TRENDS IN CELL BIOLOGY

Emerging roles of palmitoylation in pyroptosis
Zhang N, Yang Y and Xu D
Pyroptosis is a lytic, proinflammatory type of programmed cell death crucial for the immune response to pathogen infections and internal danger signals. Gasdermin D (GSDMD) acts as the pore-forming protein in pyroptosis following inflammasome activation. While recent research has improved our understanding of pyroptosis activation and execution, many aspects regarding the molecular mechanisms controlling inflammasome and GSDMD activation remain to be elucidated. A growing body of literature has shown that S-palmitoylation, a reversible post-translational modification (PTM) that attaches palmitate to cysteine residues, contributes to multi-layered regulation of pyroptosis. This review summarizes the emerging roles of S-palmitoylation in pyroptosis research with a focus on mechanisms that regulate NLRP3 inflammasome and GSDMD activation.
MDM4 exon skipping upon dysfunctional ribosome assembly
Jansen J and Dobbelstein M
Recent studies revealed how nucleolar stress enhances MDM4 exon skipping and activates p53 via the ribosomal protein L22 (RPL22; eL22). Tumor-associated L22 mutations lead to full-length MDM4 synthesis, overcoming tumor suppression by p53. This forum article explores how MDM4 splicing patterns integrate stress signaling to take p53-dependent cell fate decisions.
The culture and application of circulating tumor cell-derived organoids
Pan C, Wang X, Yang C, Fu K, Wang F and Fu L
Circulating tumor cells (CTCs), which have the heterogeneity and histological properties of the primary tumor and metastases, are shed from the primary tumor and/or metastatic lesions into the vasculature and initiate metastases at remote sites. In the clinic, CTCs are used extensively in liquid biopsies for early screening, diagnosis, treatment, and prognosis. Current research focuses on using CTC-derived models to study tumor heterogeneity and metastasis, with 3D organoids emerging as a promising tool in cancer research and precision oncology. However, isolating and enriching CTCs from blood remains challenging due to their scarcity, exacerbated by the lack of an optimized culture medium for CTC-derived organoids (CTCDOs). In this review, we summarize the origin, isolation, enrichment, culture, validation, and clinical application of CTCs and CTCDOs.
POGK is a domesticated KRAB domain-containing transposable element with tumor suppressive functions in breast cancer
Mann KM
Transposable elements (TEs) account for 50% of the human genome and have essential functions as gene promoters. A subset of TEs is expressed in normal cells and differentially expressed in cancers, yet their biological significance is understudied. In a recent article, Tu et al. describe the tumor suppressive function of POGK, an expressed TE with a KRAB domain, and its cooperation with TRIM28 to repress ribosomal gene transcription in triple-negative breast cancer (TNBC).
Central role of the ER proteostasis network in healthy aging
Hetz C and Dillin A
Aging trajectories vary among individuals, characterized by progressive functional decline, often leading to disease states. One of the central hallmarks of aging is the deterioration of proteostasis, where the function of the endoplasmic reticulum (ER) is dramatically affected. ER stress is monitored and adjusted by the unfolded protein response (UPR); a signaling pathway that mediates adaptive processes to restore proteostasis. Studies in multiple model organisms (yeast, worms, flies, and mice) in addition to human tissue indicates that adaptive UPR signaling contributes to healthy aging. Strategies to improve ER proteostasis using small molecules and gene therapy reduce the decline of organ function during normal aging in mammals. This article reviews recent advances in understanding the significance of the ER proteostasis network to normal aging and its relationship with other hallmarks of aging such as senescence.
Increased O-GlcNAcylation connects metabolic to transcriptional reprogramming during pathophysiological cell activation
Very N, Staels B and Eeckhoute J
Increased protein O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) has emerged as a hallmark of mammalian cell activation, contributing to Warburg-like metabolic rewiring allowing the acquisition of new functionalities. Recent advances indicate that O-GlcNAcylation promotes the activity of transcriptional regulators driving gene expression reprogramming. This may offer new therapeutic opportunities in a broad spectrum of pathological conditions.
Dynamic rRNA modifications as a source of ribosome heterogeneity
Milenkovic I and Novoa EM
Ribosomal RNAs (rRNA) are the most abundant RNA molecules in almost all cell types. The general consensus in the field is that rRNA modifications are largely species-specific, with most previous works and databases solely stratifying modifications by the species of origin, without taking other levels of complexity into account. However, new evidence has emerged suggesting dynamic rRNA modifications may have additional layers of complexity and might play an important role in development and disease. In this review article, we summarize recent evidence supporting heterogeneity and dynamics in rRNA modifications in diverse biological contexts, challenging the simplistic view of 'one-species-one-rRNA-modification-pattern'. Moreover, we highlight how rRNA modification dynamics have been studied to date and how long-read sequencing methods can significantly improve our understanding of this largely unexplored yet highly abundant RNA family, across tissues, developmental stages, and diseases.
Proteome-wide CETSA reveals new step in apoptosis control
Lavrik IN and Ivanisenko NV
Apoptosis, a well-established program of cell death, is fundamental to all multicellular organisms. Recent studies of apoptosis initiation events using proteome-wide cellular thermal shift assay (CETSA) have revealed a novel regulatory mechanism involving the cleavage of nuclear substrates. This finding suggests a previously unrecognized amplification step in apoptosis occurring within the nucleus.
Cytoplasmic mtDNA clearance suppresses inflammatory immune responses
Yan C, Liu X, Xu H and Wang L
Upon various stresses, mtDNA leaks from mitochondria into the cytoplasm, leading to cellular dysfunction and inflammation, thereby exacerbating disease progression. The autophagy-lysosome pathway has emerged as a pivotal quality control mechanism for eliminating abnormal cytoplasmic mtDNA. This article summarizes the mechanisms underlying mtDNA-triggered inflammation and how cytoplasmic mtDNA is eliminated.
TFEB links the cGAS-STING pathway to lysosome biogenesis
Meng Y, Li X and Xu H
The cGAS-STING pathway senses the level of double-stranded (ds)DNA in the cytosol, and is required for innate immunity through its effector, TBK1. A recent study by Lv et al. reports that STING activation also simultaneously promotes lysosomal biogenesis by inducing nuclear translocation of the transcription factors TFEB/TFE3 independent of TBK1.
Regulation of leukemogenesis via redox metabolism
Zhang Z, Chen C, Li X, Zheng J and Zhao Y
Redox metabolism plays a central role in the cellular metabolism network, involves catabolic and anabolic reactions of diverse biomass, and determines the redox state of cells. It can be quantitatively and conveniently measured in living cells and organisms with genetically encoded fluorescent sensors, providing novel insights that cannot be readily acquired via conventional metabolic assays. Here, we review the recent progress on the regulation of leukemogenesis via redox metabolism, especially redox biosensor-based findings. In general, low reactive oxygen species levels and high reductive capacity promote leukemogenesis and chemotherapy resistance in leukemia cells, and acute leukemia cells rewire metabolism of glucose, fatty acids, and some amino acids, together with oxidative phosphorylation, to fuel energy production, support biomass-related synthesis, and survive oxidative stress. In summary, redox metabolism is a potential target for the development of novel therapies for leukemia or beneficial dietary regimens for patients with refractory and relapsed leukemia.
Crosstalk between mitochondria-ER contact sites and the apoptotic machinery as a novel health meter
Larrañaga-SanMiguel A, Bengoa-Vergniory N and Flores-Romero H
Mitochondria-endoplasmic reticulum (ER) contact sites (MERCS) function as transient signaling platforms that regulate essential cellular functions. MERCS are enriched in specific proteins and lipids that connect mitochondria and the ER together and modulate their activities. Dysregulation of MERCS is associated with several human pathologies including Alzheimer's disease (AD), Parkinson's disease (PD), and cancer. BCL-2 family proteins can locate at MERCS and control essential cellular functions such as calcium signaling and autophagy in addition to their role in mitochondrial apoptosis. Moreover, the BCL-2-mediated apoptotic machinery was recently found to trigger cGAS-STING pathway activation and a proinflammatory response, a recognized hallmark of these diseases that requires mitochondria-ER interplay. This review underscores the pivotal role of MERCS in regulating essential cellular functions, focusing on their crosstalk with BCL-2 family proteins, and discusses how their dysregulation is linked to disease.
Emerging roles of ECSIT in immunity and tumorigenesis
Yang S and Humphries F
Mitochondria are signaling hubs that produce immunomodulatory metabolites during the immune response. In addition, mitochondria also facilitate the recruitment and anchoring of immune signaling complexes during infection. Evolutionary conserved signaling intermediate in toll (ECSIT) was initially described as a positive regulator of the transcription factor Nuclear factor kappa-light chain enhancer of activated B cells (NF-κB). More recently, ECSIT has emerged as a regulator of bacterial clearance, mitochondrial reactive oxygen species (mROS), and mitophagy. In addition, ECSIT has been identified as a control point in responding to viral infection and tumorigenesis. Notably, ECSIT loss in different models and cell types has been found to lead to enhanced tumorigenesis. Thus, ECSIT functions as a metabolic tumor suppressor and limits cancer pathogenesis. In this review, we highlight the key functions and crosstalk mechanisms that ECSIT bridges between cell metabolism and immunity and focus then on the antitumor role of ECSIT independent of immunity.
Extracellular vesicles from the dead: the final message
Shi B, Phan TK and Poon IKH
Communication between dying and neighbouring cells is vital to ensure appropriate processes such as tissue repair or inflammation are initiated in response to cell death. As a mechanism to aid intercellular communication, cells undergoing apoptosis can release membrane-bound extracellular vesicles (EVs) called apoptotic-cell-derived EVs (ApoEVs) that can influence downstream processes through biomolecules within or on ApoEVs. ApoEVs are broadly categorised based on size as either large ApoEVs known as apoptotic bodies (ApoBDs) or small ApoEVs (s-ApoEVs). Notably, the mechanisms of ApoBD and s-ApoEV formation are different, and the functions of these two ApoEV subsets are distinct. This Review focuses on the biogenesis and functional properties of both ApoBDs and s-ApoEVs, particularly in the context of cell clearance, cell signalling and disease progression.
ERMCS Ca transmission fuels cell division
Madesh M, Vishnu N and Tomar D
Mitosis is a cellular process that demands high energy, but it was previously unclear how this process is linked with mitochondrial ATP production. Zhao et al. describe how during mitosis, the lamin B receptor migrates to the ER membrane to enhance ER-mitochondria contact sites, coordinating Ca surges that increase ATP production necessary for cell division.
Mechanisms suppressing noncoding translation
Kesner JS and Wu X
The majority of the DNA sequence in our genome is noncoding and not intended for synthesizing proteins. Nonetheless, genome-wide mapping of ribosome footprints has revealed widespread translation in annotated noncoding sequences, including long noncoding RNAs (lncRNAs), untranslated regions (UTRs), and introns of mRNAs. How cells suppress the translation of potentially toxic proteins from various noncoding sequences remains poorly understood. This review summarizes mechanisms for the mitigation of noncoding translation, including the BCL2-associated athanogene 6 (BAG6)-mediated proteasomal degradation pathway, which has emerged as a unifying mechanism to suppress the translation of diverse noncoding sequences in metazoan cells.
Senescent neutrophils: a hidden role in cancer progression
Rys RN and Calcinotto A
Neutrophils have recently received increased attention in cancer because they contribute to all stages of cancer. Neutrophils are so far considered to have a short half-life. However, a growing body of literature has shown that tumor-associated neutrophils (TANs) acquire a prolonged lifespan. This review discusses recent work surrounding the mechanisms by which neutrophils can persist in the tumor microenvironment (TME). It also highlights different scenarios for therapeutic targeting of protumorigenic neutrophils, supporting the idea that, in tumors, inhibition of neutrophil recruitment is not sufficient because these cells can persist and remain hidden from current interventions. Hence, the elimination of long-lived neutrophils should be pursued to increase the efficacy of standard therapy.
Sugar symphony: glycosylation in cancer metabolism and stemness
Varadharaj V, Petersen W, Batra SK and Ponnusamy MP
Glycosylation is a complex co-translational and post-translational modification (PTM) in eukaryotes that utilizes glycosyltransferases to generate a vast array of glycoconjugate structures. Recent studies have highlighted the role of glycans in regulating essential molecular, cellular, tissue, organ, and systemic biological processes with significant implications for human diseases, particularly cancer. The metabolic reliance of cancer, spanning tumor initiation, disease progression, and resistance to therapy, necessitates a range of uniquely altered cellular metabolic pathways. In addition, the intricate interplay between cell-intrinsic and -extrinsic mechanisms is exemplified by the communication between cancer cells, cancer stem cells (CSCs), cancer-associated fibroblasts (CAFs), and immune cells within the tumor microenvironment (TME). In this review article, we explore how differential glycosylation in cancer influences the metabolism and stemness features alongside new avenues in glycobiology.
Epigenetic regulation of hematopoietic stem cell fate
Meng Y and Nerlov C
Hematopoietic stem cells (HSCs) sustain blood cell production throughout the mammalian life span. However, it has become clear that at the single cell level a subset of HSCs is stably biased in their lineage output, and that such heterogeneity may play a key role in physiological processes including aging and adaptive immunity. Analysis of chromatin accessibility, DNA methylation, and histone modifications has revealed that HSCs with different lineage bias exhibit distinct epigenetic traits inscribed at poised, lineage-specific enhancers. This allows for lineage priming without initiating lineage-specific gene expression in HSCs, controlling lineage bias while preserving self-renewal and multipotency. Here, we review our current understanding of epigenetic regulation in the establishment and maintenance of HSC fate decisions under different physiological conditions.
Gut microbial metabolism in ferroptosis and colorectal cancer
Cui W, Hao M, Yang X, Yin C and Chu B
Ferroptosis is programmed cell death induced by iron-driven lipid peroxidation. Numerous studies have shown that ferroptosis is implicated in the progression of colorectal cancer (CRC) and has emerged as a promising strategy to combat therapy-resistant CRC. While the intrinsic antiferroptotic and proferroptotic pathways in CRC cells have been well characterized, extrinsic metabolism pathways regulating ferroptosis in CRC pathogenesis remain less understood. Emerging evidence shows that gut microbial metabolism is tightly correlated with the progression of CRC. This review provides an overview of gut microbial metabolism and discusses how these metabolites derived from intestinal microflora contribute to cancer plasticity through ferroptosis. Targeting gut microbe-mediated ferroptosis is a potential approach for CRC treatment.
Extracellular vesicle-mediated crosstalk in tumor microenvironment dominates tumor fate
Dou X, Feng C, Li J, Jiang E and Shang Z
The tumor microenvironment (TME) is a complex and heterogeneous system containing various cells cooperating and competing with each other. Extracellular vesicles (EVs) differing in form and content are important intercellular communication mediators in the TME. Previous studies have focused on the cargoes within EVs rather than on the donors from which they originate and the recipient cells that exert their effects. Therefore, we provide here a detailed overview of the important roles of EVs in shaping tumor fate, highlighting their various mechanisms of intercellular dialog within the TME. We evaluate recent advances and also raise unresolved challenges to provide new ideas for clinical treatment strategies using EVs.