Journal of cell science最新文献

The nucleus-vacuole junction (NVJ) in Saccharomyces cerevisiae is a multifunctional contact site between the membrane of the nuclear endoplasmic reticulum (ER) and the vacuole that has diverse roles in lipid metabolism, transfer and storage. Adaptation of NVJ functions to metabolic cues is mediated by a striking remodeling of the size and the proteome of the contact site, but the extent and the molecular determinants of this plasticity are not fully understood. Using microscopy-based screens, we monitored NVJ remodeling in response to glucose availability. We identified Pex31, Nsg1, Nsg2, Shr5, and Tcb1 as NVJ residents. Glucose starvation typically results in an expansion of the NVJ size and proteome. Pex31 shows an atypical behavior, being specifically enriched at the NVJ in high-glucose conditions. Loss of Pex31 uncouples NVJ remodeling from glucose availability, resulting in recruitment of glucose starvation-specific residents and NVJ expansion at glucose-replete conditions. Moreover, PEX31 deletion results in alterations of sterol ester storage and a remodeling of vacuolar membranes that phenocopy glucose starvation responses. We conclude that Pex31 has a role in metabolic adaptation of the NVJ.

Chromera velia is a photosynthetic, free-living alga closely related to the apicomplexan parasites, a phylum of intracellular pathogens responsible for many devastating diseases, including malaria, cryptosporidiosis, and toxoplasmosis. With molecular and cellular landmarks clearly related to but distinguishable from those found in apicomplexan parasites, Chromera provides an opportunity to investigate the evolutionary origin of the structures and processes needed for intracellular parasitism. However, tools for defining localization and functions of gene products do not exist for Chromera, which creates a major bottleneck for exploring its biology. Here we report two major advances in exploring the cell biology of this free-living relative of a large group of intracellular parasites: 1) successful cell transformation, and 2) the implementation of expansion microscopy. The initial analysis enabled by these tools generated new insights into subcellular organization in different life stages of Chromera. These new developments boost the potential of Chromera as a model system for understanding the evolution of parasitism in apicomplexans.

Fanconi anemia is a rare genetic disease caused by the loss of function of one of the 23 associated genes and is characterized by bone marrow failure, cancer predisposition and developmental defects. The proteins encoded by these genes (FANC proteins) mainly function in DNA damage response and repair. Although FANC deficiency has multiple effects on the regulation of lipid metabolism, the molecular function of FANC proteins in the context of Fanconi anemia pathology remains unclear. In the present study, we demonstrate that FANCD2, a key component of FANC proteins, interacts with factors involved in fatty acid biosynthesis or sphingolipid metabolism and that FANCD2 deficiency downregulates the cellular levels of fatty acids. Moreover, a portion of FANCD2 is localized to nuclear lipid droplets in response to oleic acid (OA) treatment. These subcellular dynamics are independent of FANCD2 monoubiquitylation, which is essential for the DNA damage response. Collectively, these findings demonstrate that FANCD2 responds to not only DNA damage but also OA exposure, providing insights into the pathogenesis of lipid dysregulation in Fanconi anemia.

Growth signals and immune responses in cancer typically originate in the same compartments. In early stages of tumor development, inflammatory cells trigger responses against growing cancers. At a molecular level, it is unclear how the innate immune system recognizes tumorigenesis. At later stages, cancer cells resist cell death and evade immune detection, thereby suppressing anti-tumor responses and promoting cancer hallmarks. Often, chronic inflammatory responses become tumor friendly and incline towards tumorigenesis disturbing metabolic signaling, thereby rewiring nutritional supply for cancer growth. The precise connecting link between cancer, nutrition and metabolism remains unclear. Drosophila provides an ideal platform to explore the links between hyperactive immune signaling, defective fat metabolism and pseudotumor formation. Therefore, we examined the effects of methotrexate on these pathophysiological processes in larvae with hyperactive Toll/NF-κB pathway. We determined that both chemical (methotrexate) and genetic [rescue of Ubc9-/- mutants by introducing a wild-type copy of Cactus (negative regulator of the Toll pathway)] interventions alleviated abnormalities associated with Toll/NF-κB hyperactivity and its influence on insulin signaling. Our study underscores drug repurposing studies and provides insights into how immune-metabolic crosstalk rewires inflammation-driven tumorigenesis.

Krüppel-like factor 1 [KLF1; also known as erythroid Krüppel-like factor (EKLF)] is a C2H2 zinc finger transcription factor that plays a crucial role in all aspects of erythropoiesis. Mutations in KLF1 lead to diverse phenotypes ranging from mild to severe anemias. Individuals with a heterozygous E325K mutation [congenital dyserythropoietic anemia (CDA) type IV] exhibit impaired erythroid terminal differentiation and increased presence of binucleate erythroblasts. We have previously shown that KLF1 is necessary for cell cycle exit and enucleation in mouse primary cells. In the present study, we discovered that genes involved in cell motility, cell division and mitotic pathways are all directly regulated by KLF1. Klf1-/- cells exhibit increased numbers of binucleated erythroblasts and DNA bridges, and differentiating Klf1-/- erythroblasts display an increased percentage of cytokinesis failure events and defective microtubule bundling. Klf1-/- erythroblasts produce frequent aberrant F-actin-rich membrane protrusions and anucleate cell fragments. Human CDA type IV cells exhibit similar patterns of dysregulation of cytokinesis and cell motility genes. Collectively, we show that KLF1 is necessary for maintaining the integrity of erythroid cell divisions by direct regulation of genes involved in cytokinesis and motility pathways during terminal erythroid differentiation.

Sphingolipids are essential for cell membrane structure and the regulation of organelle functions. Sphingolipid synthesis requires the coordinated activity of multiple organelles, including the endoplasmic reticulum, Golgi, lysosomes and mitochondria, which are connected via membrane contact sites. Metabolic remodeling of sphingolipid pathways is observed in aging and numerous age-related disorders. However, numerous studies have highlighted the complex and species-specific roles of sphingolipid metabolism in aging. In budding yeast, inhibition of sphingolipid synthesis extends lifespan by a mechanism that is poorly understood. Recent findings suggest that inhibition of sphingolipid synthesis in cells mimics methionine restriction, a condition known to extend lifespan across different experimental models. However, how sphingolipid remodeling alters cellular methionine levels, and whether this directly influences aging, remains unclear. In this Review, we explore the roles of sphingolipids in organelle function, highlighting their metabolic connections to methionine restriction and aging.

Hormones typically regulate physiology by modulating transcriptional programmes. However, post-transcriptional mechanisms offer an additional layer of control, enabling rapid and context-specific regulation of gene expression. Among these mechanisms, cytoplasmic ribonucleoprotein granules (RNPGs) - a type of membraneless condensate that includes stress granules and processing bodies - have emerged as dynamic regulators of RNA fate. These granules could serve as integrative hubs that modulate mRNA translation, stability and storage in response to endocrine signals, thereby fine-tuning hormone-driven cellular responses. This Hypothesis article proposes that hormonal cues can influence RNPG assembly, composition and physical state through transcriptional regulation of granule components or via rapid, non-genomic mechanisms, including kinase cascades or ligand-induced conformational changes in granule proteins. In turn, RNPGs can regulate hormone-driven cellular responses by selectively sequestering, releasing or degrading specific mRNAs. Furthermore, these granules can regulate hormonal pathways by controlling the availability of hormone-related transcripts and signalling components, establishing a bidirectional regulatory network. This dynamic interaction, illustrated by examples from plants, invertebrates and mammals, is hypothesised to add complexity and versatility to endocrine regulation, enabling rapid and adaptive responses to physiological demands.

We present evidence that the association of the epithelial (E)-cadherin (CHD1) extracellular domain and epidermal growth factor receptor (EGFR, ErbB1) is obligatory for cadherin force transduction signaling. E-cadherin and EGFR associate at cell surfaces, independent of their cytoplasmic domains, and tension on E-cadherin activates EGFR signaling. Using engineered E-cadherin mutants that disrupt co-immunoprecipitation with EGFR, but not adhesion, we show that the hetero-receptor complex is required to mechanically activate signaling and downstream cytoskeletal remodeling at cadherin adhesions. The mutants localized the essential region on E-cadherin to domain 4 of the extracellular region (EC4). The ectodomain is also required for hetero-receptor colocalization at intercellular junctions. Although the E-cadherin mutants disrupt EGFR signaling, integrin pre-activation together with tension rescues cytoskeletal reinforcement at cadherin adhesions, confirming the role of integrins in intercellular force transduction. Furthermore, although E-cadherin suppresses EGFR-mediated proliferation, in response to extracellular matrix stiffening, the force-sensitive hetero-receptor complex regulates growth factor-dependent epithelial proliferation. These findings support the hypothesis that E-cadherin complexes with EGFR are mechano-switches at cell-cell contacts that directly couple intercellular force fluctuations to mitogen-dependent signaling.

The nucleus must maintain shape and integrity to protect the function of the genome. Nuclear blebs are deformations identified by decreased DNA density that commonly lead to rupture. Lamin B levels often vary drastically between blebs. We tracked rupture via time-lapse imaging of nuclear localization sequence (NLS)-GFP immediately followed by immunofluorescence imaging of lamins and known rupture markers. We find that lamin B1 loss consistently marks ruptured nuclear blebs better than lamin A/C, emerin and cGAS. Visualizing post-rupture lamin B1 loss and emerin enrichment reveals that cell lines display widely different propensities for nuclear bleb rupture. To determine how rupture affects DNA damage, we time-lapse-imaged ruptured and unruptured blebs, then conducted immunofluorescence on the same cells for DNA damage markers γH2AX and 53BP1. We find that DNA damage is increased in blebbed nuclei independently of rupture. This was verified in blebbed LNCaP nuclei, which do not rupture and maintain lamin B1, but still show increased DNA damage. Thus, we confirm that lamin B is the most consistent marker of nuclear rupture, and that blebbed nuclei have increased DNA damage regardless of rupture.