RESUMO
Breast cancer resistance protein (BCRP, ABCG2) is an efflux transporter that plays a crucial role in multidrug resistance to antineoplastic drugs. Ko143, an analogue of the natural product fumitremorgin C, is a potent inhibitor of ABCG2 but is rapidly hydrolyzed to an inactive metabolite in vivo. To identify ABCG2 inhibitors with improved metabolic stability, we have assessed a series of Ko143 analogues for their ability to inhibit ABCG2-mediated transport in ABCG2-transduced MDCK II cells and determined the stability of the most potent compounds in liver microsomes. The most promising analogues were evaluated in vivo by positron emission tomography. In vitro, three of the tested analogues were potent ABCG2 inhibitors and stable in microsomes. In vivo, they increased the distribution of the ABCG2/ABCB1 substrate [11C]tariquidar to the brain both in wild-type (with Abcb1a/b transport blocked by tariquidar) and Abcb1a/b(-/-) mice. One analogue was more potent than Ko143 in both animal models.
Assuntos
Transportadores de Cassetes de Ligação de ATP , Antineoplásicos , Camundongos , Animais , Transportadores de Cassetes de Ligação de ATP/metabolismo , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismo , Proteínas de Neoplasias/metabolismo , Encéfalo/metabolismo , Antineoplásicos/farmacologia , Antineoplásicos/metabolismoRESUMO
ABCG2 is an ATP-binding cassette (ABC) transporter that protects tissues against xenobiotics, affects the pharmacokinetics of drugs and contributes to multidrug resistance. Although many inhibitors and modulators of ABCG2 have been developed, understanding their structure-activity relationship requires high-resolution structural insight. Here, we present cryo-EM structures of human ABCG2 bound to synthetic derivatives of the fumitremorgin C-related inhibitor Ko143 or the multidrug resistance modulator tariquidar. Both compounds are bound to the central, inward-facing cavity of ABCG2, blocking access for substrates and preventing conformational changes required for ATP hydrolysis. The high resolutions allowed for de novo building of the entire transporter and also revealed tightly bound phospholipids and cholesterol interacting with the lipid-exposed surface of the transmembrane domains (TMDs). Extensive chemical modifications of the Ko143 scaffold combined with in vitro functional analyses revealed the details of ABCG2 interactions with this compound family and provide a basis for the design of novel inhibitors and modulators.
Assuntos
Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/antagonistas & inibidores , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/química , Indóis/química , Proteínas de Neoplasias/antagonistas & inibidores , Proteínas de Neoplasias/química , Quinolinas/química , Trifosfato de Adenosina/química , Sítios de Ligação , Colesterol/química , Microscopia Crioeletrônica , Dicetopiperazinas/química , Desenho de Fármacos , Resistência a Múltiplos Medicamentos , Ensaios de Seleção de Medicamentos Antitumorais , Compostos Heterocíclicos de 4 ou mais Anéis/química , Humanos , Hidrólise , Cinética , Lipídeos/química , Estrutura Molecular , Fosfolipídeos/química , Ligação Proteica , Multimerização Proteica , Relação Estrutura-Atividade , Especificidade por SubstratoRESUMO
Small-molecule hits for the bromodomains of CREBBP and BAZ2B have been identified by scaffold hopping followed by docking of a set of â¼200 compounds containing the acetyl indole scaffold. Chemical synthesis of nearly 30 derivatives has resulted in ligands of representatives of three subfamilies of human bromodomains with favorable ligand efficiency. The X-ray crystal structures of three different bromodomains (CREBBP, BAZ2B, and BRPF1b) in complex with acetyl indole derivatives reveal the influence of the gatekeeper residue on the orientation of small-molecule ligands in the acetyl lysine binding site.