RESUMO
Activity-dependent remodeling of excitatory connections underpins memory formation in the brain. Serotonin receptors are known to contribute to such remodeling, yet the underlying molecular machinery remains poorly understood. Here, we employ high-resolution time-lapse FRET imaging in neuroblastoma cells and neuronal dendrites to establish that activation of serotonin receptor 5-HT4 (5-HT4R) rapidly triggers spatially-restricted RhoA activity and G13-mediated phosphorylation of cofilin, thus locally boosting the filamentous actin fraction. In neuroblastoma cells, this leads to cell rounding and neurite retraction. In hippocampal neurons in situ, 5-HT4R-mediated RhoA activation triggers maturation of dendritic spines. This is paralleled by RhoA-dependent, transient alterations in cell excitability, as reflected by increased spontaneous synaptic activity, apparent shunting of evoked synaptic responses, and enhanced long-term potentiation of excitatory transmission. The 5-HT4R/G13/RhoA signaling thus emerges as a previously unrecognized molecular pathway underpinning use-dependent functional remodeling of excitatory synaptic connections.
Assuntos
Actinas/metabolismo , Espinhas Dendríticas/fisiologia , Receptores 5-HT4 de Serotonina/fisiologia , Sinapses/fisiologia , Proteína rhoA de Ligação ao GTP/fisiologia , Citoesqueleto de Actina/metabolismo , Citoesqueleto de Actina/fisiologia , Animais , Animais Recém-Nascidos , Células Cultivadas , Feminino , Potenciação de Longa Duração , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores 5-HT4 de Serotonina/genética , Transdução de Sinais/genética , Transmissão Sináptica/fisiologiaRESUMO
Intersectin 1 (ITSN1) is a multidomain adaptor protein that functions in clathrin-mediated endocytosis and signal transduction. This protein is highly abundant in neurons and is implicated in Down syndrome, Alzheimer's disease and, possibly, other neurodegenerative disorders. Here we used an in vitro binding assay combined with MALDI-TOF mass spectrometry to identify novel binding partners of ITSN1. We found that the neuron-specific isoform of the stable tubule-only polypeptide (STOP) interacts with SH3A domain of ITSN1. STOP and ITSN1 were shown to form a complex in vivo and to partially co-localize in rat primary hippocampal neurons. As STOP is a microtubule-stabilizing protein that is required for several forms of synaptic plasticity in the hippocampus, identification of this interaction raises the possibility of ITSN1 participation in this process.