RESUMEN
Dysregulation of transforming growth factor-beta (TGF-beta) signaling has been implicated in the pathogenesis of a variety of diseases including cancer; therefore, pharmacological inhibitors that target the TGF-beta signaling pathway might be promising drugs for disease therapy. In this study, we investigated the mechanism of inhibition of TGF-beta signaling by the Hsp90 inhibitor geldanamycin (GA). Treatment with GA suppressed TGF-beta signaling, as evidenced by inhibition of TGF-beta-induced phosphorylation and transcriptional activity of Smad3 and decreased induction of target genes. Western blot analysis revealed that GA induced degradation of TGF-beta type I and type II receptors through a proteasome-dependent pathway. Notably, induction of Hsp70 by GA correlated with inhibition of TGF-beta signaling. Suppression of Hsp70 expression by Hsp70 siRNA or KNK437, an inhibitor of Hsp70 synthesis, blocked the inhibition of TGF-beta signaling by GA. Furthermore, Hsp70 interacted directly with TGF-beta receptors following GA treatment. Our results suggest that GA-mediated induction of Hsp70 and its subsequent interaction with TGF-beta receptors plays a crucial role in inhibition of TGF-beta signaling.
Asunto(s)
Benzoquinonas/farmacología , Proteínas HSP70 de Choque Térmico/metabolismo , Lactamas Macrocíclicas/farmacología , Transducción de Señal/efectos de los fármacos , Factor de Crecimiento Transformador beta/antagonistas & inhibidores , Factor de Crecimiento Transformador beta/metabolismo , Línea Celular , Regulación de la Expresión Génica/efectos de los fármacos , Proteínas HSP70 de Choque Térmico/genética , Humanos , Receptores de Factores de Crecimiento Transformadores beta/genética , Receptores de Factores de Crecimiento Transformadores beta/metabolismo , Proteína Smad2/genética , Proteína Smad2/metabolismo , Proteína smad3/genética , Proteína smad3/metabolismo , Ubiquitinación/efectos de los fármacosRESUMEN
Glutaminyl cyclase (QC) has been implicated in the formation of toxic amyloid plaques by generating the N-terminal pyroglutamate of ß-amyloid peptides (pGlu-Aß) and thus may participate in the pathogenesis of Alzheimer's disease (AD). We designed a library of glutamyl cyclase (QC) inhibitors based on the proposed binding mode of the preferred substrate, Aß3E-42. An in vitro structure-activity relationship study identified several excellent QC inhibitors demonstrating 5- to 40-fold increases in potency compared to a known QC inhibitor. When tested in mouse models of AD, compound 212 significantly reduced the brain concentrations of pyroform Aß and total Aß and restored cognitive functions. This potent Aß-lowering effect was achieved by incorporating an additional binding region into our previously established pharmacophoric model, resulting in strong interactions with the carboxylate group of Glu327 in the QC binding site. Our study offers useful insights in designing novel QC inhibitors as a potential treatment option for AD.