Abstract P467: Cardiac-specific Deletion Of Voltage Dependent Anion Channel 2 Leads To Dilated Cardiomyopathy By Altering Calcium Homeostasis

Voltage dependent anion channel 2 (VDAC2) is a mitochondrial outer membrane porin known to play a significant role in apoptosis and calcium signaling. Abnormalities in cellular calcium homeostasis often leads to electrical and contractile dysfunction and can cause dilated cardiomyopathy and heart failure. Previous literature suggests that improving mitochondrial calcium uptake via VDAC2 rescues arrhythmia phenotypes in genetic models of impaired cellular calcium signaling. However, the direct role of VDAC2 in intracellular calcium signaling and cardiac function is not well understood. To elucidate the role of VDAC2 in calcium homeostasis, we generated a cardiac-specific deletion of Vdac2 in mice. Our results indicate that loss of VDAC2 in the myocardium during development causes severe impairment in excitation-contraction coupling by reducing mitochondrial calcium uptake (n=3, p<0.05) and thereby impairing intracellular calcium signaling. VDAC2 knock-out mice showed a significant reduction in RYR-mediated calcium release (F/F 0 ) and rate of calcium uptake by SERCA2a [tau(msec)] compared to control mice (N=3, WT=54, KO=38, p<0.0001 (F/F 0 ) and p<0.05 (tau)). We also observed adverse cardiac remodeling which progressed to severe dilated cardiomyopathy and death (N=6, p<0.0001). Reintroducing VDAC2 in 6-week-old knock-out mice partially rescued the cardiomyopathy phenotype evident from improvement in ejection fraction and fractional shortening (n=3, p<0.05). Improving mitochondrial calcium uptake via VDAC2 using a VDAC2 agonist efsevin, increased cardiac contractile force in a mouse model of pressure-overload induced heart failure (N=8, n=22, p<0.05). In conclusion, our findings demonstrate that VDAC2 plays a crucial role in cardiac function by influencing mitochondrial and cellular calcium signaling. Through this role in cellular calcium dynamics and excitation-contraction coupling VDAC2 emerges as a plausible therapeutic target for heart failure.

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Contribution of Mitochondrial Calcium Uptake to Intracellular Calcium Homeostasis Studied with Organelle-Targetted Probes in Skeletal Muscle Fibers

Biophysical Journal ◽

10.1016/j.bpj.2016.11.2170 ◽

2017 ◽

Vol 112 (3) ◽

pp. 400a

Author(s):

Carlo Reggiani ◽

Marta Canato ◽

Paola Capitanio ◽

Lina Cancellara ◽

Feliciano Protasi

Keyword(s):

Skeletal Muscle ◽

Intracellular Calcium ◽

Calcium Homeostasis ◽

Calcium Uptake ◽

Muscle Fibers ◽

Mitochondrial Calcium ◽

Intracellular Calcium Homeostasis ◽

Skeletal Muscle Fibers ◽

Mitochondrial Calcium Uptake

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Cardiac-specific deletion of voltage dependent anion channel 2 leads to dilated cardiomyopathy by altering calcium homeostasis

Nature Communications ◽

10.1038/s41467-021-24869-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Thirupura S. Shankar ◽

Dinesh K. A. Ramadurai ◽

Kira Steinhorst ◽

Salah Sommakia ◽

Rachit Badolia ◽

...

Keyword(s):

Heart Failure ◽

Cardiac Function ◽

Calcium Signaling ◽

Calcium Homeostasis ◽

Anion Channel ◽

Calcium Dynamics ◽

Voltage Dependent Anion Channel ◽

Contraction Coupling ◽

Voltage Dependent

AbstractVoltage dependent anion channel 2 (VDAC2) is an outer mitochondrial membrane porin known to play a significant role in apoptosis and calcium signaling. Abnormalities in calcium homeostasis often leads to electrical and contractile dysfunction and can cause dilated cardiomyopathy and heart failure. However, the specific role of VDAC2 in intracellular calcium dynamics and cardiac function is not well understood. To elucidate the role of VDAC2 in calcium homeostasis, we generated a cardiac ventricular myocyte-specific developmental deletion of Vdac2 in mice. Our results indicate that loss of VDAC2 in the myocardium causes severe impairment in excitation-contraction coupling by altering both intracellular and mitochondrial calcium signaling. We also observed adverse cardiac remodeling which progressed to severe cardiomyopathy and death. Reintroduction of VDAC2 in 6-week-old knock-out mice partially rescued the cardiomyopathy phenotype. Activation of VDAC2 by efsevin increased cardiac contractile force in a mouse model of pressure-overload induced heart failure. In conclusion, our findings demonstrate that VDAC2 plays a crucial role in cardiac function by influencing cellular calcium signaling. Through this unique role in cellular calcium dynamics and excitation-contraction coupling VDAC2 emerges as a plausible therapeutic target for heart failure.

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Mitochondrial calcium uptake regulates tumour progression in embryonal rhabdomyosarcoma

10.1101/2021.11.10.468020 ◽

2021 ◽

Author(s):

Reshma Taneja ◽

Hsin Yao Chiu ◽

Amos Hong Pheng Loh

Keyword(s):

Calcium Homeostasis ◽

Calcium Uptake ◽

Cellular Proliferation ◽

Myogenic Differentiation ◽

Tumour Progression ◽

Embryonal Rhabdomyosarcoma ◽

Mitochondrial Calcium ◽

Mitochondrial Calcium Uptake

Embryonal rhabdomyosarcoma (ERMS) is characterized by a failure of cells to complete skeletal muscle differentiation. Although ERMS cells are vulnerable to oxidative stress, the relevance of mitochondrial calcium homeostasis in oncogenesis is unclear. Here, we show that ERMS cell lines as well as primary tumours exhibit elevated expression of the Mitochondrial Calcium Uniporter (MCU). MCU knockdown resulted in impaired mitochondrial calcium uptake and a reduction in mitochondrial reactive oxygen species (mROS) levels. Phenotypically, MCU knockdown cells exhibited reduced cellular proliferation and motility, with an increased propensity to differentiate in vitro and in vivo. RNA-sequencing of MCU knockdown cells revealed a significant reduction in genes involved in TGF? signalling that play prominent roles in oncogenesis and inhibition of myogenic differentiation. Interestingly, modulation of mROS production impacted TGF? signalling. Our study elucidates mechanisms by which mitochondrial calcium dysregulation promotes tumour progression and suggests that targeting the MCU complex to restore mitochondrial calcium homeostasis could be a therapeutic avenue in ERMS.

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Mitochondria-lysosome contacts regulate mitochondrial Ca2+dynamics via lysosomal TRPML1

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2003236117 ◽

2020 ◽

Vol 117 (32) ◽

pp. 19266-19275 ◽

Cited By ~ 6

Author(s):

Wesley Peng ◽

Yvette C. Wong ◽

Dimitri Krainc

Keyword(s):

Calcium Uptake ◽

Calcium Release ◽

Transient Receptor Potential ◽

Mitochondrial Dynamics ◽

Contact Dynamics ◽

Mitochondrial Calcium ◽

Calcium Dynamics ◽

Voltage Dependent Anion Channel ◽

Contact Sites ◽

Mitochondrial Calcium Uptake

Mitochondria and lysosomes are critical for cellular homeostasis, and dysfunction of both organelles has been implicated in numerous diseases. Recently, interorganelle contacts between mitochondria and lysosomes were identified and found to regulate mitochondrial dynamics. However, whether mitochondria–lysosome contacts serve additional functions by facilitating the direct transfer of metabolites or ions between the two organelles has not been elucidated. Here, using high spatial and temporal resolution live-cell microscopy, we identified a role for mitochondria–lysosome contacts in regulating mitochondrial calcium dynamics through the lysosomal calcium efflux channel, transient receptor potential mucolipin 1 (TRPML1). Lysosomal calcium release by TRPML1 promotes calcium transfer to mitochondria, which was mediated by tethering of mitochondria–lysosome contact sites. Moreover, mitochondrial calcium uptake at mitochondria–lysosome contact sites was modulated by the outer and inner mitochondrial membrane channels, voltage-dependent anion channel 1 and the mitochondrial calcium uniporter, respectively. Since loss of TRPML1 function results in the lysosomal storage disorder mucolipidosis type IV (MLIV), we examined MLIV patient fibroblasts and found both altered mitochondria–lysosome contact dynamics and defective contact-dependent mitochondrial calcium uptake. Thus, our work highlights mitochondria–lysosome contacts as key contributors to interorganelle calcium dynamics and their potential role in the pathophysiology of disorders characterized by dysfunctional mitochondria or lysosomes.

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Abstract 16535: Conditional Knockout of the Mitochondrial 18-kDa Translocator Protein Limits Heart Failure

Circulation ◽

10.1161/circ.132.suppl_3.16535 ◽

2015 ◽

Vol 132 (suppl_3) ◽

Author(s):

Phung Thai ◽

Xiyuan Lu ◽

Daniel Daugherty ◽

Wenbin Deng ◽

Donald M Bers ◽

...

Keyword(s):

Heart Failure ◽

Body Weight ◽

Energy Production ◽

Calcium Uptake ◽

Conditional Knockout ◽

Translocator Protein ◽

Calcium Handling ◽

Mitochondrial Calcium ◽

Mptp Opening ◽

Mitochondrial Calcium Uptake

Introduction: Heart failure results in myocyte and mitochondrial death, and is characterized by abnormalities in mitochondrial calcium handling, energy production, and opening of the mitochondrial permeability transition pore (mPTP). The 18-kDa mitochondrial translocator protein (TSPO) has been shown to be significantly upregulated by heart failure in animals and in explanted hearts from patients, suggesting a vital role for this protein. Hypothesis: In the current experiments, we tested the hypothesis that conditional knockout of the TSPO using Cre inducible TSPO-floxed C57BL/6J mice would limit heart failure resulting from transverse aortic constriction (TAC). Methods: Mice in 4 groups_wild-type (WT) sham, WT TAC, KO sham, and KO TAC_were monitored by weekly echocardiography for 8 weeks, followed by downstream experiments. Results: TAC caused a 46±13% reduction in ejection fraction in WT mice, which was significantly lower in the KO mice (14±10%, P < 0.01, Figure). Strain analysis revealed a significant improvement in radial, longitudinal, and circumferential strain in KO TAC mice, supported by tissue histology finding of significantly less collagen in KO TAC mice. KO TAC mice showed lower heart to body weight and lung to body weight ratios, with no KO TAC mice showing signs of pulmonary edema. Calcium uptake experiment using Rhod-2 AM in isolated cells revealed that KO TAC mice had higher mitochondrial calcium uptake, a crucial finding since mitochondrial calcium uptake has been shown to play a role in energetics and mPTP opening. Conclusion: Genetic modulation of the TSPO limits heart failure due to pressure overload, likely mediated by preserving mitochondrial calcium uptake and energy production, and possibly limiting mPTP opening. These data suggest that pharmacologic interventions that inhibit TSPO expression or function can limit heart failure at the sub-cellular level.

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Spatial Separation of Mitochondrial Calcium Uptake and Extrusion for Energy-Efficient Mitochondrial Calcium Signaling in the Heart

Cell Reports ◽

10.1016/j.celrep.2018.08.040 ◽

2018 ◽

Vol 24 (12) ◽

pp. 3099-3107.e4 ◽

Cited By ~ 17

Author(s):

Sergio De La Fuente ◽

Jonathan P. Lambert ◽

Zuzana Nichtova ◽

Celia Fernandez Sanz ◽

John W. Elrod ◽

...

Keyword(s):

Calcium Signaling ◽

Energy Efficient ◽

Calcium Uptake ◽

Spatial Separation ◽

Mitochondrial Calcium ◽

Mitochondrial Calcium Uptake

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Dysregulation of RyR Calcium Channel and Impaired Mitochondrial Calcium Uptake Cause the Onset of Mitochondrial Retrograde Signaling

SSRN Electronic Journal ◽

10.2139/ssrn.3542583 ◽

2020 ◽

Author(s):

Anindya Roy Chowdhury ◽

Satish Srinivasan ◽

György Csordás ◽

György Hajnóczky ◽

Narayan Avadhani

Keyword(s):

Calcium Channel ◽

Calcium Uptake ◽

Retrograde Signaling ◽

Mitochondrial Calcium ◽

Mitochondrial Retrograde Signaling ◽

Mitochondrial Calcium Uptake

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Cadmium disrupts mitochondrial distribution and activates excessive mitochondrial fission by elevating cytosolic calcium independent of MCU-mediated mitochondrial calcium uptake in its neurotoxicity

Toxicology ◽

10.1016/j.tox.2021.152726 ◽

2021 ◽

pp. 152726

Author(s):

Ju Tang ◽

Weixia Duan ◽

Ping Deng ◽

Huijuan Li ◽

Cong Liu ◽

...

Keyword(s):

Calcium Uptake ◽

Mitochondrial Fission ◽

Cytosolic Calcium ◽

Mitochondrial Calcium ◽

Mitochondrial Distribution ◽

Mitochondrial Calcium Uptake

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An Adult Mouse Model of Dilated Cardiomyopathy Caused by Inducible Cardiac-Specific Bis Deletion

International Journal of Molecular Sciences ◽

10.3390/ijms22031343 ◽

2021 ◽

Vol 22 (3) ◽

pp. 1343

Author(s):

Hye Hyeon Yun ◽

Soon Young Jung ◽

Bong Woo Park ◽

Ji Seung Ko ◽

Kyunghyun Yoo ◽

...

Keyword(s):

Heart Failure ◽

Dilated Cardiomyopathy ◽

Late Onset ◽

Small Heat Shock Protein ◽

Left Ventricular ◽

Therapeutic Interventions ◽

Ventricular Contractility ◽

Knock Out ◽

Multifunctional Protein ◽

Cell Death Suppressor

BCL-2 interacting cell death suppressor (BIS) is a multifunctional protein that has been implicated in cancer and myopathy. Various mutations of the BIS gene have been identified as causative of cardiac dysfunction in some dilated cardiomyopathy (DCM) patients. This was recently verified in cardiac-specific knock-out (KO) mice. In this study, we developed tamoxifen-inducible cardiomyocyte-specific BIS-KO (Bis-iCKO) mice to assess the role of BIS in the adult heart using the Cre-loxP strategy. The disruption of the Bis gene led to impaired ventricular function and subsequent heart failure due to DCM, characterized by reduced left ventricular contractility and dilatation that were observed using serial echocardiography and histology. The development of DCM was confirmed by alterations in Z-disk integrity and increased expression of several mRNAs associated with heart failure and remodeling. Furthermore, aggregation of desmin was correlated with loss of small heat shock protein in the Bis-iCKO mice, indicating that BIS plays an essential role in the quality control of cardiac proteins, as has been suggested in constitutive cardiac-specific KO mice. Our cardiac-specific BIS-KO mice may be a useful model for developing therapeutic interventions for DCM, especially late-onset DCM, based on the distinct phenotypes and rapid progressions.

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