Kuczewski Nicola, Porcher Christophe, Ferrand Nadine, Fiorentino Hervé, Pellegrino Christophe, Kolarow Richard, Lessmann Volkmar, Medina Igor, Gaiarsa Jean-Luc
Institut de Neurobiologie de la Méditerranée, Inserm Unité 901 and Université de La Méditerranée, 13273 Marseille Cedex 09, France.
J Neurosci. 2008 Jul 2;28(27):7013-23. doi: 10.1523/JNEUROSCI.1673-08.2008.
Brain-derived neurotrophic factor (BDNF) is a major regulator of activity-dependent synapse development and plasticity. Because BDNF is a secreted protein, it has been proposed that BDNF is released from target neurons in an activity-dependent manner. However, direct evidence for postsynaptic release of BDNF triggered by ongoing network activity is still lacking. Here we transfected cultures of dissociated hippocampal neurons with green fluorescent protein (GFP)-tagged BDNF and combined whole-cell recording, time-lapse fluorescent imaging, and immunostaining to monitor activity-dependent dendritic release of BDNF. We found that spontaneous backpropagating action potentials, but not synaptic activity alone, led to a Ca2+-dependent dendritic release of BDNF-GFP. Moreover, we provide evidence that endogenous BDNF released from a single neuron can phosphorylate CREB (cAMP response element-binding protein) in neighboring neurons, an important step of immediate early gene activation. Therefore, together, our results support the hypothesis that BDNF might act as a target-derived messenger of activity-dependent synaptic plasticity and development.
脑源性神经营养因子（BDNF）是活动依赖性突触发育和可塑性的主要调节因子。由于BDNF是一种分泌蛋白，有人提出BDNF以活动依赖性方式从靶神经元释放。然而，仍缺乏由持续的网络活动触发的BDNF突触后释放的直接证据。在这里，我们用绿色荧光蛋白（GFP）标记的BDNF转染解离的海马神经元培养物，并结合全细胞记录、延时荧光成像和免疫染色来监测活动依赖性的BDNF树突释放。我们发现，自发的逆向动作电位，而不是单独的突触活动，导致了BDNF-GFP的Ca2+依赖性树突释放。此外，我们提供的证据表明，从单个神经元释放的内源性BDNF可以使相邻神经元中的CREB（cAMP反应元件结合蛋白）磷酸化，这是即时早期基因激活的重要步骤。因此，我们的结果共同支持了这样一种假设，即BDNF可能作为活动依赖性突触可塑性和发育的靶源性信使。
