RESUMEN
Terminally differentiated neurons have a single, primary cilium. The primary cilia of hypothalamic neurons play a critical role in sensing metabolic signals. We recently showed that mice with leptin deficiency or resistance have shorter cilia in the hypothalamic neurons, and leptin treatment elongates cilia in hypothalamic neurons. Here, we investigated the molecular mechanisms by which leptin controls ciliary length in hypothalamic neurons. In N1 hypothalamic neuronal cells, leptin treatment increased the expression of intraflagellar transport proteins. These effects occurred via phosphatase and tensin homolog/glycogen synthase kinase-3ß-mediated inhibition of the transcriptional factor RFX1. Actin filament dynamics were also involved in leptin-promoted ciliary elongation. Both leptin and cytochalasin-D treatment induced F-actin disruption and cilium elongation in hypothalamic neurons that was completely abrogated by co-treatment with the F-actin polymerizer phalloidin. Our findings suggest that leptin elongates hypothalamic neuronal cilia by stimulating the production of intraflagellar transport proteins and destabilizing actin filaments.
Asunto(s)
Actinas/metabolismo , Cilios/metabolismo , Hipotálamo/citología , Leptina/metabolismo , Neuronas/citología , Actinas/ultraestructura , Animales , Línea Celular , Línea Celular Tumoral , Cilios/ultraestructura , Regulación de la Expresión Génica , Glucógeno Sintasa Quinasa 3/metabolismo , Glucógeno Sintasa Quinasa 3 beta , Humanos , Hipotálamo/metabolismo , Ratones , Neuronas/metabolismo , Fosfohidrolasa PTEN/metabolismoRESUMEN
The majority of mammalian cells have nonmotile primary cilia on their surface that act as antenna-like sensory organelles. Genetic defects that result in ciliary dysfunction are associated with obesity in humans and rodents, which suggests that functional cilia are important for controlling energy balance. Here we demonstrated that neuronal cilia lengths were selectively reduced in hypothalami of obese mice with leptin deficiency and leptin resistance. Treatment of N1 hypothalamic neuron cells with leptin stimulated cilia assembly via inhibition of the tumor suppressors PTEN and glycogen synthase kinase 3ß (GSK3ß). Induction of short cilia in the hypothalamus of adult mice increased food intake and decreased energy expenditure, leading to a positive energy balance. Moreover, mice with short hypothalamic cilia exhibited attenuated anorectic responses to leptin, insulin, and glucose, which indicates that leptin-induced cilia assembly is essential for sensing these satiety signals by hypothalamic neurons. These data suggest that leptin governs the sensitivity of hypothalamic neurons to metabolic signals by controlling the length of the cell's antenna.
Asunto(s)
Metabolismo Energético/fisiología , Hipotálamo/metabolismo , Neuronas/metabolismo , Animales , Anorexia/genética , Anorexia/metabolismo , Línea Celular , Cilios/genética , Cilios/metabolismo , Glucosa/genética , Glucosa/metabolismo , Glucógeno Sintasa Quinasa 3/genética , Glucógeno Sintasa Quinasa 3/metabolismo , Glucógeno Sintasa Quinasa 3 beta , Hipotálamo/citología , Insulina/genética , Insulina/metabolismo , Leptina , Ratones , Ratones Noqueados , Neuronas/citología , Fosfohidrolasa PTEN/genética , Fosfohidrolasa PTEN/metabolismoRESUMEN
Protein tyrosine phosphatase 1B plays a major role in the negative regulation of insulin signaling, and this establishes protein tyrosine phosphatase 1B as an attractive therapeutic target for diabetes. Bioassay-guided fractionation of the EtOAc-soluble extract of the seeds of Psoralea corylifolia afforded two protein tyrosine phosphatase 1B inhibitory compounds, psoralidin (1) and bakuchiol (2), along with inactive corylin. Compounds 1 and 2 inhibited PTP1B activity in a dose-dependent manner, displaying IC50 values of 9.4 +/- 0.5 microM and 20.8 +/- 1.9 microM, respectively.