2-Aminothiazole-Flavonoid Hybrid Derivatives Binding to Tau Protein and Responsible for Antitumor Activity in Glioblastoma.

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.

Tau Protein as Therapeutic Target for Cancer? Focus on Glioblastoma.

Despite being extensively studied for several decades, the microtubule-associated protein Tau has not finished revealing its secrets. For long, Tau has been known for its ability to promote microtubule assembly. A less known feature of Tau is its capability to bind to cancer-related protein kinases, suggesting a possible role of Tau in modulating microtubule-independent cellular pathways that are associated with oncogenesis.

Tau regulates the microtubule-dependent migration of glioblastoma cells via the Rho-ROCK signaling pathway.

The pathological significance of Tau (encoded by ) in mechanisms driving cell migration in glioblastoma is unclear. By using an shRNA approach to deplete microtubule-stabilizing Tau in U87 cells, we determined its impact on cytoskeletal coordination during migration. We demonstrated here that the motility of these Tau-knockdown cells (shTau cells) was significantly (36%) lower than that of control cells.

Zinc Induces Temperature-Dependent Reversible Self-Assembly of Tau.

Tau is an intrinsically disordered microtubule-associated protein that is implicated in several neurodegenerative disorders called tauopathies. In these diseases, Tau is found in the form of intracellular inclusions that consist of aggregated paired helical filaments (PHFs) in neurons. Given the importance of this irreversible PHF formation in neurodegenerative disease, Tau aggregation has been extensively studied.

Two Tau binding sites on tubulin revealed by thiol-disulfide exchanges.

Tau is a Microtubule-associated protein that induces and stabilizes the formation of the Microtubule cytoskeleton and plays an important role in neurodegenerative diseases. The Microtubules binding region of Tau has been determined for a long time but where and how Tau binds to its partner still remain a topic of debate. We used Site Directed Spin Labeling combined with EPR spectroscopy to monitor Tau upon binding to either Taxol-stabilized MTs or to αβ-tubulin when Tau is directly used as an inducer of MTs formation.

Synthesis and biological evaluation of 4 arylcoumarin analogues as tubulin-targeting antitumor agents.

The synthesis of twenty-six 4-arylcoumarin analogues of combretastatin A-4 (CA-4) led to the identification of two new compounds (25 and 26) with strong cytotoxic activity. Both compounds had a high cytotoxic effect on a CA-4-resistant colon adenocarcinoma cell line (HT29D4). The compounds affected cell cycle progression characterized by a mitotic block.

Tau Interaction with Tubulin and Microtubules: From Purified Proteins to Cells.

Microtubules (MTs) play an important role in many cellular processes and are dynamic structures regulated by an important network of microtubules-associated proteins, MAPs, such as Tau. Tau has been discovered as an essential factor for MTs formation in vitro, and its region implicated in binding to MTs has been identified. By contrast, the affinity, the stoichiometry, and the topology of Tau-MTs interaction remain controversial.

Interactions of long-chain homologues of colchicine with tubulin.

Several colchicine analogues in which the N-acetyl residue has been replaced by aliphatic, straight-chain acyl moieties, have been synthesized. These compounds show high cytotoxic activity at the nanomolar level against the tumoral cell lines HT-29, MCF-7 and A549. Some of them exhibit activities in the picomolar range against the HT-29 line and are thus two to three orders of magnitude more cytotoxic than colchicine.

Peptide screen identifies a new NADPH oxidase inhibitor: impact on cell migration and invasion.

The NADPH oxidase proteins catalyse the formation of superoxide anion which act as signalling molecules in physiological and pathological processes. Nox1-dependent NADPH oxidase is expressed in heart, lung, colon, blood vessels and brain. Different strategies involving Nox1 inhibition based on diphenylene iodonium derivatives are currently tested for colorectal cancer therapy.

Tau antagonizes end-binding protein tracking at microtubule ends through a phosphorylation-dependent mechanism.

Proper regulation of microtubule dynamics is essential for cell functions and involves various microtubule-associated proteins (MAPs). Among them, end-binding proteins (EBs) accumulate at microtubule plus ends, whereas structural MAPs bind along the microtubule lattice. Recent data indicate that the structural MAP tau modulates EB subcellular localization in neurons.

Direct evidence for the interaction of stathmin along the length and the plus end of microtubules in cells.

Stathmin is a prominent destabilizer of microtubules (MTs). Extensive in vitro studies have strongly suggested that stathmin could act by sequestering tubulin and/or by binding to MT tips. In cells, the molecular mechanisms of stathmin binding to tubulin and/or MTs and its implications for the MT dynamics remain unexplored.

Sequential binding of calcium ions to the B-repeat domain of SdrD from Staphylococcus aureus.

Biofilms of live bacteria forming on medical devices and implants contribute significantly to bacterial blood dissemination and to the spread of nosocomial infections. Cell surface SdrD protein plays a key role in the attachment of Staphylococcus aureus to the extracellular matrix (ECM) and in the formation of biofilm. SdrD binds calcium ions using its B1-B5 region bearing EF-hand Ca-binding sites, leading to conformational changes in the structure of SdrD.

Hsp90 Oligomers Interacting with the Aha1 Cochaperone: An Outlook for the Hsp90 Chaperone Machineries.

The 90-kDa heat shock protein (Hsp90) is a highly flexible dimer able to self-associate in the presence of divalent cations or under heat shock. This study investigated the relationship between Hsp90 oligomers and the Hsp90 cochaperone Aha1 (activator of Hsp90 ATPase). The interactions of Aha1 with Hsp90 dimers and oligomers were evaluated by ultracentrifugation, size-exclusion chromatography coupled to multiangle laser light scattering and high-mass matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Stathmin potentiates vinflunine and inhibits Paclitaxel activity.

Cell biology and crystallographic studies have suggested a functional link between stathmin and microtubule targeting agents (MTAs). In a previous study we showed that stathmin increases vinblastine (VLB) binding to tubulin, and that conversely VLB increases stathmin binding to tubulin. This constituted the first biochemical evidence of the direct relationship between stathmin and an antimitotic drug, and revealed a new mechanism of action for VLB.

Quantitative analysis of tau-microtubule interaction using FRET.

The interaction between the microtubule associated protein, tau and the microtubules is investigated. A fluorescence resonance energy transfer (FRET) assay was used to determine the distance separating tau to the microtubule wall, as well as the binding parameters of the interaction. By using microtubules stabilized with Flutax-2 as donor and tau labeled with rhodamine as acceptor, a donor-to-acceptor distance of 54 ± 1 Å was found.

The indolylcoumarin COUFIN exhibits potent activity against renal carcinoma cells without affecting hematopoietic system.

The present work describes the anticancer activity of a new indolylcoumarin named COUFIN and more specifically, its efficiency against clear cell renal carcinoma (CCRC). COUFIN inhibited microtubule formation and bound on tubulin to or near the colchicine site. In vitro, COUFIN showed potent anticancer activity on renal carcinoma cells (RCC) both in monolayer (2D culture) (IC50 of 88 ± 8 nM) and multicellular tumor spheroid (3D culture) (IC50 of 180 ± 20 nM).

Molecular mechanisms of Tau binding to microtubules and its role in microtubule dynamics in live cells.

Despite extensive studies, the molecular mechanisms of Tau binding to microtubules (MTs) and its consequences on MT stability still remain unclear. It is especially true in cells where the spatiotemporal distribution of Tau-MT interactions is unknown. Using Förster resonance energy transfer (FRET), we showed that the Tau-MT interaction was distributed along MTs in periodic hotspots of high and low FRET intensities.

FRET and FRAP imaging: approaches to characterise tau and stathmin interactions with microtubules in cells.

Microtubules (MTs) are involved in many crucial processes such as cell morphogenesis, mitosis and motility. These dynamic structures resulting from the complex assembly of tubulin are tightly regulated by stabilising MT-associated proteins (MAPs) such as tau and destabilising proteins, notably stathmin. Because of their key role, these MAPs and their interactions have been extensively studied using biochemical and biophysical approaches, particularly in vitro.

Synthesis and biological evaluation of novel anticancer bivalent colchicine-tubulizine hybrids.

A series of novel antimitotic hybrids were synthesized in good yields by linking of azide-containing colchicine congeners with acetylene-substituted tubulizine-type derivatives using copper-mediated 1,3-dipolar cycloaddition. Obtained compounds exhibit good cytotoxicity against HBL100 epithelial cell lines (IC(50)=0.599-2.

New insights into tau-microtubules interaction revealed by isothermal titration calorimetry.

Microtubule dynamic instability is tightly regulated by coordinated action of stabilizing and destabilizing microtubule associated proteins. Among the stabilizing proteins, tau plays a pivotal role in both physiological and pathological processes. Nevertheless, the detailed mechanism of tau-tubulin interaction is still subject to controversy.

Synthesis and biological evaluation of 4-arylcoumarin analogues of combretastatins. Part 2.

A series of A-ring variously methoxylated 4-(3-hydroxy-4-methoxyphenyl)coumarins related to combretastatin A-4 was prepared by cross-coupling reactions. Cytotoxicity studies indicated a potent activity against HBL100 cell line. Substitution patterns on A-ring had only a slight effect on antiproliferative activity.

Stathmin and interfacial microtubule inhibitors recognize a naturally curved conformation of tubulin dimers.

Tubulin is able to switch between a straight microtubule-like structure and a curved structure in complex with the stathmin-like domain of the RB3 protein (T(2)RB3). GTP hydrolysis following microtubule assembly induces protofilament curvature and disassembly. The conformation of the labile tubulin heterodimers is unknown.

Synthesis and complete assignment of the 1H and 13C NMR signals of new acetamido and aminoflavonoid derivatives.

The complete (1)H and (13)C NMR assignment of 9 acetamidochalcones, 18 acetamidoflavones, 18 aminoflavones, 9 acetamidoflavonols and 9 aminoflavonols has been performed using one- and two-dimensional NMR techniques including COSY, HMQC and HMBC experiments.

New insights into the antibacterial mechanism of action of squalamine.

Objectives: Antimicrobial resistance is an increasingly life-threatening problem that emphasizes the need to develop new antibacterial agents. The in vitro antibacterial activity of squalamine, a natural aminosterol, has been previously demonstrated against multidrug-resistant bacteria and moulds. Although the antibacterial activity of squalamine was found to correlate with that of other drugs, such as colistin, against Gram-negative bacteria, the former was active against Gram-positive bacteria, which are resistant to colistin.

Microtubule and MAPs: thermodynamics of complex formation by AUC, ITC, fluorescence, and NMR.

Microtubules are implicated in many essential cellular processes such as architecture, cell division, and intracellular traffic, due to their dynamic instability. This dynamicity is tightly regulated by microtubule-associated proteins (MAPs), such as tau and stathmin. Despite extensive studies motivated by their central role in physiological functions and pathological role in neurodegenerative diseases and cancer, the precise mechanisms of tau and stathmin binding to tubulin and their consequences on microtubule stability are still not fully understood.