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Toxicology and Applied Pharmacology Feb 2024Actin filaments form unique structures with robust actin bundles and cytoskeletal networks affixed to the extracellular matrix and interact with neighboring cells, which...
Actin filaments form unique structures with robust actin bundles and cytoskeletal networks affixed to the extracellular matrix and interact with neighboring cells, which are crucial structures for cancer cells to acquire a motile phenotype. This study aims to investigate a novel antitumor mechanism by which Tanshinone IIA (Tan IIA) modulates the morphology and migration of liver cancer cells via actin cytoskeleton regulation. 97H and Huh7 exhibited numerous tentacle-like protrusions that interacted with neighboring cells. Following treatment with Tan IIA, 97H and Huh7 showed a complete absence of cytoplasmic protrusion and adherens junctions, thereby effectively impeding their migration capability. The fluorescence staining of F-actin and microtubules indicated that these tentacle-like protrusions and cell-cell networks were actin-based structures that led to morphological changes after Tan IIA treatment by retracting and reorganizing beneath the membrane. Tan IIA can reverse the actin depolymerization and cell morphology alterations induced by latrunculin A. Tan IIA down-regulated actin and Rho GTPases expression significantly, as opposed to inducing Rho signaling activation. Preventing the activity of proteasomes and lysosomes had no discernible impact on the modifications in cellular structure and protein expression induced by Tan IIA. However, as demonstrated by the puromycin labeling technique, the newly synthesized proteins were significantly inhibited by Tan IIA. In conclusion, Tan IIA can induce dramatic actin cytoskeleton remodeling by inhibiting the protein synthesis of actin and Rho GTPases, resulting in the suppression of tumor growth and migration. Targeting the actin cytoskeleton of Tan IIA is a promising strategy for HCC treatment.
Topics: Humans; Actins; rho GTP-Binding Proteins; Cell Proliferation; Carcinoma, Hepatocellular; Liver Neoplasms; Cytoskeleton; Actin Cytoskeleton; Cell Line, Tumor; Apoptosis; Abietanes
PubMed: 38290667
DOI: 10.1016/j.taap.2024.116839 -
International Journal of Molecular... Oct 2023Tau protein has been described for several decades as a promoter of tubulin assembly into microtubules. Dysregulation or alterations in Tau expression have been related...
Tau protein has been described for several decades as a promoter of tubulin assembly into microtubules. Dysregulation or alterations in Tau expression have been related to various brain cancers, including the highly aggressive and lethal brain tumor glioblastoma multiform (GBM). In this respect, Tau holds significant promise as a target for the development of novel therapies. Here, we examined the structure-activity relationship of a new series of seventeen 2-aminothiazole-fused to flavonoid hybrid compounds (TZF) on Tau binding, Tau fibrillation, and cellular effects on Tau-expressing cancer cells. By spectrofluorometric approach, we found that two compounds, and , demonstrated high affinity for Tau and exhibited a strong propensity to inhibit Tau fibrillation. Then, the biological activity of these compounds was evaluated on several Tau-expressing cells derived from glioblastoma. The two lead compounds displayed a high anti-metabolic activity on cells related to an increased fission of the mitochondria network. Moreover, we showed that both compounds induced microtubule bundling within newly formed neurite-like protrusions, as well as with defection of cell migration. Taken together, our results provide a strong experimental basis to develop new potent molecules targeting Tau-expressing cancer cells, such as GBM.
Topics: Humans; tau Proteins; Glioblastoma; Microtubules; Thiazoles; Tubulin; Protein Binding
PubMed: 37894731
DOI: 10.3390/ijms242015050 -
Science Advances May 2024In recent years, there has been a growing interest in engineering dynamic and autonomous systems with robotic functionalities using biomolecules. Specifically, the...
In recent years, there has been a growing interest in engineering dynamic and autonomous systems with robotic functionalities using biomolecules. Specifically, the ability of molecular motors to convert chemical energy to mechanical forces and the programmability of DNA are regarded as promising components for these systems. However, current systems rely on the manual addition of external stimuli, limiting the potential for autonomous molecular systems. Here, we show that DNA-based cascade reactions can act as a molecular controller that drives the autonomous assembly and disassembly of DNA-functionalized microtubules propelled by kinesins. The DNA controller is designed to produce two different DNA strands that program the interaction between the microtubules. The gliding microtubules integrated with the controller autonomously assemble to bundle-like structures and disassemble into discrete filaments without external stimuli, which is observable by fluorescence microscopy. We believe this approach to be a starting point toward more autonomous behavior of motor protein-based multicomponent systems with robotic functionalities.
Topics: Robotics; DNA; Microtubules; Kinesins; Molecular Motor Proteins
PubMed: 38820146
DOI: 10.1126/sciadv.adn4490 -
PLoS Pathogens Feb 2024The early branching eukaryote Trypanosoma brucei divides uni-directionally along the longitudinal cell axis from the cell anterior toward the cell posterior, and the...
The early branching eukaryote Trypanosoma brucei divides uni-directionally along the longitudinal cell axis from the cell anterior toward the cell posterior, and the cleavage furrow ingresses along the cell division plane between the new and the old flagella of a dividing bi-flagellated cell. Regulation of cytokinesis in T. brucei involves actomyosin-independent machineries and trypanosome-specific signaling pathways, but the molecular mechanisms underlying cell division plane positioning remain poorly understood. Here we report a kinesin-13 family protein, KIN13-5, that functions downstream of FPRC in the cytokinesis regulatory pathway and determines cell division plane placement. KIN13-5 localizes to multiple cytoskeletal structures, interacts with FPRC, and depends on FPRC for localization to the site of cytokinesis initiation. Knockdown of KIN13-5 causes loss of microtubule bundling at both ends of the cell division plane, leading to mis-placement of the cleavage furrow and unequal cytokinesis, and at the posterior cell tip, causing the formation of a blunt posterior. In vitro biochemical assays demonstrate that KIN13-5 bundles microtubules, providing mechanistic insights into the role of KIN13-5 in cytokinesis and posterior morphogenesis. Altogether, KIN13-5 promotes microtubule bundle formation to ensure cleavage furrow placement and to maintain posterior cytoskeleton morphology in T. brucei.
Topics: Cytokinesis; Trypanosoma brucei brucei; Kinesins; Cytoskeleton; Microtubules; Morphogenesis; Protozoan Proteins
PubMed: 38300973
DOI: 10.1371/journal.ppat.1012000 -
Molecular Biology of the Cell Jun 2024The KMN (Knl1/Mis12/Ndc80) network at the kinetochore, primarily known for its role in chromosome segregation, has been shown to be repurposed during neurodevelopment....
The KMN (Knl1/Mis12/Ndc80) network at the kinetochore, primarily known for its role in chromosome segregation, has been shown to be repurposed during neurodevelopment. Here, we investigate the underlying neuronal mechanism and show that the KMN network promotes the proper axonal organization within the head nervous system. Postmitotic degradation of KNL-1, which acts as a scaffold for signaling and has microtubule-binding activities at the kinetochore, led to disorganized ganglia and aberrant placement and organization of axons in the nerve ring - an interconnected axonal network. Through gene-replacement approaches, we demonstrate that the signaling motifs within KNL-1, responsible for recruiting protein phosphatase 1, and activating the spindle assembly checkpoint are required for neurodevelopment. Interestingly, while the microtubule-binding activity is crucial to KMN's neuronal function, microtubule dynamics and organization were unaffected in the absence of KNL-1. Instead, the NDC-80 microtubule-binding mutant displayed notable defects in axon bundling during nerve ring formation, indicating its role in facilitating axon-axon contacts. Overall, these findings provide evidence for a noncanonical role for the KMN network in shaping the structure and connectivity of the nervous system in during brain development.
Topics: Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Axons; Kinetochores; Neurons; Microtubule-Associated Proteins; Microtubules; Nervous System; Spindle Apparatus; Cytoskeletal Proteins; Chromosome Segregation; Signal Transduction
PubMed: 38656792
DOI: 10.1091/mbc.E23-08-0325 -
BioRxiv : the Preprint Server For... Sep 2023Cells have complex and beautiful structures that are important for their function, but understanding the molecular mechanisms that produce these structures is a...
Cells have complex and beautiful structures that are important for their function, but understanding the molecular mechanisms that produce these structures is a challenging problem due to the gap in size scales between molecular interactions and cellular structures. The giant ciliate is a unicellular model organism whose large size, reproducible structure, and ability to heal wounds and regenerate has historically allowed the formation of structure in a single cell to be addressed using methods of experimental embryology. Such studies have shown that specific cellular structures, such as the oral apparatus, always form in specific regions of the cell, which raises the question: what is the source of positional information within this organism? By analogy with embryonic development, in which localized mRNA is often used to mark position, we asked whether position along the anterior-posterior axis of Stentor might be marked by specific regionalized mRNAs. By physically bisecting cells and conducting half-cell RNA sequencing, we were able to identify sets of messages enriched in either the anterior or posterior half. We repeated this analysis in cells in which a set of longitudinal microtubule bundles running down the whole length of the cell, known as KM-fibers, were disrupted by RNAi of b-tubulin. We found that many messages either lost their regionalized distribution or switched to an opposite distribution, such that anterior-enriched messages in control became posterior-enriched in the RNAi cells, or vice versa. This study indicates that mRNA can be regionalized within a single giant cell and that microtubules may play a role, possibly by serving as tracks for the movement of the messages.
PubMed: 36711710
DOI: 10.1101/2023.01.09.523364 -
Nature Communications Mar 2024The axon-initial-segment (AIS) of mature neurons contains microtubule (MT) fascicles (linear bundles) implicated as retrograde diffusion barriers in the retention of...
The axon-initial-segment (AIS) of mature neurons contains microtubule (MT) fascicles (linear bundles) implicated as retrograde diffusion barriers in the retention of MT-associated protein (MAP) tau inside axons. Tau dysfunction and leakage outside of the axon is associated with neurodegeneration. We report on the structure of steady-state MT bundles in varying concentrations of Mg or Ca divalent cations in mixtures containing αβ-tubulin, full-length tau, and GTP at 37 °C in a physiological buffer. A concentration-time kinetic phase diagram generated by synchrotron SAXS reveals a wide-spacing MT bundle phase (B), a transient intermediate MT bundle phase (B), and a tubulin ring phase. SAXS with TEM of plastic-embedded samples provides evidence of a viscoelastic intervening network (IN) of complexes of tubulin oligomers and tau stabilizing MT bundles. In this model, αβ-tubulin oligomers in the IN are crosslinked by tau's MT binding repeats, which also link αβ-tubulin oligomers to αβ-tubulin within the MT lattice. The model challenges whether the cross-bridging of MTs is attributed entirely to MAPs. Tubulin-tau complexes in the IN or bound to isolated MTs are potential sites for enzymatic modification of tau, promoting nucleation and growth of tau fibrils in tauopathies.
Topics: Microtubules; Scattering, Small Angle; tau Proteins; Tubulin; X-Ray Diffraction; Humans
PubMed: 38491006
DOI: 10.1038/s41467-024-46438-x -
NPJ Parkinson's Disease Jan 2024Highly specialized microtubules in neurons are crucial to both health and disease of the nervous system, and their properties are strictly regulated by different...
Highly specialized microtubules in neurons are crucial to both health and disease of the nervous system, and their properties are strictly regulated by different post-translational modifications, including α-Tubulin acetylation. An imbalance in the levels of acetylated α-Tubulin has been reported in experimental models of Parkinson's disease (PD) whereas pharmacological or genetic modulation that leads to increased acetylated α-Tubulin successfully rescues axonal transport defects and inhibits α-Synuclein aggregation. However, the role of acetylation of α-Tubulin in the human nervous system is largely unknown as most studies are based on in vitro evidence. To capture the complexity of the pathological processes in vivo, we analysed post-mortem human brain of PD patients and control subjects. In the brain of PD patients at Braak stage 6, we found a redistribution of acetylated α-Tubulin, which accumulates in the neuronal cell bodies in subcortical structures but not in the cerebral cortex, and decreases in the axonal compartment, both in putamen bundles of fibres and in sudomotor fibres. High-resolution and 3D reconstruction analysis linked acetylated α-Tubulin redistribution to α-Synuclein oligomerization and to phosphorylated Ser 129 α-Synuclein, leading us to propose a model for Lewy body (LB) formation. Finally, in post-mortem human brain, we observed threadlike structures, resembling tunnelling nanotubes that contain α-Synuclein oligomers and are associated with acetylated α-Tubulin enriched neurons. In conclusion, we support the role of acetylated α-Tubulin in PD pathogenesis and LB formation.
PubMed: 38167511
DOI: 10.1038/s41531-023-00607-9 -
Current Biology : CB Jan 2024Actin-microtubule crosstalk diversifies cytoskeletal networks. A new study provides insight into how the microtubule polymerase CKAP5 mediates actin-microtubule...
Actin-microtubule crosstalk diversifies cytoskeletal networks. A new study provides insight into how the microtubule polymerase CKAP5 mediates actin-microtubule crosstalk. CKAP5 directs the assembly of stable actin bundles on dynamic microtubules; in turn, the actin bundles align growing microtubules along their length.
Topics: Actins; Cytoskeleton; Microtubules; Fungi; Nucleotidyltransferases
PubMed: 38262365
DOI: 10.1016/j.cub.2023.12.028 -
American Journal of Transplantation :... May 2024Immunotactoid deposition is a rare fibrillary deposition disease that is primarily seen in the kidney and is associated with paraproteinemia. Here, we report a case of...
Immunotactoid deposition is a rare fibrillary deposition disease that is primarily seen in the kidney and is associated with paraproteinemia. Here, we report a case of hepatic immunotactoid deposition in a 67-year-old male with a history of smoldering myeloma and chronic kidney disease who underwent liver transplantation for metabolic dysfunction-related cirrhosis. Immunotactoid deposition was first identified in the explanted liver and recurred in the allograft within only 7 weeks following transplantation, presenting as ascites with normal liver function tests. The patient's posttransplant course was complicated by proteinuria and renal failure requiring dialysis. Histologic examination of both native and allograft livers demonstrated pink amorphous material occupying sinusoidal spaces that were Congo-red negative and immunoglobulin M Kappa-restricted. Electron microscopy revealed characteristic deposits of electron-dense bundles of hollow microtubules with a 40 nm diameter within the sinusoids and space of Disse, consistent with immunotactoids. Therapy of the patient's underlying plasma-cell dyscrasia utilizing a daratumumab-based regimen showed decreased serum paraproteins, resolution of ascites, and improved kidney function, no longer requiring dialysis, without inducing rejection. The patient continues to respond to treatment 10 months posttransplant.
Topics: Humans; Male; Aged; Liver Transplantation; Recurrence; Prognosis; Liver Diseases; Postoperative Complications
PubMed: 38145784
DOI: 10.1016/j.ajt.2023.12.019