Brain neurons play a crucial role to maintain organism health in response to macro/micro-environmental biophysical and biochemical cues, and their dysfunction and death drive aging and diseases. However, cellular mechanisms controlling neuronal health are incompletely understood. Drosophila has proven a paramount model to understand fundamental pathways of tissue development, homeostasis, and cell death in health and disease. Among these pathways, the regulation of nuclear structure and function, including genome organization, RNA synthesis and processing, DNA damage repair, and nucleocytoplasmic transport, has been shown to play a major role. In this regulation, the nucleoskeleton, a meshwork of type A/C and B Lamin proteins, provides an interface between the cytoskeleton and chromatin, controlling (epi)genome dynamics and nucleocytoplasmic compartmentalization, also by interacting with the inner nuclear membrane and pore complexes. In postmitotic neurons, LaminB is the major nucleoskeletal component. In this Review, I focus on the key role of nuclear LaminB dynamics in neuronal homeostasis in aging and cell death, highlighting the power of Drosophila models to uncover the underlying fundamental mechanisms. In this context, I spotlight that the regulation of nuclear LaminB structure and function is emerging as a stress-integration gatekeeper controlling neuronal response to macro/micro-environmental biophysical and biochemical cues, which maintains neuronal health, and whose impairment drives neuronal aging and non-apoptotic cell death in neurodegenerative diseases.
Synapses are ‘double-edged swords’, being appropriate for the quick transmission of impulses in one hand, but vulnerable to the oxidative stress in another hand. When the presynaptic terminals convey neurotransmission by altering structure of lipid molecules in response to physiological stimuli, membrane remodeling occurs rapidly at dendrites to make synaptic vesicles and release neurotransmitters. However, excessive stimuli due to stresses such as ischemia, trauma, irradiation, etc., cause changes of lipidomes at the presynaptic membranes to generate various lysophospholipids by overactivating phospholipase A2 (PLA2) and autotaxin. Lysophosphatidylcholine (LysoPC) is generated from the membraneous phosphatidylcholine (PC) via PLA2, while lysophosphatidic acid (LysoPA) is generated from LysoPC via autotaxin. LysoPC at the synaptic area enhances the membrane excitability, and LysoPA interferes with the cytoskeleton, both facilitating neuronal injuries. Here, the author focused on the ultrastructural visualization of lysophospholipids to elucidate detrimental effects of stress-induced lysophospholipids which were generated at the synaptic area. Lipidomics can detect LysoPC and LysoPA involved in the body fluids, however, cannot detect LysoPC accumulated in the restricted brain area. This is due to an insufficient spatial resolution of standard lipidomic/mass spectrometry approaches, and/or a technical limitation specific to LysoPC extraction/detection in the brain tissue. Since tannic acid interacts with the choline head-group of PC or LysoPC, and tannic acid-choline aggregates are postfixed by osmium tetroxide, it was utilized to visualize them by electron microscopy. Using tannic acid, PC is ultrastructurally observed as distinct double membrane structures, whereas LysoPC is visualized as extramembraneous, multilamellar bodies. In the monkey brain after ischemia, multilamellar bodies were clearly seen in the vicinity of synaptic vesicle membranes of hippocampal neurons. This review highlights the regional toxicity of lysophopholipids due to the transition from physiological lipid remodeling to pathological PLA2 overactivation.
Regulated cell death (RCD) encompasses genetically encoded and pharmacologically modifiable pathways that govern cellular demise. In the nervous system, RCD assumes unique biological and clinical relevance due to neurons’ post-mitotic status, the functional integration of neural circuits, and the central role of glial cells in homeostasis and inflammation. This review synthesizes current knowledge on apoptotic and non-apoptotic RCD modalities in neurons and glia, integrates molecular mechanisms with ultrastructural hallmarks, and discusses specific patterns of pathway engagement. We emphasize compartmentalized death, pathway crosstalk, and cell-type specificity.
Immune checkpoint inhibitors (ICIs) have transformed cancer care, yet durable responses remain limited in a majority of patients. This is particularly true of immunologically cold tumors, which are characterized by insufficient T-cell infiltration, low antigenicity, impaired adjuvanticity, and an immunosuppressive tumor microenvironment (TME). Z-form Nucleic Acid (Z-NA) Binding protein 1 (ZBP1)-initiated signaling, by overcoming these barriers, offers a mechanistic solution to rekindling ICI responsiveness in cold tumors. ZBP1 is an immune sensor which detects viral or endogenous Z-NAs, binds the kinase RIPK3, and activates Mixed Lineage Kinase Like pseudokinase (MLKL)-mediated necroptosis. ZBP1-initiated signaling can also inflame tumors non-cytolytically, including by activating inflammatory gene expression. Tumors frequently inactivate ZBP1 signaling, most notably by epigenetically silencing RIPK3. However, TME cells, particularly inflammatory cancer-associated fibroblasts (iCAFs), retain RIPK3 competence and represent a readily exploitable therapeutic vulnerability for activation of ZBP1-mediated immunogenic signaling within the tumor mass. Here, we discuss emerging strategies to activate ZBP1 within cold tumors as a means to enhance ICI-driven anti-tumor responses.
BackgroundBiliary Tract Cancers (BTCs), including cholangiocarcinoma and gallbladder cancer, are aggressive malignancies characterized by late diagnosis, high mortality, and intrinsic resistance to standard chemotherapeutic regimens like gemcitabine and cisplatin. A critical barrier to improving therapeutic outcomes is the historical reliance on 2D monolayer cultures. These conventional models fail to recapitulate the complex Tumor Microenvironment (TME), leading to poor predictive validity and high attrition rates in drug discovery.ScopeThis review critically examines the paradigm shift from reductionist 2D cultures to advanced 3D tumor models—as superior in vitro platforms for decoding drug resistance and apoptosis evasion in BTCs, while acknowledging that 2D model limitations represent only one component of a broader translational pipeline that includes animal models, biomarker gaps, and anatomical challenges.Key InsightsThe article highlights that 3D architectures uniquely recapitulate physiological barriers absent in monolayers, including hypoxia-driven metabolic reprogramming, dense Extracellular Matrix (ECM) shielding, and drug distribution gradients. These models reveal specific “multicellular resistance” (MCR) mechanisms, such as the dysregulation of the Bcl-2 rheostat (particularly Bcl-xL and Mcl-1 dependence). Furthermore, 3D systems provide a more accurate context for investigating alternative cell death pathways, including ferroptosis and necroptosis, and for identifying quiescent cancer stem cell populations protected by the niche.Conclusion3D tumor models, particularly PDOs, serve as high-fidelity “clinical avatars” that bridge the translational gap between preclinical screening and precision oncology. While challenges regarding standardization, immune component integration, and scalability remain, the adoption of these physiologically relevant systems is imperative for developing effective combinatorial therapies and overcoming the profound chemoresistance inherent to BTCs.
April 2024 marked the 30-year anniversary of the publication of reaper, the first description of a Drosophila cell death gene. This discovery established the foundation for modern apoptosis research in Drosophila and fundamentally reshaped studies on programmed cell death (PCD). This review provides a historical and mechanistic overview of apoptosis research in Drosophila, with a particular emphasis on the discovery and legacy of reaper. Rather than providing a comprehensive review of the entire field, this article emphasizes some of the main lessons learned from Drosophila cell death research and their general impact. One of the first lessons was that reaper is transcriptionally activated by many different death-inducing signals, suggesting that apoptosis is a transcriptionally regulated, developmentally patterned process. Mechanistically, reaper and its neighboring genes head involution defective (hid), grim, and sickle, collectively referred to as RHG genes, induce apoptosis by neutralizing the anti-apoptotic Drosophila Inhibitor of Apoptosis-1 (DIAP1) protein. DIAP1 is required to prevent unwanted caspase activation and apoptosis in virtually all somatic cells. RHG proteins de-repress caspases by inducing the self-conjugation and degradation of this E3-ligase protein. This mechanism provided a conceptual bridge to mammalian IAP-antagonists such as Smac/DIABLO and ARTS, which were discovered 6 years later. The RHG proteins introduced a fundamental principle in cell death regulation: that apoptosis in higher animals can be triggered by precisely controlled expression of IAP antagonists, rather than activation of caspases alone. Over 3 decades, Drosophila has proven indispensable in elucidating caspase regulation in vivo, transcriptional control of cell death, the role of apoptosis in developmental and tissue morphogenesis, the hormonal regulation of apoptosis, ubiquitin-proteasome-mediated protein degradation in cell death, apoptosis-induced proliferation, and non-apoptotic cell death pathways, including autophagic, necrotic, and inflammatory forms of regulated cell death. Due to its genetic and anatomical accessibility, Drosophila continues to drive conceptual advances with relevance to cancer, neurodegeneration, immunity, and regeneration.
Aging is a complex biological process characterized by gradual cellular and molecular changes contributing to cognitive decline and neurodegeneration. Histone alterations regulate gene expression, chromatin organization, and neuronal function. Additionally, nuclear architecture undergoes significant alterations during aging, with lamin B, a key component of the nuclear lamina, playing a pivotal role in maintaining the stability of the cell nucleus. Lamin B1 (LB1) dysfunction has been implicated in age-related neuronal decline, as aberrations in its expression or processing can lead to nuclear deformation, impaired gene regulation, and increased susceptibility to DNA damage to the point that LB1 is now regarded as a cellular senescence marker. We have studied the immunocytochemical localization of trimethylated histone H4 at lysine 20 (H4K20me3), acetylated histone H4 at lysine 12 (H4K12ac), and LB1 in the brain of postnatal day 5 (P5) pups, mature adult (9–10 months), and old (24 months) mice, aiming to find a correlation between histone epigenetic modifications, senescence, and cell death, with particular attention to the hippocampus and cerebral cortex. We first describe the distribution of the three molecules throughout the different brain regions, and confirm these data with Western blot analysis. We then show that H4K20me3 and H4K12ac can be detected in both neurons and glia. After inferential statistics and effect size analysis, we demonstrate that a biologically meaningful reduction in the expression of the three molecules occurs in the old hippocampus. In addition, a biologically relevant decrease in the degree of cellular coexistence of H4K20me3 and H4K12ac was observed in the hippocampus and cerebral cortex. Understanding how histone and LB1 modifications influence brain aging provides valuable insights into the molecular pathways that drive neurodegeneration and may offer clues to better understanding age-related cognitive disorders.
Cell death shapes multicellular organism development and sustains tissue and organ homeostasis. Great progress has been made in understanding the breadth of physiological and biochemical diversity in cell death and clearance pathways, which play vital roles in organismal development and health. While apoptosis and necrosis have been studied extensively across many model systems and contexts, the discovery of non-apoptotic paradigms of cell death and their roles in disease has greatly expanded the field. Collectively called Regulated Cell Death, these death pathways operate in a tissue and context-dependent manner. Germ cells in many organisms develop in cysts of interconnected cells, and may die in response to environmental or developmental cues. Recent findings suggest that germ cell cysts may use a common mechanism of non-apoptotic cell death involving phagocytic and lysosomal activity of surrounding somatic cells. Cyst cell death has been analyzed most thoroughly in the Drosophila adult ovary and testis, with remarkable similarity to cyst cell death in mouse adult testis and fetal ovary. In this review, we highlight recent progress in deciphering germline cyst cell death.
Copper is an essential cofactor for all organisms. However, it can become toxic if its concentration rises above a specific level. This level is controlled by evolutionary conserved homeostatic mechanisms. Recently, a new type of cell death called cuproptosis has been found. The process represents a copper-dependent, regulated form of cell death that is distinct from all known death mechanisms and relies on mitochondrial respiration. The mechanism of cuproptosis involves the direct binding of copper to lipidated parts in the tricarboxylic acid (TCA) cycle. This results in the abnormal aggregation of lipoylated proteins and the destabilization of iron-sulfur cluster (Fe-S) proteins. These events induce proteotoxic stress, ultimately leading to cell death. Copper-induced cell death is controlled by proteolipid acylation, which is mediated by the mitochondrial iron-sulfur protein FDX1. Copper overload also inhibits the biosynthesis of iron-sulfur (Fe-S) clusters and impairs the activity of Fe-S enzymes. As a result, mitochondrial function is disrupted. Both copper-induced cell death and impaired copper homeostasis arise from the same mechanistic basis. The expression of copper import gene SLC31A1 (CTR1) and export genes ATP7A and ATP7B significantly influences cuproptosis. The tumor suppressor p53 may participate in this process by modulating glycolysis and mitochondrial metabolism. In contrast, glutathione (GSH) reduces copper ion cytotoxicity by binding copper to form a complex. The growth and spread of tumor cells is more dependent on copper than that of normal cells.The copper ionophore elesclomol (ES) kills cancer cells by transporting copper ions into them. This ES-Cu complex not only inhibits cancer cell proliferation but also activates an immune response. Moreover, when ES is combined with αPD-L1, it might increase the effectiveness of cancer treatment. This gives a new idea for treating cancer.
Lysosome is crucial for maintaining cellular homeostasis, but disintegrity of its limiting membrane affects the cell death fate. From 1972 to 1999, via the cytochemistry of cultured cells which were exposed to stresses, Brunk et al. defined lysosomal membrane permeabilization (LMP) as leakage through the ultrastructurally-intact limiting membrane. In 1996, via the electron microscopic analysis of the monkey hippocampal CA1 neurons after transient ischemia, Yamashima et al. first identified lysosomal membrane rupture (LMR) as an apparent disruption of the limiting membrane. To elucidate the mechanism of lysosomal cell death, it is indispensable to precisely differentiate LMP and its extensive form LMR. LMP indicates formation of ultrastructurally-undetectable, tiny pores at the lysosomal limiting membrane that allow selective leakage of lysosomal contents. LMP contributes to amplification of the cell death signal, and participates in apoptosis. In contrast, LMR indicates presence of larger holes that cause acute and massive leakage of hydrolytic cathepsin enzymes. LMR leads to the rapid and explosive vanishment of lysosomes, which proceeds along with vanishment of cells, i.e., necrosis. Each representative form of cell death is carried out in human diseases, depending upon the size and number of perforations, the amount of leakage, and the cellular context. The modality of the lysosomal membrane disintegrity, LMP or LMR, determines the cell death fate. It is likely that apoptosis occurs by the proteolytic activation of caspases via LMP, whereas necrosis occurs by the calpain-cathepsin cascade via LMR. This paper is to review ultrastructural evidences of LMR which were identified in diverse pathologic conditions of C. elegans, mice, monkeys, and humans. For elucidating mechanisms of each cell death in the organs affected by stresses, LMP and LMR should be precisely differentiated by electron microscopy. Herein, other lysosomal cell death such as pyroptosis and ferroptosis was discussed to make the difference clear. Ferroptosis might share very similar calpain-cathepsin cascade with necrosis.
The epidermis is routinely subjected to DNA damage induced by ultraviolet B (UVB) solar radiation. In addition to activating canonical DNA damage responses such as cycle cell checkpoints and DNA repair, UVB-induced DNA damage can also activate additional signaling pathways including inflammatory responses. The pathways activated downstream of UVB-induced DNA damage have a critical role in determining cellular survival to UVB radiation. Here we report that loss of CCAAT/enhancer binding protein β (C/EBPβ) in mouse keratinocytes results in enhanced UVB-induced apoptosis through activation of extrinsic apoptosis genes cleaved caspase-8 and truncated BH3 interacting-domain death agonist (tBid). RNAseq and Ingenuity Pathway Analysis of UVB-treated C/EBPβ−/− primary keratinocytes revealed an enrichment of inflammatory signaling pathways, including the type I interferon (IFN-I) pathway as the most enriched pathway. Numerous IFN-I stimulated genes were up-regulated in UVB-treated C/EBPβ−/− keratinocytes, including genes that regulate extrinsic apoptosis. Inhibition of the interferon-α/β receptor or the associated kinase Tyk2 greatly reduced cell death in UVB-exposed C/EBPβ deficient keratinocytes, demonstrating the dependence of IFN signaling in C/EBPβ regulated apoptosis. The apoptosis inducing cytokine tumor necrosis factor alpha (TNF-α) was identified as one of the most significant upstream regulators activated in UVB-exposed C/EBPβ−/− keratinocytes compared to UVB exposed wild type control. UVB-exposed C/EBPβ−/− keratinocytes displayed increased expression of TNF-α and the enhanced apoptosis in C/EBPβ−/− keratinocytes was suppressed by a TNF-α neutralizing antibody. Our results indicate that loss of C/EBPβ enhances activation of a non-canonical UVB DNA damage response pathway involving interferon and TNF signaling to induce keratinocyte cell death.
The deubiquitinating enzyme CYLD hydrolyzes Lys63-and Met1-linked ubiquitin chains, playing a crucial role in regulating various cellular processes such as immune cell development, innate and adaptive immunity, spermatogenesis, ciliogenesis, and cell survival. CYLD also functions as a tumor suppressor and is mutated in familial cylindromatosis. This pleiotropic function implies tight regulatory mechanisms. In this review, we summarize the current knowledge on CYLD’s molecular characteristics, subcellular location, and binding partners, with a focus on its involvement in life-and-death decisions. In addition, we discuss how post-translational modifications, including phosphorylation, ubiquitination, and proteolysis, shape CYLD’s function, unveiling the potential for therapeutic intervention. Finally, we highlight the remaining challenges that need to be overcome to deepen our understanding of this crucial enzyme.
Apoptosis is a form of programmed cell death that eliminates excessive and damaged cells. It can be conducted by two ways: the extrinsic and the intrinsic (mitochondrial) pathways. The extrinsic death pathway is triggered by activation of the death receptors (DRs), while the intrinsic pathway is initiated by changes at the mitochondria. The induction of life and death signals via DRs requires an intricate regulation of signal transduction. In this regard, an optimal conformation of the extracellular domain of DR is required for the Death Ligand (DL) binding and initiation of DR signaling. Glycosylation, the enzymatic attachment of carbohydrates to proteins, can influence DR conformation and thereby receptor-ligand interaction. Due to the tremendous structural diversity of glycans attached to DRs, little is known about the role of specific glycosylation subtypes influencing functions of DRs. Deciphering the role of specific glycan signatures, so-called “glyco-code”, on DRs is important to understand how glycans are involved in signal transduction. Although apoptosis has been shown to be associated with altered glycosylation patterns of glycoproteins, our understanding how glycosylation modulates apoptosis is still limited. This review focuses on summarizing our current knowledge on the modulation of cell signaling via glycosylation of DRs.
When yeast cells are transferred to water only, they remain viable for several days. However, when transferred to water with glucose, there is a rapid loss of viability. This phenomenon is termed Sugar-Induced Cell Death (SICD). In addition to glucose, SICD can be induced by an array of different sugars and is thought to be triggered by increased levels of intracellular reactive oxygen species (ROS) generated upon transfer to sugar-only solutions. Although not termed SICD, a similar response is observed in mammalian cells, whereby high glucose induces cell death, especially in cases of hyperglycemia and diabetes. In contrast, cancer cells thrive under conditions of high glucose. In this review, we summarize the current understanding of SICD in yeast and highlight studies showing the presence of a similar phenomenon in mammalian cells, High Glucose-Induced Cell Death (HGICD). We end with a discussion on mechanisms by which cancer cells evade HGICD. Unlike other types of cell death in yeast, SICD has not yet been thoroughly reviewed. Therefore, this review represents the first comprehensive review of SICD in yeast with a comparison to HGICD in other eukaryotes.
Glucose deprivation (GD), a common metabolic stress condition, has been recognized as a potent inducer of necroptotic cell death. Our previous findings suggested that the mitochondrial protein, Noxa, may be involved in mediating the release of mitochondrial DNA during GD-induced ZBP1-dependent necroptotic pathway. However, the functional significance of Noxa in necroptosis under GD treatment remains unclear. Here, we investigated the role of Noxa in GD-induced necroptosis and the underlying molecular mechanisms governing its expression. We revealed that Noxa is required for the induction of necroptosis under GD. We also demonstrated that the upregulation of Noxa induced by GD is mediated by ATF4, a key transcription factor. These results provide insights into the regulatory mechanisms underlying Noxa dynamics during GD treatment and highlights its potential as a therapeutic target in cancer therapy and necroptosis-related diseases.
Pyroptosis is a form of proinflammatory cell death characterized by inflammasome activation, pore formation, and the release of pro-inflammatory cytokines such as interleukin-1β (IL-1β) and IL-18 upon cell rupture. Nuclear factor-κB (NF-κB), a prototypical pro-inflammatory transcription factor, plays a critical role in immune system regulation. Recent research highlights the multifaceted roles of NF-κB signaling in pyroptosis. Various immunologically relevant ligands and their receptors can activate the NF-κB pathway to promote pyroptosis, with Toll-like receptors (TLRs), IL-1 receptors (IL-1Rs), and TNF receptors (TNFRs) being the most prominent. NF-κB regulates the transcription of key components of inflammasomes involved in pyroptosis, particularly the NLRP3 inflammasome. Recent studies also indicate that NF-κB modulates the activation of NLRC4 and AIM2 inflammasomes through distinct pathways in diverse inflammatory conditions, such as acute lung injury and neuroinflammation. Additionally, the NF-κB pathway mediates the production of inflammatory cytokines, including IL-1β, IL-33, and TNF-α, which further regulate pyroptosis. This review examines recent advances in understanding the role of the NF-κB signaling pathway in regulating pyroptosis during infection and inflammation.
Mitochondria are multifaceted organelles acting as energy, metabolic and signaling hubs in the cells. They play a central role in biological processes aimed at maintaining cell homeostasis and regulating cell fate upon changing environments. Alterations in mitochondrial functions can affect cell stress response through different mechanisms, leading to adaptation or death. In this perspective, we focus on mitochondrial communication and its relevance for cytoprotective strategies aimed at controlling synthesis, degradation and recycling processes. The advantage of using yeast as a model organism for improving our understanding of the molecular mechanisms behind cell stress responses to mitochondrial dysfunction is described. New challenges for studying the interplay between mitochondrial retrograde signaling and autophagy/mitophagy pathways are highlighted.
Cell death is an essential physiological process for the survival of multicellular organisms. Our understanding of programmed cell death in development, immune function maintenance, and adult tissue repair has significantly advanced over the past decade. However, there are still gaps in our knowledge about the induction, regulation, and checkpoints of this process due to the diverse forms of cellular suicide and the rapid nature of the process. Molecular advancements such as specific cell death sensors, RNA-seq, single-cell RNA-seq, and proteomics have allowed for identifying new factors and a better understanding of the molecular networks and pathways that regulate these processes. Programmed cell death also plays a role in cancer, both limiting and facilitating aspects of the malignant process, making its analysis and inhibition challenging. This review discusses the field’s advancements using the model organism Drosophila melanogaster, the types of cell death in development and adult tissues, the techniques for studying it, and its role in cancer.
