Cardiac contractility is mediated by a variable flux in intracellular calcium (Ca2+), thought to be integrated into mitochondria via the mitochondrial calcium uniporter (MCU) channel to match ...energetic demand. Here, we examine a conditional, cardiomyocyte-specific, mutant mouse lacking Mcu, the pore-forming subunit of the MCU channel, in adulthood. Mcu−/− mice display no overt baseline phenotype and are protected against mCa2+ overload in an in vivo myocardial ischemia-reperfusion injury model by preventing the activation of the mitochondrial permeability transition pore, decreasing infarct size, and preserving cardiac function. In addition, we find that Mcu−/− mice lack contractile responsiveness to acute β-adrenergic receptor stimulation and in parallel are unable to activate mitochondrial dehydrogenases and display reduced bioenergetic reserve capacity. These results support the hypothesis that MCU may be dispensable for homeostatic cardiac function but required to modulate Ca2+-dependent metabolism during acute stress.
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•The MCU is dispensable for baseline homeostatic cardiac function•Deletion of Mcu protects against myocardial IR injury by reducing MPTP activation•The MCU is required to match energetics with contractile demand during stress•A slow MCU-independent uptake mechanism may maintain basal matrix mCa2+ content
Luongo et al. show, using a conditional knockout mouse model, that the mitochondrial Ca2+ uniporter (MCU), although dispensable for homeostatic function, is necessary for the cardiac “fight-or-flight” contractile response and a significant contributor to mitochondrial permeability transition during ischemia-reperfusion injury.
TRPM channels are a subgroup of the transient receptor potential (TRP) channel superfamily whose members have important roles in cell proliferation and survival. TRPM2, the second subfamily member to ...be cloned, is expressed in many tissues including brain, heart, vasculature and haematopoietic cells. TRPM2 is activated by oxidative stress and several other extracellular signals including tumour necrosis factor α (TNF‐α) and amyloid β‐peptide, which increase production of ADP‐ribose (ADPR). ADPR binds to the TRPM2 C‐terminal NUDT9‐H domain, activating the channel. Early studies support the paradigm that TRPM2 activation induces cell death by sustained Ca2+ influx or by enhancing cytokine production, aggravating inflammation and tissue injury. However, more recent data show that for a number of physiological processes, TRPM2 is protective. TRPM2 protects lungs from endotoxin‐induced injury by reducing reactive oxygen species (ROS) production by phagocytes. It protects hearts from oxidative damage after ischaemia–reperfusion or hypoxia–reoxygenation by maintaining better mitochondrial bioenergetics and by decreasing ROS. Sustained Ca2+ entry through TRPM2 is required to maintain cellular bioenergetics and protect against hypoxia–reoxygenation injury. TRPM2 also protects neuroblastoma from moderate oxidative stress by decreasing ROS through increased levels of forkhead box transcription factor 3a (FOXO3a) and a downstream effector, superoxide dismutase 2. TRPM2 is important for tumour growth and cell survival through modulation of hypoxia‐inducible transcription factor expression, mitochondrial function and mitophagy. These findings in cardiac ischaemia and in neuroblastoma suggest that TRPM2 has a basic role in sustaining mitochondrial function and in cell survival that applies to a number of physiological systems and pathophysiological processes including ischaemia–reperfusion injury.
Although activation of the ion channel TRPM2 can induce cell death in some circumstances, TRPM2 can also preserve cell viability and protect against tissue damage following oxidative stress and ischaemia–reperfusion. TRPM2 dependent Ca2+ entry can modulate HIF‐1/2α expression. One mechanism through which this may occur is through enhancement of calcineurin activity through TRPM2‐dependent Ca2+ entry, which may increase HIF‐1/2α stability. HIF‐1/2α enhances expression of a number of target genes including those involved in energy metabolism, antioxidant expression and mitophagy. Ca2+ entry through TRPM2 may also directly influence mitochondrial Ca2+ uptake. Together, the impact on mitochondrial function results in reduced ROS production and reduced cell death. In contrast, in the TRPM2 KO, Ca2+ influx is reduced after oxidative stress and HIF‐1/2α expression is decreased, as are proteins downstream of HIF‐1/2α including BNIP3, SOD1/2, and NDUFA4L2. In addition, mitochondrial Ca2+ uptake is reduced, which may contribute to dysfunctional mitochondria along with decreased NDUFA4L2, and reduced mitochondrial bioenergetics. Decreased BNIP3, which results in reduced mitophagy, contributes to an accumulation of dysfunctional mitochondria and along with decreased SOD1/2 antioxidant activity, increased ROS. The cell has reduced tolerance to a further rise in ROS, for example following ischaemia or doxorubicin, leading to reduced cell survival and increased cell death in the absence of TRPM2.
Bcl2-associated athanogene-3 (BAG3) is expressed ubiquitously in humans, but its levels are highest in the heart, the skeletal muscle, and the central nervous system; it is also elevated in many ...cancers. BAG3's diverse functions are supported by its multiple protein-protein binding domains, which couple with small and large heat shock proteins, members of the Bcl2 family, other antiapoptotic proteins, and various sarcomere proteins. In the heart, BAG3 inhibits apoptosis, promotes autophagy, couples the beta-adrenergic receptor with the L-type Ca.sup.2+ channel, and maintains the structure of the sarcomere. In cancer cells, BAG3 binds to and supports an identical array of prosurvival proteins, and it may represent a therapeutic target. However, the development of strategies to block BAG3 function in cancer cells may be challenging, as they are likely to interfere with the essential roles of BAG3 in the heart. In this Review, we present the current knowledge regarding the biology of this complex protein in the heart and in cancer and suggest several therapeutic options.
The purpose of this systematic review is to provide supporting evidence for a clinical practice guideline on the use of actigraphy.
The American Academy of Sleep Medicine commissioned a task force of ...experts in sleep medicine. A systematic review was conducted to identify studies that compared the use of actigraphy, sleep logs, and/or polysomnography. Statistical analyses were performed to determine the clinical significance of using actigraphy as an objective measure of sleep and circadian parameters. Finally, the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) process was used to assess the evidence for making recommendations.
The literature search resulted in 81 studies that met inclusion criteria; all 81 studies provided data suitable for statistical analyses. These data demonstrate that actigraphy provides consistent objective data that is often unique from patient-reported sleep logs for some sleep parameters in adult and pediatric patients with suspected or diagnosed insomnia, circadian rhythm sleep-wake disorders, sleep-disordered breathing, central disorders of hypersomnolence, and adults with insufficient sleep syndrome. These data also demonstrate that actigraphy is not a reliable measure of periodic limb movements in adult and pediatric patients. The task force provided a detailed summary of the evidence along with the quality of evidence, the balance of benefits and harms, patient values and preferences, and resource use considerations.
Transient receptor potential channel TRPM2 is highly expressed in many cancers and involved in regulation of key physiological processes including mitochondrial function, bioenergetics, and oxidative ...stress. In Stage 4 non-MYCN amplified neuroblastoma patients, high TRPM2 expression is associated with worse outcome. Here, neuroblastoma cells with high TRPM2 expression demonstrated increased migration and invasion capability. RNA sequencing, RT-qPCR, and Western blotting demonstrated that the mechanism involved significantly greater expression of integrins α1, αv, β1, and β5 in cells with high TRPM2 expression. Transcription factors HIF-1α, E2F1, and FOXM1, which bind promoter/enhancer regions of these integrins, were increased in cells with high TRPM2 expression. Subcellular fractionation confirmed high levels of α1, αv, and β1 membrane localization and co-immunoprecipitation confirmed the presence of α1β1, αvβ1, and αvβ5 complexes. Inhibitors of α1β1, αvβ1, and αvβ5 complexes significantly reduced migration and invasion in cells highly expressing TRPM2, confirming their functional role. Increased pAkt
and pERK
, which promote migration through mechanisms including integrin activation, were found in cells highly expressing TRPM2. TRPM2 promotes migration and invasion in neuroblastoma cells with high TRPM2 expression through modulation of integrins together with enhancing cell survival, negatively affecting patient outcome and providing rationale for TRPM2 inhibition in anti-neoplastic therapy.
The purpose of this guideline is to establish clinical practice recommendations for the use of actigraphy in adult and pediatric patients with suspected or diagnosed sleep disorders or circadian ...rhythm sleep-wake disorders.
The American Academy of Sleep Medicine (AASM) commissioned a task force of experts in sleep medicine to develop recommendations and assigned strengths based on a systematic review of the literature and an assessment of the evidence using the GRADE process. The task force provided a summary of the relevant literature and the quality of evidence, the balance of benefits and harms, patient values and preferences, and resource use considerations that support the recommendations. The AASM Board of Directors approved the final recommendations.
The following recommendations are intended as a guide for clinicians using actigraphy in evaluating patients with sleep disorders and circadian rhythm sleep-wake disorders, and only apply to the use of FDA-approved devices. Each recommendation statement is assigned a strength ("Strong" or "Conditional"). A "Strong" recommendation (ie, "We recommend…") is one that clinicians should follow under most circumstances. A "Conditional" recommendation (ie, "We suggest…") reflects a lower degree of certainty regarding the outcome and appropriateness of the patient-care strategy for all patients. The ultimate judgment regarding any specific care must be made by the treating clinician and the patient, taking into consideration the individual circumstances of the patient, available treatment options, and resources. We suggest that clinicians use actigraphy to estimate sleep parameters in adult patients with insomnia disorder. (Conditional). We suggest that clinicians use actigraphy in the assessment of pediatric patients with insomnia disorder. (Conditional). We suggest that clinicians use actigraphy in the assessment of adult patients with circadian rhythm sleep-wake disorder. (Conditional). We suggest that clinicians use actigraphy in the assessment of pediatric patients with circadian rhythm sleep-wake disorder. (Conditional). We suggest that clinicians use actigraphy integrated with home sleep apnea test devices to estimate total sleep time during recording (in the absence of alternative objective measurements of total sleep time) in adult patients suspected of sleep-disordered breathing. (Conditional). We suggest that clinicians use actigraphy to monitor total sleep time prior to testing with the Multiple Sleep Latency Test in adult and pediatric patients with suspected central disorders of hypersomnolence. (Conditional). We suggest that clinicians use actigraphy to estimate total sleep time in adult patients with suspected insufficient sleep syndrome. (Conditional). We recommend that clinicians
use actigraphy in place of electromyography for the diagnosis of periodic limb movement disorder in adult and pediatric patients. (Strong).
Ca2+ dynamics and oxidative signaling are fundamental mechanisms for mitochondrial bioenergetics and cell function. The MCU complex is the major pathway by which these signals are integrated ...in mitochondria. Whether and how these coactive elements interact with MCU have not been established. As an approach toward understanding the regulation of MCU channel by oxidative milieu, we adapted inflammatory and hypoxia models. We identified the conserved cysteine 97 (Cys-97) to be the only reactive thiol in human MCU that undergoes S-glutathionylation. Furthermore, biochemical, structural, and superresolution imaging analysis revealed that MCU oxidation promotes MCU higher order oligomer formation. Both oxidation and mutation of MCU Cys-97 exhibited persistent MCU channel activity with higher Ca2+m uptake rate, elevated mROS, and enhanced Ca2+m overload-induced cell death. In contrast, these effects were largely independent of MCU interaction with its regulators. These findings reveal a distinct functional role for Cys-97 in ROS sensing and regulation of MCU activity.
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•Mitochondrial Ca2+ uniporter complex core component senses mitochondrial ROS•MCU Cys-97 undergoes S-glutathionylation and exhibits as a higher-order oligomer•Interaction between MCU and its regulatory components is unaltered by MCU oxidation•Inflammatory/hypoxia signals promote MCU oxidation and sensitize cells to death
Dong et al. show that conserved MCU Cys-97 senses mitochondrial luminal ROS, and MCU oxidation promotes MCU higher-order oligomer formation and exhibits persistent activation of the MCU channel, elevated mitochondrial ROS, and enhanced Ca2+m overload-induced cell death. These findings reveal a distinct functional role for Cys-97 in mROS sensing and regulation of MCU activity.
Abstract
Study Objectives:
Chronotype, or diurnal preference, refers to behavioral manifestations of the endogenous circadian system that governs preferred timing of sleep and wake. As variations in ...circadian timing and system perturbations are linked to disease development, the fundamental biology of chronotype has received attention for its role in the regulation and dysregulation of sleep and related illnesses. Family studies indicate that chronotype is a heritable trait, thus directing attention toward its genetic basis. Although discoveries from molecular studies of candidate genes have shed light onto its genetic architecture, the contribution of genetic variation to chronotype has remained unclear with few related variants identified. In the advent of large-scale genome-wide association studies (GWAS), scientists now have the ability to discover novel common genetic variants associated with complex phenotypes. Three recent large-scale GWASs of chronotype were conducted on subjects of European ancestry from the 23andMe cohort and the UK Biobank. This review discusses the findings of these landmark GWASs in the context of prior research.
Methods:
We systematically reviewed and compared methodological and analytical approaches and results across the three GWASs of chronotype.
Results:
A good deal of consistency was observed across studies with 9 genes identified in 2 of the 3 GWASs. Several genes previously unknown to influence chronotype were identified.
Conclusions:
GWAS is an important tool in identifying common variants associated with the complex chronotype phenotype, the findings of which can supplement and guide molecular science. Future directions in model systems and discovery of rare variants are discussed.
Transient receptor potential melastatin channel subfamily member 2 (TRPM2) has an essential function in cell survival and is highly expressed in many cancers. Inhibition of TRPM2 in neuroblastoma by ...depletion with CRISPR technology or expression of dominant negative TRPM2-S has been shown to significantly reduce cell viability. Here, the role of proline-rich tyrosine kinase 2 (Pyk2) in TRPM2 modulation of neuroblastoma viability was explored. In TRPM2-depleted cells, phosphorylation and expression of Pyk2 and cAMP-responsive element-binding protein (CREB), a downstream target, were significantly reduced after application of the chemotherapeutic agent doxorubicin. Overexpression of wild-type Pyk2 rescued cell viability. Reduction of Pyk2 expression with shRNA decreased cell viability and CREB phosphorylation and expression, demonstrating Pyk2 modulates CREB activation. TRPM2 depletion impaired phosphorylation of Src, an activator of Pyk2, and this may be a mechanism to reduce Pyk2 phosphorylation. TRPM2 inhibition was previously demonstrated to decrease mitochondrial function. Here, CREB, Pyk2, and phosphorylated Src were reduced in mitochondria of TRPM2-depleted cells, consistent with their role in modulating expression and activation of mitochondrial proteins. Phosphorylated Src and phosphorylated and total CREB were reduced in TRPM2-depleted nuclei. Expression and function of mitochondrial calcium uniporter (MCU), a target of phosphorylated Pyk2 and CREB, were significantly reduced. Wild-type TRPM2 but not Ca
-impermeable mutant E960D reconstituted phosphorylation and expression of Pyk2 and CREB in TRPM2-depleted cells exposed to doxorubicin. Results demonstrate that TRPM2 expression protects the viability of neuroblastoma through Src, Pyk2, CREB, and MCU activation, which play key roles in maintaining mitochondrial function and cellular bioenergetics.
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