MCOLN1 is a ROS sensor in lysosomes that regulates autophagy

Organelle-oriented nanomedicines in tumor therapy: Targeting, escaping, or collaborating?

Precise tumor therapy is essential for improving treatment specificity, enhancing efficacy, and minimizing side effects. Targeting organelles is a key strategy for achieving this goal and is a frontier research area attracting a considerable amount of attention. The concept of organelle targeting has a significant effect on the structural design of the nanodrugs employed. Most notably, the intricate interactions among different organelles in a tumor cell essentially create a unified system. Unfortunately, this aspect might have been somewhat overlooked when existing organelle-targeting nanodrugs were designed. In this review, we underscore the synergistic relationship among the various organelles and advocate for a holistic view of organelle-targeting design. Through the integration of biology and material science, recent advancements in organelle targeting, escaping, and collaborating are consolidated to offer fresh perspectives for the development of antitumor nanomedicines.

Key Mechanisms in Lysosome Stability, Degradation and Repair

Lysosomes are organelles that play pivotal roles in macromolecule digestion, signal transduction, autophagy, and cellular homeostasis. Lysosome instability, including the inhibition of lysosomal intracellular activity and the leakage of their contents, is associated with various pathologies, including cancer, neurodegenerative diseases, inflammatory diseases and infections. These lysosomal-related pathologies highlight the significance of factors contributing to lysosomal dysfunction. The vulnerability of the lysosomal membrane and its components to internal and external stimuli make lysosomes particularly susceptible to damage. Cells are equipped with mechanisms to repair or degrade damaged lysosomes to prevent cell death. Understanding the factors influencing lysosome stabilization and damage repair is essential for developing effective therapeutic interventions for diseases. This review explores the factors affecting lysosome acidification, membrane integrity, and functional homeostasis and examines the underlying mechanisms of lysosomal damage repair. In addition, we summarize how various risk factors impact lysosomal activity and cell fate.

Research Advances of the Autophagy-Regulated Radiosensitivity

Autophagy is an evolutionarily conserved process of cell self-catabolism that provides a minimum level of energy for cellular homeostasis during metabolic stress. In radiotherapy (RT), it has been explicitly explained that autophagy plays a dual role in tumour control by tuning cellular radiosensitivity. However, the underlying molecular mechanism remains a conundrum. Therefore, it is of utmost importance to gain insight into the molecular mechanisms elaborating the autophagy-mediated radiosensitivity and craft refined RT strategies for different tumours. Distinguishing it from previous reviews in the field, here we discuss the mechanisms of autophagy, especially its pro-survival and growth-suppressing mechanisms via regulation of radiosensitivity. We further outline some frontier RT adjuvant therapies targeting autophagy, in an endeavour to shed some light on the autophagy-mediated pathways to harness radiosensitivity.

ZLDI-8 facilitates pexophagy by ROS-mediated activation of TFEB and ATM in HeLa cells

Autophagy-mediated organelle quality control is vital for cellular homeostasis. However, the mechanisms underlying selective autophagy of peroxisomes, known as pexophagy, are less well understood than those of other organelles, such as mitochondria. In this study, we screened a phosphatase inhibitor library using a cell-based system and identified several potent pexophagy inducers, including ZLDI-8, a known inhibitor of lymphoid-specific tyrosine phosphatase. Notably, treatment with ZLDI-8 selectively induces the loss of peroxisomes without affecting other organelles, such as mitochondria, the endoplasmic reticulum, or the Golgi apparatus. The peroxisome loss induced by ZLDI-8 was significantly blocked in ATG5-knockout HeLa cells, confirming its dependence on autophagy. We further found that ZLDI-8 treatment increases both cellular and peroxisomal reactive oxygen species (ROS), which were effectively scavenged by N-acetylcysteine (NAC). The increase in peroxisomal ROS leads to the activation of ATM kinase and the dephosphorylation of TFEB. Moreover, ROS scavenging prevents all of these processes. Taken together, these findings demonstrate that ZLDI-8 induces pexophagy through a mechanism involving peroxisomal ROS-mediated activation of TFEB and ATM. This study provides valuable insights into the molecular mechanisms regulating selective peroxisome degradation and potential therapeutic strategies for targeting pexophagy.

Mechanistic insights into arimoclomol mediated effects on lysosomal function in Niemann-pick type C disease

Niemann-Pick disease type C (NPC) is an ultra-rare, fatal neurodegenerative disease. It is characterized by lysosomal dysfunction with cytotoxic accumulation of unesterified cholesterol and glycosphingolipids in lysosomes, which causes neurodegeneration and peripheral organ dysfunction. Arimoclomol, an orally available small molecule, is the first FDA-approved treatment for NPC when used in combination with miglustat. Here, we present the results of a series of in vitro studies performed to explore the pathways by which arimoclomol targets the fundamentals of NPC etiology. While the precise cellular interactions of arimoclomol remain unclear, the increased translocation of the transcription factors EB and E3 (TFEB and TFE3) from the cytosol to the nucleus is a key initial step for triggering a cascade of downstream events that can rescue cellular functions. Activation of TFEB and TFE3 raises the expression rates of coordinated lysosomal expression and regulation (CLEAR) genes including NPC1 that are essential for the regulation of lysosomal function. The subsequent upregulation of CLEAR network proteins combined with increased unfolded protein response activation was shown to enlarge the pool of matured NPC1 capable of reaching the lysosome to reduce cholesterol accumulation. By also amplifying expression of CLEAR genes associated with autophagy, arimoclomol has the potential to act on different pathways and improve cell viability independent of NPC1 protein levels and functionality. In summary, the findings presented illustrate how arimoclomol improves lysosomal function and potentially autophagy flux to decrease lipid burden in NPC patient fibroblasts.

Crosstalk between calcium and reactive oxygen species signaling in cancer revisited

The homeostasis of cellular reactive oxygen species (ROS) and calcium (Ca2+) are intricately linked. ROS signaling and Ca2+ signaling are reciprocally regulated within cellular microdomains and are crucial for transcription, metabolism and cell function. Tumor cells often highjack ROS and Ca2+ signaling mechanisms to ensure optimal cell survival and tumor progression. Expression and regulation of Ca2+ channels and transporters at the plasma membrane, endoplasmic reticulum, mitochondria and other endomembranes are often altered in tumor cells, and this includes their regulation by ROS and reactive nitrogen species (RNS). Likewise, alterations in cellular Ca2+ levels influence the generation and scavenging of oxidants and thus can alter the redox homeostasis of the cell. This interplay can be either beneficial or detrimental to the cell depending on the localization, duration and levels of ROS and Ca2+ signals. At one end of the spectrum, Ca2+ and ROS/RNS can function as signaling modules while at the other end, lethal surges in these species are associated with cell death. Here, we highlight the interplay between Ca2+ and ROS in cancer progression, emphasize the impact of redox regulation on Ca2+ transport mechanisms, and describe how Ca2+ signaling pathways, in turn, can regulate the cellular redox environment.

Unveiling the Role of Intracellular Dissolution Equilibria in the Antioxidant Mechanism of Ceria Nanoparticles

It is well-known that ceria nanoparticles (CNPs) exhibit significant antioxidant activity, offering potential applications in the treatment of ROS-related pathologies. This activity of CNPs as a nanozyme is typically interpreted by considering Ce(III)/Ce(IV) equilibria on the nanoparticles' surface. However, the validity of this mechanism has never been directly proven in a biological context. Furthermore, it is often overlooked that after endocytosis, CNPs are compartmentalized within endolysosomes, while ROS are primarily located in the cytoplasm, making their direct interaction difficult. This study presents chemical and biological evidence supporting an alternative mechanism of action. By utilizing synchrotron μXRF and μXANES analysis on individual cells, the study shows that the amount of Ce(III), the species responsible for the antioxidant activity, increases linearly with time within the endolysosomes, where CNPs are accumulated, and in their vicinity. Such an increase can be explained by the release of Ce3+ ions resulting from a partial reductive dissolution of CNPs in the acidic environment of the endolysosomes. The Ce3+ ions can then cross the endolysosomal membrane, reaching the cytosol, where they can exert their reducing activity on ROS. In fact, neutralizing the acidic endolysosomal pH results in a complete inhibition of the CNP activity. Consequently, CNP antioxidant activity should be regarded as the result of redox processes that extend beyond the nanoparticles surface but involve complex dissolution equilibria.

Correlation of organelle interactions in the development of non-alcoholic fatty liver disease

Organelles, despite having distinct functions, interact with each other. Interactions between organelles typically occur at membrane contact sites (MCSs) to maintain cellular homeostasis, allowing the exchange of metabolites and other pieces of information required for normal cellular physiology. Imbalances in organelle interactions may lead to various pathological processes. Increasing evidence suggests that abnormalorganelle interactions contribute to the pathogenesis of non-alcoholic fatty liver disease (NAFLD). However, the key role of organelle interactions in NAFLD has not been fully evaluated and researched. In this review, we summarize the role of organelle interactions in NAFLD and emphasize their correlation with cellular calcium homeostasis, lipid transport, and mitochondrial dynamics.

Logic-Gated DNA Intelligent Nanorobots for Cellular Lysosome Interference and Enhanced Therapeutics

Environment-recognizing DNA nanodevices have proven promising for cellular manipulation and disease treatment, whereas how to sequentially respond to different cellular microenvironments remains a challenge. To this end, here we elaborate a logic-gated intelligent DNA nanorobot (Gi-DR) for the cascade response to inter- and intra-cellular microenvironments, thereby achieving lysosome-targeted cargo delivery for subcellular interference and tumor treatment with enhanced efficacy. Utilizing G-quadruplexes to respond to high-level K+ in cancer cell surrounding, this Gi-DR nanorobot can activate an aptamer-based transmembrane DNA machine that delivers molecular payloads to cellular lysosome. Accordingly, the nanoassembly of Gi-DR is promoted by the folding of heterodimeric i-motifs in the acidic microenvironment. Such a design allows the extra-/intra-cellular behaviors of the Gi-DR nanorobot to be programmed by an YES-AND logic circuit, with environmental K+ and H+ as two inputs. As a consequence, DNA nanostrips are controllably formed in living cells, interfering with lysosomal function and thereby preventing cellular proliferation. Further, a therapeutic agent (i.e. ligand-drug conjugate) is delivered into target cancer cells for synergistic tumor treatment in vivo, exhibiting the super-enhanced cancer cell lethality and anti-tumor efficacy. It well illustrates that our designed logic-gated DNA nanorobot has broad application prospects in modulating cellular function and precision disease treatment.

Microplastics exacerbate ferroptosis via mitochondrial reactive oxygen species-mediated autophagy in chronic obstructive pulmonary disease

Microplastics (MPs) induce mitochondrial dysfunction and iron accumulation, contributing to mitochondrial macroautophagy/autophagy and ferroptosis, which has increased susceptibility to the exacerbation of chronic obstructive pulmonary disease (COPD); however, the underlying mechanism remains unclear. We demonstrated that MPs intensified inflammation in COPD by enhancing autophagy-dependent ferroptosis (ADF) in vitro and in vivo. In the lung tissues of patients with COPD, the concentrations of MPs, especially polystyrene microplastics (PS-MPs), were significantly higher than that of the control group, as detected by pyrolysis gas chromatography mass spectrometry (Py-GCMS), with increased iron accumulation. The exposure to PS-MPs, 2 μm in size, resulted in their being deposited in the lungs of COPD model mice detected by optical in vivo imaging, and observed in bronchial epithelial cells traced by GFP-labeled PS-MPs. There were mitochondrial impairments accompanied by mitochondrial reactive oxygen species (mito-ROS) overproduction and significantly increased levels of lysosome biogenesis and acidification in pDHBE cells with PS-MP stimulation, triggering occurrence of ferritinophagy and enhancing ADF in COPD, which triggered acute exacerbation of COPD (AECOPD). Reestablishing autophagy-dependent ferroptosis via mitochondria-specific ROS scavenging or ferroptosis inhibition alleviated excessive inflammation and ameliorated AECOPD induced by PS-MPs. Collectively, our data initially revealed that MPs exacerbate ferroptosis via mito-ROS-mediated autophagy in COPD, which sheds light on further hazard assessments of MPs on human respiratory health and potential therapeutic agents for patients with COPD.Abbreviations: ADF: autophagy-dependent ferroptosis; AECOPD: acute exacerbation of chronic obstructive pulmonary disease; Cchord: static compliance; COPD: chronic obstructive pulmonary disease; CQ: chloroquine; CS: cigarette smoke; DEGs: differentially expressed genes; Fer-1: ferrostatin-1; FEV 0.1: forced expiratory volume in first 100 ms; FVC: forced vital capacity; GSH: glutathione; HE: hematoxylin and eosin; IL1B/IL-1β: interleukin 1 beta; IL6: interleukin 6; MDA: malondialdehyde; Mito-ROS: mitochondrial reactive oxygen species; MMA: methyl methacrylate; MMF: maximal mid-expiratory flow curve; MMP: mitochondrial membrane potential; MOI: multiplicity of infection; MPs: microplastics; MV: minute volume; PA: polyamide; PBS: phosphate-buffered saline; PC: polycarbonate; pDHBE: primary human bronchial epithelial cell from COPD patients; PET: polyethylene terephthalate; PIF: peak inspiratory flow; PLA: polylactic acid; pNHBE: primary normal human bronchial epithelial cell; PS-MPs: polystyrene microplastics; PVA: polyvinyl acetate; PVC: polyvinyl chloride; Py-GCMS: pyrolysis gas chromatography mass spectrometry; SEM: scanning electron microscopy; Te: expiratory times; Ti: inspiratory times; TNF/TNF-α: tumor necrosis factor.

Small-molecule activation of TFEB alleviates Niemann-Pick disease type C via promoting lysosomal exocytosis and biogenesis

Niemann-Pick disease type C (NPC) is a devastating lysosomal storage disease characterized by abnormal cholesterol accumulation in lysosomes. Currently, there is no treatment for NPC. Transcription factor EB (TFEB), a member of the microphthalmia transcription factors (MiTF), has emerged as a master regulator of lysosomal function and promoted the clearance of substrates stored in cells. However, it is not known whether TFEB plays a role in cholesterol clearance in NPC disease. Here, we show that transgenic overexpression of TFEB, but not TFE3 (another member of MiTF family) facilitates cholesterol clearance in various NPC1 cell models. Pharmacological activation of TFEB by sulforaphane (SFN), a previously identified natural small-molecule TFEB agonist by us, can dramatically ameliorate cholesterol accumulation in human and mouse NPC1 cell models. In NPC1 cells, SFN induces TFEB nuclear translocation via a ROS-Ca2+-calcineurin-dependent but MTOR-independent pathway and upregulates the expression of TFEB-downstream genes, promoting lysosomal exocytosis and biogenesis. While genetic inhibition of TFEB abolishes the cholesterol clearance and exocytosis effect by SFN. In the NPC1 mouse model, SFN dephosphorylates/activates TFEB in the brain and exhibits potent efficacy of rescuing the loss of Purkinje cells and body weight. Hence, pharmacological upregulating lysosome machinery via targeting TFEB represents a promising approach to treat NPC and related lysosomal storage diseases, and provides the possibility of TFEB agonists, that is, SFN as potential NPC therapeutic candidates.

Focus on the Forgotten Organelle: Regulation of Lysosomes in Skeletal Muscle

Research on the role of the lysosome as the terminal organelle in autophagy and in communicating with other organelles in skeletal muscle is in its infancy. We hypothesize that the lysosome can adapt positively to exercise to improve the clearance of cargo, like dysfunctional mitochondria, within muscle, representing an important therapy for protein homeostasis in aging and muscle disuse.

Highly spatial-temporal electrochemical profiling of molecules trafficking at a single mitochondrion in one living cell

Simultaneous profiling of multiple molecules trafficking at a single organelle and the surrounding cytosol within a living cell is crucial for elucidating their functions, necessitating advanced techniques that provide high spatial-temporal resolution and molecule specificity. In this study, we present an electrochemical nanodevice based on a θ-nanopipette designed to coanalyze calcium ions (Ca2+) and reactive oxygen species (ROS) at a single mitochondrion and its surrounding cytosol, thereby enhancing our understanding of their trafficking within the signaling pathways of cellular autophagy. Two independent nanosensors integrated within the channels of the θ-nanopipette spatially isolate a single target mitochondrion from the cytosol and simultaneously measure the release of Ca2+ and ROS with high spatial-temporal resolution. Dynamic tracking reveals the direct trafficking of lysosomal Ca2+ to the mitochondrion rather than to the cytosol, which triggers ROS-induced ROS release within the mitochondria. Furthermore, highly temporal and concurrent observations revealed a second burst of Ca2+ in both the mitochondrion and the cytosol, which is not consistent with the change in ROS. These dynamic data elucidate the potential role of a beneficial feedback loop between the Ca2+ signaling pathway and the subsequent generation of mitochondrial ROS in ML-SA-induced autophagy. More importantly, this innovative platform facilitates detailed profiling of the molecular interactions between trafficking molecules within the mitochondria and the adjacent cytosolic environment, which is hardly realized using the current superresolution optical microscopy.

TRPML1 ion channel promotes HepaRG cell differentiation under simulated microgravity conditions

Stem cell differentiation must be regulated by intricate and complex interactions between cells and their surrounding environment, ensuring normal organ and tissue morphology such as the liver1. Though it is well acknowledged that microgravity provides necessary mechanical force signals for cell fate2, how microgravity affects growth, differentiation, and communication is still largely unknown due to the lack of real experimental scenarios and reproducibility tools. Here, Rotating Flat Chamber (RFC) was used to simulate ground-based microgravity effects to study how microgravity effects affect the differentiation of HepaRG (hepatic progenitor cells) cells. Unexpectedly, the results show that RFC conditions could promote HepaRG cell differentiation which exhibited increased expression of Alpha-fetoprotein (AFP), albumin (ALB), and Recombinant Cytokeratin 18 (CK18). Through screening a series of mechanical receptors, the ion channel TRPML1 was critical for promoting the differentiation effect under RFC conditions. Once TRPML1 was activated by stimulated microgravity effects, the concentration of lysosomal calcium ions was increased to activate the Wnt/β-catenin signaling pathway, which finally led to enhanced cell differentiation of HepaRG cells. In addition, the cytoskeleton was remodeled under RFC conditions to influence the expression of PI (3,5) P2, which is the best-known activator of TRPML1. In summary, our findings have established a mechanism by which simulated microgravity promotes the differentiation of HepaRG cells through the TRPML1 signaling pathway, which provides a potential target for the regulation of hepatic stem/progenitor cell differentiation and embryonic liver development under real microgravity conditions.

AAV-Mediated Gene Transfer of WDR45 Corrects Neurological Deficits in the Mouse Model of Beta-Propeller Protein-Associated Neurodegeneration

Beta-propeller protein-associated neurodegeneration (BPAN) is an ultra-rare, X-linked dominant, neurodevelopmental, and neurodegenerative disease caused by loss-of-function mutations in the WDR45 gene. It manifests in neurodevelopmental delay and seizures followed by secondary neurological decline with dystonia/parkinsonism and dementia in adolescence and early adulthood and is characterized by progressive accumulation of iron in the basal ganglia. WDR45 encodes β-propeller-shaped scaffold protein, or WD repeat domain phosphoinositide-interacting protein 4 (WIPI4), which plays an important role in autophagosome formation. While the mechanisms of how WIPI4 loss of function results in neurological decline and brain pathology have not yet been established, findings of lower autophagic activity provide a direct link between impaired autophagy and neurological disease in BPAN. Here we performed phenotypical characterization of a novel mouse model of BPAN, Wdr45_ex9+1g>a mouse. We identified hyperactive behavior and reduction of autophagy markers in brain tissue in Wdr45_ex9+1g>a hemizygous males as early as at 2 months of age. Given the early onset and spectrum of neurological symptoms such as hyper-arousal and attention deficits in human patients, this model presents a disease-relevant phenotype and can be used in preclinical studies. We used this mouse model for a proof-of-concept study to evaluate whether adeno-associated virus (AAV)-mediated central nervous system (CNS)-targeted gene transfer of WDR45 can provide therapeutic benefit and be considered a therapeutic paradigm for BPAN. We observed successful expression of human WDR45 transcripts and WIPI4 protein in the brain tissue, rescue of hyperactive behavior, and correction of autophagy markers. These data demonstrate that WDR45 gene transfer can be a promising therapeutic strategy for BPAN.

Acid Sphingomyelinase Regulates AdipoRon-Induced Differentiation of Arterial Smooth Muscle Cells via TFEB Activation

AdipoRon is a selective adiponectin receptor agonist that inhibits vascular remodeling by promoting the differentiation of arterial smooth muscle cells (SMCs). Our recent studies have demonstrated that activation of TFEB and its downstream autophagy-lysosomal signaling contribute to adipoRon-induced differentiation of SMCs. The present study was designed to examine whether acid sphingomyelinase (ASM; gene symbol Smpd1) is involved in mediating adipoRon-induced activation of TFEB-autophagy signaling and inhibition of proliferation/migration in arterial SMCs. Our results showed that adipoRon induced ASM expression and ceramide production in Smpd1+/+ SMCs, which were abolished in Smpd1-/- SMCs. Compared to Smpd1+/+ SMCs, Smpd1-/- SMCs exhibited less TFEB nuclear translocation and activation of autophagy signaling induced by adipoRon stimulation. SMC differentiation was further characterized by retarded wound healing, reduced proliferation, F-actin reorganization, and MMP downregulation. The results showed that Smpd1-/- SMCs were less responsive to adipoRon-induced differentiation than Smpd1+/+ SMCs. Mechanistically, adipoRon increased the expression of protein phosphatases such as calcineurin and PP2A in Smpd1+/+ SMCs. The calcineurin inhibitor FK506/cyclosporin A or PP2A inhibitor okadaic acid significantly attenuated adipoRon-induced activation of TFEB-autophagy signaling. In addition, adipoRon-induced expressions of calcineurin and PP2A were not observed in Smpd1-/- SMCs. However, activation of calcineurin by lysosomal TRPML1-Ca2+ channel agonist ML-SA1 rescued the activation of TFEB-autophagy signaling and the effects of adipoRon on cell differentiation in Smpd1-/- SMCs. Taken together, these data suggested that ASM regulates adipoRon-induced SMC differentiation through TFEB activation. This study provided novel mechanistic insights into the therapeutic effects of adipoRon on TFEB signaling and pathological vascular remodeling.

Crosstalk Between Autophagy and Oxidative Stress in Hematological Malignancies: Mechanisms, Implications, and Therapeutic Potential

Autophagy is a fundamental cellular process that maintains homeostasis by degrading damaged components and regulating stress responses. It plays a crucial role in cancer biology, including tumor progression, metastasis, and therapeutic resistance. Oxidative stress, similarly, is key to maintaining cellular balance by regulating oxidants and antioxidants, with its disruption leading to molecular damage. The interplay between autophagy and oxidative stress is particularly significant, as reactive oxygen species (ROS) act as both inducers and by-products of autophagy. While autophagy can function as a tumor suppressor in early cancer stages, it often shifts to a pro-tumorigenic role in advanced disease, aiding cancer cell survival under adverse conditions such as hypoxia and nutrient deprivation. This dual role is mediated by several signaling pathways, including PI3K/AKT/mTOR, AMPK, and HIF-1α, which coordinate the balance between autophagic activity and ROS production. In this review, we explore the mechanisms by which autophagy and oxidative stress interact across different hematological malignancies. We discuss how oxidative stress triggers autophagy, creating a feedback loop that promotes tumor survival, and how autophagic dysregulation leads to increased ROS accumulation, exacerbating tumorigenesis. We also examine the therapeutic implications of targeting the autophagy-oxidative stress axis in cancer. Current strategies involve modulating autophagy through specific inhibitors, enhancing ROS levels with pro-oxidant compounds, and combining these approaches with conventional therapies to overcome drug resistance. Understanding the complex relationship between autophagy and oxidative stress provides critical insights into novel therapeutic strategies aimed at improving cancer treatment outcomes.

Transient Receptor Potential Channels in Vascular Mechanotransduction

Transmural pressure and shear stress are mechanical forces that profoundly affect the smooth muscle cells (SMCs) comprising the vascular wall and the endothelial cells (ECs) lining the lumen. Pressure and flow are detected by mechanosensors in these cells and translated into appropriate responses to regulate blood pressure and flow. This review focuses on the role of the transient receptor potential (TRP) superfamily of cation channels in this process. We discuss how specific members of the TRP superfamily (TRPC6, TRPM4, TRPV1, TRPV4, and TRPP1) regulate the resting membrane and intracellular Ca2+ levels in SMCs and ECs to promote changes in vascular tone in response to intraluminal pressure and shear stress. Although TRP channels participate in vascular mechanotransduction, little evidence supports their intrinsic mechanosensitivity. Therefore, we also examine the evidence exploring the force-sensitive signal transduction pathways acting upstream of vascular TRP channels. Understanding the interplay between mechanosensors, force-induced signaling cascades, and TRP channels holds promise for the development of targeted therapies for diseases caused by vascular dysfunction.

Hyperosmotic Stress Promotes the Nuclear Translocation of TFEB in Tubular Epithelial Cells Depending on Intracellular Ca2+ Signals via TRPML Channels

Purpose

We previously demonstrated that hyperosmotic stress, which acts as mechanical stress, induces autophagy of tubular epithelial cells. This study aims to elucidate the molecular mechanisms of hyperosmolarity-induced autophagy. The research question addresses how hyperosmotic stress activates autophagy through transcription factor EB (TFEB) and Ca2+ signaling pathways, contributing to understanding cellular responses to mechanical stress.

Methods

NRK-52E normal rat kidney cells were subjected to hyperosmotic stress using mannitol-containing medium. Fluorescence microscopy was utilized to observe TFEB nuclear translocation, a crucial event in autophagy regulation. An intracellular Ca2+ chelator, BAPTA-AM, and a calcineurin inhibitor were used to dissect the Ca2+ signaling pathway involved in TFEB translocation. The phosphorylation of p70S6K, a substrate of the mammalian target of rapamycin complex 1 kinase, was analyzed to explore its role in TFEB localization. Additionally, the function of transient receptor potential mucolipin 1 (TRPML1), an intracellular Ca2+ channel, was assessed using pharmacological inhibition to determine its impact on TFEB translocation and autophagy marker LC3-II levels.

Results

Mannitol-induced hyperosmotic stress promoted the nuclear translocation of TFEB, which was completely abolished by treatment with BAPTA-AM. Inhibition of calcineurin suppressed TFEB nuclear translocation under hyperosmolarity, indicating that a signaling pathway governed by intracellular Ca2+ is involved in TFEB's nuclear translocation. In contrast, hyperosmotic stress did not significantly alter p70S6K phosphorylation. Pharmacological inhibition of TRPML1 attenuated both TFEB nuclear translocation and LC3-II upregulation in response to hyperosmotic stress.

Conclusions

Hyperosmotic stress promotes TFEB nuclear localization, and TRPML1-induced activation of calcineurin is involved in the mechanism of hyperosmolarity-induced autophagy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-024-00839-6.

Lysosomal cation channel TRPML1 suppression sensitizes acute myeloid leukemia cells to chemotherapeutics by inhibiting autophagy

Despite the implementation of novel therapeutic regimens and extensive research efforts, chemoresistance remains a formidable challenge in the treatment of acute myeloid leukemia (AML). Notably, the involvement of lysosomes in chemoresistance has sparked interest in developing lysosome-targeted therapies to sensitize tumor cells to currently approved chemotherapy or as innovative pharmacological approaches. Moreover, as ion channels on the lysosomal membrane are critical regulators of lysosomal function, they present potential as novel targets for enhancing chemosensitivity. Here, we discovered that the expression of a lysosomal cation channel, namely transient receptor potential mucolipin 1 (TRPML1), was elevated in AML cells. Inhibiting TRPML1 individually does not impact the proliferation and apoptosis of AML cells. Importantly, inhibition of TRPML1 demonstrated the potential to modulate the sensitivity of AML cells to chemotherapeutic agents. Exploration of the underlying mechanisms revealed that suppression of TRPML1 impaired autophagy while concurrently increasing the production of reactive oxygen species (ROS) and ROS-mediated lipid peroxidation (Lipid-ROS) in AML cells. Finally, the knockdown of TRPML1 significantly reduced OCI-AML3 tumor growth following chemotherapy in a mouse model of human leukemia. In summary, targeting TRPML1 represents a promising approach for combination therapy aimed at enhancing chemosensitivity in treating AML.

Simultaneous Live Mapping of pH and Hydrogen Peroxide Fluctuations in Autophagic Vesicles

Hydrogen peroxide (H2O2) plays a critical role in the regulation and progress of autophagy, an essential recycling process that influences cellular homeostasis and stress response. Autophagy is characterized by the formation of intracellular vesicles analogous to recycle "bags" called autophagosomes, which fuse with lysosomes to form autolysosomes, eventually ending up as lysosomes. We have developed two novel autophagic vesicle-targeted peptide-based sensors, ROSA for H2O2 and pHA for pH, to simultaneously track H2O2 and pH dynamics within autophagic vesicles as autophagy advances. Since pH values progressively decrease within autophagic vesicles with the progress of autophagy, we utilized information on vesicular pH to identify stages of autophagic vesicles in live cells. Fluorescence intensities of the H2O2 sensor, ROSA, within autophagic compartments at different autophagic stages, which were identified by simultaneous pH mapping, revealed that H2O2 levels vary significantly within autophagic vesicles as autophagy progresses, with maximum H2O2 levels in the autolysosomal stage. This study provides the first detailed observation of H2O2 fluctuations within autophagic vesicles throughout the entire process of autophagy in living mammalian cells, offering insights into the oxidative changes associated with this vital cellular process.

Lysosomes finely control macrophage inflammatory function via regulating the release of lysosomal Fe2+ through TRPML1 channel

Lysosomes are best known for their roles in inflammatory responses by engaging in autophagy to remove inflammasomes. Here, we describe an unrecognized role for the lysosome, showing that it finely controls macrophage inflammatory function by manipulating the lysosomal Fe2+-prolyl hydroxylase domain enzymes (PHDs)-NF-κB-interleukin 1 beta (IL1B) transcription pathway that directly links lysosomes with inflammatory responses. TRPML1, a lysosomal cationic channel, is activated secondarily to ROS elevation upon inflammatory stimuli, which in turn suppresses IL1B transcription, thus limiting the excessive production of IL-1β in macrophages. Mechanistically, the suppression of IL1B transcription caused by TRPML1 activation results from its modulation on the release of lysosomal Fe2+, which subsequently activates PHDs. The activated PHDs then represses transcriptional activity of NF-κB, ultimately resulting in suppressed IL1B transcription. More importantly, in vivo stimulation of TRPML1 ameliorates multiple clinical signs of Dextran sulfate sodium-induced colitis in mice, suggesting TRPML1 has potential in treating inflammatory bowel disease.

Lysosome-Mitochondrial Crosstalk in Cellular Stress and Disease

The perception of lysosomes and mitochondria as entirely separate and independent entities that degrade material and produce ATP, respectively, has been challenged in recent years as not only more complex roles for both organelles, but also an unanticipated level of interdependence are being uncovered. Coupled lysosome and mitochondrial function and dysfunction involve complex crosstalk between the two organelles which goes beyond mitochondrial quality control and lysosome-mediated clearance of damaged mitochondria through mitophagy. Our understanding of crosstalk between these two essential metabolic organelles has been transformed by major advances in the field of membrane contact sites biology. We now know that membrane contact sites between lysosomes and mitochondria play central roles in inter-organelle communication. This importance of mitochondria-lysosome contacts (MLCs) in cellular homeostasis, evinced by the growing number of diseases that have been associated with their dysregulation, is starting to be appreciated. How MLCs are regulated and how their coordination with other pathways of lysosome-mitochondria crosstalk is achieved are the subjects of ongoing scrutiny, but this review explores the current understanding of the complex crosstalk governing the function of the two organelles and its impact on cellular stress and disease.

Activation of lysosomal Ca2+ channels mitigates mitochondrial damage and oxidative stress

Elevated levels of plasma-free fatty acids and oxidative stress have been identified as putative primary pathogenic factors in endothelial dysfunction etiology, though their roles are unclear. In human endothelial cells, we found that saturated fatty acids (SFAs)-including the plasma-predominant palmitic acid (PA)-cause mitochondrial fragmentation and elevation of intracellular reactive oxygen species (ROS) levels. TRPML1 is a lysosomal ROS-sensitive Ca2+ channel that regulates lysosomal trafficking and biogenesis. Small-molecule agonists of TRPML1 prevented PA-induced mitochondrial damage and ROS elevation through activation of transcriptional factor EB (TFEB), which boosts lysosome biogenesis and mitophagy. Whereas genetically silencing TRPML1 abolished the protective effects of TRPML1 agonism, TRPML1 overexpression conferred a full resistance to PA-induced oxidative damage. Pharmacologically activating the TRPML1-TFEB pathway was sufficient to restore mitochondrial and redox homeostasis in SFA-damaged endothelial cells. The present results suggest that lysosome activation represents a viable strategy for alleviating oxidative damage, a common pathogenic mechanism of metabolic and age-related diseases.

Gold nanoclusters Au25AcCys18 normalize intracellular ROS without increasing cytoplasmic alarmin acHMGB1 abundance in human microglia and neurons

This study focuses on the modulatory effects of gold nanoclusters with 25 gold atoms and 18 acetyl cysteines (Au25AcCys18) in human microglia, human iPSC-derived neurons and SH-SY5Y differentiated human neuronal cells. The combination of chemical, biological, and computational methods shows the well-retained viability of these human cells treated with Au25AcCys18, interactions between Au25AcCys18 and transcription factor TFEB (computational approach), interactions between TFEB and HMGB1 (proximity ligation assay and molecular modeling using AlphaFold), modulation of the abundance and location of acHMGB1 by Au25AcCys18 (immunocytochemistry), and the reduction of ROS in cells treated with Au25AcCys18 (CellROX live imaging). These novel findings in human neural cells, particularly neurons, encourage further studies in experimental animal models of neurological disorders and/or human organoids to exploit the unique structural and photophysical properties of gold nanoclusters and to better understand their ability to modulate molecular mechanisms in human cells.

A role for lysosomal calcium channels in mitigating mitochondrial damage and oxidative stress

Elevated free fatty acids and oxidative stress may function as pathogenic factors in endothelial dysfunction that is associated with various cardiovascular complications. In recent work, Feng and colleagues report that activation of a lysosomal Ca2+ channel may be a viable option to alleviate oxidative damage by boosting lysosome biogenesis and mitophagy.

A Mitochondria-Targeting and Peroxynitrite-Activatable Ratiometric Fluorescent Probe for Precise Tracking of Oxidative Stress-Induced Mitophagy

Mitochondria are the energy factory of cells and can be easily damaged by reactive oxygen species (ROS) because of the frequent occurrence of oxidative stress. Abnormality in mitophagy is often associated with many diseases including inflammation, cancer, and aging. While previously developed fluorescent probes mainly focus on detecting just ROS or mitophagy, quite rare studies have endeavored to comprehensively capture the entire mitophagic process, encompassing both the production of ROS and the induction of mitophagy. Herein, we report a new ratiometric fluorescent probe NA-DP for tracking peroxynitrite (ONOO-) as well as the subsequent oxidative stress-induced mitophagy. To a naphthalimide-based dye, an ONOO--responsive diphenyl phosphinate moiety and the mitochondria-targeting triphenylphosphonium group were attached. The probe showed a highly selective response to ONOO- through an addition-elimination reaction with diphenyl phosphinate. Owing to its outstanding pH stability and organelle-targeting ability, NA-DP was successfully used to detect mitophagy induced by oxidative stress after the generation of ONOO-. In the meantime, the probe was also used to track starvation-induced mitophagy and indicate that starvation-induced mitophagy is independent of ONOO-. Therefore, NA-DP has the ability to precisely track oxidative stress-induced mitophagy by distinguishing it from starvation-induced mitophagy. This study offers a new chemical tool to study the relationship between ROS generation and mitophagy.

Corydaline attenuates osteolysis in rheumatoid arthritis via mitigating reactive oxygen species production and suppressing calcineurin-Nfatc1 signaling

AIM OF THE STUDY

Osteolysis in Rheumatoid arthritis (RA) is principally provoked by osteoclast hyperactivity. This study aims to employ Corydaline (Cory), a plant extract, as an osteoclast inhibitor in treating RA-inflicted osteolysis while unveiling the corresponding mechanism.

MATERIALS AND METHODS

Osteoclasts were derived from mouse bone marrow-derived monocytes (BMMs) stimulated with M-CSF and RANKL. Subsequently, utilizing network pharmacology, we performed a thorough analysis of Cory's molecular structure and discerned its preliminary therapeutic potential. Subsequently, LPS was used to simulate and establish an in vitro model of RA, and the biological effect of Cory on osteoclast behaviors was evaluated through various staining methods, RT-qPCR, and Western blot. In addition, a collagen-induced arthritis (CIA) mouse model was developed to evaluate the therapeutic effects of Cory in vivo.

RESULTS

The results from network pharmacology indicated a significant correlation between Cory, oxidative stress, and calcium signaling. Subsequent in vitro experiments demonstrated Cory's capacity to inhibit the formation and function of osteoclast under inflammatory stimuli, thereby protecting against abnormal bone resorption. This effect is achieved by activating the Nrf2 signaling pathway, mitigating the generation of reactive oxygen species (ROS), and modulating the calcineurin-Nfatc1 signaling. Furthermore, this therapeutic effect of Cory on RA-associated osteolysis was proved in CIA mice models.

CONCLUSIONS

Cory demonstrates the potential to activate the Nrf2 signaling pathway, effectively countering oxidative stress, and simultaneously inhibit the calcineurin-Nfatc1 signaling pathway to regulate the terminals of calcium signaling. These dual effects collectively reduce osteoclast activity, ultimately contributing to a therapeutic role in RA osteolysis. Therefore, our study presents Cory as a novel pharmaceutical candidate for the prevention and treatment of RA.

Tangningtongluo Tablet ameliorates pancreatic damage in diabetic mice by inducing autophagy and inhibiting the PI3K/Akt/mTOR signaling pathway

BACKGROUND

Diabetes is a metabolic disease characterized by hyperglycaemia. Tangningtongluo Tablet (TNTL) is an inpatient formula extensively utilized to treat diabetes mellitus (DM), but the protective mechanism is not clear. This study aimed to investigate the relevant mechanisms by which TNTL affects pancreatic damage in diabetic mice and autophagy.

METHODS

The impact of TNTL on pancreatic damage in diabetic mice in vitro and in vivo was investigated via glucose and lipid metabolism analyses, HE staining, CCK-8, TUNEL staining, Annexin V/PI, and Western blotting. Molecular docking and Western blotting were used to verify the results of network pharmacological analysis, which was carried out to explore the mechanism by which TNTL affects DM. The autophagosome levels were visualized via RFP-GFP-LC3 and transmission electron microscopy, and lysosomal function was evaluated via Lysotracker red staining. Western blot, immunohistochemistry and immunofluorescence staining were used to detect the expression of the autophagy proteins LC3, p62 and LAMP2.

RESULTS

Compared with the model group, TNTL protected pancreas from oxidative stress, decreased the level of MDA, increased the levels of SOD and GSH-px, induced the occurrence of autophagy and decreased the levels of apoptotic factors. Moreover, TNTL inhibited the protein expression of p-PI3K, p-Akt and p-mTOR, increased the levels of LC3 and LAMP2 and decreased the level of p62, and the autophagy inhibitor CQ blocked the protective effect of TNTL on pancreatic damage in diabetic mice.

CONCLUSION

These results demonstrated that TNTL ameliorated pancreatic damage in diabetic mice by inhibiting the PI3K/Akt/mTOR signaling and regulating autophagy.

Dynamic regulation of proximal tubular autophagy from injury to repair after ischemic kidney damage

BACKGROUND

The role of proximal tubular autophagy in repairing kidney injury following ischemia remains unclear.

METHODS

In this study, we utilized mice with conditional deletion of the Atg5 gene in proximal tubules and monitored the long-term dynamic regulation of autophagy following ischemic acute kidney injury (AKI).

RESULTS

The results showed that Atg5-deficient proximal tubule epithelial cells exhibited damaged mitochondria, concentric membranes, and lysosomal accumulation 24 h after ischemia/reperfusion. However, 28 days after ischemia/reperfusion, concentric membrane bodies remained, but lysosomal accumulation was no longer observed. Notably, the absence of Atg5 in renal tubular epithelial cells impaired renal function and led to increased tubular cell proliferation and oxidative stress in the early stage of injury. However, during the repair period following AKI, Atg5 deficiency exhibited no significant difference in the expression of proliferating cell nuclear antigen (PCNA) and 4-hydoxynonenal (4HNE), suggesting that the improvement in renal fibrosis associated with Atg5 deficiency is unlikely to result from its effect on cell proliferation or reactive oxygen species levels. Additionally, Atg5 deficiency inhibits the secretion of profibrotic factor fibroblast growth factor 2 (FGF2) from the early stage of renal injury to the recovery stage of AKI, indicating that autophagy-specific regulation of FGF2 secretion is a dynamic process overlapping with other stages of injury. Furthermore, increased co-localization of ATG5 with 4HNE and FGF2 was observed in patient samples.

CONCLUSION

In summary, our results suggest that the dynamic regulation of autophagy on key molecules involved in kidney injury and repair varies with the stage of kidney injury.

Integration of transcriptional and epigenetic regulation of TFEB reveals its dual functional roles in Pan-cancer

Transcription factor EB (TFEB) mainly regulates the autophagy-lysosomal pathway, associated with many diseases, including cancer. However, the role of TFEB in pan-cancer has not been investigated systematically. In this study, we comprehensively analyzed TFEB targets under three stresses in Hela cells by cross-validation of RNA-seq and ChIP-seq. 1712 novel TFEB targets have not been reported in the Gene Set Enrichment Analysis and ChIP Enrichment Analysis databases. We further investigated their distributions and roles among the pan-cancer co-expression networks across 32 cancers constructed by multiscale embedded gene co-expression network analysis (MEGENA) based on the Cancer Genome Atlas (TCGA) cohort. Specifically, TFEB might serve as a hidden player with multifaceted functions in regulating pan-cancer risk factors, e.g. CXCL2, PKMYT1 and BUB1, associated with cell cycle and immunosuppression. TFEB might also regulate protective factors, e.g. CD79A, related to immune promotion in the tumor microenvironment. We further developed a Shiny app website to present the comprehensive regulatory targets of TFEB under various stimuli, intending to support further research on TFEB functions. Summarily, we provided references for the TFEB downstream targets responding to three stresses and the dual roles of TFEB and its targets in pan-cancer, which are promising anticancer targets that warrant further exploration.

LAMTOR1 regulates dendritic lysosomal positioning in hippocampal neurons through TRPML1 inhibition

Intracellular lysosomal trafficking and positioning are fundamental cellular processes critical for proper neuronal function. Among the diverse array of proteins involved in regulating lysosomal positioning, the Transient Receptor Potential Mucolipin 1 (TRPML1) and the Ragulator complex have emerged as central players. TRPML1, a lysosomal cation channel, has been implicated in lysosomal biogenesis, endosomal/lysosomal trafficking including in neuronal dendrites, and autophagy. LAMTOR1, a subunit of the Ragulator complex, also participates in the regulation of lysosomal trafficking. Here we report that LAMTOR1 regulates lysosomal positioning in dendrites of hippocampal neurons by interacting with TRPML1. LAMTOR1 knockdown (KD) increased lysosomal accumulation in proximal dendrites of cultured hippocampal neurons, an effect reversed by TRPML1 KD or inhibition. On the other hand, TRPML1 activation with ML-SA1 or prevention of TRPML1 interaction with LAMTOR1 using a TAT-decoy peptide induced dendritic lysosomal accumulation. LAMTOR1 KD-induced proximal dendritic lysosomal accumulation was blocked by the dynein inhibitor, ciliobrevin D, suggesting the involvement of a dynein-mediated transport. These results indicate that LAMTOR1-mediated inhibition of TRPML1 is critical for normal dendritic lysosomal distribution and that release of this inhibition or direct activation of TRPML1 results in abnormal dendritic lysosomal accumulation. The roles of LAMTOR1-TRPML1 interactions in lysosomal trafficking and positioning could have broad implications for understanding cognitive disorders associated with lysosomal pathology and calcium dysregulation.

Mechanisms of autophagy-lysosome dysfunction in neurodegenerative diseases

Autophagy is a lysosome-based degradative process used to recycle obsolete cellular constituents and eliminate damaged organelles and aggregate-prone proteins. Their postmitotic nature and extremely polarized morphologies make neurons particularly vulnerable to disruptions caused by autophagy-lysosomal defects, especially as the brain ages. Consequently, mutations in genes regulating autophagy and lysosomal functions cause a wide range of neurodegenerative diseases. Here, we review the role of autophagy and lysosomes in neurodegenerative diseases such as Alzheimer disease, Parkinson disease and frontotemporal dementia. We also consider the strong impact of cellular ageing on lysosomes and autophagy as a tipping point for the late-age emergence of related neurodegenerative disorders. Many of these diseases have primary defects in autophagy, for example affecting autophagosome formation, and in lysosomal functions, especially pH regulation and calcium homeostasis. We have aimed to provide an integrative framework for understanding the central importance of autophagic-lysosomal function in neuronal health and disease.

Metabolic stress induces a double-positive feedback loop between AMPK and SQSTM1/p62 conferring dual activation of AMPK and NFE2L2/NRF2 to synergize antioxidant defense

Co-occurring mutations in KEAP1 in STK11/LKB1-mutant NSCLC activate NFE2L2/NRF2 to compensate for the loss of STK11-AMPK activity during metabolic adaptation. Characterizing the regulatory crosstalk between the STK11-AMPK and KEAP1-NFE2L2 pathways during metabolic stress is crucial for understanding the implications of co-occurring mutations. Here, we found that metabolic stress increased the expression and phosphorylation of SQSTM1/p62, which is essential for the activation of NFE2L2 and AMPK, synergizing antioxidant defense and tumor growth. The SQSTM1-driven dual activation of NFE2L2 and AMPK was achieved by inducing macroautophagic/autophagic degradation of KEAP1 and facilitating the AXIN-STK11-AMPK complex formation on the lysosomal membrane, respectively. In contrast, the STK11-AMPK activity was also required for metabolic stress-induced expression and phosphorylation of SQSTM1, suggesting a double-positive feedback loop between AMPK and SQSTM1. Mechanistically, SQSTM1 expression was increased by the PPP2/PP2A-dependent dephosphorylation of TFEB and TFE3, which was induced by the lysosomal deacidification caused by low glucose metabolism and AMPK-dependent proton reduction. Furthermore, SQSTM1 phosphorylation was increased by MAP3K7/TAK1, which was activated by ROS and pH-dependent secretion of lysosomal Ca2+. Importantly, phosphorylation of SQSTM1 at S24 and S226 was critical for the activation of AMPK and NFE2L2. Notably, the effects caused by metabolic stress were abrogated by the protons provided by lactic acid. Collectively, our data reveal a novel double-positive feedback loop between AMPK and SQSTM1 leading to the dual activation of AMPK and NFE2L2, potentially explaining why co-occurring mutations in STK11 and KEAP1 happen and providing promising therapeutic strategies for lung cancer.Abbreviations: AMPK: AMP-activated protein kinase; BAF1: bafilomycin A1; ConA: concanamycin A; DOX: doxycycline; IP: immunoprecipitation; KEAP1: kelch like ECH associated protein 1; LN: low nutrient; MAP3K7/TAK1: mitogen-activated protein kinase kinase kinase 7; MCOLN1/TRPML1: mucolipin TRP cation channel 1; MEFs: mouse embryonic fibroblasts; MTORC1: mechanistic target of rapamycin kinase complex 1; NAC: N-acetylcysteine; NFE2L2/NRF2: NFE2 like bZIP transcription factor 2; NSCLC: non-small cell lung cancer; PRKAA/AMPKα: protein kinase AMP-activated catalytic subunit alpha; PPP2/PP2A: protein phosphatase 2; ROS: reactive oxygen species; PPP3/calcineurin: protein phosphatase 3; RPS6KB1/p70S6K: ribosomal protein S6 kinase B1; SQSTM1/p62: sequestosome 1; STK11/LKB1: serine/threonine kinase 11; TCL: total cell lysate; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3; V-ATPase: vacuolar-type H+-translocating ATPase.

PbrATG6 modulates reactive oxygen species metabolism and interacts with PbrTLP15 synergistic enhancement of pear resistance to Botryosphaeria dothidea

Autophagy is vital for plant defense against pathogens, with ATG6 being a key gene in this process. At present, little has been reported on the potential function and molecular mechanisms of ATG6 mediated pathogen resistance in pear. This study investigates the function of the pear homolog of ATG6 (PbrATG6) in resistance to Botryosphaeria dothidea. PbrATG6 is expressed differentially in pear tissues and its expression increases upon infection. Overexpression of PbrATG6 enhances resistance in Arabidopsis and pear calli, while silencing it increases susceptibility. PbrTLP15, a pathogenesis-related protein belonging to the PR5 family, was found that interacts with PbrATG6 by a yeast two-hybrid screening. Yeast two-hybrid, luciferase complementation imaging, bimolecular fluorescence complementation assays and pull-down assays showed that PbrATG6 interacts with PbrTLP15. The transient silencing transgenic assays of PbrATG6 and PbrTLP15 revealed that PbrATG6 could cooperate with PbrTLP15 to regulate pear B. dothidea resistance. In addition, transcriptional analyses of autophagy key genes in pTRV-PbrTLP15 and transmission electron microscopy (TEM) assays also implied that PbrTLP15 does affect autophagy. Hence, PbrATG6 and PbrTLP15 may synergistically enhance pear B. dothidea disease resistance. It provides a new strategy for the study of autophagy in pear disease resistance and enriches the research on pear disease resistance mechanism.

LW-213, a derivative of wogonin, triggers reticulophagy-mediated cell death in NSCLC via lysosomal damage combined with NPC1 inhibition

BACKGROUND

Maintaining intracellular equilibrium is essential for the viability of tumor cells, which tend to be particularly vulnerable to environmental stressors. Consequently, targeting the disruption of this homeostasis offers a promising approach for oncological treatments. LW-213, a novel derivative of wogonin, effectively induces apoptosis in cancer cells by initiating endoplasmic reticulum (ER) stress, although the precise molecular pathways involved remain intricate and multifaceted.

PURPOSE

This research aimed to explore how LW-213 prompts apoptosis in non-small cell lung cancer (NSCLC) cells and to clarify the detailed mechanisms that govern this process.

METHODS

Various NSCLC cell lines were utilized to delineate the apoptotic effects induced by LW-213. Advanced methodologies, including RNA sequencing (RNA-seq), Western blotting (WB), immunofluorescence (IF), immunoprecipitation (IP), flow cytometry (Fc), real-time quantitative polymerase chain reaction (RT-qPCR), and electron microscopy, were employed to investigate the underlying molecular interactions. The efficacy and mechanistic action of LW-213 were also assessed in a xenograft model using nude mice.

RESULTS

We demonstrated that LW-213, a small molecule cationic amphiphilic drug (CAD), inhibited Niemann-Pick C1 (NPC1) function and induced lysosomal membrane damage, thereby activating the phosphoinositide-initiated membrane tethering and lipid transport (PITT) pathway. This activation promoted cholesterol transport from the ER to the lysosome, perpetuating a cholesterol-deficient state in the ER, including massive exocytosis of Ca2+ and activation of FAM134B-mediated reticulophagy. Ultimately, excessive reticulophagy induced lethal ER stress.

CONCLUSIONS

In summary, our study elucidates an organelle domino reaction initiated by lysosome damage and a series of self-rescue mechanisms that eventually lead to irreversible lethal effects, revealing a potential drug intervention strategy.

Early Cardiac Ischemia-Reperfusion Injury: Interactions of Autophagy with Galectin-3 and Oxidative Stress

Background: Cardiovascular diseases are the leading cause of death worldwide, including the United Arab Emirates. Ischemia-reperfusion (IR) injury results in the death of cardiac myocytes that were viable immediately before myocardial reperfusion. We aim to investigate the role of galectin-3 (Gal-3) in autophagy during ischemia-reperfusion injuries. Methods: Male C57B6/J and Gal-3 knockout (KO) mice were used for the murine model of IR injury. Heart samples and serum were collected 24 h post-IR and were processed for immunohistochemical and immunofluorescent labeling and an enzyme-linked immunosorbent assay. Results: There was a significant increase in left ventricle (LV) concentrations of Gal-3 in Gal-3 wild-type mice compared to sham mice. There were significantly higher concentrations of LV autophagy proteins and phospho-AMPK in IR Gal-3 KO mice than in IR Gal-3 wild-type mice, compared to lower concentrations of LV phospho-mTOR and p62 in IR Gal-3 KO than in IR wild-type mice. Antioxidant activities were higher in the LVs of IR Gal-3 wild-type mice, while oxidative stress was higher in the LVs of IR Gal-3 KO mice. Conclusions: Our study supports the interaction of Gal-3 with autophagy proteins, oxidative stress, and antioxidant proteins and demonstrates that the absence of Gal-3 can enhance autophagy in the heart after IR injury.

Targeting sub-cellular organelles for boosting precision photodynamic therapy

Among various cancer treatment methods, photodynamic therapy has received significant attention due to its non-invasiveness and high efficiency in inhibiting tumour growth. Recently, specific organelle targeting photosensitizers have received increasing interest due to their precise accumulation and ability to trigger organelle-mediated cell death signalling pathways, which greatly reduces the drug dosage, minimizes toxicity, avoids multidrug resistance, and prevents recurrence. In this review, recent advances and representative photosensitizers used in targeted photodynamic therapy on organelles, specifically including the endoplasmic reticulum, Golgi apparatus, mitochondria, nucleus, and lysosomes, have been comprehensively reviewed with a focus on organelle structure and organelle-mediated cell death signalling pathways. Furthermore, a perspective on future research and potential challenges in precision photodynamic therapy has been presented at the end.

TMX2 potentiates cell viability of hepatocellular carcinoma by promoting autophagy and mitophagy

The dysregulation of membrane protein expression has been implicated in tumorigenesis and progression, including hepatocellular carcinoma (HCC). In this study, we aimed to identify membrane proteins that modulate HCC viability. To achieve this, we performed a CRISPR activation screen targeting human genes encoding membrane-associated proteins, revealing TMX2 as a potential driver of HCC cell viability. Gain- and loss-of-function experiments demonstrated that TMX2 promoted growth and tumorigenesis of HCC. Clinically, TMX2 was an independent prognostic factor for HCC patients. It was significantly upregulated in HCC tissues and associated with poor prognosis of HCC patients. Mechanistically, TMX2 was demonstrated to promote macroautophagy/autophagy by facilitating KPNB1 nuclear export and TFEB nuclear import. In addition, TMX2 interacted with VDAC2 and VADC3, assisting in the recruitment of PRKN to defective mitochondria to promote cytoprotective mitophagy during oxidative stress. Most interestingly, HCC cells responded to oxidative stress by upregulating TMX2 expression and cell autophagy. Knockdown of TMX2 enhanced the anti-tumor effect of lenvatinib. In conclusion, our findings emphasize the pivotal role of TMX2 in driving the HCC cell viability by promoting both autophagy and mitophagy. These results suggest that TMX2 May serve as a prognostic marker and promising therapeutic target for HCC treatment.Abbreviation: CCCP: Carbonyl cyanide 3-chlorophenylhydrazone; Co-IP: co-immunoprecipitation; CRISPR: clustered regularly interspaced short palindromic repeat; ER: endoplasmic reticulum; HCC: hepatocellular carcinoma; KPNB1: karyopherin subunit beta 1; PRKN: parkin RBR E3 ubiquitin protein ligase; ROS: reactive oxygen species; TFEB: transcription factor EB; TMX2: thioredoxin related transmembrane protein 2; VDAC2: voltage dependent anion channel 2; VDAC3: voltage dependent anion channel 3; WB: western blot.

Calcineurin promotes adaptation to chronic stress through two distinct mechanisms

Adaptation to environmental stress requires coordination between stress-defense programs and cell cycle progression. The immediate response to many stressors has been well characterized, but how cells survive in challenging environments long term is unknown. Here, we investigate the role of the stress-activated phosphatase calcineurin (CN) in adaptation to chronic CaCl2 stress in Saccharomyces cerevisiae. We find that prolonged exposure to CaCl2 impairs mitochondrial function and demonstrate that cells respond to this stressor using two CN-dependent mechanisms-one that requires the downstream transcription factor Crz1 and another that is Crz1 independent. Our data indicate that CN maintains cellular fitness by promoting cell cycle progression and preventing CaCl2-induced cell death. When Crz1 is present, transient CN activation suppresses cell death and promotes adaptation despite high levels of mitochondrial loss. However, in the absence of Crz1, prolonged activation of CN prevents mitochondrial loss and further cell death by upregulating glutathione biosynthesis genes thereby mitigating damage from reactive oxygen species. These findings illustrate how cells maintain long-term fitness during chronic stress and suggest that CN promotes adaptation in challenging environments by multiple mechanisms.

Preservation of Mitochondrial Function by SkQ1 in Skin Fibroblasts Derived from Patients with Leber's Hereditary Optic Neuropathy Is Associated with the PINK1/PRKN-Mediated Mitophagy

Increased or altered mitochondrial ROS production in the retinal ganglion cells is regarded as the chief culprit of the disease-causing Leber's hereditary optic neuropathy (LHON). SkQ1 is a rechargeable mitochondria-targeted antioxidant with high specificity and efficiency. SkQ1 has already been used to treat LHON patients, and a phase 2a randomized clinical trial of SkQ1 has demonstrated improvements in eyesight. However, the underlying mechanism of SkQ1 in LHON remains unclear. This study aimed to assess the effects and molecular mechanism of SkQ1 in the preservation of mitochondrial function using skin fibroblasts derived from LHON patients. Our study found that SkQ1 could reduce ROS production and stabilize the mitochondrial membrane. Mechanistically, through network pharmacology and molecular docking, we identified the key targets of SkQ1 as SOD2 and PINK1, which play crucial roles in redox and mitophagy. SkQ1 interacted with PINK1 and downregulated its expression to balance mitochondrial homeostasis. Collectively, the findings of our study reveal that by regulating PINK1/PRKN-mediated mitophagy, SkQ1 preserves mitochondrial function in LHON fibroblasts. The data indicate that SkQ1 may be a novel therapeutic intervention to prevent the progression of LHON.

ROS-mediated lysosomal membrane permeabilization and autophagy inhibition regulate bleomycin-induced cellular senescence

Bleomycin exhibits effective chemotherapeutic activity against multiple types of tumors, and also induces various side effects, such as pulmonary fibrosis and neuronal defects, which limit the clinical application of this drug. Macroautophagy/autophagy has been recently reported to be involved in the functions of bleomycin, and yet the mechanisms of their crosstalk remain insufficiently understood. Here, we demonstrated that reactive oxygen species (ROS) produced during bleomycin activation hampered autophagy flux by inducing lysosomal membrane permeabilization (LMP) and obstructing lysosomal degradation. Exhaustion of ROS with N-acetylcysteine relieved LMP and autophagy defects. Notably, we observed that LMP and autophagy blockage preceded the emergence of cellular senescence during bleomycin treatment. In addition, promoting or inhibiting autophagy-lysosome degradation alleviated or exacerbated the phenotypes of senescence, respectively. This suggests the alternation of autophagy activity is more a regulatory mechanism than a consequence of bleomycin-induced cellular senescence. Taken together, we reveal a specific role of bleomycin-induced ROS in mediating defects of autophagic degradation and further regulating cellular senescence in vitro and in vivo. Our findings, conversely, indicate the autophagy-lysosome degradation pathway as a target for modulating the functions of bleomycin. These provide a new perspective for optimizing bleomycin as a clinically applicable chemotherapeutics devoid of severe side-effects.Abbreviations: AT2 cells: type II alveolar epithelial cells; ATG7: autophagy related 7; bEnd.3: mouse brain microvascular endothelial cells; BNIP3L: BCL2/adenovirus E1B interacting protein 3-like; CCL2: C-C motif chemokine ligand 2; CDKN1A: cyclin dependent kinase inhibitor 1A; CDKN2A: cyclin dependent kinase inhibitor 2A; FTH1: ferritin heavy polypeptide 1; γ-H2AX: phosphorylated H2A.X variant histone; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HUVEC: human umbilical vein endothelial cells; HT22: hippocampal neuronal cell lines; Il: interleukin; LAMP: lysosomal-associated membrane protein; LMP: lysosome membrane permeabilization; MTORC1: mechanistic target of rapamycin kinase complex 1; NAC: N-acetylcysteine; NCOA4: nuclear receptor coactivator 4; PI3K: phosphoinositide 3-kinase; ROS: reactive oxygen species; RPS6KB/S6K: ribosomal protein S6 kinase; SA-GLB1/β-gal: senescence-associated galactosidase, beta 1; SAHF: senescence-associated heterochromatic foci; SASP: senescence-associated secretory phenotype; SEC62: SEC62 homolog, preprotein translocation; SEP: superecliptic pHluorin; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB.

NLRP4 renders pancreatic cancer resistant to olaparib through promotion of the DNA damage response and ROS-induced autophagy

Olaparib has been approved as a therapeutic option for metastatic pancreatic ductal adenocarcinoma patients with BRCA1/2 mutations. However, a significant majority of pancreatic cancer patients have inherent resistance or develop tolerance to olaparib. It is crucial to comprehend the molecular mechanism underlying olaparib resistance to facilitate the development of targeted therapies for pancreatic cancer. In this study, we conducted an analysis of the DepMap database to investigate gene expression variations associated with olaparib sensitivity. Our findings revealed that NLRP4 upregulation contributes to increased resistance to olaparib in pancreatic cancer cells, both in vitro and in vivo. RNA sequencing and Co-IP MS analysis revealed that NLRP4 is involved in the DNA damage response and autophagy pathway. Our findings confirmed that NLRP4 enhances the capacity for DNA repair and induces the production of significant levels of reactive oxygen species (ROS) and autophagy in response to treatment with olaparib. Specifically, NLRP4-generated mitochondrial ROS promote autophagy in pancreatic cancer cells upon exposure to olaparib. However, NLRP4-induced ROS do not affect DNA damage. The inhibition of mitochondrial ROS using MitoQ and autophagy using chloroquine (CQ) may render cells more susceptible to the effects of olaparib. Taken together, our findings highlight the significant roles played by NLRP4 in the processes of autophagy and DNA repair when pancreatic cancer cells are treated with olaparib, thereby suggesting the potential therapeutic utility of olaparib in pancreatic cancer patients with low NLRP4 expression.

Nanohybrid-Based Redox Homeostasis Perturbators Escaped from Early Lysosomes toward Amplified Sensitization of Tumor Cells and Photothermally Maneuvered Pyroptosis Therapy

Reactive oxygen species (ROS) hold great potential in tumor pyroptosis therapy, yet they are still limited by short species lifespan and limited diffusion distance. Inducing cells into a metastable state and then applying external energy can effectively trigger pyroptosis, but systemic sensitization still faces challenges, such as limited ROS content, rapid decay, and short treatment windows. Herein, a nanohybrid-based redox homeostasis-perturbator system was designed that synergistically induce early lysosomal escape, autophagy inhibition, and redox perturbation functions to effectively sensitize cells to address these challenges. Specifically, weakly alkaline layered double hydroxide nanosheets (LDH NSs) with pH-responsive degradation properties enabled early lysosomal escape within 4 h, releasing poly(L-dopa) nanoparticles for inducing catechol-quinone redox cycling in the cytoplasm. The intracellular ROS levels were systematically rebounded by 3-4 times in tumor cells and lasted for over 4 h. Subsequently induced lysosomal stress and Ca2+ signaling activation resulted in severe mitochondrial dysfunction, as well as a perilous metastable state. Thereby, sequential near-infrared light was applied to trigger amplified stress through a local photothermal conversion. This led to sufficiently high levels of cleaved caspase-1 and GSDMD activation (2.5-2.8-fold increment) and subsequent pyroptosis response. In addition, OH- released by LDH elevated pH to alleviate the limitation of glutathione depletion by quinones at acidic pH and inhibit protective autophagy. Largely secreted inflammatory factors (2.5-5.6-fold increment), efficient maturation of dendritic cells, and further immune stimulation were boosted for tumor inhibition as a consequence. This study offers a new paradigm and insights into the synergy of internal systematic cellular sensitization and sequential external energy treatment to achieve tumor suppression through pyroptosis.

TFEB-Mediated Pro-inflammatory Response in Murine Macrophages Induced by Acute Alpha7 Nicotinic Receptor Activation

Transcription factors TFEB and TFE3 are crucial for regulating autophagy, lysosomal biogenesis, and lipid metabolism, and have significant roles in macrophage function and innate immunity. The alpha7 nicotinic acetylcholine receptor (α7nAChR), a ligand-gated Ca 2+ channel known for its therapeutic potential in neurological and inflammatory disorders, has been implicated in modulating immune responses by modulating macrophage function. Stimulation of α7nAChR with chemical agonists has been claimed to activate TFEB in pancreatic acinar cells and neurons. However, the impact of α7nAChR activation on TFEB and TFE3 in macrophages remained unknown, posing an important question due to the potential implications for inflammation regulation. This study investigates the effects of acute α7nAChR activation on TFEB-mediated responses in murine macrophages using the specific agonist PNU-282987. We demonstrate that α7nAChR stimulation triggers TFEB nuclear translocation and lysosomal expansion. Surprisingly, PNU-282987 induces a broad pro-inflammatory gene signature without concomitant cytokine secretion, suggesting an uncoupling of gene expression from cytokine release. Mechanistically, TFEB activation requires the lysosomal Ca 2+ exporter MCOLN1 and the Ca 2+ -dependent phosphatase PPP3/calcineurin. Additionally, PNU-282987 elevates reactive oxygen species (ROS) levels, and ROS are involved in TFEB activation by PNU-282987. Notably, even with α7nAChR deletion, compensatory ROS-mediated TFEB activation persists, suggesting the involvement of additional nicotinic receptors. Our findings reveal a novel α7nAChR-TFEB signaling axis in macrophages, offer new insights into the cholinergic regulation of immune responses, establish a baseline for comparison with disease states, and identify potential therapeutic targets for modulating inflammation.

Calcium Deregulation in Neurodegeneration and Neuroinflammation in Parkinson's Disease: Role of Calcium-Storing Organelles and Sodium-Calcium Exchanger

Parkinson's disease (PD) is a progressive neurodegenerative disorder that lacks effective treatment strategies to halt or delay its progression. The homeostasis of Ca2+ ions is crucial for ensuring optimal cellular functions and survival, especially for neuronal cells. In the context of PD, the systems regulating cellular Ca2+ are compromised, leading to Ca2+-dependent synaptic dysfunction, impaired neuronal plasticity, and ultimately, neuronal loss. Recent research efforts directed toward understanding the pathology of PD have yielded significant insights, particularly highlighting the close relationship between Ca2+ dysregulation, neuroinflammation, and neurodegeneration. However, the precise mechanisms driving the selective loss of dopaminergic neurons in PD remain elusive. The disruption of Ca2+ homeostasis is a key factor, engaging various neurodegenerative and neuroinflammatory pathways and affecting intracellular organelles that store Ca2+. Specifically, impaired functioning of mitochondria, lysosomes, and the endoplasmic reticulum (ER) in Ca2+ metabolism is believed to contribute to the disease's pathophysiology. The Na+-Ca2+ exchanger (NCX) is considered an important key regulator of Ca2+ homeostasis in various cell types, including neurons, astrocytes, and microglia. Alterations in NCX activity are associated with neurodegenerative processes in different models of PD. In this review, we will explore the role of Ca2+ dysregulation and neuroinflammation as primary drivers of PD-related neurodegeneration, with an emphasis on the pivotal role of NCX in the pathology of PD. Consequently, NCXs and their interplay with intracellular organelles may emerge as potentially pivotal players in the mechanisms underlying PD neurodegeneration, providing a promising avenue for therapeutic intervention aimed at halting neurodegeneration.

MCOLN1/TRPML1 in the lysosome: a promising target for autophagy modulation in diverse diseases

MCOLN1/TRPML1 is a nonselective cationic channel specifically localized to the late endosome and lysosome. With its property of mediating the release of several divalent cations such as Ca2+, Zn2+ and Fe2+ from the lysosome to the cytosol, MCOLN1 plays a pivotal role in regulating a variety of cellular events including endocytosis, exocytosis, lysosomal biogenesis, lysosome reformation, and especially in Macroautophagy/autophagy. Autophagy is a highly conserved catabolic process that maintains cytoplasmic integrity by removing superfluous proteins and damaged organelles. Acting as the terminal compartments, lysosomes are crucial for the completion of the autophagy process. This review delves into the emerging role of MCOLN1 in controlling the autophagic process by regulating lysosomal ionic homeostasis, thereby governing the fundamental functions of lysosomes. Furthermore, this review summarizes the physiological relevance as well as molecular mechanisms through which MCOLN1 orchestrates autophagy, consequently influencing mitochondria turnover, cell apoptosis and migration. In addition, we have illustrated the implications of MCOLN1-regulated autophagy in the pathological process of cancer and myocardial ischemia-reperfusion (I/R) injury. In summary, given the involvement of MCOLN1-mediated autophagy in the pathogenesis of cancer and myocardial I/R injury, targeting MCOLN1 May provide clues for developing new therapeutic strategies for the treatment of these diseases. Exploring the regulation of MCOLN1-mediated autophagy in diverse diseases contexts will surely broaden our understanding of this pathway and offer its potential as a promising drug target.Abbreviation: CCCP:carbonyl cyanide3-chlorophenylhydrazone; CQ:chloroquine; HCQ: hydroxychloroquine;I/R: ischemia-reperfusion; MAP1LC3/LC3:microtubule associated protein 1 light chain 3; MCOLN1/TRPML1:mucolipin TRP cation channel 1; MLIV: mucolipidosis type IV; MTORC1:MTOR complex 1; ROS: reactive oxygenspecies; SQSTM1/p62: sequestosome 1.

Lysosomes drive the piecemeal removal of mitochondrial inner membrane

Mitochondrial membranes define distinct structural and functional compartments. Cristae of the inner mitochondrial membrane (IMM) function as independent bioenergetic units that undergo rapid and transient remodelling, but the significance of this compartmentalized organization is unknown1. Using super-resolution microscopy, here we show that cytosolic IMM vesicles, devoid of outer mitochondrial membrane or mitochondrial matrix, are formed during resting state. These vesicles derived from the IMM (VDIMs) are formed by IMM herniation through pores formed by voltage-dependent anion channel 1 in the outer mitochondrial membrane. Live-cell imaging showed that lysosomes in proximity to mitochondria engulfed the herniating IMM and, aided by the endosomal sorting complex required for transport machinery, led to the formation of VDIMs in a microautophagy-like process, sparing the remainder of the organelle. VDIM formation was enhanced in mitochondria undergoing oxidative stress, suggesting their potential role in maintenance of mitochondrial function. Furthermore, the formation of VDIMs required calcium release by the reactive oxygen species-activated, lysosomal calcium channel, transient receptor potential mucolipin 1, showing an interorganelle communication pathway for maintenance of mitochondrial homeostasis. Thus, IMM compartmentalization could allow for the selective removal of damaged IMM sections via VDIMs, which should protect mitochondria from localized injury. Our findings show a new pathway of intramitochondrial quality control.

Novel autophagy inducers by accelerating lysosomal clustering against Parkinson's disease

The autophagy-lysosome pathway plays an indispensable role in the protein quality control by degrading abnormal organelles and proteins including α-synuclein (αSyn) associated with the pathogenesis of Parkinson's disease (PD). However, the activation of this pathway is mainly by targeting lysosomal enzymic activity. Here, we focused on the autophagosome-lysosome fusion process around the microtubule-organizing center (MTOC) regulated by lysosomal positioning. Through high-throughput chemical screening, we identified 6 out of 1200 clinically approved drugs enabling the lysosomes to accumulate around the MTOC with autophagy flux enhancement. We further demonstrated that these compounds induce the lysosomal clustering through a JIP4-TRPML1-dependent mechanism. Among them, the lysosomal-clustering compound albendazole promoted the autophagy-dependent degradation of Triton-X-insoluble, proteasome inhibitor-induced aggregates. In a cellular PD model, albendazole boosted insoluble αSyn degradation. Our results revealed that lysosomal clustering can facilitate the breakdown of protein aggregates, suggesting that lysosome-clustering compounds may offer a promising therapeutic strategy against neurodegenerative diseases characterized by the presence of aggregate-prone proteins.

ER-to-lysosome Ca2+ refilling followed by K+ efflux-coupled store-operated Ca2+ entry in inflammasome activation and metabolic inflammation

We studied lysosomal Ca2+ in inflammasome. Lipopolysaccharide (LPS) + palmitic acid (PA) decreased lysosomal Ca2+ ([Ca2+]Lys) and increased [Ca2+]i through mitochondrial ROS, which was suppressed in Trpm2-KO macrophages. Inflammasome activation and metabolic inflammation in adipose tissue of high-fat diet (HFD)-fed mice were ameliorated by Trpm2 KO. ER→lysosome Ca2+ refilling occurred after lysosomal Ca2+ release whose blockade attenuated LPS + PA-induced inflammasome. Subsequently, store-operated Ca2+entry (SOCE) was activated whose inhibition suppressed inflammasome. SOCE was coupled with K+ efflux whose inhibition reduced ER Ca2+ content ([Ca2+]ER) and impaired [Ca2+]Lys recovery. LPS + PA activated KCa3.1 channel, a Ca2+-activated K+ channel. Inhibitors of KCa3.1 channel or Kcnn4 KO reduced [Ca2+]ER, attenuated increase of [Ca2+]i or inflammasome activation by LPS + PA, and ameliorated HFD-induced inflammasome or metabolic inflammation. Lysosomal Ca2+ release induced delayed JNK and ASC phosphorylation through CAMKII-ASK1. These results suggest a novel role of lysosomal Ca2+ release sustained by ER→lysosome Ca2+ refilling and K+ efflux through KCa3.1 channel in inflammasome activation and metabolic inflammation.