scholarly journals Mitochondrial Calcium Uptake Is Instrumental to Alternative Macrophage Polarization and Phagocytic Activity

2019 ◽  
Vol 20 (19) ◽  
pp. 4966 ◽  
Author(s):  
Tedesco ◽  
Scattolini ◽  
Albiero ◽  
Bortolozzi ◽  
Avogaro ◽  
...  
Keyword(s):  
Phagocytic Activity ◽  
Calcium Uptake ◽  
Macrophage Polarization ◽  
Mitochondrial Calcium ◽  
M2 Macrophage ◽  
M2 Macrophages ◽  
Mitochondrial Calcium Uniporter ◽  
E Coli ◽  
Calcium Uniporter ◽  
Mitochondrial Calcium Uptake

Macrophages are highly plastic and dynamic cells that exert much of their function through phagocytosis. Phagocytosis depends on a coordinated, finely tuned, and compartmentalized regulation of calcium concentrations. We examined the role of mitochondrial calcium uptake and mitochondrial calcium uniporter (MCU) in macrophage polarization and function. In primary cultures of human monocyte-derived macrophages, calcium uptake in mitochondria was instrumental for alternative (M2) macrophage polarization. Mitochondrial calcium uniporter inhibition with KB-R7943 or MCU knockdown, which prevented mitochondrial calcium uptake, reduced M2 polarization, while not affecting classical (M1) polarization. Challenging macrophages with E. coli fragments induced spikes of mitochondrial calcium concentrations, which were prevented by MCU inhibition or silencing. In addition, mitochondria remodelled in M2 macrophages during phagocytosis, especially close to sites of E. coli internalization. Remarkably, inhibition or knockdown of MCU significantly reduced the phagocytic capacity of M2 macrophages. KB-R7943, which also inhibits the membrane sodium/calcium exchanger and Complex I, reduced mitochondria energization and cellular ATP levels, but such effects were not observed with MCU silencing. Therefore, phagocytosis inhibition by MCU knockdown depended on the impaired mitochondrial calcium buffering rather than changes in mitochondrial and cellular energy status. These data uncover a new role for MCU in alternative macrophage polarization and phagocytic activity.

scholarly journals Decision between mitophagy and apoptosis by Parkin via VDAC1 ubiquitination

2020 ◽  
Vol 117 (8) ◽  
pp. 4281-4291 ◽  
Author(s):  
Su Jin Ham ◽  
Daewon Lee ◽  
Heesuk Yoo ◽  
Kyoungho Jun ◽  
Heejin Shin ◽  
...  
Keyword(s):  
Parkinson Disease ◽  
Missense Mutation ◽  
Dopaminergic Neurons ◽  
Calcium Uptake ◽  
Mitochondrial Calcium ◽  
Dependent Manner ◽  
Mitochondrial Calcium Uniporter ◽  
Calcium Uniporter ◽  
Mitochondrial Calcium Uptake ◽  
Transgenic Flies

VDAC1 is a critical substrate of Parkin responsible for the regulation of mitophagy and apoptosis. Here, we demonstrate that VDAC1 can be either mono- or polyubiquitinated by Parkin in a PINK1-dependent manner. VDAC1 deficient with polyubiquitination (VDAC1 Poly-KR) hampers mitophagy, but VDAC1 deficient with monoubiquitination (VDAC1 K274R) promotes apoptosis by augmenting the mitochondrial calcium uptake through the mitochondrial calcium uniporter (MCU) channel. The transgenic flies expressing Drosophila Porin K273R, corresponding to human VDAC1 K274R, show Parkinson disease (PD)-related phenotypes including locomotive dysfunction and degenerated dopaminergic neurons, which are relieved by suppressing MCU and mitochondrial calcium uptake. To further confirm the relevance of our findings in PD, we identify a missense mutation of Parkin discovered in PD patients, T415N, which lacks the ability to induce VDAC1 monoubiquitination but still maintains polyubiquitination. Interestingly, Drosophila Parkin T433N, corresponding to human Parkin T415N, fails to rescue the PD-related phenotypes of Parkin-null flies. Taken together, our results suggest that VDAC1 monoubiquitination plays important roles in the pathologies of PD by controlling apoptosis.

scholarly journals Increased mitochondrial calcium uniporter in adipocytes underlies mitochondrial alterations associated with insulin resistance

2017 ◽  
Vol 313 (6) ◽  
pp. E641-E650 ◽  
Author(s):  
Lauren E. Wright ◽  
Denis Vecellio Reane ◽  
Gabriella Milan ◽  
Anna Terrin ◽  
Giorgia Di Bello ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Calcium Uptake ◽  
Genetic Manipulation ◽  
Mitochondrial Calcium ◽  
Mitochondrial Calcium Uniporter ◽  
Insulin Resistant ◽  
Calcium Uniporter ◽  
Obesity And Diabetes ◽  
Mitochondrial Calcium Uptake

Intracellular calcium influences an array of pathways and affects cellular processes. With the rapidly progressing research investigating the molecular identity and the physiological roles of the mitochondrial calcium uniporter (MCU) complex, we now have the tools to understand the functions of mitochondrial Ca2+ in the regulation of pathophysiological processes. Herein, we describe the role of key MCU complex components in insulin resistance in mouse and human adipose tissue. Adipose tissue gene expression was analyzed from several models of obese and diabetic rodents and in 72 patients with obesity as well as in vitro insulin-resistant adipocytes. Genetic manipulation of MCU activity in 3T3-L1 adipocytes allowed the investigation of the role of mitochondrial calcium uptake. In insulin-resistant adipocytes, mitochondrial calcium uptake increased and several MCU components were upregulated. Similar results were observed in mouse and human visceral adipose tissue (VAT) during the progression of obesity and diabetes. Intriguingly, subcutaneous adipose tissue (SAT) was spared from overt MCU fluctuations. Furthermore, MCU expression returned to physiological levels in VAT of patients after weight loss by bariatric surgery. Genetic manipulation of mitochondrial calcium uptake in 3T3-L1 adipocytes demonstrated that changes in mitochondrial calcium concentration ([Ca2+]mt) can affect mitochondrial metabolism, including oxidative enzyme activity, mitochondrial respiration, membrane potential, and reactive oxygen species formation. Finally, our data suggest a strong relationship between [Ca2+]mt and the release of IL-6 and TNFα in adipocytes. Altered mitochondrial calcium flux in fat cells may play a role in obesity and diabetes and may be associated with the differential metabolic profiles of VAT and SAT.

scholarly journals Structure of the MICU1–MICU2 heterodimer provides insights into the gatekeeping threshold shift

IUCrJ ◽  
2020 ◽  
Vol 7 (2) ◽  
pp. 355-365 ◽  
Author(s):  
Jongseo Park ◽  
Youngjin Lee ◽  
Taein Park ◽  
Jung Youn Kang ◽  
Sang A Mun ◽  
...  
Keyword(s):  
Calcium Uptake ◽  
Mitochondrial Calcium ◽  
Salt Bridges ◽  
Face To Face ◽  
Calcium Uniporter ◽  
Molecular Action ◽  
The Face ◽  
Mitochondrial Calcium Uptake ◽  
Apo State

Mitochondrial calcium uptake proteins 1 and 2 (MICU1 and MICU2) mediate mitochondrial Ca2+ influx via the mitochondrial calcium uniporter (MCU). Its molecular action for Ca2+ uptake is tightly controlled by the MICU1–MICU2 heterodimer, which comprises Ca2+ sensing proteins which act as gatekeepers at low [Ca2+] or facilitators at high [Ca2+]. However, the mechanism underlying the regulation of the Ca2+ gatekeeping threshold for mitochondrial Ca2+ uptake through the MCU by the MICU1–MICU2 heterodimer remains unclear. In this study, we determined the crystal structure of the apo form of the human MICU1–MICU2 heterodimer that functions as the MCU gatekeeper. MICU1 and MICU2 assemble in the face-to-face heterodimer with salt bridges and methionine knobs stabilizing the heterodimer in an apo state. Structural analysis suggests how the heterodimer sets a higher Ca2+ threshold than the MICU1 homodimer. The structure of the heterodimer in the apo state provides a framework for understanding the gatekeeping role of the MICU1–MICU2 heterodimer.

Mitochondrial calcium uniporter affects neutrophil bactericidal activity during Staphylococcus aureus infection

2021 ◽  
Author(s):  
Andrew J. Monteith ◽  
Jeanette M. Miller ◽  
William N. Beavers ◽  
K. Nichole Maloney ◽  
Erin L. Seifert ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Bactericidal Activity ◽  
Ion Flux ◽  
Mitochondrial Calcium ◽  
Dependent Manner ◽  
Mitochondrial Calcium Uniporter ◽  
Mitochondrial Homeostasis ◽  
Mitochondrial Superoxide ◽  
Calcium Uniporter ◽  
Mitochondrial Calcium Uptake

Neutrophils simultaneously restrict Staphylococcus aureus dissemination and facilitate bactericidal activity during infection through the formation of neutrophil extracellular traps (NETs). Neutrophils that produce higher levels of mitochondrial superoxide undergo enhanced terminal NET formation (suicidal NETosis) in response to S. aureus ; however, mechanisms regulating mitochondrial homeostasis upstream of neutrophil antibacterial processes are not fully resolved. Here, we demonstrate that mitochondrial calcium uptake 1 (MICU1)-deficient (MICU1 -/- ) neutrophils accumulate higher levels of calcium and iron within the mitochondria in a mitochondrial calcium uniporter (MCU)-dependent manner. Corresponding with increased ion flux through the MCU, mitochondrial superoxide production is elevated, thereby increasing the propensity for MICU1 -/- neutrophils to undergo suicidal NETosis rather than primary degranulation in response to S. aureus . Increased NET formation augments macrophage killing of bacterial pathogens. Similarly, MICU1 -/- neutrophils alone are not more antibacterial towards S. aureus , but rather enhanced suicidal NETosis by MICU1 -/- neutrophils facilitates increased bactericidal activity in the presence of macrophages. Similarly, mice with a deficiency in MICU1 restricted to cells expressing LysM exhibit lower bacterial burdens in the heart with increased survival during systemic S. aureus infection. Coinciding with the decrease in S. aureus burdens, MICU1 -/- neutrophils in the heart produced higher levels of mitochondrial superoxide and undergo enhanced suicidal NETosis. These results demonstrate that ion flux by the MCU affects the antibacterial function of neutrophils during S. aureus infection.

scholarly journals Transient Mitochondrial Depolarizations Reflect Focal Sarcoplasmic Reticular Calcium Release in Single Rat Cardiomyocytes

1998 ◽  
Vol 142 (4) ◽  
pp. 975-988 ◽  
Author(s):  
Michael R. Duchen ◽  
Anne Leyssens ◽  
Martin Crompton
Keyword(s):  
Calcium Uptake ◽  
Calcium Release ◽  
Mitochondrial Calcium ◽  
Calcium Stores ◽  
Tight Coupling ◽  
Mitochondrial Potential ◽  
Rat Cardiomyocytes ◽  
Calcium Uniporter ◽  
Mitochondrial Calcium Uptake ◽  
Sr Calcium Release

Digital imaging of mitochondrial potential in single rat cardiomyocytes revealed transient depolarizations of mitochondria discretely localized within the cell, a phenomenon that we shall call “flicker.” These events were usually highly localized and could be restricted to single mitochondria, but they could also be more widely distributed within the cell. Contractile waves, either spontaneous or in response to depolarization with 50 mM K+, were associated with propagating waves of mitochondrial depolarization, suggesting that propagating calcium waves are associated with mitochondrial calcium uptake and consequent depolarization. Here we demonstrate that the mitochondrial flicker was directly related to the focal release of calcium from sarcoplasmic reticular (SR) calcium stores and consequent uptake of calcium by local mitochondria. Thus, the events were dramatically reduced by (a) depletion of SR calcium stores after long-term incubation in EGTA or thapsigargin (500 nM); (b) buffering intracellular calcium using BAPTA-AM loading; (c) blockade of SR calcium release with ryanodine (30 μM); and (d) blockade of mitochondrial calcium uptake by microinjection of diaminopentane pentammine cobalt (DAPPAC), a novel inhibitor of the mitochondrial calcium uniporter. These observations demonstrate that focal SR calcium release results in calcium microdomains sufficient to promote local mitochondrial calcium uptake, suggesting a tight coupling of calcium signaling between SR release sites and nearby mitochondria.

scholarly journals The mitochondrial calcium uniporter promotes arrhythmias caused by high-fat diet

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Leroy C. Joseph ◽  
Michael V. Reyes ◽  
Edwin A. Homan ◽  
Blake Gowen ◽  
Uma Mahesh R. Avula ◽  
...  
Keyword(s):  
Mitochondrial Dysfunction ◽  
High Fat Diet ◽  
Calcium Uptake ◽  
Saturated Fat ◽  
Calcium Handling ◽  
Mitochondrial Calcium ◽  
High Fat ◽  
Calcium Uniporter ◽  
Mitochondrial Calcium Uptake

AbstractObesity and diabetes increase the risk of arrhythmia and sudden cardiac death. However, the molecular mechanisms of arrhythmia caused by metabolic abnormalities are not well understood. We hypothesized that mitochondrial dysfunction caused by high fat diet (HFD) promotes ventricular arrhythmia. Based on our previous work showing that saturated fat causes calcium handling abnormalities in cardiomyocytes, we hypothesized that mitochondrial calcium uptake contributes to HFD-induced mitochondrial dysfunction and arrhythmic events. For experiments, we used mice with conditional cardiac-specific deletion of the mitochondrial calcium uniporter (Mcu), which is required for mitochondrial calcium uptake, and littermate controls. Mice were used for in vivo heart rhythm monitoring, perfused heart experiments, and isolated cardiomyocyte experiments. MCU KO mice are protected from HFD-induced long QT, inducible ventricular tachycardia, and abnormal ventricular repolarization. Abnormal repolarization may be due, at least in part, to a reduction in protein levels of voltage gated potassium channels. Furthermore, isolated cardiomyocytes from MCU KO mice exposed to saturated fat are protected from increased reactive oxygen species (ROS), mitochondrial dysfunction, and abnormal calcium handling. Activation of calmodulin-dependent protein kinase (CaMKII) corresponds with the increase in arrhythmias in vivo. Additional experiments showed that CaMKII inhibition protects cardiomyocytes from the mitochondrial dysfunction caused by saturated fat. Hearts from transgenic CaMKII inhibitor mice were protected from inducible ventricular tachycardia after HFD. These studies identify mitochondrial dysfunction caused by calcium overload as a key mechanism of arrhythmia during HFD. This work indicates that MCU and CaMKII could be therapeutic targets for arrhythmia caused by metabolic abnormalities.

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