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oai:repisalud.isciii.es:20.500.12105/75162024-09-27T10:06:00Zcom_20.500.12105_19604com_20.500.12105_2051col_20.500.12105_19607

00925njm 22002777a 4500 dc Balaguer, Francisco de Asís author Mühlethaler, Tobias author Estévez-Gallego, Juan author Calvo, Enrique author Giménez-Abián, Juan Francisco author Risinger, April L author Sorensen, Erik J author Vanderwal, Christopher D author Altmann, Karl-Heinz author Mooberry, Susan L author Steinmetz, Michel O author Oliva, María Ángela author Prota, Andrea E author Díaz, J Fernando author 2019-03-20 It has been proposed that one of the mechanisms of taxane-site ligand-mediated tubulin activation is modulation of the structure of a switch element (the M-loop) from a disordered form in dimeric tubulin to a folded helical structure in microtubules. Here, we used covalent taxane-site ligands, including cyclostreptin, to gain further insight into this mechanism. The crystal structure of cyclostreptin-bound tubulin reveals covalent binding to βHis229, but no stabilization of the M-loop. The capacity of cyclostreptin to induce microtubule assembly compared to other covalent taxane-site agents demonstrates that the induction of tubulin assembly is not strictly dependent on M-loop stabilization. We further demonstrate that most covalent taxane-site ligands are able to partially overcome drug resistance mediated by βIII-tubulin (βIII) overexpression in HeLa cells, and compare their activities to pironetin, an interfacial covalent inhibitor of tubulin assembly that displays invariant growth inhibition in these cells. Our findings suggest a relationship between a diminished interaction of taxane-site ligands with βIII-tubulin and βIII tubulin-mediated drug resistance. This supports the idea that overexpression of βIII increases microtubule dynamicity by counteracting the enhanced microtubule stability promoted by covalent taxane-site binding ligands. Int J Mol Sci. 2019; 20(6):E1392 10.3390/ijms20061392 1422-0067 1422-0067 International journal of molecular sciences 30897704 http://hdl.handle.net/20.500.12105/7516 Cyclostreptin Microtubules Multidrug resistance Taxanes Tubulin Crystal Structure of the Cyclostreptin-Tubulin Adduct: Implications for Tubulin Activation by Taxane-Site Ligands