Search Results (278)

The global transition to a circular bioeconomy is accelerating the demand for sustainable, high-performance materials. Filamentous fungi represent a promising solution, as they function as living foundries that transform low-value biomass into advanced, self-assembling materials. While mycelium-based composites have proven potential, progress has been predominantly driven by empirical screening of fungal species and substrates. To unlock their full potential, a paradigm shift from empirical screening to rational design is required. This review introduces a conceptual framework centered on the biochemical programming of the fungal cell wall. Viewed through a materials science lens, the cell wall is a dynamic, hierarchical nanocomposite whose properties can be deliberately tuned. We analyze the contributions of its principal components—the chitin–glucan structural scaffold, the glycoprotein functional matrix, and surface-active hydrophobins—to the bulk characteristics of mycelium-derived materials. We then identify biochemical levers for controlling these properties. External factors such as substrate composition and environmental cues (e.g., pH) modulate cell wall architecture through conserved signaling pathways. Complementing these, an internal synthetic biology toolkit enables direct genetic and chemical intervention. Strategies include targeted engineering of biosynthetic and regulatory genes (e.g., CHS, AGS, GCN5), chemical genetics to dynamically adjust synthesis during growth, and modification of surface chemistry for specialized applications like tissue engineering. By integrating fungal cell wall biochemistry, materials science, and synthetic biology, this framework moves the field from incidental discovery toward the intentional creation of smart, functional, and sustainable mycelium-based materials—aligning material innovation with the imperatives of the circular bioeconomy. Full article

The adult heart has a limited ability to regenerate, which is partly due to the structural and metabolic specialization that cardiomyocytes (CMs) acquire during postnatal maturation. In this review, we explore how cytoskeletal remodeling, metabolic reprogramming, and interactions with the extracellular matrix (ECM) regulate CM maturation, proliferation, and the potential for regeneration. We describe how the assembly of microtubules, actin filaments, and sarcomeric structures is essential for developing contractile function, but also creates structural barriers that prevent cell division. Recent studies show that disassembling these cytoskeletal components, along with activating signaling pathways such as Hippo-YAP, Wnt, and NRG1/ErbB4, can promote CM dedifferentiation and re-entry into the cell cycle. Metabolic shifts also play a critical role. A return from oxidative phosphorylation to glycolysis also leads to CM dedifferentiation and proliferation. In addition, changes in ECM composition and mechanical signaling affect cytoskeletal dynamics and regenerative capacity. Understanding how these structural, metabolic, and signaling networks work together opens the door to new approaches for restoring heart function after injury. Full article

DprA (also known as Smf) is a conserved RecA mediator originally characterized by its role in natural chromosomal transformation, yet its widespread presence across bacteria hints at broader DNA metabolic functions. Here, we demonstrate that Bacillus subtilis DprA enhances the frequency of Escherichia coli Hfr conjugation in vivo. In vitro, RecA·ATP binds and cooperatively polymerizes in a 50-nucleotide (nt) polydeoxy T (dT)₅₀ ssDNA to form dynamic filaments that SSB inhibits, an effect fully reversed by Bacillus subtilis DprA. Escherichia coli RecA bound to (dT)₂₁ exhibits minimal dATPase activity, but the addition of B. subtilis DprA significantly stimulates RecA dATP hydrolysis. B. subtilis RecA·dATP readily assembles on (dT)₂₀ complexes, and DprA allosterically activates RecA on even shorter (dT)₁₅ substrates. Combining biochemical assays with a fully atomic model of the RecA–DprA–ssDNA complex, we proposed that only one DNA binding site of the DprA dimer engages the ssDNA during RecA loading, owing to steric constraints. This work refines the mechanism of DprA-mediated RecA nucleation and defines the minimal ssDNA footprint required for mediator activity. Full article

Focal adhesions (FAs) are multi-protein complexes that mediate cell attachment to the extracellular matrix. Their formation and maturation depend on intracellular tension generated by actin filaments interacting with phosphorylated myosin II. Using live-cell and confocal microscopy, we investigated how FA dynamics are regulated by actin polymerization and myosin II-driven contractility. We found that knockdown of myosin II resulted in complete and irreversible disassembly of FAs. However, partial inhibition of myosin II, through either ROCK or myosin light chain kinase (MLCK) inhibitors, leads to gradual FA shrinkage. In contrast, complete inhibition of myosin II phosphorylation causes disassembly of existing FAs, followed by the formation of new, small FAs at the cell periphery. In both cases, FAs formed after inhibition of myosin II phosphorylation exhibited significantly longer lifespans than FAs in control cells. Similarly, partial inhibition of actin polymerization using nanomolar concentrations of latrunculin B or cytochalasin D also promoted the formation of small FAs. Complete and irreversible FA disassembly occurred only when actin filaments were fully disrupted, leading to cell lamella retraction. These findings suggest that actin polymerization at the cell edge is the minimal and sufficient requirement for the assembly of small FAs. Notably, our data demonstrate for the first time that perturbation of the actin–myosin system results in stabilization and prolonged lifespan of small FAs, whereas larger FAs, formed in the presence of myosin II activity, are more dynamic. Together, these results emphasize the essential role of cortical actin organization and myosin II phosphorylation in the maintenance and turnover of FAs. Full article

This paper catalogues a series of experiments we conducted to explore how to 3D print a DC electric motor. The individual parts of the electric motor were 3D printed but assembled by hand. First, we focused on a rotor with soft magnetic properties, for which we adopted ProtoPasta^TM, which is a commercial off-the-shelf PLA filament incorporating iron particles. Second, we focused on the stator permanent magnets, which were 3D printed through binder jetting. Third, we focused on the wire coils, for which we adopted a form of laminated object manufacture of copper wire. The chief challenge was in 3D printing the coils, because the winding density is crucial to the performance of the motor. We have demonstrated that DC electric motors can be 3D printed and assembled into a functional system. Although the performance was poor due to the wiring problem, we showed that the other 3D printing processes were consistent with high performance. Nevertheless, we demonstrated the principle of 3D printing electric motors. Full article

Fused Filament Fabrication (FFF) enables the manufacturing of complex polymer components. However, surface finish and dimensional accuracy remain key limitations for their integration into functional assemblies. This study explores the potential of conventional turning as a post-processing strategy to improve the geometric and surface quality of PLA reinforced with carbon fiber (CF) parts produced by FFF. Machinability was evaluated through the analysis of cutting forces, thermal behavior, energy consumption, and surface integrity under varying cutting speeds, feed rates, and specimen slenderness. The results indicate that feed is the most influential parameter across all performance metrics, with lower values leading to improved dimensional accuracy and surface finish, achieving the most significant reductions of 63% in surface roughness (Sa) and 62% in cylindricity deviation. Nevertheless, the surface roughness is higher than that of metals, and deviations in geometry along the length of the specimen have been observed. A critical shear stress of 0.237 MPa has been identified as the limit for interlayer failure, defining the boundary conditions for viable cutting operation. The incorporation of CNC turning as a post-processing step reduced the total fabrication time by approximately 83% compared with high-resolution FFF, while maintaining dimensional accuracy and enhancing surface quality. These findings support the use of machining operations as a viable and efficient post-processing method for improving the functionality of polymer-based components produced by additive manufacturing. Full article

The multi-domain muscle protein titin provides elasticity and mechanosensing functions to the sarcomere. Titin’s PEVK domain is intrinsically disordered due to the presence of a large number of prolines and highly charged residues. Although PEVK does not have canonical actin-binding motifs, it has been shown to bind F-actin. Here, we explored whether the PEVK domain may also affect actin assembly. We cloned the middle, 733-residue-long segment (called PEVKII) of the full-length PEVK domain, expressed in E. coli and purified by using His- and Avi-tags engineered to the N- and C-termini, respectively. Actin assembly was monitored by the pyrene assay in the presence of varying PEVKII concentrations. The structural features of PEVKII-associated F-actin were studied with atomic force microscopy. The added PEVKII enhanced the initial and log-phase rates of actin assembly and the peak F-actin quantity in a concentration-dependent way. However, the critical concentration of actin polymerization was unaltered. Thus, PEVK accelerates actin polymerization by facilitating its nucleation. This effect was highlighted in the AFM images of F-actin–PEVKII adsorbed to the supported lipid bilayer. The sample was dominated by radially symmetric complexes of short actin filaments. PEVK’s actin polymerization-modulating effect may, in principle, have a function in regulating sarcomeric actin length and turnover. Altogether, titin’s PEVK domain is not only a non-canonical actin-binding protein that regulates sarcomeric shortening, but one that may modulate actin polymerization as well. Full article

Respiratory syncytial virus (RSV) is a major human respiratory pathogen, particularly affecting infants, the elderly, and immunocompromised individuals. RSV exists in both spherical and filamentous forms, with the filamentous morphology associated with enhanced infectivity and cell-to-cell spread. Here, we demonstrate that RhoA, a small GTPase involved in cytoskeletal regulation, is essential for filamentous RSV morphogenesis through its role in organizing lipid raft microdomains. Rhosin, a selective RhoA inhibitor developed through structure-guided screening, disrupts GEF–RhoA interactions to block RhoA activation. The pharmacological inhibition of RhoA with Rhosin significantly reduced filamentous virion formation, disrupted RSV fusion (F) protein colocalization with lipid rafts, and diminished cell-to-cell fusion, without affecting overall viral replication. Scanning electron microscopy revealed that Rhosin-treated infected HEp-2 cells exhibited fewer and shorter filamentous projections compared to the extensive filament formation seen in untreated cells. β-galactosidase-based fusion assays confirmed that reduced filamentation corresponded with decreased cell-to-cell fusion. The biophysical separation of RSV spherical and filamentous particles by sucrose gradient velocity sedimentation, coupled with fluorescence and transmission electron microscopy, showed that Rhosin treatment shifted virion morphology toward spherical forms. This suggests that RhoA activity is critical for filamentous virion assembly, which may enhance viral spread. Immunofluorescence microscopy using lipid raft-selective dyes (DiIC₁₆) and fusion protein-specific antibodies revealed the strong co-localization of RSV proteins with lipid rafts. Importantly, the pharmacological inhibition of RhoA with Rhosin disrupted F protein partitioning into raft domains, underscoring the requirement for intact lipid rafts in assembly. These findings highlight a novel role for host RhoA signaling in regulating viral assembly through raft microdomain organization, offering a potential target for host-directed antiviral intervention aimed at altering RSV structural phenotypes and limiting pathogenesis. Full article

Glutamate and dopamine receptors play a crucial role in regulating synaptic plasticity throughout the sleep–wake cycle. These receptors form various heterocomplexes in synaptic areas; however, the role of this protein interactome in sleep–wake cycles remains unclear. Co-immunoprecipitation experiments were conducted to observe the complexation of the NMDA glutamate receptor (NMDAR) subunits GluN2A and GluN2B, metabotropic glutamate receptors mGluR1/5, and dopamine receptors (D1R and D2R) with the scaffold protein Homer in the synaptic membranes of the hippocampus after six hours of sleep deprivation (SD) in rats. Our findings indicate that the level of Homer in the GluN2A/mGluR1/D1R interactome decreased during SD, while the content of Homer remained unchanged in the GluN2B/mGluR1/D2R heterocomplex. Moreover, Homer immunoprecipitated a reduced amount of inositol trisphosphate receptor (IP3R) in the microsomal and synaptic fractions, confirming the dissociation of the ternary supercomplex Homer/mGluR1/IP3R during SD. Additionally, our findings indicate that SD increases the synaptic content of the AMPA receptor (AMPAR) subunit GluA1. Unlike AMPAR, NMDAR subunits in synaptic membranes do not undergo significant changes. Furthermore, the G-to-F actin ratio decreases during SD. Changes in the assembly of actin filaments occur due to the dephosphorylation of cofilin. These results suggest that SD causes the dissociation of the GluN2A/mGluR1/D1R/Homer/IP3R heterocomplex in synaptic and endoplasmic membranes. Full article

Artemisia annua L., the primary source of the antimalarial compound artemisinin, is of great importance for malaria treatment. However, its self-incompatibility (SI) restricts selfing breeding and results in unstable artemisinin content which is vulnerable to environmental fluctuations. To address this, our study employed fluorescence microscopy and transcriptomic analysis on stigmas post self- and cross-pollination to explore the molecular mechanisms of SI in Artemisia annua L. Fluorescence microscopy observations indicate that, three hours after pollination, cross-pollinated pollen tubes mostly exhibit normal filamentous growth, whereas the growth of self-pollinated pollen tubes is significantly inhibited, with most appearing as growth-arrested pollen tubes. Using transcriptome analysis, we generated approximately 25.03 GB of data assembled into 69,498 genes and identified 620 differentially expressed genes (DEGs), including 10 classified as SI response genes. Several specific SI-related candidate genes were identified, such as the S-locus receptor kinase (SRK), Calmodulin-like (CML), modifier (MOD), and exocyst complex component (EXO) genes, between AasB and AahA. These DEGs provide vital information for studying A. annua’s SI molecular mechanisms. The putative DEGs between the two groups provided important information for a further study of the molecular mechanisms of SI in A. annua. Candidate SI-associated genes are essential for the genetic engineering of A. annua to overcome SI and to avoid breeding inbred lines. Full article

The purpose of this paper is to analyze the multi-wavelength and multi-instrument observations of two quiescent filament eruptions as well as the deflection of associated CMEs from the radial direction. The events occurred on 18 October 2017 and 9 May 2021, respectively, in the southern solar hemisphere. Both of them and associated flares were registered by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) and the Solar Terrestrial Relations Observatory–Ahead (STEREO A) Observatory in different EUV wavebands. Using data from STEREO A COR1 and COR2 instruments and the Large Angle and Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO), we investigated morphology and kinematics of the eruptions and the latitudinal offset of the related CMEs with respect to the erupting filaments. Our observations provide the evidence that the two filament eruptions were highly non-radial. The observed deviations are attributed to the presence of low-latitude coronal holes. Full article

Axon guidance, a fundamental process in neural circuit formation, is intricately regulated by Fibroblast Growth Factors (FGFs) and their receptors (FGFRs) through dynamic cytoskeletal remodeling. FGF signaling, mediated by heparan sulfate proteoglycans or Klotho co-factors, activates key downstream pathways: PI3K-Akt, JAK-STAT, PLCγ, and RAS-MAPK. These pathways orchestrate actin filament dynamics, microtubule stability, and the organization of intermediate filaments. These pathways converge on Rho GTPases, cofilin, profilin, and tau to balance the cytoskeletal assembly−disassembly cycles, enabling growth cone navigation. Unresolved questions, such as the mechanisms underlying FGF-mediated growth cone steering, highlight critical future research directions. This review integrates structural, molecular, and functional insights into how FGF-FGFR interactions regulate axon pathfinding, emphasizing the crosstalk between signaling cascades and cytoskeletal plasticity. Elucidating these mechanisms not only advances our understanding of neural development but also opens therapeutic avenues for neuro-developmental disorders, nerve injury, and neurodegenerative diseases by targeting FGF-driven cytoskeletal dynamics. Full article

Background: The formin family proteins play an important role in guiding the assembly and nucleation of linear actin and can promote the formation of actin filaments independently of the Arp2/3 complex. As a key protein that regulates the cytoskeleton and cell morphological structure, the formin gene family has been widely studied in plants such as Arabidopsis thaliana and rice. Methods: In this study, we conducted comprehensive analyses, including phylogenetic tree construction, conserved motif identification, co-expression network analysis, and transcriptome data mining. Results: A total of 18 MtFH gene family members were identified, and the distribution of these genes on chromosomes was not uniform. The phylogenetic tree divided the FH proteins of the four species into two major subgroups (Clade I and Clade II). Notably, Medicago truncatula and soybean exhibited closer phylogenetic relationships. The analysis of cis-acting elements revealed the potential regulatory role of the MtFH gene in light response, hormone response, and stress response. GO enrichment analysis again demonstrated the importance of FH for reactions such as actin nucleation. Expression profiling revealed that MtFH genes displayed significant transcriptional responsiveness to cold, drought, and salt stress conditions. And there was a temporal complementary relationship between the expression of some genes under stress. The protein interaction network indicated an interaction relationship between MtFH protein and profilin, etc. In addition, 22 miRNAs were screened as potential regulators of the MtFH gene at the post-transcriptional level. Conclusions: In general, this study provides a basis for deepening the understanding of the physiological function of the MtFH gene and provides a reference gene for stress resistance breeding in agricultural production. Full article

Structural analyses of protein filaments formed by self-assembly, such as actin, tubulin, or recombinase filaments, have suffered for decades from technical issues due to difficulties in crystallization, their large size, or the dynamic behavior inherent to their cellular function. The advent of cryo-electron microscopy has finally enabled us to obtain structures at different stages of the existence of these filaments. However, these structures correspond to frozen states, and the possibility of observations in solution is still lacking, especially for filaments characterized by a high plasticity, such as the RecA protein for homologous recombination. Here, we use a combination of SAXS measurements and integrative modeling to generate the solution structure of two known forms of the RecA nucleoprotein filament, previously characterized by electron microscopy and resolved by X-ray crystallography. The two forms differ in the cofactor bound to RecA–RecA interfaces, either ATP or ADP. Cooperative transition from one form to the other has been observed during single-molecule experiments by pulling on the filament but also in solution by modifying solvent conditions. We first compare the SAXS data against known structural information. While the crystal structure of the ATP form matches well with the SAXS data, we deduce from the SAXS profiles of the ADP-form values of the pitch (72.0 Å) and the number of monomers per turn (6.4) that differ with respect to the crystal structure (respectively, 82.7 Å and 6.0). We then monitor the transition between the two states driven by the addition of magnesium, and we show this transition occurs with 0.3 mM Mg ²⁺ ions with a high cooperativity. Full article

Glial fibrillary acidic protein (GFAP) is classified as a type III intermediate filament protein predominantly expressed in mature astrocytes. It has the ability to self-assemble into 10 nm filaments in vitro, making it particularly valuable for elucidating the sequences essential for filament assembly. In this study, we created a series of deletion mutants targeting sequences in the N-terminal, C-terminal, and central rod domains to explore the sequences critical for the assembly of GFAP into 10 nm filaments. The impact of these deletions on filament formation was evaluated through in vitro assembly studies and transduction assays conducted with primary astrocytes. Our data revealed that deletions at the carboxy end resulted in abnormalities in either filament diameter calibration or lateral association, whereas deletions at the amino-terminal end significantly disrupted the filament assembly process, particularly restricting filament elongation. Furthermore, we discovered that the filament-forming sequences within the rod domain varied in their contributions to filament assembly and network formation. These findings enhance our understanding of the GFAP assembly process in vitro and provide a detailed mapping of the essential regions required for GFAP assembly. These insights hold significant implications for Alexander disease arising from deletion mutations in GFAP. Full article