A FRET biosensor constructed using pH sensitive G-quadruplex DNA for detecting mitochondrial autophagy.

Mitochondria are crucial powerhouses and central organelles for maintaining normal physiological activities in eukaryotic cells. The use of highly specific optical biosensors to monitor mitochondrial autophagy (mitophagy) is an important way for detecting mitochondrial abnormalities. Herein, we report a pH responsive G-quadruplex (G4) structure folded by the oligonucleotide named P24. P24 is composed of four GGCCTG repeating units, and the high guanine content allows it to form an antiparallel G4 topology at pH 4.5 (lysosomal pH). However, when pH increases to around 7.4 (mitochondrial pH), P24 further transforms into a double-stranded structure. Unlike most oligonucleotides that enter lysosomes, P24 highly targets mitochondria in live cells. These characteristics enable P24 to construct a pH responsive optical biosensor by linking a pair of fluorescence resonance energy transfer (FRET) fluorophores. The P24 based biosensor demonstrates reliable applications in detecting mitophagy in live cells.

Mitochondrial 'Birth-Death' coordinator: An intelligent hydrogen nanogenerator to enhance intervertebral disc regeneration.

Currently, mitochondrial dysfunction caused by oxidative stress is a growing concern in degenerative diseases, notably intervertebral disc degeneration (IVDD). Dysregulation of the balance of mitochondrial quality control (MQC) has been considered the key contributor, while it's still challenging to effectively harmonize different MQC components in a simple and biologically safe way. Hydrogen gas (H2) is a promising mitochondrial therapeutic molecule due to its bio-reductivity and diffusibility across cellular membranes, yet its relationship with MQC regulation remains unknown. Herein, we propose a mitochondrial 'Birth-Death' coordinator achieved by an intelligent hydrogen nanogenerator (Fe@HP-OD), which can sustainably release H2 in response to the unique microenvironment in degenerated IVDs. Both in vitro and in vivo results prove alleviation of cellular oxidative stress and restoration of nucleus pulposus cells function, thereby facilitating successful IVD regeneration. Significantly, this study for the first time proposes the mitochondrial 'Birth-Death' coordination mechanism: 1) attenuation of overactivated mitochondrial 'Death' process (UPRmt and unselective mitophagy); and 2) activation of Adenosine 5'-monophosphate-activated protein kinase (AMPK) signaling pathway for mitochondrial 'Birth-Death' balance (mitochondrial biogenesis and controlled mitophagy). These pioneering findings can fill in the gaps in molecular mechanisms for H2 regulation on MQC homeostasis, and pave the way for future strategies towards restoring equilibrium of MQC system against degenerative diseases.

Naoxintong capsule accelerates mitophagy in cerebral ischemia-reperfusion injury via TP53/PINK1/PRKN pathway based on network pharmacology analysis and experimental validation.

ETHNOPHARMACOLOGICAL RELEVANCE: The incidence and mortality of cerebrovascular diseases are increasing year by year. Cerebral ischemia-reperfusion injury (CIRI) is common in patients with ischemic stroke. Naoxintong (NXT) is composed of a variety of Chinese medicines and has the ability to treat CIRI. AIM OF THE STUDY: The aim of this study is to investigate whether NXT regulates mitophagy in CIRI based on network pharmacology analysis and experimental validation. MATERIALS AND METHODS: Oxygen and glucose deprivation/re-oxygenation (OGD/R, 2/22 h) model of PC12 cells and transient middle cerebral artery occlusion (tMCAO, 2/22 h) model of rats were established. Pharmacodynamic indicators include neurological deficit score, 2,3,5-triphenyte-trazoliumchloride (TTC) staining, hematoxylin-eosin (HE) staining and cell viability. Network pharmacology was used to predict pharmacological mechanisms. Pharmacological mechanism indexes include transmission electron microscopy (TEM), drug affinity responsive target stability (DARTS), cellular thermal shift assay (CETSA), immunohistochemistry (IHC), western blot (WB) and immunofluorescence (IF). Kevetrin (an agonists of p53) and pifithrin-α (an inhibitor of p53) used to detect the key role of p53 in mitophagy of NXT. RESULTS: NXT (1% serum containing NXT and 110 mg/kg) improved the damage of OGD/R PC12 cells and tMCAO rats, and this protective effect was related to the anti-oxidation and ability to promote mitophagy of NXT. NXT and pifithrin-α increased the expression of promoting-mitophagy targets (PINK1, PRKN and LC3B) and inhibited the expression of inhibiting-mitophagy targets (p52) via restraining p53, and finally accelerated mitophagy caused by CIRI. CONCLUSION: This study demonstrates that NXT promotes mitophagy in CIRI through restraining p53 and promoting PINK1/PRKN in vivo and in vitro.

[Regulation of mitophagy and mitochondrial biogenesis by monocarbonyl analogues of curcumin in the cerebral cortex of rats in experimental Alzheimer's disease]. / Regulyatsiya mitofagii i mitokhondrial'nogo biogeneza monokarbonil'nymi analogami kurkumina v kore bol'shikh polusharii golovnogo mozga krys v usloviyakh eksperimental'noi bolezni Al'tsgeimera.

OBJECTIVE: To evaluate the effect of monocarbonyl analogues of curcumin on changes in the processes of mitophagy and mitochondrial biogenesis in the cerebral cortex of rats with experimental Alzheimer's disease. MATERIAL AND METHODS: Alzheimer's disease was modeled in Wistar rats of both sexes by injection of ß-amyloid fragments into the hippocampus of the animal. Compounds (1E, 4E)-1.5-bis (3.4.5-trimethoxyphenyl) penta-1.4-diene-3-one (AZBAX4 code) and (1E, 4E)-1.5-bis (2.4.6-trimethoxyphenyl) penta-1.4-diene-3-one (AZBAX6 code) at a dose of 20 mg/ kg (orally) and the reference drug donepezil at a dose of 50 mg/kg (orally) were administered for 30 days, after which changes in the activity of succinate dehydrogenase, cytochrome-c oxidase and citrate synthase as enzymatic biomarkers of mitochondrial biogenesis and mitophagy, respectively, were evaluated in the mitochondrial fraction of the cerebral cortex. RESULTS: The administration of AZBAX4 and AZBAX6 compounds led to an increase in the activity of succinate dehydrogenase; cytochrome-c oxidase, as well as citrate synthase in relation to the same indicators of the group of untreated animals. The use of the analyzed compounds was equally effective in both female and male rats. At the same time, it should be noted that the analyzed compounds significantly exceeded the activity level of the reference donepezil. CONCLUSION: AZBAX4 and AZBAX6 contribute to an increase in the intensity of mitochondrial biogenesis and mitophagy reactions in the cerebral cortex of rats with Alzheimer's disease, which makes them potentially effective neuroprotective compounds.

Exploring the Mechanism of Ferroptosis Induction by Sappanone A in Cancer: Insights into the Mitochondrial Dysfunction Mediated by NRF2/xCT/GPX4 Axis.

Non-small cell lung cancer (NSCLC), a major subtype of lung cancer, encompasses squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. Compared to small cell lung cancer, NSCLC cells grow and divide more slowly, and their metastasis occurs at a later stage. Currently, chemotherapy is the primary treatment for this disease. Sappanone A (SA) is a flavonoid compound extracted from the plant Caesalpinia sappan, known for its antitumor, redox-regulating, and anti-inflammatory properties. Recent studies have investigated the interaction of SA with mitochondrial pathways in regulating cell death through the Nrf-2/GPX-4/xCT axis. This study specifically explores the mechanism by which SA affects mitochondrial morphology and structure through the regulation of mitophagy and mitochondrial biogenesis in tumor cells. The study primarily utilizes second-generation transcriptomic sequencing data and molecular docking techniques to elucidate the role of SA in regulating programmed cell death in tumor cells. The omics results indicate that SA treatment significantly targets genes involved in oxidative phosphorylation, mitophagy, mitochondrial dynamics, and oxidative stress. Further findings confirmed that the Nrf-2/GPX4/xCT pathway serves as a crucial target of SA in the treatment of NSCLC. Knockdown of Nrf-2 (si-Nrf-2) and Nrf-2 overexpression (ad-Nrf-2) were shown to modulate the therapeutic efficacy of SA to varying degrees. Additionally, modifications to the GPX4/xCT genes significantly affected the regulatory effects of SA on mitochondrial autophagy, biogenesis, and energy metabolism. These regulatory mechanisms may be mediated through the caspase pathway and ferroptosis-related signaling. Molecular biology experiments have demonstrated that SA intervention further inhibits the phosphorylation of FUNDC1 at Tyr18 and downregulates TOM20 expression. SA treatment was found to reduce the expression of PGC1α, Nrf-1, and Tfam, resulting in a decrease in mitochondrial respiration and energy metabolism. Overexpression of Nrf-2 was shown to counteract the regulatory effects of SA on mitophagy and mitochondrial biogenesis. Confocal microscopy experiments further revealed that SA treatment increases mitochondrial fragmentation, subsequently inducing mitochondrial pathway-mediated programmed cell death. However, genetic modification of the Nrf-2/GPX4/xCT pathway significantly altered the regulatory effects of SA on tumor cells. In conclusion, SA has been identified as a promising therapeutic agent for NSCLC. The mitochondrial pathway-mediated apoptosis and ferroptosis may represent key mechanisms in regulating tumor cell death. Targeting the Nrf-2/GPX-4/xCT axis offers a novel therapeutic approach for maintaining mitochondrial homeostasis within the cellular microenvironment.

Graphene Oxide Quantum Dots-Preactivated Dental Pulp Stem Cells/GelMA Facilitates Mitophagy-Regulated Bone Regeneration.

Background: In bone tissue engineering (BTE), cell-laden scaffolds offer a promising strategy for repairing bone defects, particularly when host cell regeneration is insufficient due to age or disease. Exogenous stem cell-based BTE requires bioactive factors to activate these cells. Graphene oxide quantum dots (GOQDs), zero-dimensional derivatives of graphene oxide, have emerged as potential osteogenic nanomedicines. However, constructing biological scaffolds with GOQDs and elucidating their biological mechanisms remain critical challenges. Methods: We utilized GOQDs with a particle size of 10 nm, characterized by a surface rich in C-O-H and C-O-C functional groups. We developed a gelatin methacryloyl (GelMA) hydrogel incorporated with GOQDs-treated dental pulp stem cells (DPSCs). These constructs were transplanted into rat calvarial bone defects to estimate the effectiveness of GOQDs-induced DPSCs in repairing bone defects while also investigating the molecular mechanism underlying GOQDs-induced osteogenesis in DPSCs. Results: GOQDs at 5 µg/mL significantly enhanced the osteogenic differentiation of DPSCs without toxicity. The GOQDs-induced DPSCs showed active osteogenic potential in three-dimensional cell culture system. In vivo, transplantation of GOQDs-preactivated DPSCs/GelMA composite effectively facilitated calvarial bone regeneration. Mechanistically, GOQDs stimulated mitophagy flux through the phosphatase-and-tensin homolog-induced putative kinase 1 (PINK1)/Parkin E3 ubiquitin ligase (PRKN) pathway. Notably, inhibiting mitophagy with cyclosporin A prevented the osteogenic activity of GOQDs. Conclusion: This research presents a well-designed bionic GOQDs/DPSCs/GelMA composite scaffold and demonstrated its ability to promote bone regeneration by enhancing mitophagy. These findings highlight the significant potential of this composite for application in BTE and underscore the crucial role of mitophagy in promoting the osteogenic differentiation of GOQDs-induced stem cells.

Glutamine metabolism modulates microglial NLRP3 inflammasome activity through mitophagy in Alzheimer's disease.

The NLR family pyrin domain containing 3 (NLRP3) inflammasome in microglia is intimately linked to the pathogenesis of Alzheimer's disease (AD). Although NLRP3 inflammasome activity is regulated by cellular metabolism, the underlying mechanism remains elusive. Here, we found that under the pathological conditions of AD, the activation of NLRP3 inflammasome in microglia is accompanied by increased glutamine metabolism. Suppression of glutaminase, the rate limiting enzyme in glutamine metabolism, attenuated the NLRP3 inflammasome activation both in the microglia of AD mice and cultured inflammatory microglia. Mechanistically, inhibiting glutaminase blocked the anaplerotic flux of glutamine to the tricarboxylic acid cycle and amino acid synthesis, down-regulated mTORC1 signaling by phosphorylating AMPK, which stimulated mitophagy and limited the accumulation of intracellular reactive oxygen species, ultimately prevented the activation of NLRP3 inflammasomes in activated microglia during AD. Taken together, our findings suggest that glutamine metabolism regulates the activation of NLRP3 inflammasome through mitophagy in microglia, thus providing a potential therapeutic target for AD treatment.

Mitophagy related diagnostic biomarkers for coronary in-stent restenosis identified using machine learning and bioinformatics.

Percutaneous coronary intervention (PCI) combined with stent implantation is currently one of the most effective treatments for coronary artery disease (CAD). However, in-stent restenosis (ISR) significantly compromises its long-term efficacy. Mitophagy plays a crucial role in vascular homeostasis, yet its role in ISR remains unclear. This study aims to identify mitophagy-related biomarkers for ISR and explore their underlying molecular mechanisms. Through differential gene expression analysis between ISR and Control samples in the combined dataset, 169 differentially expressed genes (DEGs) were identified. Twenty-three differentially expressed mitophagy-related genes (DEMRGs) were identified by intersecting with mitophagy-related genes (MRGs) from the GeneCards, and functional enrichment analysis indicated their significant involvement in mitophagy-related biological processes. Using Weighted Gene Co-expression Network Analysis (WGCNA) and three machine learning algorithms (Logistic-LASSO, RF, and SVM-RFE), LRRK2, and ANKRD13A were identified as mitophagy-related biomarkers for ISR. The nomogram based on these two genes also exhibited promising diagnostic performance for ISR. Gene Set Enrichment Analysis (GSEA) as well as immune infiltration analyses showed that these two genes were closely associated with immune and inflammatory responses in ISR. Furthermore, potential small molecule compounds with therapeutic implications for ISR were predicted using the connectivity Map (cMAP) database. This study systematically investigated mitophagy-related biomarkers for ISR and their potential biological functions, providing new insights into early diagnosis and precision treatment strategies for ISR.

Mitophagy-associated programmed neuronal death and neuroinflammation.

Mitochondria are crucial organelles that play a central role in cellular metabolism and programmed cell death in eukaryotic cells. Mitochondrial autophagy (mitophagy) is a selective process where damaged mitochondria are encapsulated and degraded through autophagic mechanisms, ensuring the maintenance of both mitochondrial and cellular homeostasis. Excessive programmed cell death in neurons can result in functional impairments following cerebral ischemia and trauma, as well as in chronic neurodegenerative diseases, leading to irreversible declines in motor and cognitive functions. Neuroinflammation, an inflammatory response of the central nervous system to factors disrupting homeostasis, is a common feature across various neurological events, including ischemic, infectious, traumatic, and neurodegenerative conditions. Emerging research suggests that regulating autophagy may offer a promising therapeutic avenue for treating certain neurological diseases. Furthermore, existing literature indicates that various small molecule autophagy regulators have been tested in animal models and are linked to neurological disease outcomes. This review explores the role of mitophagy in programmed neuronal death and its connection to neuroinflammation.

Resveratrol Mitigates Uremic Toxin-Induced Intestinal Barrier Dysfunction in Chronic Kidney Disease by Promoting Mitophagy and Inhibiting Apoptosis Pathways.

Background: Chronic Kidney Disease (CKD) is a systemic progressive disorder related to uremic toxins. Uremic toxins disturb intestinal epithelial destruction and barrier dysfunction leading to gut-renal axis disorders in CKD. We examine the protective role of Resveratrol (RSV) against uremic toxin indoxyl sulphate (IS) related intestinal barrier disturbances among CKD. METHODS: 5/6 nephrectomized mice and isolated primary mouse intestinal epithelial cells (IEC-6) are used to assess the influence of IS on intestinal epithelial tight junction barriers. Serum biochemistry parameters, hematoxylin & eosin (H&E) and immunohistochemistry staining (IHC), Western blot analysis, q-PCR, and si-RNA targeted against AhR were used in this study. RESULTS: IS decreases the expression of tight junction proteins (TJPs) ZO-1 and claudins, increases the apoptosis and impairs mitophagy within IECs. Treatment with RSV not only reduces the loss of TJPs but also modulates mitophagy markers LC3 and P62, and concurrently decreases the levels of apoptosis-related proteins. Significantly, RSV ameliorates intestinal barrier dysfunction in CKD by modulating mitophagy via the IRF1-DRP1 axis, restoring autophagy, and inhibiting apoptosis through the activation of the PI3K/Akt-Ho-1 anti-oxidant pathway, and mTOR regulated pathways. CONCLUSION: This study establishes RSV as a potential therapeutic agent that can ameliorate gut-renal axis disturbances in CKD. These findings provide valuable insights into mechanisms underlying RSV RSV-mediated gut-renal axis, highlighting its effectiveness as a potential treatment option for CKD-associated intestinal barrier dysfunction.

Mitochondrial Stress as a Central Player in the Pathogenesis of Hypoxia-Related Myocardial Dysfunction: New Insights.

Hypoxic injury is a critical pathological factor in the development of various cardiovascular diseases, such as congenital heart disease, myocardial infarction, and heart failure. Mitochondrial quality control is essential for protecting cardiomyocytes from hypoxic damage. Under hypoxic conditions, disruptions in mitochondrial homeostasis result in excessive reactive oxygen species (ROS) production, imbalances in mitochondrial dynamics, and initiate pathological processes including oxidative stress, inflammatory responses, and apoptosis. Targeted interventions to enhance mitochondrial quality control, such as coenzyme Q10 and statins, have shown promise in mitigating hypoxia-induced mitochondrial dysfunction. These treatments offer potential therapeutic strategies for hypoxia-related cardiovascular diseases by regulating mitochondrial fission and fusion, restoring mitochondrial biogenesis, reducing ROS production, and promoting mitophagy.

GLS2 reduces the occurrence of epilepsy by affecting mitophagy function in mouse hippocampal neurons.

BACKGROUND: Altered mitophagy has been observed in various neurological disorders, such as epilepsy. The role of mitophagy in causing neuronal damage during epileptic episodes is significant, and recent research has indicated that GLS2 plays a crucial role in regulating autophagy. However, exactly how GLS2 affects epilepsy is still unclear. AIMS: To investigate the expression and distribution characteristics of GLS2 in epilepsy, and then observed the changes in behavior and electrophysiology caused by overexpression of GLS2 in epileptic mice, and determined whether GLS2 regulated seizure-like changes in the mouse model through the protective mechanism of mitophagy. RESULTS: The expression of GLS2 in a kainic acid (KA)-induced epileptic mouse model and aglutamate-inducedneuronal excitatory damage in HT22 cells model was downregulation. In brief, overexpression of GLS2 can alleviate epileptic activity. Subsequently, we demonstrated that GLS2 interacts with mitophagy-related proteins in a KA-induced epilepsy mouse model. Mechanistically, overexpression of GLS2 inhibited mitophagy in epileptic mice, downregulating the expression of LC3 and reducing ROS production. CONCLUSIONS: This study proves the GLS2 expression pattern is abnormal in epileptic mice. The function of mitophagy in hippocampal neurons is affected by GLS2, and overexpression of GLS2 can reduce the occurrence of seizure-like events (SLEs) by altering mitophagy function. Thus, GLS2 might control seizures, and our findings provide a fresh avenue for antiepileptic treatment and offer novel insights into treating and preventing epilepsy.

The role of PINK1-Parkin in mitochondrial quality control.

Mitophagy mediated by the recessive Parkinson's disease genes PINK1 and Parkin responds to mitochondrial damage to preserve mitochondrial function. In the pathway, PINK1 is the damage sensor, probing the integrity of the mitochondrial import pathway, and activating Parkin when import is blocked. Parkin is the effector, selectively marking damaged mitochondria with ubiquitin for mitophagy and other quality-control processes. This selective mitochondrial quality-control pathway may be especially critical for dopamine neurons affected in Parkinson's disease, in which the mitochondrial network is widely distributed throughout a highly branched axonal arbor. Here we review the current understanding of the role of PINK1-Parkin in the quality control of mitophagy, including sensing of mitochondrial distress by PINK1, activation of Parkin by PINK1 to induce mitophagy, and the physiological relevance of the PINK1-Parkin pathway.

Coronavirus M protein promotes mitophagy over virophagy by recruiting PDPK1 to phosphorylate SQSTM1 at T138.

Autophagy plays a dual role in coronavirus infection, facilitating the elimination of either proviral components (virophagy) or antiviral factors such as mitochondria (mitophagy), leading to complex mechanisms of immune evasion. Understanding the mechanisms that govern the switch between the autophagic degradation of deleterious or beneficial substrates in coronavirus infection is crucial for developing precise drug targets to treat virus-induced diseases. However, this switch remains largely unknown. Using a dual split-fluorescence assay, we identify PDPK1 as a negative regulator of innate immunity, directing the transition from virophagy to mitophagy through the phosphorylation of SQSTM1 at T138. Remarkably, a PDPK1-targeting peptide inhibits the replication of various RNA viruses by restoring innate immunity through enhanced virophagy and suppressed mitophagy, thereby protecting female mice from lethal infections. These findings underscore the detrimental role of PDPK1 in innate immunity by orchestrating the shift from virophagy to mitophagy, positioning PDPK1 as a promising pharmacological target for effectively combating a broad spectrum of virus infections.

RABIF promotes hepatocellular carcinoma progression through regulation of mitophagy and glycolysis.

The RAB interacting factor (RABIF) is a putative guanine nucleotide exchange factor that also functions as a RAB-stabilizing holdase chaperone. It has been implicated in pathogenesis of several cancers. However, the functional role and molecular mechanism of RABIF in hepatocellular carcinoma (HCC) are not entirely known. Here, we demonstrate an upregulation of RABIF in patients with HCC, correlating with a poor prognosis. RABIF inhibition results in decreased HCC cell growth both in vitro and in vivo. Our study reveals that depleting RABIF attenuates the STOML2-PARL-PGAM5 axis-mediated mitophagy. Consequently, this reduction in mitophagy results in diminished mitochondrial reactive oxygen species (mitoROS) production, thereby alleviating the HIF1α-mediated downregulation of glycolytic genes HK1, HKDC1, and LDHB. Additionally, we illustrate that RABIF regulates glucose uptake by controlling RAB10 expression. Importantly, the knockout of RABIF or blockade of mitophagy sensitizes HCC cells to sorafenib. This study uncovers a previously unrecognized role of RABIF crucial for HCC growth and identifies it as a potential therapeutic target.

The broad-spectrum deubiquitinating enzyme inhibitor PR-619 protects retinal ganglion cell and augments parkin-mediated mitophagy in experimental glaucoma.

Glaucoma is a leading cause of irreversible visual impairment worldwide, characterized by the progressive death of retinal ganglion cells (RGCs). Deubiquitinating enzyme (DUB) inhibitors have shown promise as pharmacological interventions for neurodegenerative disorders. Our study focuses on the pan-DUB inhibitor PR-619 and its potential neuroprotective effects on RGCs through modulation of parkin-mediated mitophagy in experimental glaucoma models. The results show that impaired mitophagy exists in RGCs of our experimental glaucomatous model. In vivo, PR-619 increased RGCs survival in glaucomatous rats. In vitro, it protected RGCs against excitotoxicity and reduced ubiquitin-specific protease (USP) 15 expression. Additionally, PR-619 upregulated parkin expression, increased LC3-II/LC3-I ratios, and elevated LAMP1 levels, indicating enhanced mitophagy in vivo and in vitro. Moreover, numbers of mitophagosomes were increased in optic nerves of PR-619-treated ocular hypertensive rats in vivo. Furthermore, parkin knockdown negated the salutary effects of PR-619 and attenuated expression of parkin-dependent mitophagy effectors in RGCs subjected to glutamate excitotoxicity in vitro. Collectively, these findings implicate augmented parkin-mediated mitophagy as the mechanistic substrate underscoring the neuroprotective capacity of PR-619 in experimental glaucoma. These revelations engender the prospect that pharmacological agents or biotherapeutics augmenting parkin-mediated mitophagy may proffer viable therapeutic modalities for glaucomatous neurodegeneration characterized by impaired mitophagy.

Calorie restriction increases insulin sensitivity to promote beta cell homeostasis and longevity in mice.

Caloric restriction (CR) can extend the organism life- and health-span by improving glucose homeostasis. How CR affects the structure-function of pancreatic beta cells remains unknown. We used single nucleus transcriptomics to show that CR increases the expression of genes for beta cell identity, protein processing, and organelle homeostasis. Gene regulatory network analysis reveal that CR activates transcription factors important for beta cell identity and homeostasis, while imaging metabolomics demonstrates that beta cells upon CR are more energetically competent. In fact, high-resolution microscopy show that CR reduces beta cell mitophagy to increase mitochondria mass and the potential for ATP generation. However, CR beta cells have impaired adaptive proliferation in response to high fat diet feeding. Finally, we show that long-term CR delays the onset of beta cell aging hallmarks and promotes cell longevity by reducing beta cell turnover. Therefore, CR could be a feasible approach to preserve compromised beta cell structure-function during aging and diabetes.

Polysiloxane-Based Fluorescent Probes for Visualizing pH and Thiocyanate during Mitochondrial Autophagy.

Mitochondrial autophagy, known as mitophagy, is a vital cellular process that involves the selective degradation of damaged or dysfunctional mitochondria through autophagy, which is critical to the functional integrity of the entire mitochondrial network and determines the survival and death of cells. An abnormal pH may lead to an imbalance in mitochondrial homeostasis and the occurrence of mitochondrial autophagic acidification and dysfunction. SCN- is also an important anion in cellular metabolism, and its abnormal concentration may lead to mitochondrial damage. However, so far, there are few reports on the simultaneous realization of pH and SCN- detection in mitochondria. Therefore, to complement the blank in this area, we developed the polysiloxane-based fluorescent probe P0-CMN that is capable of simultaneously visualizing pH and SCN- fluctuation levels in mitochondria. The probe P0-CMN has the desired mitochondrial-targeting properties and sensitivity to pH and SCN-. It is able to simultaneously monitor pH and SCN- changes in mitochondria in a dual-channel mode. In addition, probe P0-CMN can visualize pH changes during mitochondrial autophagy. This work provides an effective strategy for the design of dual-responsive fluorescent probes and further broadens the application of polysiloxane fluorescent materials.

Siah3 acts as a physiological mitophagy suppressor that facilitates axonal degeneration.

Mitophagy eliminates dysfunctional mitochondria, and defects in this cellular housekeeping mechanism are implicated in various age-related diseases. Here, we found that mitophagy suppression by the protein Siah3 promoted developmental axonal remodeling in mice. Siah3-deficient mice displayed increased peripheral sensory innervation. Cultured Siah3-deficient sensory neurons exhibited delays in both axonal degeneration and caspase-3 activation in response to withdrawal of nerve growth factor. Mechanistically, Siah3 was transcriptionally induced by the loss of trophic support and formed a complex with the cytosolic E3 ubiquitin ligase parkin, a core component of mitophagy, in transfected cells. Axons of Siah3-deficient neurons mounted profound mitophagy upon initiation of degeneration but not under basal conditions. Neurons lacking both Siah3 and parkin did not exhibit the delay in trophic deprivation-induced axonal degeneration or the induction of axonal mitophagy that was seen in Siah3-deficient neurons. Our findings reveal that mitophagy regulation acts as a gatekeeper of a physiological axon elimination program.

A Siah3 of relief: A role for mitophagy as a fail-safe during developmental axon pruning.

Developmental axon pruning is controlled by a careful balance of pro- and anti-apoptotic signals, which are activated in response to external cues to sculpt mature neuronal circuitry. In this issue of Science Signaling, Abraham et al. define a safeguard against apoptotic axon pruning and illustrate that Siah3 represses Parkin-mediated mitophagy to control the availability of axonal mitochondria that activate the pruning process.