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1.
J Nanobiotechnology ; 22(1): 132, 2024 Mar 26.
Article in English | MEDLINE | ID: mdl-38532378

ABSTRACT

BACKGROUND: Cardiovascular diseases (CVDs) have the highest mortality worldwide. Human pluripotent stem cells (hPSCs) and their cardiomyocyte derivatives (hPSC-CMs) offer a valuable resource for disease modeling, pharmacological screening, and regenerative therapy. While most CVDs are linked to significant over-production of reactive oxygen species (ROS), the effects of current antioxidants targeting excessive ROS are limited. Nanotechnology is a powerful tool to develop antioxidants with improved selectivity, solubility, and bioavailability to prevent or treat various diseases related to oxidative stress. Cerium oxide nanozymes (CeONZs) can effectively scavenge excessive ROS by mimicking the activity of endogenous antioxidant enzymes. This study aimed to assess the nanotoxicity of CeONZs and their potential antioxidant benefits in stressed human embryonic stem cells (hESCs) and their derived cardiomyocytes (hESC-CMs). RESULTS: CeONZs demonstrated reliable nanosafety and biocompatibility in hESCs and hESC-CMs within a broad range of concentrations. CeONZs exhibited protective effects on the cell viability of hESCs and hESC-CMs by alleviating excessive ROS-induced oxidative stress. Moreover, CeONZs protected hESC-CMs from doxorubicin (DOX)-induced cardiotoxicity and partially ameliorated the insults from DOX in neonatal rat cardiomyocytes (NRCMs). Furthermore, during hESCs culture, CeONZs were found to reduce ROS, decrease apoptosis, and enhance cell survival without affecting their self-renewal and differentiation potential. CONCLUSIONS: CeONZs displayed good safety and biocompatibility, as well as enhanced the cell viability of hESCs and hESC-CMs by shielding them from oxidative damage. These promising results suggest that CeONZs may be crucial, as a safe nanoantioxidant, to potentially improve the therapeutic efficacy of CVDs and be incorporated into regenerative medicine.


Subject(s)
Cerium , Myocytes, Cardiac , Pluripotent Stem Cells , Humans , Rats , Animals , Reactive Oxygen Species/metabolism , Oxidative Stress , Cell Differentiation , Antioxidants/pharmacology , Doxorubicin/pharmacology
2.
Stem Cell Res Ther ; 15(1): 31, 2024 Feb 05.
Article in English | MEDLINE | ID: mdl-38317221

ABSTRACT

BACKGROUND: Transcription factors HAND1 and HAND2 (HAND1/2) play significant roles in cardiac organogenesis. Abnormal expression and deficiency of HAND1/2 result in severe cardiac defects. However, the function and mechanism of HAND1/2 in regulating human early cardiac lineage commitment and differentiation are still unclear. METHODS: With NKX2.5eGFP H9 human embryonic stem cells (hESCs), we established single and double knockout cell lines for HAND1 and HAND2, respectively, whose cardiomyocyte differentiation efficiency could be monitored by assessing NKX2.5-eGFP+ cells with flow cytometry. The expression of specific markers for heart fields and cardiomyocyte subtypes was examined by quantitative PCR, western blot and immunofluorescence staining. Microelectrode array and whole-cell patch clamp were performed to determine the electrophysiological characteristics of differentiated cardiomyocytes. The transcriptomic changes of HAND knockout cells were revealed by RNA sequencing. The HAND1/2 target genes were identified and validated experimentally by integrating with HAND1/2 chromatin immunoprecipitation sequencing data. RESULTS: Either HAND1 or HAND2 knockout did not affect the cardiomyocyte differentiation kinetics, whereas depletion of HAND1/2 resulted in delayed differentiation onset. HAND1 knockout biased cardiac mesoderm toward second heart field progenitors at the expense of first heart field progenitors, leading to increased expression of atrial and outflow tract cardiomyocyte markers, which was further confirmed by the appearance of atrial-like action potentials. By contrast, HAND2 knockout cardiomyocytes had reduced expression of atrial cardiomyocyte markers and displayed ventricular-like action potentials. HAND1/2-deficient hESCs were more inclined to second heart field lineage and its derived cardiomyocytes with atrial-like action potentials than HAND1 single knockout during differentiation. Further mechanistic investigations suggested TBX5 as one of the downstream targets of HAND1/2, whose overexpression partially restored the abnormal cardiomyocyte differentiation in HAND1/2-deficient hESCs. CONCLUSIONS: HAND1/2 have specific and redundant roles in cardiac lineage commitment and differentiation. These findings not only reveal the essential function of HAND1/2 in cardiac organogenesis, but also provide important information on the pathogenesis of HAND1/2 deficiency-related congenital heart diseases, which could potentially lead to new therapeutic strategies.


Subject(s)
Basic Helix-Loop-Helix Transcription Factors , Human Embryonic Stem Cells , Humans , Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Cell Differentiation/genetics , Myocytes, Cardiac/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism , Human Embryonic Stem Cells/metabolism
4.
Cell Res ; 32(9): 843-854, 2022 09.
Article in English | MEDLINE | ID: mdl-35840807

ABSTRACT

The sinoatrial node (SAN) is the origin of the electrical signals for rhythmic heartbeats in mammals. The spontaneous firing of SAN pacemaker cells (SANPCs) triggers cardiac contraction. 'Local Ca2+ release' (LCR), a unique cellular activity, acts as the 'engine' of the spontaneous firing of SANPCs. However, the mechanism of LCR initiation remains unclear. Here, we report that endogenous glutamate drives LCRs in SANPCs. Using a glutamate sensor, we unraveled a tight correlation between glutamate accumulation and LCR occurrence, indicating a potential relationship between glutamate and LCRs. Intracellular application of glutamate significantly enhanced the LCRs in both intact and permeabilized SANPCs. Mechanistically, we revealed that mitochondrial excitatory amino acid transporter 1 (EAAT1)-dependent mitochondrial glutamate import promoted ROS generation, which in turn led to the oxidation of Ca2+-handling proteins, ultimately resulting in enhanced LCRs. Importantly, EAAT1 depletion reduced both the spontaneous firing rates of isolated SANPCs and the heart rate in vitro and in vivo, suggesting the central role of EAAT1 as a glutamate transporter in the regulation of cardiac autonomic rhythm. In conclusion, our results indicate that glutamate serves as an LCR igniter in SANPCs, adding a potentially important element to the coupled-clock theory that explains the origin of spontaneous firing. These findings shed new light on the future prevention and treatment of cardiac pacemaker cell-related arrhythmias.


Subject(s)
Glutamic Acid , Sinoatrial Node , Animals , Calcium/metabolism , Glutamic Acid/metabolism , Mammals , Myocytes, Cardiac/metabolism , Sinoatrial Node/metabolism
5.
Cell Res ; 31(9): 951-964, 2021 09.
Article in English | MEDLINE | ID: mdl-33824424

ABSTRACT

As an excitatory transmitter system, the glutamatergic transmitter system controls excitability and conductivity of neurons. Since both cardiomyocytes and neurons are excitable cells, we hypothesized that cardiomyocytes may also be regulated by a similar system. Here, we have demonstrated that atrial cardiomyocytes have an intrinsic glutamatergic transmitter system, which regulates the generation and propagation of action potentials. First, there are abundant vesicles containing glutamate beneath the plasma membrane of rat atrial cardiomyocytes. Second, rat atrial cardiomyocytes express key elements of the glutamatergic transmitter system, such as the glutamate metabolic enzyme, ionotropic glutamate receptors (iGluRs), and glutamate transporters. Third, iGluR agonists evoke iGluR-gated currents and decrease the threshold of electrical excitability in rat atrial cardiomyocytes. Fourth, iGluR antagonists strikingly attenuate the conduction velocity of electrical impulses in rat atrial myocardium both in vitro and in vivo. Knockdown of GRIA3 or GRIN1, two highly expressed iGluR subtypes in atria, drastically decreased the excitatory firing rate and slowed down the electrical conduction velocity in cultured human induced pluripotent stem cell (iPSC)-derived atrial cardiomyocyte monolayers. Finally, iGluR antagonists effectively prevent and terminate atrial fibrillation in a rat isolated heart model. In addition, the key elements of the glutamatergic transmitter system are also present and show electrophysiological functions in human atrial cardiomyocytes. In conclusion, our data reveal an intrinsic glutamatergic transmitter system directly modulating excitability and conductivity of atrial cardiomyocytes through controlling iGluR-gated currents. Manipulation of this system may open potential new avenues for therapeutic intervention of cardiac arrhythmias.


Subject(s)
Atrial Fibrillation , Induced Pluripotent Stem Cells , Action Potentials , Animals , Heart Atria , Humans , Myocytes, Cardiac , Rats
6.
Protein Cell ; 12(7): 545-556, 2021 07.
Article in English | MEDLINE | ID: mdl-33548033

ABSTRACT

Activation of the heart normally begins in the sinoatrial node (SAN). Electrical impulses spontaneously released by SAN pacemaker cells (SANPCs) trigger the contraction of the heart. However, the cellular nature of SANPCs remains controversial. Here, we report that SANPCs exhibit glutamatergic neuron-like properties. By comparing the single-cell transcriptome of SANPCs with that of cells from primary visual cortex in mouse, we found that SANPCs co-clustered with cortical neurons. Tissue and cellular imaging confirmed that SANPCs contained key elements of glutamatergic neurotransmitter system, expressing genes encoding glutamate synthesis pathway (Gls), ionotropic and metabotropic glutamate receptors (Grina, Gria3, Grm1 and Grm5), and glutamate transporters (Slc17a7). SANPCs highly expressed cell markers of glutamatergic neurons (Snap25 and Slc17a7), whereas Gad1, a marker of GABAergic neurons, was negative. Functional studies revealed that inhibition of glutamate receptors or transporters reduced spontaneous pacing frequency of isolated SAN tissues and spontaneous Ca2+ transients frequency in single SANPC. Collectively, our work suggests that SANPCs share dominant biological properties with glutamatergic neurons, and the glutamatergic neurotransmitter system may act as an intrinsic regulation module of heart rhythm, which provides a potential intervention target for pacemaker cell-associated arrhythmias.


Subject(s)
Biological Clocks/genetics , Nerve Tissue Proteins/genetics , Neurons/metabolism , Primary Visual Cortex/metabolism , Sinoatrial Node/metabolism , Transcriptome , Action Potentials/physiology , Animals , Astrocytes/cytology , Astrocytes/metabolism , Calcium/metabolism , Carrier Proteins/classification , Carrier Proteins/genetics , Carrier Proteins/metabolism , Gene Expression Profiling , Gene Expression Regulation , Glutamic Acid/metabolism , Male , Mice , Mice, Inbred C57BL , Microglia/cytology , Microglia/metabolism , Myocytes, Cardiac/cytology , Myocytes, Cardiac/metabolism , Nerve Tissue Proteins/classification , Nerve Tissue Proteins/metabolism , Neurons/cytology , Primary Visual Cortex/cytology , Receptors, Ionotropic Glutamate/classification , Receptors, Ionotropic Glutamate/genetics , Receptors, Ionotropic Glutamate/metabolism , Receptors, Metabotropic Glutamate/classification , Receptors, Metabotropic Glutamate/genetics , Receptors, Metabotropic Glutamate/metabolism , Single-Cell Analysis , Sinoatrial Node/cytology , Tissue Culture Techniques , gamma-Aminobutyric Acid/metabolism
7.
Nat Commun ; 12(1): 287, 2021 01 12.
Article in English | MEDLINE | ID: mdl-33436583

ABSTRACT

Bioelectrical impulses intrinsically generated within the sinoatrial node (SAN) trigger the contraction of the heart in mammals. Though discovered over a century ago, the molecular and cellular features of the SAN that underpin its critical function in the heart are uncharted territory. Here, we identify four distinct transcriptional clusters by single-cell RNA sequencing in the mouse SAN. Functional analysis of differentially expressed genes identifies a core cell cluster enriched in the electrogenic genes. The similar cellular features are also observed in the SAN from both rabbit and cynomolgus monkey. Notably, Vsnl1, a core cell cluster marker in mouse, is abundantly expressed in SAN, but is barely detectable in atrium or ventricle, suggesting that Vsnl1 is a potential SAN marker. Importantly, deficiency of Vsnl1 not only reduces the beating rate of human induced pluripotent stem cell - derived cardiomyocytes (hiPSC-CMs) but also the heart rate of mice. Furthermore, weighted gene co-expression network analysis (WGCNA) unveiled the core gene regulation network governing the function of the SAN in mice. Overall, these findings reveal the whole transcriptome profiling of the SAN at single-cell resolution, representing an advance toward understanding of both the biology and the pathology of SAN.


Subject(s)
Mammals/genetics , Sequence Analysis, RNA , Single-Cell Analysis , Sinoatrial Node/cytology , Animals , Biological Clocks , Cell Aggregation , Cluster Analysis , Gene Expression Regulation , Gene Regulatory Networks , Heart Rate , Induced Pluripotent Stem Cells/cytology , Macaca fascicularis , Mice , Myocytes, Cardiac/metabolism , Neurocalcin/deficiency , Neurocalcin/metabolism , Rabbits , Species Specificity , Stochastic Processes
8.
Circ Res ; 126(12): 1706-1720, 2020 06 05.
Article in English | MEDLINE | ID: mdl-32212953

ABSTRACT

RATIONALE: The stress response of heart rate, which is determined by the plasticity of the sinoatrial node (SAN), is essential for cardiac function and survival in mammals. As an RNA-binding protein, CIRP (cold-inducible RNA-binding protein) can act as a stress regulator. Previously, we have documented that CIRP regulates cardiac electrophysiology at posttranscriptional level, suggesting its role in SAN plasticity, especially upon stress conditions. OBJECTIVE: Our aim was to clarify the role of CIRP in SAN plasticity and heart rate regulation under stress conditions. METHODS AND RESULTS: Telemetric ECG monitoring demonstrated an excessive acceleration of heart rate under isoprenaline stimulation in conscious CIRP-KO (knockout) rats. Patch-clamp analysis and confocal microscopic Ca2+ imaging of isolated SAN cells demonstrated that isoprenaline stimulation induced a faster spontaneous firing rate in CIRP-KO SAN cells than that in WT (wild type) SAN cells. A higher concentration of cAMP-the key mediator of pacemaker activity-was detected in CIRP-KO SAN tissues than in WT SAN tissues. RNA sequencing and quantitative real-time polymerase chain reaction analyses of single cells revealed that the 4B and 4D subtypes of PDE (phosphodiesterase), which controls cAMP degradation, were significantly decreased in CIRP-KO SAN cells. A PDE4 inhibitor (rolipram) abolished the difference in beating rate resulting from CIRP deficiency. The mechanistic study showed that CIRP stabilized the mRNA of Pde4b and Pde4d by direct mRNA binding, thereby regulating the protein expression of PDE4B and PDE4D at posttranscriptional level. CONCLUSIONS: CIRP acts as an mRNA stabilizer of specific PDEs to control the cAMP concentration in SAN, maintaining the appropriate heart rate stress response.


Subject(s)
Cold Shock Proteins and Peptides/metabolism , Cyclic Nucleotide Phosphodiesterases, Type 4/metabolism , Heart Rate , Myocytes, Cardiac/metabolism , RNA-Binding Proteins/metabolism , Adrenergic beta-Agonists/pharmacology , Animals , Cells, Cultured , Cold Shock Proteins and Peptides/genetics , Cyclic AMP/metabolism , Cyclic Nucleotide Phosphodiesterases, Type 4/genetics , Isoproterenol/pharmacology , Male , Myocytes, Cardiac/drug effects , Myocytes, Cardiac/physiology , Phosphodiesterase Inhibitors/pharmacology , RNA Stability , RNA-Binding Proteins/genetics , Rats , Rats, Sprague-Dawley , Rolipram/pharmacology , Sinoatrial Node/cytology , Sinoatrial Node/metabolism , Sinoatrial Node/physiology , Stress, Physiological
9.
Heart Rhythm ; 17(6): 998-1008, 2020 06.
Article in English | MEDLINE | ID: mdl-31918003

ABSTRACT

BACKGROUND: Atrial fibrillation (AF), the most common sustained arrhythmia, significantly increases cardiovascular and cerebrovascular morbidity and mortality. The pathogenesis and treatment of AF remain a major challenge in the field of cardiology. We previously found that cold-inducible RNA-binding protein (CIRP) regulated ventricular repolarization by posttranscriptionally regulating Kv4.2/4.3 ion channels in rats, but the role of CIRP in AF is not clear. OBJECTIVE: The purpose of this study was to confirm that CIRP participates in atrial electrophysiological remodeling and AF occurrence by regulating atrial channels posttranscriptionally. METHODS: Programmed intra-atrial stimulation was used to induce AF in wild-type or transcription activator-like effector nucleases-based CIRP knockout (KO) rats. Atrial optical mapping, patch clamp, Western blotting, RNA immunoprecipitation, and luciferase reporter assays were performed to evaluate the underlying mechanism of atrial electrical remodeling. RESULTS: First, we observed a shortened atrial effective refractory period and increased susceptibility to AF in CIRP KO rats. Second, atria-specific CIRP delivery through an adeno-associated viral vector serotype 9 prolonged the atrial effective refractory period and attenuated AF development in CIRP KO rats. Third, we observed the shortened action potential duration and enhanced expression of Kv1.5 and Kv4.2/4.3 in KO rats. The transient outward current blocker 4-Aminopyridine and ultrarapid component of the delayed rectifier current blocker Diphenyl phosphine oxide-1 restored the shortened action potential duration in KO atria. Finally, we demonstrated that CIRP suppressed Kv1.5 and Kv4.2/4.3 expression by directly targeting their 3'-untranslated regions. CONCLUSION: CIRP plays a protective role in preventing AF onset through the posttranscriptional regulation of Kv1.5 and Kv4.2/4.3.


Subject(s)
Atrial Fibrillation/genetics , Cold Shock Proteins and Peptides/genetics , Kv1.5 Potassium Channel/metabolism , RNA-Binding Proteins/genetics , Shal Potassium Channels/metabolism , Animals , Atrial Fibrillation/metabolism , Blotting, Western , Cold Shock Proteins and Peptides/metabolism , Disease Models, Animal , Male , Patch-Clamp Techniques , RNA-Binding Proteins/metabolism , Rats , Rats, Sprague-Dawley , Transcription, Genetic
10.
Circ Arrhythm Electrophysiol ; 12(4): e007097, 2019 04.
Article in English | MEDLINE | ID: mdl-30939909

ABSTRACT

BACKGROUND: Kv1.5 (Potassium voltage-gated channel subfamily A member 5) has been regarded as a promising target of interventions for atrial fibrillation (AF). SNX17 (sorting nexin 17), a member of the SNXs (sorting nexin family), regulates the intracellular trafficking of membrane proteins through its FERM (four-point-one, ezrin, radixin, moesin) domain. However, whether SNX17 regulates the trafficking process of Kv1.5 remains unknown. METHODS: A SNX17 knockout rat line was generated to test the role of SNX17 in atrial electrophysiology. The protein expression of SNX17 and membrane ion channels was detected by Western blotting. Electrophysiology changes in the atrial tissue and myocytes were analyzed by optical mapping and patch clamp, respectively. Acetylcholine and electrical stimulation were used to induce AF, and ECG recording was adopted to assess the influence of SNX17 deficiency on AF susceptibility. The spatial relationship between Kv1.5 and SNX17 was evaluated by immunostaining and confocal scanning, and the functional region of SNX17 regulating Kv1.5 trafficking was identified using plasmids with truncated SNX17 domains. RESULTS: Embryonic death occurred in homozygous SNX17 knockout rats. SNX17 heterozygous rats survived, and the level of the SNX17 protein in the atrium was decreased by ≈50%. SNX17 deficiency increased the membrane expression of Kv1.5 and atria-specific ultrarapid delayed rectifier outward potassium current ( IKur) density, resulting in a shortened action potential duration, and eventually contributing to AF susceptibility. Mechanistically, SNX17 facilitated the endocytic sorting of Kv1.5 from the plasma membrane to early endosomes via the FERM domain. CONCLUSIONS: SNX17 mediates susceptibility to AF by regulating endocytic sorting of the Kv1.5 channel through the FERM domain. SNX17 could be a potential target for the development of new drugs for AF.


Subject(s)
Atrial Fibrillation/physiopathology , Potassium Channels, Voltage-Gated/physiology , Sorting Nexins/physiology , Animals , Blotting, Western , Electrocardiography , Electrophysiologic Techniques, Cardiac , HEK293 Cells , Humans , Microscopy, Confocal , Myocytes, Cardiac/metabolism , Patch-Clamp Techniques , Rats , Rats, Sprague-Dawley
11.
Int J Cardiol ; 275: 120-128, 2019 Jan 15.
Article in English | MEDLINE | ID: mdl-30309679

ABSTRACT

BACKGROUND: Low-density lipoprotein receptor-related protein 5 (LRP5) has been intensively studied as a co-receptor for ß-catenin-dependent Wnt signaling. Emerging evidences have demonstrated ß-catenin-independent functions of LRP5. However, the biological role of LRP5 in the mammalian heart is largely unknown. METHODS AND RESULTS: Conditional cardiac-specific Lrp5 knockout (Lrp5-CKO) mice were generated by crossing Lrp5flox/flox mice with αMHC/MerCreMer mice. Lrp5-CKO mice consistently displayed normal cardiac structure and function. Telemetric electrocardiogram recordings revealed a short QT interval in Lrp5-CKO mice, which was tightly linked to the striking abbreviation of action potential duration (APD) in ventricular myocytes. The analysis of whole-cell currents indicated that a reduction in activity and protein expression of L-type calcium channel (LTCC), rather than other ion channels, contributed to the abnormality in APD. Furthermore, we showed that Lrp5 ablation induced a significant convergence of CaV1.2α1c proteins to the endoplasmic reticulum. Consequently, increased proteasomal degradation of these proteins was observed, which was independent of the Wnt/ß-catenin signaling pathway. CONCLUSIONS: LRP5 directly modulates the degradation of LTCC to control cardiac QT interval. These findings provide compelling evidence for the potential role of LRPs in cardiac electrophysiology.


Subject(s)
Calcium Channels, L-Type/genetics , Electrocardiography , Gene Expression Regulation , Low Density Lipoprotein Receptor-Related Protein-5/metabolism , Myocytes, Cardiac/metabolism , RNA/genetics , Tachycardia, Ventricular/metabolism , Animals , Blotting, Western , Calcium Channels, L-Type/biosynthesis , Disease Models, Animal , Homeostasis , Mice, Knockout , Myocytes, Cardiac/pathology , Polymerase Chain Reaction , Tachycardia, Ventricular/pathology , Tachycardia, Ventricular/physiopathology
12.
J Am Heart Assoc ; 7(3)2018 02 03.
Article in English | MEDLINE | ID: mdl-29431104

ABSTRACT

BACKGROUND: Heart failure is a complex syndrome characterized by cardiac contractile impairment with high mortality. Defective intracellular Ca2+ homeostasis is the central cause under this scenario and tightly links to ultrastructural rearrangements of sarcolemmal transverse tubules and the sarcoplasmic reticulum (SR); however, the modulators of the SR architecture remain unknown. The SR has been thought to be a specialized endoplasmic reticulum membrane system. Receptor accessory proteins (REEPs)/DP1/Yop1p are responsible for shaping high-curvature endoplasmic reticulum tubules. This study aimed to determine the role of REEPs in SR membrane shaping and thus cardiac function. METHODS AND RESULTS: We identified REEP5 (receptor accessory protein 5) as more highly expressed than other REEP members in adult rat ventricular myocardium, and it was downregulated in the failing hearts. Targeted inactivation of REEP5 in rats specially deformed the cardiac SR membrane without affecting transverse tubules, and this was visualized by focused ion beam scanning electron microscopy-based 3-dimensional reconstruction. Accordingly, simultaneous recordings of depolarization-induced Ca2+ currents and Ca2+ transients in REEP5-null cardiomyocytes revealed normal L-type Ca2+ channel currents but a depressed SR Ca2+ release. Consequently, the excitation-contraction coupling gain of cardiomyocytes and consequent cardiac contractility were compromised. REEP5 deficiency did not alter the expression of major proteins involved in Ca2+ handling in the heart. CONCLUSIONS: REEP5 modulates cardiac function by shaping the SR. REEP5 defect deforms the SR architecture to depress cardiac contractility. REEP5-dependent SR shaping might have potential as a therapeutic target for heart failure.


Subject(s)
Calcium Signaling , Heart Failure/metabolism , Membrane Proteins/metabolism , Myocardial Contraction , Myocytes, Cardiac/metabolism , Sarcoplasmic Reticulum/metabolism , Animals , Disease Models, Animal , Excitation Contraction Coupling , Heart Failure/genetics , Heart Failure/pathology , Heart Failure/physiopathology , Imaging, Three-Dimensional , Membrane Potentials , Membrane Proteins/genetics , Microscopy, Electron, Scanning/methods , Microscopy, Electron, Transmission , Myocytes, Cardiac/ultrastructure , Rats, Transgenic , Sarcoplasmic Reticulum/ultrastructure , Time Factors
13.
Nat Commun ; 7: 11775, 2016 06 02.
Article in English | MEDLINE | ID: mdl-27250245

ABSTRACT

Low-density lipoprotein receptor-related protein 6 (LRP6) is a Wnt co-receptor in the canonical Wnt/ß-catenin signalling. Here, we report the scaffold function of LRP6 in gap junction formation of cardiomyocytes. Cardiac LRP6 is spatially restricted to intercalated discs and binds to gap junction protein connexin 43 (Cx43). A deficiency in LRP6 disrupts Cx43 gap junction formation and thereby impairs the cell-to-cell coupling, which is independent of Wnt/ß-catenin signalling. The defect in Cx43 gap junction resulting from LRP6 reduction is attributable to the defective traffic of de novo Cx43 proteins from the endoplasmic reticulum to the Golgi apparatus, leading to the lysosomal degradation of Cx43 proteins. Accordingly, the hearts of conditional cardiac-specific Lrp6-knockout mice consistently exhibit overt reduction of Cx43 gap junction plaques without any abnormality in Wnt signalling and are predisposed to lethal arrhythmias. These findings uncover a distinct role of LRP6 as a platform for intracellular protein trafficking.


Subject(s)
Arrhythmias, Cardiac/genetics , Gap Junctions/metabolism , Heart Ventricles/metabolism , Low Density Lipoprotein Receptor-Related Protein-6/genetics , Myocardium/metabolism , Myocytes, Cardiac/metabolism , Animals , Arrhythmias, Cardiac/metabolism , Arrhythmias, Cardiac/physiopathology , Connexin 43/genetics , Connexin 43/metabolism , Echocardiography , Endoplasmic Reticulum/metabolism , Endoplasmic Reticulum/ultrastructure , Gap Junctions/ultrastructure , Gene Expression Regulation , Golgi Apparatus/metabolism , Golgi Apparatus/ultrastructure , Heart Ventricles/pathology , Low Density Lipoprotein Receptor-Related Protein-6/deficiency , Mice , Mice, Knockout , Myocardium/pathology , Myocytes, Cardiac/pathology , Organ Culture Techniques , Primary Cell Culture , Protein Transport , Rats , Rats, Sprague-Dawley , Signal Transduction , Wnt Proteins/genetics , Wnt Proteins/metabolism , beta Catenin/genetics , beta Catenin/metabolism
14.
Circ Res ; 116(10): 1655-9, 2015 May 08.
Article in English | MEDLINE | ID: mdl-25953924

ABSTRACT

RATIONALE: Cold-inducible RNA-binding protein (CIRP) is constitutively expressed at low levels across various tissues. It is rapidly upregulated by multiple stresses, underlying a general role for CIRP in organic adaptations to pathophysiological conditions. However, the role of CIRP in the heart remains unclear. OBJECTIVE: To examine the biofunctions of CIRP in the mammalian heart. METHODS AND RESULTS: Rats with targeted disruption of Cirp were generated using the TALEN (transcription activator-like effector nucleases)-based genome editing technique. The Cirp-knockout rats had structurally and functionally normal hearts. Resting ECG recordings revealed a short rate-corrected QT (QTc) interval in Cirp-null rats without any abnormalities in PR interval, RR interval or QRS waves as compared to wild-type animals. The shortened QTc interval from Cirp ablation was tightly linked to an abbreviated action potential duration in cardiac myocytes, which was attributable to increased transient outward potassium current (Ito). Furthermore, our findings uncovered that CIRP protein selectively bonded to KCND2 and KCND3 mRNAs encoding the functional α-subunits of Ito channel proteins. CIRP deficiency did not change the transcriptional activity of KCND2 or KCND3, but it facilitated their translation. Cirp knockout had no effect on the functional expression of ion channels other than Ito channels. CONCLUSIONS: CIRP modulates cardiac repolarization by negatively adjusting the expression and function of Ito channels. Our study may open a window to decipher the potential function of RNA-binding proteins in bioelectric activity.


Subject(s)
Cold Shock Proteins and Peptides/metabolism , Myocytes, Cardiac/metabolism , RNA-Binding Proteins/metabolism , Shal Potassium Channels/metabolism , Action Potentials , Animals , Binding Sites , Cells, Cultured , Cold Shock Proteins and Peptides/deficiency , Cold Shock Proteins and Peptides/genetics , Genotype , Heart Rate , Ion Channel Gating , Kv Channel-Interacting Proteins/genetics , Kv Channel-Interacting Proteins/metabolism , Phenotype , Protein Binding , RNA, Messenger/metabolism , RNA-Binding Proteins/genetics , Rats, Transgenic , Shal Potassium Channels/genetics , Time Factors , Transcription, Genetic , Transfection
15.
J Cell Mol Med ; 18(10): 1992-9, 2014 Oct.
Article in English | MEDLINE | ID: mdl-25092467

ABSTRACT

Ischaemic cardiac arrhythmias cause a large proportion of sudden cardiac deaths worldwide. The ischaemic arrhythmogenesis is primarily because of the dysfunction and adverse remodelling of sarcolemma ion channels. However, the potential regulators of sarcolemma ion channel turnover and function in ischaemic cardiac arrhythmias remains unknown. Our previous studies indicate that dynamin-2 (DNM2), a cardiac membrane-remodelling GTPase, modulates ion channels membrane trafficking in the cardiomyocytes. Here, we have found that DNM2 plays an important role in acute ischaemic arrhythmias. In rat ventricular tissues and primary cardiomyocytes subjected to acute ischaemic stress, the DNM2 protein and transcription levels were markedly down-regulated. This DNM2 reduction was coupled with severe ventricular arrhythmias. Moreover, we identified that the down-regulation of DNM2 within cardiomyocytes increases the action potential amplitude and prolongs the re-polarization duration by depressing the retrograde trafficking of Nav1.5 and Kir2.1 channels. These effects are likely to account for the DNM2 defect-induced arrhythmogenic potentials. These results suggest that DNM2, with its multi-ion channel targeting properties, could be a promising target for novel antiarrhythmic therapies.


Subject(s)
Arrhythmias, Cardiac/metabolism , Dynamin II/metabolism , Ischemia/metabolism , Myocytes, Cardiac/metabolism , NAV1.5 Voltage-Gated Sodium Channel/metabolism , Potassium Channels, Inwardly Rectifying/metabolism , Animals , Arrhythmias, Cardiac/genetics , Arrhythmias, Cardiac/pathology , Biotinylation , Blotting, Western , Cells, Cultured , Dynamin II/genetics , Electrocardiography , Electrophysiology , Immunoenzyme Techniques , Ischemia/genetics , Ischemia/pathology , Male , Myocytes, Cardiac/pathology , NAV1.5 Voltage-Gated Sodium Channel/genetics , Potassium Channels, Inwardly Rectifying/genetics , RNA, Messenger/genetics , Rats , Rats, Sprague-Dawley , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction
16.
Cell Res ; 24(8): 977-93, 2014 Aug.
Article in English | MEDLINE | ID: mdl-25022898

ABSTRACT

Pathological cardiac hypertrophy is an inevitable forerunner of heart failure. Regardless of the etiology of cardiac hypertrophy, cardiomyocyte mitochondrial alterations are always observed in this context. The translocases of mitochondrial outer membrane (Tom) complex governs the import of mitochondrial precursor proteins to maintain mitochondrial function under pathophysiological conditions; however, its role in the development of pathological cardiac hypertrophy remains unclear. Here, we showed that Tom70 was downregulated in pathological hypertrophic hearts from humans and experimental animals. The reduction in Tom70 expression produced distinct pathological cardiomyocyte hypertrophy both in vivo and in vitro. The defective mitochondrial import of Tom70-targeted optic atrophy-1 triggered intracellular oxidative stress, which led to a pathological cellular response. Importantly, increased Tom70 levels provided cardiomyocytes with full resistance to diverse pro-hypertrophic insults. Together, these results reveal that Tom70 acts as a molecular switch that orchestrates hypertrophic stresses and mitochondrial responses to determine pathological cardiac hypertrophy.


Subject(s)
Cardiomegaly/pathology , Mitochondrial Membrane Transport Proteins/metabolism , Animals , Cardiomegaly/metabolism , Disease Models, Animal , Down-Regulation , Heart Failure/metabolism , Heart Failure/pathology , Humans , Male , Mice , Mice, Inbred C57BL , Mitochondrial Membrane Transport Proteins/antagonists & inhibitors , Mitochondrial Membrane Transport Proteins/genetics , Mitochondrial Precursor Protein Import Complex Proteins , Myocytes, Cardiac/cytology , Myocytes, Cardiac/metabolism , Oxidative Stress , RNA Interference , RNA, Small Interfering/metabolism , Rats , Rats, Sprague-Dawley , Zebrafish/metabolism
17.
PLoS One ; 9(1): e86156, 2014.
Article in English | MEDLINE | ID: mdl-24497937

ABSTRACT

Long non-coding RNAs (lncRNAs) are key regulatory molecules involved in a variety of biological processes and human diseases. However, the pathological effects of lncRNAs on primary varicose great saphenous veins (GSVs) remain unclear. The purpose of the present study was to identify aberrantly expressed lncRNAs involved in the prevalence of GSV varicosities and predict their potential functions. Using microarray with 33,045 lncRNA and 30,215 mRNA probes, 557 lncRNAs and 980 mRNAs that differed significantly in expression between the varicose great saphenous veins and control veins were identified in six pairs of samples. These lncRNAs were sub-grouped and mRNAs expressed at different levels were clustered into several pathways with six focused on metabolic pathways. Quantitative real-time PCR replication of nine lncRNAs was performed in 32 subjects, validating six lncRNAs (AF119885, AK021444, NR_027830, G36810, NR_027927, uc.345-). A coding-non-coding gene co-expression network revealed that four of these six lncRNAs may be correlated with 11 mRNAs and pathway analysis revealed that they may be correlated with another 8 mRNAs associated with metabolic pathways. In conclusion, aberrantly expressed lncRNAs for GSV varicosities were here systematically screened and validated and their functions were predicted. These findings provide novel insight into the physiology of lncRNAs and the pathogenesis of varicose veins for further investigation. These aberrantly expressed lncRNAs may serve as new therapeutic targets for varicose veins. The Human Ethnics Committee of Shanghai East Hospital, Tongji University School of Medicine approved the study (NO.: 2011-DF-53).


Subject(s)
Gene Expression Profiling , RNA, Long Noncoding/genetics , Saphenous Vein/metabolism , Varicose Veins/genetics , Adult , Aged , Female , Gene Ontology , Gene Regulatory Networks , Humans , Male , Middle Aged , Oligonucleotide Array Sequence Analysis , RNA, Messenger/genetics , Reverse Transcriptase Polymerase Chain Reaction , Saphenous Vein/pathology
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