bims-mecmid 2021-10-10 papers

bims-mecmid

Biomed News

on Membrane communication in mitochondrial dynamics

Issue of 2021–10–10
ten papers selected by
Mauricio Cardenas Rodriguez, University of Padova

Molecular Machinery and Pathophysiology of Mitochondrial Dynamics.
Advances in Cardiotoxicity Induced by Altered Mitochondrial Dynamics and Mitophagy.
The effect of gestational diabetes on the expression of mitochondrial fusion proteins in placental tissue.
Protective mitochondrial fission induced by stress-responsive protein GJA1-20k.
Mitochondrial Fusion Suppresses Tau Pathology-Induced Neurodegeneration and Cognitive Decline.
Opa1 Prevents Apoptosis and Cisplatin-Induced Ototoxicity in Murine Cochleae.
MFN2 Deficiency Impairs Mitochondrial Transport and Downregulates Motor Protein Expression in Human Spinal Motor Neurons.
Probing Membrane Protein Interactions and Signaling Molecule Homeostasis in Plants by Förster Resonance Energy Transfer Analysis.
SIRT3 mediates Mitofusin 2 ubiquitination and degradation to suppress ischemia reperfusion-induced acute kidney injury.
SIRT3 protects kidneys from ischemia-reperfusion injury by modulating the DRP1 pathway to induce mitochondrial autophagy.

Front Cell Dev Biol. 2021 ;9 743892

Molecular Machinery and Pathophysiology of Mitochondrial Dynamics.

Yi-Han Chiu, Shu-Chuan Amy Lin, Chen-Hsin Kuo, Chia-Jung Li.

  Mitochondria are double-membraned organelles that exhibit fluidity. They are the main site of cellular aerobic respiration, providing energy for cell proliferation, migration, and survival; hence, they are called "powerhouses." Mitochondria play an important role in biological processes such as cell death, cell senescence, autophagy, lipid synthesis, calcium homeostasis, and iron balance. Fission and fusion are active processes that require many specialized proteins, including mechanical enzymes that physically alter mitochondrial membranes, and interface proteins that regulate the interaction of these mechanical proteins with organelles. This review discusses the molecular mechanisms of mitochondrial fusion, fission, and physiopathology, emphasizing the biological significance of mitochondrial morphology and dynamics. In particular, the regulatory mechanisms of mitochondria-related genes and proteins in animal cells are discussed, as well as research trends in mitochondrial dynamics, providing a theoretical reference for future mitochondrial research.

Keywords:  fission; fusion; machinery; mitochondrial dynamics; pathophysiology

DOI:  https://doi.org/10.3389/fcell.2021.743892
Front Cardiovasc Med. 2021 ;8 739095

Advances in Cardiotoxicity Induced by Altered Mitochondrial Dynamics and Mitophagy.

Yiyuan Yin, Haitao Shen.

  Mitochondria are the most abundant organelles in cardiac cells, and are essential to maintain the normal cardiac function, which requires mitochondrial dynamics and mitophagy to ensure the stability of mitochondrial quantity and quality. When mitochondria are affected by continuous injury factors, the balance between mitochondrial dynamics and mitophagy is broken. Aging and damaged mitochondria cannot be completely removed in cardiac cells, resulting in energy supply disorder and accumulation of toxic substances in cardiac cells, resulting in cardiac damage and cardiotoxicity. This paper summarizes the specific underlying mechanisms by which various adverse factors interfere with mitochondrial dynamics and mitophagy to produce cardiotoxicity and emphasizes the crucial role of oxidative stress in mitophagy. This review aims to provide fresh ideas for the prevention and treatment of cardiotoxicity induced by altered mitochondrial dynamics and mitophagy.

Keywords:  cardiotoxicity; mitochondrial dynamics; mitochondrial fission; mitochondrial fusion; mitophagy

DOI:  https://doi.org/10.3389/fcvm.2021.739095
Placenta. 2021 Sep 24. pii: S0143-4004(21)00602-0. [Epub ahead of print]115 106-114

The effect of gestational diabetes on the expression of mitochondrial fusion proteins in placental tissue.

Umut Kerem Kolac, Meryem Kurek Eken, Mustafa Ünübol, Gizem Donmez Yalcin, Abdullah Yalcin.

   INTRODUCTION: Gestational diabetes mellitus (GDM) poses a risk factor for fetal mortality and morbidity by directly affecting the placenta and fetus. Mitochondria are dynamic organelles that play a key role in energy production and conversion in placental tissue. Mitochondrial fusion and fission proteins are important in terms of providing mitochondrial dynamics, the adaptation of the cell to different conditions, and maintaining the metabolic stability of the cells. Although GDM shares many features with Type 2 diabetes mellitus (T2DM), different effects of these conditions on the mother and the child suggest that GDM may have specific pathological effects on placental cells. The aim of this study is to investigate the expression of mitochondrial dynamics, and mitochondrial protein folding markers in placentas from GDM patients and women with pre-existing diabetes mellitus.
METHODS: Placentas were properly collected from women, who had pre-existing diabetes (Pre-DM), from women with gestational diabetes mellitus (GDM) and from healthy (non-diabetic) pregnant women. Levels of mitochondrial fusion markers were determined in these placentas by real time quantitative PCR and Western blot experiments.
RESULTS: mRNA expressions and protein levels of mitochondrial fusion markers, mitofusin 1, mitofusin 2 (MFN1 and MFN2) and optical atrophy 1 (OPA1) proteins were found to be significantly lower in both Pre-DM placentas and those with GDM compared to healthy (non-diabetic) control group. Likewise, proteins involved in mitochondrial protein folding were also found to be significantly reduced compared to control group.
DISCUSSION: Diabetes during pregnancy leads to processes that correlate with mitochondria dysfunction in placenta. Our results showed that mitochondrial fusion markers significantly decrease in placental tissue of women with GDM, compared to the healthy non-diabetic women. The decrease in mitochondrial fusion markers was more severe during GDM compared to the Pre-DM. Our results suggest that there may be differences in the pathophysiology of these conditions.

Keywords:  Gestational diabetes mellitus; Mitochondrial fusion; Placenta

DOI:  https://doi.org/10.1016/j.placenta.2021.09.015
Elife. 2021 10 05. pii: e69207. [Epub ahead of print]10

Protective mitochondrial fission induced by stress-responsive protein GJA1-20k.

Daisuke Shimura, Esther Nuebel, Rachel Baum, Steven E Valdez, Shaohua Xiao, Junco S Warren, Joseph A Palatinus, TingTing Hong, Jared Rutter, Robin M Shaw.

  The Connexin43 gap junction gene GJA1 has one coding exon, but its mRNA undergoes internal translation to generate N-terminal truncated isoforms of Connexin43 with the predominant isoform being only 20 kDa in size (GJA1-20k). Endogenous GJA1-20k protein is not membrane bound and has been found to increase in response to ischemic stress, localize to mitochondria, and mimic ischemic preconditioning protection in the heart. However, it is not known how GJA1-20k benefits mitochondria to provide this protection. Here, using human cells and mice, we identify that GJA1-20k polymerizes actin around mitochondria which induces focal constriction sites. Mitochondrial fission events occur within about 45 s of GJA1-20k recruitment of actin. Interestingly, GJA1-20k mediated fission is independent of canonical Dynamin-Related Protein 1 (DRP1). We find that GJA1-20k-induced smaller mitochondria have decreased reactive oxygen species (ROS) generation and, in hearts, provide potent protection against ischemia-reperfusion injury. The results indicate that stress responsive internally translated GJA1-20k stabilizes polymerized actin filaments to stimulate non-canonical mitochondrial fission which limits ischemic-reperfusion induced myocardial infarction.

Keywords:  GJA1-20k; actin dynamics; cell biology; human; ischemia/reperfusion; mitochondria; mitochondria dynamics; mouse; organ protection

DOI:  https://doi.org/10.7554/eLife.69207
J Alzheimers Dis. 2021 Sep 30.

Mitochondrial Fusion Suppresses Tau Pathology-Induced Neurodegeneration and Cognitive Decline.

Luwen Wang, Mengyu Liu, Ju Gao, Amber M Smith, Hisashi Fujioka, Jingjing Liang, George Perry, Xinglong Wang.

   BACKGROUND: Abnormalities of mitochondrial fission and fusion, dynamic processes known to be essential for various aspects of mitochondrial function, have repeatedly been reported to be altered in Alzheimer's disease (AD). Neurofibrillary tangles are known as a hallmark feature of AD and are commonly considered a likely cause of neurodegeneration in this devastating disease.
OBJECTIVE: To understand the pathological role of mitochondrial dynamics in the context of tauopathy.
METHODS: The widely used P301S transgenic mice of tauopathy (P301S mice) were crossed with transgenic TMFN mice with the forced expression of Mfn2 specifically in neurons to obtain double transgenic P301S/TMFN mice. Brain tissues from 11-month-old non-transgenic (NTG), TMFN, P301S, and P301S/TMFN mice were analyzed by electron microscopy, confocal microscopy, immunoblot, histological staining, and immunostaining for mitochondria, tau pathology, and tau pathology-induced neurodegeneration and gliosis. The cognitive function was assessed by the Barnes maze.
RESULTS: P301S mice exhibited mitochondrial fragmentation and a consistent decrease in Mfn2 compared to age-matched NTG mice. When P301S mice were crossed with TMFN mice (P301S/TMFN mice), neuronal loss, as well as mitochondria fragmentation were significantly attenuated. Greatly alleviated tau hyperphosphorylation, filamentous aggregates, and thioflavin-S positive tangles were also noted in P301S/TMFN mice. Furthermore, P301S/TMFN mice showed marked suppression of neuroinflammation and improved cognitive performance in contrast to P301S mice.
CONCLUSION: These in vivo findings suggest that promoted mitochondrial fusion suppresses toxic tau accumulation and associated neurodegeneration, which may protect against the progression of AD and related tauopathies.

Keywords:  Cognitive decline; Mfn2; mitochondrial dynamics; mitochondrial fusion; neurodegeneration; neuroinflammation; tau pathology

DOI:  https://doi.org/10.3233/JAD-215175
Front Cell Dev Biol. 2021 ;9 744838

Opa1 Prevents Apoptosis and Cisplatin-Induced Ototoxicity in Murine Cochleae.

Tingting Dong, Xuejie Zhang, Yiqing Liu, Shan Xu, Haishuang Chang, Fengqiu Chen, Lulu Pan, Shaoru Hu, Min Wang, Min Lu.

  Optic atrophy1 (OPA1) is crucial for inner mitochondrial membrane (IMM) fusion and essential for maintaining crista structure and mitochondrial morphology. Optic atrophy and hearing impairment are the most prevalent clinical features associated with mutations in the OPA1 gene, but the function of OPA1 in hearing is still unknown. In this study, we examined the ability of Opa1 to protect against cisplatin-induced cochlear cell death in vitro and in vivo. Our results revealed that knockdown of Opa1 affects mitochondrial function in HEI-OC1 and Neuro 2a cells, as evidenced by an elevated reactive oxygen species (ROS) level and reduced mitochondrial membrane potential. The dysfunctional mitochondria release cytochrome c, which triggers apoptosis. Opa1 expression was found to be significantly reduced after cell exposed to cisplatin in HEI-OC1 and Neuro 2a cells. Loss of Opa1 aggravated the apoptosis and mitochondrial dysfunction induced by cisplatin treatment, whereas overexpression of Opa1 alleviated cisplatin-induced cochlear cell death in vitro and in explant. Our results demonstrate that overexpression of Opa1 prevented cisplatin-induced ototoxicity, suggesting that Opa1 may play a vital role in ototoxicity and/or mitochondria-associated cochlear damage.

Keywords:  OPA1; apoptosis; cisplatin; mitochondria; ototoxicity

DOI:  https://doi.org/10.3389/fcell.2021.744838
Front Mol Neurosci. 2021 ;14 727552

MFN2 Deficiency Impairs Mitochondrial Transport and Downregulates Motor Protein Expression in Human Spinal Motor Neurons.

Yongchao Mou, Joshua Dein, Zhenyu Chen, Mrunali Jagdale, Xue-Jun Li.

  Charcot-Marie-Tooth (CMT) disease is one of the most common genetically inherited neurological disorders and CMT type 2A (CMT 2A) is caused by dominant mutations in the mitofusin-2 (MFN2) gene. MFN2 is located in the outer mitochondrial membrane and is a mediator of mitochondrial fusion, with an essential role in maintaining normal neuronal functions. Although loss of MFN2 induces axonal neuropathy, the detailed mechanism by which MFN2 deficiency results in axonal degeneration of human spinal motor neurons remains largely unknown. In this study, we generated MFN2-knockdown human embryonic stem cell (hESC) lines using lentivirus expressing MFN2 short hairpin RNA (shRNA). Using these hESC lines, we found that MFN2 loss did not affect spinal motor neuron differentiation from hESCs but resulted in mitochondrial fragmentation and dysfunction as determined by live-cell imaging. Notably, MFN2-knockodwn spinal motor neurons exhibited CMT2A disease-related phenotypes, including extensive perikaryal inclusions of phosphorylated neurofilament heavy chain (pNfH), frequent axonal swellings, and increased pNfH levels in long-term cultures. Importantly, MFN2 deficit impaired anterograde and retrograde mitochondrial transport within axons, and reduced the mRNA and protein levels of kinesin and dynein, indicating the interfered motor protein expression induced by MFN2 deficiency. Our results reveal that MFN2 knockdown induced axonal degeneration of spinal motor neurons and defects in mitochondrial morphology and function. The impaired mitochondrial transport in MFN2-knockdown spinal motor neurons is mediated, at least partially, by the altered motor proteins, providing potential therapeutic targets for rescuing axonal degeneration of spinal motor neurons in CMT2A disease.

Keywords:  CMT2A; MFN2; human embryonic stem cell; mitochondrial transport; spinal motor neuron

DOI:  https://doi.org/10.3389/fnmol.2021.727552
J Exp Bot. 2021 Oct 05. pii: erab445. [Epub ahead of print]

Probing Membrane Protein Interactions and Signaling Molecule Homeostasis in Plants by Förster Resonance Energy Transfer Analysis.

Zhikun Duan, Kaiwen Li, Wenwen Duan, Junli Zhang, Jingjing Xing.

  Membrane proteins have key functions in signal transduction, transport, and metabolism. Therefore, deciphering the interactions between membrane proteins provides crucial information on signal transduction and the spatiotemporal organization of protein complexes. However, detecting the interactions and behaviors of membrane proteins in their native environments remains difficult. Förster resonance energy transfer (FRET) is a powerful tool for quantifying the dynamic interactions and assembly of membrane proteins without disrupting their local environment, supplying nanometer-scale spatial information and nanosecond-scale temporal information. In this review, we briefly introduce the basic principles of FRET and assess the current state of progress in the development of new FRET techniques (such as FRET-FLIM, Homo-FRET and smFRET) for the analysis of plant membrane proteins. We also describe the various FRET-based biosensors used to quantify the homeostasis of signaling molecules and the active state of kinases. Furthermore, we summarize recent applications of these advanced FRET sensors in probing membrane protein interactions, stoichiometry, and protein clustering, which have shed light on the complex biological functions of membrane proteins in living plant cells.

Keywords:  Förster resonance energy transfer (FRET); assembly stoichiometry; biosensors; membrane microdomains; membrane proteins; protein interaction

DOI:  https://doi.org/10.1093/jxb/erab445
Exp Cell Res. 2021 Oct 05. pii: S0014-4827(21)00415-8. [Epub ahead of print] 112861

SIRT3 mediates Mitofusin 2 ubiquitination and degradation to suppress ischemia reperfusion-induced acute kidney injury.

Lin Shen, Qiufeng Zhang, Shumin Tu, Wentao Qin.

  Ischemia reperfusion-induced acute kidney injury (IR-induced AKI) is a life-threatening disease with many complications. Mitofusin 2 (Mfn2) ubiquitination is related to AKI. But the underlying molecular mechanisms remain unknown. This study aimed to probe the mechanism of Mfn2 ubiquitination in IR-induced AKI development. In IR-induced AKI mouse models, orbital blood and urine were collected for assessing kidney function. The kidney injury, ultrastructure of mitochondria and histopathology in mice were evaluated after injection of G5, an ubiquitination inhibitor. Oxygen glucose deprivation/reoxygenation (OGD/R) models were established in HK-2 cells, and the mitochondria were extracted. Cell viability, apoptosis, oxidative stress, inflammatory reaction, mitochondrial membrane potential and ATP production were measured. Mfn2 ubiquitination in mouse and cell models was evaluated. si-SIRT3 and pcDNA3.1-SIRT3 were transfected into cell models. Consequently, kidney function in mice was impaired by IR-induced AKI. Mfn2 ubiquitination and degradation promoted IR-induced AKI. OGD/R induced renal tubular epithelial cell injury and disrupted mitochondrial dynamics and functions through promoting Mfn2 ubiquitination. SIRT3 knockdown led to Mfn2 ubiquitination by binding to UBC; while its overexpression alleviated tubular epithelial cell injury. Briefly, SIRT3 mediates Mfn2 ubiquitination to relieve IR-induced AKI. This investigation may offer new insights for the treatment of IR-induced AKI injury.

Keywords:  Acute kidney injury; Ischemia reperfusion; Mfn2; Mitochondria; SIRT3; Ubiquitination

DOI:  https://doi.org/10.1016/j.yexcr.2021.112861
Life Sci. 2021 Oct 01. pii: S0024-3205(21)00992-9. [Epub ahead of print] 120005

SIRT3 protects kidneys from ischemia-reperfusion injury by modulating the DRP1 pathway to induce mitochondrial autophagy.

Wenyu Zhao, Mingxing Sui, Rui Chen, Hanlan Lu, Youhua Zhu, Lei Zhang, Li Zeng.

  Renal ischemia-reperfusion injury (IRI) is a leading cause of acute kidney injury (AKI) and may influence renal graft survival. In this study, we investigate the involvement of SIRT3 and DRP1 in mitochondrial autophagy and AKI in a mouse model of IRI. Autophagy was detected in the absence of SIRT3, and hypoxic reoxygenation (H/R) experiments using renal tubular epithelial cells NRK52E were performed in vitro to validate these results. We found that autophagosomes increased following IRI and that the expression of autophagy-related genes was up-regulated. The inhibition of autophagy with 3-methyladenine exacerbated IRI, whereas the DRP1 inhibitor Mdivi-1 reversed this inhibition. Mdivi-1 did not reverse the inhibition of autophagy in the absence of SIRT3. During IRI, Mdivi-1 reduced autophagy and DRP1 expression, whereas SIRT3 overexpression attenuated this condition. Rescue experiment showed that autophagy was increased when both SIRT3 or DRP1 were over- or under-expressed or just DRP1 was under-expressed but expression was reduced when just SIRT3 was under-expressed. However, the expression of DRP1-related molecules was reduced when SIRT3 was overexpressed and when DRP1 was under-expressed. Taken together, these findings indicate that SIRT3 protects against kidney damage from IRI by modulating the DRP1 pathway to induce mitochondrial autophagy.

Keywords:  Acute kidney injury; Ischemia-reperfusion injury; Mitophagy; SIRT3, DRP1

DOI:  https://doi.org/10.1016/j.lfs.2021.120005