Journal of cell science最新文献

Crosstalk between tumor microenvironmental factors, such as extracellular matrix (ECM) stiffness and metabolic pathways, regulate cell invasive phenotype in cancer cells. ECM stiffening leads to the collapse of blood vessels leading to oxygen deprivation and nutrient stress. The individual and combined effect of these two factors on the mode of invasion of cancer cells remains poorly understood. Here, we show that in breast cancer cells, glucose deprivation induces a switch from an energy-demanding proteolytic mode of migration to an energy efficient non-proteolytic mode of migration. Energy demands met by OXPHOS and nuclear softening sustain this mode of migration. We further show that the energy sensor AMPK mediates this switch through transcriptional activation of the mechanoresponsive actin crosslinking protein α-actinin-4. Collectively, our results demonstrate how AMPK fine-tunes mode of invasion under nutrient constraints by transcriptional activation of α-actinin-4.

Epithelial tissues form protective barriers while supporting crucial functions, such as absorption and secretion. Their structural and functional integrity relies on adherens junctions, which coordinate migration and transmit forces between adjacent cells by connecting their actin cytoskeleton. In this study, we report the presence of an apical supracellular actin network in squamous epithelial cells. Using squamous carcinoma A431 cells as a model, we characterized this network composed of star-shaped actin structures interconnected by linear actin bundles that span multiple cells. We demonstrate that the formation and maintenance of the network require actomyosin contractility and intact adherens junctions, whereas tight junctions seem dispensable. Furthermore, this network dynamically reorganizes as cells migrate and preferentially aligns with the direction of movement. This contractile structure generates mechanical tension that extends across the apical surface of multiple cells. Our findings suggest that this supracellular actin network functions as a long-range force transmission device in squamous cells, advancing our understanding of the biomechanical properties of epithelia.

The hair follicle undergoes repeated cycles, with anagen representing the active growth phase. During anagen, transit amplifying cells within the germinative matrix at the follicle bulb drive rapid proliferation for hair growth. This region exhibits some of the highest mitotic rates observed in any tissue, offering a rare opportunity to study mitosis in its native epithelial context, previously studied only in cultured cell lines. We applied volume electron microscopy to intact chemically fixed hair follicles enabling exceptional ultrastructural preservation of the entire mini-organ. Morphometric analysis revealed stage-specific changes in chromosomal and organelle volume and spatial distribution, highlighting coordinated roles for the mitochondria, vesicles and endoplasmic reticulum, and enabled, to our knowledge, the first ultrastructure-based karyotype of ovine chromosomes. This work advances understanding of mitosis by resolving ultrastructure in a highly proliferative, spatially constrained epithelial microenvironment, demonstrating the power of serial block face scanning electron microscopy to bridge in vitro models and native tissue architecture.

Proteasome activator 200 (PA200; also known as PSME4) is upregulated in non-small cell lung cancer (NSCLC) and linked to poor prognosis. We have previously demonstrated that the overexpression of PA200 in NSCLC is associated with immune evasion and reduced responsiveness to immune checkpoint inhibitors. The cell autonomous function of PA200 in cancer growth, however, has not been solved. We here demonstrate that deletion of PA200 in two distinct lung cancer cell lines induced cell-specific alterations in proteasome composition and activities with a minor direct impact on overall proteasome activity. Deficiency of PA200 in lung cancer cells did not consistently alter tumor cell growth in vitro and in vivo. However, we observed concerted inhibition of tumor cell migration and invasion with conserved downregulation of the integrin ITGB3 and transcriptional dysregulation of multiple cell adhesion and extracellular matrix regulators. Our transcriptome profiling revealed a striking disparity in the transcriptional response to PA200 deletion in the two lung cancer cell lines. Together with our PA200 interactome analysis that uncovered an unexpected cell-dependent profile of PA200-interacting proteins, our data indicate that the function of PA200 is cell specific and depends on the cellular context. In conclusion, we here demonstrate that PA200 cell-autonomously regulates the invasive capacities of tumor cells thereby potentially promoting lung cancer spread and metastasis formation. This mechanism might add to PA200-related immune evasion and contribute to the observed poor prognosis of individuals with PA200-overexpressing lung cancer.

LAMP1 and LAMP2A (an isoform of LAMP2) are abundant proteins of late endosomal/lysosomal compartments that are often used interchangeably to label what is assumed to be the same organelle population, potentially obscuring distinct physiological roles. Here, we characterised the axonal transport dynamics of LAMP1- and LAMP2A-positive compartments in human induced pluripotent stem cell (hiPSC)-derived cortical neurons. We found that LAMP1-positive organelles move slower in the retrograde direction, pause more frequently, and display a broader anterograde velocity distribution than LAMP2A-positive vesicles, indicating distinct trafficking behaviours. Co-transport analysis revealed that ∼65% of motile LAMP1-positive organelles carry LAMP2A, and vice versa, with higher co-transport in the retrograde direction. To explore molecular differences underlying these behaviours, we performed proximity labelling using full-length LAMP1 or LAMP2A fused to the light-activated biotin ligase LOV-Turbo. This approach revealed largely overlapping interactomes, with LAMP2A-associated proteins forming a subset of the LAMP1 interactome and showing an enrichment for synaptic vesicle-related proteins. We further validated ZFYVE16 as a novel interactor of both compartments. Together, our findings indicate that LAMP1- and LAMP2A-positive organelles share overlapping molecular identities but represent functionally distinct axonal populations with divergent transport dynamics.

The proper formation of tissues and organs relies on precisely regulated differentiation and migration processes. In Drosophila embryos, the development of the midgut musculature requires coordinated movement of caudal visceral mesoderm (CVM) cells across the trunk visceral mesoderm (TVM). Here, we report that Beaten path (Beat) II proteins (Beat IIa and Beat IIb) are specifically expressed in CVM cells, whereas Sidestep IV (Side IV) is expressed in their substrate, the TVM. Both beat II and side IV mutants show similar migration defects, characterized by irregular migration patterns and abnormal cell distributions. At the end of embryogenesis, the midgut contains areas devoid of longitudinal muscles, resulting in a reduced number of longitudinal muscle fibres at larval stages. In cell-cell aggregation assays, Beat II proteins specifically interact with Side IV in trans. Moreover, ectopic expression of Side IV in trachea attracts migrating CVM cells and aligns them along tracheal branches. Altogether, these findings suggest that Side IV and Beat II proteins likely act as a ligand-receptor pair, providing guidance signals to assist in the formation of longitudinal muscle fibres of the midgut.

Mechanical coupling and chemical communication between cardiomyocytes are facilitated through a specialized adhesive structure called the intercalated disc (ICD). The ICD is essential for heart organization and contraction. Yet, the network of adhesion, adaptor and signaling proteins that form the ICD remains poorly defined. Here, we combined proximity labeling and quantitative mass spectrometry to identify proteins associated with the desmosomal cadherin desmoglein 2 (DSG2), in cultured neonatal cardiomyocytes. We identified over 300 proteins in the DSG2 interactome, half of which are shared with the N-cadherin (CDH2) interactome in cardiomyocytes. Proteins unique to DSG2 include connexin 43 and the plakin family of cytolinker proteins. Comparison of the cardiomyocyte DSG2 interactome with the interactomes of desmosomal proteins from epithelia revealed few shared proteins. In cardiomyocytes, plakoglobin and plakophilin 2 (PKP2) were the most abundant shared proteins between the DSG2 and CDH2 interactomes. We show that PKP2 is a dynamic protein whose membrane recruitment in cardiomyocytes is dependent on tension. Our analysis of the DSG2 interactome provides a crucial new dimension to the proteomic atlas of the essential molecular complexes required for cardiomyocyte adhesion.

Photoreceptors rely on microtubule (MT)-based transport within the connecting cilium to maintain cellular homeostasis. Mutations in RP1L1, a retina-specific doublecortin (DC) domain protein, cause inherited retinal disorders including occult macular dystrophy (OMD), yet the underlying mechanisms remain poorly defined. Here, we show that the RP1L1 R45W variant, prevalent in East Asian individuals with OMD, confers a toxic gain-of-function phenotype characterized by abnormally strong MT binding. Live-cell imaging revealed an approximately twofold increase in MT association relative to wild-type RP1L1. Molecular dynamics simulations indicated that R45W stabilizes RP1L1-α-tubulin interactions via cation-π contacts and reduced electrostatic repulsion. Remarkably, low concentrations of glycerol selectively disrupted these aberrant interactions, restoring MT binding to wild-type levels in both cellular and biochemical contexts. Our study elucidates a structural and mechanistic basis for RP1L1 R45W hyper-binding and demonstrates that small-molecule modulation of DC-domain interactions might provide a variant-specific therapeutic strategy for RP1L1-related retinopathies.