Immp2l Mutation Induces Mitochondrial Membrane Depolarization and Complex Ⅲ Activity Suppression after Middle Cerebral Artery Occlusion in Mice

Objective We previously reported that mutations in inner mitochondrial membrane peptidase 2-like(Immp2l)increase infarct volume,enhance superoxide production,and suppress mitochondrial respiration after transient cerebral focal ischemia and reperfusion injury.The present study investigated the impact of heterozygous Immp2l mutation on mitochondria function after ischemia and reperfusion injury in mice.Methods Mice were subjected to middle cerebral artery occlusion for 1 h followed by 0,1,5,and 24 h of reperfusion.The effects of Immp2l^(+/−)on mitochondrial membrane potential,mitochondrial respiratory complex III activity,caspase-3,and apoptosis-inducing factor(AIF)translocation were examined.Results Immp2l^(+/−)increased ischemic brain damage and the number of TUNEL-positive cells compared with wild-type mice.Immp2l^(+/−)led to mitochondrial damage,mitochondrial membrane potential depolarization,mitochondrial respiratory complex III activity suppression,caspase-3 activation,and AIF nuclear translocation.Conclusion The adverse impact of Immp2l^(+/−)on the brain after ischemia and reperfusion might be related to mitochondrial damage that involves depolarization of the mitochondrial membrane potential,inhibition of the mitochondrial respiratory complex III,and activation of mitochondria-mediated cell death pathways.These results suggest that patients with stroke carrying Immp2l^(+/−)might have worse and more severe infarcts,followed by a worse prognosis than those without Immp2l mutations.

lncRNA Gm20257 alleviates pathological cardiac hypertrophy by modulating the PGC-1α–mitochondrial complexⅣaxis

Pathological cardiac hypertrophy,a major contributor to heart failure,is closely linked to mitochondrial function.The roles of long noncoding RNAs(lncRNAs),which regulate mitochondrial function,remain largely unexplored in this context.Herein,a previously unknown lncRNA,Gm20257,was identified.It markedly increased under hypertrophic stress in vivo and in vitro.The suppression of Gm20257 by using small interfering RNAs significantly induced cardiomyocyte hypertrophy.Conversely,the overexpression of Gm20257 through plasmid transfection or adeno-associated viral vector-9 mitigated angiotensinⅡ-induced hypertrophic phenotypes in neonatal mouse ventricular cells or alleviated cardiac hypertrophy in a mouse TAC model respectively,thus restoring cardiac function.Importantly,Gm20257 restored mitochondrial complexⅣlevel and enhanced mitochondrial function.Bioinformatics prediction showed that Gm20257 had a high binding score with peroxisome proliferator–activated receptor coactivator-1(PGC-1α),which could increase mitochondrial complex IV.Subsequently,Western blot analysis results revealed that Gm20257 substantially affected the expression of PGC-1α.Further analyses through RNA immunoprecipitation and immunoblotting following RNA pull-down indicated that PGC-1αwas a direct downstream target of Gm20257.This interaction was demonstrated to rescue the reduction of mitochondrial complex IV induced by hypertrophic stress and promote the generation of mitochondrial ATP.These findings suggest that Gm20257 improves mitochondrial function through the PGC-1α-mitochondrial complexⅣaxis,offering a novel approach for attenuating pathological cardiac hypertrophy.

Complete mitochondrial DNA sequence analysis in two southern Chinese pedigrees with Leber hereditary optic neuropathy revealed secondary mutations along with the primary mutation

AIM: To investigate mitochondrial factors associated with Leber hereditary optic neuropathy (LHON) through complete sequencing and analysis of the mitochondrial genome of Chinese patients with this disease. METHODS: Two unrelated southern Chinese families with LHON and 10 matched healthy controls were recruited, and their entire mitochondrial DNA (mtDNA) was amplified and sequenced with the universal M13 primer. Then DNA sequence analysis and variation identification were performed by DNAssist and Chromas 2 software and compared with authoritative databases such as Mitomap. RESULTS: Mutational analysis of mtDNA in these two Chinese pedigrees revealed one common LHON-associated mutation, G11778A (Arg -> His), in the MT-ND4 gene. In addition, there were two secondary mutations in Pedigree 1: C34971 (Ala -> Val), and C3571T (Leu -> Phe) in the MT-ND1 gene, which have not been reported; and two secondary mutations occurred in Pedigree 2: A10398G (Thr -> Ala) in the MT-ND3 gene, and T14502C (Ile -> Val) in the MT-ND6 gene. Three polymorphisms, A73G, G94A and A263G in the mtDNA control region, were also found. CONCLUSION: Our study confirmed that the known MT-ND4* G11778A mutation is the most significant cause of LHON. The C3497T and C3571T mutations in Pedigree 1 were also both at hot-spots of MT-ND1; they may affect the respiratory chain in coordination with the primary mutation G11778A. In Pedigree 2, the two secondary mutations A10398G of MT-ND3 and T14502C of MT-ND6 may influence mitochondrial respiratory complex I, leading to the mitochondrial respiratory chain dysfunction which results in optic atrophy together with G11778A. Therefore, not only the common primary LHON mutation is responsible for the visual atrophy, but other secondary mtDNA mutations should also be considered when giving genetic counseling.

The conditional mitochondrial protein complexome in the Arabidopsis thaliana root and shoot

Protein complexes are important for almost all biological processes.Hence,to fully understand how cells work,it is also necessary to characterize protein complexes and their dynamics in response to various cellular cues.Moreover,the dynamics of protein interaction play crucial roles in regulating the(dis)association of protein complexes and,in turn,regulating biological processes such as metabolism.Here,mitochondrial protein complexes were investigated by blue native PAGE and size-exclusion chromatography under conditions of oxidative stress in order to monitor their dynamic(dis)associations.Rearrangements of enzyme interactions and changes in protein complex abundance were observed in response to oxidative stress induced by menadione treatment.These included changes in enzymatic protein complexes involving g-amino butyric acid transaminase(GABA-T),D-ornithine aminotransferase(D-OAT),or proline dehydrogenase 1(POX1)that are expected to affect proline metabolism.Menadione treatment also affected interactions between several enzymes of the tricarboxylic acid(TCA)cycle and the abundance of complexes of the oxidative phosphorylation pathway.In addition,we compared the mitochondrial complexes of roots and shoots.Considerable differences between the two tissues were observed in the mitochondrial import/export apparatus,the formation of super-complexes in the oxidative phosphorylation pathway,and specific interactions between enzymes of the TCA cycle that we postulate may be related to the metabolic/energetic requirements of roots and shoots.

Association of TRMT2B gene variants with juvenile amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis(ALS)is a fatal neurodegenerative disease characterized by progressive degeneration of motor neurons,and it demonstrates high clinical heterogeneity and complex genetic architecture.A variation within TRMT2B(c.1356G>T;p.K452N)was identified to be associated with ALS in a family comprising two patients with juvenile ALS(JALS).Two missense variations and one splicing variation were identified in 10 patients with ALS in a cohort with 910 patients with ALS,and three more variants were identified in a public ALS database including 3317 patients with ALS.A decreased number of mitochondria,swollen mitochondria,lower expression of ND1,decreased mitochondrial complex I activities,lower mitochondrial aerobic respiration,and a high level of ROS were observed functionally in patient-originated lymphoblastoid cell lines and TRMT2B interfering HEK293 cells.Further,TRMT2B variations overexpression cells also displayed decreased ND1.In conclusion,a novel JALS-associated gene called TRMT2B was identified,thus broadening the clinical and genetic spectrum of ALS.

Anti-aging effects of chlorpropamide depend on mitochondrial complex-Ⅱ and the production of mitochondrial reactive oxygen species

Sulfonylureas are widely used oral anti-diabetic drugs.However,its long-term usage effects on patients’lifespan remain controversial,with no reports of influence on animal longevity.Hence,the anti-aging effects of chlorpropamide along with glimepiride,glibenclamide,and tolbutamide were studied with special emphasis on the interaction of chlorpropamide with mitochondrial ATP-sensitive K+(mito K-ATP)channels and mitochondrial complex II.Chlorpropamide delayed aging in Caenorhabditis elegans,human lung fibroblast MRC-5 cells and reduced doxorubicin-induced senescence in both MRC-5 cells and mice.In addition,the mitochondrial membrane potential and ATP levels were significantly increased in chlorpropamide-treated worms,which is consistent with the function of its reported targets,mito K-ATP channels.Increased levels of mitochondrial reactive oxygen species(mt ROS)were observed in chlorpropamide-treated worms.Moreover,the lifespan extension by chlorpropamide required complex II and increased mt ROS levels,indicating that chlorpropamide acts on complex II directly or indirectly via mito K-ATP to increase the production of mt ROS as a pro-longevity signal.This study provides mechanistic insight into the anti-aging effects of sulfonylureas in C.elegans.

Thiabendazole inhibits ubiquinone reduction activity of mitochondrial respiratory complex Ⅱ via a water molecule mediated binding feature

The mitochondrial respiratory complex Ⅱ or succinate:ubiquinone oxidoreductase(SQR)is a key membrane complex in both the tricarboxylic acid cycle and aerobic respiration.Five disinfectant compounds were investigated with their potent inhibition effects on the ubiquinone reduction activity of the porcine mitochondrial SQR by enzymatic assay and crystallography.Crystal structure of the SQR bound with thiabendazole(TBZ)reveals a different inhibitor-binding feature at the ubiquinone binding site where a water molecule plays an important role.The obvious inhibitory effect of TBZ based on the biochemical data(IC50~100μmol/L)and the significant structure-based binding affinity calculation(~94μmol/L)draw the suspicion of using TBZ as a good disinfectant compound for nematode infections treatment and fruit storage.

Mitochondrial dysfunction in Parkinson’s disease

Parkinson’s disease(PD)is the second most common neurodegenerative disease,which is characterized by loss of dopaminergic(DA)neurons in the substantia nigra pars compacta and the formation of Lewy bodies and Lewy neurites in surviving DA neurons in most cases.Although the cause of PD is still unclear,the remarkable advances have been made in understanding the possible causative mechanisms of PD pathogenesis.Numerous studies showed that dysfunction of mitochondria may play key roles in DA neuronal loss.Both genetic and environmental factors that are associated with PD contribute to mitochondrial dysfunction and PD pathogenesis.The induction of PD by neurotoxins that inhibit mitochondrial complex I provides direct evidence linking mitochondrial dysfunction to PD.Decrease of mitochondrial complex I activity is present in PD brain and in neurotoxin-or genetic factorinduced PD cellular and animal models.Moreover,PINK1 and parkin,two autosomal recessive PD gene products,have important roles in mitophagy,a cellular process to clear damaged mitochondria.PINK1 activates parkin to ubiquitinate outer mitochondrial membrane proteins to induce a selective degradation of damaged mitochondria by autophagy.In this review,we summarize the factors associated with PD and recent advances in understanding mitochondrial dysfunction in PD.

Mitochondrial dysfunction,oxidative stress and apoptotic induction in microglial BV-2 cells treated with sodium arsenate

The treatment of microglial BV-2 cells with sodium arsenate（As（V）：0.1-400 μmol/L — 48 hr）induces a dose-dependent response.The neurotoxic effects of high concentrations of As（V）（100,200 and 400 μmol/L） are characterized by increased levels of mitochondrial complexesⅠ,Ⅱ,and Ⅳ followed by increased superoxide anion generation.Moreover,As（V） triggers an apoptotic mode of cell death,demonstrated by an apoptotic SubG1 peak,associated with an alteration of plasma membrane integrity.There is also a decrease in transmembrane mitochondrial potential and mitochondrial adenosine triphosphate ATP.It is therefore tempting to speculate that As（V） triggers mitochondrial dysfunction,which may lead to defective oxidative phosphorylation subsequently causing mitochondrial oxidative damage,which in turn induces an apoptotic mode of cell death.