RESUMEN
1. UK-78,282, a novel piperidine blocker of the T lymphocyte voltage-gated K+ channel, Kv1.3, was discovered by screening a large compound file using a high-throughput 86Rb efflux assay. This compound blocks Kv1.3 with a IC50 of approximately 200 nM and 1:1 stoichiometry. A closely related compound, CP-190,325, containing a benzyl moiety in place of the benzhydryl in UK-78,282, is significantly less potent. 2 Three lines of evidence indicate that UK-78,282 inhibits Kv1.3 in a use-dependent manner by preferentially blocking and binding to the C-type inactivated state of the channel. Increasing the fraction of inactivated channels by holding the membrane potential at - 50 mV enhances the channel's sensitivity to UK-78,282. Decreasing the number of inactivated channels by exposure to approximately 160 mM external K+ decreases the sensitivity to UK-78,282. Mutations that alter the rate of C-type inactivation also change the channel's sensitivity to UK-78,282 and there is a direct correlation between tau(h) and IC50 values. 3. Competition experiments suggest that UK-78,282 binds to residues at the inner surface of the channel overlapping the site of action of verapamil. Internal tetraethylammonium and external charybdotoxin do not compete UK-78,282's action on the channel. 4. UK-78,282 displays marked selectivity for Kv1.3 over several other closely related K+ channels, the only exception being the rapidly inactivating voltage-gated K+ channel, Kv1.4. 5. UK-78,282 effectively suppresses human T-lymphocyte activation.
Asunto(s)
Compuestos de Bencidrilo/farmacología , Inmunosupresores/farmacología , Activación de Linfocitos/efectos de los fármacos , Piperidinas/farmacología , Bloqueadores de los Canales de Potasio , Linfocitos T/efectos de los fármacos , Animales , Unión Competitiva , Células COS , Bovinos , Caribdotoxina/metabolismo , Caribdotoxina/farmacología , Células HeLa , Humanos , Radioisótopos de Yodo , Activación del Canal Iónico/fisiología , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Canales de Potasio/metabolismo , Canales de Potasio/fisiología , Ratas , Ratas Endogámicas Lew , Radioisótopos de Rubidio , Linfocitos T/inmunología , Tetraetilamonio/metabolismo , Tetraetilamonio/farmacologíaRESUMEN
Through the use of empirical and computational methods, phosphinate-based inhibitors of MMP-1 and MMP-13 that bind into the S2 pocket of these enzymes were designed. The synthesis and testing of 2 suggested that binding was occurring as hypothesized. Structure determination of a co-crystal of 2 bound to the catalytic domain of MMP-1 confirmed the binding mode. Substituents binding into S2, S1', S2' and S3', were optimized yielding compounds with low double-digit nM IC50's against these enzymes.
Asunto(s)
Inhibidores de la Metaloproteinasa de la Matriz , Ácidos Fosfínicos/farmacología , Sitios de Unión , Colagenasas/farmacocinética , Simulación por Computador , Cristalografía por Rayos X , Diseño de Fármacos , Concentración 50 Inhibidora , Metaloproteinasa 1 de la Matriz , Metaloproteinasa 13 de la Matriz , Modelos MolecularesRESUMEN
A highly conserved motif, GYGD, contributes to the formation of the ion selectivity filter in voltage-gated K+ channels and is thought to interact with the scorpion toxin residue, Lys27. By probing the pore of the Kv1.3 channel with synthetic kaliotoxin-Lys27 mutants, each containing a non-natural lysine analog of a different length, and using mutant cycle analysis, we determined the spatial locations of Tyr400 and Asp402 in the GYGD motif, relative to His404 located at the base of the outer vestibule. Our data indicate that the terminal amines of the shorter Lys27 analogs lie close to His404 and to Asp402, while Lys27 itself interacts with Tyr400. Based on these data, we developed a molecular model of this region of the channel. The junction between the outer vestibule and the pore is defined by a ring ( approximately 8-9-A diameter) formed from alternating Asp402 and His404 residues. Tyr400 lies 4-6 A deeper into the pore, and its interaction with kaliotoxin-Lys27 is in competition with K+ ions. Studies with dimeric Kv1.3 constructs suggest that two Tyr400 residues in the tetramer are sufficient to bind K+ ions. Thus, at least part of the K+ channel signature sequence extends into a shallow trough at the center of a wide external vestibule.
Asunto(s)
Canales de Potasio con Entrada de Voltaje , Canales de Potasio/metabolismo , Venenos de Escorpión/química , Animales , Ácido Aspártico , Sitios de Unión , Cinética , Canal de Potasio Kv1.3 , Lisina , Modelos Moleculares , Mutagénesis Sitio-Dirigida , Venenos de Escorpión/farmacología , Relación Estructura-Actividad , Termodinámica , Tirosina , XenopusRESUMEN
The architecture of the pore-region of a voltage-gated K+ channel, Kv1.3, was probed using four high affinity scorpion toxins as molecular calipers. We established the structural relatedness of these toxins by solving the structures of kaliotoxin and margatoxin and comparing them with the published structure of charybdotoxin; a homology model of noxiustoxin was then developed. Complementary mutagenesis of Kv1.3 and these toxins, combined with electrostatic compliance and thermodynamic mutant cycle analyses, allowed us to identify multiple toxin-channel interactions. Our analyses reveal the existence of a shallow vestibule at the external entrance to the pore. This vestibule is approximately 28-32 A wide at its outer margin, approximately 28-34 A wide at its base, and approximately 4-8 A deep. The pore is 9-14 A wide at its external entrance and tapers to a width of 4-5 A at a depth of approximately 5-7 A from the vestibule. This structural information should directly aid in developing topological models of the pores of related ion channels and facilitate therapeutic drug design.
Asunto(s)
Espectroscopía de Resonancia Magnética , Canales de Potasio/química , Venenos de Escorpión/química , Secuencia de Aminoácidos , Sitios de Unión , Caribdotoxina/química , Conductividad Eléctrica , Electroquímica , Activación del Canal Iónico , Modelos Moleculares , Datos de Secuencia Molecular , Mutagénesis , Neurotoxinas/química , Canales de Potasio/fisiología , Estructura Terciaria de Proteína , Soluciones , TermodinámicaRESUMEN
A new series of thiazolidine-2,4-diones was obtained by replacing the ether function of englitazone with various functional groups, i.e., a ketone, alcohol, or olefin moiety. These compounds lower blood glucose levels in the genetically obese and insulin-resistant ob/ob mouse. Appending an oxazole-based group at the terminus of the chain provided highly potent compounds.
Asunto(s)
Hipoglucemiantes/farmacología , Tiazoles/farmacología , Tiazolidinedionas , Alcoholes/química , Animales , Benzopiranos/química , Glucemia/análisis , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Hipoglucemiantes/síntesis química , Hipoglucemiantes/uso terapéutico , Cetonas/química , Ratones , Ratones Endogámicos C57BL , Tiazoles/síntesis química , Tiazoles/química , Tiazoles/uso terapéuticoRESUMEN
With computer modeling, an initial three-component pharmacophore for specific 5-HT3 receptor ligands ICS-205-930 (1), ondansetron (2), zacopride (3), and 3-[2-(guanidinylmethyl)-4-thiazolyl]indol (4) has been identified. Two parts represent electrostatic interactions, one as a hydrogen-bond-donating interaction and the other as a hydrogen-bond-accepting interaction. The third part is represented by a plane in which the lipophilic aromatic groups align. The generation of the pharmacophore relies on the interactions of these ligands with probe atoms representative of a possible hydrogen-bond donor or hydrogen-bond acceptor within the receptor. A carboxylate oxygen was used as a hydrogen-bond-accepting probe and a serine-like hydroxyl was utilized as a hydrogen-bond-donating probe.
Asunto(s)
Compuestos Bicíclicos Heterocíclicos con Puentes , Receptores de Serotonina/efectos de los fármacos , Antagonistas de la Serotonina , Animales , Benzamidas/química , Compuestos Bicíclicos con Puentes/química , Gráficos por Computador , Simulación por Computador , Imidazoles/química , Técnicas In Vitro , Indoles/química , Ligandos , Ratones , Modelos Moleculares , Ondansetrón , Ratas , Relación Estructura-Actividad , Tiazoles , TropisetrónRESUMEN
A novel structural class of highly potent and selective 5-HT3 receptor antagonists is described. The compounds in this new series contain a thiazole moiety linking an aromatic group and a nitrogen-containing basic region; the thiazole group appears to be acting as a carbonyl bioisostere in this system. An optimized member of this series, 4-(2-methoxyphenyl)-2-[[4(5)-methyl-5(4)-imidazolyl]methyl]thiazole (5), exhibits oral activity in the Bezold-Jarisch reflex paradigm comparable to or better than the standard agents ondansetron (1) and ICS-205-930 (2). Several of the structure-activity relationships are rationalized in terms of a computer pharmacophore model for 5-HT3 receptor binding.
Asunto(s)
Receptores de Serotonina/efectos de los fármacos , Antagonistas de la Serotonina/síntesis química , Tiazoles/farmacología , Administración Oral , Animales , Gráficos por Computador , Técnicas In Vitro , Ratones , Modelos Moleculares , Neuronas/metabolismo , Ensayo de Unión Radioligante , Ratas , Receptores de Serotonina/clasificación , Antagonistas de la Serotonina/metabolismo , Antagonistas de la Serotonina/farmacología , Relación Estructura-Actividad , Tiazoles/administración & dosificación , Tiazoles/química , Células Tumorales CultivadasRESUMEN
Sorbinil (1), a spirocyclic hydantoin, is a potent inhibitor of the enzyme aldose reductase. Simulation of the rigid spirocyclic ring orientation found in sorbinil was achieved with nonspirocyclic 5-[5'-chloro-2'-(alkylsulfonyl)-phenyl]hydantoins and 5-[5'-chloro-2'-[(N-alkylamino)sulfonyl]phenyl]hydantoins. The 2'-substituent (SO2R) was sufficiently large to hinder rotation of the hydantoin ring, forcing an orientation similar to that of a spirocyclic hydantoin. Calculated conformational preference, X-ray data, and inhibitory IC50 values for these nonspirocyclic 2'-substituted (SO2R) phenylhydantoins are in accord with what is expected for spirocyclic hydantoins and comparable to those of sorbinil.