Organelle homeostasis principles: How organelle quality control and inter-organelle crosstalk promote cell survival

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

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

Self-Assembly of DNA Nanoflares in Mitochondria for Sensitive In Situ Imaging of Cancer Markers

Real-time monitoring of cancer markers at the organelle level offers an effective approach to understanding the mechanisms of cancer generation. Herein, we have developed a sensitive in situ imaging method for human apurinic/apyrimidinic endonuclease 1 (APE1), a cancer biomarker that regulates mitochondrial function by triggering a chain reaction within mitochondria to form highly efficient DNA nanoflares through palindrome-driven assembly (PDA). To deliver the DNA sequences with palindromes for the chain reaction, we prepared triphenylphosphine (TPP)-modified polymeric nanoparticles specifically targeting mitochondria. The presence of APE1 in mitochondria triggered the PDA, leading to the in situ assembly of DNA nanoflares and yielding highly sensitive imaging of APE1. This strategy demonstrates the high capability of combined chain reactions for the real-time monitoring of cancer markers within organelles.

Deciphering melanophagy: role of the PTK2-ITCH-MLANA-OPTN cascade on melanophagy in melanocytes

Melanosomes play a pivotal role in skin color and photoprotection. In contrast to the well-elucidated pathway of melanosome biogenesis, the process of melanosome degradation, referred to as melanophagy, is largely unexplored. Previously, we discovered that 3,4,5-trimethoxycinnamate thymol ester (TCTE) effectively inhibits skin pigmentation by activating melanophagy. In this study, we discovered a new regulatory signaling cascade that controls melanophagy in TCTE-treated melanocytes. ITCH (itchy E3 ubiquitin protein ligase) facilitates ubiquitination of the melanosome membrane protein MLANA (melan-A) during TCTE-induced melanophagy. This ubiquitinated MLANA is then recognized by an autophagy receptor protein, OPTN (optineurin). Additionally, a phospho-kinase antibody array revealed that TCTE activates PTK2 (protein tyrosine kinase 2), which phosphorylates ITCH, enhancing the ubiquitination of MLANA. Furthermore, inhibition of either PTK2 or ITCH disrupts the ubiquitination of MLANA and the MLANA-OPTN interaction in TCTE-treated cells. Taken together, our findings highlight the critical role of the PTK2-ITCH-MLANA-OPTN cascade in orchestrating melanophagy progression.Abbreviations: α-MSH: alpha-melanocyte-stimulating hormone; dichlone: 2,3-dichloro-1,4-naphthoquinone; ITCH: itchy E3 ubiquitin protein ligase; MITF: melanocyte inducing transcription factor; MLANA: melan-A; NBR1: NBR1 autophagy cargo receptor; OPTN: optineurin; PINK1: PTEN induced kinase 1; PTK2: protein tyrosine kinase 2; SQSTM1/p62: sequestosome 1; TCTE: 3,4,5-trimethoxycinnamate thymol ester; TPC2: two pore segment channel 2; VDAC1: voltage dependent anion channel 1.

Inter-organelle communication dynamically orchestrates juvenile hormone biosynthesis and female reproduction

Inter-organelle communication coordinates cellular homeostasis and function. Juvenile hormone (JH) is produced in the corpora allata (CA) and acts as a gonadotrophic hormone in most insects. Using transcriptomic, biochemical, molecular, and genetic analyses, here we investigated the underlying mechanism of how inter-organelle communication dynamically orchestrates JH biosynthesis and female reproduction in the American cockroach, Periplaneta americana. The extracellular stimuli insulin and allatostatin act through their membrane receptors and antagonistically regulate RyR-mediated Ca2+ release from the endoplasmic reticulum in CA cells. Ca2+-activated CaMKII stimulates energy metabolism in the mitochondria partially via SLC25A6, and induces the expression of JH biosynthetic genes HMGR, Jhamt, and Cyp15a1 through activating transcription factor CREB, which recruits CBP for histone acetylation in the nucleus. Additionally, mitochondria interact with CREB-CBP through mitonuclear communication to regulate JH biosynthesis. From the perspective of inter-organelle communication, this comprehensive study significantly advanced our understanding of hormone biosynthesis and reproductive biology in insects.

Bionanoparticles with In Situ Nitric Oxide Release for Precise Modulation of ER-TRPV1 Ion Channels in Multimodal Killing of Glioblastoma

Glioblastoma (GBM) with highly immunosuppressive tumor microenvironment is a significant factor contributing to its treatment resistance and low survival rate. The activation of the transient receptor potential vanilloid 1 (TRPV1) ion channel, which is overexpressed on the endoplasmic reticulum (ER) of GBM cells, governs the control of multi-organelle stress pathway branches to inhibit GBM expansion. Precise modulation of ER-TRPV1 is considered an effective strategy for inhibition of GBM. As an effective intracellular and extracellular second messenger, nitric oxide (•NO) activates the TRPV1 ion channel through nitrosylation of cysteine residues. However, the short lifespan and limited effective range of •NO makes it challenging to achieve precise regulation of ER-TRPV1. Herein, a biomimetic upconversion nanoassembly (M-UCN-T) is constructed, which encapsulates an organic •NO donor and is coated with homologous tumor-targeting cell membrane and ER-targeting peptide. In response to near-infrared light and glutathione, M-UCN-T releases •NO in situ to activate the ER-TRPV1 ion channels. This study developed a •NO-targeted release nanoplatform with stepwise targeting functions, which allow for the precise modulation of ER-TPRV1 in GBM through in situ release of •NO. This approach induces multi-organelle stress signaling pathways, ultimately resulting in multi-modal killing of tumor cells.

Organellar quality control crosstalk in aging-related disease: Innovation to pave the way

Organellar homeostasis and crosstalks within a cell have emerged as essential regulatory and determining factors for the survival and functions of cells. In response to various stimuli, cells can activate the organellar quality control systems (QCS) to maintain homeostasis. Numerous studies have demonstrated that dysfunction of QCS can lead to various aging-related diseases such as neurodegenerative, pulmonary, cardiometabolic diseases and cancers. However, the interplay between QCS and their potential role in these diseases are poorly understood. In this review, we present an overview of the current findings of QCS and their crosstalk, encompassing mitochondria, endoplasmic reticulum, Golgi apparatus, ribosomes, peroxisomes, lipid droplets, and lysosomes as well as the aberrant interplays among these organelles that contributes to the onset and progression of aging-related disorders. Furthermore, potential therapeutic approaches based on these quality control interactions are discussed. Our perspectives can enhance insights into the regulatory networks underlying QCS and the pathology of aging and aging-related diseases, which may pave the way for the development of novel therapeutic targets.

Spatial organization of putrescine synthesis in plants

Three plant pathways for the synthesis of putrescine have been described to date. These are the synthesis of putrescine from ornithine, by ornithine decarboxylase (ODC); the synthesis of putrescine from arginine by arginine decarboxylase, agmatine iminohydrolase (AIH) and N-carbamoylputrescine amidohydrolase (NLP1); and arginine decarboxylase and agmatinase. To address how these pathways are organized in plants, we have used transient expression analysis of these genes in the leaves of Nicotiana benthamiana. Brassicas do not have ODC, but the single ODC gene from rice and one of the soybean genes, were localized to the ER. Transient expression of the rice agmatinase gene showed that it was localized to the mitochondria. In A. thaliana there are five isoforms of AIH and three isoforms of NLP1. Stable GFP-tagged transformants of the longest isoforms of AIH and NLP1 showed that both proteins were localized to the ER, but in tissues with chloroplasts, the localization was concentrated to lamellae adjacent to chloroplasts. Transient expression analyses showed that four of the isoforms of AIH and all of the isoforms of NLP1 were localized to the ER. However, AIH.4 was localized to the chloroplast. Combining these results with other published data, reveal that putrescine synthesis is excluded from the cytoplasm and is spatially localized to the chloroplast, ER, and likely the mitochondria. Synthesis of putrescine in the ER may facilitate cell to cell transport via plasmodesmata, or secretion via vesicles. Differential expression of these pathways may enable putrescine-mediated activation of hormone-responsive genes.

The interactions of subcellular organelles in pulmonary fibrosis induced by carbon black nanoparticles: a comprehensive review

Owing to the widespread use and improper emissions of carbon black nanoparticles (CBNPs), the adverse effects of CBNPs on human health have attracted much attention. In toxicological research, carbon black is frequently utilized as a negative control because of its low toxicity and poor solubility. However, recent studies have indicated that inhalation exposure to CBNPs could be a risk factor for severe and prolonged pulmonary inflammation and fibrosis. At present, the pathogenesis of pulmonary fibrosis induced by CBNPs is still not fully elucidated, but it is known that with small particle size and large surface area, CBNPs are more easily ingested by cells, leading to organelle damage and abnormal interactions between organelles. Damaged organelle and abnormal organelles interactions lead to cell structure and function disorders, which is one of the important factors in the development and occurrence of various diseases, including pulmonary fibrosis. This review offers a comprehensive analysis of organelle structure, function, and interaction mechanisms, while also summarizing the research advancements in organelles and organelle interactions in CBNPs-induced pulmonary fibrosis.

Super-Resolution Microscopy Unveils Synergistic Structural Changes of Organelles Upon Point Mutation

Ethyl methanesulphonate (EMS), is a widely used chemical mutagen that causes high-frequency germline null mutation by inserting an alkyl group into the nucleotide guanine in eukaryotic cells. The effect of EMS on the dynamics of the aneuploid genome, increased cellular instability, and carcinogenicity in relation to benign and malignant tumors are reported, but the molecular level understanding of morphological changes of higher-order chromatin structure has poorly been understood. This is due to a lack of sufficient resolution in conventional microscopic techniques to see small structures below the diffraction limit. Here, using super-resolution radial fluctuation, a largely fragmented, decompaction, and less dense heterochromatin structure upon EMS treatment to HEK 293A cells without any change in nuclear DNA domains is observed. This result suggests an early stage of carcinogenicity happened due to the point mutation. In addition, the distinct structural changes with an elongated morphology of lysosomes are also observed. On the other hand, fragmented and increased heterogeneous populations with an increased cytoplasmic occupancy of mitochondria are observed.

Epigenetic regulation of mitochondrial-endoplasmic reticulum dynamics in kidney diseases

Kidney diseases are serious health problems affecting >800 million individuals worldwide. The high number of affected individuals and the severe consequences of kidney dysfunction demand an intensified effort toward more effective prevention and treatment. The pathophysiology of kidney diseases is complex and comprises diverse organelle dysfunctions including mitochondria and endoplasmic reticulum (ER). The recent findings prove interactions between the ER membrane and nearly all cell compartments and give new insights into molecular events involved in cellular mechanisms in health and disease. Interactions between the ER and mitochondrial membranes, known as the mitochondria-ER contacts regulate kidney physiology by interacting with each other via membrane contact sites (MCS). ER controls mitochondrial dynamics through ER stress sensor proteins or by direct communication via mitochondria-associated ER membrane to activate signaling pathways such as apoptosis, calcium transport, and autophagy. More importantly, these organelle dynamics are found to be regulated by several epigenetic mechanisms such as DNA methylation, histone modifications, and noncoding RNAs and can be a potential therapeutic target against kidney diseases. However, a thorough understanding of the role of epigenetic regulation of organelle dynamics and their functions is not well understood. Therefore, this review will unveil the role of epigenetic mechanisms in regulating organelle dynamics during various types of kidney diseases. Moreover, we will also shed light on different stress origins in organelles leading to kidney disease. Henceforth, by understanding this we can target epigenetic mechanisms to maintain/control organelle dynamics and serve them as a novel therapeutic approach against kidney diseases.

Subcellular visualization: Organelle-specific targeted drug delivery and discovery

Organelles perform critical biological functions due to their distinct molecular composition and internal environment. Disorders in organelles or their interacting networks have been linked to the incidence of numerous diseases, and the research of pharmacological actions at the organelle level has sparked pharmacists' interest. Currently, cell imaging has evolved into a critical tool for drug delivery, drug discovery, and pharmacological research. The introduction of advanced imaging techniques in recent years has provided researchers with richer biological information for viewing and studying the ultrastructure of organelles, protein interactions, and gene transcription activities, leading to the design and delivery of precision-targeted drugs. Therefore, this reviews the research on organelles-targeted drugs based upon imaging technologies and development of fluorescent molecules for medicinal purposes. We also give a thorough analysis of a number of subcellular-level elements of drug development, including subcellular research instruments and methods, organelle biological event investigation, subcellular target and drug identification, and design of subcellular delivery systems. This review will make it possible to promote drug research from the individual/cellular level to the subcellular level, as well as give a new focus based on newly found organelle activities.

Multisubcellular organelle-targeting nanoparticle for synergistic chemotherapy and photodynamic/photothermal tumor therapy

Background: The subcellular organelle-targeting strategy has attracted wide attention for a variety of reasons, including strong specificity, high accuracy, low dose administration and few side effects. It is an important and challenging task to explore the multisubcellular organelle-targeting strategy to achieve effective tumor treatment. Materials & methods: Using bovine serum albumin as a nanoreactor, BSA/Cu/NQ/IR780/DOX nanoparticles (NPs) were constructed via drug-induced protein self-assembly. Folic acid was then coupled to the surface of NPs to prepare folate receptor-targeted FA-BSA/Cu/NQ/IR780/DOX NPs. Results & conclusion: The FA-BSA/Cu/NQ/IR780/DOX NPs exhibit multifunctional properties, including multisubcellular organelle-targeting, induction of response release in the tumor microenvironment, fluorescence imaging capabilities and potential for synergistic chemotherapy and photodynamic/photothermal tumor therapy.

Blocking Spatiotemporal Crosstalk between Subcellular Organelles for Enhancing Anticancer Therapy with Nanointercepters

The spatiotemporal characterization of signaling crosstalk between subcellular organelles is crucial for the therapeutic effect of malignant tumors. Blocking interactive crosstalk in this fashion is significant but challenging. Herein, a communication interception strategy is reported, which blocks spatiotemporal crosstalk between subcellular organelles for cancer therapy with underlying molecular mechanisms. Briefly, amorphous-core@crystalline-shell Fe@Fe₃ O₄ nanoparticles (ACFeNPs) are fabricated to specifically block the crosstalk between lysosomes and endoplasmic reticulum (ER) by hydroxyl radicals generated along with their trajectory through heterogeneous Fenton reaction. ACFeNPs initially enter lysosomes and trigger autophagy, then continuous lysosomal damage blocks the generation of functional autolysosomes, which mediates ER-lysosome crosstalk, thus the autophagy is paralyzed. Thereafter, released ACFeNPs from lysosomes induce ER stress. Without the alleviation by autophagy, the ER-stress-associated apoptotic pathway is fully activated, resulting in a remarkable therapeutic effect. This strategy provides a wide venue for nanomedicine to exert biological advantages and confers new perspective for the design of novel anticancer drugs.

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.

Soft X-ray tomography to map and quantify organelle interactions at the mesoscale

Inter-organelle interactions are a vital part of normal cellular function; however, these have proven difficult to quantify due to the range of scales encountered in cell biology and the throughput limitations of traditional imaging approaches. Here, we demonstrate that soft X-ray tomography (SXT) can be used to rapidly map ultrastructural reorganization and inter-organelle interactions in intact cells. SXT takes advantage of the naturally occurring, differential X-ray absorption of the carbon-rich compounds in each organelle. Specifically, we use SXT to map the spatiotemporal evolution of insulin vesicles and their co-localization and interaction with mitochondria in pancreatic β cells during insulin secretion and in response to different stimuli. We quantify changes in the morphology, biochemical composition, and relative position of mitochondria and insulin vesicles. These findings highlight the importance of a comprehensive and unbiased mapping at the mesoscale to characterize cell reorganization that would be difficult to detect with other existing methodologies.