Senescent cell heterogeneity: origins, detection, and therapeutic implications Although senescent cells are commonly characterized by stable cell cycle arrest, emerging evidence indicates that senescence is not a uniform state but a collection of highly heterogeneous phenotypes. This heterogeneity stems from biological factors, such as diverse senescence markers, cellular origins, and targeting mechanisms, as well as from technical variations in experimental approaches, notably in the design of transgenic mouse models. By summarizing recent advances in next-generation senolytic strategies, multiomics profiling, and genetically engineered mouse models of senescence, we provide an integrated perspective on the origins and consequences of senescent cell heterogeneity. Such a perspective is essential for refining investigative methodologies and for developing precise therapies that selectively target senescent cell populations whose roles have been experimentally validated in vivo.

Senescent cell heterogeneity: origins, detection, and therapeutic implications

The heme-regulated inhibitor eIF2α kinase: a multifaceted sensor and drug target Heme-regulated eukaryotic translation initiation factor 2 alpha kinase (HRI) is highly expressed in red blood cell precursors and plays a critical role in their maturation by coupling globin synthesis to heme availability. HRI plays critical roles in responding to cytoplasmic and mitochondrial unfolded proteins, oxidative stress response, innate immunity, neurobiology, and the suppression of epithelial cancers. HRI activity is regulated by multiple signaling networks, which, in turn, modify cellular homeostatic responses. In this review, we summarize emerging evidence on the role of HRI in normal biology and pathobiology, the molecular underpinnings of HRI’s regulation, and discuss chemical modifiers of HRI, which may form the basis of drug development programs for the treatment of human disorders whose pathobiology can be modified by HRI.

The heme-regulated inhibitor eIF2α kinase: a multifaceted sensor and drug target

Noninvasive methods to monitor dynamic single-cell events Adaptations to changing environments manifest in various cellular activities across multiple timescales, where single-cell responses can occur asynchronously between individual cells. Hence, accurate delineation of transient or rare activities often requires real-time monitoring of single cells over hours or days. While great strides have been made in the throughput of molecular analysis methodologies, most biochemical methods are cell destructive and, therefore, can only provide snapshots of dynamic processes. Noninvasive observations of natural cell behaviors offer unique insights into key dynamic events. In this feature review article, we discuss current toolkits for monitoring real-time dynamics of diverse cellular activities in living cells, as well as their advantages and challenges. We also speculate on new avenues for noninvasive single-cell monitoring that will be feasible in the foreseeable future.

Noninvasive methods to monitor dynamic single-cell events

Generating exosome subtypes: diverse membrane origins and mergers Exosomes are formally defined as extracellular vesicles, which are formed in compartments with endosomal origin by the inward budding of the endosomal limiting membrane. Recent analyses of the dynamic events within exosome-generating compartments have overturned the dogma that only late endosomal membranes produce exosomes. It is now clear that recycling endosomal, autophagic, regulated secretory, and other organelle membranes contribute to exosome production. In this opinion article, we discuss studies demonstrating the critical roles of membrane origins and mergers, together with intracompartmental microenvironments, in generating intraluminal vesicle and exosome subtypes with diverse physiological and pathological functions, both inside and outside the secreting cell. These findings provide significant opportunities to develop novel strategies that overcome the current challenges of detecting and targeting disease-relevant exosomes.

Generating exosome subtypes: diverse membrane origins and mergers

Ferroptosis as an approach to leverage cancer metabolism Ferroptosis is a cell death process defined by the iron-mediated peroxidation of membrane phospholipids that overwhelms the cell’s innate antioxidant capabilities. Sitting at the nexus of iron, lipid, reactive oxygen species-induced stress responses, and cellular metabolism, ferroptosis is intricately tied to these pathways. The burgeoning field of cancer metabolism has revealed that cancer cells exhibit changes in ferroptosis-relevant metabolic pathways, thereby opening an important avenue of investigation into whether tumors can have characteristic metabolic alterations that render them exquisitely sensitive to ferroptotic cell death. In this review, we highlight recent findings in the metabolic pathways linking ferroptosis and oncogenesis, as well as implications for future cancer therapeutic strategies.

Ferroptosis as an approach to leverage cancer metabolism

Proteostasis regulation in T cell dysfunction: dual regulation by KLHL6 T cell exhaustion represents a major barrier to the efficacy of cancer immunotherapy, driven by complex transcriptional reprogramming, epigenetic remodeling, and metabolic imbalance. Cheng et al. report in Nature that the E3 ubiquitin ligase Kelch-like protein 6 (KLHL6) dually suppresses T cell exhaustion and mitochondrial dysfunction via proteostasis control, establishing a new therapeutic target.

Proteostasis regulation in T cell dysfunction: dual regulation by KLHL6

Neutral lipid quality control gates ferroptotic cell death By uncovering a lipid droplet (LD) quality-control pathway driven by ferroptosis suppressor protein 1, Lange et al. show that neutral-lipid oxidation shapes ferroptosis vulnerability. This work expands ferroptosis regulation beyond membrane phospholipids and positions LDs as active redox control sites with broad implications for cell fate regulation.

Neutral lipid quality control gates ferroptotic cell death

Eosinophil extracellular traps: heterogeneity of their stimuli, components, and functions Eosinophils participate in immune regulation through their granule proteins and cytokines. Recent studies demonstrate eosinophil functional versatility through the mechanism of eosinophil extracellular traps (EETs). EET formation occurs via suicidal eosinophil extracellular trap cell death (EETosis) and vital EET release. EETs contain chromatin- or mitochondrial-derived DNA, granule proteins, nuclear proteins, and cytosolic components that vary depending on the type and intensity of stimuli. Synthetic compounds, pathogenic microorganisms, endogenous molecules, and co-stimulatory factors stimulate EET formation via diverse signaling pathways through receptors that rely on or operate independently of NADPH oxidase-mediated reactive oxygen species production and peptidylarginine deiminase-4-dependent histone modification. Necroptosis, pyroptosis, and autophagy pathways also contribute to EET biogenesis and subset heterogeneity. Here, we summarize EET formation, compositional profile, and functional heterogeneity across disease states, as well as the future potential for novel immune intervention.

Eosinophil extracellular traps: heterogeneity of their stimuli, components, and functions

Endoplasmic reticulum architecture in liver metabolic regulation The endoplasmic reticulum (ER) is a central hub for essential cellular processes, including lipid and glucose metabolism, protein folding, calcium homeostasis, and detoxification. The ER exhibits a complex architecture, comprising multiple subdomains such as the nuclear envelope and the peripheral ER, which is further organized into sheets, tubules, three-way junctions, and contact sites. Both ER form and function are highly adaptive, with a robust capacity to respond to changes in environmental cues such as nutritional states. Here, we discuss remodeling of ER shape - as a fundamental mechanism of metabolic regulation, which enables the diversification and fine-tuning of metabolic function in physiology, while also representing a potential point of vulnerability during metabolic stress. We focus on the liver, a central organ in systemic energy homeostasis, and examine how hepatic ER morphology and its dynamic interorganelle interactions are reorganized in response to nutritional fluctuations and how this remodeling reflects on metabolic function.

Endoplasmic reticulum architecture in liver metabolic regulation

Plasma membranes: does one model fit all? Biological membranes consist of a lipid bilayer with a highly asymmetric distribution of lipids in the two leaflets. This asymmetry is maintained by enzymes whose activities depend on cytosolic ATP and Ca2+ concentrations. Recently, a new model for plasma membranes (PMs) was introduced. It is based on studies with human erythrocytes and suggests that there is a 50% overabundance of lipids with two hydrophobic chains in the cytosolic leaflet, compensated by the presence of three times more cholesterol in the outer leaflet. In this opinion article, we discuss the large differences in lipid composition between erythrocytes and other cell types, the assumptions used to reach the new membrane model, and whether this model would fit PMs of other cell types.

Plasma membranes: does one model fit all?

Targeting mitochondrial dynamics against cancer Although cancer treatment has improved, many patients exhibit limited responses due to the intrinsic heterogeneity and adaptability of tumors, coupled with immunosuppressive conditions in the tumor microenvironment (TME). Mitochondrial dynamics, characterized by continuous fusion and fission, influences cellular processes such as metabolism, cell cycle, cell death, and stemness, thereby profoundly shaping tumor cell evolution and TME plasticity. In this review, we summarize recent advances regarding the roles of mitochondrial dynamics in cancer biology and discuss how it regulates the behavior of both tumor cells and tumor-associated immune cells in the TME. We propose that targeting mitochondrial dynamics represents a dual therapeutic strategy that disrupts core oncogenic programs while potentiating antitumor immunity, offering a promising direction for future cancer treatment.

Targeting mitochondrial dynamics against cancer

Deciphering the significance of p53 mutant proteins The following sections were incomplete in the article. The completed sections are as follows:

Deciphering the significance of p53 mutant proteins

Lysosome: a critical hub for ferroptosis regulation Ferroptosis is an iron-dependent programmed cell death that involves lipid peroxidation. Ferroptosis represents a critical process underlying tumorigenesis and multiple pathological disorders. Recently, lysosomes have been found to orchestrate ferroptotic signaling, linking iron metabolism, oxidative homeostasis, and selective autophagy. Furthermore, lysosomal membrane disruption leads to the release of intraluminal iron and cathepsins, thereby facilitating ferroptotic damage, whereas lysosomal exocytosis acts in the opposite direction to limit ferroptosis. Therefore, pharmacological modulation of lysosomal activities could be used to treat drug-resistant tumors or protect normal tissues against ferroptosis-related injuries. In this review, we summarize how lysosomes control ferroptosis, focusing on the regulation through lysosomal contents, pH, degradation processes, and exocytosis. We also discuss possible therapeutics that target lysosomes to modulate ferroptosis-associated diseases.

Lysosome: a critical hub for ferroptosis regulation

Whi3key old fashioned: a condensate cocktail for cell fate decisions How do single cells weigh conflicting internal and external signals to arrive at unambiguous fate decisions? Peskett et al. reveal that a partnership between two condensates, Whi3 assemblies and P-bodies, forms a decision module in budding yeast that encodes aging information and enables context-dependent choices between proliferation, senescence, and mating.

Whi3key old fashioned: a condensate cocktail for cell fate decisions

Tetraploids or polyploid giants: who is truly dangerous? Tetraploidy, resulting from a single whole-genome duplication (WGD) event, contributes to tumorigenesis by promoting genomic instability and functional diversity. In general, WGD beyond tetraploidy limits proliferative and tumorigenic potential, but an increasing number of studies suggest that polyploid giant cancer cells (PGCCs)—large, highly polyploid (≥8N) cells formed in response to chemotherapy—produce daughter cells with reduced DNA content that drive cancer progression. In this opinion article, we examine the literature on tetraploid cells and PGCCs from a cell biology perspective. It is our opinion that the role of tetraploidy in cancer is supported by findings from cell lines, animal models, and tumor sequencing data, while definitive evidence that viable progeny from PGCCs can promote cancer progression in human tumors is lacking.

Tetraploids or polyploid giants: who is truly dangerous?

H3K9 trimethylation homeostasis: mechanisms, crosstalk, and cancer relevance

Repair condensates and lipid domains in lysosome integrity Lysosomes are sophisticated signaling hubs whose function depends on membrane integrity. A breach of this barrier, known as lysosomal membrane permeabilization, triggers inflammation and cell death, driving pathologies from lysosomal storage disorders to neurodegeneration. Cells counter membrane damage with diverse repair mechanisms, including endosomal sorting complexes required for transport machinery, sphingomyelin scrambling, annexin-mediated scaffolding, lipid transport, and stress granule plugging. This diversity suggests singular strategies are insufficient, posing an ‘orchestration challenge’ regarding precise initiation, spatial organization, and temporal coordination. This opinion article proposes that biomolecular condensation, initiated by damage cues, acts as a primary organizing principle. We suggest lysosomal injury nucleates de novo ‘repair condensates’ that stabilize compromised membranes and serve as recruitment and organizational hubs for repair machinery.

Repair condensates and lipid domains in lysosome integrity

T-loop dynamics: telomere structure shapes cell fate decisions

Epithelial barrier homeostasis Epithelia cover the body’s surface to form a barrier that segregates the internal body from the external environment. Tight junctions (TJs) seal the paracellular space and are crucial for the formation of the epithelial barrier. Epithelial barrier integrity is challenged by mechanical stress, infection, genetic lesions, or inflammation, and epithelial barrier defects must be prevented or repaired to maintain epithelial barrier homeostasis. Recent research is starting to uncover the molecular mechanisms underlying epithelial barrier homeostasis. This review provides an overview of how epithelial barrier defects are prevented and repaired and discusses the pathophysiological roles of epithelial barrier homeostasis. Furthermore, recent findings showing that epithelial barrier defects may occur in a controlled manner to facilitate bulk paracellular transport are discussed.

Epithelial barrier homeostasis

Cullin–RING receptors in rare disease biology The ubiquitin–proteasome system governs selective protein turnover in all eukaryotes, and its cullin–Really Interesting New Gene (RING) ligases represent the largest class of E3 ligases. Their substrate receptors (SRs) act as the ‘specificity engines’ of degradation, yet their contribution to human genetic disease has only recently come into focus. In this review, we provide the first systematic catalogue of 267 SRs, of which 93 are now linked to germline disorders. We synthesise emerging mechanisms, from altered degron recognition to noncanonical SR functions, and highlight how patient variants illuminate pathways for diagnosis and therapy. By connecting proteostasis, rare-disease genetics, and targeted protein degradation, SRs emerge as central nodes with broad implications for precision medicine.

Cullin–RING receptors in rare disease biology

Decoding and deciphering a subcellular ZIP code system Proteins contain unique sequences that direct localization within cells, forming a subcellular ‘ZIP code’ system. Kilgore et al. recently developed an artificial intelligence/machine learning (AI/ML) approach for predicting protein subcellular localization. Internalizing phage display, together with other current experimental methods, may be applicable alongside AI/ML approaches for profiling the subcellular ZIP code system.

Decoding and deciphering a subcellular ZIP code system

The role of retrotransposons in hematopoiesis and cancer Retrotransposons are DNA elements capable of inserting themselves into various regions of the genome, potentially leading to genomic changes. Their expression is tightly regulated by epigenetic and environmental factors, such as DNA methylation and radiation. For a long time, the effects of retrotransposons were poorly understood and largely overlooked. However, recent studies have demonstrated the significant role retrotransposons play in hematopoiesis under both healthy and stress conditions, such as during pregnancy or infection. Additionally, the expression of retrotransposons has been strongly correlated with various types of cancer. Depending on the cancer type, retrotransposons appear to exert both protumorigenic and antitumorigenic effects. This review summarizes current findings on the role of retrotransposons in hematopoiesis and cancer and highlights their potential as valuable tools for diagnosis and treatment.

The role of retrotransposons in hematopoiesis and cancer

Expanding roles of N-glycosylation in the endoplasmic reticulum N-linked glycosylation in the endoplasmic reticulum (ER), catalyzed by two oligosaccharyltransferase (OST) complexes, has long been viewed as a constitutive post-translational modification. Recent discoveries suggest that OST complexes play a much more plastic and directive role in regulating ER processes. Here, we review this work and focus on one specific mechanism that uses N-glycosylation to regulate the stability of the ER chaperone HSP90B1. This degradative process regulates the cell-surface abundance of multiple signaling receptors that are HSP90B1 clients: toll-like receptors, WNT receptors, and growth factor receptors. This unusual system enables the status of ER-based processes to influence the sensitivity of cells to extracellular signals, with implications for tissue growth and development, inflammation, and immune function.

Expanding roles of N-glycosylation in the endoplasmic reticulum

Endolysosomal transport at the crossroads of cellular signaling The endolysosomal system in eukaryotic cells regulates nutrient uptake and maintains the composition of the plasma membrane, among many other functions. In autophagy, it contributes not only to the cellular quality control system to remove damaged organelles, aggregates, and pathogens but also to cellular recycling of amino acids. Transport in the endolysosomal network relies on the correct identity of the involved organelles. Rab GTPases and lipid kinases provide this membrane identity on each organelle, thereby orchestrating the protein machinery for membrane fusion and fission. Dynamic exchange of identity markers provides the basis for adaptations of the endolysosomal system, which is closely linked to cellular nutrient signaling. Here, recent structural and functional insights into the regulation and interplay of Rab regulators, lipid kinases, and tethering complexes are reviewed, focusing on the model organism Saccharomyces cerevisiae.

Endolysosomal transport at the crossroads of cellular signaling

Where you start could determine where you end up A significant subset of the eukaryotic proteome must localize to multiple cellular compartments, necessitating the emergence of mechanisms to produce protein isoforms with distinct targeting sequences. Ly et al. reveal that alternative start-codon selection during translation initiation is a pervasive mechanism for dual localization of proteins by generating N-terminal isoforms.

Where you start could determine where you end up

Oxidative stress in metastatic progression Metastasis, the dissemination of tumor cells from the primary site to distant organs, remains the leading cause of cancer-related mortality. This complex, multistep process demands not only cellular motility but also adaptation to diverse and often hostile microenvironments. Among key stressors, oxidative stress driven by elevated levels of reactive oxygen species (ROS) emerges as both a threat to survival and a modulator of metastatic traits. Tumor cells face oxidative pressure throughout the metastatic cascade, requiring mechanisms to mitigate ROS-induced damage while harnessing redox signaling to support progression. This review outlines how cancer cells respond to oxidative stress during metastatic spread, delineates stepwise roles of ROS across the cascade, and explores therapeutic strategies to disrupt redox dynamics in metastatic disease.

Oxidative stress in metastatic progression

Revisiting oligodendrocytes in amyotrophic lateral sclerosis using human multicellular stem cell models Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive motor neuron degeneration, muscle wasting, and eventual paralysis. The clinical and genetic complexity along with rapid disease progression has hindered efforts to model the disease and develop effective treatments. Rodent models and human tissue studies point to dysfunction in oligodendrocyte lineage cells early in disease, although the underlying mechanisms remain unclear. Advances in stem cell research have introduced novel platforms to investigate cells in the oligodendrocyte lineage and their interactions with neurons and other glial cells in complex human genetic backgrounds. This Review summarizes the literature implicating oligodendrocyte lineage cells in ALS and discusses both the potential and limitations of in vitro-derived cultures to shed light on their vulnerabilities and cellular interactions.

Revisiting oligodendrocytes in amyotrophic lateral sclerosis using human multicellular stem cell models

Homeostasis of megakaryocytes: balancing tissue residency and consumptive platelet production Megakaryocytes (MKs) release platelets through a terminal event that results in the complete consumption of their cytoplasm. Once viewed as end-stage conductors of platelet biogenesis, MKs are now recognized as multifunctional regulators of the bone-marrow (BM) niche, supporting hematopoietic stem cell (HSC) maintenance, immune regulation, and extracellular matrix (ECM) remodeling. This multiple identity raises a fundamental question: how is MK homeostasis orchestrated to preserve a functional BM MK pool despite consumptive platelet production? Herein we review recent mechanistic insights into the biology of diverse MK functions, MK lineage development, and homeostatic regulation of megakaryopoiesis. Beyond classical systemic regulation, which maintains platelet counts within a physiological range by sensing the circulating platelet pool, we highlight BM tissue-level homeostatic circuits that treat the MK itself as the primary regulated variable.

Homeostasis of megakaryocytes: balancing tissue residency and consumptive platelet production

AMPK opens the door to organelle memory and longevity Nutrient sensors serve as sentinels of cellular energy status, relaying metabolic information to effectors that reprogram gene expression. Zhou et al. identified an AMP-activated protein kinase (AMPK)-NUP50 axis through which AMPK stabilizes the nucleoporin NUP50 to activate transcriptional programs promoting lipid catabolism and longevity. This redefines the nuclear pore complex (NPC) as a dynamic hormetic effector coupling energy sensing to transcriptional control.

AMPK opens the door to organelle memory and longevity

Mitochondrial transfer at the crossroads of cancer, stromal, and immune cells Mitochondria are organelles that are essential for their multiple roles in cell biology, including energy metabolism. Accumulating evidence has revealed that intercellular mitochondrial transfer occurs within the tumor microenvironment (TME). The mitochondrial transfer among the TME components can profoundly affect tumor progression, immune surveillance, and stromal remodeling. Importantly, cancer cells function not only as recipients but also as donors of mitochondria, underscoring the bidirectional nature of this process. This review summarizes the multifaceted roles of mitochondria in cancer cells, immune cells, and stromal cells, with particular emphasis on emerging insights into mitochondrial transfer. In addition, the current implications of mitochondria-targeting therapies and future challenges in this evolving field are highlighted.

Mitochondrial transfer at the crossroads of cancer, stromal, and immune cells