Sulfonamide Drugs Binding to the Colchicine Site of Tubulin:  Thermodynamic Analysis of the Drug−Tubulin Interactions by Isothermal Titration Calorimetry

Abstract

The discovery of several sulfonamide drugs paved the way toward the synthesis of 6 (N-[2-[(4-hydroxyphenyl)amino]-3-pyridinyl]-4-methoxybenzenesulfonamide, E7010) and 7 (N-(3-fluoro-4-methoxyphenyl)pentafluorobenzenesulfonamide, T138067), both of which inhibit tubulin polymerization and are under clinical development. A series of diarylsulfonamides containing an indole scaffold was also found to have antimitotic properties, but their mode of interactions with tubulin has remained unidentified so far. In this study, we demonstrate that these sulfonamide drugs bind to the colchicine site of tubulin in a reversible manner. They quenched intrinsic tryptophan fluorescence of tubulin presumably due to drug-induced conformational changes in the protein, but were unable to modulate GTPase activity of tubulin in contrast to colchicine that enhances the same enzymatic activity. Further investigation using isothermal titration calorimetry (ITC) revealed that 5 (N-(5-chloro-7-indolyl)-4-methoxybenzenesulfonamide) afforded a large positive value of heat capacity change (DeltaC(p)() = +264 cal mol(-1) K(-1)) on binding to tubulin, suggesting a substantial conformational transition in the protein along with partial enthalpy-entropy compensation. On the other hand, the 2-chloro regioisomer 2 gave a large negative value of DeltaC(p)() (-589 cal mol(-1) K(-1)) along with complete enthalpy-entropy compensation. This thermodynamic profile was thought to be attributable to a prominent contribution of van der Waals interaction and hydrogen bonding between specific groups in the drug-tubulin complex. These results indicate that a mere alteration in the position of a single substituent chlorine on the indole scaffold has a great influence on the drug-tubulin binding thermodynamics.

Microtubule assembly dynamics: An attractive target for anticancer drugs

“…Griseofulvin does not have a distinct effect on the interphase microtubules. Even at twice IC 50 concentrations of griseofulvin, no detectable change in the interphase microtubules has been observed. However, at higher concentrations (6 3 IC 50 ), griseofulvin significantly depolymerizes interphase microtubules of HeLa cells.…”

“…1). Indole sulfonamides inhibit the binding of colchicine to tubulin; however, unlike colchicine, sulfonamides do not increase the GTPase activity of tubulin indicating that these agents bind to tubulin by different mechanisms (50). Docking studies also indicated that E7010 and the indole sulfonamides derived from E7010, may have distinct binding modes at the colchicine site on tubulin (51).…”

Design, synthesis and biological evaluation of some novel N-arylpyrazole derivatives bearing the sulfonamide moiety as cytotoxic agents

“…Indeed, they have also been reported to possess various types of biological properties such as anticancer [17], antibacterial [18], antimicrobial [19,20], antimalarial [21], antihypertensive [22], antitumor [23], and antiinflammatory activities [24][25][26][27][28][29][30][31], among others. Among these, the anticancer activity was found to take place through a variety of mechanisms such as disruption of the microtubule assembly, cell cycle arrest in the G1 phase, functional suppression of the transcriptional activator NF-Y, angiogenesis and carbonic anhydrase inhibition [15,16].…”

Synthesis and Evaluation of 5-Chloro-2-Methoxy-N-(4-Sulphamoylphenyl) Benzamide Derivatives as Anti-cancer Agents

“…E7010 [8]). There is considerable interest in extending and diversifying the sulphonamide framework to further explore therapeutic potentials [9].…”