RESUMO
Wnts are evolutionarily conserved ligands that signal at short range to regulate morphogenesis, cell fate, and stem cell renewal. The first and essential steps in Wnt secretion are their O-palmitoleation and subsequent loading onto the dedicated transporter Wntless/evenness interrupted (WLS/Evi). We report the 3.2 Å resolution cryogenic electron microscopy (cryo-EM) structure of palmitoleated human WNT8A in complex with WLS. This is accompanied by biochemical experiments to probe the physiological implications of the observed association. The WLS membrane domain has close structural homology to G protein-coupled receptors (GPCRs). A Wnt hairpin inserts into a conserved hydrophobic cavity in the GPCR-like domain, and the palmitoleate protrudes between two helices into the bilayer. A conformational switch of highly conserved residues on a separate Wnt hairpin might contribute to its transfer to receiving cells. This work provides molecular-level insights into a central mechanism in animal body plan development and stem cell biology.
Assuntos
Peptídeos e Proteínas de Sinalização Intracelular/química , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Receptores Acoplados a Proteínas G/química , Receptores Acoplados a Proteínas G/metabolismo , Proteínas Wnt/metabolismo , Sequência de Aminoácidos , Animais , Dissulfetos/metabolismo , Glicosilação , Humanos , Interações Hidrofóbicas e Hidrofílicas , Peptídeos e Proteínas de Sinalização Intracelular/isolamento & purificação , Modelos Moleculares , Ligação Proteica , Domínios Proteicos , Estrutura Secundária de Proteína , Transporte Proteico , Receptores Acoplados a Proteínas G/isolamento & purificação , Receptores Acoplados a Proteínas G/ultraestrutura , Homologia Estrutural de Proteína , Relação Estrutura-Atividade , Proteínas Wnt/química , Proteínas Wnt/isolamento & purificação , Proteínas Wnt/ultraestruturaRESUMO
Wnts are evolutionarily conserved signaling proteins with essential roles in development and disease that have often been thought to spread between cells and signal at a distance. However, recent studies have challenged this model, and whether long-distance extracellular Wnt dispersal occurs and is biologically relevant is debated. Understanding fundamental aspects of Wnt dispersal has been limited by challenges with observing endogenous ligands in vivo, which has prevented directly testing hypotheses. Here, we have generated functional, fluorescently tagged alleles for a C. elegans Wnt homolog and for the first time visualized a native, long-range Wnt gradient in a living animal. Live imaging of Wnt along with source and responding cell membranes provided support for free, extracellular dispersal. By limiting Wnt transfer between cells, we confirmed that extracellular spreading shapes a long-range gradient and is critical for neuroblast migration. These results provide direct evidence that Wnts spread extracellularly to regulate aspects of long-range signaling.
Assuntos
Caenorhabditis elegans/genética , Movimento Celular/genética , Imagem Molecular/métodos , Proteínas Wnt/genética , Alelos , Animais , Caenorhabditis elegans/crescimento & desenvolvimento , Polaridade Celular/genética , Espaço Extracelular/genética , Regulação da Expressão Gênica no Desenvolvimento , Peptídeos e Proteínas de Sinalização Intracelular/genética , Ligantes , Proteínas Wnt/química , Proteínas Wnt/ultraestrutura , Via de Sinalização Wnt/genética , beta Catenina/genéticaRESUMO
Wnt signaling plays an important role in the adult brain function and its dysregulation has been implicated in some neurodegenerative pathways. Despite the functional role of the Wnt signaling in adult neural circuits, there is currently no evidence regarding the relationships between exogenously Wnt signaling activation or inhibition and hippocampal structural changes in vivo. Thus, we analyzed the effect of the chronic infusion of Wnt agonists, Wnt7a and Wnt5a, and antagonist, Dkk-1, on different markers of plasticity such as neuronal MAP-2, Tau, synapse number and morphology, and behavioral changes. We observed that Wnt7a and Wnt5a increased the number of perforated synapses and the content of pre-and postsynaptic proteins associated with synapse assembly compared to control and Dkk-1 infusion. These two Wnt agonists also reduced anxiety-like behavior. Conversely, the canonical antagonist, Dkk-1, increased anxiety and inhibited spatial memory recall. Therefore, the present study elucidates the potential participation of Wnt signaling in the remodeling of hippocampal circuits underlying plasticity events in vivo, and provides evidence of the potential benefits of Wnt agonist infusion for the treatment of some neurodegenerative conditions.
Assuntos
Ansiedade/terapia , Hipocampo/efeitos dos fármacos , Peptídeos e Proteínas de Sinalização Intercelular/uso terapêutico , Memória/efeitos dos fármacos , Proteínas Wnt/uso terapêutico , Proteína Wnt-5a/uso terapêutico , Animais , Linhagem Celular Tumoral , Modelos Animais de Doenças , Comportamento Exploratório/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Hipocampo/metabolismo , Hipocampo/ultraestrutura , Humanos , Masculino , Proteínas Associadas aos Microtúbulos/metabolismo , Neuroblastoma/patologia , Ratos , Ratos Wistar , Transdução de Sinais/efeitos dos fármacos , Memória Espacial/efeitos dos fármacos , Sinapses/metabolismo , Sinapses/ultraestrutura , Proteínas Wnt/ultraestrutura , Proteína Wnt-5a/ultraestruturaRESUMO
During vertebrate embryogenesis, specialized mesodermal structures, called somites, give rise to a variety of mesodermal tissues including skeletal muscles, vertebrae and dermis. Development of the somites is a rhythmic process that involves a series of steps including segmentation of the paraxial mesoderm, epithelialization, somite formation, somite maturation, somite patterning and differentiation of somitic cells into different lineages. Wnt signaling has been found to play crucial roles in multiple steps of somite development. In this review, we present a brief overview of current knowledge on Wnt signaling events during the development of somites and their derivatives.
