重组人前列腺特异性抗原的原核表达、纯化与鉴定

目的：用分子克隆技术体外制备人前列腺特异性抗原（PSA）重组蛋白，并对其活性进行鉴定。方法：用分子克隆技术从前列腺癌cDNA文库中扩增PSAcDNA，再将cDNA和准备插入的质粒载体PET-12α分别用限制性内切酶NdeⅠ和BamHⅠ消化，然后用T4连接酶将两者连接，序列正确的阳性克隆转染B121（DE3）大肠埃希菌，诱导表达重组人PSA蛋白，从细菌包涵体中纯化PSA蛋白，再用小剂量胰岛素激活PSA活性，观察活化的PSA是否分解其变色底物S-2586和天然底物精囊蛋白Semenogelin（Sg）。结果：利用原核表达技术得到了重组人PSA，在胰岛素作用下PSA被激活，活性PSA水解其天然底物Sg和变色底物S-2586。结论：用基因克隆方法体外获得的重组人PSA蛋白可表现与天然PSA同样的丝氨酸蛋白酶活性和功能。     

附睾蛋白酶抑制剂对前列腺特异性抗原活性的抑制作用

目的 观察附睾蛋白酶抑制剂(Eppin)是否抑制前列腺特异性抗原(PSA)酶活性.方法 利用分子克隆技术体外构建、表达、纯化重组Eppin和PSA.利用PSA水解变色底物S-2586的颜色变化,于分光光度计下测定其吸光度值,代表PSA酶反应速度,反应体系是在缓冲液0.1 mol/LTris-HCl,pH8.3,1.0 mol/L NaCl中进行,观察不同浓度Eppin的加入对PSA酶反应速度的影响.结果通过体外重组技术获得较高纯度和生理活性的Eppin和PSA,通过PSA水解变色底物S-2586的检测,重组PSA具有酶活性,0.3 μmol/L PSA与底物S-2586反应的饱和曲线分析显示Km(反应速度为最大反应速度一半时的底物浓度)值是0.5 μmol,底物饱和浓度0.2 mmol/L,分别加入4中不同浓度的重组Eppin 0、0.56、1.16、2.32 μmol/L,随着Eppin浓度的增加,PSA水解其变色底物S-2586速度明显减慢,PSA活性越来越受到抑制.结论 附睾蛋白酶抑制剂(Eppin)是前列腺特异性抗原(PSA)一种新的特异性抑制剂.

Abstract：

Objective To investigate the inhibitory effects of the epididymal protease inhibitor (Eppin) on the activity of prostate specific antigen (PSA).Methods Recombinant Eppin and recombinant PSA were produced by molecular cloning technique in vitro.The enzymatical analysis of Eppin inhibiting PSA was done in the reaction buffer 0.1 mol/L Tris-HC1,pH 8.3,1.0 mol/L NaCl.The hydrolysis of velocity of PSA to the chromogenic substrate S-2586 was detected by spectrometer.Results Recombinant Eppin and PSA with high purity were produced by molecular cloning technique.The recombinant PSA had the enzymatical activity by hydrolyzing its substrate S-2586.0.3μmol/L PSA and the substate S-2586 reaction to the saturation curve analysis showed that Km( response rate of half the maximum reaction rate when the substrate concentration) value was 0.5μmol,and substrate saturated concentration was 0.2 mmol/L.With the increases of Eppin (0,0.56,1.16,2.32μmol/L),the hydrolysis velocity of PSA to S-2586 was slowed down.Conclusion Eppin,as a new inhibitor,specifically inhibits the activity of PSA.     

精囊蛋白Semenogelin抑制精子活动的活性片段分析

目的:制备重组Sem enogelin(Sg)及其不同的氨基酸片段,研究其对精子活动的影响。方法:设计特异性的引物,用分子克隆技术从精囊cDNA文库中扩增精囊蛋白Sg及其N端和C端片段的DNA,再将DNA插入质粒载体PET100,筛选序列正确的阳性克隆,转染BL21(DE3)大肠埃希菌,诱导表达重组人类Sg蛋白及其N端和C端片段,用50%N i-NTA纯化重组蛋白,用上游法筛选出的正常生育男性活动精子行抑制分析,研究重组Sg及其两片段在4种不同浓度(0、1、5、10)ng/μl下对精子活动的影响。结果:重组Sg及其N端片段在5、10 ng/μl浓度下明显抑制精子的运动(P<0.001),C端片段对精子运动无抑制作用(P>0.05)。结论:Sg分子中明显抑制精子运动的活性片段在氨基端,精液液化过程中,必须清除这端抑制片段,精子才能前向运动。     

重组人类精囊蛋白的制备及功能研究

目的 制备重组精囊蛋白(semenogelin,Sg),研究其对精子活动的影响.方法设计特异性的引物,用分子克隆技术从精囊cDNA文库中扩增精囊蛋白Sg,再将DNA插入质粒载体PET100,筛选序列正确的阳性克隆,转染BL21(DE3)大肠埃希菌,诱导表达重组人类Sg蛋白,用500g/L Ni-NTA纯化重组蛋白,用正常人的通过上游法筛选出的活动精子行抑制分析,研究重组Sg在4种不同浓度0,1 ng/μL、5 ng/μL、10 ng/μL下对精子活动的影响.结果 重组Sg在5 ng//μL、10 ng/μL浓度下明显抑制精子的运动(P<0.001).结论 sg分子明显抑制精子运动,精液液化过程中,必须清除Sg中具有抑制功能的片段,精子才能前向运动.     

人精子膜表面电压依赖性阴离子通道的初步研究

目的:研究人类精子膜表面是否存在电压依赖性阴离子通道(VDAC),并研究其生物学特性。方法:设计VDAC的特异性引物,从睾丸cDNA文库中用PCR技术扩增该通道的基因产物,用分子克隆技术体外表达重组VDAC的蛋白质。从精子表面用1%TritonX-100提取及氯仿/甲醇分离疏水性的膜表面蛋白,用免疫印迹法检测精子表面是否存在天然VDAC蛋白质。结果:人类睾丸cDNA文库含有VDAC的基因表达,人类精子膜表面发现靠N端α螺旋连接在精子膜上的VDAC蛋白质。结论:人类精子膜表面镶嵌VDAC蛋白质,该通道是以α螺旋连接在精子膜上,调控精子膜内外离子的转运和信号的转导,对精子的运动和功能至关重要。     

人血管内皮细胞生长因子cDNA克隆和在大肠杆菌的高效表达

目的 在大肠杆菌高效表达人血管内皮生长因子蛋白质。方法 用PCR从人胎儿脑cDNA文库扩增血管内皮细胞生长因子（VEGF）cDNA,得到517bp的DNA片段。扩增片段重组到M13mP18中,经测序证实为VEGF165cDNA。将该片段重组到PRL621温控表达质粒中,在大肠杆菌表达20kd的重组蛋白。结果 该表达产物占菌体总蛋白的35%,其N-端15个氨基酸序列与天然VEGF165蛋白相应序列一致。结论 工程菌TG1/PRL621/VEGF高效表达人VEGF165蛋白质。     

METH1在酵母双杂交系统中的表达及对报告基因激活作用的检测

目的通过观察血管生成抑制因子METH1的cDNA片段在酵母双杂交中的表达及检测其对报告基因有无激活作用,为进一步明确METH1抑制增生性瘢痕的分子机制奠定基础。方法采用酵母双杂交Gal4系统3,经PCR扩增子METH1的cDNA片段,分别克隆入pUC19质粒,经测序正确后,再分别亚克隆入酵母双杂交诱饵载体pGBKT7中。将重组质粒导入酵母菌AH109,检测其表达产物在酵母细胞中对报告基因的激活作用。结果成功获得METH1的cDNA片段,该片段所表达的蛋白对酵母菌AH109无毒性,且对报告基因无激活作用。结论血管生成抑制因子METH1蛋白活性区在酵母双杂交系统中的表达产物,可作为诱饵蛋白进行相互作用蛋白的筛选研究。     

METH1在酵母双杂交系统中的表达及对报告基因激活作用的检测

目的通过观察血管生成抑制因子METH1的cDNA片段在酵母双杂交中的表达及检测其对报告基因有无激活作用，为进一步明确METHI抑制增生性瘢痕的分子机制奠定基础。方法采用酵母双杂交Ga14系统3，经PCR扩增子METH1的cDNA片段，分别克隆入pUC19质粒，经测序正确后。再分别亚克隆入酵母双杂交诱饵载体pGBKT7中。将重组质粒导入酵母菌AH109，检测其表达产物在酵母细胞中对报告基因的激活作用。结果成功获得METH1的cDNA片段，该片段所表达的蛋白对酵母菌AH109无毒性，且对报告基因无激活作用。结论血管生成抑制因子METH1蛋白活性区在酵母双杂交系统中的表达产物。可作为诱饵蛋白进行相互作用蛋白的筛选研究。     

分泌人共刺激分子B7-2重组BCG对膀胱癌的体外作用

目的构建可分泌表达人共刺激分子B7-2的重组BCG,并观察其对膀胱癌细胞的作用。方法利用电穿孔技术将pYL-hB7-2穿梭质粒转导入野生型BCG中;卡那霉素抗性、PCR及测序筛选重组BCG菌株(rBCG-hB7-2);SDS-PAGE和ELISA检测重组BCG的表达产物B7-2分子,并测定rBCG-hB7-2对淋巴细胞的增殖作用及对膀胱癌细胞的杀伤作用。结果获得的阳性菌株rB-CG-hB7-2具有卡那霉素抗性,其PCR产物测序后与已发表的人B7-2基因cDNA序列一致。通过SDS-PAGE可见29200的目的蛋白条带含量增加,ELISA法检测出培养上清液及菌体内均有B7-2分子表达,上清液中含量为3.8U/ml,菌体内为10.5U/ml。体外实验中,重组BCG较野生型BCG刺激淋巴细胞增殖数量增加34.8%,重组BCG所激活淋巴细胞对膀胱癌细胞的杀伤能力是野生型的2.14倍。结论成功构建了可分泌具有共刺激活性B7-2分子的基因重组BCG菌株,为该菌株进一步临床应用提供了实验依据。     

RNA干扰抑制yrdC蛋白表达对人胃癌细胞株BGC-823体外增殖能力的影响

目的:构建针对人yrdC基因siRNA的重组腺病毒Ad-shyrdC并观察其转染人胃癌细胞株BGC-823后对细胞体外增殖能力的影响。方法:筛选高效抑制yrdC蛋白表达的RNAi位点,并构建表达siRNA的重组腺病毒,转染人胃癌细胞株BGC-823后以Western印迹法鉴定细胞yrdC蛋白表达的变化;同时通过MTT法、流式细胞术分别测定BGC-823细胞增殖活性和增殖指数的变化。结果:成功构建了抑制人yrdC基因siRNA的重组腺病毒Ad-shyrdC;转染BGC-823细胞后可明显抑制yrdC蛋白表达,并使所测定的细胞MTT值和细胞增殖指数提示BGC-823细胞增殖活性下降(P<0.05)。结论:腺病毒介导的RNAi能有效地抑制BGC-823细胞中yrdC蛋白表达,并降低其增殖活性。     

Molecular mechanism of epididymal protease inhibitor modulating the liquefaction of human semen

Aim： To study the molecular mechanism of epididymal protease inhibitor （Eppin） modulating the process of prostate specific antigen （PSA） digesting semenogelin （Sg）. Methods： Human Sg cDNA （nucleotides 82-849） and Eppin cDNA （nucleotides 70-423） were generated by polymerase chain reaction （PCR） and cloned into pET-100D/TOPO. Recombinant Eppin and Sg （rEppin and rSg） were produced by BL21 （DE3）. The association of Eppin with Sg was studied by far-western immunoblot and radioautography. In vitro the digestion of rSg by PSA in the presence or absence of rEppin was studied. The effect of anti-Q20E （N-terminal） and C-terminal of Eppin on Eppin-Sg binding was monitored. Results： Eppin binds Sg on the surface of human spermatozoa with the C-terminal of Eppin （amino acids 75-133）. rSg was digested with PSA and many low molecular weight fragments were produced. When rEppin is bound to rSg, then digested by PSA, incomplete digestion and a 15-kDa fragment results. Antibody binding to the N-terminal of rEppin did not affect rSg digestion. Addition of antibodies to the C-terminal of rEppin inhibited the modulating effect of rEppin. Conclusion： Eppin protects a 15-kDa fragment of rSg from hydrolysis by PSA.     

Enzymatic action of prostate-specific antigen (PSA or hK3): substrate specificity and regulation by Zn(2+), a tight-binding inhibitor

BACKGROUND: In semen, prostate-specific antigen (PSA or hK3) digests the gel proteins semenogelin I and II, resulting in liquefaction and the release of motile spermatozoa. We characterized the substrate specificity and zinc-mediated inhibition of PSA. METHODS: The proteolysis of human semenogelin I (SgI) and II (SgII) by PSA was characterized by purification of generated SgI and SgII fragments, N-terminal sequencing, and mass spectrometry. Zn(2+)-inhibition of PSA was studied using a chromogenic substrate. RESULTS: Eighteen cleavage sites in SgI and 16 in SgII were identified. Cleavages were identified mainly as the C-terminal of certain tyrosine and glutamine residues, but also the C-terminal of histidine, aspartic acid, leucine, serine, and asparagine residues. No cleavages were identified at any arginine, lysine, phenylalanine, tryptophan, or methionine residues, indicating that the substrate specificity of PSA is distinct from that of trypsin, chymotrypsin, tissue kallkrein (hK1), and kallikrein 2 (hK2). Zn(2+) ions have a dramatic effect on PSA activity; the data indicate that Zn(2+) is a tight-binding inhibitor of PSA activity. CONCLUSIONS: The data will enable the optimized design of PSA activity assays, which may prove instrumental to uncovering the role of PSA in cancer and reproduction. The inhibition data indicate that Zn(2+) could regulate PSA activity, which may prove important in the development of efficient inhibitors of PSA activity.     

Prostate-specific antigen (PSA) protein does not affect growth of prostate cancer cells in vitro or prostate cancer xenografts in vivo

BACKGROUND: Prostate-specific antigen (PSA) is produced in high amounts by normal and malignant prostate cancer cells. PSA is a serine protease with substrates that include semenogelin I and II, insulin-like growth factor binding protein 3, fibronectin, and laminin. PSA, via its enzymatic activity, may play a role in growth, invasion, and metastasis of prostate cancer cells. Recent data also suggest that the PSA protein itself, independent of enzymatic activity, may also function as an endothelial cell-specific inhibitor of angiogenesis. METHODS: Human (PC3, DU145) and rat (AT2, AT6) prostate cancer cell lines were transfected with the full PSA gene encoding preproPSA protein. PSA-producing clones of each cell line were selected and the amount of enzymatically active PSA produced by each cell line determined using a PSA-specific fluorescent peptide substrate. In vitro and in vivo growth characteristics of PSA-producing transfectants were compared to neomycin controls and wild type cells. RESULTS: All selected clones produced and secreted PSA (5-120 ng/ml/10(5) cells). None of the PSA-transfected cell lines produced detectable amounts of enzymatically active PSA. Production of enzymatically inactive PSA by prostate cancer cell lines did not alter growth kinetics in vitro. PSA-producing xenograft doubling times in vivo were similar to neomycin controls and wild type. CONCLUSION: Although recent reports suggest the PSA protein itself may be antiangiogenic, our results demonstrate that production of PSA protein by prostate cancer cells does not significantly alter growth in vitro or in vivo.     

Epididymal protein targets: a brief history of the development of epididymal protease inhibitor as a contraceptive

The Laboratories for Reproductive Biology at the University of North Carolina at Chapel Hill began collaboration with Human Genome Sciences (Rockville, Maryland) to sequence a human epididymal library and identify epididymal-specific genes. Among the first clones obtained from Human Genome Sciences was a clone for EPPIN (official symbol, SPINLW1). Our laboratory has described EPPIN (epididymal protease inhibitor) as a novel gene on human chromosome 20q12-13.2 that encodes a cysteine-rich protein containing both Kunitz-type and WAP-type 4-disulfide core consensus sequences that characterize it as a protease inhibitor. EPPIN expresses 3 mRNA splice variants that encode 2 protein isoforms found in the testis and epididymis. Of the 2 isoforms, 1 is secreted and 1 lacks a secretory signal piece. EPPIN is predominantly a dimer, although multiples often exist, and in its native form, EPPIN is found on the sperm surface complexed with lactotransferrin and clusterin. During ejaculation, semenogelin from the seminal vesicles is bound to the EPPIN protein complex, initiating a series of events that define EPPIN's function: modulating prostate-specific antigen (PSA) activity, providing antimicrobial protection, and binding semenogelin, thereby inhibiting sperm motility. As PSA hydrolyzes semenogelin in the ejaculate coagulum, spermatozoa gain progressive motility. Using immunization as a tool to study antigen function, we demonstrated that EPPIN is essential for fertility because immunization of male monkeys with recombinant EPPIN results in complete, but reversible, contraception. To exploit our understanding of EPPIN's function, we have developed a high-throughput screen to look for compounds that inhibit EPPIN-semenogelin interaction and mimic anti-EPPIN, inhibiting sperm motility. These compounds are now being developed into a nonhormonal male contraceptive.     

Activation of latent protease function of pro-hK2, but not pro-PSA, involves autoprocessing.

BACKGROUND: Human glandular kallikrein 2 (hK2) and prostate-specific antigen (PSA) are members of an extensive kallikrein family of proteases. Both proteases are secreted as zymogens or proenzymes containing a seven amino acid propeptide that must be proteolytically removed for enzymatic activation. The physiological proteases that activate pro-hK2 and pro-PSA are not known. METHODS: The pro-hK2 peptide sequence is Val-Pro-Leu-Ile-Gln-Ser-Arg (VPLIQSR). For PSA, the amino acid sequence of the propeptide is Ala-Pro-Leu-Ile-Leu-Ser-Arg (APLILSR). Fluorescent substrates were made by coupling these peptide sequences to 7-amino-4-methylcoumarin (AMC). The hydrolysis of the VPLIQSR-AMC and APLILSR-AMC substrates by hK2, PSA, and a panel of purified proteases was determined. RESULTS: HK2 readily cleaved the pro-hK2 peptide substrate VPLIQSR-AMC with a rate of hydrolysis that was approximately 8-fold higher than an equimolar amount of purified trypsin. HK2 also had the highest hydrolysis rate from among a group of other trypsin-like proteases. In contrast, neither hK2 nor PSA was able to appreciably cleave the pro-PSA substrate APLILSR-AMC. The pro-PSA substrate was most readily hydrolyzed by urokinase and trypsin. CONCLUSIONS: HK2 can hydrolyze the pro-hK2 substrate suggesting that maturation of pro-hK2 to enzymatically active hK2 involves autoprocessing. As expected, PSA, a chymotrypsin-like protease, was unable to hydrolyze either of the propeptide substrates. Therefore, it is unlikely that PSA can auto-process its own enzymatic function. HK2 has trypsin-like specificity but was unable to hydrolyze the pro-PSA substrate. These results raise the possibility that an additional processing protease may be required to fully process PSA to an enzymatically active form.     

成人成骨细胞体外培养

目的 改良成人成骨细胞消化培养方法,以满足在细胞学水平进行骨代谢性疾病研究的需要。方法 取无菌骨碎片,先用胰蛋白酶消化多次,以去除血的血细胞和成纤维细胞;骨片经和培养后,再次使用胰蛋白酶消化,得到大量纯净成骨细胞。细胞长至汇合后生成黑色结节。分别采用ＮＰＰ底物法,＾１２５Ｉ标记放射免疫（ＲＩＡ）法和Ⅰ、Ⅲ型胶原顺序沉淀提、ＳＤＳ－ＰＡＧＥ还原电泳法测定细胞上清中成骨细胞主要特征性分泌物;大量碱性磷     

Expression, purification, and characterization of active recombinant prostate-specific antigen in Pichia pastoris (yeast)

BACKGROUND: Prostate-specific antigen (PSA), a member of the kallikrein family of serine proteases, is a chymotrypsin-like glycoprotein produced by the prostate epithelium. Elevated serum PSA (> 4 ng/ml) is a tumor marker for prostatic cancer and benign prostatic hypertrophy; increasing serum PSA over time is indicative of metastatic disease. It has been suggested that PSA may contribute to tumor metastasis through degradation of extracellular matrix glycoproteins, as well as cleavage of IGF binding protein-3, a modulator of IGF-1. To elucidate the role of PSA in the development and progression of prostatic cancer, it is necessary to have a reliable, cost-effective source of enzymatically active protein. Previous efforts to express recombinant PSA (rPSA) produced inactive proPSA, or mixtures of active and inactive PSA requiring activation by removal of the propeptide. We describe the expression of active recombinant mature PSA in yeast. METHODS: Stable chromosomal integration of a construct consisting of the yeast alpha-factor signal sequence preceding the mature PSA sequence resulted in secretion of rPSA. The rPSA was purified from the yeast cell culture supernatant to homogeneity by strong cation-exchange chromatography, and characterized by SDS-PAGE, Western analysis, electrospray mass spectrometry, N-glycanase digestion, N-terminal amino acid sequencing, and inactivation by a PSA-specific inhibitor. RESULTS: We report the production of active, mature rPSA in Pichia pastoris. Two forms of rPSA varying slightly in glycosylation were identified. The specific activity of the rPSA was equal to that of human seminal plasma PSA (0.56 micromol/min mg) as determined using a chromogenic substrate. CONCLUSIONS: Large-scale production of active rPSA will be useful in the exploration of PSA effects on tumor cell proliferation, migration and metastasis. In addition, a large supply of enzyme should facilitate the discovery of novel inhibitors for in vitro and in vivo evaluation, and may provide a reproducible source of rPSA for use as a standard in diagnostic testing.     

Characterization of opticin digestion by proteases involved in osteoarthritis development

ObjectiveOpticin is a class III member of the small leucine-rich repeat proteoglycan (SLRP) family, produced in articular joint tissues. In normal and osteoarthritic (OA) cartilage, opticin is degraded. This study aimed to assess whether human cartilage opticin is degraded by the main proteases involved in OA pathophysiology, and to determine the protease cleavage sites of this SLRP.MethodsWe analyzed the proteolytic activity of matrix metalloproteinases (MMPs)-1, -2, -3, -7, -8 and -9, and ADAMTS-4 and -5 on proteoglycan extracts from normal and moderately fibrillated OA human cartilage, and on recombinant human opticin. Opticin degradation was analyzed by Western blotting and cleavage sites were determined by sequence analysis.ResultsAll eight proteases digested opticin from proteoglycan extracts from both normal and OA samples, as well as recombinant human opticin, MMP-2 and MMP-7 are the proteases that degrade recombinant human opticin most efficiently. The opticin cleavage site determined for these MMPs was between the glycosylation and leucine-rich repeat domains. MMP-7 had two additional digestion sites near the N-terminal end of opticin.ConclusionOpticin is a substrate for several MMPs and aggrecanases involved during OA cartilage degradation, and seems to be a preferential substrate for MMP-7. The role of opticin in cartilage degeneration could be related to decreased levels of intact opticin, followed by its proteolytic degradation, which in turn may stimulate some of the modifications observed in the OA cartilage, such as neovascularisation and changes in the extracellular matrix.