Journal of cell science最新文献

In the heart, cardiomyocyte cell-matrix and cell-cell adhesions reorganize in response to increased cardiac demand and growth. Vinculin (VCL), a mechanosensitive adaptor protein, links filamentous actin to cell-matrix and cell-cell adhesions. Yet how VCL regulates remodeling of the two adhesion systems is poorly understood. Here, we investigate the role of phosphorylation at VCL tyrosine residue 822 (pY822) in cardiomyocyte adhesion and heart function. VCL Y822 phosphorylation levels peaked during adhesion remodeling in the developing heart and were reduced as adhesions matured postnatally. VCL pY822 levels also increased in the adult heart following injury. We mutated Vcl Y822 to phenylalanine (Y822F) in the mouse to determine the in vivo function of pY822. Homozygous mutant Vcl Y822F mice were viable but exhibited cardiac dysfunction at 28 weeks. We found that VCL pY822 regulated cardiomyocyte cell-matrix and cell-cell adhesions during postnatal heart development. Defects in cell-cell adhesion organization were also observed in cultured Vcl Y822F cardiomyocytes. Our results demonstrate that VCL Y822 phosphorylation regulates adhesion organization in cardiomyocytes, highlighting the importance of post-translational modification in modulating VCL function in the heart.

Regulation of Lamin A/C levels and distribution is crucial for nuclear integrity and mechanotransduction via the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex. Dysregulation of Lamin A/C correlates with poor cancer prognosis, and its levels determine sensitivity to the microtubule-stabilising drug paclitaxel. Paclitaxel is well-known for disrupting mitosis, yet it also reduces tumour size in slow-dividing tumours, indicating an additional, poorly characterised interphase mechanism. Here, we reveal that paclitaxel induces nuclear aberrations in interphase through SUN2-dependent Lamin A/C disruption. Using advanced optical imaging and electron cryo-tomography, we show the formation of aberrant microtubule-vimentin bundles during paclitaxel treatment, which coincides with nuclear deformation and altered Lamin A/C protein levels and organisation at the nuclear envelope. SUN2 is required for Lamin A/C reduction in paclitaxel and is in turn regulated by polyubiquitination. Furthermore, Lamin A/C expression levels determine not only cell survival during treatment but also recovery after drug removal. Our findings support a model in which paclitaxel acts through both defective mitosis and interphase nuclear-cytoskeletal disruption, providing additional mechanistic insights into a widely used anticancer drug.

Throughout the life cycle of the unicellular parasite Trypanosoma brucei, its single flagellum remains laterally attached to the cell body by FLA and FLABP proteins, even as the parasite differentiates from the bloodstream form (BSF), found in the mammalian host, to the procyclic form (PCF), in the insect midgut. This differentiation is accompanied by changes in the dominant surface coat protein from the variable surface glycoprotein to procyclins. There are stage-specific variants of the FLA and FLABP proteins, with FLA2 and FLA2BP found in BSFs and FLA1 and FLA1BP in PCFs. Yet, how these proteins maintain flagellum attachment during the differentiation from BSFs to PCFs and the accompanying change in surface coat environment is unknown. Here, we used a double-induction system to test whether FLA2 and FLA2BP can maintain flagellum attachment in cells expressing procyclins. While FLA2 compensated for the loss of FLA1, FLA2BP was mis-localised in PCFs and could not compensate for the loss of FLA1BP. Interestingly, when FLA2 was expressed alongside FLA2BP, FLA2BP localised to the FAZ and flagellum attachment was maintained. Thus, we conclude that FLA2 and FLA2BP, together, will maintain flagellum attachment as the surface coat environment changes during BSF to PCF differentiation.

Microtubule organization plays a central role in cell differentiation, orchestrating essential processes such as cell polarization, mechanotransduction, organelle positioning, and intracellular transport. A hallmark of many differentiated cells is the transition from a centrosomal to a non-centrosomal microtubule-organizing center (MTOC). Here, we demonstrate that both centrosomal and nuclear envelope (NE)-associated MTOCs coexist in osteoclasts. We show that the key players for NE-MTOC formation, AKAP6β and nesprin-1α, previously considered muscle-specific, are upregulated during osteoclast differentiation, suggesting a conserved role in NE-MTOC assembly across cell types. Targeted depletion of AKAP6 in RAW264.7-derived osteoclasts led to the displacement of the Golgi and MTOC-associated proteins PCM1, pericentrin, and CDK5RAP2 from the NE, while their centrosomal localization remained intact. This selectively impaired microtubule nucleation from the NE without disrupting centrosomal microtubule activity, enabling a functional dissection of the two MTOCs. Loss of NE-MTOC activity, by AKAP6 depletion, impaired podosome formation and significantly reduced bone resorption capacity, highlighting the distinct and essential role of NE-derived microtubules in osteoclast function.

A significant challenge in Drosophila centriole biology is its small size. Advanced super-resolution techniques have provided valuable insights, but require specialized equipment and can be difficult to implement in tissues. Expansion Microscopy (ExM) offers an accessible alternative, yet its application in Drosophila centriole research has been sparse. We provide an ExM protocol for cultured S2 cells and fly tissues that revealed new insights into pro-centriole biology. In S2 cells we document overduplication in the form of the classic "rosettes", while in spermatids we uncover an unexpected movement of the pro-centriole-like structure (PCL). ExM has also refined existing molecular models. In S2 cells we document the distal tip protein Cep97 as a ring, which clarifies its role in capping the growing centriole. In spermatids, we spatially segregated the inner nuclear membrane protein Spag4 and the cytoplasmic protein Yuri, which led to the new hypothesis that they play independent roles at the centriole-nucleus contact site. Finally, we show that our ExM protocol is a hypothesis-generator and discovery tool applicable beyond Drosophila centrioles by imaging synaptonemal complexes in the Plodia interpunctella moth.

Cell shape regulation is important for many biological processes. Some cell shape-regulating proteins harbor mechanoresponsive properties that enable them to sense and respond to mechanical cues. In Dictyostelium discoideum, mechanoresponsive network proteins like Myosin II, Cortexillin I and IQGAP1 assemble in the cytoplasm into macromolecular complexes, which we term Contractility Kits. In our previous studies, we identified the RNA-binding protein, RNP1A, as a genetic interactor with the cell's cytoskeletal machinery and as a biochemical interactor of Cortexillin I, using in vivo fluorescence cross-correlation spectroscopy. In this study, the rnp1A knockdown cells have reduced cell proliferation, reduced adhesion, defective cytokinesis, and a gene expression profile that indicates rnp1A knockdown cells shift away from the vegetative growth state. RNP1A binds transcripts some of which encode proteins involved in macropinocytosis, a critical cell shape change process. Loss of other CK proteins leads to macropinocytotic defects characterized by reduced macropinocytotic crown size. RNP1A interacts with IQGAP1, leading to crosstalk during macropinocytosis. Overall, RNP1A binds transcripts and contributes to cell mechanics and cell shape change processes through interactions with Contractility Kit proteins.

Replication stress involves the slowing or stalling of the replication fork as DNA is copied during S phase. This stress can drive genomic instability, a cancer hallmark. RNA:DNA hybrids, such as R-loops and single genome-embedded ribonucleotides, are significant sources of replication stress. RNA:DNA hybrid homeostasis must therefore be tightly regulated through prevention and removal. Ribonuclease H2 (RNase H2) functions both in R-loop removal and excision of single ribonucleotides from genomic DNA. Recent research has generated new mechanistic insights into the functions of RNase H2 in the replication stress response, and implicated both loss and overexpression of RNase H2 in cancer development and therapy response. These findings help generate new models but also raise new questions. This Review explores the contribution of RNA:DNA hybrids to replication stress, the involvement of RNase H2 in regulating these structures, and the emerging roles of RNase H2 in replication stress response and cancer.

Between 2008 and 2025, four of The Company of Biologists' journals - Development, Journal of Cell Science (JCS), Journal of Experimental Biology (JEB) and Disease Models & Mechanisms (DMM) - offered Travelling Fellowships of up to £3000 to enable early-career researchers (ECRs) to make collaborative visits to other laboratories. Over the past few decades, these fellowships have enabled researchers within the communities served by the Company journals from all over the world to gain cutting-edge research experience, expand their professional networks and publish their findings - all of which has helped some of the former recipients to set up their own labs later in life. In this article, I trace the history of the Company's Travelling Fellowships scheme, initiated by Development and later expanded to include JCS, JEB and DMM, while also highlighting testimonials from former fellowship recipients and looking ahead to the Company's future plans.

Cell migration is a complex process hallmarked by front-to-back cell polarity that is established by the highly dynamic actin cytoskeleton. Branched actin polymerization creates a lamellipodium at the leading edge of the cell, while the contractile acto-myosin cytoskeleton is present at the lagging edge. Rap2, a Ras GTPase family member, has previously been reported to localize to the lamellipodium as a result of ubiquitylation by a Rab40-Cullin5 E3 ubiquitin ligase complex (Rab40/CRL5). However, how Rap2 functions and how ubiquitylation targets Rap2 to the lamellipodium remained unclear. Here, we demonstrate that Rap2 is recruited to retracting lamellipodia ruffles where it inhibits RhoA, likely through interactions with ARHGAP29, and regulates lamellipodia dynamics, thus facilitating cell migration. Furthermore, using a variety of genetic and pharmacological techniques, we show that Rab40/CRL5-dependent ubiquitylation is required for guanine-nucleotide-exchange factor (GEF)-dependent Rap2 activation, a necessary step for Rap2 targeting to the lamellipodium membrane. As such, we demonstrate how this unique ubiquitylation and activation of Rap2 regulates lamellipodia actin dynamics during cell migration.

Mitochondrial transfer to recipient cells triggers a respiratory burst by increasing ATP production and cellular energy metabolism. However, its impact on intracellular metabolic shifts remains unclear. This study introduces a novel methodological approach and new biological insights into mitochondrial dynamics in cancer cells. We developed fluorescence-lifetime imaging microscopy (FLIM) intensity-based image segmentation (FIBIS), an algorithm optimized for single-mitochondrion analysis. FIBIS utilizes NADH autofluorescence, eliminating the need for biomarker staining, and improves mitochondrial detection accuracy by 35% compared to raw intensity thresholding. This method is particularly effective for analyzing dynamic mitochondria in live cells. Using FIBIS, we show that normal epithelial mitochondria uptake alters the free NADH-to-bound NADH ratio, increasing bound NADH in both estrogen- and progesterone receptor-positive and triple-negative breast cancer cells. Additionally, mitochondrial transfer enhances cancer cell sensitivity to oxidative stress-inducing anti-cancer drugs, suggesting a potential restoration of normal reactive oxygen species tolerance. Overall, FIBIS is a robust methodological approach that uses the phasor-FLIM technique to analyze NADH levels (free and bound) at the single-mitochondrion level, providing new biological insights into transferred mitochondrial dynamics in cancer cells.