Lysosomes: fusion and function

Electrophysiological Techniques on the Study of Endolysosomal Ion Channels

Endolysosomal ion channels are a group of ion channel proteins that are functionally expressed on the membrane of endolysosomal vesicles. The electrophysiological properties of these ion channels in the intracellular organelle membrane cannot be observed using conventional electrophysiological techniques. This section compiles the different electrophysiological techniques utilized in recent years to study endolysosomal ion channels and describes their methodological characteristics, emphasizing the most widely used technique for whole endolysosome recordings to date. This includes the use of different pharmacological tools and genetic tools for the application of patch-clamping techniques for specific stages of endolysosomes, allowing the recording of ion channel activity in different organelles, such as recycling endosomes, early endosomes, late endosomes, and lysosomes. These electrophysiological techniques are not only cutting-edge technologies that help to investigate the biophysical properties of known and unknown intracellular ion channels but also help us to investigate the physiopathological role of these ion channels in the distribution of dynamic vesicles and to identify new therapeutic targets for precision medicine and drug screening.

Lysosomal Potassium Channels

Lysosomes are acidic membrane-bound organelles that use hydrolytic enzymes to break down material through pathways such as endocytosis, phagocytosis, mitophagy, and autophagy. To function properly, intralysosomal environments are strictly controlled by a set of integral membrane proteins such as ion channels and transporters. Potassium ion (K⁺) channels are a large and diverse family of membrane proteins that control K⁺ flux across both the plasma membrane and intracellular membranes. In the plasma membrane, they are essential in both excitable and non-excitable cells for the control of membrane potential and cell signaling. However, our understanding of intracellular K⁺ channels is very limited. In this review, we summarize the recent development in studies of K⁺ channels in the lysosome. We focus on their characterization, potential roles in maintaining lysosomal membrane potential and lysosomal function, and pathological implications.

Ca2+ and Annexins - Emerging Players for Sensing and Transferring Cholesterol and Phosphoinositides via Membrane Contact Sites

Maintaining lipid composition diversity in membranes from different organelles is critical for numerous cellular processes. However, many lipids are synthesized in the endoplasmic reticulum (ER) and require delivery to other organelles. In this scenario, formation of membrane contact sites (MCS) between neighbouring organelles has emerged as a novel non-vesicular lipid transport mechanism. Dissecting the molecular composition of MCS identified phosphoinositides (PIs), cholesterol, scaffolding/tethering proteins as well as Ca²⁺ and Ca²⁺-binding proteins contributing to MCS functioning. Compelling evidence now exists for the shuttling of PIs and cholesterol across MCS, affecting their concentrations in distinct membrane domains and diverse roles in membrane trafficking. Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) at the plasma membrane (PM) not only controls endo-/exocytic membrane dynamics but is also critical in autophagy. Cholesterol is highly concentrated at the PM and enriched in recycling endosomes and Golgi membranes. MCS-mediated cholesterol transfer is intensely researched, identifying MCS dysfunction or altered MCS partnerships to correlate with de-regulated cellular cholesterol homeostasis and pathologies. Annexins, a conserved family of Ca²⁺-dependent phospholipid binding proteins, contribute to tethering and untethering events at MCS. In this chapter, we will discuss how Ca²⁺ homeostasis and annexins in the endocytic compartment affect the sensing and transfer of cholesterol and PIs across MCS.

Oral Delivery of Nucleic Acid Therapies for Local and Systemic Action

Nucleic acid (NA) therapy has gained importance over the past decade due to its high degree of selectivity and minimal toxic effects over conventional drugs. Currently, intravenous (IV) or intramuscular (IM) formulations constitute majority of the marketed formulations containing nucleic acids. However, oral administration is traditionally preferred due to ease of administration as well as higher patient compliance. To leverage the benefits of oral delivery for NA therapy, the NA of interest must be delivered to the target site avoiding all degrading and inhibiting factors during its transition through the gastrointestinal tract. The oral route presents myriad of challenges to NA delivery, making formulation development challenging. Researchers in the last few decades have formulated various delivery systems to overcome such challenges and several reviews summarize and discuss these strategies in detail. However, there is a need to differentiate between the approaches based on target so that in future, delivery strategies can be developed according to the goal of the study and for efficient delivery to the desired site. The goal of this review is to summarize the mechanisms for target specific delivery, list and discuss the formulation strategies used for oral delivery of NA therapies and delineate the similarities and differences between local and systemic targeting oral delivery systems and current challenges.

A little less aggregation a little more replication: Viral manipulation of stress granules

Recent exciting studies have uncovered how membrane-less organelles, also known as biocondensates, are providing cells with rapid response pathways, allowing them to re-organize their cellular contents and adapt to stressful conditions. Their assembly is driven by the phase separation of their RNAs and intrinsically disordered protein components into condensed foci. Among these, stress granules (SGs) are dynamic cytoplasmic biocondensates that form in response to many stresses, including activation of the integrated stress response or viral infections. SGs sit at the crossroads between antiviral signaling and translation because they concentrate signaling proteins and components of the innate immune response, in addition to translation machinery and stalled mRNAs. Consequently, they have been proposed to contribute to antiviral activities, and therefore are targeted by viral countermeasures. Equally, SGs components can be commandeered by viruses for their own efficient replication. Phase separation processes are an important component of the viral life cycle, for example, driving the assembly of replication factories or inclusion bodies. Therefore, in this review, we will outline the recent understanding of this complex interplay and tug of war between viruses, SGs, and their components. This article is categorized under: RNA in Disease and Development > RNA in Disease Translation > Regulation RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.

From Lysosomal Storage Disorders to Parkinson's Disease - Challenges and Opportunities

Lysosomes are specialized organelles with an acidic pH that act as recycling hubs for intracellular and extracellular components. They harbour numerous different hydrolytic enzymes to degrade substrates like proteins, peptides, and glycolipids. Reduced catalytic activity of lysosomal enzymes can cause the accumulation of these substrates and loss of lysosomal integrity, resulting in lysosomal dysfunction and lysosomal storage disorders (LSDs). Post-mitotic cells, such as neurons, seem to be highly sensitive to damages induced by lysosomal dysfunction, thus LSDs often manifest with neurological symptoms. Interestingly, some LSDs and Parkinson's disease (PD) share common cellular pathomechanisms, suggesting convergence of aetiology of the two disease types. This is further underlined by genetic associations of several lysosomal genes involved in LSDs with PD. The increasing number of lysosome-associated genetic risk factors for PD makes it necessary to understand functions and interactions of lysosomal proteins/enzymes both in health and disease, thereby holding the potential to identify new therapeutic targets. In this review, we highlight genetic and mechanistic interactions between the complex lysosomal network, LSDs and PD, and elaborate on methodical challenges in lysosomal research.

Identifying Key Lysosome-Related Genes Associated with Drug-Resistant Breast Cancer Using Computational and Systems Biology Approach

Background

Drug resistance in breast cancer is an unsolved problem in treating patients. It has been recently discussed that lysosomes contribute to the invasion and angiogenesis of cancer cells. There is evidence that lysosomes can also cause multi-drug resistance. We analyzed this emerging concept in breast cancer through computational and systems biology approaches.

Objectives

We aimed to identify the key lysosome-related genes associated with drug-resistant breast cancer.

Methods

All genes contributing to the structure and function of lysosomes were inquired through the Human Lysosome Gene Database. The prioritized top 51 genes from the provided lists of Endeavour, ToppGene, and GPSy as prioritization tools were selected. All lysosomal genes and 12 breast cancer-related genes aligned to identify the most similar genes to breast cancer-related genes. Different centralities were applied to score each human protein to calculate the most central lysosomal genes in the human protein-protein interaction (PPI) network. Common genes were extracted from the results of the mentioned methods as a selected gene set. For Gene Ontology enrichment, the selected gene set was analyzed by WebGestalt, DAVID, and KOBAS. The PPI network was constructed via the STRING database. The PPI network was analyzed utilizing Cytoscape for topology network interaction and CytoHubba to extract hub genes.

Results

Based on biological studies, literature reviews, and comparing all mentioned analyzing methods, six genes were introduced as essential in breast cancer. This computational approach to all lysosome-related genes suggested that candidate genes include PRF1, TLR9, CLTC, GJA1, AP3B1, and RPTOR. The analyses of these six genes suggest that they may have a crucial role in breast cancer development, which has rarely been evaluated. These genes have a potential therapeutic implication for new drug discovery for chemo-resistant breast cancer.

Conclusions

The present work focused on all the functional and structural lysosome-related genes associated with breast cancer. It revealed the top six lysosome hub genes that might serve as therapeutic targets in drug-resistant breast cancer. Since these genes play a pivotal role in the structure and function of lysosomes, targeting them can effectively overcome drug resistance.

The phospholipid flippase ATP8B1 is required for lysosomal fusion in macrophages

ATP8B1 is a phospholipid flippase and member of the type 4 subfamily of P-type ATPases (P4-ATPase) subfamily. P4-ATPases catalyze the translocation of phospholipids across biological membranes, ensuring proper membrane asymmetry, which is crucial for membrane protein targeting and activity, vesicle biogenesis, and barrier function. Here we have investigated the role of ATP8B1 in the endolysosomal pathway in macrophages. Depletion of ATP8B1 led to delayed degradation of content in the phagocytic pathway and in overacidification of the endolysosomal system. Furthermore, ATP8B1 knockdown cells exhibited large multivesicular bodies filled with intraluminal vesicles. Similar phenotypes were observed in CRISPR-generated ATP8B1 knockout cells. Importantly, induction of autophagy led to accumulation of autophagosomes in ATP8B1 knockdown cells. Collectively, our results support a novel role for ATP8B1 in lysosomal fusion in macrophages, a process crucial in the terminal phase of endolysosomal degradation.

Lysosomal solute and water transport

Lysosomes mediate hydrolase-catalyzed macromolecule degradation to produce building block catabolites for reuse. Lysosome function requires an osmo-sensing machinery that regulates osmolytes (ions and organic solutes) and water flux. During hypoosmotic stress or when undigested materials accumulate, lysosomes become swollen and hypo-functional. As a membranous organelle filled with cargo macromolecules, catabolites, ions, and hydrolases, the lysosome must have mechanisms that regulate its shape and size while coordinating content exchange. In this review, we discussed the mechanisms that regulate lysosomal fusion and fission as well as swelling and condensation, with a focus on solute and water transport mechanisms across lysosomal membranes. Lysosomal H+, Na+, K+, Ca2+, and Cl- channels and transporters sense trafficking and osmotic cues to regulate both solute flux and membrane trafficking. We also provide perspectives on how lysosomes may adjust the volume of themselves, the cytosol, and the cytoplasm through the control of lysosomal solute and water transport.

TFEB acetylation promotes lysosome biogenesis and ameliorates Alzheimer's disease-relevant phenotypes in mice

Lysosomes are one of the major centers for regulating cargo degradation and protein quality control. Transcription factor EB (TFEB)-promoted lysosome biogenesis enhances lysosome-mediated degradation and alleviates neurodegenerative diseases, but the mechanisms underlying TFEB modification and activation are still poorly understood. Here, we report essential roles of TFEB acetylation in TFEB nuclear translocation and lysosome biogenesis, which are independent of TFEB dephosphorylation. By screening small molecules, we find that Trichostatin A (TSA), the pan-inhibitor of histone deacetylases (HDACs), promotes nuclear translocation of TFEB. TSA enhances the staining of cells by LysoTracker Red and increases the expression of lysosomal and autophagic genes. We identify four novel acetylated lysine residues in TFEB, which are important for TFEB nuclear translocation and lysosome biogenesis. We show that TFEB acetylation is regulated by HDACs (HDAC5, HDAC6, and HDAC9) and lysine acetyltransferases (KATs), including ELP3, CREBBP, and HAT1. During TSA-induced cytosol-to-nucleus translocation of TFEB, acetylation is independent of TFEB dephosphorylation, since the mTORC1- or GSK3β-related phosphorylation sites on TFEB are still phosphorylated. Administration of TSA to APP/PS1 mice increases the expression of lysosomal and autophagic genes in mouse brains and also improves memory. Accordingly, the β-amyloid plaque burden is decreased. These results show that the acetylation of TFEB, as a novel mechanism of TFEB activation, promotes lysosome biogenesis and alleviates the pathogenesis of Alzheimer's disease. Our results also suggest that HDAC inhibition can promote lysosome biogenesis, and this may be a potential therapeutic approach for the treatment of neurodegenerative diseases and disorders related to HDAC hyperactivation.

Fabry disease: Mechanism and therapeutics strategies

Fabry disease is a monogenic disease characterized by a deficiency or loss of the α-galactosidase A (GLA). The resulting impairment in lysosomal GLA enzymatic activity leads to the pathogenic accumulation of enzymatic substrate and, consequently, the progressive appearance of clinical symptoms in target organs, including the heart, kidney, and brain. However, the mechanisms involved in Fabry disease-mediated organ damage are largely ambiguous and poorly understood, which hinders the development of therapeutic strategies for the treatment of this disorder. Although currently available clinical approaches have shown some efficiency in the treatment of Fabry disease, they all exhibit limitations that need to be overcome. In this review, we first introduce current mechanistic knowledge of Fabry disease and discuss potential therapeutic strategies for its treatment. We then systemically summarize and discuss advances in research on therapeutic approaches, including enzyme replacement therapy (ERT), gene therapy, and chaperone therapy, as well as strategies targeting subcellular compartments, such as lysosomes, the endoplasmic reticulum, and the nucleus. Finally, the future development of potential therapeutic strategies is discussed based on the results of mechanistic studies and the limitations associated with these therapeutic approaches.

Cell-imaging studies of highly substituted oxazole derivatives as organelle targeting fluorophores (OTFPs)

The field of biomedical science has progressed enormously in the past decade. With the advent of newer diagnostic tools for imaging and detection, identification of root cause of a disease is now remarkably accurate and specific. Small organic fluorophores in these connections are in great demand currently for cellular organelle sensing and detecting, due to their non-invasiveness, excellent accuracy and bio-sensitivity. Small molecule fluorescence probes offer most potent area for biological sensing with diagnostic imaging ability. These organelle targetable fluorescent probes are produced through synthetic manipulations to get the desired, decent fluorescence properties. When a suitable organelle specific functional group is installed within these highly fluorescent scaffolds, then these molecules turn out to be as lysotracker, mitotracker and cytoplasm-stainer in mammalian cells with high efficiencies (high Pearson co-efficient factors). The present work demonstrated an environmentally benign (green) one-pot, sp³ C–H functionalization of highly substituted oxazole derivatives with excellent photophysical properties. These molecules were further modified by installing organelle specific targetable groups (sensors/detectors) which selectively localize in specific intra-cellular organelles.

Integration of transcriptomic and metabolomic reveals metabolic pathway alteration in earthworms (Eisenia fetida) under copper exposure

Copper is a trace element that necessary for plant growth in the soil. However, in recent years, due to human activities, the content of copper in soil exceeds the standard seriously, which is threatening the safety of soil animals, plants and even human beings. In this study, we investigated the effects and molecular mechanisms of 60 days long-term copper exposure on earthworms (Eisenia fetida) at 67.58 mg/kg, 168.96 mg/kg and 337.92 mg/kg concentration by using transcriptome and metabolomics. Transcriptome analysis showed that the expression of energy metabolism related genes (LDH, GYS, ATP6N, GAPDH, COX17), immune system related genes (E3.2.1.14) and detoxification related genes (UGT, CYP2U1, CYP1A1) were down-regulated, the expression of antioxidant system related genes (GCLC, HPGDS) were up-regulated in copper exposure experiment of earthworms. Similarly, metabolomics analysis revealed that the expression of energy metabolism related metabolites (Glucose-1-phosphate, Glucose-6-phosphate), TCA cycle related metabolites (fumaric acid, allantoic acid, malate, malic acid) were down-regulated, digestion and immune system related metabolites (Trehalose-6-phosphate) were up-regulated. Integrating transcriptome and metabolomics data, it was found that higher antioxidant capacity and accelerated TCA cycle metabolism may be an adaptive strategy for earthworms to adapt to long-term copper stress. Collectively, the results of this study will greatly contribute to incrementally understand the stress responses on copper exposure to earthworms and supply molecular level support for evaluating the environmental effects of copper on soil organisms.

A sensitive zinc probe operating via enhancement of excited-state intramolecular charge transfer

Novel highly sensitive fluorescent probes for zinc cations based on the diketopyrrolopyrrole scaffold were designed and synthesized. Large bathochromic shifts (≈80 nm) of fluorescence are observed when the Zn²⁺-recognition unit (di-(2-picolyl)amine) is bridged with the fluorophore possessing an additional pyridine unit able to participate in the coordination process. This effect originates from the dipolar architecture and the increasing electron-withdrawing properties of the diketopyrrolopyrrole core upon addition of the cation. The new, greenish-yellow emitting probes, which operate via modulation of intramolecular charge transfer, are very sensitive to the presence of Zn²⁺. Introduction of a morpholine unit in the diketopyrrolopyrrole structure induces a selective six-fold increase of the emission intensity upon zinc coordination. Importantly, the presence of other divalent biologically relevant metal cations has negligible effects and typically even at a 100-fold higher concentration of Mg²⁺/Zn²⁺, the effect is comparable. Computational studies rationalize the strong bathochromic shift upon Zn²⁺-complexation. Decorating the probes with the triphenylphosphonium cation and morpholine unit enables selective localization in the mitochondria and the lysosome of cardiac H9C2 cells, respectively.

Effects of Ultra-High Pressure on Endogenous Enzyme Activities, Protein Properties, and Quality Characteristics of Shrimp (Litopenaeus vannamei) during Iced Storage

The present study aimed to explore the effects of ultra-high pressure (UHP) on the cathepsin (B, D, H, and L) activities, protein oxidation, and degradation properties as well as quality characteristics of iced shrimp (Litopenaeus vannamei). Fresh shrimps were vacuum-packed, treated with UHP (100–500 MPa for 5 min), and stored at 0 °C for 15 days. The results showed that the L* (luminance), b* (yellowness), W (whiteness), ΔE (color difference), hardness, shear force, gumminess, chewiness, and resilience of shrimp were significantly improved by UHP treatment. Moreover, the contents of surface hydrophobicity, myofibril fragmentation index (MFI), trichloroacetic acid (TCA)-soluble peptides, carbonyl, dityrosine, and free sulfhydryl of myofibrillar protein (MP) were significantly promoted by UHP treatment. In addition, UHP (above 300 MPa) treatment enhanced the mitochondrial membrane permeability but inhibited the lysosomal membrane stability, and the cathepsin (B, D, H, and L) activities. UHP treatment notably inhibited the activities of cathepsins, delayed protein oxidation and degradation, as well as texture softening of shrimp during storage. Generally, UHP treatment at 300 MPa for 5 min effectively delayed the protein and quality deterioration caused by endogenous enzymes and prolonged the shelf life of shrimp by 8 days.

Discrimination of Cell Death Types with an Activatable Fluorescent Probe through Visualizing the Lysosome Morphology

Cell death plays a vital role in body development, maintenance of tissue function, and homeostasis. Accurate evaluation of cell death types is of great importance for pharmacological and pathological research. However, there is a lack of efficient fluorescent probes to discriminate various cell states. Here, we design and synthesize a novel activatable fluorescent probe PNE-Lyso to detect intracellular pH and hexosaminidases with two kinds of fluorescence signals. PNE-Lyso could distinguish dead cells from healthy cells based on a dual-color mode by targeting the lysosome and evaluating lysosomal hexosaminidase activity. Significantly, PNE-Lyso could also discriminate apoptotic and necrotic cells through visualizing lysosome morphology that is adjusted by the integrity of the lysosome membrane. Moreover, probe PNE-Lyso was successfully applied to investigate the drug-induced cell death process. To the best of our knowledge, this work is the first time cell death types have been distinguished based on a single fluorescent probe.

Protective Effect of Natural Medicinal Plants on Cardiomyocyte Injury in Heart Failure: Targeting the Dysregulation of Mitochondrial Homeostasis and Mitophagy

Heart failure occurs because of various cardiovascular pathologies, such as coronary artery disease or cardiorenal syndrome, eventually reaching end-stage disease. Various factors contribute to cardiac structural or functional changes that result in systolic or diastolic dysfunction. Several studies have confirmed that the key factor in heart failure progression is myocardial cell death, and mitophagy is the major mechanism regulating myocardial cell death in heart failure. The clinical mechanisms of heart failure are well understood in practice. However, the essential role of mitophagic regulation in heart failure has only recently received widespread attention. Receptor-mediated mitophagy is involved in various mitochondrial processes like oxidative stress injury, energy metabolism disorders, and calcium homeostasis, which are also the main causes of heart failure. Understanding of the diverse regulatory mechanisms in mitophagy and the complexity of its pathophysiology in heart failure remains incomplete. Related studies have found that various natural medicinal plants and active ingredients, such as flavonoids and saponins, can regulate mitophagy to a certain extent, improve myocardial function, and protect myocardial cells. This review comprehensively covers the relevant mechanisms of different types of mitophagy in regulating heart failure pathology and controlling mitochondrial adaptability to stress injury. Further, it explores the relationship between mitophagy and cardiac ejection dysfunction. Natural medicinal plant-targeted regulation strategies and scientific evidence on mitophagy were provided to elucidate current and potential strategies to apply mitophagy-targeted therapy for heart failure.

VAMP4 regulates insulin levels by targeting secretory granules to lysosomes

Insulin levels are essential for the maintenance of glucose homeostasis, and deviations lead to pathoglycemia or diabetes. However, the metabolic mechanism controlling insulin quantity and quality is poorly understood. In pancreatic β cells, insulin homeostasis and release are tightly governed by insulin secretory granule (ISG) trafficking, but the required regulators and mechanisms are largely unknown. Here, we identified that VAMP4 controlled the insulin levels in response to glucose challenge. VAMP4 deficiency led to increased blood insulin levels and hyperresponsiveness to glucose. In β cells, VAMP4 is packaged into immature ISGs (iISGs) at trans-Golgi networks and subsequently resorted to clathrin-coated vesicles during granule maturation. VAMP4-positive iISGs and resorted vesicles then fuse with lysosomes facilitated by a SNARE complex consisting of VAMP4, STX7, STX8, and VTI1B, which ensures the breakdown of excess (pro)insulin and obsolete materials and thus maintenance of intracellular insulin homeostasis. Thus, VAMP4 is a key factor regulating the insulin levels and a potential target for the treatment of diabetes.

Ligand-bound integrin αvβ6 internalisation and trafficking

The integrin αvβ6 is expressed at low levels in most normal healthy tissue but is very often upregulated in a disease context including cancer and fibrosis. Integrins use endocytosis and trafficking as a means of regulating their surface expression and thus their functions, however little is known of how this process is regulated in the context of αvβ6. As αvβ6 is a major target for the development of therapeutics in cancer and fibrosis, understanding these dynamics is critical in the development of αvβ6-targeted therapies. Following development of a flow cytometry-based assay to measure ligand (A20FMDV2 or LAP)-bound αvβ6 endocytosis, an siRNA screen was performed to identify which genes were responsible for internalising αvβ6. These data identified 15 genes (DNM2, CBLB, DNM3, CBL, EEA1, CLTC, ARFGAP3, CAV1, CYTH2, CAV3, CAV2, IQSEC1, AP2M1, TSG101) which significantly decreased endocytosis, predominantly within dynamin-dependent pathways. Inhibition of these dynamin-dependent pathways significantly reduced αvβ6-dependent migration (αvβ6-specific migration was 547 ± 128 under control conditions, reduced to 225 ± 73 with clathrin inhibition, and 280 ± 51 with caveolin inhibition). Colocalization studies of αvβ6 with endosome markers revealed that up to 6 h post-internalisation of ligand, αvβ6 remains in Rab11-positive endosomes in a perinuclear location, with no evidence of αvβ6 degradation up to 48 h post exposure to A20FMDV2. Additionally, 60% of ligand-bound αvβ6 was recycled back to the surface by 6 h. With studies ongoing using conjugated A20FMDV2 to therapeutically target αvβ6 in cancer and fibrosis, these data have important implications. Binding of A20FMDV2 seemingly removes much of the αvβ6 from the cell membrane, and upon its recycling, a large fraction appears to still be in the ligand-bound state. While these results are observed with A20FMDV2, these data will be of value in the design of αvβ6-specific therapeutics and potentially the types of therapeutic load.

Lysosome exocytosis is required for mitosis in mammalian cells

Mitosis, the accurate segregation of duplicated genetic material into what will become two new daughter cells, is accompanied by extensive membrane remodelling and membrane trafficking activities. Early in mitosis, adherent cells partially detach from the substratum, round up and their surface area decreases. This likely results from an endocytic uptake of plasma membrane material. As cells enter cytokinesis they re-adhere, flatten and exhibit an associated increase in surface area. The identity of the membrane donor for this phase of mitosis remains unclear. In this paper we demonstrate how lysosomes dynamically redistribute during mitosis and exocytose. Antagonism of lysosomal exocytosis by pharmacological and genetic approaches causes mitosis failure in a significant proportion of cells. We speculate that either lysosomal membrane or luminal content release, possibly both, are therefore required for normal mitosis progression. These findings are important as they reveal a new process required for successful cell division.

High-Resolution Low-Power Hyperspectral Line-Scan Imaging of Fast Cellular Dynamics Using Azo-Enhanced Raman Scattering Probes

Small-molecule Raman probes for cellular imaging have attracted great attention owing to their sharp peaks that are sensitive to environmental changes. The small cross section of molecular Raman scattering limits dynamic cellular Raman imaging to expensive and complex coherent approaches that acquire single-channel images and lose hyperspectral Raman information. We introduce a new method, dynamic azo-enhanced Raman imaging (DAERI), to couple the new class of azo-enhanced Raman probes with a high-speed line-scan Raman imaging system. DAERI achieved high-resolution low-power imaging of fast cellular dynamics resolved at ∼270 nm along the confocal direction, 75 μW/μm² and 3.5 s/frame. Based on the azo-enhanced Raman probes with characteristic signals 10²-10⁴ stronger than classic Raman labels, DAERI was not restricted to the cellular Raman-silent region as in prior work and enabled multiplex visualization of organelle motions and interactions. We anticipate DAERI to be a powerful tool for future studies in biophysics and cell biology.

Sodium alginate coating simultaneously increases the biosafety and immunotherapeutic activity of the cationic mRNA nanovaccine

The extraordinary advantages associated with mRNA vaccines, including their high efficiency, relatively low severity of side effects, and ease of manufacture, have enabled them to be a promising immunotherapy approach against various infectious diseases and cancers. Nevertheless, most mRNA delivery carriers have many disadvantages, such as high toxicity, poor biocompatibility, and low efficiency in vivo, which have hindered the widespread use of mRNA vaccines. To further characterize and solve these problems and develop a new type of safe and efficient mRNA delivery carrier, a negatively charged SA@DOTAP-mRNA nanovaccine was prepared in this study by coating DOTAP-mRNA with the natural anionic polymer sodium alginate (SA). Intriguingly, the transfection efficiency of SA@DOTAP-mRNA was significantly higher than that of DOTAP-mRNA, which was not due to the increase in cellular uptake but was associated with changes in the endocytosis pathway and the strong lysosome escape ability of SA@DOTAP-mRNA. In addition, we found that SA significantly increased the expression of LUC-mRNA in mice and achieved certain spleen targeting. Finally, we confirmed that SA@DOTAP-mRNA had a stronger antigen-presenting ability in E. G7-OVA tumor-bearing mice, dramatically inducing the proliferation of OVA-specific CLTs and ameliorating the antitumor effect. Therefore, we firmly believe that the coating strategy applied to cationic liposome/mRNA complexes is of potential research value in the field of mRNA delivery and has promising clinical application prospects.

Biodegradable particles for protein delivery: Estimation of the release kinetics inside cells

A methodology to quantify the efficiency of the protein loading and in-vitro delivery for biodegradable capsules with different architectures based on polyelectrolytes (dextran sulfate, poly-L-arginine and polyethylenimine) and SiO₂ was developed. The capsules were loaded with model proteins such as ovalbumin and green fluorescent protein (GFP), and the protein release profile inside cells (either macrophages or HeLa cells) after endocytosis was analysed. Both, protein loading and release kinetics were evaluated by analysing confocal laser scanning microscopy images using MatLab and CellProfiler software. Our results indicate that silica capsules showed the most efficient release of proteins as cargo molecules within 48 h, as compared to their polymeric counterparts. This developed method for the analysis of the intracellular cargo release kinetics from carrier structures could be used in the future for a better control of drug release profiles.

Mesenchymal Stem Cell-Derived Extracellular Vesicles as Idiopathic Pulmonary Fibrosis Microenvironment Targeted Delivery

Idiopathic pulmonary fibrosis (IPF) affects an increasing number of people globally, yet treatment options remain limited. At present, conventional treatments depending on drug therapy do not show an ideal effect in reversing the lung damage or extending the lives of IPF patients. In recent years, more and more attention has focused on extracellular vesicles (EVs) which show extraordinary therapeutic effects in inflammation, fibrosis disease, and tissue damage repair in many kinds of disease therapy. More importantly, EVs can be modified or used as a drug or cytokine delivery tool, targeting injury sites to enhance treatment efficiency. In light of this, the treatment strategy of mesenchymal stem cell-extracellular vesicles (MSC-EVs) targeting the pulmonary microenvironment for IPF provides a new idea for the treatment of IPF. In this review, we summarized the inflammation, immune dysregulation, and extracellular matrix microenvironment (ECM) disorders in the IPF microenvironment in order to reveal the treatment strategy of MSC-EVs targeting the pulmonary microenvironment for IPF.

Ubiquitin profiling of lysophagy identifies actin stabilizer CNN2 as a target of VCP/p97 and uncovers a link to HSPB1

Lysosomal membrane permeabilization (LMP) is an underlying feature of diverse conditions including neurodegeneration. Cells respond by extensive ubiquitylation of membrane-associated proteins for clearance of the organelle through lysophagy that is facilitated by the ubiquitin-directed AAA-ATPase VCP/p97. Here, we assessed the ubiquitylated proteome upon acute LMP and uncovered a large diversity of targets and lysophagy regulators. They include calponin-2 (CNN2) that, along with the Arp2/3 complex, translocates to damaged lysosomes and regulates actin filaments to drive phagophore formation. Importantly, CNN2 needs to be ubiquitylated during the process and removed by VCP/p97 for efficient lysophagy. Moreover, we identified the small heat shock protein HSPB1 that assists VCP/p97 in the extraction of CNN2 and show that other membrane regulators including SNAREs, PICALM, AGFG1, and ARL8B are ubiquitylated during lysophagy. Our data reveal a framework of how ubiquitylation and two effectors, VCP/p97 and HSPB1, cooperate to protect cells from the deleterious effects of LMP.

Fluorescent Probes Design Strategies for Imaging Mitochondria and Lysosomes

Modern cellular biology faces several major obstacles, such as the determination of the concentration of active sites corresponding to chemical substances. In recent years, the popular small-molecule fluorescent probes have completely changed the understanding of cellular biology through their high sensitivity toward specific substances in various organisms. Mitochondria and lysosomes are significant organelles in various organisms, and their interaction is closely related to the development of various diseases. The investigation of their structure and function has gathered tremendous attention from biologists. The advanced nanoscopic technologies have replaced the diffraction-limited conventional imaging techniques and have been developed to explore the unknown aspects of mitochondria and lysosomes with a sub-diffraction resolution. Recent progress in this field has yielded several excellent mitochondria- and lysosome-targeted fluorescent probes, some of which have demonstrated significant biological applications. Herein, we review studies that have been carried out to date and suggest future research directions that will harness the considerable potential of mitochondria- and lysosome-targeted fluorescent probes.

Intracellular Absolute Quantification of Oligonucleotide Therapeutics by NanoSIMS

Antisense oligonucleotide (ASO)-based therapeutics hold great potential for the treatment of a variety of diseases. Therefore, a better understanding of cellular delivery, uptake, and trafficking mechanisms of ASOs is highly important for early-stage drug discovery. In particular, understanding the biodistribution and quantifying the abundance of ASOs at the subcellular level are needed to fully characterize their activity. Here, we used a combination of electron microscopy and NanoSIMS to assess the subcellular concentrations of a ³⁴S-labeled GalNAc-ASO and a naked ASO in the organelles of primary human hepatocytes. We first cross-validated the method by including a ¹²⁷I-labeled ASO, finding that the absolute concentration of the lysosomal ASO using two independent labeling strategies gave matching results, demonstrating the strength of our approach. This work also describes the preparation of external standards for absolute quantification by NanoSIMS. For both the ³⁴S and ¹²⁷I approaches used for our quantification methodology, we established the limit of detection (5 and 2 μM, respectively) and the lower limit of quantification (14 and 5 μM, respectively).

Optical Visualization of Red-GQDs’ Organelles Distribution and Localization in Living Cells

Recently, there has been a rapidly expanding interest in a new nanomaterial, graphene quantum dots (GQDs), owing to its profound potential in various advanced applications. At present, the study of GQDs mainly focuses on the new synthesis methods and surface modification. However, revealing the intracellular distribution of GQDs is currently not available, limiting in-depth understanding of its biological regulatory mechanism. To fill up this gap, the visualization study of red fluorescent graphene quantum dots (Red-GQDs) is helpful to clarify their subcellular distribution and metabolism in living cells system. Here, in this study, two-photon laser confocal microscopy was used to deeply analyze the uptake and subcellular distribution of Red-GQDs by HeLa cells at different concentrations and times through visual observation and discussed the effect of Red-GQDs on the metabolic of HeLa cells. The results indicated that Red-GQDs could be well-absorbed by HeLa cells and further revealed the differential distribution of Red-GQDs in different organelles (lysosomes and mitochondria) in a time-dependent manner. In addition, we confirmed that Red-GQDs significantly affect cell biological functions. Low concentrations of Red-GQDs are related to the autophagy pathway of cells, and high concentrations of Red-GQDs can induce ferroptosis in cells and promote the secretion of cellular exosomes. In the present study, the distribution and metabolic pathways of Red-GQDs in the subcellular structure of cells were characterized in detail through visual analysis, which can bring positive reference for the application of Red-GQDs in the future.

Molecular design of a pathogen activated, self-assembling mechanopharmaceutical device

Weakly basic small molecule drugs like clofazimine can be used as building blocks for endowing cells with unnatural structural and functional elements. Here, we describe how clofazimine represents a first-in-class mechanopharmaceutical device, serving to construct inert, inactive and stimulus responsive drug depots within the endophagolysosomal compartment of cells of living organisms. Upon oral administration, clofazimine molecules self-assemble into stable, membrane-bound, crystal-like drug inclusions (CLDI) that accumulate within macrophages to form a "smart" biocompatible, pathogen activatable mechanopharmaceutical device. Upon perturbation of the mechanism maintaining pH and ion homeostasis of these CLDIs, the inert encapsulated drug precipitates are destabilized, releasing bioactive drug molecules into the cell and its surrounding. The resulting increase in clofazimine solubility activates this broad-spectrum antimicrobial, antiparasitic, antiviral or cytotoxic agent within the infected macrophage. We present a general, molecular design strategy for using clofazimine and other small molecule building blocks for the cytoplasmic construction of mechanopharmaceutical devices, aimed at rapid deployment during infectious disease outbreaks, for the purpose of pandemic prevention.

Amphiphilic Gold Nanoparticles: A Biomimetic Tool to Gain Mechanistic Insights into Peptide-Lipid Interactions

Functional peptides are now widely used in a myriad of biomedical and clinical contexts, from cancer therapy and tumor targeting to the treatment of bacterial and viral infections. Underlying this diverse range of applications are the non-specific interactions that can occur between peptides and cell membranes, which, in many contexts, result in spontaneous internalization of the peptide within cells by avoiding energy-driven endocytosis. For this to occur, the amphipathicity and surface structural flexibility of the peptides play a crucial role and can be regulated by the presence of specific molecular residues that give rise to precise molecular events. Nevertheless, most of the mechanistic details regulating the encounter between peptides and the membranes of bacterial or animal cells are still poorly understood, thus greatly limiting the biomimetic potential of these therapeutic molecules. In this arena, finely engineered nanomaterials-such as small amphiphilic gold nanoparticles (AuNPs) protected by a mixed thiol monolayer-can provide a powerful tool for mimicking and investigating the physicochemical processes underlying peptide-lipid interactions. Within this perspective, we present here a critical review of membrane effects induced by both amphiphilic AuNPs and well-known amphiphilic peptide families, such as cell-penetrating peptides and antimicrobial peptides. Our discussion is focused particularly on the effects provoked on widely studied model cell membranes, such as supported lipid bilayers and lipid vesicles. Remarkable similarities in the peptide or nanoparticle membrane behavior are critically analyzed. Overall, our work provides an overview of the use of amphiphilic AuNPs as a highly promising tailor-made model to decipher the molecular events behind non-specific peptide-lipid interactions and highlights the main affinities observed both theoretically and experimentally. The knowledge resulting from this biomimetic approach could pave the way for the design of synthetic peptides with tailored functionalities for next-generation biomedical applications, such as highly efficient intracellular delivery systems.

Universal Barcoding Predicts In Vivo ApoE-Independent Lipid Nanoparticle Delivery

To predict whether preclinical lipid nanoparticle (LNP) delivery will translate in humans, it is necessary to understand whether the mechanism used by LNPs to enter cells is conserved across species. In mice, non-human primates, and humans, LNPs deliver RNA to hepatocytes by adsorbing apolipoprotein E (ApoE), which binds low-density lipoprotein receptor (LDLR). A growing number of LNPs can deliver RNA to nonhepatocytes, suggesting that ApoE- and LDLR-independent interactions could affect LNP tropism. To evaluate this hypothesis, we developed a universal DNA barcoding system that quantifies how chemically distinct LNPs deliver small interfering RNA in any mouse model, including genetic knockouts. We quantified how 98 different LNPs targeted 11 cell types in wildtype, LDLR^-/-, very low-density lipoprotein receptor, and ApoE^-/- mice, studying how these genes, which traffic endogenous lipids, affected LNP delivery. These data identified a novel, stereopure LNP that targets Kupffer cells, endothelial cells, and hepatocytes in an ApoE-independent manner. These results suggest that non-ApoE interactions can affect the tropism of LNP-RNA drugs.

A Facile Fabrication of Lysosome-Targeting pH Fluorescent Nanosensor Based on PEGylated Polyester Block Copolymer

A novel lysosome-targeting PEGylated polyester-based fluorescent pH nanosensor is fabricated by the combination of ring-opening copolymerization (ROCOP), side-group modification and subsequent self-assembly. First, a key target amphiphilic copolymer carrier for rhodamine (Rh) pH indicator is synthesized in a facile manner by the ROCOP of phthalic anhydride with allyl glycidyl ether using mPEG-OH and t-BuP1/Et3B as the macroinitiator and binary catalyst, respectively. Subsequently, Rh moieties are covalently attached on the polymer chain with controllable grafting degree via an efficient thiol-ene click reaction. Concurrently, the effect of catalyst systems and reaction conditions on the catalytic copolymerization performance is presented, and the quantitative introduction of Rh is described in detail. Owing to its amphiphilic characteristics, the rhodamine-functionalized polyester-based block copolymer can self-assemble into micelles. With the covalent incorporation of Rh moieties, the as-formed micelles exhibit excellent absorption and fluorescence-responsive sensitivity and selectivity towards H+ in the presence of various metal cations. Moreover, the as-prepared micelles with favorable water dispersibility, good pH sensitivity and excellent biocompatibility also display appreciable cell-membrane permeability, staining ability and pH detection capability for lysosomes in living cells. This work provides a new strategy for the facile synthesis of novel biocompatible polymeric fluorescent pH nanosensors for the fluorescence imaging of lysosomal pH changes.

Aflatoxin B1 exposure disrupts organelle distribution in mouse oocytes

Aflatoxin B1 (AFB1) is a secondary metabolite produced by the fungus Aspergillus, which is ubiquitous in moldy grain products. Aflatoxin B1 has been reported to possess hepatotoxicity, renal toxicity, and reproductive toxicity. Previous studies have shown that AFB1 is toxic to mammalian oocytes. However, the potential toxicity of AFB1 on the organelles of mouse oocytes is unknown. In this study, we found that exposure to AFB1 significantly reduced mouse oocyte development capacity. Further analysis showed that the endoplasmic reticulum (ER) failed to accumulate around the spindle, and scattered in the cytoplasm under AFB1 exposure. Similar to the ER, the Golgi apparatus showed a uniform localization pattern following AFB1 treatment. In addition, we found that AFB1 exposure caused the condensation of lysosomes in the cytoplasm, presenting as a clustered or spindle peripheral-localization pattern, which indicated that protein modification, transport, and degradation were affected. Mitochondrial distribution was also altered by AFB1 treatment. In summary, our study showed that AFB1 exposure had toxic effects on the distribution of mouse oocyte organelles, which further led to a decline in oocyte quality.

Lysosomal Targeted Cyclometallic Iridium(Ⅲ) Salicylaldehyde-Coumarin Schiff Base Complexes and Anticancer Application

Natural coumarin derivatives and cyclometallic iridium (Ⅲ) (Ir^Ⅲ) complexes have attracted much attention in the field of anticancer. In this study, six coumarin-modified cyclometallic Ir^Ⅲ salicylaldehyde Schiff base complexes ([(ppy)₂Ir(O^N)]/[(ppy-CHO)₂Ir(O^N)]) were designed and synthesized. Compared with coumarin and Ir^Ⅲ complex monomers, target complexes exhibited favorable cytotoxic activity toward A549 and BEAS-2B cells. These complexes could induce extensive apoptosis of A549 cell (late apoptosis), which was represented by the disturbance of cell cycle (G₁-phase) and the accumulation of intracellular reactive oxygen species, exhibiting an anticancer mechanism of oxidation. With the help of suitable fluorescence of these complexes, no conflict with the probes, confocal detection confirmed that complexes showed an energy-dependent cellular uptake mechanism and triggered lysosome-mediated apoptosis in A549 cell line. Above all, our findings reveal the design of a lysosomal targeting cyclometallic Ir^Ⅲ Schiff base complexes and provide a new idea for the design of integrated drugs for diagnosis and treatment.

Role of Azole Drugs in Promoting Fungal Cell Autophagy Revealed by an NIR Fluorescence-Based Theranostic Probe

Autophagy, a widespread degradation system in eukaryotes, plays an important role in maintaining the homeostasis of the cellular environment and the recycling of substances. Optical probes for the tracking of autophagy can be used as an effective tool not only to visualize the autophagy process but also to study autophagy-targeted drugs. Various molecule probes for autophagy of cancer cells emerge but are very limited for that of fungal cells, resulting in the lack of research on antifungal drugs targeting autophagy. To address this issue, we report an azole NIR fluorescence-based theranostic probe AF-1 with antifungal activity that is sensitive to autophagy-associated pH. The unique design of this probe lies in the introduction of both the pH-sensitive fluorophore with a detection range matching the pH range of the autophagy process and the conserved core structural fragment of azole drugs, providing a strategy to investigate the relationship between antifungal drug action and autophagy. As such, AF-1 exhibited excellent spectral properties and was found to target and induce the autophagy of the fungal cell membrane while maintaining moderate antifungal activity. Of note, using this theranostic probe as both a dye and drug, the autophagy process of fungi was visualized in a ratiometric manner, revealing the role of azole antifungal drugs in promoting autophagy to induce fungal cell apoptosis.

Proteomic Response Revealed Signaling Pathways Involving in the Mechanism of Polymyxin B-Induced Melanogenesis

Polymyxin B is a last-line antibiotic for extensively resistant Gram-negative bacterial infection. Skin hyperpigmentation is a serious side effect induced by polymyxin B that severely compromises the psychological health and compliance of patients. The literature lacks mechanistic studies that explain how hyperpigmentation occurs, and this substantially hinders the development of intervention strategies and improved compliance. SK-MEL-2 cells were used for the polymyxin B-induced hyperpigmentation mechanism study. Melanin content and tyrosinase activity were measured after polymyxin B treatment. Tandem mass tag (TMT)-labeling quantitative proteomics was employed to investigate the response of SK-MEL-2 cells to polymyxin B treatment. Real-time quantitative PCR and Western blot were applied to validate the mRNA and protein levels of related genes and proteins. The melanin content and tyrosinase activity were significantly upregulated after polymyxin B treatment in SK-MEL-2 cells at 48 h and 72 h. Quantitative proteomics showed that 237 proteins were upregulated and 153 proteins were downregulated in the 48 h group, and 49 proteins were upregulated and 49 proteins were downregulated in the 72 h group. The differentially expressed proteins were involved in pathways such as lysosome, PI3K/Akt signaling pathway, and calcium signaling pathway. The upregulation of melanogenic enzymes and microphthalmia-associated transcription factor (MITF) was validated by qPCR and Western blot. Meanwhile, phosphorylation of PI3K, β-catenin, and cyclic-AMP response binding protein (CREB) in response to polymyxin B treatment was observed. The present study reveals the proteomic response of polymyxin B-induced melanogenesis in SK-MEL-2 cells for the first time. Signaling pathways, including melanin biosynthesis, PI3K/Akt, and calcium signaling pathways may be involved in the mechanism of melanogenesis. IMPORTANCE Polymyxin B-induced skin hyperpigmentation seriously affects the psychological health and compliance of patients. This study provides a proteomic clue to the mechanism at the cellular level for understanding polymyxin B-induced hyperpigmentation, contributing to a follow-up investigation of the corresponding PI3K/Akt signaling transduction pathway and calcium signaling pathway. The elucidation of its underlying mechanism is of great significance for patients' compliance improvement, intervention strategy, and new drug development.

Rational engineering of biomimetic flavylium fluorophores for regulating the lysosomal and mitochondrial localization behavior by pH-induced structure switch and application to fluorescence imaging

Mitochondria and lysosomes, as the important subcellular organelles, play vital roles in cell metabolism and physiopathology. However, there is still no general method to precisely regulate the lysosomal and mitochondrial localization behavior of fluorescent probes except by selecting specific targeting groups. Herein, we proposed a pH-induced structure switch (pHISS) strategy to solve this tricky puzzle. For the proof-of-concept, we have rationally designed and synthesized a series of cationic flavylium derivatives FL-1-9 with tunable pH-induced structure switch through adjusting the electron-donating ability of the substituents. As expected, the co-localization imaging experiments revealed that the lysosomal and mitochondrial localization behavior of FL-1-9 dyes is closely related to their pHISS ability. It is noteworthy that FL cationic dyes with strong electron-donors are not prone to pHISS and can be well enriched in mitochondria, while FL cationic dyes with weak electron-donors are highly susceptible to pHISS and display an unusual lysosome-targeting capability. This also provided a feasible strategy for lysosomal localization without basic groups and presented new application options for some flavylium dyes previously thought to be less stable. Furthermore, FL cationic dyes with medium electron-donor exhibit certain localization abilities both in mitochondria and lysosomes. Finally, through a detailed study of pH-induced structure switch and exploiting the pH inertia brought by the strong electron-donors, a novel NIR ratiometric fluorescent probe with large wavelength-shift was constructed for monitoring mitochondrial H₂S in living cells, tumor tissues and living mice, highlighting the value of the pHISS strategy in precisely regulating organelle targeting and constructing corresponding organelle targeting probes.

Lyso-IP: Uncovering Pathogenic Mechanisms of Lysosomal Dysfunction

Lysosomes are ubiquitous membrane-bound organelles found in all eukaryotic cells. Outside of their well-known degradative function, lysosomes are integral in maintaining cellular homeostasis. Growing evidence has shown that lysosomal dysfunction plays an important role not only in the rare group of lysosomal storage diseases but also in a host of others, including common neurodegenerative disorders, such as Alzheimer disease and Parkinson disease. New technological advances have significantly increased our ability to rapidly isolate lysosomes from cells in recent years. The development of the Lyso-IP approach and similar methods now allow for lysosomal purification within ten minutes. Multiple studies using the Lyso-IP approach have revealed novel insights into the pathogenic mechanisms of lysosomal disorders, including Niemann-Pick type C disease, showing the immense potential for this technique. Future applications of rapid lysosomal isolation techniques are likely to greatly enhance our understanding of lysosomal dysfunction in rare and common neurodegeneration causes.

Targeting calcium-mediated inter-organellar crosstalk in cardiac diseases

INTRODUCTION

Abnormal calcium signaling between organelles such as the sarcoplasmic reticulum (SR), mitochondria and lysosomes is a key feature of heart diseases. Calcium serves as a secondary messenger mediating inter-organellar crosstalk, essential for maintaining the cardiomyocyte function.

AREAS COVERED

This article examines the available literature related to calcium channels and transporters involved in inter-organellar calcium signaling. The SR calcium-release channels ryanodine receptor type-2 (RyR2) and inositol 1,4,5-trisphosphate receptor (IP₃R), and calcium-transporter SR/ER-ATPase 2a (SERCA2a) are illuminated. The roles of mitochondrial voltage-dependent anion channels (VDAC), the mitochondria Ca²⁺ uniporter complex (MCUC), and the lysosomal H⁺/Ca²⁺ exchanger, two pore channels (TPC), and transient receptor potential mucolipin (TRPML) are discussed. Furthermore, recent studies showing calcium-mediated crosstalk between the SR, mitochondria, and lysosomes as well as how this crosstalk is dysregulated in cardiac diseases are placed under the spotlight.

EXPERT OPINION

Enhanced SR calcium release via RyR2 and reduced SR reuptake via SERCA2a, increased VDAC and MCUC-mediated calcium uptake into mitochondria, and enhanced lysosomal calcium-release via lysosomal TPC and TRPML may all contribute to aberrant calcium homeostasis causing heart disease. While mechanisms of this crosstalk need to be studied further, interventions targeting these calcium channels or combinations thereof might represent a promising therapeutic strategy.