RESUMO
Startling reports described the paradoxical triggering of the human mitogen-activated protein kinase pathway when a small-molecule inhibitor specifically inactivates the BRAF V600E protein kinase but not wt-BRAF. We performed a conceptual analysis of the general phenomenon "activation by inhibition" using bacterial and human HtrA proteases as models. Our data suggest a clear explanation that is based on the classic biochemical principles of allostery and cooperativity. Although substoichiometric occupancy of inhibitor binding sites results in partial inhibition, this effect is overrun by a concomitant activation of unliganded binding sites. Therefore, when an inhibitor of a cooperative enzyme does not reach saturating levels, a common scenario during drug administration, it may cause the contrary of the desired effect. The implications for drug development are discussed.
Assuntos
Sítio Alostérico , Antineoplásicos/farmacologia , Proteínas de Choque Térmico/antagonistas & inibidores , Serina Peptidase 1 de Requerimento de Alta Temperatura A/antagonistas & inibidores , Proteínas Periplásmicas/antagonistas & inibidores , Inibidores de Proteases/farmacologia , Regulação Alostérica , Antineoplásicos/química , Escherichia coli , Proteínas de Choque Térmico/química , Proteínas de Choque Térmico/metabolismo , Serina Peptidase 1 de Requerimento de Alta Temperatura A/química , Serina Peptidase 1 de Requerimento de Alta Temperatura A/metabolismo , Humanos , Proteínas Periplásmicas/química , Proteínas Periplásmicas/metabolismo , Inibidores de Proteases/química , Ligação Proteica , Serina Endopeptidases/química , Serina Endopeptidases/metabolismoRESUMO
Despite the availability of hundreds of antibiotic drugs, infectious diseases continue to remain one of the most notorious health issues. In addition, the disparity between the spread of multidrug-resistant pathogens and the development of novel classes of antibiotics exemplify an important unmet medical need that can only be addressed by identifying novel targets. Herein we demonstrate, by the development of the first inâ vivo active DegS inhibitors based on a pyrazolo[1,5-a]-1,3,5-triazine scaffold, that the serine protease DegS and the cell envelope stress-response pathway σE represent a target for generating antibiotics with a novel mode of action. Moreover, DegS inhibition is synergistic with well-established membrane-perturbing antibiotics, thereby opening promising avenues for rational antibiotic drug design.
Assuntos
Antibacterianos/farmacologia , Proteínas de Escherichia coli/antagonistas & inibidores , Escherichia coli/efeitos dos fármacos , Inibidores de Serina Proteinase/farmacologia , Antibacterianos/síntese química , Antibacterianos/química , Relação Dose-Resposta a Droga , Escherichia coli/metabolismo , Proteínas de Escherichia coli/metabolismo , Testes de Sensibilidade Microbiana , Simulação de Acoplamento Molecular , Estrutura Molecular , Inibidores de Serina Proteinase/síntese química , Inibidores de Serina Proteinase/química , Relação Estrutura-AtividadeRESUMO
Covalent modifications of nonactive site lysine residues by small molecule probes has recently evolved into an important strategy for interrogating biological systems. Here, we report the discovery of a class of bioreactive compounds that covalently modify lysine residues in DegS, the rate limiting protease of the essential bacterial outer membrane stress response pathway. These modifications lead to an allosteric activation and allow the identification of novel residues involved in the allosteric activation circuit. These findings were validated by structural analyses via X-ray crystallography and cell-based reporter systems. We anticipate that our findings are not only relevant for a deeper understanding of the structural basis of allosteric activation in DegS and other HtrA serine proteases but also pinpoint an alternative use of covalent small molecules for probing essential biochemical mechanisms.
