重组人睫状神经营养因子衍生物的构建、表达和活性分析

采用PCR定点突变技术对睫状神经营养因子(CNTF)基因进行改造,获得了CNTF衍生物(CNTF-D)基因序列分析证明其核苷酸序列符合设计要求,并在大肠杆菌中获得高效表达,CNTF-D表达量超过40%,复性后,经Q-Sepharose HP纯化,其纯度超过95%,体内法测定发现能明显降低实验小鼠的体重。表明CNTF-D在体内具有良好的生物学活性,为下游开发奠定了基础。     

人纤溶酶原饼环区5(hPK5)基因的分泌型表达

构建人纤溶酶原饼环区5(hPK5)基因的原核可溶性表达载体并进行表达和纯化,获取大量高纯度、具有生物活性的hPK5蛋白。以纤溶酶原cDNA为模板,PCR扩增了hPK5基因,经过适当酶切后构建表达载体pET22b(+)hPK5,转入大肠杆菌BL21(DE3)进行表达并经组氨酸亲和层析获得纯化。带有重组质粒pET22b(+)hPK5的大肠杆菌经IPTG诱导后以可溶性形式表达16kDa的蛋白,其表达量占菌体总蛋白的30%以上,纯化后目的蛋白纯度达95%以上,Western印迹表明重组蛋白具有Histag抗原活性。构建了pET22b(+)hPK5重组质粒并成功地在大肠杆菌中获得可溶性表达,为获得大量hPK5基因工程产品奠定了实验基础。     

细胞因子对GH3细胞中人生长激素基因表达的影响

为了研究细胞因子IL 11、睫状神经营养因子 (CNTF)和转化生长因子 (TGF β)对大鼠垂体GH3 细胞中人生长激素 (hGH)的基因启动子活性的影响及其与垂体特异性转录因子Pit 1蛋白的关系 ,首先建立含hGH基因启动子 (- 4 84～ 30bp)和荧光素酶融合基因的稳定转化GH3 细胞系 ,然后用细胞因子刺激 ,检测细胞培养液和细胞裂解液中GH的含量 ,反映它们对GH分泌和合成的影响 ;检测GH3 细胞内荧光素酶的变化 ,说明细胞因子对hGH基因启动子活性的作用。将Pit 1蛋白表达质粒 (pcDNA pit 1 cDNA)单独转染或与Pit 1反义寡核苷酸 (Pit 1OND)共转染于稳定转化的GH3 细胞中 ,观察加入细胞因子后荧光素酶的变化 ,探讨细胞因子的作用与Pit 1蛋白的关系。结果表明 ,IL 11(2 0nmol/L)、CNTF(10nmol/L)能刺激大鼠垂体GH3 细胞中GH的分泌和合成 ,增强GH3 细胞中荧光素酶的表达 ,分别增加到对照组的 12 6 %、136 %。TGF β(5nmol/L)能减少GH的分泌和合成 ,抑制荧光素酶的表达到对照组的 77%。Pit 1蛋白过表达和表达被抑制对细胞因子的调节作用没有影响。这说明IL 11、CNTF和TGF β可通过调节大鼠垂体GH3 细胞中hGH基因启动子活性影响GH的合成 ,Pit 1蛋白可能不参与这些调节作用。     

重组人睫状神经营养因子突变体的构建、表达及生物活性分析

目的:通过对原始CNTF的突变改造,降低表达蛋白的免疫原性,同时增加其稳定性,以期能用于临床治疗肥胖症。方法:以原始CNTF为模板,去掉N端的12个氨基酸、C端的14个氨基酸,并将C端末2个氨基酸点突变为极性较强的赖氨酸,在大肠杆菌中表达,获得CNTF-T突变体。结果:基因序列分析与原设计吻合,目的蛋白表达量占全菌体的35%左右,表达蛋白以包涵体形式存在,经变性、复性、DEAE-FF纯化,纯度可达95%以上,小鼠体内生物活性测定,能明显抑制小鼠体重增长,且CNTF-T的生物活性比原始序列CNTF的活性高。结论:突变的CNTF-T有望成为新一代的生物减肥制剂应用于临床。     

转铁蛋白-PEG-睫状神经营养因子的制备及其生物活性评价

为了实现在体内更持久的药效作用,根据睫状神经营养因子CNTF第17位为游离半胱氨酸残基,而转铁蛋白Tf无游离半胱氨酸的特点,采用N-羟基琥珀酰亚胺-聚乙二醇5K-马来酰亚胺(NHS-PEG5k-MAL)作为偶联剂,实现了两者定点偶联,然后结合蛋白自身特性制定纯化方法,制备获得纯度高于90%的转铁蛋白-聚乙二醇5k-睫状神经营养因子(Tf-PEG5k-CNTF)耦合物。高效凝胶色谱和动态光散射分析显示耦合物的表观分子体积大于两蛋白之和。细胞试验结果显示耦合物的活性下降至原蛋白的65.8%。大鼠药代动力学试验显示Tf-PEG5k-CNTF耦合物在体内的代谢半衰期延长至8.2小时,与CNTF原蛋白相比提高了约17倍。小鼠动物试验显示在每周2次的给药频率,每次1.0 mg/kg的剂量下,Tf-PEG5k-CNTF能更为显著地影响小鼠对食物摄入量和减轻体重。因此,转铁蛋白偶联技术可用于脑部靶向蛋白药物的长效递送。     

耐甲氧西林金黄色葡萄球菌PBP2a转肽酶区的克隆表达及纯化鉴定

目的:对编码耐甲氧西林金黄色葡萄球菌(MRSA)青霉素结合蛋白2a(PBP2a)转肽酶区的mecA基因片段进行克隆、表达、纯化及鉴定。方法:根据基因文库登录的mecA基因的编码序列,设计合成了一对寡核苷酸引物,应用PCR技术从MRSA基因组DNA中扩增获得编码PBP2a转肽酶区的DNA片段,将此目的基因片段克隆至pET-His载体,经酶切鉴定、测序正确后,转化E.coliBL21(DE3)plysS;用IPTG进行诱导表达后,利用Ni2 亲和层析技术从表达蛋白中纯化目的蛋白;对表达的蛋白以MRSA胶乳凝集试剂盒进行鉴定。结果:成功构建了PBP2a转肽酶区原核表达载体,并获得了高效表达,制备了高纯度的目的蛋白。结论:获得了高纯度的PBP2a转肽酶区蛋白,为其进一步研究奠定了基础。     

肿瘤坏死因子相关的凋亡诱导配体(TRAIL)cDNA的克隆、表达和活性测定

肿瘤坏死因子相关的凋亡诱导配体 (TRAIL)能选择性诱导肿瘤细胞凋亡 .为利用基因工程技术获得重组TRAIL蛋白可溶性片段 (sTRAIL) ,设计 1对引物 .利用PCR技术特异性扩增出sTRAIL的cDNA ,克隆于质粒pGEM 3Zf( )的EcoRⅠ和PstⅠ位点 .经测序证明序列正确后克隆于表达质粒pBV2 2 0的EcoRⅠ和PstⅠ位点 ,转化大肠杆菌DH5α .转化菌株经温度诱导 ,SDS PAGE检测和Western印迹鉴定 ,获得重组sTRAIL的高水平非融合表达菌株 .表达量占菌体总蛋白的 2 0 % .对其表达产物进行了初步纯化 ,SDS PAGE结果显示纯度可达 90 %以上 .用L92 9细胞测定其生物学活性表明 ,重组蛋白在体外能明显诱导肿瘤细胞凋亡     

分泌睫状神经营养因子腺病毒载体的构建及小量复制病毒增强其分泌表 达的研究

目的:探讨复制型腺病毒能否增强增殖缺陷型腺病毒Ad5-hCNTF所携带外源基因的表达分泌。方法:亚克隆获得分泌型睫状神经营养因子的基因(ciliary neurotrophic factor),然后将此基因插入到穿梭质粒pshuttle。pshuttle-hCNTF经pme1酶切后,CIAP去磷酸化,利用Ad-EASY腺病毒制备系统,将其与腺病毒骨架质粒pAdEasy-1共同转化大肠杆菌BJ5183,通过同源重组,筛选出含目的基因的重组型腺病毒质粒的菌株,获得大量该质粒后转染病毒包装细胞AD-293,成功包装出一种血清5型增殖缺陷型腺病毒Ad5-hCNTF。结果:经PCR鉴定该病毒含有该基因片断,Western blotting证实该病毒感染细胞后能表达CNTF蛋白。采用ELISA法检测培养液证实感染细胞能高水平地分泌CNTF。结论:体外实验表明在不同滴度的复制型腺病毒Ad5-E1+E3+的带动下,该病毒感染细胞后分泌表达目的蛋白的水平显著提高,为今后应用Ad作为基因治疗的载体提供实验证据。     

结核分枝杆菌肝素结合血凝素蛋白的表达、纯化及免疫学特性的初步研究

目的:克隆肝素结合血凝素(HBHA)基因,并在大肠杆菌中进行表达和纯化,利用获得的蛋白进行免疫学特性的初步研究.方法:用PCR方法从结核分枝杆菌H37Rv基因组扩增出HBHA基因片段,克隆至pMDI8-T载体中,序列测定正确后,将其亚克隆到表达载体pQE80L并在大肠杆菌DH5α中表达,表达蛋白经SDS-PAG及Western-blot分析后,亲和层析法纯化蛋白.获得的蛋白免疫BALB/c小鼠,测定血清抗体水平及IgG2a/IgG1比例.结果:克隆了HBHA基因,并成功表达该蛋白,SDS-PAGE及Western-blot分析表明表达产物正确.通过亲和层析法得到28kD纯化蛋白,与文献报道相符,诱导小鼠可使CD4+和CD8+细胞数明显增加.结论:成功获得了纯化的HBHA蛋白,明确了HBHA蛋白的免疫学特性,为进一步研究HBHA蛋白的致病机理及新型疫苗的开发提供了实验依据.     

原核生物核糖核酸酶HII基因的克隆及在大肠杆菌中的高效表达

核糖核酸酶HII (RNaseHII)能有效降解RNA和DNA杂交链中的RNA链。为进一步研究其功能 ,利用大肠杆菌XL1blue为模板 ,相应的寡聚脱氧核苷酸为引物 ,PCR扩增大肠杆菌RNaseHII(rnh 2 )基因 ,并将目的基因连接到克隆载体 pUC18上 ,经测序确认无误 ,分别亚克隆到能够进行IPTG诱导的表达载体pTrcHisC和进行温度诱导的表达载体pBV2 2 0上。重组质粒转化到大肠杆菌DH5α细胞中获得高效表达。在载体pTrcHisC和 pBV2 2 0中目的蛋白RNaseHII的表达量均超过菌体总蛋白的 2 0 % ,且表达产物以稳定的包涵体形式存在。此项工作为以后目的蛋白的纯化提供了有利条件 ,并为研究其结构和功能奠定了基础。     

Expression and histochemical localization of ciliary neurotrophic factor in cultured adult rat dorsal root ganglion neurons

Ciliary neurotrophic factor (CNTF) is abundantly expressed in Schwann cells in adult mammalian peripheral nerves, but not in neurons. After peripheral nerve injury, CNTF released from disrupted Schwann cells is likely to promote neuronal survival and axonal regeneration. In the present study, we examined the expression and histochemical localization of CNTF in adult rat DRG in vivo and in vitro. In contrast to the restricted expression in Schwann cells in vivo, we observed abundant CNTF mRNA and protein expression in DRG neurons after 3 h, 2, 7, and 15 days in dissociated cell culture. At later stages (7 and 15 days) of culture, CNTF immunoreactivity was detected in both neuronal cell bodies and regenerating neurites. These results suggest that CNTF is synthesized and transported to neurites in cultured DRG neurons. Since we failed to observe CNTF immunoreactivity in DRG neurons in explant culture, disruption of cell–cell interactions, rather than the culture itself, may be an inducible factor for localization of CNTF in the neurons.     

Ciliary neurotrophic factor fused to a protein transduction domain retains full neuroprotective activity in the absence of cytokine-like side effects

Ciliary neurotrophic factor (CNTF) is a multifunctional cytokine that can regulate the survival and differentiation of many types of developing and adult neurons. CNTF prevents the degeneration of motor neurons after axotomy and in mouse mutant progressive motor neuronopathy, which has encouraged trials of CNTF for human motor neuron disease. Given systemically, however, CNTF causes severe side effects, including cachexia and a marked immune response, which has limited its clinical application. The present work describes a novel approach for administering recombinant human CNTF (rhCNTF) while conserving neurotrophic activity and avoiding deleterious side effects. rhCNTF was fused to a protein transduction domain derived from the human immunodeficiency virus-1 TAT (transactivator) protein. The resulting fusion protein (TAT-CNTF) crosses the plasma membrane within minutes and displays a nuclear localization. TAT-CNTF was equipotent to rhCNTF in supporting the survival of cultured chicken embryo dorsal root ganglion neurons. Local or subcutaneous administration of TAT-CNTF, like rhCNTF rescued motor neurons from death in neonatal rats subjected to sciatic nerve transection. In contrast to subcutaneous rhCNTF, which caused a 20–30% decrease in body weight in neonatal rats between postnatal days 2 and 7 together with a considerable fat mobilization in brown adipose tissue, TAT-CNTF lacked such side effects. Together, these results indicate that rhCNTF fused with the protein transduction domain/TAT retains neurotrophic activity in the absence of CNTFs cytokine-like side effects and may be a promising candidate for the treatment of motor neuron and other neurodegenerative diseases.     

Promotion of survival and neurite outgrowth of cultured peripheral neurons by exogenous lipids and detergents

Gangliosides, in particular the monosialoglycosphingolipids Gtet 1 (GM1), have previously been implicated in the mediation of neuronal rescue and restitutional axonal growth, both in vitro and subsequent to brain and peripheral nerve lesions. In the present study it is shown that the bis-sialosyl gangliosides Gtet2b and Gtet3b, but not the gangliosides Gtet2a and Gtet1, promote the survival of dissociated dorsal root ganglion (DRG) neurons cultured from Embryonic Day (E) 8 chicks (DRG8) almost to the same extent as nerve growth factor (NGF). Ciliary ganglion (CG) neurons from E8 chicks (CG8) and DRG10 neurons were virtually not supported suggesting considerable specificity in terms of neuronal targets and developmental stages being addressed. Moreover, a variety of other lipids including cerebroside (Cb), dipalmitoylphosphatidylcholine (DPPC) and -serine (DPPS), sulfatide (Sf), and sphingomyelin (Sm) were tested for putative survival promoting activity toward chick CG, DRG, and lumbar sympathetic ganglion (SG11) neurons. At the highest concentration employed (2.5 x 10(-5) M), Sm, DPPC, and DPPS maintained between 45 and 65% of the plateau survival with CG8 (maximally supported by ciliary neuronotrophic factor (CNTF], DRG8, and DRG10 neurons, and 30 to 40% with SG11 neurons. Cb supported CG8 neurons at about 55% of the plateau value achieved with CNTF, but had hardly any effect on the other neuron populations tested. Control experiments using highly enriched neurons and serum-free conditions assured that the effects were unlikely to be mediated by serum components or nonneuronal cells. A variety of detergents, in particular Triton X-100, also promoted the survival of CG8 and DRG10 neurons. Ganglioside Gtet1, Sm, and Triton X-100 shifted the NGF titration curve for DRG10 neurons between 6- and 15-fold in a dose-dependent manner suggesting synergisms between NGF and lipids for neuronal maintenance. These results document the neuronotrophic potency of certain gangliosides, a heterogeneous group of structurally unrelated lipids, and detergents. The mechanisms by which these agents modulate neuronal survival still await clarification.     

Prevention of apoptosis in CNTF-dependent neurons by a mutant ICE and by viral protein CrmA but not by proto-oncogene product Bcl-2

The interleukin-1beta converting enzyme (ICE) gene family, (homologues of C. elegans cell death gene product Ced-3) plays an important role in controlling programmed cell death. Nerve growth factor (NGF) promotes survival of cultured embryonic chicken dorsal root ganglion neurons. Ciliary ganglion neurons depend exclusively on ciliary neurotrophic factor (CNTF) for survival. Complete depletion of NGF or CNTF from culture medium induces apoptosis in both types of neurons. We can prevent apoptosis, due either to NGF or CNTF withdrawal and in either type of neuron, by overexpression of a mutant inactive ICE and an ICE inhibitor, the product of cowpox virus gene crmA. Bcl-2 does not prevent apoptosis in CNTF-dependent ciliary neurons or DRG neurons as it does in NGF-dependent neurons. These results suggest that neuronal cell death is mediated through a common effector mechanism involving the Ice family of genes, whereas different suppression mechanisms are engaged depending upon the specific neurotrophic factors present.     

Purification of the Chick Eye Ciliary Neuronotrophic Factor

Dissociated 8-day chick embryo ciliary ganglionic neurons will not survive for even 24 h in culture without the addition of specific supplements. One such supplement is a protein termed the ciliary neuronotrophic factor (CNTF) which is present at very high concentrations within intraocular tissues that contain the same muscle cells innervated by ciliary ganglionic neurons in vivo. We describe here the purification of chick eye CNTF by a 2 1/2-day procedure involving the processing of intraocular tissue extract sequentially through DE52 ion-exchange chromatography, membrane ultrafiltration-concentration, sucrose density gradient ultracentrifugation, and preparative sodium dodecyl sulfate-polyacrylamide gradient electrophoresis. An aqueous extract of the tissue from 300 eyes will yield about 10-20 micrograms of biologically active, electrophoretically pure CNTF with a specific activity of 7.5 X 10(6) trophic units/mg protein. Purified CNTF has an Mr of 20,400 daltons and an isoelectric point of about 5, as determined by analytical gel electrophoresis. In addition to supporting the survival of ciliary ganglion neurons, purified CNTF also supports the 24-h survival of cultured neurons from certain chick and rodent sensory and sympathetic ganglia. CNTF differs from mouse submaxillary nerve growth factor (NGF) in molecular weight, isoelectric point, inability to be inactivated by antibodies to NGF, ability to support the in vitro survival of the ciliary ganglion neurons, and inability to support that of 8-day chick embryo dorsal root ganglionic neurons. Thus, CNTF represents the first purified neuronotrophic factor which addresses parasympathetic cholinergic neurons.     

Neuroprotective properties of ciliary neurotrophic factor for cultured adult rat dorsal root ganglion neurons

We observed that recombinant ciliary neurotrophic factor (CNTF) enhanced survival and neurite outgrowth of cultured adult rat dorsal root ganglion (DRG) neurons. Among other neurotrophic factors (NGF and GDNF) and interleukin (IL)-6 cytokine members [IL-6, LIF, cardiotrophin-1, and oncostatin M (OSM)] at the same concentration (50 ng/ml), CNTF, as well as LIF and OSM, displayed high efficacy for the promotion of the number of viable neurons and neurite-bearing cells. CNTF enhanced the number of neurite-bearing cells in both small neurons (soma diameter <30 mum) and large neurons (soma diameter >/=30 mum), whereas NGF and GDNF promoted that in only small neurons. Western blot analysis revealed that CNTF induced phosphorylation of STAT3, Akt, and ERK1/2 in the neurons. Furthermore, the neurite outgrowth-promoting activity of CNTF was diminished by co-treatment with Janus kinase (JAK) 2 inhibitor, AG490; STAT3 inhibitor, STA-21; phosphatidyl inositol-3'-phosphate-kinase (PI3K) inhibitor, LY294002; and mitogen-activated protein kinase kinase (MEK) inhibitor, PD98059, in a concentration-dependent manner. Its survival-promoting activity was also affected by AG490, STA-21, and LY294002 at higher concentrations, but not by PD98059. These findings suggest the involvement of JAK2/STAT3, PI3K/Akt, and MEK/ERK signaling pathways in CNTF-induced neurite outgrowth, where the former two pathways are thought to play major roles in mediating the survival response of neurons to CNTF.     

Construction and Characterization of Ciliary Neurotrophic Factor (CNTF) Antagonists: Microenvironmental Difference in the CNTF Receptor Between Rat and Chicken Cells for Recognizing the D1 Cap Region

Abstract: Antagonistic mutants of ciliary neurotrophic factor (CNTF) were constructed and their properties characterized. K155A and K155W mutants lost cell survival promoting activity for chicken dorsal root ganglion (DRG) neurons and inhibited the activity of the wild type. However, they retained slight agonistic activity for the survival of rat DRG neurons, indicating there is a difference between chicken and rat cells for receptor recognition around the D1 cap region including K155 residue. The chicken receptor recognizes the D1 cap region more strictly than does the rat receptor. The substitution of F152, which locates at the top of the D1 cap region, was combined with the K155A mutation. A combination of the two mutations gave an antagonistic feature to not only chicken but also rat cells. Both F152S/K155A and F152D/K155A mutants lacked cell survival promoting activity and had an antagonistic effect on rat DRG neurons. The three-dimensional structure of CNTF suggests the following. F152 and K155 bind to the receptor with hydrophobic and electrostatic interactions, respectively. F152 locates close to L156 with a van der Waals contact, and K155 contacts with Q42 through a hydrogen bond. Both interactions play indispensable roles in maintaining the structure around the D1 cap region of CNTF.     

rhCNTF对鸡胚感觉与运动神经元神经营养作用的比较

在无血清培养条件下,观察了重组人睫状营养因子（ｒｈＣＮＴＦ）对鸡胚背根节感觉神经元及腹角运动神经元的营养作用。结果表明ｒｈＣＮＴＦ对这两类神经元均有明显的促存活作用,并呈一定的剂量／效应关系。ｒｈＣＮＴＦ浓度在０．５ｎｇ／ｍｌ以下时无作用,１．０－１．５ｎｇ／ｍｌ时已有促神经元存活作用,４ｎｇ／ｍｌ时作用最明显,再增加到１００ｎｇ／ｍｌ神经元存活数无进一步增加。比较培养７天时两类神经元存活数发现感觉神经元对ＣＮＴＦ缺乏的敏感性高于运动神经元,提示ＣＮＴＦ对运动神经元的促存活作用只是它多种类型神经元营养作用中较弱的一环