RESUMEN
The vast majority of intracellular protein targets are refractory toward small-molecule therapeutic engagement, and additional therapeutic modalities are needed to overcome this deficiency. Here, the identification and characterization of a natural product, WDB002, reveals a therapeutic modality that dramatically expands the currently accepted limits of druggability. WDB002, in complex with the FK506-binding protein (FKBP12), potently and selectively binds the human centrosomal protein 250 (CEP250), resulting in disruption of CEP250 function in cells. The recognition mode is unprecedented in that the targeted domain of CEP250 is a coiled coil and is topologically featureless, embodying both a structural motif and surface topology previously considered on the extreme limits of "undruggability" for an intracellular target. Structural studies reveal extensive protein-WDB002 and protein-protein contacts, with the latter being distinct from those seen in FKBP12 ternary complexes formed by FK506 and rapamycin. Outward-facing structural changes in a bound small molecule can thus reprogram FKBP12 to engage diverse, otherwise "undruggable" targets. The flat-targeting modality demonstrated here has the potential to expand the druggable target range of small-molecule therapeutics. As CEP250 was recently found to be an interaction partner with the Nsp13 protein of the SARS-CoV-2 virus that causes COVID-19 disease, it is possible that WDB002 or an analog may exert useful antiviral activity through its ability to form high-affinity ternary complexes containing CEP250 and FKBP12.
Asunto(s)
Actinobacteria/genética , Antivirales/farmacología , Genoma Bacteriano , Macrólidos/farmacología , Dominios y Motivos de Interacción de Proteínas/efectos de los fármacos , Bibliotecas de Moléculas Pequeñas/farmacología , Proteína 1A de Unión a Tacrolimus/química , Proteína 1A de Unión a Tacrolimus/metabolismo , Actinobacteria/metabolismo , Secuencia de Aminoácidos , Antivirales/química , Antivirales/metabolismo , Autoantígenos/genética , Autoantígenos/metabolismo , Calcineurina/genética , Calcineurina/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Evolución Molecular , Células HEK293 , Humanos , Macrólidos/química , Macrólidos/metabolismo , Modelos Moleculares , Conformación Proteica , Homología de Secuencia , Sirolimus/química , Sirolimus/metabolismo , Bibliotecas de Moléculas Pequeñas/química , Bibliotecas de Moléculas Pequeñas/metabolismo , Serina-Treonina Quinasas TOR/genética , Serina-Treonina Quinasas TOR/metabolismoRESUMEN
Multiple pathways have been proposed to explain how proteasome inhibition induces cell death, but mechanisms remain unclear. To approach this issue, we performed a genome-wide siRNA screen to evaluate the genetic determinants that confer sensitivity to bortezomib (Velcade (R); PS-341). This screen identified 100 genes whose knockdown affected lethality to bortezomib and to a structurally diverse set of other proteasome inhibitors. A comparison of three cell lines revealed that 39 of 100 genes were commonly linked to cell death. We causally linked bortezomib-induced cell death to the accumulation of ASF1B, Myc, ODC1, Noxa, BNIP3, Gadd45alpha, p-SMC1A, SREBF1, and p53. Our results suggest that proteasome inhibition promotes cell death primarily by dysregulating Myc and polyamines, interfering with protein translation, and disrupting essential DNA damage repair pathways, leading to programmed cell death.