Reti Irving M, Reddy Radhika, Worley Paul F, Baraban Jay M
Department of Psychiatry, Neuroscience and Neurology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
J Neurochem. 2002 Aug;82(4):935-44. doi: 10.1046/j.1471-4159.2002.01051.x.
Narp (neuronal activity regulated pentraxin) is a secreted immediate early gene product that is induced by synaptic activity. Recent studies have indicated that Narp may be an extracellular aggregating factor for AMPA receptors. Immunohistochemical studies have revealed prominent expression of Narp in the mossy fiber pathway of the dentate gyrus, suggesting it may be released pre-synaptically. However, in vitro studies using recombinant Narp indicate that Narp may act when expressed by either pre- or post-synaptic elements. To help define Narp's mode of action, we have examined its localization in the habenula-interpeduncular pathway which also displays robust Narp expression. Focusing on this pathway as well as hippocampal and cortical Narp expression, we found prominent Narp staining in projection pathways and terminal fields. In contrast, Narp expression in dendrites was minimal in these neuronal populations. These findings indicate that, under physiological conditions, Narp is targeted to the synapse from pre- rather than post-synaptic elements. Our results also suggest that future studies focusing on these projection pathways that express high levels of Narp, in vivo, may help to understand the regulation and function of endogenous Narp.
神经元活性调节五聚体蛋白（Narp）是一种由突触活性诱导产生的分泌型即早基因产物。最近的研究表明，Narp可能是AMPA受体的一种细胞外聚集因子。免疫组织化学研究显示，Narp在齿状回的苔藓纤维通路中表达显著，提示其可能在突触前释放。然而，使用重组Narp的体外研究表明，Narp在由突触前或突触后元件表达时均可能发挥作用。为了帮助确定Narp的作用模式，我们研究了其在缰核-脚间通路中的定位，该通路也有较强的Narp表达。聚焦于该通路以及海马和皮质中的Narp表达，我们发现在投射通路和终末区域有显著的Narp染色。相比之下，在这些神经元群体中，树突中的Narp表达极少。这些发现表明，在生理条件下，Narp是从突触前而非突触后元件靶向到突触的。我们的结果还表明，未来在体内针对这些高表达Narp的投射通路开展的研究，可能有助于理解内源性Narp的调节和功能。
