Expression level of cardiac ryanodine receptors dictates properties of Ca-induced Ca release.

The type 2 ryanodine receptor (RyR2) is the major Ca release channel required for Ca-induced Ca release (CICR) and cardiac excitation-contraction coupling. The cluster organization of RyR2 at the dyad is critical for efficient CICR. Despite its central role in cardiac Ca signaling, the mechanisms that control CICR are not fully understood.

Phosphorylation of phospholamban promotes SERCA2a activation by dwarf open reading frame (DWORF).

In cardiac myocytes, the type 2a sarco/endoplasmic reticulum Ca-ATPase (SERCA2a) plays a key role in intracellular Ca regulation. Due to its critical role in heart function, SERCA2a activity is tightly regulated by different mechanisms, including micropeptides. While phospholamban (PLB) is a well-known SERCA2a inhibitor, dwarf open reading frame (DWORF) is a recently identified SERCA2a activator.

Protein carbonylation causes sarcoplasmic reticulum Ca overload by increasing intracellular Na level in ventricular myocytes.

Diabetes is commonly associated with an elevated level of reactive carbonyl species due to alteration of glucose and fatty acid metabolism. These metabolic changes cause an abnormality in cardiac Ca regulation that can lead to cardiomyopathies. In this study, we explored how the reactive α-dicarbonyl methylglyoxal (MGO) affects Ca regulation in mouse ventricular myocytes.

Utilization of the genetically encoded calcium indicator Salsa6F in cardiac applications.

Calcium signaling is a critical process required for cellular mechanisms such as cardiomyocyte contraction. The inability of the cell to properly activate or regulate calcium signaling can lead to contractile dysfunction. In isolated cardiomyocytes, calcium signaling has been primarily studied using calcium fluorescent dyes, however these dyes have limited applicability to whole organs.

Protein carbonylation causes sarcoplasmic reticulum Ca2+ overload by increasing intracellular Na+ level in ventricular myocytes.

Diabetes is commonly associated with an elevated level of reactive carbonyl species due to alteration of glucose and fatty acid metabolism. These metabolic changes cause an abnormality in cardiac Ca regulation that can lead to cardiomyopathies. In this study, we explored how the reactive α-dicarbonyl methylglyoxal (MGO) affects Ca regulation in mouse ventricular myocytes.

Utilization of the genetically encoded calcium indicator Salsa6F in cardiac applications.

Calcium signaling is a critical process required for cellular mechanisms such as cardiac contractility. The inability of the cell to properly activate or regulate calcium signaling can lead to contractile dysfunction. In isolated cardiomyocytes, calcium signaling has been primarily studied using calcium fluorescent dyes, however these dyes have limited applicability to whole organs.

Regulation of cardiac calcium signaling by newly identified calcium pump modulators.

In cardiomyocytes, the sarco/endoplasmic reticulum Ca-ATPase (SERCA2a) is a central component of intracellular Ca regulation. Several heart diseases, including heart failure, are associated with reduced myocardial contraction due to SERCA2a downregulation. Therefore, the need for developing new drugs that could improve SERCA2a function is high.

RyR2 Binding of an Antiarrhythmic Cyclic Depsipeptide Mapped Using Confocal Fluorescence Lifetime Detection of FRET.

Hyperactivity of cardiac sarcoplasmic reticulum (SR) ryanodine receptor (RyR2) Ca-release channels contributes to heart failure and arrhythmias. Reducing the RyR2 activity, particularly during cardiac relaxation (diastole), is a desirable therapeutic goal. We previously reported that the unnatural enantiomer () of an insect-RyR activator, verticilide, inhibits porcine and mouse RyR2 at diastolic (nanomolar) Ca and has in vivo efficacy against atrial and ventricular arrhythmia.

Cysteines 1078 and 2991 cross-linking plays a critical role in redox regulation of cardiac ryanodine receptor (RyR).

The most common cardiac pathologies, such as myocardial infarction and heart failure, are associated with oxidative stress. Oxidation of the cardiac ryanodine receptor (RyR2) Ca channel causes spontaneous oscillations of intracellular Ca, resulting in contractile dysfunction and arrhythmias. RyR2 oxidation promotes the formation of disulfide bonds between two cysteines on neighboring RyR2 subunits, known as intersubunit cross-linking.

New N-aryl-N-alkyl-thiophene-2-carboxamide compound enhances intracellular Ca dynamics by increasing SERCA2a Ca pumping.

The type 2a sarco/endoplasmic reticulum Ca-ATPase (SERCA2a) plays a central role in the intracellular Ca homeostasis of cardiac myocytes, pumping Ca from the cytoplasm into the sarcoplasmic reticulum (SR) lumen to maintain relaxation (diastole) and prepare for contraction (systole). Diminished SERCA2a function has been reported in several pathological conditions, including heart failure. Therefore, development of new drugs that improve SERCA2a Ca transport is of great clinical significance.

Presenilin 1 is a direct regulator of the cardiac sarco/endoplasmic reticulum calcium pump.

The gamma secretase catalytic subunit presenilin 1 (PS1) is expressed in the endoplasmic reticulum (ER) of neurons, where it regulates Ca signaling. PS1 is also expressed in heart, but its role in regulation of cardiac Ca transport remains unknown. Since the type 2 sarco/endoplasmic reticulum Ca ATPase (SERCA2a) plays a central role in cardiac Ca homeostasis, we studied whether PS1 regulates the cardiac SERCA2a function.

Dwarf open reading frame (DWORF) is a direct activator of the sarcoplasmic reticulum calcium pump SERCA.

The sarco-plasmic reticulum calcium pump (SERCA) plays a critical role in the contraction-relaxation cycle of muscle. In cardiac muscle, SERCA is regulated by the inhibitor phospholamban. A new regulator, dwarf open reading frame (DWORF), has been reported to displace phospholamban from SERCA.

Fecal transplantation and butyrate improve neuropathic pain, modify immune cell profile, and gene expression in the PNS of obese mice.

Obesity affects over 2 billion people worldwide and is accompanied by peripheral neuropathy (PN) and an associated poorer quality of life. Despite high prevalence, the molecular mechanisms underlying the painful manifestations of PN are poorly understood, and therapies are restricted to use of painkillers or other drugs that do not address the underlying disease. Studies have demonstrated that the gut microbiome is linked to metabolic health and its alteration is associated with many diseases, including obesity.

The functional significance of redox-mediated intersubunit cross-linking in regulation of human type 2 ryanodine receptor.

The type 2 ryanodine receptor (RyR2) plays a key role in the cardiac intracellular calcium (Ca) regulation. We have previously shown that oxidative stress activates RyR2 in rabbit cardiomyocytes by promoting the formation of disulfide bonds between neighboring RyR2 subunits. However, the functional significance of this redox modification for human RyR2 (hRyR2) remains largely unknown.

Dimerization of SERCA2a Enhances Transport Rate and Improves Energetic Efficiency in Living Cells.

The type 2a sarco/endoplasmic reticulum (ER) Ca-ATPase (SERCA2a) plays a key role in intracellular Ca regulation in the heart. We have previously shown evidence of stable homodimers of SERCA2a in heterologous cells and cardiomyocytes. However, the functional significance of the pump dimerization remains unclear.

Deletion of cardiac polycystin 2/PC2 results in increased SR calcium release and blunted adrenergic reserve.

Transient receptor potential proteins (TRPs) act as nonselective cation channels. Of the TRP channels, PC2 (also known as polycystin 2) is localized to the sarcoplasmic reticulum (SR); however, its contribution to calcium-induced calcium release and overall cardiac function in the heart is poorly understood. The goal of this study was to characterize the effect of cardiac-specific PC2 deletion in adult cardiomyocytes and in response to chronic β-adrenergic challenge.

Novel approach for quantification of endoplasmic reticulum Ca transport.

The type 2a sarco-/endoplasmic reticulum Ca-ATPase (SERCA2a) plays a key role in Ca regulation in the heart. However, available techniques to study SERCA function are either cell destructive or lack sensitivity. The goal of this study was to develop an approach to selectively measure SERCA2a function in the cellular environment.

Redox Dependent Modifications of Ryanodine Receptor: Basic Mechanisms and Implications in Heart Diseases.

Heart contraction vitally depends on tightly controlled intracellular Ca regulation. Because contraction is mainly driven by Ca released from the sarcoplasmic reticulum (SR), this organelle plays a particularly important role in Ca regulation. The type two ryanodine receptor (RyR2) is the major SR Ca release channel in ventricular myocytes.

Oxidation of ryanodine receptor after ischemia-reperfusion increases propensity of Ca waves during β-adrenergic receptor stimulation.

β-Adrenergic receptor (β-AR) activation produces the main positive inotropic response of the heart. During ischemia-reperfusion (I/R), however, β-AR activation can trigger life-threatening arrhythmias. Because I/R is frequently associated with oxidative stress, we investigated whether ryanodine receptor (RyR) oxidation contributes to proarrythmogenic Ca waves during β-AR activation.

Redistribution of SERCA calcium pump conformers during intracellular calcium signaling.

The conformational changes of a calcium transport ATPase were investigated with molecular dynamics (MD) simulations as well as fluorescence resonance energy transfer (FRET) measurements to determine the significance of a discrete structural element for regulation of the conformational dynamics of the transport cycle. Previous MD simulations indicated that a loop in the cytosolic domain of the SERCA calcium transporter facilitates an open-to-closed structural transition. To investigate the significance of this structural element, we performed additional MD simulations and new biophysical measurements of SERCA structure and function.

The role of RyR2 oxidation in the blunted frequency-dependent facilitation of Ca transient amplitude in rabbit failing myocytes.

Defective Ca regulation plays a key role in the blunted force-frequency response in heart failure (HF). Since HF is commonly associated with oxidative stress, we studied whether oxidation of ryanodine receptor (RyR2) contributes to this defect. In control ventricular myocytes, oxidative stress induced formation of disulfide bonds between RyR2 subunits: intersubunit cross-linking (XL).

The effect of PKA-mediated phosphorylation of ryanodine receptor on SR Ca leak in ventricular myocytes.

Functional impact of cardiac ryanodine receptor (type 2 RyR or RyR2) phosphorylation by protein kinase A (PKA) remains highly controversial. In this study, we characterized a functional link between PKA-mediated RyR2 phosphorylation level and sarcoplasmic reticulum (SR) Ca release and leak in permeabilized rabbit ventricular myocytes. Changes in cytosolic [Ca] and intra-SR [Ca] were measured with Fluo-4 and Fluo-5N, respectively.

R-CEPIA1er as a new tool to directly measure sarcoplasmic reticulum [Ca] in ventricular myocytes.

In cardiomyocytes, [Ca] within the sarcoplasmic reticulum (SR; [Ca]SR) partially determines the amplitude of cytosolic Ca transient that, in turn, governs myocardial contraction. Therefore, it is critical to understand the molecular mechanisms that regulate [Ca]SR handling. Until recently, the best approach available to directly measure [Ca]SR was to use low-affinity Ca indicators (e.

Increased Energy Demand during Adrenergic Receptor Stimulation Contributes to Ca(2+) Wave Generation.

While β-adrenergic receptor (β-AR) stimulation ensures adequate cardiac output during stress, it can also trigger life-threatening cardiac arrhythmias. We have previously shown that proarrhythmic Ca(2+) waves during β-AR stimulation temporally coincide with augmentation of reactive oxygen species (ROS) production. In this study, we tested the hypothesis that increased energy demand during β-AR stimulation plays an important role in mitochondrial ROS production and Ca(2+)-wave generation in rabbit ventricular myocytes.

Cytosolic Ca²⁺ buffering determines the intra-SR Ca²⁺ concentration at which cardiac Ca²⁺ sparks terminate.

Single ryanodine receptor (RyR) Ca(2+) flux amplitude (i(Ca-RyR)) decreases as intra-sarcoplasmic reticulum (SR) Ca(2+) levels fall during a cardiac Ca(2+) spark. Since i(Ca-RyR) drives the inter-RyR Ca(2+)-induced Ca(2+) release (CICR) that underlies the spark, decreasing i(Ca-RyR) may contribute to spark termination because RyRs that spontaneously close may stay closed. To test this possibility, we simultaneously measured local cytosolic and intra-SR ([Ca(2+)]cyto and [Ca(2+)]SR) during Ca(2+) sparks in permeabilized rabbit ventricular myocytes.