RESUMEN
Liver kinase B1 (LKB1) has important roles in governing energy homeostasis by regulating the activity of the energy sensor kinase AMP-activated protein kinase (AMPK). The regulation of LKB1 function, however, is still poorly understood. Here we demonstrate that the orphan nuclear receptor Nur77 binds and sequesters LKB1 in the nucleus, thereby attenuating AMPK activation. This Nur77 function is antagonized by the chemical compound ethyl 2-[2,3,4-trimethoxy-6-(1-octanoyl)phenyl]acetate (TMPA), which interacts with Nur77 with high affinity and at specific sites. TMPA binding of Nur77 results in the release and shuttling of LKB1 to the cytoplasm to phosphorylate AMPKα. Moreover, TMPA effectively reduces blood glucose and alleviates insulin resistance in type II db/db and high-fat diet- and streptozotocin-induced diabetic mice but not in diabetic littermates with the Nur77 gene knocked out. This study attains a mechanistic understanding of the regulation of LKB1-AMPK axis and implicates Nur77 as a new and amenable target for the design and development of therapeutics to treat metabolic diseases.
Asunto(s)
Proteínas Quinasas Activadas por AMP/metabolismo , Miembro 1 del Grupo A de la Subfamilia 4 de Receptores Nucleares/metabolismo , Fenilacetatos/farmacología , Proteínas Serina-Treonina Quinasas/metabolismo , Quinasas de la Proteína-Quinasa Activada por el AMP , Proteínas Quinasas Activadas por AMP/antagonistas & inhibidores , Animales , Glucemia/efectos de los fármacos , Células Cultivadas , Diabetes Mellitus Experimental/inducido químicamente , Diabetes Mellitus Experimental/tratamiento farmacológico , Diabetes Mellitus Experimental/metabolismo , Activación Enzimática/efectos de los fármacos , Células HEK293 , Humanos , Resistencia a la Insulina , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Obesos , Modelos Moleculares , Miembro 1 del Grupo A de la Subfamilia 4 de Receptores Nucleares/antagonistas & inhibidores , Miembro 1 del Grupo A de la Subfamilia 4 de Receptores Nucleares/genética , Fenilacetatos/química , Fosforilación/efectos de los fármacos , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Transporte de Proteínas/efectos de los fármacos , Estreptozocina , Relación Estructura-ActividadRESUMEN
Six analogous dumbbell-shaped 3d-4f complexes MLn were obtained by the reaction of Ln(NO3)3 (Ln = Eu, Gd, Dy) and M(OAc)2 (M = Co, Ni) without any other organic ligands, and M5Gd4 exhibited a large magnetocaloric effect (-ΔSm = 31.0, 37.3 J kg-1 K-1 for Co5Gd4 and Ni5Gd4 respectively), while M5Dy4 and Co5Eu4 showed single molecule magnet behaviour. To the best of our knowledge, Co5Eu4 is the first Eu-based cluster to display single molecule magnet behaviour (Ueff = 16.4 K).