The cytoplasmic SYNCRIP mRNA interactome of mammalian neurons
RNA BIOLOGY
Authors: Khudayberdiev, Sharof; Soutschek, Michael; Ammann, Irina; Heinze, Anika; Rust, Marco B.; Baumeister, Stefan; Schratt, Gerhard
Abstract
SYNCRIP, a member of the cellular heterogeneous nuclear ribonucleoprotein (hnRNP) family of RNA binding proteins, regulates various aspects of neuronal development and plasticity. Although SYNCRIP has been identified as a component of cytoplasmic RNA granules in dendrites of mammalian neurons, only little is known about the specific SYNCRIP target mRNAs that mediate its effect on neuronal morphogenesis and function. Here, we present a comprehensive characterization of the cytoplasmic SYNCRIP mRNA interactome using iCLIP in primary rat cortical neurons. We identify hundreds of bona fide SYNCRIP target mRNAs, many of which encode for proteins involved in neurogenesis, neuronal migration and neurite outgrowth. From our analysis, the stabilization of mRNAs encoding for components of the microtubule network, such as doublecortin (Dcx), emerges as a novel mechanism of SYNCRIP function in addition to the previously reported control of actin dynamics. Furthermore, we found that SYNCRIP synergizes with pro-neural miRNAs, such as miR-9. Thus, SYNCRIP appears to promote early neuronal differentiation by a two-tier mechanism involving the stabilization of pro-neural mRNAs by direct 3MODIFIER LETTER PRIMEUTR interaction and the repression of anti-neural mRNAs in a complex with neuronal miRISC. Together, our findings provide a rationale for future studies investigating the function of SYNCRIP in mammalian brain development and disease.
alpha 7nAchR mediates transcutaneous auricular vagus nerve stimulation-induced neuroprotection in a rat model of ischemic stroke by enhancing axonal plasticity
NEUROSCIENCE LETTERS
Authors: Li, Jiani; Zhang, Qinbin; Li, Sheng; Niu, Lingchuan; Ma, Jingxi; Wen, Lan; Zhang, Lina; Li, Changqing
Abstract
Axonal plasticity is important for neurofunctional recovery after stroke. This study aimed to explore the role of transcutaneous auricular vagus nerve stimulation (ta-VNS) on axonal plasticity and its underlying association with the alpha 7 nicotinic acetylcholine receptor(alpha 7nAchR) after cerebral ischemia/reperfusion (I/R) injury. Adult male Sprague-Dawley rats were pretreated by intraperitoneal injection with either phosphate-buffered saline (PBS) or an alpha 7nAchR antagonist and then subjected to middle cerebral artery occlusion and ta-VNS treatment. alpha 7nAchR expression and localization in the peri-infarct cortex were examined after ta-VNS treatment. Subsequently, neurologic scores were assessed with a battery of tests. Axonal regeneration, indicated by upregulation of growth-associated protein 43 (GAP-43) and neurofilament protein 200 (NF-200), was assessed. Axonal reorganization was examined on the basis of anterograde movement of the neuronal molecular probe biotin dextran amine. Additionally, brain-derived neurotrophic factor (BDNF)-associated signaling was measured 28d after I/R. Our findings showed that ta-VNS treatment enhanced alpha 7nAchR expression in the ischemic cortex. alpha 7nAchR colocalized with DCX and Nestin after reperfusion. Furthermore, ta-VNS-treated I/R rats displayed enhanced neurobehavioral performance and increased axonal plasticity (axonal regeneration and axonal reorganization), as indicated by elevated levels of BDNF/cyclic AMP (cAMP)/protein kinase A (PKA)/phosphorylated cAMP response element-binding protein pathway (p-CREB) pathway members. Strikingly, the beneficial effects of ta-VNS were diminished after alpha 7nAchR blockade. In conclusion, our study is the first to show that alpha 7nAchR is a potential mediator of ta-VNS-induced neuroprotection in the chronic phase of stroke and that its effects may be related to enhanced axonal plasticity through activation of the BDNF/cAMP/PKA/p-CREB pathway.