Visualizing myosin-actin interaction with a genetically-encoded fluorescent strain sensor

Many proteins have been shown to undergo conformational changes in response to externally applied force in vitro, but whether the force-induced protein conformational changes occur in vivo remains unclear. To reveal the force-induced conformational changes, or strains, within proteins in living cells, we have developed a genetically encoded fluorescent “strain sensor,” by combining the proximity imaging (PRIM) technique, which uses spectral changes of 2 GFP molecules that are in direct contact, and myosin–actin as a model system. The developed PRIM-based strain sensor module (PriSSM) consists of the tandem fusion of a normal and circularly permuted GFP. To apply strain to PriSSM, it was inserted between 2 motor domains of Dictyostelium myosin II. In the absence of strain, the 2 GFP moieties in PriSSM are in contact, whereas when the motor domains are bound to F-actin, PriSSM has a strained conformation, leading to the loss of contact and a concomitant spectral change. Using the sensor system, we found that the position of the lever arm in the rigor state was affected by mutations within the motor domain. Moreover, the sensor was used to visualize the interaction between myosin II and F-actin in Dictyostelium cells. In normal cells, myosin was largely detached from F-actin, whereas ATP depletion or hyperosmotic stress increased the fraction of myosin bound to F-actin. The PRIM-based strain sensor may provide a general approach for studying force-induced protein conformational changes in cells.     

Quality control of overexpressed membrane proteins

Overexpression of membrane proteins in Escherichia coli frequently leads to the formation of aggregates or inclusion bodies, which is undesirable for most studies. Ideally, one would like to optimize the expression conditions by monitoring simultaneously and rapidly both the amounts of properly folded and aggregated membrane protein, a requirement not met by any of the currently available methods. Here, we describe a simple gel-based approach with green fluorescent protein as folding indicator to detect well folded and aggregated proteins simultaneously. The method allows for rapid screening and, importantly, pinpointing the most likely bottlenecks in protein production.     

Heat shock proteins in the retina: Focus on HSP70 and alpha crystallins in ganglion cell survival

Heat shock proteins (HSPs) belong to a superfamily of stress proteins that are critical constituents of a complex defense mechanism that enhances cell survival under adverse environmental conditions. Cell protective roles of HSPs are related to their chaperone functions, antiapoptotic and antinecrotic effects. HSPs' anti-apoptotic and cytoprotective characteristics, their ability to protect cells from a variety of stressful stimuli, and the possibility of their pharmacological induction in cells under pathological stress make these proteins an attractive therapeutic target for various neurodegenerative diseases; these include Alzheimer's, Parkinson's, Huntington's, prion disease, and others. This review discusses the possible roles of HSPs, particularly HSP70 and small HSPs (alpha A and alpha B crystallins) in enhancing the survival of retinal ganglion cells (RGCs) in optic neuropathies such as glaucoma, which is characterized by progressive loss of vision caused by degeneration of RGCs and their axons in the optic nerve. Studies in animal models of RGC degeneration induced by ocular hypertension, optic nerve crush and axotomy show that upregulation of HSP70 expression by hyperthermia, zinc, geranyl–geranyl acetone, 17-AAG (a HSP90 inhibitor), or through transfection of retinal cells with AAV2-HSP70 effectively supports the survival of injured RGCs. RGCs survival was also stimulated by overexpression of alpha A and alpha B crystallins. These findings provide support for translating the HSP70- and alpha crystallin-based cell survival strategy into therapy to protect and rescue injured RGCs from degeneration associated with glaucomatous and other optic neuropathies.     

质粒型单纯疱疹病毒载体介导GDNF和GFP基因在体外培养的BHK细胞和大鼠脊髓、背根节神经元中的转移和表达

为了观察质粒型单纯疱疹病毒载体介导的外源性胶质细胞源性神经营养因子和绿色荧光蛋白基因在体外培养的金黄地鼠肾细胞以及脊髓神经元和背根节神经元中的转移和表达 ,本研究采用了以质粒型单纯疱疹病毒载体为基础构建的分别含有重组胶质细胞源性神经营养因子和绿色荧光蛋白基因的混合毒株 dv HSV-GDNF和 dv HSV-GFP感染体外培养的金黄地鼠肾细胞、脊髓神经元和背根节神经元。用免疫组织化学方法和荧光显微镜观测法分别检测了胶质细胞源性神经营养因子和绿色荧光蛋白基因的转移和表达。结果发现 :质粒型单纯疱疹病毒载体可以成功地将外源性胶质细胞源性神经营养因子和绿色荧光蛋白基因导入金黄地鼠的肾细胞以及脊髓神经元和背根节神经元中。提示质粒型单纯疱疹病毒载体可以作为转基因胶质细胞源性营养因子治疗脊髓损伤的转移载体 ,为脊髓损伤的基因治疗提供了实验基础。绿色荧光蛋白作为报告基因 ,也可因其适用广泛、观察简便等特性而得到更加广泛的应用。     

汉坦病毒核蛋白基因片段真核表达载体的构建及鉴定

目的 确定特定小鼠ＭＨＣ Ｉ类分子Ｈ－２ｄ限制性另工提呈的汉坦病毒核蛋白（ＮＰ）抗原表位。方法 在计算机预测的基础上,以编码ＮＰ的Ｓ基因为模板,合成了３个相互重叠的基因片段,构建了以携带ＧＦＰ报告基因的ｐＥＧＦＰ－Ｎ２为持载体的重组质粒,并进行了初步表达及鉴定。结果 目的基因片段已插入质粒载体,并在转染的真核细胞内成功表达。结论 汉坦病毒核蛋白片段能够被细胞加工提呈。     

人组织型纤溶酶原激活剂(t-PA)与绿色荧光蛋白(GFP)在转基因烟草中的融合表达

构建人组织型纤溶酶原激活剂(t-PA)与绿色荧光蛋白(GFP)融合表达的植物表达载体pCA1302NSF-tPA。将重组载体转入根瘤农杆菌GV3101中，通过叶圆盘法转化烟草。转化植株经PCR鉴定整合有t-PA基因，通过荧光显微镜可检测到绿色荧光蛋白(GFP)的表达。     

HBV启动子调控的GFP在肿瘤细胞中的表达

为进一步探讨针对晚期肺癌患者治疗的新方式 ,本文根据曾有动物实验研究报告 (即ＢＣＧ辅以ＩＬ 2吸入防治实验肺癌模型 ) ,通过采用超声雾化方式 ,在临床上试行将相关免疫制剂配合化疗药物以气溶胶微粒形式吸入肺组织用以治疗肺癌 ,先后对 10例患者进行共 16例次的治疗。初步观察该方法在控制肿瘤病灶发展、减轻病痛等方面临床意义 ,现报告如下。10例患者中 ,男 7例 ,女 3例 ;年龄 6 2～ 88岁。所有患者均以临床表现 ,影像学检查 ,部分经病理证实诊断为肺癌 ,其中 ,原发性肺癌 7例 (腺癌、鳞癌各 3例 ,1例无病理 ) ;转移性肺癌 3例。ＫＰＳ…     

Parameters affecting the efficiency of Agrobacterium tumefaciens-mediated transformation of Colletotrichum graminicola

We have developed an Agrobacterium tumefaciens-mediated transformation (ATMT) protocol for the plant pathogenic fungus Colletotrichum graminicola, the cause of anthracnose leaf blight and stalk rot of corn. The ATMT results in higher transformation efficiencies than previously available polyethylene glycol-mediated protocols, and falcate spores can be used instead of protoplasts for transformation. Various experimental parameters were tested for their effects on transformation efficiencies. The parameters with the greatest influence were the A. tumefaciens strain used and the Ti-plasmid it carried, the ratio of bacterium to fungus during cocultivation, and the length of cocultivation. Southern analysis demonstrated that most transformants (80%) contained tandem integrations of plasmid sequences, and at least 36% had integrations at multiple sites in the genome. In a majority of cases (70%), the whole Ti-plasmid, and not just the T-DNA, had integrated as a series of tandem repeats. Tandem integrations, especially of the whole plasmid, make it difficult to rescue DNA from both flanks of the integrations with standard PCR-based approaches. Thus, ATMT may be unsuitable for insertional mutagenesis of C. graminicola without further modification.