硫化氢对体外大鼠肝星状细胞内Ca~(2+)浓度变化及细胞增殖的影响

目的 研究硫化氢(H2S)对大鼠肝星状细胞-T6(HSC-T6)Ca2+浓度、细胞增殖的影响及其机制. 方法 活化HSC-T6用含10%小牛1血清DMEM培养液制备为1×105个肝星状细胞(HSC)悬液.钙离子荧光探针Fluo-3/AM负载细胞后,在不同刺激条件下,利用激光扫描共焦显微镜动态扫描HSC-T6细胞内Ca2+荧光强度(FI)变化,FI表示细胞内Ca2+浓度.四唑盐比色法,观察不同浓度H2S供体--NasH对HSC-T6细胞增殖的影响. 结果 低浓度H2S(100μmol/L)明显降低HSC-T6细胞内Ca2+浓度(P<0.05),而细胞增殖增加(增殖率为116%);KATP通道阻断剂--格列本脲可阻断H2S的作用.高浓度H2S(Immol/L)刺激HSC-T6细胞内Ca2+浓度增加,但细胞增殖无明显变化(P>0.05). 结论 低浓度H2S通过激活HSC-T6细胞KATP通道降低绌胞内Ca2+浓度,可能通过调节细胞氧化应激促进细胞增殖;高浓度H2S刺激HSC-T6细胞内Ca2+浓度增加.提示H2S在肝硬化门脉高压症的发生机制中具有双重作用.     

Ara h2三聚体重组蛋白的制备及其低致敏原性鉴定

目的制备花生主要过敏原Ara h 2三聚体重组蛋白并检测其过敏原性。方法利用分子生物学的方法将3分子的Ara h 2依次串联起来,并将其整合到原核表达载体pET-32a(+),再转化到感受态Origami中;然后利用IPTG诱导其表达;通过Ni2+亲和层析纯化三聚体重组蛋白;Western-blotting和ELISA检测目的蛋白的过敏原性。结果测序结果表明Trimer成功整合到pET-32a(+)上。三聚体重组蛋白纯化后经SDS-PAGE鉴定,蛋白大小与理论值相符。Western-blotting和ELISA结果表明Trimer与重组的Ara h 2(r-Ara h 2)蛋白相比,结合花生过敏病人混合血清中IgE的能力有所降低。结论成功制备花生主要过敏原Ara h 2三聚体重组蛋白,初步的体外实验表明该重组蛋白具有低致敏原的潜能。     

miR-125b对过敏原刺激后支气管上皮细胞凋亡和分泌炎症因子的作用北大核心CSCD

目的:探究miR-125b对过敏原刺激后支气管上皮细胞凋亡和分泌炎症因子的作用和机制。方法:支气管上皮细胞分为Control组、Model组(尘螨抗原提取物处理)、miR-NC组(转染mimics control,尘螨抗原提取物处理)、miR-125b组(转染miR-125b mimics,尘螨抗原提取物处理)、miR-125b+PMA组(转染miR-125b mimics,尘螨抗原提取物和NF-κB信号激活剂PMA处理)。qRT-PCR分析miR-125b表达,流式细胞术分析细胞凋亡,ELISA分析细胞培养液上清中IL-6、IL-29水平,Western blot分析Bax、Bcl-2、p65蛋白表达。结果:与Control组相比,Model组支气管上皮细胞中miR-125b水平降低,细胞凋亡率升高,细胞分泌IL-6、IL-29增多,细胞中Bax、p65蛋白表达水平升高,Bcl-2蛋白表达水平降低。与miR-NC组相比,miR-125b组支气管上皮细胞中miR-125b水平升高,细胞凋亡率降低,细胞分泌IL-6、IL-29减少,细胞中Bax、p65蛋白表达水平降低,Bcl-2蛋白表达水平升高。与miR-125b组相比,miR-125b+PMA组支气管上皮细胞凋亡率升高,细胞分泌IL-6、IL-29增多,细胞中Bax、p65蛋白表达水平升高,Bcl-2蛋白表达水平降低。结论:miR-125b抑制过敏原刺激后支气管上皮细胞凋亡和分泌炎症因子,其机制可能与抑制NF-κB信号通路有关。     

尘螨抗原对支气管上皮细胞单核细胞趋化蛋白-1表达的影响

目的探讨屋尘螨（Dermatophagoides pteronyssinus，Derp）抗原对支气管上皮细胞单核细胞趋化蛋白-1（MCP-1）表达的影响。方法使支气管上皮细胞BEAS-2B暴露于系列不同浓度（0．02、0．2．2、20μg／ml）的Derp抗原24h至96h，分别观察各时间点细胞的表现，然后用酶联免疫法（ELISA）检测其细胞上清MCP-1的浓度表达。结果正常为未加Derp抗原。表现为单层细胞完全平铺；实验各组在抗原的刺激下，表现为随着浓度和时间的增加，细胞逐渐变瘦长，细胞间距逐渐增大；在无抗原刺激因素培养条件下的对照组，MCP-1释放水平很低，而在加入Derp抗原组，引起细胞分泌MCP-1蛋白水平的显著增加，并随着时间和浓度增加，MCP-1蛋白的表达水平呈上升趋势，特别是在高浓度组，即20μg／ml抗原组，各时间点MCP-1的表达差异均有统计学意义（P〈0．01）。结论Derp抗原刺激气道上皮细胞，引起支气管上皮损伤和脱落等气道炎症反应，激发单核巨噬细胞产生大量的MCP-1，促成和加重气道炎症反应，因此认为MCP-1可能参与哮喘疾病的某些过程。     

钙离子对重组创伤弧菌溶细胞素诱导THP-1细胞损伤的影响机制

目的 研究重组创伤弧菌溶细胞素( rVvhA)诱导人单核细胞白血病细胞(THP-1)的凋亡机制及其Ca2+的变化.方法 采用CCK-8法、激光共聚焦显微镜结合Fluo 3/AM法、流式细胞术结合AnnexinV -PI标记等检测rVvhA对THP-1细胞的影响,并观察胞内Ca2+浓度变化.结 果rVvhA可诱导THP-1细胞发生凋亡并引起细胞内Ca2+浓度升高,细胞内钙离子螯合剂BAPTA-AM处理组胞内钙离子升高幅度远高于细胞外钙离子螯合剂EGTA处理组.结论 rVvhA具有诱导THP-1细胞凋亡的生物学活性,并能引起细胞内Ca2+浓度升高,升高的Ca2+主要源于胞外钙离子内流.     

利用ELISA技术检测尘螨变应原的生物活性

目的分析尘螨变应原溶液中抗原含量与ELISA结果的关系,探索利用ELISA技术分析变应原生物活性的方法.方法采用ELISA技术对变应原的生物活性进行动态分析, 利用Excel软件分析抗原浓度与变应原活性的关系.结果当抗原含量在一定范围时,抗原含量与ELISA结果成正相关,利用双对数曲线分析抗原浓度与ELISA结果的关系,既能反映变应原的相对含量和活性,又能预测不同变应原溶液中变应原组成成分的差异.结论该方法可以用来比较尘螨变应原溶液的生物活性.     

家蚕过敏原CSP5克隆表达、纯化鉴定及分析

克隆家蚕过敏原CSP5(chemosensory protein 5precursor)基因,表达、纯化该蛋白,鉴定其免疫活性,并进行生物信息学分析。人工合成家蚕化学感受蛋白5前体CSP5基因,将其连接至pMD18-T克隆载体,用异丙基-β-D-硫代半乳糖苷(IPTG)诱导表达后进行纯化,用western blotting和ELISA鉴定其免疫学特性,并采用生物信息学方法预测CSP5蛋白的理化性质、三级结构、潜在B细胞抗原表位。本研究成功克隆了纯度较高的重组CSP5蛋白,测序鉴定蛋白分子质量约为14.25kD。重组过敏原CSP5能与家蚕过敏患者血清IgE发生特异性结合。生物信息学方法推导其潜在B细胞抗原表位为17~22、35~36、51~55、70~74、106~110、112~115。获得的重组蛋白CSP5具有与天然蛋白相似的免疫学活性,为以标准化抗原作为临床特异性诊断和治疗以及由家蚕引起的过敏性疾病的进一步研究奠定了基础。     

苹果过敏原Mal d4蛋白抗原表位预测及交叉反应分析

目的:预测苹果过敏原Mal d 4蛋白B细胞和T细胞抗原表位,探讨Mal d 4蛋白与其同源蛋白之间的交叉反应性.方法:以苹果过敏原Mal d 4蛋白的氨基酸序列为基础,采用生物信息软件HNN预测二级结构;运用DNAStar和Bcepred软件预测其B细胞抗原表位,用NetMHCⅡ、NetMHCⅡpan、Syfpeithi及Propred软件综合预测T细胞抗原表位;采用Clustal X1.83、Swiss-Model软件比对同源序列和模拟空间构象.结果:该蛋白二级结构以无规则卷曲为主.B/T细胞共同抗原表位的区域为53～61、85～93.苹果Mal d 4蛋白与桃、芒果、甜樱桃、草莓中的前纤维蛋白氨基酸序列同源性达88%以上,空间构象相似.结论:苹果过敏原Mal d 4蛋白与桃、芒果、甜樱桃和草莓的前纤维蛋白之间可能存在交叉反应,其优势抗原表位区域可能为53～61、85～93,是后续过敏原改造的重点,为继续深入开展苹果过敏原基础性研究提供理论依据.     

木犀草素对肥大细胞脱颗粒影响及机制的研究

目的:探讨木犀草素(Luteolin)的抗I 型变态反应的作用机制。方法:通过建立DNP-BSA-IgE 激发致敏的大鼠RBL-2H3 细胞模型,分别采用MTT 法检测不同浓度(5、15、25 mol/ L)Luteolin 对RBL-2H3 肥大细胞活性的影响;ELISA 法检测不同浓度Luteolin 对RBL-2H3 细胞分泌 hexosa minidase( HEX)及细胞因子TNF 影响;Flou-4AM 荧光探针检测细胞内Ca2+浓度变化;Western blot 检测AKT,P-AKT 的表达。结果:成功建立致敏的细胞模型,低浓度的Luteolin 对RBL-2H3 细胞活性无明显影响;不同浓度Luteolin 刺激RBL-2H3 细胞后,对 HEX 和TNF鄄琢的释放抑制作用呈线性相关,且细胞内Ca2+ 明显减少;Western blot 结果显示随着Luteolin 浓度的增加AKT 磷酸化水平明显下降。结论:Luteolin 呈剂量依赖性抑制RBL鄄2H3 肥大细胞脱颗粒,且通过调节细胞内Ca2+浓度与AKT 活性参与其中。     

Amiloride通过抑制缺氧诱导的NHE1表达而延缓calpain介导的ABCA1降解

目的:研究缺氧对钠氢交换体1(NHE1)表达、细胞内钙离子浓度([Ca2+]i)和钙蛋白酶(calpain)活性的影响,探讨NHE1抑制剂阿米洛利(amiloride)对ABCA1降解的影响以及与calpain相关的机制。方法:RAW264.7细胞缺氧0、12、24和48 h。MTT法检测细胞活力,real-time PCR及Western blot检测NHE1的表达。流式细胞术检测[Ca2+]i,荧光素法检测细胞内calpain活性。进而,经缺氧24 h处理的细胞,cycloheximide干预条件下,NHE1抑制剂amiloride处理6 h及12 h,检测ABCA1蛋白含量。最后,给予calpain抑制剂ALLN及细胞内钙螯合剂BAPTA共孵育12 h,检测ABCA1含量及calpain活性。结果:缺氧呈时间依赖方式抑制细胞增殖。缺氧促进NHE1表达上调,增加[Ca2+]i及calpain活性。缺氧加速ABCA1蛋白降解,而amiloride减缓ABCA1蛋白降解。ALLN及BAPTA升高ABCA1蛋白含量,降低calpain活性。结论:Amiloride延缓calpain介导的ABCA1降解,提示缺氧诱导NHE1表达可能至少部分参与ABCA1蛋白降解。     

Novel monoclonal antibodies to double stranded DNA that require Ca2+ or Mg2+ for their binding.

Murine monoclonal antibody (MoAb) 2B5 (IgG2aK) was obtained by its binding on a solid phase to double-stranded (ds) DNA from one of the mutant CBA/K1(CBA/K1Jms-1prcg/1prcg) mice which were recently found, in our institute, to develop lymphadenopathy associated with the production of anti-double-stranded (ds) antibodies. MoAb 2B5 was highly specific for dsDNA, as shown by enzyme-linked immunosorbent assay (ELISA). The dsDNA binding of 2B5 was decreased dose-dependently by the chelating agent EDTA, being lost completely with 2.5-5.0 mM EDTA, whereas dsDNA on the solid phase remained intact after incubation with EDTA. Addition of Ca2+ or Mg2+ to antibody in culture supernatant that had lost dsDNA binding activity by dialysis against Ca2+ and Mg(2+)-free buffer restored its binding with dsDNA to the original level, indicating that MoAb 2B5 requires Ca2+ or Mg2+ for its binding with dsDNA. It is unknown whether MoAb 2B5 recognizes new conformational epitopes created in the presence of Ca2+ or Mg2+, but this MoAb should be useful in studies on the modes of interaction of DNA with antibodies and DNA-binding proteins.     

Are Ca2+‐binding motifs involved in the immunoglobin E‐binding of allergens? Olive pollen allergens as model of study

BACKGROUND: Several Ca2+-binding proteins, which possess EF-hand sites with a high sequence similarity, have been found to be able to induce Type-I allergy. OBJECTIVE: To study whether the common EF-hand sequential motifs can be involved in the IgE-reactivity of these proteins, thus being responsible of a degree of cross-reactivity among different Ca2+-binding proteins. METHODS: Two olive pollen allergens, Ole e 3 and Ole e 8, have been used in the study. Parvalbumin and calmodulin were included in immunological analyses. Sera from patients allergic to olive pollen, as well as Ole e 3- and Ole e 8-specific rabbit antisera were used in indirect enzyme-linked immunosorbent assay (ELISA), ELISA inhibition assays and immunoblotting. Conformational analyses (circular dichroism spectra and thermal stability) and specific immunodetection assays were performed in the presence and the absence of Ca2+. Chemical breakdown and high-performance liquid chromatography (HPLC) was used to obtain fragments from Ole e 3 containing a single EF-hand motif. RESULTS: Thirty-four (17%) and 16 (8.2%) out of 195 sera from patients allergic to olive pollen contained specific IgE against Ole e 3 and Ole e 8, respectively. The IgE-binding of 12 allergic sera diminished up to 22% for Ole e 3 and to 82% for Ole e 8, when depleted Ca2+. A pool of these sera recognized the two olive allergens and parvalbumin, but at very different extent. Inhibition of the IgE-binding was only achieved between two olive allergens. No structural relationships between Ole e 3 and Ole e 8 were established when specific polyclonal antisera against both proteins were used. CONCLUSION: EF-hand Ca2+-binding sites can not be considered as general allergenic motifs responsible for the cross-reactivity between Ca2+-binding allergens. Different families of Ca2+-binding allergens have specific epitopes that could be involved in the cross-reactivity among members of the same family.     

A calcium-binding monoclonal antibody that recognizes a non-calcium-binding epitope in the short consensus repeat units (SCRs) of complement C1r.

C1r is a Ca(2+)-binding serine protease that interacts with two other plasma proteins, C1q and C1s, to form C1, the first component of the complement cascade. A monoclonal antibody, BG6, has been produced which binds to C1r only in the presence of Ca2+, requiring 3-5 microM Ca2+ for half-maximal binding. The antibody reacts with native and heat-denatured C1r, and with zymogen C1r, but does not cross-react with C1s or C1q. BG6 did not significantly affect the esterolytic activity of C1r toward a synthetic thioester substrate nor the hemolytic activity of C1 reconstituted from subcomponents in the presence of the antibody. A tryptic fragment of C1r which consists of the C-terminal gamma region of the A chain disulfide-linked to the B chain (gamma B) binds in a Ca(2+)-dependent manner to BG6-Sepharose. Western blotting experiments have further localized the epitope to the gamma region of the A chain, which is composed of two short consensus repeat (SCR) units. The N-terminal alpha region contains the only previously determined Ca(2+)-binding site in the C1r molecule. Equilibrium dialysis experiments confirmed that C1r-gamma B does not bind Ca2+, and showed that antibody BG6 and the gamma B/BG6 complex do bind Ca2+. Thus, the Ca(2+)-dependent nature of this interaction is due exclusively to binding of the metal ion to the antibody. Equilibrium dialysis and immunoblotting have further localized the Ca(2+)-binding site to the Fab fragment of BG6, indicating that the metal-induced conformational change residues in or near the variable region of the IgG. BG6 may set a precedent for the preparation of Ca(2+)-dependent antibodies to non-Ca(2+)-binding epitopes in other proteins.     

Recombinant lipid transfer protein Cor a 8 from hazelnut: a new tool for in vitro diagnosis of potentially severe hazelnut allergy

BACKGROUND: Cor a 1.04 has been identified as the major hazelnut allergen in 65 European patients with positive double-blind, placebo-controlled food challenge results to hazelnut. Recently, the 11S globulin Cor a 9 was shown to be a pollen-independent hazelnut allergen in the United States, whereas preliminary data suggest the lipid transfer protein (LTP) as an important birch pollen-unrelated hazelnut allergen in Europe. OBJECTIVE: We sought to recruit a group of European patients allergic to hazelnut without birch pollen allergy and to identify and clone the major food allergen(s) in this study population. METHODS: We recruited 26 such Spanish patients, including 10 patients with anaphylaxis. IgE immunoblotting was performed with hazelnut extract. Hazelnut LTP Cor a 8 was cloned by using a PCR strategy, purified, and subjected to IgE immunoblotting. Recombinant Cor a 8, rCor a 1.0401, and rCor a 2 (profilin) were further investigated by means of enzyme allergosorbent test. Immunoblot inhibition experiments were used to compare the immunologic properties of natural and recombinant LTP. RESULTS: A 9-kd major allergen was identified in hazelnut extract. Cloning, sequencing, heterologous expression, and inhibition experiments identified it as an LTP. The prevalence of specific IgE antibody reactivity to LTP was 62% in hazelnut extract and 77% when recombinant LTP was tested by means of immunoblotting. IgE immunoblot inhibition with hazelnut extract showed that natural Cor a 8 and rCor a 8 shared identical epitopes. Only one patient had positive reactivity to Cor a 1.04, and no patients had positive reactivity to Cor a 2. Two sera bound to high-molecular-weight allergens. The LTP was denominated as Cor a 8 and submitted to the allergen database of the World Health Organization/International Union of Immunological Societies Allergen Nomenclature Subcommittee. CONCLUSIONS: Cor a 8 is a relevant allergen for a majority of Spanish patients with hazelnut allergy that can cause severe allergic reactions.     

Calsequestrin expression and calcium binding is increased in streptozotocin-induced diabetic rat skeletal muscle though not in cardiac muscle

Altered mechanisms of Ca2+ transport may underlie the contractile dysfunctions that have been frequently reported to occur in diabetic cardiac and skeletal muscle tissues. Calsequestrin, a high-capacity Ca2+-binding protein, is involved in the regulation of the excitation-contraction-relaxation cycle of both skeletal and cardiac muscle fibres. We have investigated the expression of calsequestrin and Ca2+ binding in cardiac and skeletal muscle from streptozotocin-induced diabetic rat. Immunoblotting of microsomal membranes from normal and streptozotocin-induced diabetic muscle revealed no significant changes in heart, but an increase in the relative abundance of calsequestrin and calsequestrin-like proteins in skeletal muscle. In analogy, the overall Ca2+-binding capacity of sarcoplasmic reticulum vesicles from diabetic skeletal muscle was drastically increased. The expression of fast muscle marker proteins was not affected, indicating that no relevant fibre transformation occurred in streptozotocin-treated rat muscles. The up-regulation of the high-capacity Ca2+-binding element calsequestrin might represent a compensatory mechanism of diabetic skeletal muscle. An increased Ca2+-buffering capacity of the sarcoplasmic reticulum lumen might counteract elevated cytosolic Ca2+ levels in diabetes thereby preventing Ca2+-dependent myo-necrosis.     

Comparison of four variants of a major allergen in hazelnut (Corylus avellana) Cor a 1.04 with the major hazel pollen allergen Cor a 1.01.

The aim of this study was to produce the Bet v 1-related major hazelnut allergen Cor a 1.0401 and variants thereof as recombinant allergens, and to compare their immuno-reactivity with the major hazel pollen allergen using sera of patients whose hazelnut allergy recently was confirmed by double-blind placebo-controlled food challenges (DBPCFC) in a multicenter study.Total RNA was isolated from immature hazelnuts and transcribed into cDNA. Full length coding DNA obtained by PCR-strategy was subcloned into pTYB11 vector and expressed in E. coli ER2566 cells. Native non-fusion target proteins were purified by DTT-induced self-cleavage of the intein-tagged N-terminal fusion proteins. IgE reactivity of the recombinant allergens was tested by enzyme allergosorbent test (EAST), EAST-inhibition, immunoblot-inhibition and histamine release assays. Four recombinant allergens were produced showing deduced amino acid sequence identities among each other of 97-99%, and were considered as variants Cor a 1.0401 (GenBank Accession no.: AF136945), Cor a 1.0402 (AF323973), Cor a 1.0403 (AF323974) and Cor a 1.0404 (AF323975). Cor a 1.0402 and 03 only differed in a C4S exchange. Cor a 1.0404 had a unique proline residue in position 99. Surprisingly, only 63% identity was revealed with hazel pollen Cor a 1. EAST with 43 sera of patients with positive DBPCFC to hazelnut indicated IgE reactivity to Cor a 1.0401 in 95% of the sera, to Cor a 1.0402 in 93%, to Cor a 1.0403 in 91%, and in only 74% of the sera to the proline variant Cor a 1.0404. The allergenic activity of the four variants was confirmed by histamine release assays in 15 hazelnut-allergic patients stimulated with the four variants and controls. Eleven sera were positive with extract from native hazelnut, 13 with rCor a 1.0401, 12 with rCor a 1.0402, 11 with rCor a 1.0403, and only two with rCor a 1.0404 containing the proline exchange. The high IgE binding variant Cor a 1.0401 showed only partial IgE cross-reactivity with pollen Cor a 1. IgE-binding and histamine release capacity led to a concordant ranking of the allergenic activity of the recombinant variants: Cor a 1.0401>Cor a 1.0402 and 03>Cor a 1.0404 (the proline variant). Similar results for Cor a 1.0402 and 03 suggest a minor influence in IgE binding of cysteine in position 4, whereas proline in position 99 appears to be responsible for the decrease in IgE reactivity in Cor a 1.0404. It appears that the epitopes of hazelnut Cor a 1.04 are less related to pollen Cor a 1 than to Bet v 1 from birch pollen. Low IgE binding variants or mutants of Cor a 1.04 are candidate compounds for developing a novel and safe approach of specific immunotherapy of hazelnut allergy.     

Olive pollen allergen Ole e 8: identification in mature pollen and presence of Ole e 8-like proteins in different pollens

In a first approach, Ole e 8, a novel Ca2+-binding protein from olive pollen, was cloned and produced in Escherichia coli. We have obtained the natural form of Ole e 8 (nOle e 8) from the pollen and examined its immunologic equivalence with its recombinant form (rOle e 8). Size exclusion chromatography and a phenyl-Sepharose CL-4B affinity column were used to obtain nOle e 8 from the olive pollen. Inhibition assays by immunoblotting, using rOle e 8-specific rabbit antiserum, were performed to analyze the immunologic equivalence between the natural and the recombinant allergen, as well as to detect its presence in other pollens. Recombinant and natural Ole e 8 resulted immunologically equivalents, since they completely inhibited the IgG binding of the polyclonal antiserum to each other. Ole e 8-like proteins were detected in Oleaceae and Juniperus communis pollen, and might contribute to cross-reactivity processes between taxonomically related pollens.     

Differential modulation of voltage-dependent Ca2+ currents by EGTA and BAPTA in bovine adrenal chromaffin cells

Whole-cell patch-clamp recordings were made to examine the effects of the Ca2+ chelators EGTA and BAPTA on the biophysical properties of voltage-operated Ca2+ currents in bovine adrenal chromaffin cells. Ca2+ currents in the presence of either EGTA or BAPTA over a concentration range of 0.1-60 mM were recorded under otherwise identical conditions. Analysis of current-voltage relationships yielded unexpected differences in several important parameters such as the voltage dependence of activation, kinetics, slope, and reversal potential, which seemed to be unrelated to the Ca(2+)-binding properties of these chelators. Increasing concentrations of BAPTA augmented the peak Ca2+ current amplitude while current amplitudes in the presence of EGTA remained constant over the entire concentration range tested. Increasing concentrations of BAPTA shifted the voltage sensitivity of Ca2+ currents by about 15 mV towards positive voltages. EGTA, over the same concentration range, did not affect the voltage sensitivity. The shift in voltage sensitivity observed with BAPTA was unrelated to its faster Ca92+)-binding kinetics, as it was also observed when substituting Ca2+ with Ba2+ as the charge carrier. The mechanism by which BAPTA affects Ca2+ channel voltage dependence also seems unrelated to kinase-mediated modulation of Ca2+ channels, since the protein-kinase-C- (PKC-) specific drugs bisindolylmaleimide and phorbol ester (PMA) neither mimicked nor prevented the action of BAPTA. The less specific kinase inhibitor staurosporine, however, augmented Ca2+ currents similarly to BAPTA, but without affecting the voltage sensitivity. The BAPTA-mediated shift in voltage sensitivity was partially suppressed by non-hydrolysable analogs of GTP (GDP[beta-S] and GTP[gamma-S]). Lowering [Mg2+]i mimicked the BAPTA-induced shift in voltage sensitivity and prevented further shifts in voltage sensitivity by BAPTA. The results demonstrate that BAPTA and EGTA, despite their similarities in terms of Ca2+ buffering, have disparate effects on the voltage dependence of Ca2+ channels and careful selection of the chelator is required to quantitatively assess Ca2+ currents.     

Interaction of calcium and Ro60: increase of antigenicity

The structural and functional integrity of the cell is largely maintained by protein-protein interactions. Recently, we demonstrated that multiple antigenic peptides (MAPs) constructed from 60 kDa Ro sequence could be used to show intramolecular and intermolecular protein-protein interaction within the 60 kDa Ro ribonucleoprotein particle. We were interested in understanding the mechanism of this binding and hypothesized that this interaction might be mediated through divalent metal ions. The 60 kDa Ro-MAPs failed to interact with purified 60 kDa Ro in the presence of EDTA or EGTA when analyzed by Ouchterlony or surface plasmon resonance (SPR) analysis. When purified 60 kDa Ro was incubated with various metal ions such as Cu2+, Mg2+, Zn2+ and Ca2+, and analyzed by Ouchterlony or SPR for binding to specific 60 kDa Ro-MAPs only Ca2+ ions significantly increased the binding. It was interesting to note that recombinant 60 kDa Ro formed precipitin lines with Ro-MAPs only in the presence of Ca2+ ions. Anti-Ro60 containing SLE sera bound to recombinant Ro60 strongly when incubated in the presence of Ca2+ ions but not in the absence of Ca2+ ions. Using SPR analysis we also found that native Ro60 binds to La only in the presence of Ca2+. These data imply that Ca2+ induces a more native tertiary structure to recombinant 60 kDa Ro and makes it more antigenic. Thus, the observed intramolecular and intermolecular interactions and antigen-antibody interactions could be Ca2+ ion mediated conformational interactions, and we propose that 60 kDa Ro is a calcium binding protein.     

Regulation of human basophil activation. I. Dissociation of cationic dye binding from histamine release in activated human basophils.

Human basophil activation was demonstrated by histamine release (HR) and by the decrease of the toluidine blue-positive basophils (TB+). In four experimental systems, TB+ number decreased in the absence of HR (1) in basophils from atopic subjects stimulated by allergen concentrations below the threshold for HR, (2) in basophils sensitized by anti-2,4-dinitrophenyl IgE stimulated by noncovalently linked 2,4-dinitrobenzene sulfonic acid-human serum albumin (also, the threshold for decrease of TB+ required lower concentrations of sensitizing anti-2,4-dinitrophenyl IgE than for HR), (3) in low Ca++ medium, and (4) in the presence of the Na+/H+ exchanger, monensin. These results suggest that (1) there is a lower threshold for TB+ decrease than for HR in allergen concentration, number of membrane IgE molecules, and number of IgE cross-linkings; moreover, external Ca++ requirement is lower for decrease of TB+ than for HR and (2) TB+ decrease reflects either granule exocytosis or, in the absence of HR, biochemical changes (most probably cation exchanges) altering the interaction of the basic dye with the granules. Thus, monitoring decrease in TB+ allows detection of basophil activation in the absence of HR.