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The actin cytoskeleton plays multiple roles in structural colour formation in butterfly wing scales.Nature Communications May 2024Vivid structural colours in butterflies are caused by photonic nanostructures scattering light. Structural colours evolved for numerous biological signalling functions...
Vivid structural colours in butterflies are caused by photonic nanostructures scattering light. Structural colours evolved for numerous biological signalling functions and have important technological applications. Optically, such structures are well understood, however insight into their development in vivo remains scarce. We show that actin is intimately involved in structural colour formation in butterfly wing scales. Using comparisons between iridescent (structurally coloured) and non-iridescent scales in adult and developing H. sara, we show that iridescent scales have more densely packed actin bundles leading to an increased density of reflective ridges. Super-resolution microscopy across three distantly related butterfly species reveals that actin is repeatedly re-arranged during scale development and crucially when the optical nanostructures are forming. Furthermore, actin perturbation experiments at these later developmental stages resulted in near total loss of structural colour in H. sara. Overall, this shows that actin plays a vital and direct templating role during structural colour formation in butterfly scales, providing ridge patterning mechanisms that are likely universal across lepidoptera.
Topics: Animals; Butterflies; Wings, Animal; Actin Cytoskeleton; Pigmentation; Actins; Color; Animal Scales
PubMed: 38769302
DOI: 10.1038/s41467-024-48060-3 -
The Journal of Investigative Dermatology May 2024Keloids are a severe form of scarring for which the underlying mechanisms are poorly understood, and treatment options are limited or inconsistent. Although...
Keloids are a severe form of scarring for which the underlying mechanisms are poorly understood, and treatment options are limited or inconsistent. Although biomechanical forces are potential drivers of keloid scarring, the direct cellular responses to mechanical cues have yet to be defined. The aim of this study was to examine the distinct responses of normal dermal fibroblasts and keloid-derived fibroblasts (KDFs) to changes in extracellular matrix stiffness. When cultured on hydrogels mimicking the elasticity of normal or scarred skin, KDFs displayed greater stiffness-dependent increases in cell spreading, F-actin stress fiber formation, and focal adhesion assembly. Elevated actomyosin contractility in KDFs disrupted the normal mechanical regulation of extracellular matrix deposition and conferred resistance on myosin inhibitors. Transcriptional profiling identified mechanically regulated pathways in normal dermal fibroblasts and KDFs, including the actin cytoskeleton, Hippo signaling, and autophagy. Further analysis of the autophagy pathway revealed that autophagic flux was intact in both fibroblast populations and depended on actomyosin contractility. However, KDFs displayed marked changes in lysosome organization and an increase in lysosomal exocytosis, which was mediated by actomyosin contractility. Together, these findings demonstrate that KDFs possess an intrinsic increase in cytoskeletal tension, which heightens the response to extracellular matrix mechanics and promotes lysosomal exocytosis.
PubMed: 38763173
DOI: 10.1016/j.jid.2024.04.015 -
European Journal of Cell Biology Jun 2024Nuclear receptor Nur77 plays a pivotal role in immune regulation across various tissues, influencing pro-inflammatory signaling pathways and cellular metabolism. While...
Nuclear receptor Nur77 plays a pivotal role in immune regulation across various tissues, influencing pro-inflammatory signaling pathways and cellular metabolism. While cellular mechanics have been implicated in inflammation, the contribution of Nur77 to these mechanical processes remains elusive. Macrophages exhibit remarkable plasticity in their morphology and mechanics, enabling them to adapt and execute essential inflammatory functions, such as navigating through inflamed tissue and pathogen engulfment. However, the precise regulatory mechanisms governing these dynamic changes in macrophage mechanics during inflammation remain poorly understood. To establish the potential correlation of Nur77 with cellular mechanics, we compared bone marrow-derived macrophages (BMDMs) from wild-type (WT) and Nur77-deficient (Nur77-KO) mice and employed cytoskeletal imaging, single-cell acoustic force spectroscopy (AFS), migration and phagocytosis assays, and RNA-sequencing. Our findings reveal that Nur77-KO BMDMs exhibit changes to their actin networks compared to WT BMDMs, which is associated with a stiffer and more rigid phenotype. Subsequent in vitro experiments validated our observations, showcasing that Nur77 deficiency leads to enhanced migration, reduced adhesion, and increased phagocytic activity. The transcriptomics data confirmed altered mechanics-related pathways in Nur77-deficient macrophage that are accompanied by a robust pro-inflammatory phenotype. Utilizing previously obtained ChIP-data, we revealed that Nur77 directly targets differentially expressed genes associated with cellular mechanics. In conclusion, while Nur77 is recognized for its role in reducing inflammation of macrophages by inhibiting the expression of pro-inflammatory genes, our study identifies a novel regulatory mechanism where Nur77 governs macrophage inflammation through the modulation of expression of genes involved in cellular mechanics. Our findings suggest that immune regulation by Nur77 may be partially mediated through alterations in cellular mechanics, highlighting a potential avenue for therapeutic targeting.
Topics: Nuclear Receptor Subfamily 4, Group A, Member 1; Animals; Macrophages; Mice; Mice, Knockout; Mice, Inbred C57BL; Phagocytosis; Cell Movement; Inflammation
PubMed: 38763048
DOI: 10.1016/j.ejcb.2024.151419 -
Clinical Proteomics May 2024The early identification of patients at high-risk for end-stage renal disease (ESRD) is essential for providing optimal care and implementing targeted prevention...
BACKGROUND
The early identification of patients at high-risk for end-stage renal disease (ESRD) is essential for providing optimal care and implementing targeted prevention strategies. While the Kidney Failure Risk Equation (KFRE) offers a more accurate prediction of ESRD risk compared to static eGFR-based thresholds, it does not provide insights into the patient-specific biological mechanisms that drive ESRD. This study focused on evaluating the effectiveness of KFRE in a UK-based advanced chronic kidney disease (CKD) cohort and investigating whether the integration of a proteomic signature could enhance 5-year ESRD prediction.
METHODS
Using the Salford Kidney Study biobank, a UK-based prospective cohort of over 3000 non-dialysis CKD patients, 433 patients met our inclusion criteria: a minimum of four eGFR measurements over a two-year period and a linear eGFR trajectory. Plasma samples were obtained and analysed for novel proteomic signals using SWATH-Mass-Spectrometry. The 4-variable UK-calibrated KFRE was calculated for each patient based on their baseline clinical characteristics. Boruta machine learning algorithm was used for the selection of proteins most contributing to differentiation between patient groups. Logistic regression was employed for estimation of ESRD prediction by (1) proteomic features; (2) KFRE; and (3) proteomic features alongside KFRE.
RESULTS
SWATH maps with 943 quantified proteins were generated and investigated in tandem with available clinical data to identify potential progression biomarkers. We identified a set of proteins (SPTA1, MYL6 and C6) that, when used alongside the 4-variable UK-KFRE, improved the prediction of 5-year risk of ESRD (AUC = 0.75 vs AUC = 0.70). Functional enrichment analysis revealed Rho GTPases and regulation of the actin cytoskeleton pathways to be statistically significant, inferring their role in kidney function and the pathogenesis of renal disease.
CONCLUSIONS
Proteins SPTA1, MYL6 and C6, when used alongside the 4-variable UK-KFRE achieve an improved performance when predicting a 5-year risk of ESRD. Specific pathways implicated in the pathogenesis of podocyte dysfunction were also identified, which could serve as potential therapeutic targets. The findings of our study carry implications for comprehending the involvement of the Rho family GTPases in the pathophysiology of kidney disease, advancing our understanding of the proteomic factors influencing susceptibility to renal damage.
PubMed: 38762513
DOI: 10.1186/s12014-024-09486-5 -
The Science of the Total Environment Jul 2024The contamination of marine and freshwater environments by nanoplastics is considered a global threat for aquatic biota. Taking into account the most recent...
The contamination of marine and freshwater environments by nanoplastics is considered a global threat for aquatic biota. Taking into account the most recent concentration range estimates reported globally and recognizing a knowledge gap in polystyrene nanoplastics (PS-NPs) ecotoxicology, the present work investigated the harmful effects of 20 nm and 80 nm PS-NPs, at increasing biological complexity, on the rainbow trout Oncorhynchus mykiss RTG-2 and gilthead seabream Sparus aurata SAF-1 cell lines. Twenty nm PS-NPs exerted a greater cytotoxicity than 80 nm ones and SAF-1 were approximately 4-fold more vulnerable to PS-NPs than RTG-2. The engagement of PS-NPs with plasma membranes was accompanied by discernible uptake patterns and morphological alterations along with a nuclear translocation already within a 30-min exposure. Cells were structurally damaged only by the 20 nm PS-NPs in a time-dependent manner as indicated by distinctive features of the execution phase of the apoptotic cell death mechanism such as cell shrinkage, plasma membrane blebbing, translocation of phosphatidylserine to the outer leaflet of the cell membrane and DNA fragmentation. At last, functional analyses unveiled marked transcriptional impairment at both sublethal and lethal doses of 20 nm PS-NPs, with the latter impacting the "Steroid biosynthesis", "TGF-beta signaling pathway", "ECM-receptor interaction", "Focal adhesion", "Regulation of actin cytoskeleton" and "Protein processing in endoplasmic reticulum" pathways. Overall, a distinct ecotoxicological hazard of PS-NPs at environmentally relevant concentrations was thoroughly characterized on two piscine cell lines. The effects were demonstrated to depend on size, exposure time and model, emphasizing the need for a comparative evaluation of endpoints between freshwater and marine ecosystems.
Topics: Animals; Water Pollutants, Chemical; Polystyrenes; Fresh Water; Transcriptome; Oncorhynchus mykiss; Sea Bream; Cell Line; Ecotoxicology; Seawater; Nanoparticles
PubMed: 38761939
DOI: 10.1016/j.scitotenv.2024.173159 -
Journal of the American Heart... May 2024Many cardiomyopathy-associated pathogenic variants are heterozygous truncations, and pathogenic variants are associated with arrhythmias. Arrhythmia triggers in...
BACKGROUND
Many cardiomyopathy-associated pathogenic variants are heterozygous truncations, and pathogenic variants are associated with arrhythmias. Arrhythmia triggers in filaminopathy are incompletely understood.
METHODS AND RESULTS
We describe an individual with biallelic pathogenic variants, p.Arg650X and c.970-4A>G, with peripartum cardiomyopathy and ventricular arrhythmias. We also describe clinical findings in probands with variants including Val2715fs87X, Glu2458Serfs71X, Phe106Leu, and c.970-4A>G with hypertrophic and dilated cardiomyopathy, atrial fibrillation, and ventricular tachycardia. Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were generated. The truncation, Arg650X/c.970-4A>G, showed a marked reduction in filamin C protein consistent with biallelic loss of function mutations. To assess loss of filamin C, gene editing of a healthy control iPSC line was used to generate a homozygous disruption in the actin binding domain. Because filamin C has been linked to protein quality control, we assessed the necessity of filamin C in iPSC-CMs for response to the proteasome inhibitor bortezomib. After exposure to low-dose bortezomib, null iPSC-CMs showed an increase in the chaperone proteins BAG3, HSP70 (heat shock protein 70), and HSPB8 (small heat shock protein B8) and in the autophagy marker LC3I/II. null iPSC-CMs had prolonged electric field potential, which was further prolonged in the presence of low-dose bortezomib. null engineered heart tissues had impaired function after low-dose bortezomib.
CONCLUSIONS
pathogenic variants associate with a predisposition to arrhythmias, which can be modeled in iPSC-CMs. Reduction of filamin C prolonged field potential, a surrogate for action potential, and with bortezomib-induced proteasome inhibition, reduced filamin C led to greater arrhythmia potential and impaired function.
Topics: Filamins; Humans; Proteostasis; Female; Induced Pluripotent Stem Cells; Arrhythmias, Cardiac; Myocytes, Cardiac; Cardiomyopathies; Male; Adult; Mutation; Bortezomib
PubMed: 38761081
DOI: 10.1161/JAHA.123.030467 -
Life Science Alliance Aug 2024Dynamic rearrangements of the F-actin cytoskeleton are a hallmark of tumor metastasis. Thus, proteins that govern F-actin rearrangements are of major interest for...
Dynamic rearrangements of the F-actin cytoskeleton are a hallmark of tumor metastasis. Thus, proteins that govern F-actin rearrangements are of major interest for understanding metastasis and potential therapies. We hypothesized that the unique F-actin binding and bundling protein SWAP-70 contributes importantly to metastasis. Orthotopic, ectopic, and short-term tail vein injection mouse breast and lung cancer models revealed a strong positive dependence of lung and bone metastasis on SWAP-70. Breast cancer cell growth, migration, adhesion, and invasion assays revealed SWAP-70's key role in these metastasis-related cell features and the requirement for SWAP-70 to bind F-actin. Biophysical experiments showed that tumor cell stiffness and deformability are negatively modulated by SWAP-70. Together, we present a hitherto undescribed, unique F-actin modulator as an important contributor to tumor metastasis.
Topics: Animals; Actins; Mice; Humans; Female; Cell Line, Tumor; Neoplasm Metastasis; Breast Neoplasms; Lung Neoplasms; Microfilament Proteins; Cell Movement; Actin Cytoskeleton; Cell Proliferation; Cell Adhesion; Protein Binding
PubMed: 38760173
DOI: 10.26508/lsa.202302307 -
Parasite (Paris, France) 2024Eimeria tenella is an obligate intracellular parasite which causes great harm to the poultry breeding industry. Protein phosphorylation plays a vital role in host...
Quantitative phosphoproteomic analysis of chicken DF-1 cells infected with Eimeria tenella, using tandem mass tag (TMT) and parallel reaction monitoring (PRM) mass spectrometry.
Eimeria tenella is an obligate intracellular parasite which causes great harm to the poultry breeding industry. Protein phosphorylation plays a vital role in host cell-E. tenella interactions. However, no comprehensive phosphoproteomic analyses of host cells at various phases of E. tenella infection have been published. In this study, quantitative phosphoproteomic analysis of chicken embryo DF-1 fibroblasts that were uninfected (UI) or infected with E. tenella for 6 h (PI6, the early invasion phase) or 36 h (PI36, the trophozoite development phase) was conducted. A total of 10,122 phosphopeptides matched to 3,398 host cell phosphoproteins were identified and 13,437 phosphorylation sites were identified. Of these, 491, 1,253, and 275 differentially expressed phosphorylated proteins were identified in the PI6/UI, PI36/UI, and PI36/PI6 comparisons, respectively. KEGG pathway enrichment analysis showed that E. tenella modulated host cell processes through phosphorylation, including focal adhesion, regulation of the actin cytoskeleton, and FoxO signaling to support its early invasion phase, and modulating adherens junctions and the ErbB signaling pathway to favor its trophozoite development. These results enrich the data on the interaction between E. tenella and host cells and facilitate a better understanding of the molecular mechanisms underlying host-parasite relationships.
Topics: Animals; Eimeria tenella; Chickens; Proteomics; Phosphoproteins; Tandem Mass Spectrometry; Phosphorylation; Fibroblasts; Cell Line; Poultry Diseases; Host-Parasite Interactions; Coccidiosis; Chick Embryo; Signal Transduction
PubMed: 38759153
DOI: 10.1051/parasite/2024027 -
The Journal of Cell Biology Jun 2024There has long been conflicting evidence as to how bundled actin filaments, found in cellular structures such as filopodia, are disassembled. In this issue, Chikireddy...
There has long been conflicting evidence as to how bundled actin filaments, found in cellular structures such as filopodia, are disassembled. In this issue, Chikireddy et al. (https://doi.org/10.1083/jcb.202312106) provide a detailed in vitro analysis of the steps involved in fragmentation of fascin-bundled actin filaments and propose a novel mechanism for severing two-filament bundles.
Topics: Actin Cytoskeleton; Microfilament Proteins; Actins; Pseudopodia; Humans; Animals; Carrier Proteins
PubMed: 38748453
DOI: 10.1083/jcb.202403191 -
Zoological Research May 2024Proper regulation of synapse formation and elimination is critical for establishing mature neuronal circuits and maintaining brain function. Synaptic abnormalities, such...
Proper regulation of synapse formation and elimination is critical for establishing mature neuronal circuits and maintaining brain function. Synaptic abnormalities, such as defects in the density and morphology of postsynaptic dendritic spines, underlie the pathology of various neuropsychiatric disorders. Protocadherin 17 (PCDH17) is associated with major mood disorders, including bipolar disorder and depression. However, the molecular mechanisms by which PCDH17 regulates spine number, morphology, and behavior remain elusive. In this study, we found that PCDH17 functions at postsynaptic sites, restricting the number and size of dendritic spines in excitatory neurons. Selective overexpression of PCDH17 in the ventral hippocampal CA1 results in spine loss and anxiety- and depression-like behaviors in mice. Mechanistically, PCDH17 interacts with actin-relevant proteins and regulates actin filament (F-actin) organization. Specifically, PCDH17 binds to ROCK2, increasing its expression and subsequently enhancing the activity of downstream targets such as LIMK1 and the phosphorylation of cofilin serine-3 (Ser3). Inhibition of ROCK2 activity with belumosudil (KD025) ameliorates the defective F-actin organization and spine structure induced by PCDH17 overexpression, suggesting that ROCK2 mediates the effects of PCDH17 on F-actin content and spine development. Hence, these findings reveal a novel mechanism by which PCDH17 regulates synapse development and behavior, providing pathological insights into the neurobiological basis of mood disorders.
Topics: Animals; Mice; Actin Cytoskeleton; Cadherins; Dendritic Spines; Gene Expression Regulation; rho-Associated Kinases; Protocadherins
PubMed: 38747058
DOI: 10.24272/j.issn.2095-8137.2024.055