sustained changes in bulk energetics.Compartmentation of membrane processes and nucleotide dynamics in diffusion-restricted cardiac cell microenvironmentAlexey E. Alekseev, Santiago Reyes, Vitaly A. Selivanov, Petras P. Dzeja, Andre Terzic10.1016/j.yjmcc.2011.06.007Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-06-20Journal of Molecular and Cellular Cardiology2011-06-20522S0022-2828(12)X0002-6Metabolic Compartmentation401409http://www.jmmc-online.com/article/PIIS0022282811003336/abstract?rss=yesAbstract: AMPK is an important sensor of cellular energy levels. The aim of these studies was to investigate whether cardiac KATP channels, which couple cellular energy metabolism to membrane excitability, are regulated by AMPK activity. We investigated effects of AMPK on rat ventricular KATP channels using electrophysiological and biochemical approaches. Whole-cell KATP channel current was activated by metabolic inhibition; this occurred more rapidly in the presence of AICAR (an AMPK activator). AICAR had no effects on KATP channel activity recorded in the inside-out patch clamp configuration, but ZMP (the intracellular intermediate of AICAR) strongly activated KATP channels. An AMPK-mediated effect is demonstrated by the finding that ZMP had no effect on KATP channels in the presence of Compound C (an AMPK inhibitor). Recombinant AMPK activated Kir6.2/SUR2A channels in a manner that was dependent on the AMP concentration, whereas heat-inactivated AMPK was without effect. Using mass-spectrometry and co-immunoprecipitation approaches, we demonstrate that the AMPK α-subunit physically associates with KATP channel subunits. Our data demonstrate that the cardiac KATP channel function is directly regulated by AMPK activation. During metabolic stress, a small change in cellular AMP that activates AMPK can be a potential trigger for KATP channel opening. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Graphical abstract: Highlights: ► During metabolic impairment, a change in the ATP:ADP ratio stimulates KATP channels opening. ► The ATP:AMP ratio is an acquisitively sensitive indicator of alterations in the metabolic status. ► We show that AMP-activated protein kinase (AMPK) activity promotes KATP channel opening. ► AMPK physically interacts with KATP channel subunits, suggestive of local signaling. ► Thus, small changes in AMP may trigger KATP channel availability under ischemic conditions.AMP-activated protein kinase connects cellular energy metabolism to KATP channel functionHidetada Yoshida, Li Bao, Eirini Kefaloyianni, Eylem Taskin, Uzoma Okorie, Miyoun Hong, Piyali Dhar-Chowdhury, Michiyo Kaneko, William A. Coetzee10.1016/j.yjmcc.2011.08.013Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-08-25Journal of Molecular and Cellular Cardiology2011-08-25522S0022-2828(12)X0002-6Metabolic Compartmentation410418http://www.jmmc-online.com/article/PIIS002228281100280X/abstract?rss=yesAbstract: This review describes developments in historical perspective as well as recent results of investigations of cellular mechanisms of regulation of energy fluxes and mitochondrial respiration by cardiac work — the metabolic aspect of the Frank–Starling law of the heart. A Systems Biology solution to this problem needs the integration of physiological and biochemical mechanisms that take into account intracellular interactions of mitochondria with other cellular systems, in particular with cytoskeleton components. Recent data show that different tubulin isotypes are involved in the regular arrangement exhibited by mitochondria and ATP-consuming systems into Intracellular Energetic Units (ICEUs). Beta II tubulin association with the mitochondrial outer membrane, when co-expressed with mitochondrial creatine kinase (MtCK) specifically limits the permeability of voltage-dependent anion channel for adenine nucleotides. In the MtCK reaction this interaction changes the regulatory kinetics of respiration through a decrease in the affinity for adenine nucleotides and an increase in the affinity for creatine. Metabolic Control Analysis of the coupled MtCK–ATP Synthasome in permeabilized cardiomyocytes showed a significant increase in flux control by steps involved in ADP recycling. Mathematical modeling of compartmentalized energy transfer represented by ICEUs shows that cyclic changes in local ADP, Pi, phosphocreatine and creatine concentrations during contraction cycle represent effective metabolic feedback signals when amplified in the coupled non-equilibrium MtCK–ATP Synthasome reactions in mitochondria. This mechanism explains the regulation of respiration on beat to beat basis during workload changes under conditions of metabolic stability. This article is part of a Special Issue entitled “Local Signaling in Myocytes.”Highlights: ► The mechanism of linear dependence of mitochondrial respiration on heart work is described. ► The role of tubulin and plectin in formation of Intracellular Energetic Units. ► The mitochondrial tubulin beta II and its role in respiration regulation are described. ► Feedback metabolic regulation on beat to beat basis is described.Intracellular Energetic Units regulate metabolism in cardiac cellsValdur Saks, Andrey V. Kuznetsov, Marcela Gonzalez-Granillo, Kersti Tepp, Natalja Timohhina, Minna Karu-Varikmaa, Tuuli Kaambre, Pierre Dos Santos, François Boucher, Rita Guzun10.1016/j.yjmcc.2011.07.015Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-07-27Journal of Molecular and Cellular Cardiology2011-07-27522S0022-2828(12)X0002-6Metabolic Compartmentation419436http://www.jmmc-online.com/article/PIIS0022282811003154/abstract?rss=yesAbstract: The aim of this study was to investigate the possible role of tubulin βII, a cytoskeletal protein, in regulation of mitochondrial oxidative phosphorylation and energy fluxes in heart cells. This isotype of tubulin is closely associated with mitochondria and co-expressed with mitochondrial creatine kinase (MtCK). It can be rapidly removed by mild proteolytic treatment of permeabilized cardiomyocytes in the absence of stimulatory effect of cytochrome c, that demonstrating the intactness of the outer mitochondrial membrane. Contrary to isolated mitochondria, in permeabilized cardiomyocytes (in situ mitochondria) the addition of pyruvate kinase (PK) and phosphoenolpyruvate (PEP) in the presence of creatine had no effect on the rate of respiration controlled by activated MtCK, showing limited permeability of voltage-dependent anion channel (VDAC) in mitochondrial outer membrane (MOM) for ADP regenerated by MtCK. Under normal conditions, this effect can be considered as one of the most sensitive tests of the intactness of cardiomyocytes and controlled permeability of MOM for adenine nucleotides. However, proteolytic treatment of permeabilized cardiomyocytes with trypsin, by removing mitochondrial βII tubulin, induces high sensitivity of MtCK-regulated respiration to PK–PEP, significantly changes its kinetics and the affinity to exogenous ADP. MtCK coupled to ATP synthasome and to VDAC controlled by tubulin βII provides functional compartmentation of ATP in mitochondria and energy channeling into cytoplasm via phosphotransfer network. Therefore, direct transfer of mitochondrially produced ATP to sites of its utilization is largely avoided under physiological conditions, but may occur in pathology when mitochondria are damaged. This article is part of a Special Issue entitled ‘‘Local Signaling in Myocytes’’.Highlights: ► The role of mitochondrial tubulin beta II and its role in respiration regulation are described. ► Mitochondrial tubulin beta II is rapidly removed by short proteolytic treatment of permeabilized cardiomyocytes. ► Removal of tubulin increases the permeability of outer mitochondrial membrane for ADP. ► Quality tests for isolated cardiomyocytes are described.Studies of the role of tubulin beta II isotype in regulation of mitochondrial respiration in intracellular energetic units in cardiac cellsMarcela Gonzalez-Granillo, Alexei Grichine, Rita Guzun, Yves Usson, Kersti Tepp, Vladimir Chekulayev, Igor Shevchuk, Minna Karu-Varikmaa, Andrey V. Kuznetsov, Michael Grimm, Valdur Saks, Tuuli Kaambre10.1016/j.yjmcc.2011.07.027Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-08-08Journal of Molecular and Cellular Cardiology2011-08-08522S0022-2828(12)X0002-6Metabolic Compartmentation437447http://www.jmmc-online.com/article/PIIS002228281100383X/abstract?rss=yesAbstract: Mitochondria are highly metabolically active cell organelles that not only act as the powerhouse of the cell by supplying energy through ATP production, but also play a destructive role by initiating cell death pathways. Growing evidence recognizes that mitochondrial dysfunction is one of the major causes of cardiovascular disease. Under de-energized conditions, slowing of adenine nucleotide transport in and out of the mitochondria significantly attenuates myocardial ischemia–reperfusion injury. The purpose of this review is to elaborate on and update the mechanistic pathways which may explain how altered adenine nucleotide transport can influence cardiovascular function. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► Role of mitochondria in myocardial ischemia–reperfusion injury. ► Mitochondrial adenine nucleotide transport in ischemia–reperfusion injury. ► Role of voltage dependent anion channel (VDAC) in mitochondrial ATP transport. ► Mitochondrial ATP transport and mitochondrial permeability transition pore (mPTP).Mitochondrial adenine nucleotide transport and cardioprotectionSamarjit Das, Charles Steenbergen10.1016/j.yjmcc.2011.09.007Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-09-19Journal of Molecular and Cellular Cardiology2011-09-19522S0022-2828(12)X0002-6Metabolic Compartmentation448453http://www.jmmc-online.com/article/PIIS0022282811004202/abstract?rss=yesAbstract: Cardiac arrhythmias can cause sudden cardiac death (SCD) and add to the current heart failure (HF) health crisis. Nevertheless, the pathological processes underlying arrhythmias are unclear. Arrhythmic conditions are associated with systemic and cardiac oxidative stress caused by reactive oxygen species (ROS). In excitable cardiac cells, ROS regulate both cellular metabolism and ion homeostasis. Increasing evidence suggests that elevated cellular ROS can cause alterations of the cardiac sodium channel (Nav1.5), abnormal Ca2+ handling, changes of mitochondrial function, and gap junction remodeling, leading to arrhythmogenesis. This review summarizes our knowledge of the mechanisms by which ROS may cause arrhythmias and discusses potential therapeutic strategies to prevent arrhythmias by targeting ROS and its consequences. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► Cardiomyopathies are associated with metabolic stress, oxidative stress, and arrhythmic risk. ► Oxidative stress alters ion channels, Ca2+ handling, and gap junctions, possibly explaining the arrhythmic risk. ► Anti-oxidants may be useful anti-arrhythmic drugs. ► Highlights ROS mediate arrhythmogenesis through the alteration of ion homeostasis and structural remodeling.Metabolic stress, reactive oxygen species, and arrhythmiaEuy-Myoung Jeong, Man Liu, Megan Sturdy, Ge Gao, Susan T. Varghese, Ali A. Sovari, Samuel C. Dudley10.1016/j.yjmcc.2011.09.018Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-09-26Journal of Molecular and Cellular Cardiology2011-09-26522S0022-2828(12)X0002-6Metabolic Compartmentation454463http://www.jmmc-online.com/article/PIIS002228281100335X/abstract?rss=yesAbstract: Post-infarct remodeling is associated with the upregulation of the receptor for advanced glycation end products (RAGE), the induction of its ligand the calcium binding protein S100B and the release of the potent endothelial-cell specific mitogen vascular endothelial growth factor (VEGF). To determine a possible functional interaction between S100B, RAGE and VEGF we stimulated rat neonatal cardiac myocyte cultures transfected with either RAGE or a dominant-negative cytoplasmic deletion mutant of RAGE with S100B for 48h. Under baseline conditions, cardiac myocytes express low levels of RAGE and VEGF and secrete VEGF in the medium as measured by ELISA. In RAGE overexpressing myocytes, S100B (100nM) resulted in increases in VEGF mRNA, VEGF protein, VEGF secretion, and activation of the transcription factor NF-κB. Pre-treatment of RAGE overexpressing myocytes with the NF-κB inhibitor caffeic acid phenethyl ester inhibited increases in VEGF mRNA, VEGF protein and VEGF in the medium by S100B. In myocytes expressing dominant-negative RAGE, S100B did not induce VEGF mRNA, VEGF protein, VEGF secretion or NF-κB activation. In culture, rat neonatal and adult cardiac fibroblasts undergo phenotypic transition to myofibroblasts. Treatment of neonatal and adult myofibroblasts with VEGF (10ng/mL) induces VEGFR-2 (flk-1/KDR) tyrosine kinase phosphorylation, ERK1/2 phosphorylation and myofibroblast proliferation. Together these data demonstrate that secreted VEGF by cardiac myocytes in response to S100B via RAGE ligation induces myofibroblast proliferation potentially contributing to scar formation observed in infarcted myocardium. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► We determined an interaction between S100B and vascular endothelial growth factor. ► In rat cardiocyte cultures, S100B increased VEGF mRNA, protein, and secretion. ► In culture, rat cardiac fibroblasts undergo phenotypic transition to myofibroblasts. ► VEGF induces via VEGFR-2, ERK1/2 phosphorylation and myofibroblast proliferation. ► Myofibroblast proliferation contributes to scar formation in infarcted myocardium.S100B-RAGE dependent VEGF secretion by cardiac myocytes induces myofibroblast proliferationJames N. Tsoporis, Shehla Izhar, Gerald Proteau, Graham Slaughter, Thomas G. Parker10.1016/j.yjmcc.2011.08.015Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-08-25Journal of Molecular and Cellular Cardiology2011-08-25522S0022-2828(12)X0002-6Autocrine and Paracrine Signaling in the Heart464473http://www.jmmc-online.com/article/PIIS0022282811003841/abstract?rss=yesAbstract: Adiponectin is a cardioprotective adipokine derived predominantly from visceral fat. We recently demonstrated that exogenous adiponectin induces vascular smooth muscle cell (VSMC) differentiation via repression of mTORC1 and FoxO4. Here we report for the first time that VSMC express and secrete adiponectin, which acts in an autocrine and paracrine manner to regulate VSMC contractile phenotype. Adiponectin was found to be expressed in human coronary artery and mouse aortic VSMC. Importantly, siRNA knock-down of endogenous adiponectin in VSMC significantly reduced the expression of VSMC contractile proteins. Contractile protein deficiency was also observed in primary VSMC isolated from Adiponectin−/− mice. This deficiency could be rescued by culturing Adiponectin−/− VSMC in conditioned media from wild type (WT) VSMC. Moreover, the paracrine effect of VSMC-derived adiponectin was confirmed as adiponectin neutralizing antibody blocked the rescue. Overexpressed adiponectin also exerted paracrine effects on neighboring untransfected VSMC, which was also blocked by adiponectin neutralizing antibody. Interestingly, adiponectin expression was inducible by the PPARγ agonist rosiglitazone. Our data support an important role for VSMC-derived adiponectin in maintaining VSMC contractile phenotype, contributing to critical cardioprotective functions in the vascular wall. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Graphical abstract: Highlights: ► Vascular smooth muscle cells synthesize and secrete adiponectin. ► VSMC-derived adiponectin is upregulated by PPARγ agonists. ► VSMC-derived adiponectin is required for contractile protein expression. ► VSMC-derived adiponectin acts in an autocrine and paracrine fashion.Vascular smooth muscle cell-derived adiponectin: A paracrine regulator of contractile phenotypeMin Ding, Ana Catarina Carrão, Robert J. Wagner, Yi Xie, Yu Jin, Eva M. Rzucidlo, Jun Yu, Wei Li, George Tellides, John Hwa, Tamar R. Aprahamian, Kathleen A. Martin10.1016/j.yjmcc.2011.09.008Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-09-19Journal of Molecular and Cellular Cardiology2011-09-19522S0022-2828(12)X0002-6Autocrine and Paracrine Signaling in the Heart474484http://www.jmmc-online.com/article/PIIS0022282811002604/abstract?rss=yesAbstract: Focal adhesion kinase (FAK), a broadly expressed non-receptor tyrosine kinase which transduces signals from integrins, growth and hormonal factors, is a key player in many fundamental biological processes and functions, including cell adhesion, migration, proliferation and survival. The involvement of FAK in this range of functions supports its role in important aspects of organismal development and disease, such as central nervous system and cardiovascular development, cancer, cardiac hypertrophy and tissue fibrosis. Many functions of FAK are correlated with its tyrosine kinase activity, which is temporally and spatially controlled by complex intra-molecular autoinhibitory conformation and inter-molecular interactions with protein and lipid partners. The inactivation of FAK in mice results in embryonic lethality attributed to the lack of proper development and function of the heart. Accordingly, embryonic FAK myocyte-specific knockout mice display lethal cardiac defects such as thin ventricle wall and ventricular septum defects. Emerging data also support a role for FAK in the reactive hypertrophy and failure of adult hearts. Moreover, the mechanisms that regulate FAK in differentiated cardiac myocytes to biomechanical stress and soluble factors are beginning to be revealed and are discussed here together with data that connect FAK to its downstream effectors. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► FAK regulates cell adhesion, migration, proliferation and survival. ► The many FAK functions are critical for organismal development and disease. ► Emerging data imply FAK in cardiac development, hypertrophy and failure. ► Therapies to inhibit FAK may prove to be an alternative to treat cardiac diseases.Focal adhesion kinase — The basis of local hypertrophic signaling domainsK.G. Franchini10.1016/j.yjmcc.2011.06.021Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-07-04Journal of Molecular and Cellular Cardiology2011-07-04522S0022-2828(12)X0002-6Local Signaling in Hypertrophy and Failure485492http://www.jmmc-online.com/article/PIIS0022282811004421/abstract?rss=yesAbstract: The heart responds to sustained overload by hypertrophic growth in which the myocytes distinctly thicken or elongate on increases in systolic or diastolic stress. Though potentially adaptive, hypertrophy itself may predispose to cardiac dysfunction in pathological settings. The mechanisms underlying the diverse morphology and outcomes of hypertrophy are uncertain. Here we used a focal adhesion kinase (FAK) cardiac-specific transgenic mice model (FAK-Tg) to explore the function of this non-receptor tyrosine kinase on the regulation of myocyte growth. FAK-Tg mice displayed a phenocopy of concentric cardiac hypertrophy, reflecting the relative thickening of the individual myocytes. Moreover, FAK-Tg mice showed structural, functional and molecular features of a compensated hypertrophic growth, and preserved responses to chronic pressure overload. Mechanistically, FAK overexpression resulted in enhanced myocardial FAK activity, which was proven by treatment with a selective FAK inhibitor to be required for the cardiac hypertrophy in this model. Our results indicate that upregulation of FAK does not affect the activity of Src/ERK1/2 pathway, but stimulated signaling by a cascade that encompasses PI3K, AKT, mTOR, S6K and rpS6. Moreover, inhibition of the mTOR complex by rapamycin extinguished the cardiac hypertrophy of the transgenic FAK mice. These findings uncover a unique role for FAK in regulating the signaling mechanisms that governs the selective myocyte growth in width, likely controlling the activity of PI3K/AKT/mTOR pathway, and suggest that FAK activation could be important for the adaptive response to increases in cardiac afterload. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► Hypertrophy can be adaptive or pathological. ► Cardiac myocyte-FAK overexpression in mice induced compensated cardiac hypertrophy. ► Upregulation of FAK was accompanied by activation of PI3K, AKT, mTOR, S6K and rpS6. ► Inhibition of the mTOR complex by rapamycin extinguished the cardiac hypertrophy. ► FAK activation may be important for the adaptive responses to increases in cardiac afterload.Focal adhesion kinase governs cardiac concentric hypertrophic growth by activating the AKT and mTOR pathwaysC.F.M.Z. Clemente, J. Xavier-Neto, A.P. Dalla Costa, S.R. Consonni, J.E. Antunes, S.A. Rocco, M.B. Pereira, C.C. Judice, B. Strauss, P.P. Joazeiro, J.R. Matos-Souza, K.G. Franchini10.1016/j.yjmcc.2011.10.015Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-10-28Journal of Molecular and Cellular Cardiology2011-10-28522S0022-2828(12)X0002-6Local Signaling in Hypertrophy and Failure493501http://www.jmmc-online.com/article/PIIS0022282811003075/abstract?rss=yesAbstract: The serotonin 5-HT2A receptor belongs to the G-protein-coupled receptors (GPCRs) superfamily and mediates the hypertrophic response to serotonin (5-HT) in cardiac myocytes. At present the regulatory mechanisms of 5-HT2A receptor-induced myocyte hypertrophy are not fully understood. The localization and the compartmentation of GPCRs within specialized membrane microdomains are known to modulate their signalling pathway. Therefore, we hypothesized that caveolae microdomains and caveolin-3, the predominant isoform of cardiac caveolae, might be regulators of 5-HT2A receptor signalling. We demonstrate that 5-HT2A receptors interact with caveolin-3 upon 5-HT stimulation and traffic into caveolae membrane microdomains. We provide evidence that caveolin-3 knockdown abolishes the redistribution of 5-HT2A receptors into caveolae and enhances 5-HT2A receptor-induced myocyte hypertrophic markers such as cell size, protein synthesis and ANF gene expression. Importantly, we demonstrate that caveolin-3 and caveolae structures are negative regulators of 5-HT2A receptor-induced nuclear factor of activated T cells (NFAT) transcriptional activation. Taken together, our data demonstrate that caveolin-3 and caveolae microdomains are important regulators of the hypertrophic response induced by 5-HT2A receptors. These findings thus open new insights to target heart hypertrophy under the enhanced serotonin system. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► We show that 5-HT2A receptors/caveolin-3 interaction increases upon agonist exposure. ► 5-HT2A receptors stimulated with 5-HT traffic into caveolae microdomains. ► Caveolin-3 silencing enhances myocyte hypertrophy induced by 5-HT2A receptors. ► Caveolin-3 inhibits NFAT activation involved in 5-HT2A receptor-mediated hypertrophy.Serotonin 5-HT2A receptor-mediated hypertrophy is negatively regulated by caveolin-3 in cardiomyoblasts and neonatal cardiomyocytesJeanne Mialet-Perez, Romina D'Angelo, Christelle Villeneuve, Catherine Ordener, Anne Nègre-Salvayre, Angelo Parini, Cécile Vindis10.1016/j.yjmcc.2011.07.019Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-07-29Journal of Molecular and Cellular Cardiology2011-07-29522S0022-2828(12)X0002-6Local Signaling in Hypertrophy and Failure502510http://www.jmmc-online.com/article/PIIS0022282811002239/abstract?rss=yesAbstract: Here we reveal that the characterization of large-scale re-arrangements of signaling scaffolds induced by heart failure can serve as a novel concept to identify more specific therapeutic targets. In the mammalian heart, the cAMP pathway, with the cAMP-dependent protein kinase (PKA) in a central role, acts directly downstream of adrenergic receptors to mediate cardiac contractility and rhythm. Heart failure, characterized by severe alterations in adrenergic stimulation is, amongst other interventions, often treated with β-blockers. Contrasting results, however, have shown both beneficial and detrimental effects of decreased cAMP levels in failing hearts. We hypothesize that the origin of this behavior lies in the complex spatiotemporal organization of the regulatory subunit of PKA (PKA-R), which associates tightly with various A-kinase anchoring proteins (AKAPs) to specifically localize PKA's activity. Using chemical proteomics directly applied to human patient and control heart tissue we demonstrate that the association profile of PKA-R with several AKAPs is severely altered in the failing heart, for instance effecting the interaction between PKA and the novel AKAP SPHKAP was 6-fold upregulated upon failing heart conditions. Also a significant increase in captured cGMP-dependent protein kinase (PKG) and phosphodiesterase 2 (PDE2) was observed. The observed altered profiles can already explain many aspects of the aberrant cAMP-response in the failing human heart, validating that this dataset may provide a resource for several novel, more specific, treatment options. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.Highlights: ► Failing hearts have a severely altered complement of PKA-AKAP signaling nodes. ► Altered PKA-AKAP signaling nodes explain several aspects of the failing phenotype. ► A chemical proteomics strategy reveals aberrant signaling at single AKAP resolution. ► Chemical proteomics identifies novel therapeutic targets for heart failure.Reorganized PKA-AKAP associations in the failing human heartThin-Thin Aye, Siddarth Soni, Toon A.B. van Veen, Marcel A.G. van der Heyden, Salvatore Cappadona, Andras Varro, Roel A. de Weger, Nicolaas de Jonge, Marc A. Vos, Albert J.R. Heck, Arjen Scholten10.1016/j.yjmcc.2011.06.003Journal of Molecular and Cellular Cardiology 52, 2 (2012)2011-06-13Journal of Molecular and Cellular Cardiology2011-06-13522S0022-2828(12)X0002-6Local Signaling in Hypertrophy and Failure511518