Abstract P144: Local Signaling And Cardiac Hypertrophy:specificity In The Face Of Pleiotropy

Hypertension ◽  
2021 ◽  
Vol 78 (Suppl_1) ◽  
Author(s):  
Naveed Aslam
Keyword(s):  
Cardiac Hypertrophy ◽  
Mapk Pathway ◽  
Mechanistic Model ◽  
Second Messenger ◽  
Pathological State ◽  
Activated T Cells ◽  
Specific Domain ◽  
Bidirectional Regulation ◽  
Anchoring Protein ◽  
Camp Levels

Rationale: Most likely, the overall myocyte cell growth during the pathological state of cardiac hypertrophy is regulated by a local muscle A-kinase anchoring protein β (mAKAPβ) complex. The mAKAPβ may act as a significant coordinator of myocyte hypertrophic signals. It may critically integrate the hypertrophic signals due to β-adrenergic and leukemia inhibitory factor (LIF)/gp-130 receptor stimulation. Observations suggest that mAKAPβ signalosome may act as a gate-keeper for regulating nuclear factor of activated T cells (NFATc) activity and nuclear localization of this complex might be directly linked to the induction of cardiac hypertrophy. The mAKAPβ complex might function through modulating the profiles of a local cyclic adenosine 3’,5’ monophosphate (cAMP) microdomain at perinuclear region in cardiomyocytes. The acute stimulation of cAMP may be beneficial for the heart, whereas chronic stimulation might cause damage. The transition between the chronic and acute function of cAMP is probably modulated by the ability of myocytes to tightly regulate the cAMP levels in local microdomains across the cell. Any dysfunction in this process may lead to net accumulation and a global rise of cAMP levels, leading to deleterious effects on the heart. Objective: cAMP is a single messenger but delivers multiple messages in myocytes. How is this managed? Here, we aim to investigate a key question that how mAKAPβ signalosome might ensure the microdomain specificity despite the pleiotropic nature of the second messenger. Methods and Results: Our results may explain how, in the context of hypertrophy, mAKAPβ complex coordinates the interactions between two coupled cAMP-induced feedback loops and LIF-induced activation of the MAPK pathway. Our results may also explain that mAKAPβ complex functions through anchoring protein kinase A (PKA) and ERK5 in the signalosome thus, modulating the bidirectional regulation of phosphodiesterase and hence the control of localized cAMP metabolism as well as the shape and temporal profile of the second messenger in a specific domain. Conclusion: Here, we propose a mechanistic model which suggests that stress-induced reprofiling of cAMP flux at discrete cellular locations may lead to cardiovascular disease.

Abstract 837: Beta1 And Beta2 Adrenergic Receptor Transgenic Mice Display Distinct MicroRNA Expression Patterns That Converge On The Hypertrophic Signature

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Danish Sayed ◽  
Shweta Rane ◽  
Leng-Yi Chen ◽  
Minzhen He ◽  
Jacqueline Lypowy ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Adrenergic Receptor ◽  
Mapk Pathway ◽  
Expression Patterns ◽  
Pressure Overload ◽  
Mapk Signaling ◽  
Compensatory Hypertrophy ◽  
Over Expression ◽  
Mrna Targets ◽  
Dose Dependent

MicroRNA (miRNA) are ~22 ribonucleotides-long, with a potential to recognize multiple mRNA targets guided by sequence complimentarity. This class of molecules is functionally versatile, with the capacity to specifically inhibit translation, as well as, induce mRNA degradation, through targeting the 3′-untranslated regions. The levels of individual miRNA vary under different developmental, biological, or pathological conditions, thus, implicating them in normal and pathological cellular attributes. We have previously reported a miRNA signature that distinguishes pressure-overload compensatory hypertrophy by recapitulating the neonatal pattern. We hypothesized that this ’signature’ might aid in discriminating the underlying molecular differences in genetic models of cardiac hypertrophy, as seen in the beta1 and 2 adrenergic receptor (B1AR and B2AR) transgenic (Tg) mice. To address this, we used microarray analysis of RNA isolated from the hearts of 3 months old B1AR and B2AR mice. In general, while both mice exhibited an overlap with the hypertrophy signature including, upregulation of miR-21 and downregulation of miR-133a, miR-133b, and miR-185, the B2-AR Tg exhibited a more extensive overlap with the hypertrophy pattern, which further included upregulation of miR-199a*, miR-214, and miR-15b. To understand the functional significance of these miRNA in myocyte hypertrophy, we cloned them and their anti-sense sequences into adenoviral vectors. Significantly, over-expression miR-21 resulted in a, dose-dependent, branching (sprouting) of the cells. Computational predictions by ’TargetScanS’ identified sprouty as potential target. Subsequently, we confirmed down-regulation of sprouty by over-expression of miR-21 and vice versa. Sprouty is a known inhibitor of the Ras-MAPK signaling pathway and is, concordantly, downregulated in many forms of cancer. In the heart, sprouty has been suggested to control myocyte size and vascularization during cardiac hypertrophy. Thus, we propose that B1AR and B2AR Tg models exhibit distinct miRNA profiles that converge on that of pressure-overload cardiac hypertrophy. Moreover, the commonly over-expressed miR-21 plays a role in downregulating sprouty, an antagonist of the Ras-MAPK pathway.

scholarly journals Single nucleotide polymorphisms alter kinase anchoring and the subcellular targeting of A-kinase anchoring proteins

2018 ◽  
Vol 115 (49) ◽  
pp. E11465-E11474 ◽  
Author(s):  
F. Donelson Smith ◽  
Mitchell H. Omar ◽  
Patrick J. Nygren ◽  
Joseph Soughayer ◽  
Naoto Hoshi ◽  
...  
Keyword(s):  
Solid Phase ◽  
Second Messenger ◽  
Nuclear Accumulation ◽  
Nucleotide Polymorphisms ◽  
Binding Assays ◽  
Subcellular Targeting ◽  
Regulatory Subunits ◽  
Anchoring Proteins ◽  
Anchoring Protein ◽  
Second Messenger Signaling

A-kinase anchoring proteins (AKAPs) shape second-messenger signaling responses by constraining protein kinase A (PKA) at precise intracellular locations. A defining feature of AKAPs is a helical region that binds to regulatory subunits (RII) of PKA. Mining patient-derived databases has identified 42 nonsynonymous SNPs in the PKA-anchoring helices of five AKAPs. Solid-phase RII binding assays confirmed that 21 of these amino acid substitutions disrupt PKA anchoring. The most deleterious side-chain modifications are situated toward C-termini of AKAP helices. More extensive analysis was conducted on a valine-to-methionine variant in the PKA-anchoring helix of AKAP18. Molecular modeling indicates that additional density provided by methionine at position 282 in the AKAP18γ isoform deflects the pitch of the helical anchoring surface outward by 6.6°. Fluorescence polarization measurements show that this subtle topological change reduces RII-binding affinity 8.8-fold and impairs cAMP responsive potentiation of L-type Ca2+ currents in situ. Live-cell imaging of AKAP18γ V282M-GFP adducts led to the unexpected discovery that loss of PKA anchoring promotes nuclear accumulation of this polymorphic variant. Targeting proceeds via a mechanism whereby association with the PKA holoenzyme masks a polybasic nuclear localization signal on the anchoring protein. This led to the discovery of AKAP18ε: an exclusively nuclear isoform that lacks a PKA-anchoring helix. Enzyme-mediated proximity-proteomics reveal that compartment-selective variants of AKAP18 associate with distinct binding partners. Thus, naturally occurring PKA-anchoring-defective AKAP variants not only perturb dissemination of local second-messenger responses, but also may influence the intracellular distribution of certain AKAP18 isoforms.

Abstract 197: Overexpression of the Na+/K+ ATPase a2 But Not a1 Isoform Attenuates Pathological Cardiac Hypertrophy and Remodeling

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Robert N Correll ◽  
Petra Eder ◽  
Adam R Burr ◽  
Sanda Despa ◽  
Jennifer Davis ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Protective Effect ◽  
Pressure Overload ◽  
Negative Regulator ◽  
Protective Measure ◽  
Nuclear Factor ◽  
Activated T Cells ◽  
Reverse Mode ◽  
Pathological Cardiac Hypertrophy ◽  
Protein Kinase Cα

The Na+/K+ ATPase (NKA) directly regulates intracellular Na+ levels, which indirectly regulate Ca2+ levels by controlling flux through the Na+/Ca2+ exchanger (NCX1). Elevated Na+ levels have been reported during heart failure, which permits some degree of reverse mode Ca2+ entry through NCX1 and less efficient Ca2+ clearance. To determine if lower intracellular Na+ levels would enhance forward-mode Ca2+ clearance and prevent reverse-mode Ca2+ entry through NCX1 as a protective measure, we generated cardiac-specific transgenic mice overexpressing either the NKA-α1 or α2 isoform and subjected them to pressure overload hypertrophic stimulation. We found that while increased expression of the NKA-α1 isoform had no protective effect, overexpression of NKA-α2 significantly decreased cardiac hypertrophy after pressure overload at 2, 10 and 16 weeks of stimulation. Remarkably, total NKA protein expression was not altered in either of these 2 transgenic models, as increased expression of one isoform led to a concomitant decrease in the other endogenous isoform. While total NKA ATPase activity and intracellular Na+ levels were unchanged in either overexpression model, and both showed reduced Ca2+ transient amplitudes and sarcoplasmic reticulum Ca2+ load, only NKA-α2 overexpression led to faster removal of bulk Ca2+ from the cytosol in a manner requiring NCX1 activity. This increased NCX1 activity, though correlated with improved outcome after pressure overload, did not affect signaling through Ca2+-sensitive signaling pathways such as calcineurin/nuclear factor of activated T-cells, Ca2+/calmodulin-dependent kinase II, or protein kinase Cα. Overexpression of NKA-α2 did, however, result in reduced expression of phospholemman (PLM), an inhibitor of NKA activity (when dephosphorylated) and NCX1 activity (when phosphorylated). Our results suggest that the protective effect produced by increased expression of NKA-α2 after pressure overload is likely due to: 1) Na+ regulation in a unique signaling microdomain distinct from NKA-α1, and 2) downregulation of PLM expression that removes a negative regulator of NCX1 activity, both leading to preservation of forward-mode NCX1 activity during disease, in association with optimized cardiac function.

Abstract 159: Cardiac Hypertrophy and Sudden Death in a Mouse Model of STIM1 Overexpression

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Sanjeewa A Goonasekera ◽  
Jop van Berlo ◽  
Adam R Burr ◽  
Robert N Correll ◽  
Allen J York ◽  
...  
Keyword(s):  
Mouse Model ◽  
Cardiac Hypertrophy ◽  
Molecular Mechanisms ◽  
Ventricular Myocytes ◽  
Interstitial Fibrosis ◽  
Heart Weight ◽  
Activated T Cells ◽  
Lung Weight ◽  
Tibia Length

Background: STIM1, an ER/SR resident Ca 2+ sensing protein regulates Ca 2+ entry following internal Ca 2+ store depletion in a broad range of tissues and cell types. However their putative roles in excitable tissue such as cardiac myocytes is uncertain. Results: Here we generated a mouse model of STIM1 overexpression in cardiac and skeletal muscle. Western blot analysis suggested approximately 4-6 fold STIM1 overexpression in Tg mouse hearts compared to Ntg littermates. Immunocytochemistry carried out in ventricular myocytes revealed that STIM1 and the cardiac ryanodine receptor (RyR2) co-localize. Functionally, the amplitude of Ca 2+ entry following SR Ca 2+ depletion was 2-fold greater in myocytes isolated from STIM1 Tg mice compared to NTg littermates. Echocardiographic analysis in STIM1 Tg mice showed age dependent remodeling of the myocardium with a significant decrease in fractional shortening at 16 weeks of age (14.4.5±3.8 in STIM1 Tg vs. 36.9±1.5 in Ntg). These changes were accompanied by a significant increase in heart weight to tibia length (13.6 +/- 1.4 vs 6.5 +/- 0.24) and increased lung weight to tibia length ratio (11.6+/- 2.1 vs 8.1 +/- 0.38) in STIM1 Tg mice compared to Ntg littermates. Photometry experiments in isolated ventricular myocytes demonstrated significantly increased Ca 2+ transient amplitude with an unexpected decrease in the SR Ca 2+ load associated with STIM1 overexpression. In addition transgenic mice showed increased calcineurin-nuclear factor of activated T cells (NFAT) activation in vivo, increased CaMKII activity, interstitial fibrosis and exaggerated hypertrophy following two weeks of neuroendocrine agonist or pressure overload stimulation. Conclusion: Our observations suggest that STIM1 overexpression by itself can lead to cardiac hypertrophy and contribute to pathological cardiac remodeling and possibly sudden cardiac death. The molecular mechanisms underlying these phenomena are currently under investigation.

scholarly journals LIM and Cysteine-Rich Domains 1 Regulates Cardiac Hypertrophy by Targeting Calcineurin/Nuclear Factor of Activated T Cells Signaling

Hypertension ◽  
2010 ◽  
Vol 55 (2) ◽  
pp. 257-263 ◽  
Author(s):  
Zhou-Yan Bian ◽  
He Huang ◽  
Hong Jiang ◽  
Di-Fei Shen ◽  
Ling Yan ◽  
...  
Keyword(s):  
T Cells ◽  
Cardiac Hypertrophy ◽  
Nuclear Factor ◽  
Activated T Cells

scholarly journals MicroRNA-1 suppresses cardiac hypertrophy by targeting nuclear factor of activated T cells cytoplasmic 3

2012 ◽  
Vol 12 (6) ◽  
pp. 8282-8288 ◽  
Author(s):  
HONGLEI YIN ◽  
LIHUA ZHAO ◽  
SHAOLI ZHANG ◽  
YAN ZHANG ◽  
SUYANG LEI
Keyword(s):  
T Cells ◽  
Cardiac Hypertrophy ◽  
Nuclear Factor ◽  
Activated T Cells

scholarly journals Second-messenger regulation of receptor association with clathrin-coated pits: a novel and selective mechanism in the control of CD4 endocytosis.

1997 ◽  
Vol 8 (7) ◽  
pp. 1377-1389 ◽  
Author(s):  
M Foti ◽  
J L Carpentier ◽  
C Aiken ◽  
D Trono ◽  
D P Lew ◽  
...  
Keyword(s):  
Myeloid Cells ◽  
Myeloid Cell ◽  
Insulin Receptors ◽  
Fluid Phase ◽  
Second Messenger ◽  
Surface Expression ◽  
Ultrastructural Level ◽  
Immunoglobulin Superfamily ◽  
Coated Pits ◽  
Camp Levels

CD4, a member of the immunoglobulin superfamily, is not only expressed in T4 helper lymphocytes but also in myeloid cells. Receptor-mediated endocytosis plays a crucial role in the regulation of surface expression of adhesion molecules such as CD4. In T lymphocytes p56lck, a CD4-associated tyrosine kinase, prevents CD4 internalization, but in myeloid cells p56lck is not expressed and CD4 is constitutively internalized. In this study, we have investigated the role of cyclic AMP (cAMP) in the regulation of CD4 endocytosis in the myeloid cell line HL-60. Elevations of cellular cAMP were elicited by 1) cholera toxin, 2) pertussis toxin, 3) forskolin and IBMX, 4) NaF, or 5) the physiological receptor agonist prostaglandin E1. All five interventions led to an inhibition of CD4 internalization. Increased cAMP levels did not inhibit endocytosis per se, because internalization of insulin receptors and transferrin receptors and fluid phase endocytosis were either unchanged or slightly enhanced. The mechanism of cAMP inhibition was further analyzed at the ultrastructural level. CD4 internalization, followed either by quantitative electron microscopy autoradiography or by immunogold labeling, showed a rapid and temperature-dependent association of CD4 with clathrin-coated pits in control cells. This association was markedly inhibited in cells with elevated cAMP levels. Thus these findings suggest a second-messenger regulation of CD4 internalization through an inhibition of CD4 association with clathrin-coated pits in p56lck-negative cells.

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