TrkA与snapin蛋白的直接相互作用

目的确认TrkA与snapin蛋白间的直接相互作用。方法采用DNA重组技术,构建增强型荧光蛋白表达载体pECFP-TrkAICD(TrkA膜内区)和pEYFP-snapin,共转染HEK 293T细胞后以激光扫描共聚焦显微镜观察并进行荧光共振能量转移(fluorescence resonance energy transfer,FRET)分析。结果成功构建了snapin和TrkA的重组质粒,共转染细胞后激光扫描共聚焦显微镜分析表明两种蛋白分布在细胞质同一层面,荧光共振能量转移(FRET)分析表明能量转移效率>5%,与对照相比有显著区别(P<0.05)。结论激光扫描共聚焦及FRET实验结果都证明了TrkA膜内区与snapin两个蛋白之间存在着直接的相互作用。     

The ubiquitin proteasome system in neurodegenerative diseases: Culprit,accomplice or victim?

A shared hallmark for many neurodegenerative disorders is the accumulation of toxic protein species which is assumed to be the cause for these diseases. Since the ubiquitin proteasome system (UPS) is the most important pathway for selective protein degradation it is likely that it is involved in the aetiology neurodegenerative disorders. Indeed, impairment of the UPS has been reported to occur during neurodegeneration. Although accumulation of toxic protein species (amyloid β) are in turn known to impair the UPS the relationship is not necessarily causal. We provide an overview of the most recent insights in the roles the UPS plays in protein degradation and other processes. Additionally, we discuss the role of the UPS in clearance of the toxic proteins known to accumulate in the hallmarks of neurodegenerative diseases. The present paper will focus on critically reviewing the involvement of the UPS in specific neurodegenerative diseases and will discuss if UPS impairment is a cause, a consequence or both of the disease.     

TrkB inhibition as a therapeutic target for CNS-related disorders

The interaction of brain-derived neurotrophic factor (BDNF) with its tropomyosin-related kinase receptor B (TrkB) is involved in fundamental cellular processes including neuronal proliferation, differentiation and survival as well as neurotransmitter release and synaptic plasticity. TrkB signaling has been widely associated with beneficial, trophic effects and many commonly used psychotropic drugs aim to increase BDNF levels in the brain. However, it is likely that a prolonged increased TrkB activation is observed in many pathological conditions, which may underlie the development and course of clinical symptoms. Interestingly, genetic and pharmacological studies aiming at decreasing TrkB activation in rodent models mimicking human pathology have demonstrated a promising therapeutic landscape for TrkB inhibitors in the treatment of various diseases, e.g. central nervous system (CNS) disorders and several types of cancer. Up to date, only a few selective and potent TrkB inhibitors have been developed. As such, the use of crystallography and in silico approaches to model BDNF-TrkB interaction and to generate relevant pharmacophores represent powerful tools to develop novel compounds targeting the TrkB receptor.     

Nerve growth factor and the physiology of pain: lessons from congenital insensitivity to pain with anhidrosis

Congenital insensitivity to pain with anhidrosis (CIPA) is an autosomal recessive genetic disorder characterized by insensitivity to pain, anhidrosis (the inability to sweat) and mental retardation. Nerve growth factor (NGF) is a well-known neurotrophic factor essential for the survival and maintenance of NGF-dependent neurons, including primary afferent neurons with thin fibers and sympathetic postganglionic neurons, during development. NGF is also considered to be an inflammatory mediator associated with pain, itch and inflammation in adults. CIPA results from loss-of-function mutations in the NTRK1 gene-encoding TrkA (tropomyosin-related kinase A), a receptor tyrosine kinase for NGF. Defects in NGF-TrkA signal transduction lead to the failure of survival of various NGF-dependent neurons. As a result, patients with CIPA lack NGF-dependent neurons. Recent studies have revealed that mutations in the NGFB gene-encoding NGF protein also cause congenital insensitivity to pain. Using the pathophysiology of CIPA as a foundation, this review investigates the ways in which NGF-dependent neurons contribute to interoception, homeostasis and emotional responses and, together with the brain, immune and endocrine systems, play crucial roles in pain, itch and inflammation. The NGF-TrkA system is essential for the establishment of neural networks for interoception, homeostasis and emotional responses. These networks mediate reciprocal communication between the brain and the body in humans.     

Improved neural microcirculation and regeneration after peripheral nerve decompression in DPN rats*

Objective: Recently, neural microcirculation and regeneration were regarded as critical factors in diabetic peripheral neuropathy (DPN) improvement. In the present study, we explored the cytological and molecular mechanisms how peripheral nerve decompression impaired nerve injury.

Methods: Forty-five male SD rats were established as the DPN model. HE staining was used to observe the morphology and distribution of microvessels. Transmission electron microscopy was applied to observe the morphology and distribution of Schwann cells. Immunohistochemical staining was performed to measure nerve growth factor (NGF), tyrosine kinase receptor A (TrkA) and growth-associated protein 43 (GAP-43) in the distal sciatic nerve.

Results: Distribution of microvessels and Schwann cells decreased in the DPN group (p < 0.05). NGF, TrkA and GAP-43 also decreased significantly in the DPN group (p < 0.05). NGF, TrkA, GAP-43 and distribution of microvessels and Schwann cells increased in the decompressed group (p < 0.05).

Discussion: In DPN rats, after nerves are compressed, microcirculation disturbance and hypoxia ischemia will happen, which cause decreased expression of NGF, TrkA and GAP-43. Finally, the self-healing function of compressed nerves is impacted. Conversely, nerve decompression can improve neural microcirculation and regeneration and change the former pathological process.     

Thymocyte depletion affects neurotrophin receptor expression in thymic stromal cells

Thymocytes and thymic stromal cells cross-talk in a bidirectional manner within the thymus, thus contributing to the generation of mature T-cells. The thymic stromal cells in the rat express the high- (TrkA, TrkB) and low-affinity (p75NTR) receptors for neurotrophins. In this study we analysed the regulation of TrkA, TrkB and p75NTR expression in the rat thymus by thymocytes. We induced thymocyte apoptosis by administration of corticoids in rats, and then analysed the expression and distribution of these receptors 1, 4 and 10 days later. Thymocyte death was assessed by the activation of caspase-3 in cells undergoing apoptosis. We observed massive thymocyte apoptosis 1 day after injection and, to a lesser extent, after 4 days, which was parallel with a reduction in the density of thymic epithelial cells normally expressing TrkA and p75NTR. Furthermore, TrkA expression was found in cortical thymic epithelial cells, which normally lack this receptor. The expression of TrkB was restricted to a subset of macrophage-dendritic cells, and remained unchanged with treatment. The normal pattern of neurotrophin receptor expression was almost completely restored by day 10. The results demonstrate that the expression of neurotrophin receptors by thymic epithelial cells, but not by macrophage-dendritic cells, is regulated by thymocytes.     

电离辐射对大鼠海马区神经发生及TrkA和TrkB表达的影响

目的 探讨电离辐射对大鼠海马区神经发生以及TrkA、TrkB蛋白表达的影响。方法 将56只SD大鼠按随机数字表法分为照射组（28只）和健康对照组（28只）,照射组给予单次10 Gy全脑照射。分别于照后1、3 d,2周以及1个月取海马组织,应用免疫荧光染色观察神经元增殖变化,Golgi染色观察海马树突棘形态变化,Western blot及RT-PCR分别检测TrkA、TrkB蛋白及RNA水平变化。结果 与健康对照组比较,免疫荧光染色显示照射组双皮质素（DCX）数量明显减少（t=6.49,P<0.05）。照射组海马树突棘明显减少,且树突棘的形态变化明显。与健康对照组相比,照后不同时间照射组TrkA蛋白表达明显升高（t=2.64、3.06、4.80、2.64, P<0.05）,而TrkB的表达则显著下降（t=4.59、3.06、2.81、2.57, P<0.05）;TrkA mRNA表达水平明显升高（t=4.57、3.06、5.39、5.86, P<0.05）,TrkB的表达显著下降（t=14.87、11.69、4.98,P<0.05）。结论 作为神经生长因子、脑源性神经因子重要的下游信号通路分子,全脑照射后TrkA、TrkB的表达变化,可能在电离辐射所致海马神经发生损伤中发挥重要作用。     

Glaucoma alters the expression of NGF and NGF receptors in visual cortex and geniculate nucleus of rats: effect of eye NGF application

We investigated the effect of glaucoma (GL) on nerve growth factor (NGF) presence in two brain visual areas. Rats with elevated intraocular pressure (EIOP), induced by hypertonic saline injection in the episcleral vein, were treated with eye topical application of saline or NGF. Rats were subsequently sacrificed, and brain tissues were used for immunohistochemical, biochemical, and molecular analyses. We found that GL alters the basal level of NGF and NGF receptors in brain visual centers and that NGF eye application normalized these deficits. These findings demonstrate that the reduced presence of NGF can arise due to degenerative events in retinal and brain visual areas.     

脊髓减压病对大鼠TNF-α、NGF及TrkA表达的影响

潜水医学中,发生在中枢神经系统的减压病以脊髓减压病较为多见.在失事潜艇的艇员脱险时,往往由于没有立即救治的条件,使脊髓减压病成为减员的重要原因之一[1].本实验通过对脊髓减压病大鼠NGF、TrkA和TNF-α蛋白表达的观察,分析减压病致脊髓损伤的自身保护因素与加重损伤的因素,及其时间分布的特点,认识脊髓减压病的发病规律,为治疗脊髓减压病提供理论依据.     

TrkA及PPTA mRNA在咬合创伤犬三叉神经节内的表达变化

目的：观察咬合创伤时犬三叉神经节（TG）中神经生长因子受体TrkA mRNA及前速激肽原－A（PPTA） mRNA的表达变化，探讨咬合创伤导致口面痛的可能机制。方法：将高出咬合面1.5mm的镍铬合金嵌体粘固于10只杂种犬右侧上颌第一，二磨牙咬合面的一类嵌体洞形内，造成对He牙的创伤。粘固嵌体后3，7，14，30，60天时取双侧TG。用反转录－聚合酶链式反应（RT＿PCR）检测 TG中Trk A及PPTA mRNA的表达变化并与无咬合创伤的对照组作比较。结果：（1）创伤后3－60天内创伤侧TG的Trk A和PPTA mRNA表达水平比对侧明显上调。（2）创伤侧TrkA mRNA的表达量在3－60天内均高于对照组，7－30天内维持较高水平。（3）3－30天内PPTA mRNA水平明显高地对照组，3－14天达到最高，60天组与对照无差异。结论：咬合创伤能导致TG内TrkA mRNA及PPTA mRNA表达水平的上调。Trk A和PPTA可能参与了咬合创伤所导致的口面痛。