RESUMO
The motor neuron disease spinal muscular atrophy (SMA) results from mutations that lead to low levels of the ubiquitously expressed protein survival of motor neuron (SMN). An ever-increasing collection of data suggests that therapeutics that elevate SMN may be effective in treating SMA. We executed an image-based screen of annotated chemical libraries and discovered several classes of compounds that were able to increase cellular SMN. Among the most important was the RTK-PI3K-AKT-GSK-3 signaling cascade. Chemical inhibitors of glycogen synthase kinase 3 (GSK-3) and short hairpin RNAs (shRNAs) directed against this target elevated SMN levels primarily by stabilizing the protein. It was particularly notable that GSK-3 chemical inhibitors were also effective in motor neurons, not only in elevating SMN levels, but also in blocking the death that was produced when SMN was acutely reduced by an SMN-specific shRNA. Thus, we have established a screen capable of detecting drug-like compounds that correct the main phenotypic change underlying SMA.
Assuntos
Descoberta de Drogas/métodos , Regulação da Expressão Gênica/efeitos dos fármacos , Atrofia Muscular Espinal/tratamento farmacológico , Proteína 1 de Sobrevivência do Neurônio Motor/metabolismo , Adulto , Animais , Benzazepinas/farmacologia , Células Cultivadas , Pré-Escolar , Células-Tronco Embrionárias , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Regulação da Expressão Gênica/fisiologia , Inativação Gênica , Quinase 3 da Glicogênio Sintase/antagonistas & inibidores , Glicogênio Sintase Quinase 3 beta , Humanos , Indóis/farmacologia , Camundongos , Neurônios Motores/metabolismo , Atrofia Muscular Espinal/metabolismo , Mutação , Fator de Crescimento Derivado de Plaquetas/farmacologia , Fator de Transcrição STAT1 , Bibliotecas de Moléculas Pequenas , Proteína 1 de Sobrevivência do Neurônio Motor/genética , Proteína 2 de Sobrevivência do Neurônio Motor/genética , Proteína 2 de Sobrevivência do Neurônio Motor/metabolismoRESUMO
Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disease, characterized by motor neuron (MN) death, for which there are no truly effective treatments. Here, we describe a new small molecule survival screen carried out using MNs from both wild-type and mutant SOD1 mouse embryonic stem cells. Among the hits we found, kenpaullone had a particularly impressive ability to prolong the healthy survival of both types of MNs that can be attributed to its dual inhibition of GSK-3 and HGK kinases. Furthermore, kenpaullone also strongly improved the survival of human MNs derived from ALS-patient-induced pluripotent stem cells and was more active than either of two compounds, olesoxime and dexpramipexole, that recently failed in ALS clinical trials. Our studies demonstrate the value of a stem cell approach to drug discovery and point to a new paradigm for identification and preclinical testing of future ALS therapeutics.