阿尔茨海默病大鼠海马胆固醇水平升高对tau蛋白磷酸化程度增加的影响

目的观察海马胆固醇含量升高后tau蛋白磷酸化程度的变化,探讨其在阿尔茨海默病(AD)中可能的作用。方法水迷宫训练大鼠7 d筛选合格大鼠后,海马直接注射不同剂量胆固醇,72 h后水迷宫检测行为学变化,并以免疫印迹和免疫组织化学方法检测大鼠海马tau蛋白磷酸化水平。结果注射胆固醇后72 h,中高剂量组大鼠水迷宫潜伏期明显延长(P<0.01),tau蛋白PHF-1位点磷酸化水平明显增高(P<0.01),tau-1明显降低(P<0.01),总tau蛋白(R134d)无明显变化。结论海马胆固醇水平升高可导致tau蛋白磷酸化程度增加,可能参与AD的形成。     

Leber's Hereditary Optic Neuropathy Arising From the Synergy Between ND1 3635G>A Mutation and Mitochondrial YARS2 Mutations

PurposeTo investigate the mechanism underlying the synergic interaction between Leber''s hereditary optic neuropathy (LHON)-associated ND1 and mitochondrial tyrosyl-tRNA synthetase (YARS2) mutations.MethodsMolecular dynamics simulation and differential scanning fluorimetry were used to evaluate the structure and stability of proteins. The impact of ND1 3635G>A and YARS2 p.G191V mutations on the oxidative phosphorylation machinery was evaluated using blue native gel electrophoresis and enzymatic activities assays. Assessment of reactive oxygen species (ROS) production in cell lines was performed by flow cytometry with MitoSOX Red reagent. Analysis of effect of mutations on autophagy was undertaken via flow cytometry for autophagic flux.ResultsMembers of one Chinese family bearing both the YARS2 p.191Gly>Val and m.3635G>A mutations exhibited much higher penetrance of optic neuropathy than those pedigrees carrying only the m.3635G>A mutation. The m.3635G>A (p.Ser110Asn) mutation altered the ND1 structure and function, whereas the p.191Gly>Val mutation affected the stability of YARS2. Lymphoblastoid cell lines harboring both m.3635G>A and p.191Gly>Val mutations revealed more reductions in the levels of mitochondrion-encoding ND1 and CO2 than cells bearing only the m.3635G>A mutation. Strikingly, both m.3635G>A and p.191Gly>Val mutations exhibited decreases in the nucleus-encoding subunits of complex I and IV. These deficiencies manifested greater defects in the stability and activities of complex I and complex IV and overproduction of ROS and promoted greater autophagy in cell lines harboring both m.3635G>A and p.191Gly>Val mutations compared with cells bearing only the m.3635G>A mutation.ConclusionsOur findings provide new insights into the pathophysiology of LHON arising from the synergy between ND1 3635G>A mutation and mitochondrial YARS2 mutations.     

Rats classified as low or high cocaine locomotor responders: A unique model involving striatal dopamine transporters that predicts cocaine addiction-like behaviors

Individual differences are a hallmark of drug addiction. Here, we describe a rat model based on differential initial responsiveness to low dose cocaine. Despite similar brain cocaine levels, individual outbred Sprague-Dawley rats exhibit markedly different magnitudes of acute cocaine-induced locomotor activity and, thereby, can be classified as low or high cocaine responders (LCRs or HCRs). LCRs and HCRs differ in drug-induced, but not novelty-associated, hyperactivity. LCRs have higher basal numbers of striatal dopamine transporters (DATs) than HCRs and exhibit marginal cocaine inhibition of in vivo DAT activity and cocaine-induced increases in extracellular DA. Importantly, lower initial cocaine response predicts greater locomotor sensitization, conditioned place preference and greater motivation to self-administer cocaine following low dose acquisition. Further, outbred Long-Evans rats classified as LCRs, versus HCRs, are more sensitive to cocaine's discriminative stimulus effects. Overall, results to date with the LCR/HCR model underscore the contribution of striatal DATs to individual differences in initial cocaine responsiveness and the value of assessing the influence of initial drug response on subsequent expression of addiction-like behaviors.     

Roles of O-GlcNAcylation on amyloid-β precursor protein processing,tau phosphorylation,and hippocampal synapses dysfunction in Alzheimer’s disease

Alzheimer disease (AD), a central nervous system degenerative disease, is characterized by abnormal deposition of amyloid-β peptide (Aβ), neurofibrillary tangles formed by hyperphosphorylated tau and synaptic loss. It is widely accepted that Aβ is the chief culprit of AD. Aβ peptide is the cleavage product of amyloid-β precursor protein (APP). Recently, more attention has been paid to O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) modification of protein. O-GlcNAcylation plays a significant role in hippocampal synaptic function. Abated O-GlcNAcylation might be a modulator in progression of AD through regulating activity of pertinent enzymes and factors. Evidence suggests that enhanced O-GlcNAcylation interacts with tau phosphorylation and prevents brain from tau and Aβ-induced impairment. Here, we review the roles of O-GlcNAcylation in APP cleavage, tau phosphorylation and hippocampal synapses function.     

Bax phosphorylation association with nucleus and oligomerization after neonatal Hypoxia–ischemia

Neonatal hypoxia–ischemia (HI) is a common occurrence in preterm and low‐birth‐weight infants, and the incidence of low‐birth‐weight and preterm births is increasing. Characterization of brain injury after HI is of critical importance in developing new treatments that more accurately target the injury. After severe HI, neuronal cells undergo necrosis and secondary apoptosis of the surrounding cells as a result of neuroinflammation. We sought to characterize the biochemical pathways associated with cell death after HI. Bax, a cell death signaling protein, is activated after HI and translocates to the nucleus, endoplasmic reticulum, and mitochondria. The translocation patterns of Bax affect the resultant cell death phenotype (necrotic or apoptotic) observed. Although Bax is known to oligomerize once it is activated, less is known about the factors that control its translocation and oligomerization. We hypothesize that Bax kinase‐specific phosphorylation determines its oligomerization and intracellular localization. Using well‐established in vivo and in vitro models of neonatal HI, we characterized Bax oligomerization and multiorganelle translocation. We found that HI‐dependent phosphorylation of Bax determines its oligomerization status and multiorganelle localization, and, ultimately, the cell death phenotype observed. Understanding the mechanisms of Bax translocation will aid in the rational design of therapeutic strategies that decrease the trauma resulting from HI‐associated inflammation. © 2013 Wiley Periodicals, Inc.     

Direct binding of GABAA receptor β2 and β3 subunits to gephyrin

GABAergic transmission is essential to brain function, and a large repertoire of GABA type A receptor (GABA_AR) subunits is at a neuron's disposition to serve this function. The glycine receptor (GlyR)‐associated protein gephyrin has been shown to be essential for the clustering of a subset of GABA_AR. Despite recent progress in the field of gephyrin‐dependent mechanisms of postsynaptic GABA_AR stabilisation, the role of gephyrin in synaptic GABA_AR localisation has remained a complex matter with many open questions. Here, we analysed comparatively the interaction of purified rat gephyrin and mouse brain gephyrin with the large cytoplasmic loops of GABA_AR α1, α2, β2 and β3 subunits. Binding affinities were determined using surface plasmon resonance spectroscopy, and showed an ~ 20‐fold lower affinity of the β2 loop to gephyrin as compared to the GlyR β loop–gephyrin interaction. We also probed in vivo binding in primary cortical neurons by the well‐established use of chimaeras of GlyR α1 that harbour respective gephyrin‐binding motifs derived from the different GABA_AR subunits. These studies identify a novel gephyrin‐binding motif in GABA_AR β2 and β3 large cytoplasmic loops.