Gaining ligand selectivity in thyroid hormone receptors via entropy

Autor(es):Mostrar menos -

Martinez, Leandro ^[1] ; Nascimento, Alessandro S. ^[2] ; Nunes, Fabio M. ^[2] ; Phillips, Kevin ^[3] ; Aparicio, Ricardo ^[2] ; Dias, Sandra Martha G. ^[2] ; Figueira, Ana Carolina M. ^[2] ; Lin, Jean H. ^[3] ; Nguyen, Phuong ^[3] ; Apriletti, James W. ^[3] ; Neves, Francisco A. R. ^[4] ; Baxter, John D. ^[3] ; Webb, Paul ^[3] ; Skaf, Munir S. ^[1] ; Polikarpov, Igor ^[2]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Quim, BR-13084862 Campinas, SP - Brazil

^[2] Univ Sao Paulo, Dept Fis & Informat, Inst Fis Sao Carlos, BR-13566590 Sao Carlos, SP - Brazil

^[3] Methodist Hosp, Res Inst, Houston, TX 77030 - USA

^[4] Univ Brasilia, Fac Ciencias Saude, Lab Farmacol Mol, BR-70910900 Brasilia, DF - Brazil

• Tipo de documento: Artigo Científico
• Fonte: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA; v. 106, n. 49, p. 20717-20722, DEC 8 2009.
• Citações Web of Science: 50

Resumo

Nuclear receptors are important targets for pharmaceuticals, but similarities between family members cause difficulties in obtaining highly selective compounds. Synthetic ligands that are selective for thyroid hormone (TH) receptor beta (TR beta) vs. TR alpha reduce cholesterol and fat without effects on heart rate; thus, it is important to understand TR beta-selective binding. Binding of 3 selective ligands (GC-1, KB141, and GC-24) is characterized at the atomic level; preferential binding depends on a nonconserved residue (Asn-331 beta) in the TR beta ligand-binding cavity (LBC), and GC-24 gains extra selectivity from insertion of a bulky side group into an extension of the LBC that only opens up with this ligand. Here we report that the natural TH 3,5,3'-triodothyroacetic acid (Triac) exhibits a previously unrecognized mechanism of TR beta selectivity. TR x-ray structures reveal better fit of ligand with the TR alpha LBC. The TR beta LBC, however, expands relative to TR alpha in the presence of Triac (549 angstrom(3) vs. 461 angstrom(3)), and molecular dynamics simulations reveal that water occupies the extra space. Increased solvation compensates for weaker interactions of ligand with TR beta and permits greater flexibility of the Triac carboxylate group in TR beta than in TR alpha. We propose that this effect results in lower entropic restraint and decreases free energy of interactions between Triac and TR beta, explaining subtype-selective binding. Similar effects could potentially be exploited in nuclear receptor drug design. (AU)

• Processo FAPESP: 06/00182-8 - Biofísica estrutural dos receptores nucleares e proteínas relacionadas
• Beneficiário: Igor Polikarpov
• Linha de fomento: Auxílio à Pesquisa - Temático