Metabolic regulation of mitochondrial dynamics

USP7 cardiomyocyte specific knockout causes disordered mitochondrial biogenesis and dynamics and early neonatal lethality in mice

BACKGROUND

Ubiquitination is an enzymatic modification involving ubiquitin chains, that can be reversed by deubiquitination (DUB) enzymes. Ubiquitin-specific protease 7 (USP7), which is also known as herpes virus-associated ubiquitin-specific protease (HAUSP), has been shown to play a vital role in cardiovascular diseases. However, the underlying molecular mechanism by which USP7 regulates cardiomyocyte function has not been reported.

METHODS

To understand the physiological function of USP7 in the heart, we constructed cardiomyocyte-specific USP7 conditional knockout mice.

RESULTS

We found that homozygous knockout mice died approximately three weeks after birth, while heterozygous knockout mice grew normally into adulthood. Severe cardiac dysfunction, hypertrophy, fibrosis, and cell apoptosis were observed in cardiomyocyte-specific USP7 knockout mice, and these effects were accompanied by disordered mitochondrial dynamics and cardiometabolic-related proteins.

CONCLUSIONS

In summary, we investigated changes in the growth status and cardiac function of cardiomyocyte-specific USP7 knockout mice, and preliminarily explored the underlying mechanism.

Mitophagy at the crossroads of cancer development: Exploring the role of mitophagy in tumor progression and therapy resistance

Preserving a functional mitochondrial network is crucial for cellular well-being, considering the pivotal role of mitochondria in ensuring cellular survival, especially under stressful conditions. Mitophagy, the selective removal of damaged mitochondria through autophagy, plays a pivotal role in preserving cellular homeostasis by preventing the production of harmful reactive oxygen species from dysfunctional mitochondria. While the involvement of mitophagy in neurodegenerative diseases has been thoroughly investigated, it is becoming increasingly evident that mitophagy plays a significant role in cancer biology. Perturbations in mitophagy pathways lead to suboptimal mitochondrial quality control, catalyzing various aspects of carcinogenesis, including establishing metabolic plasticity, stemness, metabolic reconfiguration of cancer-associated fibroblasts, and immunomodulation. While mitophagy performs a delicate balancing act at the intersection of cell survival and cell death, mounting evidence indicates that, particularly in the context of stress responses induced by cancer therapy, it predominantly promotes cell survival. Here, we showcase an overview of the current understanding of the role of mitophagy in cancer biology and its potential as a target for cancer therapy. Gaining a more comprehensive insight into the interaction between cancer therapy and mitophagy has the potential to reveal novel targets and pathways, paving the way for enhanced treatment strategies for therapy-resistant tumors in the near future.

Resilience to diabetic retinopathy

Chronic elevation of blood glucose at first causes relatively minor changes to the neural and vascular components of the retina. As the duration of hyperglycemia persists, the nature and extent of damage increases and becomes readily detectable. While this second, overt manifestation of diabetic retinopathy (DR) has been studied extensively, what prevents maximal damage from the very start of hyperglycemia remains largely unexplored. Recent studies indicate that diabetes (DM) engages mitochondria-based defense during the retinopathy-resistant phase, and thereby enables the retina to remain healthy in the face of hyperglycemia. Such resilience is transient, and its deterioration results in progressive accumulation of retinal damage. The concepts that co-emerge with these discoveries set the stage for novel intellectual and therapeutic opportunities within the DR field. Identification of biomarkers and mediators of protection from DM-mediated damage will enable development of resilience-based therapies that will indefinitely delay the onset of DR.

Serine 39 in the GTP-binding domain of Drp1 is involved in shaping mitochondrial morphology

Continuous fusion and fission are critical for mitochondrial health. In this study, we further characterize the role played by dynamin-related protein 1 (Drp1) in mitochondrial fission. We show that a single amino acid change in Drp1 at position 39 from serine to alanine (S39A) within the GTP-binding (GTPase) domain results in a fused mitochondrial network in human SH-SY5Y neuroblastoma cells. Interestingly, the phosphorylation of Ser-616 and Ser-637 of Drp1 remains unaffected by the S39A mutation, and mitochondrial bioenergetic profile and cell viability in the S39A mutant were comparable to those observed in the control. This leads us to propose that the serine 39 residue of Drp1 plays a crucial role in mitochondrial distribution through its involvement in the GTPase activity. Furthermore, this amino acid mutation leads to structural anomalies in the mitochondrial network. Taken together, our results contribute to a better understanding of the function of the Drp1 protein.

Sodium butyrate ameliorates high glucose-suppressed neuronal mitophagy by restoring PRKN expression via inhibiting the RELA-HDAC8 complex

Damaged mitochondria accumulation in diabetes is one of the main features that contribute to increased incidence of cognitive impairment by inducing apoptosis. Butyrate is a major metabolite produced by microbiota that has neuroprotective effects by regulating mitochondrial function. However, detailed mechanisms underlying how butyrate can regulate neuronal mitophagy remain unclear. Here, we examined the regulatory effects of sodium butyrate (NaB) on high glucose-induced mitophagy dysregulation, neuronal apoptosis, and cognitive impairment and its underlying mechanisms in human-induced pluripotent stem cell-derived neurons, SH-SY5Ys, and streptozotocin (STZ)-induced diabetic mice. In our results, diabetic mice showed gut-microbiota dysbiosis, especially a decreased number of butyrate-producing bacteria and reduced NaB plasma concentration. NaB ameliorated high glucose-induced neuronal mitochondrial dysfunction by recovering PRKN/Parkin-mediated mitophagy. High glucose-induced reactive oxygen species (ROS) and -inhibited PRKAA/AMPKα stimulated the RELA/p65-HDAC8 complex, which downregulated PRKN protein expression by binding to the PRKN promoter region. NaB restored PRKN expression by blocking RELA nuclear translocation and directly inhibiting HDAC8 in the nucleus. In addition, HDAC8 overexpression inhibited the positive effect of NaB on high glucose-induced mitophagy dysfunction and neuronal apoptosis. Oral administration of NaB improved cognitive impairment in diabetic mice by restoring mitophagy in the hippocampus. Taken together, NaB ameliorates neuronal mitophagy through PRKN restoration by inhibiting RELA-HDAC8 complexes, suggesting that NaB is an important substance for protecting neuronal apoptosis in diabetes-associated cognitive impairment.

Mitochondrial quality control in non-exudative age-related macular degeneration: From molecular mechanisms to structural and functional recovery

Non-exudative age-related macular degeneration (NE-AMD) is the leading blindness cause in the elderly. Clinical and experimental evidence supports that early alterations in macular retinal pigment epithelium (RPE) mitochondria play a key role in NE-AMD-induced damage. Mitochondrial dynamics (biogenesis, fusion, fission, and mitophagy), which is under the central control of AMP-activated kinase (AMPK), in turn, determines mitochondrial quality. We have developed a NE-AMD model in C57BL/6J mice induced by unilateral superior cervical ganglionectomy (SCGx), which progressively reproduces the disease hallmarks circumscribed to the temporal region of the RPE/outer retina that exhibits several characteristics of the human macula. In this work we have studied RPE mitochondrial structure, dynamics, function, and AMPK role on these parameters' regulation at the nasal and temporal RPE from control eyes and at an early stage of experimental NE-AMD (i.e., 4 weeks post-SCGx). Although RPE mitochondrial mass was preserved, their function, which was higher at the temporal than at the nasal RPE in control eyes, was significantly decreased at 4 weeks post-SCGx at the same region. Mitochondria were bigger, more elongated, and with denser cristae at the temporal RPE from control eyes. Exclusively at the temporal RPE, SCGx severely affected mitochondrial morphology and dynamics, together with the levels of phosphorylated AMPK (p-AMPK). AMPK activation with metformin restored RPE p-AMPK levels, and mitochondrial dynamics, structure, and function at 4 weeks post-SCGx, as well as visual function and RPE/outer retina structure at 10 weeks post-SCGx. These results demonstrate a key role of the temporal RPE mitochondrial homeostasis as an early target for NE-AMD-induced damage, and that pharmacological AMPK activation could preserve mitochondrial morphology, dynamics, and function, and, consequently, avoid the functional and structural damage induced by NE-AMD.

TRABD modulates mitochondrial homeostasis and tissue integrity

High TRABD expression is associated with tau pathology in patients with Alzheimer's disease; however, the function of TRABD is unknown. Human TRABD encodes a mitochondrial outer-membrane protein. The loss of TRABD resulted in mitochondrial fragmentation, and TRABD overexpression led to mitochondrial clustering and fusion. The C-terminal tail of the TRABD anchored to the mitochondrial outer membrane and the TraB domain could form homocomplexes. Additionally, TRABD forms complexes with MFN2, MIGA2, and PLD6 to facilitate mitochondrial fusion. Flies lacking dTRABD are viable and have normal lifespans. However, aging flies exhibit reduced climbing ability and abnormal mitochondrial morphology in their muscles. The expression of dTRABD is increased in aged flies. dTRABD overexpression leads to neurodegeneration and enhances tau toxicity in fly eyes. The overexpression of dTRABD also increased reactive oxygen species (ROS), ATP production, and protein turnover in the mitochondria. This study suggested that TRABD-induced mitochondrial malfunctions contribute to age-related neurodegeneration.

Food perception induces fast fragmentation of hepatic mitochondria

Henschke et al. have recently shown that sensory food perception in mice integrated at the hypothalamus would be sufficient to suppress hepatic glucose production in a rapid mechanism involving a newly described AKT-dependent kinase pathway that engages mitochondrial fission dynamics. Exploiting this pathway could guide strategies to treat type 2 diabetes.

The role of mitochondrial dynamics in oocyte and early embryo development

Mitochondrial dysfunction is widely implicated in various human diseases, through mechanisms that go beyond mitochondria's well-established role in energy generation. These dynamic organelles exert vital control over numerous cellular processes, including calcium regulation, phospholipid synthesis, innate immunity, and apoptosis. While mitochondria's importance is acknowledged in all cell types, research has revealed the exceptionally dynamic nature of the mitochondrial network in oocytes and embryos, finely tuned to meet unique needs during gamete and pre-implantation embryo development. Within oocytes, both the quantity and morphology of mitochondria can significantly change during maturation and post-fertilization. These changes are orchestrated by fusion and fission processes (collectively known as mitochondrial dynamics), crucial for energy production, content exchange, and quality control as mitochondria adjust to the shifting energy demands of oocytes and embryos. The roles of proteins that regulate mitochondrial dynamics in reproductive processes have been primarily elucidated through targeted deletion studies in animal models. Notably, impaired mitochondrial dynamics have been linked to female reproductive health, affecting oocyte quality, fertilization, and embryo development. Dysfunctional mitochondria can lead to fertility problems and can have an impact on the success of pregnancy, particularly in older reproductive age women.

Targeted inhibition of branched-chain amino acid metabolism drives apoptosis of glioblastoma by facilitating ubiquitin degradation of Mfn2 and oxidative stress

Glioblastoma is one of the most challenging malignancies with high aggressiveness and invasiveness and its development and progression of glioblastoma highly depends on branched-chain amino acid (BCAA) metabolism. The study aimed to investigate effects of inhibition of BCAA metabolism with cytosolic branched-chain amino acid transaminase (BCATc) Inhibitor 2 on glioblastoma, elucidate its underlying mechanisms, and explore therapeutic potential of targeting BCAA metabolism. The expression of BCATc was upregulated in glioblastoma and BCATc Inhibitor 2 precipitated apoptosis both in vivo and in vitro with the activation of Bax/Bcl2/Caspase-3/Caspase-9 axis. In addition, BCATc Inhibitor 2 promoted K63-linkage ubiquitination of mitofusin 2 (Mfn2), which subsequently caused lysosomal degradation of Mfn2, and then oxidative stress, mitochondrial fission and loss of mitochondrial membrane potential. Furthermore, BCATc Inhibitor 2 treatment resulted in metabolic reprogramming, and significant inhibition of expression of ATP5A, UQCRC2, SDHB and COX II, indicative of suppressed oxidative phosphorylation. Moreover, Mfn2 overexpression or scavenging mitochondria-originated reactive oxygen species (ROS) with mito-TEMPO ameliorated BCATc Inhibitor 2-induced oxidative stress, mitochondrial membrane potential disruption and mitochondrial fission, and abrogated the inhibitory effect of BCATc Inhibitor 2 on glioblastoma cells through PI3K/AKT/mTOR signaling. All of these findings indicate suppression of BCAA metabolism promotes glioblastoma cell apoptosis via disruption of Mfn2-mediated mitochondrial dynamics and inhibition of PI3K/AKT/mTOR pathway, and suggest that BCAA metabolism can be targeted for developing therapeutic agents to treat glioblastoma.

Mitochondrial dysfunction: mechanisms and advances in therapy

Mitochondria, with their intricate networks of functions and information processing, are pivotal in both health regulation and disease progression. Particularly, mitochondrial dysfunctions are identified in many common pathologies, including cardiovascular diseases, neurodegeneration, metabolic syndrome, and cancer. However, the multifaceted nature and elusive phenotypic threshold of mitochondrial dysfunction complicate our understanding of their contributions to diseases. Nonetheless, these complexities do not prevent mitochondria from being among the most important therapeutic targets. In recent years, strategies targeting mitochondrial dysfunction have continuously emerged and transitioned to clinical trials. Advanced intervention such as using healthy mitochondria to replenish or replace damaged mitochondria, has shown promise in preclinical trials of various diseases. Mitochondrial components, including mtDNA, mitochondria-located microRNA, and associated proteins can be potential therapeutic agents to augment mitochondrial function in immunometabolic diseases and tissue injuries. Here, we review current knowledge of mitochondrial pathophysiology in concrete examples of common diseases. We also summarize current strategies to treat mitochondrial dysfunction from the perspective of dietary supplements and targeted therapies, as well as the clinical translational situation of related pharmacology agents. Finally, this review discusses the innovations and potential applications of mitochondrial transplantation as an advanced and promising treatment.

Three-dimensional object geometry of mitochondria-associated signal: 3-D analysis pipeline for two-photon image stacks of cerebrovascular endothelial mitochondria

Increasing evidence indicates the role of mitochondrial and vascular dysfunction in aging and aging-associated pathologies; however, the exact mechanisms and chronological processes remain enigmatic. High-energy demand organs, such as the brain, depend on the health of their mitochondria and vasculature for the maintenance of normal functions, therefore representing vulnerable targets for aging. This methodology article describes an analysis pipeline for three-dimensional (3-D) mitochondria-associated signal geometry of two-photon image stacks of brain vasculature. The analysis methods allow the quantification of mitochondria-associated signals obtained in real time in their physiological environment. In addition, signal geometry results will allow the extrapolation of fission and fusion events under normal conditions, during aging, or in the presence of different pathological conditions, therefore contributing to our understanding of the role mitochondria play in a variety of aging-associated diseases with vascular etiology.NEW & NOTEWORTHY Analysis pipeline for 3-D mitochondria-associated signal geometry of two-photon image stacks of brain vasculature.

Deafness-associated tRNAPhe mutation impaired mitochondrial and cellular integrity

Defects in mitochondrial RNA metabolism have been linked to sensorineural deafness that often occurs as a consequence of damaged or deficient inner ear hair cells. In this report, we investigated the molecular mechanism underlying a deafness-associated tRNAPhe 593T > C mutation that changed a highly conserved uracil to cytosine at position 17 of the DHU-loop. The m.593T > C mutation altered tRNAPhe structure and function, including increased melting temperature, resistance to S1 nuclease-mediated digestion, and conformational changes. The aberrant tRNA metabolism impaired mitochondrial translation, which was especially pronounced by decreases in levels of ND1, ND5, CYTB, CO1, and CO3 harboring higher numbers of phenylalanine. These alterations resulted in aberrant assembly, instability, and reduced activities of respiratory chain enzyme complexes I, III, IV, and intact supercomplexes overall. Furthermore, we found that the m.593T > C mutation caused markedly diminished membrane potential, and increased the production of reactive oxygen species in the mutant cell lines carrying the m.593T > C mutation. These mitochondrial dysfunctions led to the mitochondrial dynamic imbalance via increasing fission with abnormal mitochondrial morphology. Excessive fission impaired the process of autophagy including the initiation phase, formation, and maturation of the autophagosome. In particular, the m.593T > C mutation upregulated the PARKIN-dependent mitophagy pathway. These alterations promoted an intrinsic apoptotic process for the removal of damaged cells. Our findings provide critical insights into the pathophysiology of maternally inherited deafness arising from tRNA mutation-induced defects in mitochondrial and cellular integrity.

High-fat diet exacerbates 1-Bromopropane-induced loss of dopaminergic neurons in the substantia nigra of mice through mitochondrial damage associated necroptotic pathway

In recent years, accumulating evidence supports that occupational exposure to solvents is associated with an increased incidence of Parkinson's disease (PD) among workers. The neurotoxic effects of 1-bromopropane (1-BP), a widely used new-type solvent, are well-established, yet data on its relationship with the etiology of PD remain limited. Simultaneously, high-fat consumption in modern society is recognized as a significant risk factor for PD. However, whether there is a synergistic effect between a high-fat diet and 1-BP exposure remains unclear. In this study, adult C57BL/6 mice were fed either a chow or a high-fat diet for 18 weeks prior to 12-week 1-BP treatment. Subsequent neurobehavioral and neuropathological examinations were conducted to assess the effects of 1-BP exposure on parkinsonian pathology. The results demonstrated that 1-BP exposure produced obvious neurobehavioral abnormalities and dopaminergic degeneration in the nigral region of mice. Importantly, a high-fat diet further exacerbated the impact of 1-BP on motor and cognitive abnormalities in mice. Mechanistic investigation revealed that mitochondrial damage and mtDNA release induced by 1-BP and high-fat diet activate NLRP3 and cGAS-STING pathway- mediated neuroinflammatory response, and ultimately lead to necroptosis of dopaminergic neurons. In summary, our study unveils a potential link between chronic 1-BP exposure and PD-like pathology with motor and no-motor defects in experimental animals, and long-term high-fat diet can further promote 1-BP neurotoxicity, which underscores the pivotal role of environmental factors in the etiology of PD.

Mitochondrial fission inhibition protects against hypertension induced by angiotensin II

Mitochondrial dysfunction has been implicated in various types of cardiovascular disease including hypertension. Mitochondrial fission fusion balance is critical to mitochondrial quality control, whereas enhanced fission has been reported in several models of cardiovascular disease. However, limited information is available regarding the contribution of mitochondrial fission in hypertension. Here, we have tested the hypothesis that inhibition of mitochondrial fission attenuates the development of hypertension and associated vascular remodeling. In C57BL6 mice infused with angiotensin II for 2 weeks, co-treatment of mitochondrial fission inhibitor, mdivi1, significantly inhibited angiotensin II-induced development of hypertension assessed by radiotelemetry. Histological assessment of hearts and aortas showed that mdivi1 inhibited vessel fibrosis and hypertrophy induced by angiotensin II. This was associated with attenuation of angiotensin II-induced decline in mitochondrial aspect ratio seen in both the endothelial and medial layers of aortas. Mdivi1 also mitigated angiotensin II-induced cardiac hypertrophy assessed by heart weight-to-body weight ratio as well as by echocardiography. In ex vivo experiments, mdivi1 inhibited vasoconstriction and abolished the enhanced vascular reactivity by angiotensin II in small mesenteric arteries. Proteomic analysis on endothelial cell culture media with angiotensin II and/or mdivi1 treatment revealed that mdivi1 inhibited endothelial cell hypersecretory phenotype induced by angiotensin II. In addition, mdivi1 attenuated angiotensin II-induced protein induction of periostin, a myofibroblast marker in cultured vascular fibroblasts. In conclusion, these data suggest that mdivi1 prevented angiotensin II-induced hypertension and cardiovascular remodeling via multicellular mechanisms in the vasculature.

Revolutionizing cellular energy: The convergence of mitochondrial dynamics and delivery technologies

The intersection of mitochondrial dynamics and delivery technologies heralds a paradigm shift in cellular biology and therapeutic intervention. Mitochondrial dynamics, encompassing fusion, fission, transport, and mitophagy, are critical for cellular energy production, signaling, and homeostasis. Dysregulation of these processes is implicated in a myriad of diseases, including neurodegenerative disorders, cardiovascular diseases, and cancer. Concurrently, advances in delivery technologies, such as nanocarriers, targeted delivery systems, and gene editing tools, offer unprecedented opportunities to manipulate mitochondrial function directly. This review synthesizes current knowledge on mitochondrial dynamics, examines recent breakthroughs in targeted delivery methods, and explores their potential convergence to modulate cellular energetics for therapeutic purposes. By integrating insights from biology, chemistry, and bioengineering, this review highlights the innovative approaches being developed to enhance mitochondrial function, underscoring the potential of this convergence to address complex diseases. This interdisciplinary perspective not only broadens our understanding of cellular processes but also paves the way for novel therapeutic strategies, marking a significant step forward in the quest for precision medicine and targeted interventions in mitochondrial-related diseases.

CircPTEN-MT from PTEN regulates mitochondrial energy metabolism

Phosphatase and tensin homolog (PTEN) is a multifunctional gene involved in a variety of physiological and pathological processes. Circular RNAs (circRNAs) are generated from back-splicing events during mRNA processing and participate in cell biological processes through binding to RNAs or proteins. However, PTEN-related circRNAs are largely unknown. Here, we report that circPTEN- mitochondria (MT) (hsa_circ_0002934) is a circular RNA encoded by exons 3, 4, and 5 of PTEN and is a critical regulator of mitochondrial energy metabolism. CircPTEN-MT is localized to mitochondria and physically associated with leucine-rich pentatricopeptide repeat-containing protein (LRPPRC), which regulates posttranscriptional gene expression in mitochondria. Knocking down circPTEN-MT reduces the interaction of LRPPRC and steroid receptor RNA activator (SRA) stem-loop interacting RNA binding protein (SLIRP) and inhibits the polyadenylation of mitochondrial mRNA, which decreases the mRNA level of the mitochondrial complex I subunit and reduces mitochondrial membrane potential and adenosine triphosphate production. Our data demonstrate that circPTEN-MT is an important regulator of cellular energy metabolism. This study expands our understanding of the role of PTEN, which produces both linear and circular RNAs with different and independent functions.

A PCR-independent approach for mtDNA enrichment and next-generation sequencing: comprehensive evaluation and clinical application

BACKGROUND

Sequencing the mitochondrial genome has been increasingly important for the investigation of primary mitochondrial diseases (PMD) and mitochondrial genetics. To overcome the limitations originating from PCR-based mtDNA enrichment, we set out to develop and evaluate a PCR-independent approach in this study, named Pime-Seq (PCR-independent mtDNA enrichment and next generation Sequencing).

RESULTS

By using the optimized mtDNA enrichment procedure, the mtDNA reads ratio reached 88.0 ± 7.9% in the sequencing library when applied on human PBMC samples. We found the variants called by Pime-Seq were highly consistent among technical repeats. To evaluate the accuracy and reliability of this method, we compared Pime-Seq with lrPCR based NGS by performing both methods simultaneously on 45 samples, yielding 1677 concordant variants, as well as 146 discordant variants with low-level heteroplasmic fraction, in which Pime-Seq showed higher reliability. Furthermore, we applied Pime-Seq on 4 samples of PMD patients retrospectively, and successfully detected all the pathogenic mtDNA variants. In addition, we performed a prospective study on 192 apparently healthy pregnant women during prenatal screening, in which Pime-Seq identified pathogenic mtDNA variants in 4 samples, providing extra information for better health monitoring in these cases.

CONCLUSIONS

Pime-Seq can obtain highly enriched mtDNA in a PCR-independent manner for high quality and reliable mtDNA deep-sequencing, which provides us an effective and promising tool for detecting mtDNA variants for both clinical and research purposes.

Mitochondria-associated endoplasmic reticulum membranes as a therapeutic target for cardiovascular diseases

Cardiovascular diseases (CVDs) are currently the leading cause of death worldwide. In 2022, the CVDs contributed to 19.8 million deaths globally, accounting for one-third of all global deaths. With an aging population and changing lifestyles, CVDs pose a major threat to human health. Mitochondria-associated endoplasmic reticulum membranes (MAMs) are communication platforms between cellular organelles and regulate cellular physiological functions, including apoptosis, autophagy, and programmed necrosis. Further research has shown that MAMs play a critical role in the pathogenesis of CVDs, including myocardial ischemia and reperfusion injury, heart failure, pulmonary hypertension, and coronary atherosclerosis. This suggests that MAMs could be an important therapeutic target for managing CVDs. The goal of this study is to summarize the protein complex of MAMs, discuss its role in the pathological mechanisms of CVDs in terms of its functions such as Ca2+ transport, apoptotic signaling, and lipid metabolism, and suggest the possibility of MAMs as a potential therapeutic approach.

GTPBP8 modulates mitochondrial fission through a Drp1-dependent process

Mitochondrial fission is a tightly regulated process involving multiple proteins and cell signaling. Despite extensive studies on mitochondrial fission factors, our understanding of the regulatory mechanisms remains limited. This study shows the critical role of a mitochondrial GTPase, GTPBP8, in orchestrating mitochondrial fission in mammalian cells. Depletion of GTPBP8 resulted in drastic elongation and interconnectedness of mitochondria. Conversely, overexpression of GTPBP8 shifted mitochondrial morphology from tubular to fragmented. Notably, the induced mitochondrial fragmentation from GTPBP8 overexpression was inhibited in cells either depleted of the mitochondrial fission protein Drp1 (also known as DNM1L) or carrying mutated forms of Drp1. Importantly, downregulation of GTPBP8 caused an increase in oxidative stress, modulating cell signaling involved in the increased phosphorylation of Drp1 at Ser637. This phosphorylation hindered the recruitment of Drp1 to mitochondria, leading to mitochondrial fission defects. By contrast, GTPBP8 overexpression triggered enhanced recruitment and assembly of Drp1 at mitochondria. In summary, our study illuminates the cellular function of GTPBP8 as a pivotal modulator of the mitochondrial division apparatus, inherently reliant on its influence on Drp1.

Phosphoglycerate mutase 5 exacerbates liver ischemia-reperfusion injury by activating mitochondrial fission

Although the death of hepatocytes is a crucial trigger of liver ischemia-reperfusion (I/R) injury, the regulation of liver I/R-induced hepatocyte death is still poorly understood. Phosphoglycerate mutase 5 (PGAM5), a mitochondrial Serine/Threonine protein phosphatase, regulates mitochondrial dynamics and is involved in the process of both apoptosis and necrotic. However, it is still unclear what role PGAM5 plays in the death of hepatocytes induced by I/R. Using a PGAM5-silence mice model, we investigated the role of PGAM5 in liver I/R injury and its relevant molecular mechanisms. Our data showed that PGAM5 was highly expressed in mice with liver I/R injury. Silence of PGAM5 could decrease I/R-induced hepatocyte death in mice. In subcellular levels, the silence of PGAM5 could restore mitochondrial membrane potential, increase mitochondrial DNA copy number and transcription levels, inhibit ROS generation, and prevent I/R-induced opening of abnormal mPTP. As for the molecular mechanisms, we indicated that the silence of PGAM5 could inhibit Drp1(S616) phosphorylation, leading to a partial reduction of mitochondrial fission. In addition, Mdivi-1 could inhibit mitochondrial fission, decrease hepatocyte death, and attenuate liver I/R injury in mice. In conclusion, our data reveal the molecular mechanism of PGAM5 in driving hepatocyte death through activating mitochondrial fission in liver I/R injury.

Drp1 controls complex II assembly and skeletal muscle metabolism by Sdhaf2 action on mitochondria

The dynamin-related guanosine triphosphatase, Drp1 (encoded by Dnm1l), plays a central role in mitochondrial fission and is requisite for numerous cellular processes; however, its role in muscle metabolism remains unclear. Here, we show that, among human tissues, the highest number of gene correlations with DNM1L is in skeletal muscle. Knockdown of Drp1 (Drp1-KD) promoted mitochondrial hyperfusion in the muscle of male mice. Reduced fatty acid oxidation and impaired insulin action along with increased muscle succinate was observed in Drp1-KD muscle. Muscle Drp1-KD reduced complex II assembly and activity as a consequence of diminished mitochondrial translocation of succinate dehydrogenase assembly factor 2 (Sdhaf2). Restoration of Sdhaf2 normalized complex II activity, lipid oxidation, and insulin action in Drp1-KD myocytes. Drp1 is critical in maintaining mitochondrial complex II assembly, lipid oxidation, and insulin sensitivity, suggesting a mechanistic link between mitochondrial morphology and skeletal muscle metabolism, which is clinically relevant in combatting metabolic-related diseases.

Exposure to different surface-modified polystyrene nanoparticles caused anxiety, depression, and social deficit in mice via damaging mitochondria in neurons

Nanoplastics (NPs) are unavoidable hazardous materials that result from the human production and use of plastics. While there is evidence that NPs can bioaccumulate in the brain, no enough research regarding the pathways by which NPs reach the brain was conducted, and it is also urgently needed to evaluate the health threat to the nervous system. Here, we observed accumulation of polystyrene nanoplastics (PS-NPs) with different surface modifications (PS, PS-COOH, and PS-NH2) in mouse brains. Further studies showed that PS-NPs disrupted the tight junctions between endothelial cells and transport into endothelial cells via the endocytosis and macropinocytosis pathways. Additionally, NPs exposure induced a series of alternations in behavioral tests, including anxiety- and depression-like changes and impaired social interaction performance. Further results identified that NPs could be internalized into neurons and localized in the mitochondria, bringing about mitochondrial dysfunction and a concurrent decline of ATP production, which might be associated with abnormal animal behaviors. The findings provide novel insights into the neurotoxicity of NPs and provide a basis for the formulation of policy on plastic production and usage by relevant government agencies.

Disturbance of mitochondrial dynamics in myocardium of broilers with pulmonary hypertension syndrome

1. The following study investigated the relationship between pulmonary hypertension syndrome (PHS) and mitochondrial dynamics in broiler cardiomyocytes.2. An animal model for PHS was established by injecting broiler chickens with CM-32 cellulose particles. Broiler myocardial cells were cultured under hypoxic conditions to establish an in vitro model. The ascites heart index, histomorphology, mitochondrial ultrastructure, and mitochondrial dynamic-related gene and protein expression were evaluated.3. The myocardial fibres from PHS broilers had wider spaces and were wavy and twisted and the number of mitochondria increased. Compared with the control group, the gene and protein expression levels were decreased for Opa1, Mfn1, and Mfn2 in the myocardium of PHS broilers. The gene and protein expression was significantly increased for Drp1 and Mff.4. This study showed that PHS in broilers may cause myocardial mitochondrial dysfunction, specifically by diminishing mitochondrial fusion and enhancing fission, causing disturbances in the mitochondrial dynamics of the heart.

A detailed review of pharmacology of MFN1 (mitofusion-1)-mediated mitochondrial dynamics: Implications for cellular health and diseases

The mitochondria are responsible for the production of cellular ATP, the regulation of cytosolic calcium levels, and the organization of numerous apoptotic proteins through the release of cofactors necessary for the activation of caspases. This level of functional adaptability can only be attained by sophisticated structural alignment. The morphology of the mitochondria does not remain unchanged throughout time; rather, it undergoes change as a result of processes known as fusion and fission. Fzo in flies, Fzo1 in yeast, and mitofusins in mammals are responsible for managing the outer mitochondrial membrane fusion process, whereas Mgm1 in yeast and optic atrophy 1 in mammals are responsible for managing the inner mitochondrial membrane fusion process. The fusion process is composed of two phases. MFN1, a GTPase that is located on the outer membrane of the mitochondria, is involved in the process of linking nearby mitochondria, maintaining the potential of the mitochondrial membrane, and apoptosis. This article offers specific information regarding the functions of MFN1 in a variety of cells and organs found in living creatures. According to the findings of the literature review, MFN1 plays an important part in a number of diseases and organ systems; nevertheless, the protein's function in other disease models and cell types has to be investigated in the near future so that it can be chosen as a promising marker for the therapeutic and diagnostic potentials it possesses. Overall, the major findings of this review highlight the pivotal role of mitofusin (MFN1) in regulating mitochondrial dynamics and its implications across various diseases, including neurodegenerative disorders, cardiovascular diseases, and metabolic syndromes. Our review identifies novel therapeutic targets within the MFN1 signaling pathways and underscores the potential of MFN1 modulation as a promising strategy for treating mitochondrial-related diseases. Additionally, the review calls for further research into MFN1's molecular mechanisms to unlock new avenues for clinical interventions, emphasizing the need for targeted therapies that address MFN1 dysfunction.

PKM2 induces mitophagy through the AMPK-mTOR pathway promoting CSFV proliferation

Viruses exploit the host cell's energy metabolism system to support their replication. Mitochondria, known as the powerhouse of the cell, play a critical role in regulating cell survival and virus replication. Our prior research indicated that the classical swine fever virus (CSFV) alters mitochondrial dynamics and triggers glycolytic metabolic reprogramming. However, the role and mechanism of PKM2, a key regulatory enzyme of glycolytic metabolism, in CSFV replication remain unclear. In this study, we discovered that CSFV enhances PKM2 expression and utilizes PKM2 to inhibit pyruvate production. Using an affinity purification coupled mass spectrometry system, we successfully identified PKM as a novel interaction partner of the CSFV non-structural protein NS4A. Furthermore, we validated the interaction between PKM2 and both CSFV NS4A and NS5A through co-immunoprecipitation and confocal analysis. PKM2 was found to promote the expression of both NS4A and NS5A. Moreover, we observed that PKM2 induces mitophagy by activating the AMPK-mTOR signaling pathway, thereby facilitating CSFV proliferation. In summary, our data reveal a novel mechanism whereby PKM2, a metabolic enzyme, promotes CSFV proliferation by inducing mitophagy. These findings offer a new avenue for developing antiviral strategies.

IMPORTANCE

Viruses rely on the host cell's material-energy metabolic system for replication, inducing host metabolic disorders and subsequent immunosuppression-a major contributor to persistent viral infections. Classical swine fever virus (CSFV) is no exception. Classical swine fever is a severe acute infectious disease caused by CSFV, resulting in significant economic losses to the global pig industry. While the role of the metabolic enzyme PKM2 (pyruvate dehydrogenase) in the glycolytic pathway of tumor cells has been extensively studied, its involvement in viral infection remains relatively unknown. Our data unveil a new mechanism by which the metabolic enzyme PKM2 mediates CSFV infection, offering novel avenues for the development of antiviral strategies.

Mitochondrial dysfunction route as a possible biomarker and therapy target for human cancer

Mitochondria are vital organelles found within living cells and have signalling, biosynthetic, and bioenergetic functions. Mitochondria play a crucial role in metabolic reprogramming, which is a characteristic of cancer cells and allows them to assure a steady supply of proteins, nucleotides, and lipids to enable rapid proliferation and development. Their dysregulated activities have been associated with the growth and metastasis of different kinds of human cancer, particularly ovarian carcinoma. In this review, we briefly demonstrated the modified mitochondrial function in cancer, including mutations in mtDNA, reactive oxygen species production, dynamics, apoptosis of cells, autophagy, and calcium excess to maintain cancer genesis, progression, and metastasis. Furthermore, the mitochondrial dysfunction pathway for some genomic, proteomic, and metabolomics modifications in ovarian cancer has been studied. Additionally, ovarian cancer has been linked to targeted therapies and biomarkers found through various alteration processes underlying mitochondrial dysfunction, notably targeting reactive oxygen species, metabolites, rewind metabolic pathways, and chemo-resistant ovarian carcinoma cells.

Drp1: Focus on Diseases Triggered by the Mitochondrial Pathway

Drp1 (Dynamin-Related Protein 1) is a cytoplasmic GTPase protein encoded by the DNM1L gene that influences mitochondrial dynamics by mediating mitochondrial fission processes. Drp1 has been demonstrated to play an important role in a variety of life activities such as cell survival, proliferation, migration, and death. Drp1 has been shown to play different physiological roles under different physiological conditions, such as normal and inflammation. Recently studies have revealed that Drp1 plays a critical role in the occurrence, development, and aggravation of a series of diseases, thereby it serves as a potential therapeutic target for them. In this paper, we review the structure and biological properties of Drp1, summarize the biological processes that occur in the inflammatory response to Drp1, discuss its role in various cancers triggered by the mitochondrial pathway and investigate effective methods for targeting Drp1 in cancer treatment. We also synthesized the phenomena of Drp1 involving in the triggering of other diseases. The results discussed herein contribute to our deeper understanding of mitochondrial kinetic pathway-induced diseases and their therapeutic applications. It is critical for advancing the understanding of the mechanisms of Drp1-induced mitochondrial diseases and preventive therapies.

TMEM135 maintains the equilibrium of osteogenesis and adipogenesis by regulating mitochondrial dynamics

BACKGROUND

Disturbance in the differentiation process of bone marrow mesenchymal stem cells (BMSCs) leads to osteoporosis. Mitochondrial dynamics plays a pivotal role in the metabolism and differentiation of BMSCs. However, the mechanisms underlying mitochondrial dynamics and their impact on the differentiation equilibrium of BMSCs remain unclear.

METHODS

We investigated the mitochondrial morphology and markers related to mitochondrial dynamics during BMSCs osteogenic and adipogenic differentiation. Bioinformatics was used to screen potential genes regulating BMSCs differentiation through mitochondrial dynamics. Subsequently, we evaluated the impact of Transmembrane protein 135 (TMEM135) deficiency on bone homeostasis by comparing Tmem135 knockout mice with their littermates. The mechanism of TMEM135 in mitochondrial dynamics and BMSCs differentiation was also investigated in vivo and in vitro.

RESULTS

Distinct changes in mitochondrial morphology were observed between osteogenic and adipogenic differentiation of BMSCs, manifesting as fission in the late stage of osteogenesis and fusion in adipogenesis. Additionally, we revealed that TMEM135, a modulator of mitochondrial dynamics, played a functional role in regulating the equilibrium between adipogenesis and osteogenesis. The TMEM135 deficiency impaired mitochondrial fission and disrupted crucial mitochondrial energy metabolism during osteogenesis. Tmem135 knockout mice showed osteoporotic phenotype, characterized by reduced osteogenesis and increased adipogenesis. Mechanistically, TMEM135 maintained intracellular calcium ion homeostasis and facilitated the dephosphorylation of dynamic-related protein 1 at Serine 637 in BMSCs.

CONCLUSIONS

Our findings underscore the significant role of TMEM135 as a modulator in orchestrating the differentiation trajectory of BMSCs and promoting a shift in mitochondrial dynamics toward fission. This ultimately contributes to the osteogenesis process. This work has provided promising biological targets for the treatment of osteoporosis.

Mitochondria and diabetes: insights and potential therapies

INTRODUCTION

Type 2 diabetes (T2D) presents significant global health and economic challenges, contributing to complications such as stroke, cardiovascular disease, kidney dysfunction, and cancer. The current review explores the crucial role of mitochondria, essential for fuel metabolism, in diabetes-related processes.

AREAS COVERED

Mitochondrial deficits impact insulin-resistant skeletal muscles, adipose tissue, liver, and pancreatic β-cells, affecting glucose and lipid balance. Exercise emerges as a key factor in enhancing mitochondrial function, thereby reducing insulin resistance. Additionally, the therapeutic potential of mitochondrial uncoupling, which generates heat instead of ATP, is discussed. We explore the intricate link between mitochondrial function and diabetes, investigating genetic interventions to mitigate diabetes-related complications. We also cover the impact of insulin deficiency on mitochondrial function, the role of exercise in addressing mitochondrial defects in insulin resistance, and the potential of mitochondrial uncoupling. Furthermore, a comprehensive analysis of Mitochondrial Replacement Therapies (MRT) techniques is presented.

EXPERT OPINION

MRTs hold promise in preventing the transmission of mitochondrial disease. However, addressing ethical, regulatory, and technical considerations is crucial. Integrating mitochondrial-based treatments requires a careful balance between innovation and safety. Ethical dimensions and regulatory aspects of MRT are examined, emphasizing collaborative efforts for the responsible advancement of human health.

Quadriceps muscle atrophy after non-invasive anterior cruciate ligament injury: evidence linking to autophagy and mitophagy

Introduction: Anterior cruciate ligament (ACL) injury is frequently accompanied by quadriceps muscle atrophy, a process closely linked to mitochondrial health and mitochondria-specific autophagy. However, the temporal progression of key quadricep atrophy-mediating events following ACL injury remains poorly understood. To advance our understanding, we conducted a longitudinal study to elucidate key parameters in quadriceps autophagy and mitophagy. Methods: Long-Evans rats were euthanized at 7, 14, 28, and 56 days after non-invasive ACL injury that was induced via tibial compression overload; controls were not injured. Vastus lateralis muscle was extracted, and subsequent immunoblotting analysis was conducted using primary antibodies targeting key proteins involved in autophagy and mitophagy cellular processes. Results: Our findings demonstrated dynamic changes in autophagy and mitophagy markers in the quadriceps muscle during the recovery period after ACL injury. The early response to the injury was characterized by the induction of autophagy at 14 days (Beclin1), indicating an initial cellular response to the injury. Subsequently, at 14 days we observed increase in the elongation of autophagosomes (Atg4B), suggesting a potential remodeling process. The autophagosome flux was also augmented between 14- and 28 days (LC3-II/LC3-I ratio and p62). Notably, at 56 days, markers associated with the elimination of damaged mitochondria were elevated (PINK1, Parkin, and VDAC1), indicating a possible ongoing cellular repair and restoration process. Conclusion: These data highlight the complexity of muscle recovery after ACL injury and underscore the overlooked but crucial role of autophagy and mitophagy in promoting the recovery process.

A new direction in Chinese herbal medicine ameliorates for type 2 diabetes mellitus: Focus on the potential of mitochondrial respiratory chain complexes

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes is a common chronic disease. Chinese herbal medicine (CHM) has a history of several thousand years in the treatment of diabetes, and active components with hypoglycemic effects extracted from various CHM, such as polysaccharides, flavonoids, terpenes, and steroidal saponins, have been widely used in the treatment of diabetes.

AIM OF THE STUDY

Research exploring the potential of various CHM compounds to regulate the mitochondrial respiratory chain complex to improve type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

The literature data were primarily obtained from authoritative databases such as PubMed, CNKI, Wanfang, and others within the last decade. The main keywords used include "type 2 diabetes mellitus", "Chinese medicine", "Chinese herbal medicine", "mitochondrial respiratory chain complex", and "mitochondrial dysfunction".

RESULTS

Chinese herbal medicine primarily regulates the activity of mitochondrial respiratory chain complexes in various tissues such as liver, adipose tissue, skeletal muscle, pancreatic islets, and small intestine. It improves cellular energy metabolism through hypoglycemic, antioxidant, anti-inflammatory and lipid-modulating effects. Different components of CHM can regulate the same mitochondrial respiratory chain complexes, while the same components of a particular CHM can regulate different complex activities. The active components of CHM target different mitochondrial respiratory chain complexes, regulate their aberrant changes and effectively improve T2DM and its complications.

CONCLUSION

Chinese herbal medicine can modulate the function of mitochondrial respiratory chain complexes in various cell types and exert their hypoglycemic effects through various mechanisms. CHM has significant therapeutic potential in regulating mitochondrial respiratory chain complexes to improve T2DM, but further research is needed to explore the underlying mechanisms and conduct clinical trials to assess the safety and efficacy of these medications. This provides new perspectives and opportunities for personalized improvement and innovative developments in diabetes management.

Recent insights into the control of mitochondrial fission

Mitochondria are the powerhouse of the cell. They undergo fission and fusion to maintain cellular homeostasis. In this review, we explore the intricate regulation of mitochondrial fission at various levels, including the protein level, the post-translational modification level, and the organelle level. Malfunctions in mitochondrial fission can have detrimental effects on cells. Therefore, we also examine the association between mitochondrial fission with diseases such as breast cancer and cardiovascular disorders. We anticipate that a comprehensive investigation into the control of mitochondrial fission will pave the way for the development of innovative therapeutic strategies.

Viroporins Manipulate Cellular Powerhouses and Modulate Innate Immunity

Viruses have a wide repertoire of molecular strategies that focus on their replication or the facilitation of different stages of the viral cycle. One of these strategies is mediated by the activity of viroporins, which are multifunctional viral proteins that, upon oligomerization, exhibit ion channel properties with mild ion selectivity. Viroporins facilitate multiple processes, such as the regulation of immune response and inflammasome activation through the induction of pore formation in various cell organelle membranes to facilitate the escape of ions and the alteration of intracellular homeostasis. Viroporins target diverse membranes (such as the cellular membrane), endoplasmic reticulum, and mitochondria. Cumulative data regarding the importance of mitochondria function in multiple processes, such as cellular metabolism, energy production, calcium homeostasis, apoptosis, and mitophagy, have been reported. The direct or indirect interaction of viroporins with mitochondria and how this interaction affects the functioning of mitochondrial cells in the innate immunity of host cells against viruses remains unclear. A better understanding of the viroporin-mitochondria interactions will provide insights into their role in affecting host immune signaling through the mitochondria. Thus, in this review, we mainly focus on descriptions of viroporins and studies that have provided insights into the role of viroporins in hijacked mitochondria.

Cyclin-dependent Kinase 5 and Neurodegenerative Diseases

Neurodegenerative diseases are a group of diseases characterized by the progressive loss of neurons, including Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis. These diseases have a high incidence and mortality rate globally, placing a heavy burden on patients and their families. The pathogenesis of neurodegenerative diseases is complex, and there are no effective treatments at present. Cyclin-dependent kinase 5 is a proline-directed serine/threonine protein kinase that is closely related to the development and function of the nervous system. Under physiological conditions, it is involved in regulating the process of neuronal proliferation, differentiation, migration, and synaptic plasticity. Moreover, there is increasing evidence that cyclin-dependent kinase 5 also plays an important role in the pathogenesis of neurodegenerative diseases. In this review, we address the biological characteristics of cyclin-dependent kinase 5 and its role in neurodegenerative diseases. In particular, this review highlights the underlying mechanistic linkages between cyclin-dependent kinase 5 and mitochondrial dysfunction, oxidative stress and neuroinflammation in the context of neurodegeneration. Finally, we also summarize the currently available cyclin-dependent kinase 5 inhibitors and their prospects for the treatment of neurodegenerative diseases. Taken together, a better understanding of the molecular mechanisms of cyclin-dependent kinase 5 involved in neurodegenerative diseases can lead to the development of new strategies for the prevention and treatment of these devastating diseases.

Deficient tRNA posttranscription modification dysregulated the mitochondrial quality controls and apoptosis

Mitochondria are dynamic organelles in cellular metabolism and physiology. Mitochondrial DNA (mtDNA) mutations are associated with a broad spectrum of clinical abnormalities. However, mechanisms underlying mtDNA mutations regulate intracellular signaling related to the mitochondrial and cellular integrity are less explored. Here, we demonstrated that mt-tRNAMet 4435A>G mutation-induced nucleotide modification deficiency dysregulated the expression of nuclear genes involved in cytosolic proteins involved in oxidative phosphorylation system (OXPHOS) and impaired the assemble and integrity of OXPHOS complexes. These dysfunctions caused mitochondrial dynamic imbalance, thereby increasing fission and decreasing fusion. Excessive fission impaired the process of autophagy including initiation phase, formation, and maturation of autophagosome. Strikingly, the m.4435A>G mutation upregulated the PARKIN dependent mitophagy pathways but downregulated the ubiquitination-independent mitophagy. These alterations promoted intrinsic apoptotic process for the removal of damaged cells. Our findings provide new insights into mechanism underlying deficient tRNA posttranscription modification regulated intracellular signaling related to the mitochondrial and cellular integrity.

Mitochondrial Dysfunction in Kidney Tubulopathies

Mitochondria play a key role in kidney physiology and pathology. They produce ATP to fuel energy-demanding water and solute reabsorption processes along the nephron. Moreover, mitochondria contribute to cellular health by the regulation of autophagy, (oxidative) stress responses, and apoptosis. Mitochondrial abundance is particularly high in cortical segments, including proximal and distal convoluted tubules. Dysfunction of the mitochondria has been described for tubulopathies such as Fanconi, Gitelman, and Bartter-like syndromes and renal tubular acidosis. In addition, mitochondrial cytopathies often affect renal (tubular) tissues, such as in Kearns-Sayre and Leigh syndromes. Nevertheless, the mechanisms by which mitochondrial dysfunction results in renal tubular diseases are only scarcely being explored. This review provides an overview of mitochondrial dysfunction in the development and progression of kidney tubulopathies. Furthermore, it emphasizes the need for further mechanistic investigations to identify links between mitochondrial function and renal electrolyte reabsorption.

Obesity causes mitochondrial fragmentation and dysfunction in white adipocytes due to RalA activation

Mitochondrial dysfunction is a characteristic trait of human and rodent obesity, insulin resistance and fatty liver disease. Here we show that high-fat diet (HFD) feeding causes mitochondrial fragmentation in inguinal white adipocytes from male mice, leading to reduced oxidative capacity by a process dependent on the small GTPase RalA. RalA expression and activity are increased in white adipocytes after HFD. Targeted deletion of RalA in white adipocytes prevents fragmentation of mitochondria and diminishes HFD-induced weight gain by increasing fatty acid oxidation. Mechanistically, RalA increases fission in adipocytes by reversing the inhibitory Ser637 phosphorylation of the fission protein Drp1, leading to more mitochondrial fragmentation. Adipose tissue expression of the human homolog of Drp1, DNM1L, is positively correlated with obesity and insulin resistance. Thus, chronic activation of RalA plays a key role in repressing energy expenditure in obese adipose tissue by shifting the balance of mitochondrial dynamics toward excessive fission, contributing to weight gain and metabolic dysfunction.

In situ architecture of Opa1-dependent mitochondrial cristae remodeling

Cristae membrane state plays a central role in regulating mitochondrial function and cellular metabolism. The protein Optic atrophy 1 (Opa1) is an important crista remodeler that exists as two forms in the mitochondrion, a membrane-anchored long form (l-Opa1) and a processed short form (s-Opa1). The mechanisms for how Opa1 influences cristae shape have remained unclear due to lack of native three-dimensional views of cristae. We perform in situ cryo-electron tomography of cryo-focused ion beam milled mouse embryonic fibroblasts with defined Opa1 states to understand how each form of Opa1 influences cristae architecture. In our tomograms, we observe a variety of cristae shapes with distinct trends dependent on s-Opa1:l-Opa1 balance. Increased l-Opa1 levels promote cristae stacking and elongated mitochondria, while increased s-Opa1 levels correlated with irregular cristae packing and round mitochondria shape. Functional assays indicate a role for l-Opa1 in wild-type apoptotic and calcium handling responses, and show a compromised respiratory function under Opa1 imbalance. In summary, we provide three-dimensional visualization of cristae architecture to reveal relationships between mitochondrial ultrastructure and cellular function dependent on Opa1-mediated membrane remodeling.

Mitochondrial dynamics and colorectal cancer biology: mechanisms and potential targets

Colorectal cancer (CRC) is a significant public health concern, and its development is associated with mitochondrial dysfunction. Mitochondria can adapt to the high metabolic demands of cancer cells owing to their plasticity and dynamic nature. The fusion-fission dynamics of mitochondria play a crucial role in signal transduction and metabolic functions of CRC cells. Enhanced mitochondrial fission promotes the metabolic reprogramming of CRC cells, leading to cell proliferation, metastasis, and chemoresistance. Excessive fission can also trigger mitochondria-mediated apoptosis. In contrast, excessive mitochondrial fusion leads to adenosine triphosphate (ATP) overproduction and abnormal tumor proliferation, whereas moderate fusion protects intestinal epithelial cells from oxidative stress-induced mitochondrial damage, thus preventing colitis-associated cancer (CAC). Therefore, an imbalance in mitochondrial dynamics can either promote or inhibit CRC progression. This review provides an overview of the mechanism underlying mitochondrial fusion-fission dynamics and their impact on CRC biology. This revealed the dual role of mitochondrial fusion-fission dynamics in CRC development and identified potential drug targets. Additionally, this study partially explored mitochondrial dynamics in immune and vascular endothelial cells in the tumor microenvironment, suggesting promising prospects for targeting key fusion/fission effector proteins against CRC.

Extracellular Delivery of Functional Mitochondria Rescues the Dysfunction of CD4+ T Cells in Aging

Mitochondrial dysfunction alters cellular metabolism, increases tissue oxidative stress, and may be principal to the dysregulated signaling and function of CD4+ T lymphocytes in the elderly. In this proof of principle study, it is investigated whether the transfer of functional mitochondria into CD4+ T cells that are isolated from old mice (aged CD4+ T cells), can abrogate aging-associated mitochondrial dysfunction, and improve the aged CD4+ T cell functionality. The results show that the delivery of exogenous mitochondria to aged non-activated CD4+ T cells led to significant mitochondrial proteome alterations highlighted by improved aerobic metabolism and decreased cellular mitoROS. Additionally, mito-transferred aged CD4+ T cells showed improvements in activation-induced TCR-signaling kinetics displaying markers of activation (CD25), increased IL-2 production, enhanced proliferation ex vivo. Importantly, immune deficient mouse models (RAG-KO) showed that adoptive transfer of mito-transferred naive aged CD4+ T cells, protected recipient mice from influenza A and Mycobacterium tuberculosis infections. These findings support mitochondria as targets of therapeutic intervention in aging.

Structural insights into the specific recognition of mitochondrial ribosome-binding factor hsRBFA and 12 S rRNA by methyltransferase METTL15

Mitochondrial rRNA modifications are essential for mitoribosome assembly and its proper function. The m4C methyltransferase METTL15 maintains mitochondrial homeostasis by catalyzing m4C839 located in 12 S rRNA helix 44 (h44). This modification is essential to fine-tuning the ribosomal decoding center and increasing decoding fidelity according to studies of a conserved site in Escherichia coli. Here, we reported a series of crystal structures of human METTL15-hsRBFA-h44-SAM analog, METTL15-hsRBFA-SAM, METTL15-SAM and apo METTL15. The structures presented specific interactions of METTL15 with different substrates and revealed that hsRBFA recruits METTL15 to mitochondrial small subunit for further modification instead of 12 S rRNA. Finally, we found that METTL15 deficiency caused increased reactive oxygen species, decreased membrane potential and altered cellular metabolic state. Knocking down METTL15 caused an elevated lactate secretion and increased levels of histone H4K12-lactylation and H3K9-lactylation. METTL15 might be a suitable model to study the regulation between mitochondrial metabolism and histone lactylation.

HTRA2/OMI-Mediated Mitochondrial Quality Control Alters Macrophage Polarization Affecting Systemic Chronic Inflammation

Systemic chronic inflammation (SCI) due to intrinsic immune over-activation is an important factor in the development of many noninfectious chronic diseases, such as neurodegenerative diseases and diabetes mellitus. Among these immune responses, macrophages are extensively involved in the regulation of inflammatory responses by virtue of their polarization plasticity; thus, dysregulation of macrophage polarization direction is one of the potential causes of the generation and maintenance of SCI. High-temperature demand protein A2 (HtrA2/Omi) is an important regulator of mitochondrial quality control, not only participating in the degradation of mis-accumulated proteins in the mitochondrial unfolded protein response (UPRmt) to maintain normal mitochondrial function through its enzymatic activity, but also participating in the regulation of mitochondrial dynamics-related protein interactions to maintain mitochondrial morphology. Recent studies have also reported the involvement of HtrA2/Omi as a novel inflammatory mediator in the regulation of the inflammatory response. HtrA2/Omi regulates the inflammatory response in BMDM by controlling TRAF2 stabilization in a collagen-induced arthritis mouse model; the lack of HtrA2 ameliorates pro-inflammatory cytokine expression in macrophages. In this review, we summarize the mechanisms by which HtrA2/Omi proteins are involved in macrophage polarization remodeling by influencing macrophage energy metabolism reprogramming through the regulation of inflammatory signaling pathways and mitochondrial quality control, elucidating the roles played by HtrA2/Omi proteins in inflammatory responses. In conclusion, interfering with HtrA2/Omi may become an important entry point for regulating macrophage polarization, providing new research space for developing HtrA2/Omi-based therapies for SCI.

Sirtuins mediate mitochondrial quality control mechanisms: a novel therapeutic target for osteoporosis

Mitochondria plays a role in cell differentiation and apoptosis processes. Maintaining mitochondrial function is critical, and this involves various aspects of mitochondrial quality control such as protein homeostasis, biogenesis, dynamics, and mitophagy. Osteoporosis, a metabolic bone disorder, primarily arises from two factors: the dysregulation between lipogenic and osteogenic differentiation of aging bone marrow mesenchymal stem cells, and the imbalance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Mitochondrial quality control has the potential to mitigate or even reverse the effects. Among the Sirtuin family, consisting of seven Sirtuins (SIRT1-7), SIRT1-SIRT6 play a crucial role in maintaining mitochondrial quality control. Additionally, SIRT1, SIRT3, SIRT6, and SIRT7 are directly involved in normal bone development and homeostasis by modulating bone cells. However, the precise mechanism by which these Sirtuins exert their effects remains unclear. This article reviews the impact of various aspects of mitochondrial quality control on osteoporosis, focusing on how SIRT1, SIRT3, and SIRT6 can improve osteoporosis by regulating mitochondrial protein homeostasis, biogenesis, and mitophagy. Furthermore, we provide an overview of the current state of clinical and preclinical drugs that can activate Sirtuins to improve osteoporosis. Specific Sirtuin-activating compounds are effective, but further studies are needed. The findings of this study may offer valuable insights for future research on osteoporosis and the development of clinical prevention and therapeutic target strategies.

Multiomics Reveals Induction of Neuroblastoma SK-N-BE(2)C Cell Death by Mitochondrial Division Inhibitor 1 through Multiple Effects

Mitochondrial division inhibitor 1 (Mdivi-1) is a well-known synthetic compound aimed at inhibiting dynamin-related protein 1 (Drp1) to suppress mitochondrial fission, making it a valuable tool for studying mitochondrial dynamics. However, its specific effects beyond Drp1 inhibition remain to be confirmed. In this study, we employed integrative proteomics and phosphoproteomics to delve into the molecular responses induced by Mdivi-1 in SK-N-BE(2)C cells. A total of 3070 proteins and 1945 phosphorylation sites were identified, with 880 of them represented as phosphoproteins. Among these, 266 proteins and 97 phosphorylation sites were found to be sensitive to the Mdivi-1 treatment. Functional enrichment analysis unveiled their involvement in serine biosynthesis and extrinsic apoptotic signaling pathways. Through targeted metabolomics, we observed that Mdivi-1 enhanced intracellular serine biosynthesis while reducing the production of C24:1-ceramide. Within these regulated phosphoproteins, dynamic dephosphorylation of proteasome subunit alpha type 3 serine 250 (PSMA3-S250) occurred after Mdivi-1 treatment. Further site-directed mutagenesis experiments revealed that the dephosphorylation-deficient mutant PSMA3-S250A exhibited a decreased cell survival. This research confirms that Mdivi-1's inhibition of mitochondrial division leads to various side effects, ultimately influencing cell survival, rather than solely targeting Drp1 inhibition.

Harnessing the benefits of glycine supplementation for improved pancreatic microcirculation in type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is predominantly managed using insulin replacement therapy, however, pancreatic microcirculatory disturbances play a critical role in T1DM pathogenesis, necessitating alternative therapies. This study aimed to investigate the protective effects of glycine supplementation on pancreatic microcirculation in T1DM. Streptozotocin-induced T1DM and glycine-supplemented mice (n = 6 per group) were used alongside control mice. Pancreatic microcirculatory profiles were determined using a laser Doppler blood perfusion monitoring system and wavelet transform spectral analysis. The T1DM group exhibited disorganized pancreatic microcirculatory oscillation. Glycine supplementation significantly restored regular biorhythmic contraction and relaxation, improving blood distribution patterns. Further-more, glycine reversed the lower amplitudes of endothelial oscillators in T1DM mice. Ultrastructural deterioration of islet microvascular endothelial cells (IMECs) and islet microvascular pericytes, including membrane and organelle damage, collagenous fiber proliferation, and reduced edema, was substantially reversed by glycine supplementation. Additionally, glycine supplementation inhibited the production of IL-6, TNF-α, IFN-γ, pro-MMP-9, and VEGF-A in T1DM, with no significant changes in energetic metabolism observed in glycine-supplemented IMECs. A statistically significant decrease in MDA levels accompanied by an increase in SOD levels was also observed with glycine supplementation. Notably, negative correlations emerged between inflammatory cytokines and microhemodynamic profiles. These findings suggest that glycine supplementation may offer a promising therapeutic approach for protecting against pancreatic microcirculatory dysfunction in T1DM.

Trophoblast Syncytialization: A Metabolic Crossroads

During placentation, villous cytotrophoblast (CTB) stem cells proliferate and fuse, giving rise to the multinucleated syncytiotrophoblast (STB), which represents the terminally differentiated villous layer as well as the maternal-fetal interface. The syncytiotrophoblast is at the forefront of nutrient, gas, and waste exchange while also harboring essential endocrine functions to support pregnancy and fetal development. Considering that mitochondrial dynamics and respiration have been implicated in stem cell fate decisions of several cell types and that the placenta is a mitochondria-rich organ, we will highlight the role of mitochondria in facilitating trophoblast differentiation and maintaining trophoblast function. We discuss both the process of syncytialization and the distinct metabolic characteristics associated with CTB and STB sub-lineages prior to and during syncytialization. As mitochondrial respiration is tightly coupled to redox homeostasis, we emphasize the adaptations of mitochondrial respiration to the hypoxic placental environment. Furthermore, we highlight the critical role of mitochondria in conferring the steroidogenic potential of the STB following differentiation. Ultimately, mitochondrial function and morphological changes centrally regulate respiration and influence trophoblast fate decisions through the production of reactive oxygen species (ROS), whose levels modulate the transcriptional activation or suppression of pluripotency or commitment genes.

Size-dependent and sex-specific negative effects of micro- and nano-sized polystyrene particles in the terrestrial invertebrate model Drosophila melanogaster

Microplastic pollution is believed to be one of the most widespread and long-lasting changes on a global scale. Our understanding that microplastics significantly impact terrestrial systems and are a global change stressor continues to grow. In the present study, we investigated the negative effect of long-term (28 days of exposure in food) polystyrene particles of micro (1.0-1.9 µm, 0.4-0.6 µm) and nano (0.04-0.06 µm) scale, in low doses, on the fruit fly - representing a common, globally distributed terrestrial invertebrate, and a model species in many fields. Our observations involved such parameters as ingestion and transfer of particles, survival, reproduction, changes in ultrastructure and tissue and cell responses in midgut epithelium (the place of direct contact with plastic), ovary, and testis in adults, and transgenerational effects in larvae. These observations may indicate possible toxic effects of the tested substances, even in low doses, that can be expected in other taxa, in terrestrial ecosystems. We observed a negative impact of polystyrene particles on the fruit fly survival, midgut, ovary, and testis, involving ultrastructural alterations, such as autophagy and/or ultimately necrosis in the midgut, triggering oxidative stress and activating processes of antioxidative protection. Despite the changes, midgut function and reproduction were not altered - spermatogenesis and oogenesis proceeded normally. The effect was size-dependent - the smaller the polystyrene particles were, the more substantial was the impact they caused. Ultrastructural changes and studied parameters, i.e., generation of ROS (overproduction of which generates oxidative stress), total glutathione concentration (involved in defense against ROS, acting in distinct pathways), and total antioxidant concentration (the oxidative defense system) showed the highest levels after exposure to the smallest nanoparticles, and vice versa. The effect was also sex-dependent, with male flies being more sensitive. Negative effects in males were more substantial and more prominent, even after contact with larger particles, compared to females. The smaller particles (0.4-0.6 µm, 0.04-0.06 µm) were transferred to the ovary and accumulated in the oocytes. In this case, a transgenerational negative effect was detected in larvae. It was characterized by size-dependent alterations, with smaller particles triggering higher levels of ROS and cellular oxidative response. Only the largest particles (1.0-1.9 µm) did not pass into the gonad and did not alter the larvae. These observations together demonstrated that polystyrene particles of micro- and nanoscale, even in a low dose, can induce numerous negative effects on terrestrial invertebrates.

Salmonella enterica serovar Typhimurium remodels mitochondrial dynamics of macrophages via the T3SS effector SipA to promote intracellular proliferation

Mitochondrial dynamics are critical in cellular energy production, metabolism, apoptosis, and immune responses. Pathogenic bacteria have evolved sophisticated mechanisms to manipulate host cells' mitochondrial functions, facilitating their proliferation and dissemination. Salmonella enterica serovar Typhimurium (S. Tm), an intracellular foodborne pathogen, causes diarrhea and exploits host macrophages for survival and replication. However, S. Tm-associated mitochondrial dynamics during macrophage infection remain poorly understood. In this study, we showed that within macrophages, S. Tm remodeled mitochondrial fragmentation to facilitate intracellular proliferation mediated by Salmonella invasion protein A (SipA), a type III secretion system effector encoded by Salmonella pathogenicity island 1. SipA directly targeted mitochondria via its N-terminal mitochondrial targeting sequence, preventing excessive fragmentation and the associated increase in mitochondrial reactive oxygen species, loss of mitochondrial membrane potential, and release of mitochondrial DNA and cytochrome c into the cytosol. Macrophage replication assays and animal experiments showed that mitochondria and SipA interact to facilitate intracellular replication and pathogenicity of S. Tm. Furthermore, we showed that SipA delayed mitochondrial fragmentation by indirectly inhibiting the recruitment of cytosolic dynamin-related protein 1, which mediates mitochondrial fragmentation. This study revealed a novel mechanism through which S. Tm manipulates host mitochondrial dynamics, providing insights into the molecular interplay that facilitates S. Tm adaptation within host macrophages.

DMSA-coated IONPs trigger oxidative stress, mitochondrial metabolic reprograming and changes in mitochondrial disposition, hindering cell cycle progression of cancer cells

There is increasing interest in modulating the redox homeostasis of tumors since high levels of reactive oxygen species (ROS) make them more vulnerable to changes in these species. Nanomedicine offers promise in this context as such applications may provoke biological responses that induce ROS production. Indeed, iron oxide nanoparticles (IONPs) can induce ROS accumulation through the so-called Fenton reaction of iron, further augmenting the ROS in tumors and overloading the antioxidant system beyond its capacity, thereby driving oxidative stress to a level that is incompatible with cell survival. Here, three different coatings for IONPs were compared to assess their intrinsic capacity to induce ROS production in cells. Of these coatings, dimercaptosuccinic acid-coated IONPs (DMSA-NPs) provoked the strongest ROS production, which was associated with the ability to reprogram the metabolism of cancer cells. This latter phenomenon involved shutting-down oxidative phosphorylation (OXPHOS), shifting mitochondrial morphology towards a more elongated phenotype, reducing the total mitochondrial mass and ultimately, blocking cell proliferation by inducing G0/G1 cell cycle arrest. Consequently, the data obtained highlights the importance of studying the chemical properties of IONPs, presenting DMSA-NPs as a novel tool to induce oxidative stress in cancer cells and alter their cell fate.