Mitochondrial Protein Function Research Articles

Exploring the role of mitochondrial uncoupling protein 4 in brain metabolism: implications for Alzheimer's disease.

The brain's high demand for energy necessitates tightly regulated metabolic pathways to sustain physiological activity. Glucose, the primary energy substrate, undergoes complex metabolic transformations, with mitochondria playing a central role in ATP production via oxidative phosphorylation. Dysregulation of this metabolic interplay is implicated in Alzheimer's disease (AD), where compromised glucose metabolism, oxidative stress, and mitochondrial dysfunction contribute to disease progression. This review explores the intricate bioenergetic crosstalk between astrocytes and neurons, highlighting the function of mitochondrial uncoupling proteins (UCPs), particularly UCP4, as important regulators of brain metabolism and neuronal function. Predominantly expressed in the brain, UCP4 reduces the membrane potential in the inner mitochondrial membrane, thereby potentially decreasing the generation of reactive oxygen species. Furthermore, UCP4 mitigates mitochondrial calcium overload and sustains cellular ATP levels through a metabolic shift from mitochondrial respiration to glycolysis. Interestingly, the levels of the neuronal UCPs, UCP2, 4 and 5 are significantly reduced in AD brain tissue and a specific UCP4 variant has been associated to an increased risk of developing AD. Few studies modulating the expression of UCP4 in astrocytes or neurons have highlighted protective effects against neurodegeneration and aging, suggesting that pharmacological strategies aimed at activating UCPs, such as protonophoric uncouplers, hold promise for therapeutic interventions in AD and other neurodegenerative diseases. Despite significant advances, our understanding of UCPs in brain metabolism remains in its early stages, emphasizing the need for further research to unravel their biological functions in the brain and their therapeutic potential.

Insights into the Role of VPS39 and Its Interaction with CP204L and A137R in ASFV Infection.

The African swine fever virus (ASFV) is a large and complex DNA virus that causes a highly lethal disease in swine, for which no antiviral drugs or vaccines are currently available. Studying viral-host protein-protein interactions advances our understanding of the molecular mechanisms underlying viral replication and pathogenesis and can facilitate the discovery of antiviral therapeutics. In this study, we employed affinity tagging and purification mass spectrometry to characterize the interactome of VPS39, an important cellular factor during the early phase of ASFV replication. The interaction network of VPS39 revealed associations with mitochondrial proteins involved in membrane contact sites formation and cellular respiration. We show that the ASFV proteins CP204L and A137R target VPS39 by interacting with its clathrin heavy-chain functional domain. Furthermore, we elaborate on the potential mechanisms by which VPS39 may contribute to ASFV replication and prioritize interactions for further investigation into mitochondrial protein function in the context of ASFV infection.

Tissue-specific knockdown of OMM protein via GFP nanobody-mediated degradation

Mitochondria, with their diverse morphologies across tissues, hint at a unique function based on location. For instance, outer mitochondrial membrane (OMM) proteins are critical for various mitochondrial activities, including regulating mitochondrial dynamics, ion homeostasis, and protein translocation. This study introduces a green fluorescent protein (GFP) nanobody-mediated protein degradation (G-DEG) system to investigate tissue-specific mitochondrial functions in Caenorhabditis elegans and potential other model systems. G-DEG combines CRISPR-Cas9 GFP knock-in with ZIF-1-mediated protein degradation, leveraging the high specificity of antigen–antibody recognition for precise manipulation across species. We demonstrate the G-DEG system by targeting FZO-1, a mammalian homolog of MAN1/2, which is essential for mitochondrial fusion. Our protocol includes CRISPR-Cas9-mediated fzo-1:GFP knock-in and the construction of tissue-specific GFP nanobody degradation plasmids for the epidermis, muscle, and neurons. Injection of these plasmids into wild-type C. elegans and subsequent crossbreeding with the fzo-1:GFP knock-in strain allows for effective FZO-1 targeting, providing tissue-specific insights into mitochondrial protein function. Overall, G-DEG emerges as a powerful and versatile tool for tissue-specific knockdown of OMM proteins, paving the way for advanced studies on their diverse biological functions.

Roles of O-GlcNAcylation in Mitochondrial Homeostasis and Cardiovascular Diseases.

Protein posttranslational modifications are important factors that mediate the fine regulation of signaling molecules. O-linked β-N-acetylglucosamine-modification (O-GlcNAcylation) is a monosaccharide modification on N-acetylglucosamine linked to the hydroxyl terminus of serine and threonine of proteins. O-GlcNAcylation is responsive to cellular stress as a reversible and posttranslational modification of nuclear, mitochondrial and cytoplasmic proteins. Mitochondrial proteins are the main targets of O-GlcNAcylation and O-GlcNAcylation is a key regulator of mitochondrial homeostasis by directly regulating the mitochondrial proteome or protein activity and function. Disruption of O-GlcNAcylation is closely related to mitochondrial dysfunction. More importantly, the O-GlcNAcylation of cardiac proteins has been proven to be protective or harmful to cardiac function. Mitochondrial homeostasis is crucial for cardiac contractile function and myocardial cell metabolism, and the imbalance of mitochondrial homeostasis plays a crucial role in the pathogenesis of cardiovascular diseases (CVDs). In this review, we will focus on the interactions between protein O-GlcNAcylation and mitochondrial homeostasis and provide insights on the role of mitochondrial protein O-GlcNAcylation in CVDs.

TSPO deficiency exacerbates acute lung injury via NLRP3 inflammasome-mediated pyroptosis.

Acute respiratory distress syndrome (ARDS) is a common cause of respiratory failure in many critically ill patients. Although inflammasome activation plays an important role in the induction of acute lung injury (ALI) and ARDS, the regulatory mechanism of this process is still unclear. When cells are stimulated by inflammation, the integrity and physiological function of mitochondria play a crucial part in pyroptosis. However, the underlying mechanisms and function of mitochondrial proteins in the process of pyroptosis are largely not yet known. Here, we identified the 18-kDa translocator protein (TSPO), a mitochondrial outer membrane protein, as an important mediator regulating nucleotide-binding domain, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome activation in macrophages during ALI. TSPO gene knockout (KO) and lipopolysaccharide (LPS)-induced ALI/ARDS mouse models were employed to investigate the biological role of TSPO in the pathogenesis of ARDS. Murine macrophages were used to further characterize the effect of TSPO on the NLRP3 inflammasome pathway. Activation of NLRP3 inflammasome was preformed through LPS+adenosine triphosphate (ATP) co-stimulation, followed by detection of mitochondrial membrane potential, reactive oxygen species (ROS) production, and cell death to evaluate the potential biological function of TSPO. Comparisons between two groups were performed with a two-sided unpaired t -test. TSPO- KO mice exhibited more severe pulmonary inflammation in response to LPS-induced ALI. TSPO deficiency resulted in enhanced activation of the NLRP3 inflammasome pathway, promoting more proinflammatory cytokine production of macrophages in LPS-injured lung tissue, including interleukin (IL)-1β, IL-18, and macrophage inflammatory protein (MIP)-2. Mitochondria in TSPO -KO macrophages tended to depolarize in response to cellular stress. The increased production of mitochondrial damage-associated molecular pattern led to enhanced mitochondrial membrane depolarization and pyroptosis in TSPO -KO cells. TSPO may be the key regulator of cellular pyroptosis, and it plays a vital protective role in ARDS occurrence and development.

Mitochondrial Translocase TOMM22 Is Overexpressed in Pancreatic Cancer and Promotes Aggressive Growth by Modulating Mitochondrial Protein Import and Function.

TOMM22 bears potential for early diagnostic/prognostic biomarker development and therapeutic targeting for better management of patients with pancreatic cancer.

Assembly and phylogeographical analysis of novel Taenia solium mitochondrial genomes suggest stratification within the African-American genotype

BackgroundTaenia solium is a parasite of public health concern, causing human taeniasis and cysticercosis. Two main genotypes have been identified: Asian and African-American. Although characterizing T. solium genotypes is crucial to understanding the genetic epidemiology of its diseases, not much is known about the differences between T. solium mitochondrial genomes from different genotypes. Also, little is known about whether genotypes are further subdivided. Therefore, this study aimed to identify a set of point mutations distributed throughout the T. solium mitochondrial genome that differentiate the African-American from the Asian genotype. Another objective was to identify whether T. solium main genotypes are further stratified.MethodsOne Mexican and two Peruvian T. solium mitochondrial genomes were assembled using reads available in the NCBI Sequence Read Archive and the reference genome from China as a template. Mutations with respect to the Chinese reference were identified by multiple genome alignment. Jensen–Shannon and Grantham scores were computed for mutations in protein-coding genes to evaluate whether they affected protein function. Phylogenies by Bayesian inference and haplotype networks were constructed using cytochrome c oxidase subunit 1 and cytochrome b from these genomes and other isolates to infer phylogeographical relationships.ResultsA set of 31 novel non-synonymous point mutations present in all genomes of the African-American genotype were identified. These mutations were distributed across the mitochondrial genome, differentiating the African-American from the Asian genotype. All occurred in non-conserved protein positions. Furthermore, the analysis suggested a stratification of the African-American genotypes into an East African and a West African sublineage.ConclusionsA novel set of 31 non-synonymous mutations differentiating the main T. solium genotypes was identified. None of these seem to be causing differences in mitochondrial protein function between parasites of the two genotypes. Furthermore, two sublineages within the African-American genotype are proposed for the first time. The presence of the East African sublineage in the Americas suggests an underestimated connection between East African and Latin American countries that might have arisen in the major slave trade between Portuguese Mozambique and the Americas. The results obtained here help to complete the molecular epidemiology of the parasite.Graphical

Sperm acrosomal released proteome reveals MDH and VDAC3 from mitochondria are involved in acrosome formation during spermatogenesis in Eriocheir sinensis

Acrosome is inextricably related to membranous organelles. The origin of acrosome is still controversial, one reason is that limited articles were reported about the proteomic analysis of the acrosome. Mitochondrial proteins were found exist in the acrosome, nevertheless, only limited attention has been paid to the function of mitochondrial proteins in the acrosome formation. Eriocheir sinensis sperm has a large acrosome, which makes it an ideal model to study acrosome formation. Here, we firstly compared the rate of acrosome reaction induced by the calcium ionophore A23187 and ionomycin. The rate of acrosome reaction induced by ionomycin is higher (95.8%) than A23187 (58.7%). Morphological changes were observed using light, confocal and transmission electron microscopy. Further more, proteins released during the acrosome reaction as induced by ionomycin were collected for LC-MS/MS analysis. A total of 945 proteins, including malate dehydrogenase (MDH) and voltage-dependent anion channel 3 (VDAC3), were identified in the acrosomal released proteome. The number of proteins from mitochondria (17.57%) was higher compared with endoplasmic reituculum (1.59%) and lysosomes (1.8%). To investigate the functions of target mitochondrial proteins during spermatogenesis, poly-antibodies of MDH in E. sinensis were prepared. The characteristics, further analyzed using immunofluorescence, of two mitochondrial proteins during acrosome formation showed that MDH and VDAC3 were independently involved in the formation of acrosomal membrane. These findings illustrate the acrosomal released proteome and provide important data resource for understanding the relationship between mitochondria and the acrosome in Decapoda crustacean.

Mitophagy: From the dark into the spotlight

Despite the generally placid appearance of plants, many dynamic processes take place inside a plant cell. One such process that has garnered attention in recent years is termed 'autophagy'. While originally discovered in yeast, our understanding of autophagy in plants has improved significantly. Autophagy is considered a cellular recycling system in which cellular components or even entire organelles can be encapsulated by a membrane structure (autophagosome) and then transported to the vacuole (in plants) for degradation and re-use. One example of components degraded by autophagy are the mitochondria ('mitophagy'). Only a few years ago there was almost no information about plant mitophagy available, but lately several important studies have been published. A recent study identified an ATG8-FLZ-SnRK1 regulatory axis that connects carbon starvation signaling to mitophagy. In this Spotlight article, we focus on the function of mitochondrial FLZ proteins and SnRK1, and discuss them in context of current knowledge on the regulation of mitophagy in plants.

Abstract P3199: Role Of Acetylation In Regulating Mitochondrial Dysfunction In The Aged Heart

Cardiac mitochondrial dysfunction is a critical contributor to the pathogenesis of aging. Cardiac muscle is an extremely high energy demanding tissue, necessitating properly functioning mitochondria to meet this demand for contractile function. As such, complete control of mitochondrial function is indispensable to maintain cardiac efficiency. Lysine acetylation is a post-translational modification of proteins that has been shown to regulate several metabolic and biochemical processes in the mitochondria. The goal of this study is to understand the role of mitochondrial lysine acetylation in regulating mitochondrial processes in the aged heart. We observed an increased propensity towards a pro-acetylation profile resulting in increased acetylation of several cardiac mitochondrial proteins involved in metabolism, redox milieu and electron transport chain complexes in aging which was attenuated in our cardiac GCN5L1 knockout old animal. Based upon these findings, we hypothesize that mitochondrial acetyltransferase GCN5L1 has a critical role in regulating the function of mitochondrial proteins in the aged heart. Using immunoprecipitation assay, we observed an age-associated increase in acetylation of several key fatty acid oxidation and glucose oxidation proteins. This increased acetylation correlated with decreased activity of several fatty acid oxidation proteins, including short- and long-chain acyl-CoA dehydrogenase. Several mitochondrial proteins involved in mitochondrial fatty acid import and electron transport chain complexes were hyperacetylated in aging. These proteins largely exhibited increased acetylation levels in response to age that was attenuated by cardiac-specific GCN5L1 knockout. Lastly, we observed an age-associated increase in GCN5L1-mediated acetylation of the antioxidant enzyme manganese superoxide dismutase (SOD2) at lysine site K122. Acetylation of SOD2 at the K122 site has been shown to inhibit SOD2 activity. Based upon our findings, we conclude that age-associated increases in GCN5L1 expression results in derangements in cardiac fuel substrate utilization, electron transport chain complex function, and mediation of reactive oxygen species-associated damage.

Phytochemicals Modify the Action of Cancer Cells Mitochondrial Drug-Resistance Mechanism

The genesis and evolution of cancer are known to be significantly influenced by mitochondria, and recent studies have indicated that mitochondrial modifications may potentially contribute to the emergence of treatment resistance. Additionally, drug-resistant cancer cells may also display modifications in mitochondrial metabolism, such as changes in the generation of reactive oxygen species (ROS), which are biological byproducts of mitochondrial respiration. These changes can alter the cell's sensitivity to chemotherapy drugs and contribute to drug resistance. The expression of specific genes or proteins that are crucial in the control of cell growth and survival may be altered by mitochondrial mutations, which may also contribute to medication resistance. Phytochemicals are naturally occurring, biologically active substances found in plants that have been demonstrated to offer a variety of health advantages, including anti-cancer effects. It has been demonstrated that phytochemicals target these altered mitochondrial pathways in cancer cells, increasing the potency of chemotherapy medications and overcoming drug resistance. For instance, it has been demonstrated that some phytochemicals, including curcumin, resveratrol, and quercetin, can block the function of mitochondrial membrane proteins that lead to drug resistance in cancer cells. Other phytochemicals, including berberine and epigallocatechin gallate (EGCG), have been demonstrated to directly interfere with mitochondrial activity, inducing apoptosis (programmed cell death) in cancer cells. Overall, the capacity of phytochemicals to modify the functioning of cancer cell mitochondrial drug-resistance systems is a viable strategy for the creation of novel anti-cancer treatments.

Next-generation sequencing reveals mitogenome diversity in plasma extracellular vesicles from colorectal cancer patients

BackgroundRecent reports have demonstrated that the entire mitochondrial genome can be secreted in extracellular vesicles (EVs), but the biological attributes of this cell-free mitochondrial DNA (mtDNA) remain insufficiently understood. We used next-generation sequencing to compare plasma EV-derived mtDNA to that of whole blood (WB), peripheral blood mononuclear cells (PBMCs), and formalin-fixed paraffin-embedded (FFPE) tumor tissue from eight rectal cancer patients and WB and fresh-frozen (FF) tumor tissue from eight colon cancer patients.MethodsTotal DNA was isolated before the mtDNA was enriched by PCR with either two primer sets generating two long products or multiple primer sets (for the FFPE tumors), prior to the sequencing. mtDNA diversity was assessed as the total variant number, level of heteroplasmy (mutant mtDNA copies mixed with wild-type copies), variant distribution within the protein-coding genes, and the predicted functional effect of the variants in the different sample types. Differences between groups were compared by paired Student’s t-test or ANOVA with Dunnett’s multiple comparison tests when comparing matched samples from patients. Mann–Whitney U test was used when comparing differences between the cancer types and patient groups. Pearson correlation analysis was performed.ResultsIn both cancer types, EV mtDNA presented twice as many variants and had significantly more low-level heteroplasmy than WB mtDNA. The EV mtDNA variants were clustered in the coding regions, and the proportion of EV mtDNA variants that were missense mutations (i.e., estimated to moderately affect the mitochondrial protein function) was significantly higher than in WB and tumor tissues. Nonsense mutations (i.e., estimated to highly affect the mitochondrial protein function) were only observed in the tumor tissues and EVs.ConclusionTaken together, plasma EV mtDNA in CRC patients exhibits a high degree of diversity.Trial registrationClinicalTrials.gov: NCT01816607. Registered 22 March 2013.

Mitochondrial Damage and Hypertension: Another Dark Side of Sodium Excess.

Essential or primary hypertension (HT) is a worldwide health problem with no definitive cure. Although the exact pathogenesis of HT is not known, genetic factors, increased renin-angiotensin and sympathetic system activity, endothelial dysfunction, oxidative stress, and inflammation play a role in its development. Environmental factors such as sodium intake are also important for BP regulation, and excess sodium intake in the form of salt (NaCl, sodium chloride) increases blood pressure in salt-sensitive people. Excess salt intake increases extracellular volume, oxidative stress, inflammation, and endothelial dysfunction. Recent evidence suggests that increased salt intake also disturbs mitochondrial function both structurally and functionally which is important as mitochondrial dysfunction is associated with HT. In the current review, we have summarized the experimental and clinical data regarding the impact of salt intake on mitochondrial structure and function. Excess salt intake damage mitochondrial structure (e.g., shorter mitochondria with less cristae, increased mitochondrial fission, increased mitochondrial vacuolization). Functionally, high salt intake impairs mitochondrial oxidative phosphorylation and electron transport chain, ATP production, mitochondrial calcium homeostasis, mitochondrial membrane potential, and mitochondrial uncoupling protein function. Excess salt intake also increases mitochondrial oxidative stress and modifies Krebs cycle protein expressions. Studies have shown that high salt intake impairs mitochondrial structure and function. These maladaptive mitochondrial changes facilitate the development of HT especially in salt-sensitive individuals. High salt intake impairs many functional and structural components of mitochondria. These mitochondrial alterations along with increased salt intake promote the development of hypertension.

Effective differentiation of double negative thymocytes requires high fidelity replication of mitochondrial DNA in an age dependent manner.

One of the most proliferative periods for T cells occurs during their development in the thymus. Increased DNA replication can result in increased DNA mutations in the nuclear genome, but also in mitochondrial genomes. A high frequency of mitochondrial DNA mutations can lead to abnormal mitochondrial function and have negative implications on human health. Furthermore, aging is accompanied by an increase in such mutations through oxidative damage and replication errors. Increased mitochondrial DNA mutations cause loss of mitochondrial protein function, and decrease energy production, substrates, and metabolites. Here we have evaluated the effect of increased mitochondrial DNA mutations on T cell development in the thymus. Using mice carrying a mutant mitochondrial DNA polymerase γ (PolG) that causes increased mitochondrial DNA mutations, we show that high fidelity replication of mitochondrial DNA is pivotal for proper T cell development. Reducing the fidelity of mitochondrial DNA replication results in a premature age-dependent reduction in the total number of CD4/CD8 double negative and double positive thymocytes. Analysis of mitochondrial density in thymocyte subpopulations suggests that this may be due to reduced proliferation in specific double negative stages. Taken together, this work suggests that T cell development is regulated by the ability of mitochondria to faithfully replicate their DNA.

EFHD1, a novel mitochondrial regulator of tumor metastasis in clear cell renal cell carcinoma.

The biological function of many mitochondrial proteins in mechanistic detail has not been well investigated in clear cell renal cell carcinoma (ccRCC). A seven-mitochondrial-gene signature was generated by Lasso regression analysis to improve the prediction of prognosis of patients with ccRCC, using The Cancer Genome Atlas and Clinical Proteomic Tumor Analysis Consortium cohort. Among those seven genes, EFHD1 is less studied and its role in the progression of ccRCC remains unknown. The decreased expression of EFHD1 was validated in clinical samples and was correlated with unfavorable outcome. Overexpression of EFHD1 in ccRCC cells resulted in the reduction of mitochondrial Ca2+ , and the inhibition of cell migration and invasion in vitro and tumor metastasis in vivo. Mechanistically, EFHD1 physically bound to the core mitochondrial calcium transporter (mitochondrial calcium uniporter, MCU) through its N-terminal domain. The interaction between EFHD1 and MCU suppressed the uptake of Ca2+ into mitochondria, and deactivated the Hippo/YAP signaling pathway. Further data revealed that the ectopic expression of EFHD1 upregulated STARD13 to enhance the phosphorylation of YAP protein at Ser-127. The knockdown of STARD13 or the overexpression of MCU partly abrogated the EFHD1-mediated induction of phosphorylation of YAP at Ser-127 and suppression of cell migration. Taken together, the newly identified EFHD1-MCU-STARD13 axis participates in the modulation of the Hippo/YAP pathway and serves as a novel regulator in the progression of ccRCC.

A Promising Strategy to Treat Neurodegenerative Diseases by SIRT3 Activation.

SIRT3, the primary mitochondrial deacetylase, regulates the functions of mitochondrial proteins including metabolic enzymes and respiratory chain components. Although SIRT3's functions in peripheral tissues are well established, the significance of its downregulation in neurodegenerative diseases is beginning to emerge. SIRT3 plays a key role in brain energy metabolism and provides substrate flexibility to neurons. It also facilitates metabolic coupling between fuel substrate-producing tissues and fuel-consuming tissues. SIRT3 mediates the health benefits of lifestyle-based modifications such as calorie restriction and exercise. SIRT3 deficiency is associated with metabolic syndrome (MetS), a precondition for diseases including obesity, diabetes, and cardiovascular disease. The pure form of Alzheimer's disease (AD) is rare, and it has been reported to coexist with these diseases in aging populations. SIRT3 downregulation leads to mitochondrial dysfunction, neuroinflammation, and inflammation, potentially triggering factors of AD pathogenesis. Recent studies have also suggested that SIRT3 may act through multiple pathways to reduce plaque formation in the AD brain. In this review, we give an overview of SIRT3's roles in brain physiology and pathology and discuss several activators of SIRT3 that can be considered potential therapeutic agents for the treatment of dementia.

J-Domain Proteins Orchestrate the Multifunctionality of Hsp70s in Mitochondria: Insights from Mechanistic and Evolutionary Analyses.

Mitochondrial J-domain protein (JDP) co-chaperones orchestrate the function of their Hsp70 chaperone partner(s) in critical organellar processes that are essential for cell function. These include folding, refolding, and import of mitochondrial proteins, maintenance of mitochondrial DNA, and biogenesis of iron-sulfur cluster(s) (FeS), prosthetic groups needed for function of mitochondrial and cytosolic proteins. Consistent with the organelle's endosymbiotic origin, mitochondrial Hsp70 and the JDPs' functioning in protein folding and FeS biogenesis clearly descended from bacteria, while the origin of the JDP involved in protein import is less evident. Regardless of their origin, all mitochondrial JDP/Hsp70 systems evolved unique features that allowed them to perform mitochondria-specific functions. Their modes of functional diversification and specialization illustrate the versatility of JDP/Hsp70 systems and inform our understanding of system functioning in other cellular compartments.

Targeting Mitochondrial Dynamics Proteins for the Development of Therapies for Cardiovascular Diseases

Cardiovascular diseases are one of the leading causes of death worldwide. The identification of new pathogenetic targets contributes to more efficient development of new types of drugs for the treatment of cardiovascular diseases. This review highlights the problem of mitochondrial dynamics disorders, in the context of cardiovascular diseases. A change in the normal function of mitochondrial dynamics proteins is one of the reasons for the development of the pathological state of cardiomyocytes. Based on this, therapeutic targeting of these proteins may be a promising strategy in the development of cardiac drugs. Here we will consider changes for each process of mitochondrial dynamics in cardiovascular diseases: fission and fusion of mitochondria, mitophagy, mitochondrial transport and biogenesis, and also analyze the prospects of the considered protein targets based on existing drug developments.

Understanding the Role of Yeast Yme1 in Mitochondrial Function Using Biochemical and Proteomics Analyses.

Mitochondrial i-AAA proteinase Yme1 is a multifunctional protein that plays important roles in maintaining mitochondrial protein homeostasis and regulating biogenesis and function of mitochondrial proteins. However, due to the complex interplay of mitochondria and the multifunctional nature of Yme1, how Yme1 affects mitochondrial function and protein homeostasis is still poorly understood. In this study, we investigated how YME1 deletion affects yeast Saccharomyces cerevisiae growth, chronological life span, mitochondrial protein homeostasis and function, with a focus on the mitochondrial oxidative phosphorylation (OXPHOS) complexes. Our results show that whilst the YME1 deleted cells grow poorly under respiratory conditions, they grow similar to wild-type yeast under fermentative conditions. However, the chronological life span is impaired, indicating that Yme1 plays a key role in longevity. Using highly enriched mitochondrial extract and proteomic analysis, we show that the abundances of many mitochondrial proteins are altered by YME1 deletion. Several components of the respiratory chain complexes II, III, IV and V were significantly decreased, suggesting that Yme1 plays an important role in maintaining the level and function of complexes II-V. This result was confirmed using blue native-PAGE and in-solution-based enzyme activity assays. Taken together, this study shows that Yme1 plays an important role in the chronological life span and mitochondrial protein homeostasis and has deciphered its function in maintaining the activity of mitochondrial OXPHOS complexes.

Carnosol Reduced Pathogenic Protein Aggregation and Cognitive Impairment in Neurodegenerative Diseases Models via Improving Proteostasis and Ameliorating Mitochondrial Disorders.

Neurodegenerative diseases (NDs) such as Alzheimer's disease, Parkinson's disease, and Huntington's disease are incurable diseases with progressive loss of neural function and require urgent development of effective treatments. Carnosol (CL) reportedly has a pharmacological effect in the prevention of dementia. Nevertheless, the mechanisms of CL's neuroprotection are not entirely clear. The present study aimed to investigate the effects and mechanisms of CL-mediated neuroprotection through Caenorhabditis elegans models. First, CL restored ND protein homeostasis via inhibiting the IIS pathway, regulating MAPK signaling, and simultaneously activating molecular chaperone, thus inhibiting amyloid peptide (Aβ), polyglutamine (polyQ), and α-synuclein (α-syn) deposition and reducing protein disruption-mediated behavioral and cognitive impairments as well as neuronal damages. Furthermore, CL could repair mitochondrial structural damage via improving the mitochondrial membrane protein function and mitochondrial structural homeostasis and improve mitochondrial functional defects via increasing adenosine triphosphate contents, mitochondrial membrane potential, and reactive oxygen species levels, suggesting that CL could improve the ubiquitous mitochondrial defects in NDs. More importantly, we found that CL activated mitochondrial kinetic homeostasis related genes to improve the mitochondrial homeostasis and dysfunction in NDs. Meanwhile, CL up-regulated unc-17, cho-1, and cha-1 genes to alleviate Aβ-mediated cholinergic neurological disorders and activated Notch signaling and the Wnt pathway to diminish polyQ- and α-syn-induced ASH neurons as well as dopaminergic neuron damages. Overall, our study clarified the beneficial anti-ND neuroprotective effects of CL in different aspects and provided new insights into developing CL into products with preventive and therapeutic effects on NDs.