Lysosomes as dynamic regulators of cell and organismal homeostasis

Age-related driving mechanisms of retinal diseases and neuroprotection by transcription factor EB-targeted therapy

Retinal aging has been recognized as a significant risk factor for various retinal disorders, including diabetic retinopathy, age-related macular degeneration, and glaucoma, following a growing understanding of the molecular underpinnings of their development. This comprehensive review explores the mechanisms of retinal aging and investigates potential neuroprotective approaches, focusing on the activation of transcription factor EB. Recent meta-analyses have demonstrated promising outcomes of transcription factor EB-targeted strategies, such as exercise, calorie restriction, rapamycin, and metformin, in patients and animal models of these common retinal diseases. The review critically assesses the role of transcription factor EB in retinal biology during aging, its neuroprotective effects, and its therapeutic potential for retinal disorders. The impact of transcription factor EB on retinal aging is cell-specific, influencing metabolic reprogramming and energy homeostasis in retinal neurons through the regulation of mitochondrial quality control and nutrient-sensing pathways. In vascular endothelial cells, transcription factor EB controls important processes, including endothelial cell proliferation, endothelial tube formation, and nitric oxide levels, thereby influencing the inner blood-retinal barrier, angiogenesis, and retinal microvasculature. Additionally, transcription factor EB affects vascular smooth muscle cells, inhibiting vascular calcification and atherogenesis. In retinal pigment epithelial cells, transcription factor EB modulates functions such as autophagy, lysosomal dynamics, and clearance of the aging pigment lipofuscin, thereby promoting photoreceptor survival and regulating vascular endothelial growth factor A expression involved in neovascularization. These cell-specific functions of transcription factor EB significantly impact retinal aging mechanisms encompassing proteostasis, neuronal synapse plasticity, energy metabolism, microvasculature, and inflammation, ultimately offering protection against retinal aging and diseases. The review emphasizes transcription factor EB as a potential therapeutic target for retinal diseases. Therefore, it is imperative to obtain well-controlled direct experimental evidence to confirm the efficacy of transcription factor EB modulation in retinal diseases while minimizing its risk of adverse effects.

Coxiella burnetii effector CvpE maintains biogenesis of Coxiella-containing vacuoles by suppressing lysosome tubulation through binding PI(3)P and perturbing PIKfyve activity on lysosomes

Coxiella burnetii (C. burnetii) is the causative agent of Q fever, a zoonotic disease. Intracellular replication of C. burnetii requires the maturation of a phagolysosome-like compartment known as the replication permissive Coxiella-containing vacuole (CCV). Effector proteins secreted by the Dot/Icm secretion system are indispensable for maturation of a single large CCV by facilitating the fusion of promiscuous vesicles. However, the mechanisms of CCV maintenance and evasion of host cell clearance remain to be defined. Here, we show that C. burnetii secreted Coxiella vacuolar protein E (CvpE) contributes to CCV biogenesis by inducing lysosome-like vacuole (LLV) enlargement. LLV fission by tubulation and autolysosome degradation is impaired in CvpE-expressing cells. Subsequently, we found that CvpE suppresses lysosomal Ca2+ channel transient receptor potential channel mucolipin 1 (TRPML1) activity in an indirect manner, in which CvpE binds phosphatidylinositol 3-phosphate [PI(3)P] and perturbs PIKfyve activity in lysosomes. Finally, the agonist of TRPML1, ML-SA5, inhibits CCV biogenesis and C. burnetii replication. These results provide insight into the mechanisms of CCV maintenance by CvpE and suggest that the agonist of TRPML1 can be a novel potential treatment that does not rely on antibiotics for Q fever by enhancing Coxiella-containing vacuoles (CCVs) fission.

Signaling proteins in HSC fate determination are unequally segregated during asymmetric cell division

Hematopoietic stem cells (HSCs) continuously replenish mature blood cells with limited lifespans. To maintain the HSC compartment while ensuring output of differentiated cells, HSCs undergo asymmetric cell division (ACD), generating two daughter cells with different fates: one will proliferate and give rise to the differentiated cells' progeny, and one will return to quiescence to maintain the HSC compartment. A balance between MEK/ERK and mTORC1 pathways is needed to ensure HSC homeostasis. Here, we show that activation of these pathways is spatially segregated in premitotic HSCs and unequally inherited during ACD. A combination of genetic and chemical perturbations shows that an ERK-dependent mechanism determines the balance between pathways affecting polarity, proliferation, and metabolism, and thus determines the frequency of asymmetrically dividing HSCs. Our data identify druggable targets that modulate HSC fate determination at the level of asymmetric division.

Astrocytic uptake of posttranslationally modified amyloid-β leads to endolysosomal system disruption and induction of pro-inflammatory signaling

The disruption of astrocytic catabolic processes contributes to the impairment of amyloid-β (Aβ) clearance, neuroinflammatory signaling, and the loss of synaptic contacts in late-onset Alzheimer's disease (AD). While it is known that the posttranslational modifications of Aβ have significant implications on biophysical properties of the peptides, their consequences for clearance impairment are not well understood. It was previously shown that N-terminally pyroglutamylated Aβ3(pE)-42, a significant constituent of amyloid plaques, is efficiently taken up by astrocytes, leading to the release of pro-inflammatory cytokine tumor necrosis factor α and synapse loss. Here we report that Aβ3(pE)-42, but not Aβ1-42, gradually accumulates within the astrocytic endolysosomal system, disrupting this catabolic pathway and inducing the formation of heteromorphous vacuoles. This accumulation alters lysosomal kinetics, lysosome-dependent calcium signaling, and upregulates the lysosomal stress response. These changes correlate with the upregulation of glial fibrillary acidic protein (GFAP) and increased activity of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Treatment with a lysosomal protease inhibitor, E-64, rescues GFAP upregulation, NF-κB activation, and synapse loss, indicating that abnormal lysosomal protease activity is upstream of pro-inflammatory signaling and related synapse loss. Collectively, our data suggest that Aβ3(pE)-42-induced disruption of the astrocytic endolysosomal system leads to cytoplasmic leakage of lysosomal proteases, promoting pro-inflammatory signaling and synapse loss, hallmarks of AD-pathology.

Membrane atg8ylation in Canonical and Noncanonical Autophagy

Membrane atg8ylation is a homeostatic process responding to membrane remodeling and stress signals. Membranes are atg8ylated by mammalian ATG8 ubiquitin-like proteins through a ubiquitylation-like cascade. A model has recently been put forward which posits that atg8ylation of membranes is conceptually equivalent to ubiquitylation of proteins. Like ubiquitylation, membrane atg8ylation involves E1, E2 and E3 enzymes. The E3 ligases catalyze the final step of atg8ylation of aminophospholipids in membranes. Until recently, the only known E3 ligase for membrane atg8ylation was ATG16L1 in a noncovalent complex with the ATG12-ATG5 conjugate. ATG16L1 was first identified as a factor in canonical autophagy. During canonical autophagy, the ATG16L1-based E3 ligase complex includes WIPI2, which in turn recognizes phosphatidylinositiol 3-phosphate and directs atg8ylation of autophagic phagophores. As an alternative to WIPIs, binding of ATG16L1 to the proton pump V-ATPase guides atg8ylation of endolysosomal and phagosomal membranes in response to lumenal pH changes. Recently, a new E3 complex containing TECPR1 instead of ATG16L1, has been identified that responds to sphingomyelin's presence on the cytofacial side of perturbed endolysosomal membranes. In present review, we cover the principles of membrane atg8ylation, catalog its various presentations, and provide a perspective on the growing repertoire of E3 ligase complexes directing membrane atg8ylation at diverse locations.

JEV infection leads to dysfunction of lysosome by downregulating the expression of LAMP1 and LAMP2

Japanese Encephalitis Virus (JEV), the predominant cause of viral encephalitis in many Asian countries, affects approximately 68,000 people annually. Lysosomes are dynamic structures that regulate cellular metabolism by mediating lysosomal biogenesis and autophagy. Here, we showed that lysosome-associated membrane protein 1 (LAMP1) and LAMP2 were downregulated in cells after JEV infection, resulting in a decrease in the quantity of acidified lysosomes and impaired lysosomal catabolism. What's more, JEV nonstructural protein 4B plays key roles in the reduction of LAMP1/2 via the autophagy-lysosome pathway. JEV NS4B also promoted abnormal aggregation of SLA-DR, an important component of the swine MHC-II molecule family involved in antigen presentation and CD4+ cell activation initiation. Mechanistically, NS4B localized to the ER during JEV infection and interacted with GRP78, leading to the activation of ER stress-mediated autophagy. The 131-204 amino acid (aa) region of NS4B is essential for autophagy induction and LAMP1/2 reduction. In summary, our findings reveal a novel pathway by which JEV induces autophagy and disrupts lysosomal function.

A genetically-encoded fluorescence-based reporter to spatiotemporally investigate mannose-6-phosphate pathway

Maintenance of a pool of active lysosomes with acidic pH and degradative hydrolases is crucial for cell health. Abnormalities in lysosomal function are closely linked to diseases, such as lysosomal storage disorders, neurodegeneration, intracellular infections, and cancer among others. Emerging body of research suggests the malfunction of lysosomal hydrolase trafficking pathway to be a common denominator of several disease pathologies. However, available conventional tools to assess lysosomal hydrolase trafficking are insufficient and fail to provide a comprehensive picture about the trafficking flux and location of lysosomal hydrolases. To address some of the shortcomings, we designed a genetically-encoded fluorescent reporter containing a lysosomal hydrolase tandemly tagged with pH sensitive and insensitive fluorescent proteins, which can spatiotemporally trace the trafficking of lysosomal hydrolases. As a proof of principle, we demonstrate that the reporter can detect perturbations in hydrolase trafficking, that are induced by pharmacological manipulations and pathophysiological conditions like intracellular protein aggregates. This reporter can effectively serve as a probe for mapping the mechanistic intricacies of hydrolase trafficking pathway in health and disease and is a utilitarian tool to identify genetic and pharmacological modulators of this pathway, with potential therapeutic implications.

A dual-labeling fluorescent probe to track lysosomal polarity and endoplasmic reticulum dynamics during ferroptosis

A polarity-sensitive probe was developed to simultaneously label lysosomes and endoplasmic reticulum (ER) via its dansylamide and rhodamine fluorescence, respectively, enabling ratiometric polarity detection and stable dual-labeling. The fragmented ER network and increased lysosomal polarity during ferroptosis were revealed, which facilitates the understanding of ferroptotic mechanisms.

Pathological mechanisms of kidney disease in ageing

The kidney is a metabolically active organ that requires energy to drive processes such as tubular reabsorption and secretion, and shows a decline in function with advancing age. Various molecular mechanisms, including genomic instability, telomere attrition, inflammation, autophagy, mitochondrial function, and changes to the sirtuin and Klotho signalling pathways, are recognized regulators of individual lifespan and pivotal factors that govern kidney ageing. Thus, mechanisms that contribute to ageing not only dictate renal outcomes but also exert a substantial influence over life expectancy. Conversely, kidney dysfunction, in the context of chronic kidney disease (CKD), precipitates an expedited ageing trajectory in individuals, leading to premature ageing and a disconnect between biological and chronological age. As CKD advances, age-related manifestations such as frailty become increasingly conspicuous. Hence, the pursuit of healthy ageing necessitates not only the management of age-related complications but also a comprehensive understanding of the processes and markers that underlie systemic ageing. Here, we examine the hallmarks of ageing, focusing on the mechanisms by which they affect kidney health and contribute to premature organ ageing. We also review diagnostic methodologies and interventions for premature ageing, with special consideration given to the potential of emerging therapeutic avenues to target age-related kidney diseases.

Sulfiredoxin-1 promotes the growth of hepatocellular carcinoma by inhibiting TFEB-mediated autophagy and lysosome biogenesis

Advanced hepatocellular carcinoma (HCC) patients have poor prognosis. As an endogenous antioxidant enzyme involved in a variety of bioprocesses, sulfiredoxin-1 (SRXN1) plays an irreplaceable role in promoting the development of tumors. However, the role and working mechanism of SRXN1 in HCC remain unclear. In this study, we confirmed that SRXN1 promoted the cell proliferation of HCC at genetic and pharmacological level, respectively. Transcriptome sequencing analysis revealed SRXN1 knockdown had a significant effect on the expression of lysosome biogenesis related genes. Further experiments validated that lysosome biogenesis and autophagic flux were enhanced after SRXN1 inhibition and reduced as SRXN1 overexpression. Mechanism study revealed that ROS accumulation induced TFEB nuclear translocation, followed by increased autophagy. Following this rationale, the combination of SRXN1 inhibitor and sorafenib demonstrated noticeable synergistic antitumor effect through the boost of ROS both in vivo and in vitro. Taken together, SRXN1 could be a potential therapeutic target for HCC therapy.

Lysosome-targeted cyclometalated Ir(III) complexes as photosensitizers/photoredox catalysts for cancer therapy

A novel lysosome-targeted photosensitizer/photoredox catalyst based on cyclometalated Ir(III) complex IrL has been designed and synthesized, which exhibited excellent phosphorescence properties and the ability to generate single oxygen (1O2) and photocatalytically oxidize 1,4-dihydronicotinamide adenine dinucleotide (NADH) under light irradiation. Most importantly, the aforementioned activities are significantly enhanced due to protonation under acidic conditions, which makes them highly attractive in light-activated tumor therapy, especially for acidic lysosomes and tumor microenvironments. The photocytotoxicity of IrL and the mechanism of cell death have been investigated. Additionally, the tumor-killing ability of IrL under light irradiation was evaluated using a 4T1 tumor-bearing mouse model. This work provides a strategy for the development of lysosome-targeted photosensitizers/photoredox catalysts to overcome hypoxic tumors.

Longitudinal analysis of the lung proteome reveals persistent repair months after mild to moderate COVID-19

In order to assess homeostatic mechanisms in the lung after COVID-19, changes in the protein signature of bronchoalveolar lavage from 45 patients with mild to moderate disease at three phases (acute, recovery, and convalescent) are evaluated over a year. During the acute phase, inflamed and uninflamed phenotypes are characterized by the expression of tissue repair and host defense response molecules. With recovery, inflammatory and fibrogenic mediators decline and clinical symptoms abate. However, at 9 months, quantified radiographic abnormalities resolve in the majority of patients, and yet compared to healthy persons, all showed ongoing activation of cellular repair processes and depression of the renin-kallikrein-kinin, coagulation, and complement systems. This dissociation of prolonged reparative processes from symptom and radiographic resolution suggests that occult ongoing disruption of the lung proteome is underrecognized and may be relevant to recovery from other serious viral pneumonias.

High frequency electrical stimulation reduces α-synuclein levels and α-synuclein-mediated autophagy dysfunction

Accumulation of α-synuclein (α-Syn) has been implicated in proteasome and autophagy dysfunction in Parkinson's disease (PD). High frequency electrical stimulation (HFS) mimicking clinical parameters used for deep brain stimulation (DBS) in vitro or DBS in vivo in preclinical models of PD have been found to reduce levels of α-Syn and, in certain cases, provide possible neuroprotection. However, the mechanisms by which this reduction in α-Syn improves cellular dysfunction associated with α-Syn accumulation remains elusive. Using HFS parameters that recapitulate DBS in vitro, we found that HFS led to a reduction of mutant α-Syn and thereby limited proteasome and autophagy impairments due to α-Syn. Additionally, we observed that HFS modulates via the ATP6V0C subunit of V-ATPase and mitigates α-Syn mediated autophagic dysfunction. This study highlights a role for autophagy in reduction of α-Syn due to HFS which may prove to be a viable approach to decrease pathological protein accumulation in neurodegeneration.

Multiple mechanisms of aminoglycoside ototoxicity are distinguished by subcellular localization of action

Mechanosensory hair cells of the inner ears and lateral line of vertebrates display heightened vulnerability to environmental insult, with damage resulting in hearing and balance disorders. An important example is hair cell loss due to exposure to toxic agents including therapeutic drugs such as the aminoglycoside antibiotics such as neomycin and gentamicin and antineoplastic agents. We describe two distinct cellular pathways for aminoglycoside-induced hair cell death in zebrafish lateral line hair cells. Neomycin exposure results in death from acute exposure with most cells dying within 1 hour of exposure. By contrast, exposure to gentamicin results primarily in delayed hair cell death, taking up to 24 hours for maximal effect. Washout experiments demonstrate that delayed death does not require continuous exposure, demonstrating two mechanisms where downstream responses differ in their timing. Acute damage is associated with mitochondrial calcium fluxes and can be alleviated by the mitochondrially-targeted antioxidant mitoTEMPO, while delayed death is independent of these factors. Conversely delayed death is associated with lysosomal accumulation and is reduced by altering endolysosomal function, while acute death is not sensitive to lysosomal manipulations. These experiments reveal the complexity of responses of hair cells to closely related compounds, suggesting that intervention focusing on early events rather than specific death pathways may be a successful therapeutic strategy.

Inhibition of autophagy induced by tetrandrine promotes the accumulation of reactive oxygen species and sensitizes efficacy of tetrandrine in pancreatic cancer

Pancreatic cancer, characterized by its poor prognosis, exhibits a marked resistance to conventional chemotherapy and immunotherapy, underscoring the urgent need for more effective treatment modalities. In light of this, the present study is designed to assess the potential antineoplastic efficacy of a combined regimen involving tetrandrine, a plant-derived alkaloid, and autophagy inhibitors in the context of pancreatic cancer. Electron microscopy and immunoblots showed that tetrandrine promoted the formation of autophagosomes and the upregulation of LC3II and the downregulation of p62 expression, indicating that tetrandrine induced autophagy in pancreatic cancer cells. Western blot revealed that tetrandrine inhibited the phosphorylation of AKT and mTOR, as well as the expression of Bcl-2, while upregulating Beclin-1 expression. Moreover, tetrandrine promoted the transcription and protein expression of ATG7. Following the combination of autophagy inhibitors and tetrandrine, the apoptotic rate and cell death significantly increased in pancreatic cancer cells. Consistent results were obtained when ATG7 was silenced. Additionally, tetrandrine induced the generation of ROS, which was involved in the activation of autophagy and apoptosis. Further investigation revealed that upon autophagy inhibition, ROS accumulated in pancreatic cancer cells, resulting in decreased mitochondrial membrane potential and further induction of apoptosis. The results of treating subcutaneous xenograft tumors with a combination of tetrandrine and chloroquine validated that autophagy inhibition enhances the toxicity of tetrandrine against pancreatic cancer in vivo. Altogether, our study demonstrates that tetrandrine induces cytoprotective autophagy in pancreatic cancer cells. Inhibiting tetrandrine-induced autophagy promotes the accumulation of ROS and enhances its toxicity against pancreatic cancer.

Two-Step Enrichment Facilitates Background Reduction for Proteomic Analysis of Lysosomes

Lysosomes constitute the main degradative compartment of most mammalian cells and are involved in various cellular functions. Most of them are catalyzed by lysosomal proteins, which typically are low abundant, complicating their analysis by mass spectrometry-based proteomics. To increase analytical performance and to enable profiling of lysosomal content, lysosomes are often enriched. Two approaches have gained popularity in recent years, namely, superparamagnetic iron oxide nanoparticles (SPIONs) and immunoprecipitation from cells overexpressing a 3xHA-tagged version of TMEM192 (TMEM-IP). The effect of these approaches on the lysosomal proteome has not been investigated to date. We addressed this topic through a combination of both techniques and proteomic analysis of lysosome-enriched fractions. For SPIONs treatment, we identified altered cellular iron homeostasis and moderate changes of the lysosomal proteome. For overexpression of TMEM192, we observed more pronounced effects in lysosomal protein expression, especially for lysosomal membrane proteins and those involved in protein trafficking. Furthermore, we established a combined strategy based on the sequential enrichment of lysosomes with SPIONs and TMEM-IP. This enabled increased purity of lysosome-enriched fractions and, through TMEM-IP-based lysosome enrichment from SPIONs flow-through and eluate fractions, additional insights into the properties of individual approaches. All data are available via ProteomeXchange with PXD048696.

Emerging perspectives on precision therapy for Parkinson's disease: multidimensional evidence leading to a new breakthrough in personalized medicine

PD is a prevalent and progressive neurodegenerative disorder characterized by both motor and non-motor symptoms. Genes play a significant role in the onset and progression of the disease. While the complexity and pleiotropy of gene expression networks have posed challenges for gene-targeted therapies, numerous pathways of gene variant expression show promise as therapeutic targets in preclinical studies, with some already in clinical trials. With the recognition of the numerous genes and complex pathways that can influence PD, it may be possible to take a novel approach to choose a treatment for the condition. This approach would be based on the symptoms, genomics, and underlying mechanisms of the disease. We discuss the utilization of emerging genetic and pathological knowledge of PD patients to categorize the disease into subgroups. Our long-term objective is to generate new insights for the therapeutic approach to the disease, aiming to delay and treat it more effectively, and ultimately reduce the burden on individuals and society.

The ion channels of endomembranes

The endomembrane system consists of organellar membranes in the biosynthetic pathway [endoplasmic reticulum (ER), Golgi apparatus, and secretory vesicles] as well as those in the degradative pathway (early endosomes, macropinosomes, phagosomes, autophagosomes, late endosomes, and lysosomes). These endomembrane organelles/vesicles work together to synthesize, modify, package, transport, and degrade proteins, carbohydrates, and lipids, regulating the balance between cellular anabolism and catabolism. Large ion concentration gradients exist across endomembranes: Ca2+ gradients for most endomembrane organelles and H+ gradients for the acidic compartments. Ion (Na+, K+, H+, Ca2+, and Cl-) channels on the organellar membranes control ion flux in response to cellular cues, allowing rapid informational exchange between the cytosol and organelle lumen. Recent advances in organelle proteomics, organellar electrophysiology, and luminal and juxtaorganellar ion imaging have led to molecular identification and functional characterization of about two dozen endomembrane ion channels. For example, whereas IP3R1-3 channels mediate Ca2+ release from the ER in response to neurotransmitter and hormone stimulation, TRPML1-3 and TMEM175 channels mediate lysosomal Ca2+ and H+ release, respectively, in response to nutritional and trafficking cues. This review aims to summarize the current understanding of these endomembrane channels, with a focus on their subcellular localizations, ion permeation properties, gating mechanisms, cell biological functions, and disease relevance.

Hypomyelinated vps16 Mutant Zebrafish Exhibit Systemic and Neurodevelopmental Pathologies

Homotypic Fusion and Protein Sorting (HOPS) and Class C-core Vacuole/Endosome Tethering (CORVET) complexes regulate the correct fusion of endolysosomal bodies. Mutations in core proteins (VPS11, VPS16, VPS18, and VPS33) have been linked with multiple neurological disorders, including mucopolysaccharidosis (MPS), genetic leukoencephalopathy (gLE), and dystonia. Mutations in human Vacuolar Protein Sorting 16 (VPS16) have been associated with MPS and dystonia. In this study, we generated and characterized a zebrafish vps16(-/-) mutant line using immunohistochemical and behavioral approaches. The loss of Vps16 function caused multiple systemic defects, hypomyelination, and increased neuronal cell death. Behavioral analysis showed a progressive loss of visuomotor response and reduced motor response and habituation to acoustic/tap stimuli in mutants. Finally, using a novel multiple-round acoustic/tap stimuli test, mutants showed intermediate memory deficits. Together, these data demonstrate that zebrafish vps16(-/-) mutants show systemic defects, neurological and motor system pathologies, and cognitive impairment. This is the first study to report behavior abnormalities and memory deficiencies in a zebrafish vps16(-/-) mutant line. Finally, we conclude that the deficits observed in vps16(-/-) zebrafish mutants do not mimic pathologies associated with dystonia, but more align to abnormalities associated with MPS and gLE.

Lysosomal microautophagy: an emerging dimension in mammalian autophagy

Autophagy is a self-catabolic process through which cellular components are delivered to lysosomes for degradation. There are three types of autophagy, i.e., macroautophagy, chaperone-mediated autophagy (CMA), and microautophagy. In macroautophagy, a portion of the cytoplasm is wrapped by the autophagosome, which then fuses with lysosomes and delivers the engulfed cytoplasm for degradation. In CMA, the translocation of cytosolic substrates to the lysosomal lumen is directly across the limiting membrane of lysosomes. In microautophagy, lytic organelles, including endosomes or lysosomes, take up a portion of the cytoplasm directly. Although macroautophagy has been investigated extensively, microautophagy has received much less attention. Nonetheless, it has become evident that microautophagy plays a variety of cellular roles from yeast to mammals. Here we review the very recent updates of microautophagy. In particular, we focus on the feature of the degradative substrates and the molecular machinery that mediates microautophagy.

Oxidative stress induces extracellular vesicle release by upregulation of HEXB to facilitate tumour growth in experimental hepatocellular carcinoma

Extracellular vesicles (EVs) play a crucial role in triggering tumour-aggressive behaviours. However, the energetic process by which tumour cells produce EVs remains poorly understood. Here, we demonstrate the involvement of β-hexosaminidase B (HEXB) in mediating EV release in response to oxidative stress, thereby promoting the development of hepatocellular carcinoma (HCC). Mechanistically, reactive oxygen species (ROS) stimulate the nuclear translocation of transcription factor EB (TFEB), leading to the upregulation of both HEXB and its antisense lncRNA HEXB-AS. HEXB-AS can bind HEXB to form a protein/RNA complex, which elevates the protein stability of HEXB. The stabilized HEXB interacts with lysosome-associated membrane glycoprotein 1 (LAMP1), disrupting lysosome-multivesicular body (MVB) fusion, which protects EVs from degradation. Knockdown of HEXB efficiently inhibits EV release and curbs HCC growth both in vitro and in vivo. Moreover, targeting HEXB by M-31850 significantly inhibits HCC growth, especially when combined with GW4869, an inhibitor of exosome release. Our results underscore the critical role of HEXB as a modulator that promotes EV release during HCC development.

MFSD1 with its accessory subunit GLMP functions as a general dipeptide uniporter in lysosomes

The lysosomal degradation of macromolecules produces diverse small metabolites exported by specific transporters for reuse in biosynthetic pathways. Here we deorphanized the major facilitator superfamily domain containing 1 (MFSD1) protein, which forms a tight complex with the glycosylated lysosomal membrane protein (GLMP) in the lysosomal membrane. Untargeted metabolomics analysis of MFSD1-deficient mouse lysosomes revealed an increase in cationic dipeptides. Purified MFSD1 selectively bound diverse dipeptides, while electrophysiological, isotope tracer and fluorescence-based studies in Xenopus oocytes and proteoliposomes showed that MFSD1-GLMP acts as a uniporter for cationic, neutral and anionic dipeptides. Cryoelectron microscopy structure of the dipeptide-bound MFSD1-GLMP complex in outward-open conformation characterized the heterodimer interface and, in combination with molecular dynamics simulations, provided a structural basis for its selectivity towards diverse dipeptides. Together, our data identify MFSD1 as a general lysosomal dipeptide uniporter, providing an alternative route to recycle lysosomal proteolysis products when lysosomal amino acid exporters are overloaded.

Acetylated pelargonidin-3-O-glucoside alleviates hepatocyte lipid deposition through activating the AMPK-mediated lysosome-autophagy pathway and redox state

Nonalcoholic fatty liver disease (NAFLD) is a worldwide public health issue, but a widely accepted therapy is still lacking until now. Anthocyanins are natural flavonoid compounds that possess various bioactivities, but their applications are limited due to their low bioavailability and stability. Acylated anthocyanins are reported to show higher stability, whereas their effects on NAFLD are still unclear. Herein, pelargonidin-3-O-(6''-acetyl)-glucoside (Ace Pg3G) was found to dose-dependently reduce intracellular lipid droplets and triglycerides, and improve cellular oxidative stress that accompanied lipid deposition. Besides, Ace Pg3G was proved to activate AMPK phosphorylation, thus stimulating AMPK-mediated lysosome-autophagy pathway to eliminate overloaded lipid. Further study unveiled that Ace Pg3G regulated genes related to lipid metabolism downstream of AMPK to inhibit lipid synthesis and accelerate lipid oxidation. Overall, this study provided the first evidence, to our best knowledge, that Ace Pg3G ameliorated free fatty acid-induced lipid deposition in hepatocytes through regulating AMPK-mediated autophagy pathways and redox state.

Lysosomal dysfunction-derived autophagy impairment of gingival epithelial cells in diabetes-associated periodontitis with altered protein acetylation

Diabetes-associated periodontitis (DP) presents severe inflammation and resistance to periodontal conventional treatment, presenting a significant challenge in clinical management. In this study, we investigated the underlying mechanism driving the hyperinflammatory response in gingival epithelial cells (GECs) of DP patients. Our findings indicate that lysosomal dysfunction under high glucose conditions leads to the blockage of autophagy flux, exacerbating inflammatory response in GECs. Single-cell RNA sequencing and immunohistochemistry analyses of clinical gingival epithelia revealed dysregulation in the lysosome pathway characterized by reduced levels of lysosome-associated membrane glycoprotein 2 (LAMP2) and V-type proton ATPase 16 kDa proteolipid subunit c (ATP6V0C) in subjects with DP. In vitro stimulation of human gingival epithelial cells (HGECs) with a hyperglycemic microenvironment showed elevated release of proinflammatory cytokines, compromised lysosomal acidity and blocked autophagy. Moreover, HGECs with deficiency in ATP6V0C demonstrated impaired autophagy and heightened inflammatory response, mirroring the effects of high glucose stimulation. Proteomic analysis of acetylation modifications identified altered acetylation levels in 28 autophagy-lysosome pathway-related proteins and 37 sites in HGECs subjected to high glucose stimulation or siATP6V0C. Overall, our finding highlights the pivotal role of lysosome impairment in autophagy obstruction in DP and suggests a potential impact of altered acetylation of relevant proteins on the interplay between lysosome dysfunction and autophagy blockage. These insights may pave the way for the development of effective therapeutic strategies against DP.

A high-resolution phase-contrast microscopy system for label-free imaging in living cells

Cell biologists have long sought the ability to observe intracellular structures in living cells without labels. This study presents procedures to adjust a commercially available apodized phase-contrast (APC) microscopy system for better visualizing the dynamic behaviors of various subcellular organelles in living cells. By harnessing the versatility of this technique to capture sequential images, we could observe morphological changes in cellular geometry after virus infection in real time without probes or invasive staining. The tune-up APC microscopy system is a highly efficient platform for simultaneously observing the dynamic behaviors of diverse subcellular structures with exceptional resolution.

LAPTM4B counteracts ferroptosis via suppressing the ubiquitin-proteasome degradation of SLC7A11 in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related deaths worldwide, necessitating the identification of novel therapeutic targets. Lysosome Associated Protein Transmembrane 4B (LAPTM4B) is involved in biological processes critical to cancer progression, such as regulation of solute carrier transporter proteins and metabolic pathways, including mTORC1. However, the metabolic processes governed by LAPTM4B and its role in oncogenesis remain unknown. In this study, we conducted unbiased metabolomic screens to uncover the metabolic landscape regulated by LAPTM4B. We observed common metabolic changes in several knockout cell models suggesting of a role for LAPTM4B in suppressing ferroptosis. Through a series of cell-based assays and animal experiments, we demonstrate that LAPTM4B protects tumor cells from erastin-induced ferroptosis both in vitro and in vivo. Mechanistically, LAPTM4B suppresses ferroptosis by inhibiting NEDD4L/ZRANB1 mediated ubiquitination and subsequent proteasomal degradation of the cystine-glutamate antiporter SLC7A11. Furthermore, metabolomic profiling of cancer cells revealed that LAPTM4B knockout leads to a significant enrichment of ferroptosis and associated metabolic alterations. By integrating results from cellular assays, patient tissue samples, an animal model, and cancer databases, this study highlights the clinical relevance of the LAPTM4B-SLC7A11-ferroptosis signaling axis in NSCLC progression and identifies it as a potential target for the development of cancer therapeutics.

Disruptions in axonal lysosome transport and its contribution to neurological disease

Lysosomes are central to the maintenance of protein and organelle homeostasis in cells. Optimal lysosome function is particularly critical for neurons which are long-lived, non-dividing and highly polarized with specialized compartments such as axons and dendrites with distinct architecture, cargo, and turnover requirements. In recent years, there has been a growing appreciation for the role played by axonal lysosome transport in regulating neuronal development, its maintenance and functioning. Perturbations to optimal axonal lysosome abundance leading to either strong accumulations or dearth of lysosomes are both linked to altered neuronal health and functioning. In this review we highlight how two critical regulators of axonal lysosome transport and abundance, the small GTPase Arl8 and the adaptor protein JIP3, aid in maintaining axonal lysosome homeostasis and how alterations to their levels and activity could contribute to neurodevelopmental and neurodegenerative diseases.

Lysosomal Peptide Self-Assembly to Control Cell Behavior

Lysosomes are membrane-enclosed organelles that play key roles in degrading and recycling cellular debris, cellular signaling, and energy metabolism processes. Confinement of amphiphilic peptides in the lysosome to construct functional nanostructures through noncovalent interactions is an emerging approach to tune the homeostasis of lysosome. After briefly introducing the importance of lysosome and its functions, we discuss the advantages of lysosomal nanostructure formation for disease therapy. We next discuss the strategy for triggering the self-assembly of peptides in the lysosome, followed by a concise outlook of the future perspective about this emerging research direction.

Impaired cathepsin D in retinal pigment epithelium cells mediates Stargardt disease pathogenesis

Recessive Stargardt disease (STGD1) is an inherited juvenile maculopathy caused by mutations in the ABCA4 gene, for which there is no suitable treatment. Loss of functional ABCA4 in the retinal pigment epithelium (RPE) alone, without contribution from photoreceptor cells, was shown to induce STGD1 pathology. Here, we identified cathepsin D (CatD), the primary RPE lysosomal protease, as a key molecular player contributing to endo-lysosomal dysfunction in STGD1 using a newly developed "disease-in-a-dish" RPE model from confirmed STGD1 patients. Induced pluripotent stem cell (iPSC)-derived RPE originating from three STGD1 patients exhibited elevated lysosomal pH, as previously reported in Abca4-/- mice. CatD protein maturation and activity were impaired in RPE from STGD1 patients and Abca4-/- mice. Consequently, STGD1 RPE cells have reduced photoreceptor outer segment degradation and abnormal accumulation of α-synuclein, the natural substrate of CatD. Furthermore, dysfunctional ABCA4 in STGD1 RPE cells results in intracellular accumulation of autofluorescent material and phosphatidylethanolamine (PE). The altered distribution of PE associated with the internal membranes of STGD1 RPE cells presumably compromises LC3-associated phagocytosis, contributing to delayed endo-lysosomal degradation activity. Drug-mediated re-acidification of lysosomes in the RPE of STGD1 restores CatD functional activity and reduces the accumulation of immature CatD protein loads. This preclinical study validates the contribution of CatD deficiencies to STGD1 pathology and provides evidence for an efficacious therapeutic approach targeting RPE cells. Our findings support a cell-autonomous RPE-driven pathology, informing future research aimed at targeting RPE cells to treat ABCA4-mediated retinopathies.

Discovery and Optimization of Tetrahydroisoquinoline Derivatives To Enhance Lysosome Biogenesis as Preclinical Candidates for the Treatment of Alzheimer's Disease

More than 55 million individuals are suffering from Alzheimer's disease (AD), while the effective therapeutic strategies remain elusive. Our previous study identified a lysosome-enhancing lead compound LH2-051 with a tetrahydroisoquinoline scaffold through a novel dopamine transporter-cyclin-dependent kinase 9-transcription factor EB (DAT-CDK9-TFEB) regulation mechanism to promote TFEB activation and lysosome biogenesis. Here, we launched a comprehensive structure-activity relationship study for LH2-051, and 47 new derivatives were designed and synthesized, in which several compounds exhibited remarkable lysosome-enhancing activities. Notably, compounds 37 and 45 exhibited more favorable TFEB activation and lysosome biogenesis capabilities, good safety profiles, and excellent pharmacokinetic profiles with high brain penetration. Further investigations demonstrated that both compounds significantly enhance the clearance of Aβ aggregates and ameliorate the impairment of learning, memory, and cognition in APP/PS1 mice. Overall, these results indicated that compounds 37 and 45 are promising preclinical drug candidates for the treatment of AD.

Design and Synthesis of ESIPT-Based Imidazole Derivatives for Cell Imaging

Excited-state intramolecular proton transfer (ESIPT)-based fluorescent molecules offer several exciting applications and are utilized most frequently as a cell imaging agent. Because of this, four distinct imidazole derivatives with ESIPT emission have been synthesized, and their fluorescence characteristics have been assessed in a variety of settings. Measurements using fluorescence spectroscopy have shown a promising candidate for cell staining, and potential candidate was specifically investigated for cell imaging uses in HT-29, MDA-MB-231, and HaCaT. Cytotoxicity of candidate molecule (1d) was analyzed using HT-29 and HaCaT cell lines, and at a dosage of 160 μM, HT-29 and HaCaT cell lines showed no signs of important cell toxicity. When spectroscopically measured, compound 1d showed no fluorescence ability in phosphate-buffered saline (PBS) solution. However, after 8 h of incubation in several cell lines, excellent fluorescence characteristics were seen in the green and red filters.

A mild increase in nutrient signaling to mTORC1 in mice leads to parenchymal damage, myeloid inflammation and shortened lifespan

The mechanistic target of rapamycin complex 1 controls cellular anabolism in response to growth factor signaling and to nutrient sufficiency signaled through the Rag GTPases. Inhibition of mTOR reproducibly extends longevity across eukaryotes. Here we report that mice that endogenously express active mutant variants of RagC exhibit multiple features of parenchymal damage that include senescence, expression of inflammatory molecules, increased myeloid inflammation with extensive features of inflammaging and a ~30% reduction in lifespan. Through bone marrow transplantation experiments, we show that myeloid cells are abnormally activated by signals emanating from dysfunctional RagC-mutant parenchyma, causing neutrophil extravasation that inflicts additional inflammatory damage. Therapeutic suppression of myeloid inflammation in aged RagC-mutant mice attenuates parenchymal damage and extends survival. Together, our findings link mildly increased nutrient signaling to limited lifespan in mammals, and support a two-component process of parenchymal damage and myeloid inflammation that together precipitate a time-dependent organ deterioration that limits longevity.

Ferroptosis: principles and significance in health and disease

Ferroptosis, an iron-dependent form of cell death characterized by uncontrolled lipid peroxidation, is governed by molecular networks involving diverse molecules and organelles. Since its recognition as a non-apoptotic cell death pathway in 2012, ferroptosis has emerged as a crucial mechanism in numerous physiological and pathological contexts, leading to significant therapeutic advancements across a wide range of diseases. This review summarizes the fundamental molecular mechanisms and regulatory pathways underlying ferroptosis, including both GPX4-dependent and -independent antioxidant mechanisms. Additionally, we examine the involvement of ferroptosis in various pathological conditions, including cancer, neurodegenerative diseases, sepsis, ischemia-reperfusion injury, autoimmune disorders, and metabolic disorders. Specifically, we explore the role of ferroptosis in response to chemotherapy, radiotherapy, immunotherapy, nanotherapy, and targeted therapy. Furthermore, we discuss pharmacological strategies for modulating ferroptosis and potential biomarkers for monitoring this process. Lastly, we elucidate the interplay between ferroptosis and other forms of regulated cell death. Such insights hold promise for advancing our understanding of ferroptosis in the context of human health and disease.

Expanding the horizons of targeted protein degradation: A non-small molecule perspective

Targeted protein degradation (TPD) represented by proteolysis targeting chimeras (PROTACs) marks a significant stride in drug discovery. A plethora of innovative technologies inspired by PROTAC have not only revolutionized the landscape of TPD but have the potential to unlock functionalities beyond degradation. Non-small-molecule-based approaches play an irreplaceable role in this field. A wide variety of agents spanning a broad chemical spectrum, including peptides, nucleic acids, antibodies, and even vaccines, which not only prove instrumental in overcoming the constraints of conventional small molecule entities but also provided rapidly renewing paradigms. Herein we summarize the burgeoning non-small molecule technological platforms inspired by PROTACs, including three major trajectories, to provide insights for the design strategies based on novel paradigms.

Arrhythmogenesis in Fabry Disease

PURPOSE OF REVIEW

Fabry Disease (FD) is a rare lysosomal storage disorder characterised by multiorgan accumulation of glycosphingolipid due to deficiency in the enzyme α-galactosidase A. Cardiac sphingolipid accumulation triggers various types of arrhythmias, predominantly ventricular arrhythmia, bradyarrhythmia, and atrial fibrillation. Arrhythmia is likely the primary contributor to FD mortality with sudden cardiac death, the most frequent cardiac mode of death. Traditionally FD was seen as a storage cardiomyopathy triggering left ventricular hypertrophy, diastolic dysfunction, and ultimately, systolic dysfunction in advanced disease. The purpose of this review is to outline the current evidence exploring novel mechanisms underlying the arrhythmia substrate.

RECENT FINDINGS

There is growing evidence that FD cardiomyopathy is a primary arrhythmic disease with each stage of cardiomyopathy (accumulation, hypertrophy, inflammation, and fibrosis) contributing to the arrhythmia substrate via various intracellular, extracellular, and environmental mechanisms. It is therefore important to understand how these mechanisms contribute to an individual's risk of arrhythmia in FD. In this review, we outline the epidemiology of arrhythmia, pathophysiology of arrhythmogenesis, risk stratification, and cardiac therapy in FD. We explore how advances in conventional cardiac investigations performed in FD patients including 12-lead electrocardiography, transthoracic echocardiography, and cardiac magnetic resonance imaging have enabled early detection of pro-arrhythmic substrate. This has allowed for appropriate risk stratification of FD patients. This paves the way for future work exploring the development of therapeutic initiatives and risk prediction models to reduce the burden of arrhythmia.

WHAMM functions in kidney reabsorption and polymerizes actin to promote autophagosomal membrane closure and cargo sequestration

The actin cytoskeleton is essential for many functions of eukaryotic cells, but the factors that nucleate actin assembly are not well understood at the organismal level or in the context of disease. To explore the function of the actin nucleation factor WHAMM in mice, we examined how Whamm inactivation impacts kidney physiology and cellular proteostasis. We show that male WHAMM knockout mice excrete elevated levels of albumin, glucose, phosphate, and amino acids, and display structural abnormalities of the kidney proximal tubule, suggesting that WHAMM activity is important for nutrient reabsorption. In kidney tissue, the loss of WHAMM results in the accumulation of the lipidated autophagosomal membrane protein LC3, indicating an alteration in autophagy. In mouse fibroblasts and human proximal tubule cells, WHAMM and its binding partner the Arp2/3 complex control autophagic membrane closure and cargo receptor recruitment. These results reveal a role for WHAMM-mediated actin assembly in maintaining kidney function and promoting proper autophagosome membrane remodeling.

Messenger RNA transport on lysosomal vesicles maintains axonal mitochondrial homeostasis and prevents axonal degeneration

In neurons, RNA granules are transported along the axon for local translation away from the soma. Recent studies indicate that some of this transport involves hitchhiking of RNA granules on lysosome-related vesicles. In the present study, we leveraged the ability to prevent transport of these vesicles into the axon by knockout of the lysosome-kinesin adaptor BLOC-one-related complex (BORC) to identify a subset of axonal mRNAs that depend on lysosome-related vesicles for transport. We found that BORC knockout causes depletion of a large group of axonal mRNAs mainly encoding ribosomal and mitochondrial/oxidative phosphorylation proteins. This depletion results in mitochondrial defects and eventually leads to axonal degeneration in human induced pluripotent stem cell (iPSC)-derived and mouse neurons. Pathway analyses of the depleted mRNAs revealed a mechanistic connection of BORC deficiency with common neurodegenerative disorders. These results demonstrate that mRNA transport on lysosome-related vesicles is critical for the maintenance of axonal homeostasis and that its failure causes axonal degeneration.

Next-generation neonicotinoid: The impact of cycloxaprid on the crustacean decapod Penaeus vannamei

Cycloxaprid, a new neonicotinoid pesticide, poses ecological risks, particularly in aquatic environments, due to its unique action and environmental dispersal. This study investigated the ecotoxicological effects of various concentrations of cycloxaprid on Penaeus vannamei over 28 days. High cycloxaprid levels significantly altered shrimp physiology, as shown by changes in the hepatosomatic index and fattening. Indicators of oxidative stress, such as increased serum hemocyanin, respiratory burst, and nitric oxide, as well as decreased phenol oxidase activity, were observed. Additionally, elevated activities of lactate dehydrogenase, succinate dehydrogenase, and isocitrate dehydrogenase indicated disrupted energy metabolism in the hepatopancreas. Notably, analyses of the nervous system revealed marked disturbances in neural signaling, as evidenced by elevated acetylcholine, octopamine, and acetylcholinesterase levels. Transcriptomic analysis highlighted significant effects on gene expression and metabolic processes in the hepatopancreas and nervous system. This study demonstrated that cycloxaprid disrupts neural signaling and oxidative balance in P. vannamei, potentially affecting its growth, and provides key insights into its biochemical and transcriptomic toxicity in aquatic systems.

From cells to subcellular organelles: Next-generation cancer therapy based on peptide self-assembly

Due to the editability, functionality, and excellent biocompatibility of peptides, in situ self-assembly of peptides in cells is a powerful strategy for biomedical applications. Subcellular organelle targeting of peptides assemblies enables more precise drug delivery, enhances selectivity to disease cells, and mitigates drug resistance, providing an effective strategy for disease diagnosis and therapy. This reviewer first introduces the triggering conditions, morphological changes, and intracellular locations of self-assembling peptides. Then, the functions of peptide assemblies are summarized, followed by a comprehensive understanding of the interactions between peptide assemblies and subcellular organelles. Finally, we provide a brief outlook and the remaining challenges in this field.

Lysosome-Related Genes and RNF19B as Prognostic Markers for Survival and Immunotherapy Efficacy in Hepatocellular Carcinoma

INTRODUCTION

Hepatocellular carcinoma (HCC) poses a considerable worldwide health concern due to its associated high risk of death. The heterogeneity of HCC poses challenges in developing practical risk stratification tools and identifying prognostic markers for personalized targeted treatments. Recently, lysosomes were shown to be crucial contributors to numerous cellular activities, including tumor initiation and immune response regulation. We aimed to construct a reliable prognostic signature based on lysosome-related genes and determine its association with the immune microenvironment.

METHODS

We comprehensively analyzed lysosome-related genes in HCC to investigate their influence on patient survival and the tumor immune microenvironment. A prognostic signature comprising 14 genes associated with lysosomes was created to estimate the survival outcomes of individuals with HCC. In addition, we verified the prognostic importance of Ring Finger Protein 19B (RNF19B) in patients with HCC through multiplex immunohistochemistry analysis.

RESULTS

Our constructed lysosome-related prediction model could significantly discriminate between HCC patients with good and poor survival outcomes ( P < 0.05). We also found that elevated RNF19B expression was linked to unfavorable prognostic outcomes and showed a connection with specific clinicopathological characteristics. Moreover, it was observed that RNF19B could facilitate the transformation of macrophages into M2-polarized macrophages and showed a significant positive correlation with PD-1 and CTLA-4.

DISCUSSION

In summary, our study proposes that the expression of lysosome-related genes is associated with the immune microenvironment, serving as a predictor for HCC patient survival. Meanwhile, RNF19B was identified as a novel prognostic marker for predicting overall survival and immunotherapy effects in patients with HCC.

Mitochondria-lysosome-extracellular vesicles axis and nanotheranostics in neurodegenerative diseases

The intricate functional interactions between mitochondria and lysosomes play a pivotal role in maintaining cellular homeostasis and proper cellular functions. This dynamic interplay involves the exchange of molecules and signaling, impacting cellular metabolism, mitophagy, organellar dynamics, and cellular responses to stress. Dysregulation of these processes has been implicated in various neurodegenerative diseases. Additionally, mitochondrial-lysosomal crosstalk regulates the exosome release in neurons and glial cells. Under stress conditions, neurons and glial cells exhibit mitochondrial dysfunction and a fragmented network, which further leads to lysosomal dysfunction, thereby inhibiting autophagic flux and enhancing exosome release. This comprehensive review synthesizes current knowledge on mitochondrial regulation of cell death, organelle dynamics, and vesicle trafficking, emphasizing their significant contributions to neurodegenerative diseases. Furthermore, we explore the emerging field of nanomedicine in the management of neurodegenerative diseases. The review provides readers with an insightful overview of nano strategies that are currently advancing the mitochondrial-lysosome-extracellular vesicle axis as a therapeutic approach for mitigating neurodegenerative diseases.

PNPO-PLP axis senses prolonged hypoxia in macrophages by regulating lysosomal activity

Oxygen is critical for all metazoan organisms on the earth and impacts various biological processes in physiological and pathological conditions. While oxygen-sensing systems inducing acute hypoxic responses, including the hypoxia-inducible factor pathway, have been identified, those operating in prolonged hypoxia remain to be elucidated. Here we show that pyridoxine 5'-phosphate oxidase (PNPO), which catalyses bioactivation of vitamin B6, serves as an oxygen sensor and regulates lysosomal activity in macrophages. Decreased PNPO activity under prolonged hypoxia reduced an active form of vitamin B6, pyridoxal 5'-phosphate (PLP), and inhibited lysosomal acidification, which in macrophages led to iron dysregulation, TET2 protein loss and delayed resolution of the inflammatory response. Among PLP-dependent metabolism, supersulfide synthesis was suppressed in prolonged hypoxia, resulting in the lysosomal inhibition and consequent proinflammatory phenotypes of macrophages. The PNPO-PLP axis creates a distinct layer of oxygen sensing that gradually shuts down PLP-dependent metabolism in response to prolonged oxygen deprivation.

Sharing is caring: TMEM165 a Golgi calcium importer used by the lysosome

Calcium is a crucial second messenger in the cell that is stored in organelles including lysosomes. Proteins that facilitate calcium entry to the lysosome were unknown. A recent report by Zajac et al. identified TMEM165 as a proton-activated calcium importer on the lysosome, thus discovering a key player in subcellular calcium homeostasis.

Methods for investigating STAT3 regulation of lysosomal function in mammary epithelial cells

The transcription factor STAT3 is activated by multiple cytokines and other extrinsic factors. It plays a key role in immune and inflammatory responses and, when dysregulated, in tumourigenesis. STAT3 is also an indispensable mediator of the cell death process that occurs during post-lactational regression of the mammary gland, one of the most dramatic examples of physiological cell death in adult mammals. During this involution of the gland, STAT3 powerfully enhances the lysosomal system to efficiently remove superfluous milk-producing mammary epithelial cells via a lysosomal-mediated programmed cell death pathway. The lysosome is a membrane-enclosed  cytoplasmic organelle that digests and recycles cellular waste, with an important role as a signalling centre that monitors cellular metabolism. Here, we describe key strategies for investigating the role of STAT3 in regulating lysosomal function using a mammary epithelial cell culture model system. These include protocols for lysosome enrichment and enzyme activity assays, in addition to microscopic analyses of the vesicular compartment in cell lines. Collectively, these approaches provide the tools to investigate multiple aspects of lysosome biogenesis and function, and to define both direct and indirect roles for STAT3.

VPS13C regulates phospho-Rab10-mediated lysosomal function in human dopaminergic neurons

Loss-of-function mutations in VPS13C are linked to early-onset Parkinson's disease (PD). While VPS13C has been previously studied in non-neuronal cells, the neuronal role of VPS13C in disease-relevant human dopaminergic neurons has not been elucidated. Using live-cell microscopy, we investigated the role of VPS13C in regulating lysosomal dynamics and function in human iPSC-derived dopaminergic neurons. Loss of VPS13C in dopaminergic neurons disrupts lysosomal morphology and dynamics with increased inter-lysosomal contacts, leading to impaired lysosomal motility and cellular distribution, as well as defective lysosomal hydrolytic activity and acidification. We identified Rab10 as a phospho-dependent interactor of VPS13C on lysosomes and observed a decreased phospho-Rab10-mediated lysosomal stress response upon loss of VPS13C. These findings highlight an important role of VPS13C in regulating lysosomal homeostasis in human dopaminergic neurons and suggest that disruptions in Rab10-mediated lysosomal stress response contribute to disease pathogenesis in VPS13C-linked PD.

Targeting lysosomal quality control as a therapeutic strategy against aging and diseases

Previously, lysosomes were primarily referred to as the digestive organelles and recycling centers within cells. Recent discoveries have expanded the lysosomal functional scope and revealed their critical roles in nutrient sensing, epigenetic regulation, plasma membrane repair, lipid transport, ion homeostasis, and cellular stress response. Lysosomal dysfunction is also found to be associated with aging and several diseases. Therefore, function of macroautophagy, a lysosome-dependent intracellular degradation system, has been identified as one of the updated twelve hallmarks of aging. In this review, we begin by introducing the concept of lysosomal quality control (LQC), which is a cellular machinery that maintains the number, morphology, and function of lysosomes through different processes such as lysosomal biogenesis, reformation, fission, fusion, turnover, lysophagy, exocytosis, and membrane permeabilization and repair. Next, we summarize the results from studies reporting the association between LQC dysregulation and aging/various disorders. Subsequently, we explore the emerging therapeutic strategies that target distinct aspects of LQC for treating diseases and combatting aging. Lastly, we underscore the existing knowledge gap and propose potential avenues for future research.

Biallelic BORCS8 variants cause an infantile-onset neurodegenerative disorder with altered lysosome dynamics

BLOC-one-related complex (BORC) is a multiprotein complex composed of eight subunits named BORCS1-8. BORC associates with the cytosolic face of lysosomes, where it sequentially recruits the small GTPase ARL8 and kinesin-1 and -3 microtubule motors to promote anterograde transport of lysosomes toward the peripheral cytoplasm in non-neuronal cells and the distal axon in neurons. The physiological and pathological importance of BORC in humans, however, remains to be determined. Here, we report the identification of compound heterozygous variants [missense c.85T>C (p.Ser29Pro) and frameshift c.71-75dupTGGCC (p.Asn26Trpfs*51)] and homozygous variants [missense c.196A>C (p.Thr66Pro) and c.124T>C (p.Ser42Pro)] in BORCS8 in five children with a severe early-infantile neurodegenerative disorder from three unrelated families. The children exhibit global developmental delay, severe-to-profound intellectual disability, hypotonia, limb spasticity, muscle wasting, dysmorphic facies, optic atrophy, leuko-axonopathy with hypomyelination, and neurodegenerative features with prevalent supratentorial involvement. Cellular studies using a heterologous transfection system show that the BORCS8 missense variants p.Ser29Pro, p.Ser42Pro and p.Thr66Pro are expressed at normal levels but exhibit reduced assembly with other BORC subunits and reduced ability to drive lysosome distribution toward the cell periphery. The BORCS8 frameshift variant p.Asn26Trpfs*51, on the other hand, is expressed at lower levels and is completely incapable of assembling with other BORC subunits and promoting lysosome distribution toward the cell periphery. Therefore, all the BORCS8 variants are partial or total loss-of-function alleles and are thus likely pathogenic. Knockout of the orthologous borcs8 in zebrafish causes decreased brain and eye size, neuromuscular anomalies and impaired locomotion, recapitulating some of the key traits of the human disease. These findings thus identify BORCS8 as a novel genetic locus for an early-infantile neurodegenerative disorder and highlight the critical importance of BORC and lysosome dynamics for the development and function of the central nervous system.

An Alkaline Nanocage Continuously Activates Inflammasomes by Disrupting Multiorganelle Homeostasis for Efficient Pyroptosis

Pyroptosis has garnered increasing attention because of its ability to trigger robust antitumor immunity. Pyroptosis is initiated by the activation of inflammasomes, which are regulated by various organelles. The collaboration among organelles offers several protective mechanisms to prevent activation of the inflammasome, thereby limiting the induction of efficient pyroptosis. Herein, a multiorganelle homeostasis disruptor (denoted BLL) is constructed by encapsulating liposomes and bortezomib (BTZ) within a layered double hydroxide (LDH) nanocage to continuously activate inflammasomes for inducing efficient pyroptosis. In lysosomes, the negatively charged liposomes are released to recruit the NLRP3 inflammasomes through electrostatic interactions. ER stress is induced by BTZ to enhance the activation of the NLRP3 inflammasome. Meanwhile, the BLL nanocage exhibited H+-scavenging ability due to the weak alkalinity of LDH, thus disrupting the homeostasis of the lysosome and alleviating the degradation of the NLRP3 inflammasome by lysosomal-associated autophagy. Our results suggest that the BLL nanocage induces homeostatic imbalance in various organelles and efficient pyroptosis. We hope this work can provide new insights into the design of an efficient pyroptosis inducer by disrupting the homeostatic balance of multiple organelles and promote the development of novel antineoplastic platforms.

Evaluation of hepatic AMPK, mTORC1, and autophagy-lysosomal pathway in cows with mild or moderate fatty liver

The aim of the present study was to investigate the activity of AMPK and mTORC1 as well as TFEB transcriptional activity and autophagy-lysosomal function in the liver of dairy cows with mild fatty liver (FL) and cows with moderate FL. Liver and blood samples were collected from healthy dairy cows (n = 10; hepatic triglyceride content <1% wet weight) and cows with mild FL (n = 10; 1% ≤ hepatic triglyceride content < 5% wet weight) or moderate FL (n = 10; 5% ≤ hepatic triglyceride content < 10% wet weight) that had a similar number of lactations (median = 3, range = 2-4) and days in milk (median = 6 d, range = 3-9). Blood parameters were determined using a Hitachi 3130 autoanalyzer with commercially available kits. Protein and mRNA abundances were determined using western blotting and quantitative real-time PCR, respectively. Activities of calcineurin and β-N-acetylglucosaminidase were measured with commercial assay kits. Data were analyzed using one-way ANOVA with subsequent Bonferroni correction. Blood concentrations of glucose were lower in moderate FL cows (3.03 ± 0.21 mM) than in healthy (3.71 ± 0.14 mM) and mild FL cows (3.76 ± 0.14 mM). Blood concentrations of β-hydroxybutyrate (BHB, 1.37 ± 0.15 mM in mild FL, 1.88 ± 0.17 mM in moderate FL) and free fatty acids (FFA, 0.69 ± 0.05 mM in mild FL, 0.96 ± 0.09 mM in moderate FL) were greater in FL cows than in healthy cows (BHB, 0.76 ± 0.12 mM; FFA, 0.42 ± 0.04 mM). Compared with healthy cows, phosphorylation of AMPK was greater and phosphorylation of its downstream target acetyl-CoA carboxylase 1 was lower in cows with mild and moderate FL. Phosphorylation of mTOR was lower in cows with mild FL compared with healthy cows. In cows with moderate FL, phosphorylation of mTOR and its downstream effectors was greater than in healthy cows and cows with mild FL. The mRNA abundance of TFEB was downregulated in cows with moderate FL compared with healthy cows and mild FL cows. In mild FL cows, the mRNA and protein abundances of TFEB were greater than in healthy cows. Compared with healthy cows, the mRNA abundances of autophagy markers sequestosome-1 and microtubule-associated protein 1 light chain 3-II, and the protein and mRNA abundances of lysosome-associated membrane protein 1 and cathepsin D were increased in mild FL cows but decreased in moderate FL cows. Compared with healthy cows, the mRNA abundance of mucolipin 1 and activities of β-N-acetylglucosaminidase and calcineurin were higher in cows with mild FL but lower in cows with moderate FL. These data demonstrate that hepatic AMPK signaling pathway, TFEB transcriptional activity, and autophagy-lysosomal function are increased in dairy cows with mild FL; the hepatic mTORC1 signaling pathway is inhibited in mild FL cows but activated in moderate FL cows; and activities of AMPK and TFEB as well as autophagy-lysosomal function are impaired in moderate FL cows.

Iridoid glycosides from Morinda officinalis induce lysosomal biogenesis and promote autophagic flux to attenuate oxidative stress

Morinda officinalis is a traditional Chinese tonic herb, and have been used in the treatment of multiple diseases. Here, three iridoid glycosides isolated from M. officinalis were evaluated for their roles in the autophagy-lysosomal pathway. All three iridoid glycosides could induce TFEB/TFE3-mediated lysosomal biogenesis and trigger autophagy. Interestingly, they promoted the nuclear import of TFEB/TFE3 without affecting their nuclear export, suggesting their role in the maintenance of lysosomal homeostasis. The results from this study shed light on the identification of autophagy activators from M. officinalis and provide a basis for developing them in the treatment of oxidative stress-involved diseases.