The valosin-containing protein protects the heart against pathological Ca2+ overload by modulating Ca2+ uptake proteins

Valosin-containing protein: A potential therapeutic target for cardiovascular diseases

Valosin-containing protein (VCP), also known as p97, plays a crucial role in various cellular processes, including protein degradation, endoplasmic reticulum-associated degradation, and cell cycle regulation. While extensive research has been focused on VCP's involvement in protein homeostasis and its implications in neurodegenerative diseases, emerging evidence suggests a potential link between VCP and cardiovascular health. VCP is a key regulator of mitochondrial function, and its overexpression or mutations lead to pathogenic diseases and cellular stress responses. The present review explores VCP's roles in numerous cardiovascular disorders including myocardial ischemia/reperfusion injury, cardiac hypertrophy, and heart failure. The review dwells on the roles of VCP in modifying mitochondrial activity, promoting S-nitrosylation, regulating mTOR signalling and demonstrating cardioprotective effects. Further research into VCP might lead to novel interventions for cardiovascular disease, particularly those involving ischemia/reperfusion injury and hypertrophy.

A pathogenic mutation in the ALS/FTD gene VCP induces mitochondrial hypermetabolism by modulating the permeability transition pore

Valosin-containing protein (VCP) is a ubiquitously expressed type II AAA+ ATPase protein, implicated in both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). This study aimed to explore the impact of the disease-causing VCPR191Q/wt mutation on mitochondrial function using a CRISPR/Cas9-engineered neuroblastoma cell line. Mitochondria in these cells are enlarged, with a depolarized mitochondrial membrane potential associated with increased respiration and electron transport chain activity. Our results indicate that mitochondrial hypermetabolism could be caused, at least partially, by increased calcium-induced opening of the permeability transition pore (mPTP), leading to mild mitochondrial uncoupling. In conclusion, our findings reveal a central role of the ALS/FTD gene VCP in maintaining mitochondrial homeostasis and suggest a model of pathogenesis based on progressive alterations in mPTP physiology and mitochondrial energetics.

Targeting calpain-2-mediated junctophilin-2 cleavage delays heart failure progression following myocardial infarction

Coronary heart disease (CHD) is a prevalent cardiac disease that causes over 370,000 deaths annually in the USA. In CHD, occlusion of a coronary artery causes ischemia of the cardiac muscle, which results in myocardial infarction (MI). Junctophilin-2 (JPH2) is a membrane protein that ensures efficient calcium handling and proper excitation-contraction coupling. Studies have identified loss of JPH2 due to calpain-mediated proteolysis as a key pathogenic event in ischemia-induced heart failure (HF). Our findings show that calpain-2-mediated JPH2 cleavage yields increased levels of a C-terminal cleaved peptide (JPH2-CTP) in patients with ischemic cardiomyopathy and mice with experimental MI. We created a novel knock-in mouse model by removing residues 479-SPAGTPPQ-486 to prevent calpain-2-mediated cleavage at this site. Functional and molecular assessment of cardiac function post-MI in cleavage site deletion (CSD) mice showed preserved cardiac contractility and reduced dilation, reduced JPH2-CTP levels, attenuated adverse remodeling, improved T-tubular structure, and normalized SR Ca2+-handling. Adenovirus mediated calpain-2 knockdown in mice exhibited similar findings. Pulldown of CTP followed by proteomic analysis revealed valosin-containing protein (VCP) and BAG family molecular chaperone regulator 3 (BAG3) as novel binding partners of JPH2. Together, our findings suggest that blocking calpain-2-mediated JPH2 cleavage may be a promising new strategy for delaying the development of HF following MI.

Active Magnesium Boride/Alginate Hydrogels Rejuvenate Senescent Cells

The clearance of senescent cells may be detrimental to low cell density diseases, such as intervertebral disc degeneration (IVDD), and rejuvenating these cells presents a formidable obstacle. In this study, we investigate a mild-alkalization strategy employing magnesium boride-alginate (MB-ALG) hydrogels to rejuvenate senescent cells associated with age-related diseases. MB-ALG hydrogels proficiently ensnare senescent cells owing to their surface roughness. The hydrolysis of MB-ALG hydrogels liberates hydroxide ions (OH-), effecting a transition from an acidic microenvironment (pH ∼ 6.2) to a mildly alkaline state (pH ∼ 8.0), thereby fostering senescent cell proliferation via activation of the PI3K/Akt/mTOR pathway. Additionally, H2 aids in ROS clearance, which reduces cellular oxidative stress. And, Mg2+ rejuvenates senescent cells by inhibiting Ca2+ influx and fine-tuning the sirt1-p53 signaling pathways. Both in vitro and in vivo experiments conducted on rat intervertebral discs corroborate the sustained antisenescence and rejuvenation properties of MB-ALG hydrogels, with effects persisting for up to 12 weeks postoperation. These discoveries elucidate the role of mild-alkalization in dictating cellular destiny and provide key insights for addressing age-related diseases.

Cardiac-Specific Suppression of Valosin-Containing Protein Induces Progressive Heart Failure and Premature Mortality Correlating with Temporal Dysregulations in mTOR Complex 2 and Protein Phosphatase 1

Valosin-containing protein (VCP), an ATPase-associated protein, is emerging as a crucial regulator in cardiac pathologies. However, the pivotal role of VCP in the heart under physiological conditions remains undetermined. In this study, we tested a hypothesis that sufficient VCP expression is required for cardiac development and physiological cardiac function. Thus, we generated a cardiac-specific VCP knockout (KO) mouse model and assessed the consequences of VCP suppression on the heart through physiological and molecular studies at baseline. Our results reveal that homozygous KO mice are embryonically lethal, whereas heterozygous KO mice with a reduction in VCP by ~40% in the heart are viable at birth but progressively develop heart failure and succumb to mortality at the age of 10 to 12 months. The suppression of VCP induced a selective activation of the mammalian target of rapamycin complex 1 (mTORC1) but not mTORC2 at the early age of 12 weeks. The prolonged suppression of VCP increased the expression (by ~2 folds) and nuclear translocation (by >4 folds) of protein phosphatase 1 (PP1), a key mediator of protein dephosphorylation, accompanied by a remarked reduction (~80%) in AKTSer473 phosphorylation in VCP KO mouse hearts at a later age but not the early stage. These temporal molecular alterations were highly associated with the progressive decline in cardiac function. Overall, our findings shed light on the essential role of VCP in the heart under physiological conditions, providing new insights into molecular mechanisms in the development of heart failure.

Valosin-containing protein acts as a target and mediator of S-nitrosylation in the heart through distinct mechanisms

S-nitrosylation (SNO) is an emerging paradigm of redox signaling protecting cells against oxidative stress in the heart. Our previous studies demonstrated that valosin-containing protein (VCP), an ATPase-associated protein, is a vital mediator protecting the heart against cardiac stress and ischemic injury. However, the molecular regulations conferred by VCP in the heart are not fully understood. In this study, we explored the potential role of VCP in cardiac protein SNO using multiple cardiac-specific genetically modified mouse models and various analytical techniques including biotin switch assay, liquid chromatography, mass spectrometry, and western blotting. Our results showed that cardiac-specific overexpression of VCP led to an overall increase in the levels of SNO-modified cardiac proteins in the transgenic (TG) vs. wild-type (WT) mice. Mass spectrometry analysis identified mitochondrial proteins involved in respiration, metabolism, and detoxification as primary targets of SNO modification in VCP-overexpressing mouse hearts. Particularly, we found that VCP itself underwent SNO modification at a specific cysteine residue in its N-domain. Additionally, our study demonstrated that glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a key enzyme in glycolysis, also experienced increased SNO in response to VCP overexpression. While deletion of inducible nitric oxide synthase (iNOS) in VCP TG mice did not affect VCP SNO, it did abolish SNO modification in mitochondrial complex proteins, suggesting a dual mechanism of regulation involving both iNOS-dependent and independent pathways. Overall, our findings shed light on post-translational modification of VCP in the heart, unveiling a previously unrecognized role for VCP in regulating cardiac protein SNO and offering new insights into its function in cardiac protection.

Mitochondrial calcium uniporter channel gatekeeping in cardiovascular disease

The mitochondrial calcium (mCa2+) uniporter channel (mtCU) resides at the inner mitochondrial membrane and is required for Ca2+ to enter the mitochondrial matrix. The mtCU is essential for cellular function, as mCa2+ regulates metabolism, bioenergetics, signaling pathways and cell death. mCa2+ uptake is primarily regulated by the MICU family (MICU1, MICU2, MICU3), EF-hand-containing Ca2+-sensing proteins, which respond to cytosolic Ca2+ concentrations to modulate mtCU activity. Considering that mitochondrial function and Ca2+ signaling are ubiquitously disrupted in cardiovascular disease, mtCU function has been a hot area of investigation for the last decade. Here we provide an in-depth review of MICU-mediated regulation of mtCU structure and function, as well as potential mtCU-independent functions of these proteins. We detail their role in cardiac physiology and cardiovascular disease by highlighting the phenotypes of different mutant animal models, with an emphasis on therapeutic potential and targets of interest in this pathway.

SEPSIS LEADS TO IMPAIRED MITOCHONDRIAL CALCIUM UPTAKE AND SKELETAL MUSCLE WEAKNESS BY REDUCING THE MICU1:MCU PROTEIN RATIO

ABSTRACT

Purpose: Intensive care unit-acquired weakness (ICUAW) is a severe neuromuscular complication that frequently occurs in patients with sepsis. The precise molecular pathophysiology of mitochondrial calcium uptake 1 (MICU1) and mitochondrial calcium uniporter (MCU) in ICUAW has not been fully elucidated. Here, we speculate that ICUAW is associated with MICU1:MCU protein ratio-mediated mitochondrial calcium ([Ca 2+ ] m ) uptake dysfunction. Methods: Cecal ligation and perforation (CLP) was performed on C57BL/6J mice to induce sepsis. Sham-operated animals were used as controls. Lipopolysaccharide (LPS) (5 μg/mL) was used to induce inflammation in differentiated C2C12 myoblasts. Compound muscle action potential (CMAP) was detected using a biological signal acquisition system. Grip strength was measured using a grip-strength meter. Skeletal muscle inflammatory factors were detected using ELISA kits. The cross-sectional area (CSA) of the tibialis anterior (TA) muscle was detected by hematoxylin and eosin staining. Cytosolic calcium ([Ca 2+ ] c ) levels were measured using Fluo-4 AM. Adeno-associated virus (AAV) was injected into TA muscles for 4 weeks to overexpress MICU1 prophylactically. A lentivirus was used to infect C2C12 cells to increase MICU1 expression prophylactically. Findings: The results suggest that sepsis induces [Ca 2+ ] m uptake disorder by reducing the MICU1:MCU protein ratio, resulting in skeletal muscle weakness and muscle fiber atrophy. However, MICU1 prophylactic overexpression reversed these effects by increasing the MICU1:MCU protein ratio. Conclusions: ICUAW is associated with impaired [Ca 2+ ] m uptake caused by a decreased MICU1:MCU protein ratio. MICU1 overexpression improves sepsis-induced skeletal muscle weakness and atrophy by ameliorating the [Ca 2+ ] m uptake disorder.

MnS Nanocapsule Mediates Mitochondrial Membrane Permeability Transition for Tumor Ion-Interference Therapy

"Structure subserves function" is one fundamental biological maxim, and so the biological membrane that delimits the regions primarily serves as the margin between life and death for individual cells. Here, an Oswald ripening mechanism-guided solvothermal method was proposed for the synthesis of uniform MnS nanocapsules assembled with metastable γ-MnS nanocrystals. Through designing the physicochemical properties, MnS nanocapsules would disaggregate into small γ-MnS nanocrystals in a tumor acidic environment, with the surface potential switched from negative to positive, thus showing conspicuous delivery performance. More significantly, the specific accumulation of Mn2+ in mitochondria was promoted due to the downregulation of mitochondrial calcium uptake 1 (MICU1) by the formed H2S, thus leading to serious mitochondrial Mn-poisoning for membrane permeability increase and then tumor apoptosis. This study provides a synthesis strategy of metal sulfide nanocapsules and encourages multidisciplinary researchers to focus on ion-cancer crosstalk for the development of an antitumor strategy.

Effect of cardioplegic arrest and reperfusion on left and right ventricular proteome/phosphoproteome in patients undergoing surgery for coronary or aortic valve disease

Our earlier work has shown inter‑disease and intra‑disease differences in the cardiac proteome between right (RV) and left (LV) ventricles of patients with aortic valve stenosis (AVS) or coronary artery disease (CAD). Whether disease remodeling also affects acute changes occuring in the proteome during surgical intervention is unknown. This study investigated the effects of cardioplegic arrest on cardiac proteins/phosphoproteins in LV and RV of CAD (n=6) and AVS (n=6) patients undergoing cardiac surgery. LV and RV biopsies were collected during surgery before ischemic cold blood cardioplegic arrest (pre) and 20 min after reperfusion (post). Tissues were snap frozen, proteins extracted, and the extracts were used for proteomic and phosphoproteomic analysis using Tandem Mass Tag (TMT) analysis. The results were analysed using QuickGO and Ingenuity Pathway Analysis softwares. For each comparision, our proteomic analysis identified more than 3,000 proteins which could be detected in both the pre and Post samples. Cardioplegic arrest and reperfusion were associated with significant differential expression of 24 (LV) and 120 (RV) proteins in the CAD patients, which were linked to mitochondrial function, inflammation and cardiac contraction. By contrast, AVS patients showed differential expression of only 3 LV proteins and 2 RV proteins, despite a significantly longer duration of ischaemic cardioplegic arrest. The relative expression of 41 phosphoproteins was significantly altered in CAD patients, with 18 phosphoproteins showing altered expression in AVS patients. Inflammatory pathways were implicated in the changes in phosphoprotein expression in both groups. Inter‑disease comparison for the same ventricular chamber at both timepoints revealed differences relating to inflammation and adrenergic and calcium signalling. In conclusion, the present study found that ischemic arrest and reperfusion trigger different changes in the proteomes and phosphoproteomes of LV and RV of CAD and AVS patients undergoing surgery, with markedly more changes in CAD patients despite a significantly shorter ischaemic period.

Mitochondrial calcium exchange in physiology and disease

The uptake of calcium into and extrusion of calcium from the mitochondrial matrix is a fundamental biological process that has critical effects on cellular metabolism, signaling, and survival. Disruption of mitochondrial calcium (mCa2+) cycling is implicated in numerous acquired diseases such as heart failure, stroke, neurodegeneration, diabetes, and cancer and is genetically linked to several inherited neuromuscular disorders. Understanding the mechanisms responsible for mCa2+ exchange therefore holds great promise for the treatment of these diseases. The past decade has seen the genetic identification of many of the key proteins that mediate mitochondrial calcium uptake and efflux. Here, we present an overview of the phenomenon of mCa2+ transport and a comprehensive examination of the molecular machinery that mediates calcium flux across the inner mitochondrial membrane: the mitochondrial uniporter complex (consisting of MCU, EMRE, MICU1, MICU2, MICU3, MCUB, and MCUR1), NCLX, LETM1, the mitochondrial ryanodine receptor, and the mitochondrial permeability transition pore. We then consider the physiological implications of mCa2+ flux and evaluate how alterations in mCa2+ homeostasis contribute to human disease. This review concludes by highlighting opportunities and challenges for therapeutic intervention in pathologies characterized by aberrant mCa2+ handling and by summarizing critical unanswered questions regarding the biology of mCa2+ flux.

Valosin Containing Protein as a Specific Biomarker for Predicting the Development of Acute Coronary Syndrome and Its Complication

Background

Acute coronary syndrome (ACS) consists of a range of acute myocardial ischemia-related manifestations. The adverse events of ACS are usually associated with ventricular dysfunction (VD), which could finally develop to heart failure. Currently, there is no satisfactory indicator that could specifically predict the development of ACS and its prognosis. Valosin-containing protein (VCP) has recently been proposed to protect against cardiac diseases. Hence, we aimed to assess whether VCP in serum can serve as a valuable biomarker for predicting ACS and its complication.

Methods

Human serum samples from 291 participants were collected and classified into four groups based on their clinical diagnosis, namely healthy control (n = 64), ACS (n = 40), chronic coronary syndrome (CCS, n = 99), and nonischemic heart disease (non-IHD, n = 88). Clinical characteristics of these participants were recorded and their serum VCP levels were detected by enzyme-linked immunosorbent assay (ELISA). Association of serum VCP with the development of ACS and its complication VD was statistically studied. Subsequently, GWAS and eQTL analyses were performed to explore the association between VCP polymorphism and monocyte count. A stability test was also performed to investigate whether VCP is a stable biomarker.

Results

Serum VCP levels were significantly higher in the ACS group compared with the rest groups. Besides, the VCP levels of patients with ACS with VD were significantly lower compared to those without VD. Multivariate logistic regression analysis revealed that VCP was associated with both the risk of ACS (P = 0.042, OR = 1.222) and the risk of developing VD in patients with ACS (P = 0.035, OR = 0.513) independently. The GWAS analysis also identified an association between VCP polymorphism (rs684562) and monocyte count, whereas the influence of rs684562 on VCP mRNA expression level was further verified by eQTL analysis. Moreover, a high stability of serum VCP content was observed under different preservation circumstances.

Conclusion

Valosin-containing protein could act as a stable biomarker in predicting the development of ACS and its complication VD.

MiRNA-339-5p promotes isoproterenol-induced cardiomyocyte hypertrophy by targeting VCP to activate the mTOR signaling

MicroRNAs (miRNAs) regulate multiple biological processes and participate in various cardiovascular diseases. This study aims to investigate the role of miR-339-5p in cardiomyocyte hypertrophy and the involved mechanism. Neonatal rat cardiomyocytes (NRCMs) were cultured and stimulated with isoproterenol (ISO). The hypertrophic responses were monitored by measuring the cell surface area and expression of hypertrophic markers including β-myosin heavy chain (β-MHC) and atrial natriuretic factor (ANF). Bioinformatic prediction tools and dual-luciferase reporter assay were performed to identify the target gene of miR-339-5p. Quantitative real-time polymerase chain reaction and western blot analysis were used to determine the levels of miR-339-5p and its downstream effectors. Our data showed that miR-339-5p was upregulated during cardiomyocyte hypertrophy triggered by ISO. MiR-339-5p overexpression resulted in enlargement of cell size and increased the levels of hypertrophic markers. In contrast, inhibition of miR-339-5p significantly attenuated ISO-induced hypertrophic responses of NRCMs. Valosin-containing protein (VCP), a suppressor of cardiac hypertrophy via inhibiting mechanistic target of rapamycin (mTOR) signaling, was validated as a target of miR-339-5p. MiR-339-5p suppressed VCP protein expression, leading to elevated phosphorylation of mTOR and ribosomal protein S6 kinase (S6K). VCP depletion activated the mTOR/S6K cascade and could compromise the anti-hypertrophic effects of miR-339-5p inhibitor. Additionally, the hypertrophic responses caused by miR-339-5p was alleviated in the presence of mTOR inhibitor rapamycin. In conclusion, our research revealed that miR-339-5p promoted ISO-induced cardiomyocyte hypertrophy by targeting VCP to activate the mTOR signaling, suggesting a promising therapeutic intervention by interfering miR-339-5p.

Functional Inhibition of Valosin-Containing Protein Induces Cardiac Dilation and Dysfunction in a New Dominant-Negative Transgenic Mouse Model

Valosin-containing protein (VCP) was found to play a vital protective role against cardiac stresses. Genetic mutations of VCP are associated with human dilated cardiomyopathy. However, the essential role of VCP in the heart during the physiological condition remains unknown since the VCP knockout in mice is embryonically lethal. We generated a cardiac-specific dominant-negative VCP transgenic (DN-VCP TG) mouse to determine the effects of impaired VCP activity on the heart. Using echocardiography, we showed that cardiac-specific overexpression of DN-VCP induced a remarkable cardiac dilation and progressively declined cardiac function during the aging transition. Mechanistically, DN-VCP did not affect the endogenous VCP (EN-VCP) expression but significantly reduced cardiac ATPase activity in the DN-VCP TG mouse hearts, indicating a functional inhibition. DN-VCP significantly impaired the aging-related cytoplasmic/nuclear shuffling of EN-VCP and its co-factors in the heart tissues and interrupted the balance of the VCP-cofactors interaction between the activating co-factors, ubiquitin fusion degradation protein 1 (UFD-1)/nuclear protein localization protein 4 (NPL-4) complex, and its inhibiting co-factor P47, leading to the binding preference with the inhibitory co-factor, resulting in functional repression of VCP. This DN-VCP TG mouse provides a unique functional-inactivation model for investigating VCP in the heart in physiological and pathological conditions.

Structural and Functional Remodeling of Mitochondria in Cardiac Diseases

Mitochondria undergo structural and functional remodeling to meet the cell demand in response to the intracellular and extracellular stimulations, playing an essential role in maintaining normal cellular function. Merging evidence demonstrated that dysregulation of mitochondrial remodeling is a fundamental driving force of complex human diseases, highlighting its crucial pathophysiological roles and therapeutic potential. In this review, we outlined the progress of the molecular basis of mitochondrial structural and functional remodeling and their regulatory network. In particular, we summarized the latest evidence of the fundamental association of impaired mitochondrial remodeling in developing diverse cardiac diseases and the underlying mechanisms. We also explored the therapeutic potential related to mitochondrial remodeling and future research direction. This updated information would improve our knowledge of mitochondrial biology and cardiac diseases’ pathogenesis, which would inspire new potential strategies for treating these diseases by targeting mitochondria remodeling.

Emerging role of VCP/p97 in cardiovascular diseases: novel insights and therapeutic opportunities

Valosin-containing protein (VCP/p97) is a member of the conserved type II AAA+ (ATPases associated with diverse cellular activities) family of proteins with multiple biological functions, especially in protein homeostasis. Mutations in VCP/p97 are reportedly related to unique autosomal dominant diseases, which may worsen cardiac function. Although the structure of VCP/p97 has been clearly characterized, with reports of high abundance in the heart, research focusing on the molecular mechanisms underpinning the roles of VCP/p97 in the cardiovascular system has been recently undertaken over the past decades. Recent studies have shown that VCP/p97 deficiency affects myocardial fibers and induces heart failure, while overexpression of VCP/p97 eliminates ischemia/reperfusion injury and relieves pathological cardiac hypertrophy caused by cardiac pressure overload, which is related to changes in the mitochondria and calcium overload. However, certain studies have drawn opposing conclusions, including the mitigation of ischemia/reperfusion injury via inhibition of VCP/p97 ATPase activity. Nevertheless, these emerging studies shed light on the role of VCP/p97 and its therapeutic potential in cardiovascular diseases. In other words, VCP/p97 may be involved in the development of cardiovascular disease, and is anticipated to be a new therapeutic target. This review summarizes current findings regarding VCP/p97 in the cardiovascular system for the first time, and discusses the role of VCP/p97 in cardiovascular disease.

Novel genomic targets of valosin-containing protein in protecting pathological cardiac hypertrophy

Pressure overload-induced cardiac hypertrophy, such as that caused by hypertension, is a key risk factor for heart failure. However, the underlying molecular mechanisms remain largely unknown. We previously reported that the valosin-containing protein (VCP), an ATPase-associated protein newly identified in the heart, acts as a significant mediator of cardiac protection against pressure overload-induced pathological cardiac hypertrophy. Still, the underlying molecular basis for the protection is unclear. This study used a cardiac-specific VCP transgenic mouse model to understand the transcriptomic alterations induced by VCP under the cardiac stress caused by pressure overload. Using RNA sequencing and comprehensive bioinformatic analysis, we found that overexpression of the VCP in the heart was able to normalize the pressure overload-stimulated hypertrophic signals by activating G protein-coupled receptors, particularly, the olfactory receptor family, and inhibiting the transcription factor controlling cell proliferation and differentiation. Moreover, VCP overexpression restored pro-survival signaling through regulating alternative splicing alterations of mitochondrial genes. Together, our study revealed a novel molecular regulation mediated by VCP under pressure overload that may bring new insight into the mechanisms involved in protecting against hypertensive heart failure.

The Physiological and Pathological Roles of Mitochondrial Calcium Uptake in Heart

Calcium ion (Ca²⁺) plays a critical role in the cardiac mitochondria function. Ca²⁺ entering the mitochondria is necessary for ATP production and the contractile activity of cardiomyocytes. However, excessive Ca²⁺ in the mitochondria results in mitochondrial dysfunction and cell death. Mitochondria maintain Ca²⁺ homeostasis in normal cardiomyocytes through a comprehensive regulatory mechanism by controlling the uptake and release of Ca²⁺ in response to the cellular demand. Understanding the mechanism of modulating mitochondrial Ca²⁺ homeostasis in the cardiomyocyte could bring new insights into the pathogenesis of cardiac disease and help developing the strategy to prevent the heart from damage at an early stage. In this review, we summarized the latest findings in the studies on the cardiac mitochondrial Ca²⁺ homeostasis, focusing on the regulation of mitochondrial calcium uptake, which acts as a double-edged sword in the cardiac function. Specifically, we discussed the dual roles of mitochondrial Ca²⁺ in mitochondrial activity and the impact on cardiac function, the molecular basis and regulatory mechanisms, and the potential future research interest.

Mitochondrial Surveillance by Cdc48/p97: MAD vs. Membrane Fusion

Cdc48/p97 is a ring-shaped, ATP-driven hexameric motor, essential for cellular viability. It specifically unfolds and extracts ubiquitylated proteins from membranes or protein complexes, mostly targeting them for proteolytic degradation by the proteasome. Cdc48/p97 is involved in a multitude of cellular processes, reaching from cell cycle regulation to signal transduction, also participating in growth or death decisions. The role of Cdc48/p97 in endoplasmic reticulum-associated degradation (ERAD), where it extracts proteins targeted for degradation from the ER membrane, has been extensively described. Here, we present the roles of Cdc48/p97 in mitochondrial regulation. We discuss mitochondrial quality control surveillance by Cdc48/p97 in mitochondrial-associated degradation (MAD), highlighting the potential pathologic significance thereof. Furthermore, we present the current knowledge of how Cdc48/p97 regulates mitofusin activity in outer membrane fusion and how this may impact on neurodegeneration.

Genomic characterization reveals novel mechanisms underlying the valosin-containing protein-mediated cardiac protection against heart failure

Chronic hypertension is a key risk factor for heart failure. However, the underlying molecular mechanisms are not fully understood. Our previous studies found that the valosin-containing protein (VCP), an ATPase-associated protein, was significantly decreased in the hypertensive heart tissues. In this study, we tested the hypothesis that restoration of VCP protected the heart against pressure overload-induced heart failure. With a cardiac-specific transgenic (TG) mouse model, we showed that a moderate increase of VCP was able to attenuate chronic pressure overload-induced maladaptive cardiac hypertrophy and dysfunction. RNA sequencing and a comprehensive bioinformatic analysis further demonstrated that overexpression of VCP in the heart normalized the pressure overload-stimulated hypertrophic signals and repressed the stress-induced inflammatory response. In addition, VCP overexpression promoted cell survival by enhancing the mitochondria resistance to the oxidative stress via activating the Rictor-mediated-gene networks. VCP was also found to be involved in the regulation of the alternative splicing and differential isoform expression for some genes that are related to ATP production and protein synthesis by interacting with long no-coding RNAs and histone deacetylases, indicating a novel epigenetic regulation of VCP in integrating coding and noncoding genomic network in the stressed heart. In summary, our study demonstrated that the rescuing of a deficient VCP in the heart could prevent pressure overload-induced heart failure by rectifying cardiac hypertrophic and inflammatory signaling and enhancing the cardiac resistance to oxidative stress, which brought in novel insights into the understanding of the mechanism of VCP in protecting patients from hypertensive heart failure.

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Deficiency of VCP contributes to the pathogenesis of hypertensive heart failure.

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Rescue of VCP prevents stress-induced cardiac remodeling and cell death.

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VCP attenuates stress-induced inflammatory and hypertrophic signaling.

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VCP promotes cardiac resistance to oxidative stress.

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VCP mediates a novel epigenetic integrating regulation in the stressed heart.

Valosin-Containing Protein, a Calcium-Associated ATPase Protein, in Endoplasmic Reticulum and Mitochondrial Function and Its Implications for Diseases

Endoplasmic reticulum (ER) and mitochondrion are the key organelles in mammal cells and play crucial roles in a variety of biological functions in both physiological and pathological conditions. Valosin-containing protein (VCP), a newly identified calcium-associated ATPase protein, has been found to be involved in both ER and mitochondrial function. Impairment of VCP, caused by structural mutations or alterations of expressions, contributes to the development of various diseases, through an integrating effect on ER, mitochondria and the ubiquitin–proteasome system, by interfering with protein degradation, subcellular translocation and calcium homeostasis. Thus, understanding the role and the molecular mechanisms of VCP in these organelles brings new insights to the pathogenesis of the associated diseases, and leads to the discovery of new therapeutic strategies. In this review, we summarized the progress of studies on VCP, in terms of its regulation of ER and mitochondrial function and its implications for the associated diseases, focusing on the cancers, heart disease, and neurodegenerative disorders.

Melatonin fine-tunes intracellular calcium signals and eliminates myocardial damage through the IP3R/MCU pathways in cardiorenal syndrome type 3

Cardiorenal syndrome type-3 (CRS-3) is characterized by acute cardiac injury induced by acute kidney injury. Here, we investigated the causes of CRS-3 by analyzing cardiac function after renal ischemia-reperfusion injury (IRI) using echocardiography and evaluation of pro-inflammatory markers, calcium balance, mitochondrial function, and cardiomyocyte death. Our results show that renal IRI reduces cardiac diastolic function associated with cardiomyocyte death and inflammatory responses. Renal IRI also disrupts cardiomyocyte energy metabolism, induces calcium overload, and impairs mitochondrial function, as evidenced by reduced mitochondrial membrane potential and increased mitochondrial fission. Further, renal IRI induces phosphorylation of inositol 1,4,5-trisphosphate receptor (IP3R) and expression of mitochondrial calcium uniporter (MCU), resulting in cytoplasmic calcium overload and mitochondrial calcium accumulation. Pretreatment with melatonin attenuates renal IRI-mediated cardiac damage by maintaining myocardial diastolic function and reducing cardiomyocyte death. Melatonin also inhibits IP3R phosphorylation and MCU expression, thereby alleviating cytoplasmic and mitochondrial calcium overload. Blockade of IP3R has similar cardioprotective effects, whereas MCU activation abrogates the melatonin-mediated cardioprotection. These results show that the negative effects of renal IRI on myocardial viability and cardiac function are caused by induced IP3R phosphorylation, MCU upregulation, and calcium overload. Melatonin protects cardiac function against CRS-3 by suppressing IP3R-MCU signaling.