The protective roles of phosphorylated heat shock protein 27 in human cells harboring myoclonus epilepsy with ragged-red fibers A8344G mtDNA mutation

Mitochondrial DNA (mtDNA) mutations are associated with a large number of neuromuscular diseases. Myoclonus epilepsy with ragged-red fibers (MERRF) syndrome is a mitochondrial disease inherited through the maternal lineage. The most common mutation in MERRF syndrome, the A8344G mutation of mtDNA, is associated with severe defects in mitochondrial protein synthesis, which impair the assembly and function of the respiratory chain. We have previously shown that there is a decreased level of heat shock protein 27 (HSP27) in lymphoblastoid cells derived from a MERRF patient and in cytoplasmic hybrids (cybrids) harboring the A8344G mutation of mtDNA. In the present study, we found a dramatic decrease in the level of phosphorylated HSP27 (p-HSP27) in the mutant cybrids. Even though the steady-state level of p-HSP27 was reduced in the mutant cybrids, normal phosphorylation and dephosphorylation were observed upon exposure to stress, indicating normal kinase and phosphatase activities. To explore the roles that p-HSP27 may play, transfection experiments with HSP27 mutants, in which three specific serines were replaced with alanine or aspartic acid, showed that the phosphomimicking HSP27 desensitized mutant cybrids to apoptotic stress induced by staurosporine (STS). After heat shock stress, p-HSP27 was found to enter the nucleus immediately, and with a prolonged interval of recovery, p-HSP27 returned to the cytoplasm in wild-type cybrids but not in mutant cybrids. The translocation of p-HSP27 was correlated with cell viability, as shown by the increased number of apoptotic cells after p-HSP27 returned to the cytoplasm. In summary, our results demonstrate that p-HSP27 provides significant protection when cells are exposed to different stresses in the cell model of MERRF syndrome. Therapeutic agents targeting anomalous HSP27 phosphorylation might represent a potential treatment for mitochondrial diseases.     

过氧亚硝酸阴离子通过鸟苷酸环化酶途径抑制钠电流影响海马神经元兴奋性

过氧亚硝酸阴离子(ONOO-)是一种性质活泼的自由基,可引起强的氧化性损伤,介导了一氧化氮(NO)的大部分毒性作用.应用全细胞膜片钳技术,探讨ONOO-对脑片海马神经元电压门控钠通道电流(Ina)和神经元兴奋性的影响.结果表明,ONOO-供体SIN-1(10,500,2000 μmol/L)可浓度依赖性抑制Ina电流峰值.SIN-1与ONOO-清除剂尿酸共处理,并不影响Lna.500 μmol/L的SIN-1可使Ina的,Ⅰ-Ⅴ曲线上移,并可抑制其失活后恢复过程,但对Ina的激活和失活过程无影响.SIN-1还可抑制动作电位发放频率和幅值.脑片预处理腺苷酸环化酶(adenylate cyclase,AC)抑制剂MDL-12,330A(25 μmol/L)和NEM(50μmol/L)对SIN-1的作用无影响.然而,预处理鸟苷酸环化酶(CG)抑制剂ODQ可抑制SIN-1对Ina的作用.以上结果提示,ONOO-通过cGMP-Ina-AP信号级联系统作用于海马神经元,与PKA和蛋白巯基亚硝化途径无关,这可能是ONOO-神经毒性的机制之一.     

Genetic inactivation of the adenosine A(2A) receptor exacerbates brain damage in mice with experimental autoimmune encephalomyelitis

Studies with multiple sclerosis patients and animal models of experimental autoimmune encephalomyelitis (EAE) implicate adenosine and adenosine receptors in modulation of neuroinflammation and brain injury. Although the involvement of the A(1) receptor has been recently demonstrated, the role of the adenosine A(2A) receptor (A(2A) R) in development of EAE pathology is largely unknown. Using mice with genetic inactivation of the A(2A) receptor, we provide direct evidence that loss of the A(2A) R exacerbates EAE pathology in mice. Compared with wild-type mice, A(2A) R knockout mice injected with myelin oligodendroglia glycoprotein peptide had a higher incidence of EAE and exhibited higher neurological deficit scores and greater decrease in body weight. A(2A) R knockout mice displayed increased inflammatory cell infiltration and enhanced microglial cell activation in cortex, brainstem, and spinal cord. In addition, demyelination and axonal damage in brainstem were exacerbated, levels of Th1 cytokines increased, and Th2 cytokines decreased. Collectively, these findings suggest that extracellular adenosine acting at A(2A) Rs triggers an important neuroprotective mechanism. Thus, the A(2A) receptor is a potential target for therapeutic approaches to multiple sclerosis.     

碳酸锂通过蛋白激酶C/丝裂原活化蛋白激酶信号调节海马神经元延迟整流钾通道

碳酸锂可以用于治疗创伤和神经退行性疾病导致的脑部损伤.研究表明其保护效应与蛋白激酶C(PKC)和胞外信号调节激酶(ERK)有关.研究表明PKC激动剂PDBu可以抑制延迟整流钾通道(IK)电流并使其激活电压曲线向超极化方向移动.碳酸锂(50 μmol/L)可以抑制PDBu的反应.进一步的研究表明,预先加入MEK/ERK抑制剂U0126(20 μmol/L),碳酸锂不能逆转PDBu对,IK的作用.因此,PKC和丝裂原活化蛋白激酶(MAPK)/ERK级联反应通路可能在钾离子通道的磷酸化调节中起作用.另外,AC-cAMP和GC-cGMP的交互作用也可能参与碳酸锂对PKC激活作用的调节,成为其神经保护作用的机制之一.     

被子植物核型胚乳的细胞化

文章介绍被子植物胚乳多核体的产生及其意义、初始垂周壁和初始平周壁的产生以及微管在初始垂周壁和初始平周壁产生中的作用、胚乳发育及胚乳核细胞化的分子机制以及胚乳细胞壁的物质来源和组成的研究进展。     

拟南芥钙调素结合蛋白AtIQD26的分离鉴定

钙调素结合蛋白的研究有助于探明钙调素介导的信号转导途径.以拟南芥钙调素亚型2(ACaM2)为钓饵,重组共转化法构建并筛选了酵母双杂交文库.复筛后得到一个阳性克隆.序列测定及分析表明,分离的阳性克隆中包含一个编码钙调素结合蛋白AtIQD26的cDNA片段.凝胶覆盖实验进一步表明,AtIQD26在1 mmol/L Ca2 或1 mmol/L EGTA条件下都能与钙调素结合,说明其存在不依赖于Ca2 的CaM结合特性.GUS染色分析表明,AtIQD26具有普遍的组织表达特性,尤其是在新生的组织中表达量较大;融合荧光蛋白定位显示,AtIQD26在细胞核与质膜附近有分布.AtIQD26与钙调素空间分布的相似性,预示着它们在植物生长发育过程中可能共同发挥作用.     

小黑杨快繁与再生体系的优化

利用已获得小黑杨无菌苗叶片,研究不同培养基和植物激素对不定芽诱导、丛生苗抽茎及幼苗生根的影响。结果表明：培养基和激素对小黑杨叶片不定芽的诱导及幼苗生根有一定影响。小黑杨叶片不定芽诱导的最佳培养基：MS+6 BA 0.5 mg·L^-1+NAA 0.05 mg·L^-1,诱导率为100%。丛生苗诱导的最佳培养基：MS+6-BA 0.2 mg·L^-1+NAA 0.05 mg·L^-1。幼苗生根的最佳培养基有两种：MS+NAA 0.25 mg·L^-1或MH+IBA 0.2 mg·L^-1,生根率大于99%。     

刺五加果肉化学成分的研究

应用多种色谱技术进行分离纯化,从刺五加果肉水提取物中分离得到10个化合物,经理化性质和波谱分析鉴定其结构分别为左旋芝麻脂素(1)、紫丁香树脂酚(2)、6,7-二甲氧基香豆素(3)、7-羟基-6-甲氧基香豆素(4)、儿茶酚(5)、芦丁(6)、12-羟基硬脂酸(7)、豆甾醇(8)、β-谷甾醇(9)和蔗糖(10)。化合物3、4、5、7和8为首次从该植物中分得,其中化合物7为新的天然产物。