RESUMEN
SEC14 and Spectrin domain-1 (Sestd1) is a synapse protein that exhibits a striking shift from the presynaptic to postsynaptic space as neurons mature postnatally in the mouse hippocampus. Hippocampal pyramidal neurons from mice with global genetic deletion of Sestd1 have reduced dendrite arbors, spines, and excitatory synapses. Electrophysiologically this correlates with cell-autonomous reductions in both AMPA- and NMDA-excitatory postsynaptic currents in individual hippocampal neurons from which Sestd1 has been deleted in vivo. These neurodevelopmental and functional deficits are associated with increased activation of the Rho family GTPases Rac1 and RhoA. Co-immunoprecipitation and mass spectrometry reveal that the Breakpoint Cluster Region protein, a Rho GTPase activating protein (GAP), forms complexes with Sestd1 in brain tissue. This complements earlier findings that Sestd1 can also partner with other Rho family GAPs and guanine nucleotide exchange factors. Our findings demonstrate that Sestd1 is a developmentally dynamic synaptic regulator of Rho GTPases that contributes to dendrite and excitatory synapse formation within differentiating pyramidal neurons of the forebrain.
Asunto(s)
Proteínas Portadoras/metabolismo , Espinas Dendríticas/metabolismo , Neuropéptidos/metabolismo , Prosencéfalo/metabolismo , Proteínas Proto-Oncogénicas c-bcr/metabolismo , Sinapsis/metabolismo , Proteína de Unión al GTP rac1/metabolismo , Animales , Proteínas Portadoras/análisis , Dendritas/química , Dendritas/metabolismo , Espinas Dendríticas/química , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Neurogénesis/fisiología , Neuropéptidos/análisis , Técnicas de Cultivo de Órganos , Prosencéfalo/química , Prosencéfalo/crecimiento & desarrollo , Proteínas Proto-Oncogénicas c-bcr/análisis , Sinapsis/química , Proteína de Unión al GTP rac1/análisisRESUMEN
Genetic and epigenetic defects in Wnt/beta-catenin signaling play important roles in colorectal cancer progression. Here we identify DACT3, a member of the DACT (Dpr/Frodo) gene family, as a negative regulator of Wnt/beta-catenin signaling that is transcriptionally repressed in colorectal cancer. Unlike other Wnt signaling inhibitors that are silenced by DNA methylation, DACT3 repression is associated with bivalent histone modifications. Remarkably, DACT3 expression can be robustly derepressed by a pharmacological combination that simultaneously targets both histone methylation and deacetylation, leading to strong inhibition of Dishevelled (Dvl)-mediated Wnt/beta-catenin signaling and massive apoptosis of colorectal cancer cells. Our study identifies DACT3 as an important regulator of Wnt/beta-catenin signaling in colorectal cancer and suggests a potential strategy for therapeutic control of Wnt/beta-catenin signaling in colorectal cancer.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Neoplasias Colorrectales/metabolismo , Epigénesis Genética , Regulación Neoplásica de la Expresión Génica , Histonas/metabolismo , Transducción de Señal/genética , Proteínas Wnt/metabolismo , beta Catenina/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Adenosina/análogos & derivados , Adenosina/farmacología , Adenosilhomocisteinasa/antagonistas & inhibidores , Adenosilhomocisteinasa/metabolismo , Apoptosis , Azacitidina/análogos & derivados , Azacitidina/farmacología , Neoplasias Colorrectales/tratamiento farmacológico , Neoplasias Colorrectales/enzimología , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología , Metilación de ADN , Metilasas de Modificación del ADN/antagonistas & inhibidores , Metilasas de Modificación del ADN/metabolismo , Decitabina , Proteínas Dishevelled , Regulación hacia Abajo , Inhibidores Enzimáticos/farmacología , Epigénesis Genética/efectos de los fármacos , Perfilación de la Expresión Génica/métodos , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Células HCT116 , Inhibidores de Histona Desacetilasas , Histona Desacetilasas/metabolismo , Humanos , Ácidos Hidroxámicos/farmacología , Análisis de Secuencia por Matrices de Oligonucleótidos , Fosfoproteínas/metabolismo , Regiones Promotoras Genéticas , Reproducibilidad de los Resultados , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/efectos de los fármacos , Transfección , Proteínas Wnt/genética , beta Catenina/genéticaRESUMEN
The number of proteins that serve as Wnt receptors is growing, and Ryk is one of the newest members of this group. Understanding how extracellular Wnt ligands interact with transmembrane receptors to activate intracellular signaling cascades is of broad importance to biology and to human disease because of the roles for Wnt in embryogenesis, cancer, and neural development and plasticity. The functions and properties of Ryk, a receptor tyrosine kinase-like protein, in canonical and noncanonical Wnt signaling are beginning to be uncovered. Biochemical and genetic studies reveal that the extracellular regions of Ryk and Fz can form a mutual ligand-binding domain. It remains to be seen whether Ryk can form similar complexes with other Wnt-binding proteins. If divergent transmembrane proteins can combine interchangeably to form heteromeric Wnt receptor complexes, then a stunning diversity of signaling responses might be mediated through differential expression and localization of these proteins in target cells.
Asunto(s)
Péptidos y Proteínas de Señalización Intercelular/fisiología , Proteínas Tirosina Quinasas Receptoras/fisiología , Receptores de Superficie Celular/fisiología , Animales , Humanos , Transducción de Señal/fisiología , Proteínas WntRESUMEN
Dapper was isolated in a screen for proteins interacting with Dishevelled, a key factor in Wnt signaling. Dapper and Dishevelled colocalize intracellularly and form a complex with Axin, GSK-3, CKI, and beta-catenin. Overexpression of Dapper increases Axin and GSK-3 in this complex, resulting in decreased soluble beta-catenin and decreased activation of beta-catenin-responsive genes. Dapper also inhibits activation by Dishevelled of c-Jun N-terminal kinase (JNK), a component of beta-catenin-independent Frizzled signaling. Inhibition of Dapper activates both beta-catenin-responsive genes and an AP1-responsive promoter, demonstrating that Dapper is a general Dishevelled antagonist. Depletion of maternal Dapper RNA from Xenopus embryos results in loss of notochord and head structures, demonstrating that Dapper is required for normal vertebrate development.