RESUMO
Neuronal synapse formation is critical for brain development and depends on secreted factors from astrocytes. Here, we report that small extracellular vesicles (EVs) secreted from primary astrocytes, but not from neurons or C6 glioma cells, greatly enhance spine and synapse formation by primary cortical neurons. A comparative proteomics analysis of small EVs from astrocytes, neurons, and C6 glioma cells identified fibulin-2 as a promising EV cargo to regulate synaptogenesis. Treatment of cortical neurons with recombinant fibulin-2 increased the formation of spines and synapses, similar to the effect of small EVs. In addition, treatment of neurons with fibulin-2 or astrocyte-derived small EVs led to increased phosphorylation of Smad2, an indicator of TGF-ß signaling. Finally, the effects of fibulin-2 and astrocyte-derived small EVs on synapse formation were reversed by inhibiting transforming growth factor ß (TGF-ß) signaling. These data suggest a model in which astrocyte EVs promote synapse formation via fibulin-2-mediated activation of TGF-ß signaling.
Assuntos
Proteínas de Ligação ao Cálcio/metabolismo , Proteínas da Matriz Extracelular/metabolismo , Vesículas Extracelulares/metabolismo , Transdução de Sinais , Sinapses/fisiologia , Animais , Astrócitos/citologia , Astrócitos/metabolismo , Proteínas de Ligação ao Cálcio/antagonistas & inibidores , Proteínas de Ligação ao Cálcio/genética , Células Cultivadas , Espinhas Dendríticas/fisiologia , Proteínas da Matriz Extracelular/antagonistas & inibidores , Proteínas da Matriz Extracelular/genética , Feminino , Proteínas de Choque Térmico HSP70/metabolismo , Humanos , Neurônios/citologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fosforilação/efeitos dos fármacos , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/farmacologia , Transdução de Sinais/efeitos dos fármacos , Proteína Smad2/metabolismo , Fator de Crescimento Transformador beta/metabolismoRESUMO
Dendritic spines and synapses are critical for neuronal communication, and they are perturbed in many neurological disorders; however, the study of these structures in living cells has been hindered by their small size. Super resolution microscopy, unlike conventional light microscopy, is diffraction unlimited and thus is well suited for imaging small structures, such as dendritic spines and synapses. Super resolution microscopy has already revealed important new information about spine and synapse morphology, actin remodeling, and nanodomain composition in both healthy cells and diseased states. In this review, we highlight the advancements in probes that make super resolution more amenable to live-cell imaging of spines and synapses. We also discuss recent data obtained by super resolution microscopy that has advanced our knowledge of dendritic spine and synapse structure, organization, and dynamics in both healthy and diseased contexts. Finally, we propose a series of critical questions for understanding spine and synapse formation and maturation that super resolution microscopy is poised to answer.