RESUMO
Spatiotemporal regulation of neuronal gene expression is essential for proper functioning of neuronal circuits. In this issue of Neuron, Sharma et al. (2019) discover a dual role for Arnt2-NcoR2 protein complexes in the activity-dependent regulation of neuronal transcriptomes.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Neurônios , Translocador Nuclear Receptor Aril Hidrocarboneto , Expressão GênicaRESUMO
Proper establishment of synapses is critical for constructing functional circuits. Interactions between presynaptic neurexins and postsynaptic neuroligins coordinate the formation of synaptic adhesions. An isoform code determines the direct interactions of neurexins and neuroligins across the synapse. However, whether extracellular linker proteins can expand such a code is unknown. Using a combination of in vitro and in vivo approaches, we found that hevin, an astrocyte-secreted synaptogenic protein, assembles glutamatergic synapses by bridging neurexin-1alpha and neuroligin-1B, two isoforms that do not interact with each other. Bridging of neurexin-1alpha and neuroligin-1B via hevin is critical for the formation and plasticity of thalamocortical connections in the developing visual cortex. These results show that astrocytes promote the formation of synapses by modulating neurexin/neuroligin adhesions through hevin secretion. Our findings also provide an important mechanistic insight into how mutations in these genes may lead to circuit dysfunction in diseases such as autism.
Assuntos
Astrócitos/metabolismo , Proteínas de Ligação ao Cálcio/metabolismo , Moléculas de Adesão Celular Neuronais/metabolismo , Proteínas da Matriz Extracelular/metabolismo , Moléculas de Adesão de Célula Nervosa/metabolismo , Tálamo/metabolismo , Animais , Células COS , Chlorocebus aethiops , Dominância Ocular , Humanos , Camundongos , Camundongos Knockout , Doenças do Sistema Nervoso/metabolismo , Neurônios/metabolismo , Isoformas de Proteínas/metabolismo , Transdução de Sinais , Sinapses/metabolismoRESUMO
Neuroligin-1 is a potent trigger for the de novo formation of synaptic connections, and it has recently been suggested that it is required for the maturation of functionally competent excitatory synapses. Despite evidence for the role of neuroligin-1 in specifying excitatory synapses, the underlying molecular mechanisms and physiological consequences that neuroligin-1 may have at mature synapses of normal adult animals remain unknown. By silencing endogenous neuroligin-1 acutely in the amygdala of live behaving animals, we have found that neuroligin-1 is required for the storage of associative fear memory. Subsequent cellular physiological studies showed that suppression of neuroligin-1 reduces NMDA receptor-mediated currents and prevents the expression of long-term potentiation without affecting basal synaptic connectivity at the thalamo-amygdala pathway. These results indicate that persistent expression of neuroligin-1 is required for the maintenance of NMDAR-mediated synaptic transmission, which enables normal development of synaptic plasticity and long-term memory in the amygdala of adult animals.