重组人亲环素A的表达、纯化及活性测定

将RT－PCR扩增得到的亲环素A（CyPA）基因片段插入原核表达载体pET11c中,得到重组质粒pET11／CyPA,转入大肠杆菌获得高效表达。Spe－PAGE分析表明,重组CyPA表达量占菌体可溶性蛋白的40％以上。经50％硫酸铵沉淀和DEAESepharoseCL－6B柱层析可纯化重组CyPA。用糜蛋白酶偶联法测定显示重组CyPA具有肽基脯氨酸顺／反异构酶活性。     

HIV-1Gag蛋白在大肠杆菌和重组杆状病毒系统中的高效表达及通用型温控原核表达载体的构建

将中国株HIV－1B亚型的gag全基因序列,克隆到杆状病毒表达载体pfastbacI中,构建了重组质粒pfastGag,利用细菌／杆状病毒表达系统筛选重组杆状病毒,在昆虫细胞中高效表达了HIV－1Gag蛋白。通过改造原核表达载体pBV220和pET28,构建了一种新的通用型温控原核表达载体质粒pVV5,该载体携带PrPl串联温控启功子及His—Tag纯化标签,利于目的蛋白表达与纯化。将HIV－1gag基因的1148一1857编码序列,分别插入到pVV5b、pET28b的相应位点,构建了重组表达质粒pEG1b、pEG7b,二者在不同受体菌中,表达重组蛋白的量分别占全菌体蛋白总量的42％和28％。利用IMAC金属螯合层析柱,对包涵体中的重组p24蛋白进行纯化,纯度超过80％;纯化后的重组蛋白可与HIV－1型标准阳性血清发生较强的免疫学反应。     

白喉毒素无毒突变体CRM197基因的克隆与表达

目的构建白喉毒素(Diphtheria toxin)无毒突变体CRM197(Cross-reacting materials 197)的原核表达载体,并在大肠杆菌中表达重组蛋白。方法以白喉杆菌(ATCC39255)基因组DNA为模版,采用聚合酶链式反应(Polymerase chain reaction,PCR)扩增CRM197基因,插入表达载体pET11b中,构建重组原核表达质粒pET11b-CRM197。经双酶切及测序鉴定正确后,重组质粒被转化入大肠杆菌Rosetta 2(DE3)pLysS,IPTG诱导表达,表达产物经SDS-PAGE和Western blot进行鉴定。结果重组表达质粒经双酶切及测序鉴定,结果表明与预期一致;表达的重组蛋白相对分子质量约58 000,并可与鼠抗CRM197单克隆抗体特异性结合。结论已成功构建了重组原核表达载体pET11b-CRM197,重组的CRM197蛋白在大肠杆菌中得到了表达,为以该重组突变体作蛋白载体制备结合疫苗奠定了基础。     

构建羰基还原酶基因工程菌生物转化产l-麻黄碱

以筛选得到的Morganella morganii J-8细菌的基因组为模板,通过PCR扩增得到目的基因mdlh2。核苷酸序列测定结果表明,基因全长1046bp。以pET28a（＋）为表达载体,构建重组质粒pET28a（＋）-mldh2,并在E．coli BL21（DE3）中表达。利用表达产物进行生物转化,发现其具有催化底物1-苯基-2-甲氨基丙酮（简称MAK）产l-麻黄碱的活力。进一步考察了诱导时间和IPTG浓度对重组菌表达的羰基还原酶的影响,37℃下用0．5mmoL／L的IPTG诱导4h,重组羰基还原酶的酶活达到0．2U／mg蛋白,转化液中l-麻黄碱质量浓度达到45mg／L。     

人β神经生长因子基因稀有密码子及mRNA二级结构对其在大肠杆菌中表达的影响

目的:研究人β神经生长因子(β-NGF)基因中稀有密码子及其mRNA二级结构对其在大肠杆菌中表达量的影响。方法:根据对人β-ngf中稀有密码子及其mRNA二级结构的研究,同义突变人β-ngf基因,通过PCR得到人β-ngf的5’端同义突变基因rh-β-ngfp32和全同义突变基因rh-β-ngfmu,将这2个序列克隆入载体pET3a中,得到重组质粒pET3a-ngfp32和pET3a-ngfmu,分别转化大肠杆菌BL21(DE3)感受态,IPTG诱导表达,收集菌体,SDS-PAGE检测其表达量的改变。结果:构建的pET3a-ngfp32和pET3a-ngfmu表达载体酶切和测序结果正确,SDS-PAGE结果显示,与在重组菌pET3a-NGF总蛋白中的表达量相比,目的蛋白rh-β-NGF在重组菌pET3a-NGFP32和pET3a-NGFmu中的表达量均明显增高,并且在重组菌pET3a-NGFmu中的表达量高于重组菌pET3a-NGFP32。结论:目的蛋白rh-β-NGF在重组菌pET3a-NGFP32和pET3a-NGFmu中表达量的增高,说明人β-ngf基因中稀有密码子和mRNA的二级结构对其在大肠杆菌中的表达有较为明显的影响,结果为构建rh-β-NGF的大肠杆菌工程菌株奠定了基础。     

新型抗体结合蛋白CBD—SPG的设计与表达

设计并表达可用于纯化IgG的新型高栽量抗体结合蛋白CBD—SPG。利用基因重组技术将纤维素结合结构域（Cellulose Binding Domain,CBD）基因插入到表达载体pET28a—SPG中,获得重组质粒pET28a—CBD—SPG,并转化大肠杆菌曰位J（DE3）。IPTG诱导CBD—SPG融合蛋白表达,并用SDS—PAGE和Westernblot对表达产物进行鉴定。重组表达质粒pET28a—CBD-SPG经双酶切及测序验证无误;表达产物经SDS．PAGE和WesternBlot分析表明融合蛋白的表观分子量约为40kD;CBD—SPG具有良好的结合纤维素和抗体的能力,晶体纤维素Avicelphl01对CBD—SPG的载量可达11．61mg／g（w／w）。成功构建并运用原核系统表达CBD-SPG;CBD—SPG在保持良好抗体结合能力的同时,更具有了结合纤维素的能力,有望成为一种新型的亲和材料。     

热玫瑰小双孢菌来源的丙酮酸磷酸双激酶的表达及应用

以热玫瑰小双孢菌基因组DNA为模板, 通过PCR扩增得到了编码PPDK的基因, 将此基因片段插入到表达载体pET28a(+)中构建得到了重组表达质粒pET28a(+)-PPDK, 将重组表达质粒pET28a(+)-PPDK转化到大肠杆菌BL21(DE3)中, 经过IPTG诱导, 重组菌成功表达了N端带有6-His Tag的重组PPDK。经SDS-PAGE分析, 重组PPDK单体分子量为101 kD。经过镍亲和层析和超滤后, 重组PPDK蛋白基本达到电泳纯, 并被成功应用于焦测序中。     

热玫瑰小双孢菌来源的丙酮酸磷酸双激酶的表达及应用

以热玫瑰小双孢菌基因组DNA为模板, 通过PCR扩增得到了编码PPDK的基因, 将此基因片段插入到表达载体pET28a(+)中构建得到了重组表达质粒pET28a(+)-PPDK, 将重组表达质粒pET28a(+)-PPDK转化到大肠杆菌BL21(DE3)中, 经过IPTG诱导, 重组菌成功表达了N端带有6-His Tag的重组PPDK。经SDS-PAGE分析, 重组PPDK单体分子量为101 kD。经过镍亲和层析和超滤后, 重组PPDK蛋白基本达到电泳纯, 并被成功应用于焦测序中。     

人白细胞介素-11基因在家蚕培养细胞和虫体内的表达

将缺少编码信号肽序列的人白细胞介素－11（hIL-11)546核苷酸cDNA,重组于质粒pBacPAK8构建重组转移载体pBacIL-11,与经线性化修饰的家蚕核型多角体病毒（BmBacPAK)DNA共转染家蚕培养细胞株BmN,获得了插入hIL-11基因的重组病毒。Southern杂交表明重组病毒基因组中含有hIL-11基因片段,RNA斑点杂交表明hIL-11基因得到了转录。重组病毒感BmN细胞株、家蚕幼虫和蛹,在细胞培养上清、细胞抽提物、幼虫和蛹的体液样品中,SDS－PAGE电泳分析都能检测得到表达产物的特异性条带;采用IL－11依赖细胞株B9－11和MTT法测定表达产物的生物活性,表明rIL-11基因分别在培养细胞和蚕体内得到了高效表达。     

海栖热袍菌胞外α-淀粉酶在E.coli中的高效表达

为解决密码子偏好性差异造成的表达水平低下问题,采取了3种手段提高海栖热袍菌胞外α-淀粉酶在E．coli中的表达水平。用PCR方法从海栖热袍菌（Thermotoga maritima）基因组DNA中扩增出胞外α-淀粉酶A的完整基因amyA,插入表达载体pET-20（b）中构建成质粒pET—amyA;运用基因工程手段将amyA基因富含稀有密码子的信号肽进行切除,将不含信号肽的amyAⅠ基因插入pET-20（b）中构建成质粒pET—amyAⅠ;用PCR法从大肠杆菌基因组中扩增出argU基因,插入pET—amyAⅠ中构建成质粒pET—amyAⅡ。将重组质粒分别转化到E．coli JM109（DE3）,并将重组质粒pET—amyAⅠ转化E．coli BL21-Codon Plus（DE3）-RIL。通过IPTG诱导测酶活性：在E．coli JM109（DE3）中表达的重组酶（pET—amyA）、（pET—amyAⅠ）、（pET—amyAⅡ）的酶活分别是1658．0U／mL、6721．7U／mL、8904．5U／mL,在E．coil BL21-CodonPlus （DE3）-RIL中表达的重组酶（pET—amyAⅠ）的酶活是13867．7U／mL。表明通过这些手段能大幅提高T.maritima胞外α-淀粉酶在E．coli中的表达水平。     

Hypoxia followed by reoxygenation induces secretion of cyclophilin A from cultured rat cardiac myocytes

We previously reported that hypoxia followed by reoxygenation (hypoxia/reoxygenation) rapidly activated intracellular signaling such as mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated protein kinase (ERK) 1/2, p38MAPK, and stress-activated protein kinases (SAPKs). To investigate the humoral factors which mediate cardiac response to hypoxia/reoxygenation, we analyzed the conditioned media from cardiac myocytes subjected to hypoxia/reoxygenation by two-dimensional electrophoresis and mass spectrometry. We identified cyclophilin A (CyPA) as one of the proteins secreted from cardiac myocytes in response to hypoxia/reoxygenation. Hypoxia/reoxygenation induced the expression of CyPA and its cell surface receptor CD147 on cardiac myocytes in vitro. This was also confirmed by ischemia/reperfusion in vivo. Recombinant human (rh) CyPA activated ERK1/2, p38MAPK, SAPKs, and Akt in cultured cardiac myocytes. Furthermore, CyPA significantly increased Bcl-2 in cardiac myocytes. These data strongly suggested that CyPA is released from cardiac myocytes in response to hypoxia/reoxygenation and may protect cardiac myocytes from oxidative stress-induced apoptosis.     

Inhibition of HIV-1 multiplication by antisense U7 snRNAs and siRNAs targeting cyclophilin A

Human immunodeficiency virus 1 (HIV-1) multiplication depends on a cellular protein, cyclophilin A (CyPA), that gets integrated into viral particles. Because CyPA is not required for cell viability, we attempted to block its synthesis in order to inhibit HIV-1 replication. For this purpose, we used antisense U7 small nuclear RNAs (snRNAs) that disturb CyPA pre-mRNA splicing and short interfering RNAs (siRNAs) that target CyPA mRNA for degradation. With dual-specificity U7 snRNAs targeting the 3′ and 5′ splice sites of CyPA exons 3 or 4, we obtained an efficient skipping of these exons and a strong reduction of CyPA protein. Furthermore, short interfering RNAs targeting two segments of the CyPA coding region strongly reduced CyPA mRNA and protein levels. Upon lentiviral vector-mediated transduction, prolonged antisense effects were obtained for both types of antisense RNAs in the human T-cell line CEM-SS. These transduced CEM-SS cells showed a delayed, and for the siRNAs also reduced, HIV-1 multiplication. Since the two types of antisense RNAs function by different mechanisms, combining the two approaches may result in a synergistic effect.     

Cyclophilin A: a key player for human disease

Cyclophilin A (CyPA) is a ubiquitously distributed protein belonging to the immunophilin family. CyPA has peptidyl prolyl cis-trans isomerase (PPIase) activity, which regulates protein folding and trafficking. Although CyPA was initially believed to function primarily as an intracellular protein, recent studies have revealed that it can be secreted by cells in response to inflammatory stimuli. Current research in animal models and humans has provided compelling evidences supporting the critical function of CyPA in several human diseases. This review discusses recently available data about CyPA in cardiovascular diseases, viral infections, neurodegeneration, cancer, rheumatoid arthritis, sepsis, asthma, periodontitis and aging. It is believed that further elucidations of the role of CyPA will provide a better understanding of the molecular mechanisms underlying these diseases and will help develop novel pharmacological therapies.     

Evidences of monomer, dimer and trimer of recombinant human cyclophilin A

Cyclophilin A (CyPA) is a cytosolic receptor of immunosuppressive drug cyclosporin A (CsA) which possesses peptidyl-prodyl cis/trans isomerase (PPIase) activity. The recombinant human CyPA (rhCyPA) gene has been expressed in E. coli M15. Purification was performed using salting-out, as well as Sephacryl S-100 and DEAE-Sepharose CL-6B column chromatography. The molecular weight is about 18 kDa, confirmed by SDS-PAGE and mass spectrum. The results of Native-PAGE and immunoblotting showed the existence of three bands, which agreed well with the gel filtration results. The molecular mass of the three bands determined via CTAB gel electrophoresis and SDS-PAGE (rhCyPA cross-linked with glutaraldehyde) was 18 kDa, 36 kDa and 54 kDa respectively. Further more, the native rhCyPA and the cross-linked rhCyPA had the similar chromatographic behavior in gel filtration. All of the evidences above suggest that rhCyPA exists in forms of monomer, dimer and trimer. Moreover, we observed that even at low protein concentrations CyPA largely occurs as a dimer in solution, and enzyme kinetic parameters showed that activity of dimer was much higher than monomer or trimer, which probably have some biological significances.     

Identification of simian cyclophilin A as a calreticulin-binding protein in yeast two-hybrid screen and demonstration of cyclophilin A interaction with calreticulin

Cyclophilin A (CyPA) was identified as one of the calreticulin (CR)-binding proteins in a yeast two-hybrid screen utilizing simian cDNA expression-library. The simian CyPA protein had 96% identity with that of human, differing only at eight amino acid residues. We further established CyPA–CR interaction by incubation of glutathione transferase-fused CyPA (GST-CyPA) and CR proteins with CV-1 cyto-lysates, followed by CR and CyPA-specific immuno-blot analysis. The immunosuppressive drug cyclosporin A, a CyPA ligand, did not inhibit CyPA–CR interaction. Our results established a new property of CyPA binding activity to CR. Since CR is a Ca²⁺-binding protein, CR–CyPA interactions may be important in signaling pathways for induction of Ca²⁺-dependent cellular processes.     

环孢霉素A通过ROS-Cyclophilin A-ERK1/2信号途径抑制人脐静脉内皮细胞与中性粒细胞粘附

为研究环孢霉素A(cyclosporin A,CsA)对缺氧／复氧诱导人脐静脉内皮细胞(ECV-304)与中性粒细胞粘附的影响,本工作以缺氧／复氧诱导粘附为模型,采用D-N-乙酰氨基己糖苷酶比色法检测粘附率,流式细胞术检测ECV-304细胞表面粘附分子E-选择素(E-selectin)、细胞间粘附分子-1(ICAM-1)的表达,Fenton反应测定活性氧(reactive oxygen species,ROS)的含量,Westera-blot法检测ECV-304细胞亲环素A(cyclophilin A,CyPA)、磷酸化及总细胞外信号调节激酶(ERK1／2)蛋白的表达。结果发现,ECV-304细胞经缺氧／复氧处理后,ROS释放增多,E-selectin、ICAM-1的表达上调,其表面中性粒细胞的粘附增加,CsA能显著抑制缺氧／复氧的上述作用。缺氧／复氧后,CyPA蛋白表达明显上调,ERK1/2显著活化,细胞总ERK1/2蛋白表达无明显改变。CyPA抑制剂CsA以及CyPA反义寡核苷酸均明显减轻缺氧／复氧诱导的ERK1/2激活,显著减少ECV-304细胞与中性粒细胞柑附。ERK112信号通路特异性阻断剂PD98059亦显著抑制ECV-304细胞与中性粒细胞的粘附。上述结果提示,CsA抑制缺氧气／复氧诱导的ECV-304细胞与中性粒细胞粘附,并可能通过抑制ROS-Cyclophilin A-ERK112的信号转导途径实现。     

Active-site residues of cyclophilin A are crucial for its incorporation into human immunodeficiency virus type 1 virions.

Human immunodeficiency virus type 1 (HIV-1) incorporates the cellular peptidyl-prolyl cis-trans isomerase cyclophilin A (CyPA), the cytosolic receptor for the immunosuppressant cyclosporin A (CsA). CsA inhibits the incorporation of CyPA and reduces HIV-1 virion infectivity but is inactive against closely related primate lentiviruses that do not interact with CyPA. The incorporation of CyPA into HIV-1 virions is mediated by a specific interaction with a proline-containing, solvent-exposed loop in the capsid (CA) domain of the Gag polyprotein. CsA, which disrupts the interaction with CA, binds at the active site of CyPA. To test whether active-site residues are also involved in the interaction with HIV-1 CA, we used a panel of previously characterized active-site mutants of human CyPA. Expression vectors for epitope-tagged wild-type and mutant CyPA were transfected into COS-gamma cells along with HIV-1 proviral DNA, and the virions produced were analyzed for the presence of tagged proteins. Cotransfection of the wild-type expression vector led to the incorporation of readily detectable amounts of epitope-tagged CyPA into HIV-1 virions. One CyPA mutant with a substantially decreased sensitivity to CsA was incorporated with wild-type efficiency, demonstrating that the requirements for binding to CsA and to HIV-1 CA are not identical. The remaining six CyPA mutants were incorporated with markedly reduced efficiency, providing in vivo evidence that HIV-1 CA interacts with the active site of CyPA.     

Endothelial and vascular smooth muscle cell dysfunction mediated by cyclophylin A and the atheroprotective effects of melatonin

AimsThis study evaluated the role of cyclophilin A (CyPA) in early phase of atherosclerosis and also examined the atheroprotective effects of melatonin due to its antioxidant properties.Main methodsAPOE null mice at 6 and 15 weeks of age were treated with melatonin at a dose of 0.1 mg/kg/day or 10 mg/kg/day. We evaluated both histopathological alterations in endothelial and vascular smooth muscle cells by CyPA and rolling mononuclear cell expression during the early phase of atherosclerosis development.Key findingsOur study showed that CyPA expression increases and may modulate inflammatory cell adhesion and interleukin-6 expression inducing vascular smooth muscle cell migration and inflammatory cell extravasation in a time-dependent manner. Moreover, we observed an indirect atheroprotective effect of melatonin on vascular injury; it inhibited CyPA mediated inflammatory cell extravasation and oxidative stress.SignificanceThe melatonin treatment may represent a new atheroprotective approach that contributes to reducing the early phase of atherosclerosis involving the rolling of monocytes, their passage to subendothelial space and inhibition of CyPA expression.