Dissecting Paclitaxel–Microtubule Association: Quantitative Assessment of the 2′-OH Group (original) (raw)
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Chemistry & Biology, 2005
The interactions of microtubules with most compounds described as stabilizing agents have been studied. Several of them (lonafarnib, dicumarol, lutein, and jatrophane polyesters) did not show any stabilizing effect on microtubules. Taccalonolides A and E show paclitaxel-like effects in cells, but they were not able to modulate in vitro tubulin assembly or to bind microtubules, which suggests that other factors are involved in their cellular effects. The binding constants of epothilones, eleutherobin, discodermolide, sarcodictyins, 3,17b-diacetoxy-2-ethoxy-6-oxo-B-homo-estra-1,3,5(10)triene, and dictyostatin to the paclitaxel site; the critical concentrations of ligand-induced assembly; and their cytotoxicity in carcinoma cells have been measured, and correlations between these parameters have been determined. The inhibition of cell proliferation correlates better with the binding enthalpy change than with the binding constants, suggesting that large, favorable enthalpic contribution to the binding is desired to design paclitaxel site drugs with higher cytotoxicity.
Biochemistry, 2007
Microtubule binding and tubulin assembly promotion by a series of conformationally restricted paclitaxel (PTX) derivatives was investigated. In these derivatives, the C-4 acetate of the taxane is tethered to the C-3′ phenyl at ortho and meta positions with different length linkers. The apparent affinity of these derivatives for GMPCPP-stabilized microtubules was assessed by a competition assay, and their influence on microtubule polymerization was evaluated by measuring the critical concentration of GDP-tubulin in the presence of the respective molecule. In general, taxane derivatives with higher apparent affinity for microtubules induced tubulin assembly more efficiently. Among the derivatives, molecules with the shortest tether display the strongest affinity for microtubules. These derivatives exhibited enhanced microtubule stabilization properties and efficiently induced GDP-tubulin assembly into microtubules at low temperature of 12°C and in the absence of Mg 2+ ions in 0.1 M PIPES. Based on molecular dynamics simulations, we propose that the enhanced ability to assemble microtubules by these taxane derivatives is linked to their ability to effectively shape the conformation of the M-loop of tubulin for cross-protofilament interaction.
A new tubulin-binding site and pharmacophore for microtubule-destabilizing anticancer drugs
Proceedings of the National Academy of Sciences of the United States of America, 2014
The recent success of antibody-drug conjugates (ADCs) in the treatment of cancer has led to a revived interest in microtubule-destabilizing agents. Here, we determined the high-resolution crystal structure of the complex between tubulin and maytansine, which is part of an ADC that is approved by the US Food and Drug Administration (FDA) for the treatment of advanced breast cancer. We found that the drug binds to a site on β-tubulin that is distinct from the vinca domain and that blocks the formation of longitudinal tubulin interactions in microtubules. We also solved crystal structures of tubulin in complex with both a variant of rhizoxin and the phase 1 drug PM060184. Consistent with biochemical and mutagenesis data, we found that the two compounds bound to the same site as maytansine and that the structures revealed a common pharmacophore for the three ligands. Our results delineate a distinct molecular mechanism of action for the inhibition of microtubule assembly by clinically r...
Journal of Medicinal Chemistry, 2007
The important anticancer drug paclitaxel binds to the -subunit of the R -tubulin dimer in the microtubule in a stoichiometric ratio, promoting microtubule polymerization and stability. The conformation of microtubule-bound drug has been the subject of intense study, and various suggestions have been proposed. In previous work we presented experimental and theoretical evidence that paclitaxel adopts a T-shaped conformation when it is bound to tubulin. In this study we report additional experimental data and calculations that delineate the allowable parameters for effective paclitaxel-tubulin interactions.
Pharmacophore Models of Paclitaxel- and Epothilone-Based Microtubule Stabilizing Agents
Bulletin of the Korean Chemical Society, 2013
Microtubules play an important role in intracellular transport, mobility, and particularly mitosis. Paclitaxel (Taxol TM) and paclitaxel-like compounds have been shown to be anti-tumor agents useful for various human tumors. Paclitaxel-like compounds operate by stabilizing microtubules through interface binding at the interface between two β-tubulin monomers in adjacent protofilaments. In this paper we present the elucidation of the structural features of paclitaxel and paclitaxel-like compounds (e.g., epothilones) with microtubule stabilizing activities, and relate their activities to spatial and chemical features of the molecules. CATALYST program was used to generate three-dimensional quantitative structure activity relationships (3D-QSARs) resulting in 3D pharmacophore models of epothilone-and paclitaxel-derivatives. Pharmacophore models were generated from diverse conformers of these compounds resulting in a high correlation between experimental and predicted biological activities (r = 0.83 and 0.91 for epothilone and paclitaxel derivatives, respectively). On the basis of biological activities of the training sets, five-and four-feature pharmacophore hypotheses were generated in the epothilone and paclitaxel series. The validation of generated hypotheses was achieved by using twelve epothilones and ten paclitaxels, respectively, which are not in the training sets. The clustering (grouping) and merging techniques were used in order to supplement spatial restrictions of each of hypothesis and to develop more comprehensive models. This approach may be of use in developing novel inhibitor candidates as well as contributing a better understanding of structural characters of many compounds useful as anticancer agents targeting microtubules.
ACS Chemical Biology, 2011
The binding interactions of two antitumour agents that target the paclitaxel site, docetaxel and discodermolide, to unassembled -tubulin heterodimers and microtubules have been studied using biochemical and NMR techniques. The use of discodermolide as a water-soluble paclitaxel biomimetic and extensive NMR experiments allowed the detection of binding of microtubule-stabilizing agents to unassembled tubulin -heterodimers. The bioactive 3D structures of docetaxel and discodermolide bound to -heterodimers were elucidated and compared to those bound to microtubules, where subtle changes in the conformations of docetaxel in its different bound states were evident. Moreover, the combination of experimental TR-NOE and STD NMR data with CORCEMA-STD calculations indicate that
Chemistry & Biology, 2004
gicas their good activity against ovarian, metastatic breast, head and neck, and lung cancer [4], paclitaxel has two Consejo Superior de Investigaciones Científicas Ramiro de Maeztu 9 factors that hamper its applicability. First, its low aqueous solubility, and second, the development of pleiotro-28040 Madrid Spain pic drug resistance mediated both by the overexpression of the P-glycoprotein [5, 6] and the presence of mutations in -tubulin [7, 8]. The discovery in recent years of several natural sub-Atlanta, Georgia 30322 3 Department of Chemistry and stances with a paclitaxel-like mechanism of action (epothilone, discodermolide, laulimalide, eleutherobin, The Skaggs Institute for Chemical Biology The Scripps Research Institute peloruside, dictyostatin-1, taccalonolide, and jatrophane polyesters; [9-16]) opened new possibilities in 10550 North Torrey Pines Road La Jolla, California 92037 the field. Of these compounds, the first one recognized as having a paclitaxel-like activity was an already known natural compound called epothilone [9], a secondary metabolite from the soil myxobacterium Sorangium cel-9500 Gilman Drive La Jolla, California 92093 lulosum [17-19]. Epothilones are the most promising of this group of new paclitaxel-like compounds because they offer several advantages. First of all, while most of the other compounds are isolated from marine organ-Summary isms in limited amounts, epothilone B can be obtained in kilogram amounts by fermentation [20]. Second, it The interactions of epothilone analogs with the paclihas higher solubility in water than paclitaxel [19]. Third, taxel binding site of microtubules were studied. The
Biochemistry, 1995
Our finding that an analog of paclitaxel (Taxol) modified at position C-2 (2-debenzoyl-2-(m-azidobenzoy1)paclitaxel) was substantially more active than paclitaxel in promoting tubulin assembly [Chaudhary et al. (1994) J. Am. Chem. SOC. 116, 4097-40981 led us to perform an analysis of the modulating effects of microtubule-associated proteins, GTP, and temperature on assembly and polymer stability. The analog always showed superior activity to paclitaxel in inducing polymerization where it fails to occur without drug, probably indicating a greater ability than paclitaxel to "hypemucleate" assembly. In contrast, much smaller differences in effects on polymer stability were observed. The analysis was extended to a large series of derivatives modified at positions C-2, C-7, C-10, and C-3', including docetaxel, a clinically important analog of paclitaxel. While analog stabilization of polymer was frequently observed, neither qualitative nor quantitative analysis of this property reliably predicted whether a compound would have enhanced hypemucleation activity relative to that of paclitaxel. Stabilization was often observed at substoichiometric analog concentrations, while even superstoichiometric concentrations of most compounds failed to induce extensive tubulin polymerization at low temperatures or in the absence of microtubuleassociated proteins or GTP. Docetaxel was intermediate in activity between paclitaxel and 2-debenzoyl-2-(m-azidobenzoyl)paclitaxel in promoting assembly reactions. We conclude that the hypemucleation of tubulin assembly and polymer stabilization observed with paclitaxel represent two distinct properties of the drug. Our findings suggest that paclitaxel, docetaxel, and 2-debenzoyl-2-(m-azidobenzoyl)paclitaxel are able to interact with progressively smaller assemblages of tubulin at low temperatures or in the absence of microtubule-associated proteins or GTP. Antimitotic agents, by interfering with the microtubule system, inhibit cell growth and have potential roles in the treatment of neoplastic diseases. Most compounds in this class inhibit microtubule formation and may cause disassembly of existing microtubules. Exceptions are the taxoids paclitaxel and docetaxel [Taxol (1) and Taxotere (2); structures in Figure 11, which have great promise in cancer treatment (for reviews, see Kingston, 1991; Rowinsky & Donehower, 1992; Kingston et al., 1993; Nicolaou et al., 1994). Paclitaxel not only enhances microtubule assembly and stabilizes microtubules to disassembly induced by cold, calcium, and dilution (Schiff et al., 1979), but it also obviates many of the normal requirements for tubulin polymerization. Paclitaxel permits assembly reactions to occur at low temperatures and in the absence of microtubule-associated proteins (MAPs)' and GTP (
Structural insight into the stabilization of microtubules by taxanes
2021
Paclitaxel (Taxol®) is a taxane and a first-line chemotherapeutic drug that stabilizes microtubules. While the interaction of paclitaxel with microtubules is well described, the current lack of high-resolution structural information on a tubulin-taxane complex precludes a comprehensive description of the binding determinants that affect the drug’s mechanism of action. Here, we solved the crystal structure of the core baccatin III moiety of paclitaxel lacking the C13 side chain in complex with tubulin at 1.9 Å resolution. Based on this information, we engineered two tailor-made taxanes with modified C13 side chains, solved their crystal structures in complex with tubulin, and analyzed their effects along with those of paclitaxel, docetaxel, and baccatin III on the microtubule lattice by X-ray fiber diffraction. We then compared high-resolution structures of ligand-bound tubulin and microtubule complexes with apo forms and used molecular dynamics simulations to understand the conseque...