Resting mitochondrial matrix Ca2+ is maintained through a mitochondrial calcium uptake 1 (MICU1)-established threshold inhibition of mitochondrial calcium uniporter (MCU) activity. It is not known ...how MICU1 interacts with MCU to establish this Ca2+ threshold for mitochondrial Ca2+ uptake and MCU activity. Here, we show that MICU1 localizes to the mitochondrial matrix side of the inner mitochondrial membrane and MICU1/MCU binding is determined by a MICU1 N-terminal polybasic domain and two interacting coiled-coil domains of MCU. Further investigation reveals that MICU1 forms homo-oligomers, and this oligomerization is independent of the polybasic region. However, the polybasic region confers MICU1 oligomeric binding to MCU and controls mitochondrial Ca2+ current (IMCU). Moreover, MICU1 EF hands regulate MCU channel activity, but do not determine MCU binding. Loss of MICU1 promotes MCU activation leading to oxidative burden and a halt to cell migration. These studies establish a molecular mechanism for MICU1 control of MCU-mediated mitochondrial Ca2+ accumulation, and dysregulation of this mechanism probably enhances vascular dysfunction.
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•Mitochondrial Ca2+ is maintained by MICU1 inhibition of mitochondrial uniporter•MICU1 localizes to the mitochondrial matrix and forms homo-oligomers•MICU1/MCU binding is determined by a MICU1 N-terminal polybasic domain•MICU1 EF hands determine MCU activity, but not binding
Resting mitochondrial matrix Ca2+ is maintained through a MICU1-established threshold inhibition of mitochondrial calcium uniporter (MCU) activity. Madesh and colleagues show that MICU1 localizes to the mitochondrial matrix and that MICU1/MCU interaction is determined by a MICU1 N-terminal polybasic domain and two interacting coiled-coil domains of MCU. MICU1 forms homo-oligomers, and this oligomerization is independent of the polybasic region. Loss of MICU1 promotes MCU activation leading to oxidative burden and a halt to endothelial cell migration. MICU1 dysregulation may thus enhance vascular dysfunction.
Current Landscape of Heart Failure Gene Therapy Kieserman, Jake M; Myers, Valerie D; Dubey, Praveen ...
Journal of the American Heart Association,
05/2019, Letnik:
8, Številka:
10
Journal Article
Thyroid disorders and sleep disorders are common problems in the general population that can affect people of all ages, backgrounds, and sexes, but little is known about their clinical associations. ...We reviewed the literature assessing the associations between thyroid disease and sleep disorders and noted that hyperthyroidism and hypothyroidism have clinical overlap with sleep conditions such as insomnia, restless legs syndrome, and obstructive sleep apnea. These findings highlight the importance of identifying and managing thyroid dysfunction for patients with these common sleep disorders. Additional research is needed to further understand how thyroid dysfunction affects sleep physiology.
β-adrenergic receptors (βARs) are critical regulators of acute cardiovascular physiology. In response to elevated catecholamine stimulation during development of congestive heart failure (CHF), ...chronic activation of Gs-dependent β₁AR and Gi-dependent β₂AR pathways leads to enhanced cardiomyocyte death, reduced β₁AR expression, and decreased inotropic reserve. β-blockers act to block excessive catecholamine stimulation of βARs to decrease cellular apoptotic signaling and normalize β₁AR expression and inotropy. Whereas these actions reduce cardiac remodeling andmortality outcomes, the effects are not sustained. Converse to G-protein–dependent signaling, β-arrestin–dependent signaling promotes cardiomyocyte survival. Given that β₂AR expression is unaltered in CHF, a β-arrestin–biased agonist that operates through the β₂AR represents a potentially useful therapeutic approach. Carvedilol, a currently prescribed nonselective β-blocker, has been classified as a β-arrestin–biased agonist that can inhibit basal signaling from βARs and also stimulate cell survival signaling pathways. To understand the relative contribution of β-arrestin bias to the efficacy of select β-blockers, a specific β-arrestin–biased pepducin for the β₂AR, intracellular loop (ICL)1–9, was used to decouple β-arrestin–biased signaling from occupation of the orthosteric ligand-binding pocket. With similar efficacy to carvedilol, ICL1–9 was able to promote β₂AR phosphorylation, β-arrestin recruitment, β₂AR internalization, and β-arrestin–biased signaling. Interestingly, ICL1–9 was also able to induce β₂AR- and β-arrestin–dependent and Ca2+-independent contractility in primary adult murine cardiomyocytes, whereas carvedilol had no efficacy. Thus, ICL1–9 is an effective tool to access a pharmacological profile stimulating cardioprotective signaling and inotropic effects through the β₂AR and serves as a model for the next generation of cardiovascular drug development.
G protein-coupled receptor kinase 2 (GRK2) is a well-established therapeutic target for the treatment of heart failure. Herein we identify the selective serotonin reuptake inhibitor (SSRI) paroxetine ...as a selective inhibitor of GRK2 activity both in vitro and in living cells. In the crystal structure of the GRK2·paroxetine–Gβγ complex, paroxetine binds in the active site of GRK2 and stabilizes the kinase domain in a novel conformation in which a unique regulatory loop forms part of the ligand binding site. Isolated cardiomyocytes show increased isoproterenol-induced shortening and contraction amplitude in the presence of paroxetine, and pretreatment of mice with paroxetine before isoproterenol significantly increases left ventricular inotropic reserve in vivo with no significant effect on heart rate. Neither is observed in the presence of the SSRI fluoxetine. Our structural and functional results validate a widely available drug as a selective chemical probe for GRK2 and represent a starting point for the rational design of more potent and specific GRK2 inhibitors.
Actigraphs are wrist-worn devices that record tri-axial accelerometry data used clinically and in research studies. The expense of research-grade actigraphs, however, limit their widespread adoption, ...especially in clinical settings. Tri-axial accelerometer-based consumer wearable devices have gained worldwide popularity and hold potential for a cost-effective alternative. The lack of independent validation of minute-to-minute accelerometer data with polysomnographic data or even research-grade actigraphs, as well as access to raw data has hindered the utility and acceptance of consumer-grade actigraphs.
Sleep clinic patients wore a consumer-grade wearable (Huami Arc) on their non-dominant wrist while undergoing an overnight polysomnography (PSG) study. The sample was split into two, 20 in a training group and 21 in a testing group. In addition to the Arc, the testing group also wore a research-grade actigraph (Philips Actiwatch Spectrum). Sleep was scored for each 60-s epoch on both devices using the Cole-Kripke algorithm.
Based on analysis of our training group, Arc and PSG data were aligned best when a threshold of 10 units was used to examine the Arc data. Using this threshold value in our testing group, the Arc has an accuracy of 90.3%±4.3%, sleep sensitivity (or wake specificity) of 95.5%±3.5%, and sleep specificity (wake sensitivity) of 55.6%±22.7%. Compared to PSG, Actiwatch has an accuracy of 88.7%±4.5%, sleep sensitivity of 92.6%±5.2%, and sleep specificity of 60.5%±20.2%, comparable to that observed in the Arc.
An optimized sleep/wake threshold value was identified for a consumer-grade wearable Arc trained by PSG data. By applying this sleep/wake threshold value for Arc generated accelerometer data, when compared to PSG, sleep and wake estimates were adequate and comparable to those generated by a clinical-grade actigraph. As with other actigraphs, sleep specificity plateaus due to limitations in distinguishing wake without movement from sleep. Further studies are needed to evaluate the Arc's ability to differentiate between sleep and wake using other sources of data available from the Arc, such as high resolution accelerometry and photoplethysmography.
Cardiovascular disease is a leading cause of co-morbidity in HIV-1 positive patients, even those in whom plasma virus levels are well-controlled. The pathogenic mechanism of HIV-1-associated ...cardiomyopathy is unknown, but has been presumed to be mediated indirectly, owing to the absence of productive HIV-1 replication in cardiomyocytes. We sought to investigate the effect of the HIV-1 auxiliary protein, Nef, which is suspected of extracellular release by infected CD4+ T cells on protein quality control and autophagy in cardiomyocytes. After detection of Nef in the serum of HIV-1 positive patients and the accumulation of this protein in human and primate heart tissue from HIV-1/SIV-infected cells we employed cell and molecular biology approaches to investigate the effect of Nef on cardiomyocyte-homeostasis by concentrating on protein quality control (PQC) pathway and autophagy. We found that HIV-1 Nef-mediated inhibition of autophagy flux leads to cytotoxicity and death of cardiomyocytes. Nef compromises autophagy at the maturation stage of autophagosomes by interacting with Beclin 1/Rab7 and dysregulating TFEB localization and cellular lysosome content. These effects were reversed by rapamycin treatment. Our results indicate that HIV-1 Nef-mediated inhibition of cellular PQC is one possible mechanism involved in the development of HIV-associated cardiomyopathy.
Emerging findings suggest that two lineages of mitochondrial Ca(2+) uptake participate during active and resting states: 1) the major eukaryotic membrane potential-dependent mitochondrial Ca(2+) ...uniporter and 2) the evolutionarily conserved exchangers and solute carriers, which are also involved in ion transport. Although the influx of Ca(2+) across the inner mitochondrial membrane maintains metabolic functions and cell death signal transduction, the mechanisms that regulate mitochondrial Ca(2+) accumulation are unclear. Solute carriers--solute carrier 25A23 (SLC25A23), SLC25A24, and SLC25A25--represent a family of EF-hand-containing mitochondrial proteins that transport Mg-ATP/Pi across the inner membrane. RNA interference-mediated knockdown of SLC25A23 but not SLC25A24 and SLC25A25 decreases mitochondrial Ca(2+) uptake and reduces cytosolic Ca(2+) clearance after histamine stimulation. Ectopic expression of SLC25A23 EF-hand-domain mutants exhibits a dominant-negative phenotype of reduced mitochondrial Ca(2+) uptake. In addition, SLC25A23 interacts with mitochondrial Ca(2+) uniporter (MCU; CCDC109A) and MICU1 (CBARA1) while also increasing IMCU. In addition, SLC25A23 knockdown lowers basal mROS accumulation, attenuates oxidant-induced ATP decline, and reduces cell death. Further, reconstitution with short hairpin RNA-insensitive SLC25A23 cDNA restores mitochondrial Ca(2+) uptake and superoxide production. These findings indicate that SLC25A23 plays an important role in mitochondrial matrix Ca(2+) influx.
In adult left ventricular mouse myocytes, exposure to sodium cyanide (NaCN) in the presence of glucose dose-dependently reduced contraction amplitude, with ~80% of maximal inhibitory effect attained ...at 100 µM. NaCN (100 µM) exposure for 10 min significantly decreased contraction and intracellular Ca
concentration (Ca
) transient amplitudes, systolic but not diastolic Ca
, and maximal L-type Ca
current ( I
) amplitude, indicating acute alteration of Ca
homeostasis largely accounted for the observed excitation-contraction abnormalities. In addition, NaCN depolarized resting membrane potential ( E
), reduced action potential (AP) amplitude, prolonged AP duration at 50% (APD
) and 90% repolarization (APD
), and suppressed depolarization-activated K
currents but had no effect on Na
-Ca
exchange current ( I
). NaCN did not affect cellular adenosine triphosphate levels but depolarized mitochondrial membrane potential (ΔΨ
) and increased superoxide (O
) levels. Methylene blue (MB; 20 µg/ml) added 3 min after NaCN restored contraction and Ca
transient amplitudes, systolic Ca
, E
, AP amplitude, APD
, APD
, I
, depolarization-activated K
currents, ΔΨ
, and O
levels toward normal. We conclude that MB reversed NaCN-induced cardiotoxicity by preserving intracellular Ca
homeostasis and excitation-contraction coupling ( I
), minimizing risks of arrhythmias ( E
, AP configuration, and depolarization-activated K
currents), and reducing O
levels. NEW & NOTEWORTHY Cyanide poisoning due to industrial exposure, smoke inhalation, and bioterrorism manifests as cardiogenic shock and requires rapidly effective antidote. In the early stage of cyanide exposure, adenosine triphosphate levels are normal but myocyte contractility is reduced, largely due to alterations in Ca
homeostasis because of changes in oxidation-reduction environment of ion channels. Methylene blue, a drug approved by the U.S. Food and Drug Administration, ameliorates cyanide toxicity by normalizing oxidation-reduction state and Ca
channel function.
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