The apoptosis-associated protein BNIPL interacts with two cell proliferation-related proteins,MIF and GFER

Bcl-2/adenovirus E1B 19 kDa interacting protein 2-like, BNIP-2-like (BNIPL) is a recently cloned and characterized apoptosis-associated protein that shares 72% homology with BNIP-2. It is highly expressed in human placenta and lung. A yeast two-hybrid system was used to obtain two BNIPL-interacting proteins, MIF (macrophage migration inhibitory factor) and GFER (growth factor erv1 (Saccharomyces cerevisiae)-like). The interactions were confirmed by glutathione S-transferase pull-down assay in vitro and co-immunoprecipitation assay in vivo. Colony formation assay and cell proliferation test suggest that overexpression of BNIPL could inhibit the growth of BEL-7402 cells. These findings suggest that BNIPL may physically bind to cell proliferation-related proteins, MIF and GFER.     

Generation of highly selective VPAC2 receptor agonists by high throughput mutagenesis of vasoactive intestinal peptide and pituitary adenylate cyclase-activating peptide

Pituitary adenylate cyclase-activating peptide (PACAP) has a specific receptor PAC1 and shares two receptors VPAC1 and VPAC2 with vasoactive intestinal peptide (VIP). VPAC2 activation enhances glucose-induced insulin release while VPAC1 activation elevates glucose output. To generate a large pool of VPAC2 selective agonists for the treatment of type 2 diabetes, structure-activity relationship studies were performed on PACAP, VIP, and a VPAC2 selective VIP analog. Chemical modifications on this analog that prevent recombinant expression were sequentially removed to show that a recombinant peptide would retain VPAC2 selectivity. An efficient recombinant expression system was then developed to produce and screen hundreds of mutant peptides. The 11 mutations found on the VIP analog were systematically replaced with VIP or PACAP sequences. Three of these mutations, V19A, L27K, and N28K, were sufficient to provide most of the VPAC2 selectivity. C-terminal extension with the KRY sequence from PACAP38 led to potent VPAC2 agonists with improved selectivity (100-1000-fold). Saturation mutagenesis at positions 19, 27, 29, and 30 of VIP and charge-scanning mutagenesis of PACAP27 generated additional VPAC2 selective agonists. We have generated the first set of recombinant VPAC2 selective agonists described, which exhibit activity profiles that suggest therapeutic utility in the treatment of diabetes.     

无牛血清IgG细胞培养基（—GFCS培养基）的制备及其在杂交瘤细胞体外培养中的应用

为了制备不含牛血清IgG的细胞培养基（－GFCS培养基）,并研究其在杂交瘤细胞体外培养中的应用,采用蛋白G亲和层析的方法,将含有血清的细胞培养基中的牛血清IgG去除,以制备无IgG的培养基。使用该培养基体外培养杂交瘤细胞后,监测细胞生长和上清抗体浓度。对培养上清中的IgG类单克隆抗体可以采用蛋白G亲和层析进行纯化。与示去除牛血清IgG的培养基相比,－GFCS培养基培养的杂交瘤细胞的生长状况及上清抗体浓度均无明显变化;从－GFCS培养上清中成功纯化出不被血清IgG污染的IgG类单克隆抗体,本文结果表明,采用－GFCS培养基体外培养分泌IgG类单抗的杂交瘤细胞,可以简化上清抗体的纯化工艺。     

Transmural recording of monophasic action potentials

To investigate the possibility of transmural recording of repolarization through the ventricular wall, KCl monophasic action potential (MAP) electrodes positioned along plunge needles were developed and tested. The MAP electrode consists of a silver wire surrounded by agarose gel containing KCl, which slowly eluted into the adjacent tissue to depolarize it. In six dogs, a plunge needle containing three KCl MAP electrodes was inserted into the left ventricle to simultaneously record from the subepicardium, midwall, and subendocardium. In six pigs, eight plunge needles containing three KCl MAP electrodes and two plunge needles containing similar electrodes except for the absence of KCl were inserted into the ventricles. In three guinea pig papillary muscles, a KCl electrode was used to record MAPs along with two microelectrodes for recording transmembrane potentials. Transmural MAP recordings could be made for >1 h in dogs and >2 h in pigs with a significant decrease in MAP amplitude over time but without a significant change in MAP duration. With the electrodes without KCl in pigs, the injury potentials subsided in <30 min. When the pacing rate was changed to alter the action potential duration and refractory period in dogs, the MAP duration correlated with the local effective refractory period (r = 0.94). The time course of the MAP duration recorded with a KCl MAP electrode in guinea pig papillary muscles corresponded well with that of the transmembrane potential recorded with an adjacent microelectrode. It is possible to record transmural repolarization of the ventricles with KCl MAP electrodes on plunge needles. The MAP is caused by the KCl rather than being a nonspecific injury potential.     

人扁桃体中应激免疫抑制蛋白的初步观察

以前的实验证明,在应激条件下,外周淋巴组织中产生一种蛋白质,具有抑制某些免疫功能的作用,称为应激免疫抑制蛋白（immune suppressive protein of stress,ISPS）。本实验用人外周淋巴器官扁桃体进行了研究,证明扁桃体的提取物能抑制小鼠由Con A诱导的淋巴细胞转化,而且这种抑制作用可被ISPS单克隆抗体（2C4）部分翻转。间接ELISA法证明人扁桃体提取物能与2C4单克隆抗体相结合。以ISPS单克隆抗体（2C4）作免疫组织化学研究,证明人扁桃体中有很多染色呈阳性的细胞。这些结果从不同角度提示,人外周淋巴组织中存在一种与ISPS相类似的免疫抑制物质。     

Circadian rhythms of DNA synthesis in nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) occurs frequently in southern China. The circadian rhythm of DNA synthesis of a poorly differentiated NPC human cell line (CNE2) was investigated as an experimental prerequisite for designing chrono-chemotherapy schedules for patients with this disease. Twenty-two nude mice with BALB/c background were synchronized alternatively in 12 h of light and 12 h of darkness (LD12:12) for at least 3 wk prior to the transplantation of a CNE2 tumor fragment into each flank (area of ∼2×2 mm²). Ten days later, a tumor sample (area of ∼5 mm²) was obtained at 3, 9, 15, and 21 h after light onset (HALO) alternatively from different sites in each mouse. Single-cell suspensions were prepared and stained with propidium iodide. Cellular DNA content was measured with flow cytometry. Data were analyzed by ANOVA and cosinor methods. The average proportion of tumor cells in G₁, S or G₂-M phase varied according to circadian time with statistical significance. The maximum occurred at 9 HALO for G1, 2 HALO for S and 21 HALO for G₂-M phase cells. The approximate average distribution patterns of G₁ and G₂-M phases of cosine curve was 24 h. This was not the case for S-phase cells, which displayed a bimodal temporal pattern. Inter-individual variability in peak time was large, possibly due to relatively sparse sampling time. Nevertheless, no more than 6% of the time series displayed a maximum at 3 HALO for G₁, 21 HALO for S and 15 HALO for G₂-M. The cell cycle distribution of this human NPC cell line displayed circadian regulation following implantation into nude mice. The mechanisms involved in this rhythm and its relevance to the chrono-chemotherapy of patients deserve further investigation.     

Acrylonitrile irreversibly inactivates glyceraldehyde-3-phosphate dehydrogenase by alkylating the catalytically active cysteine 149

Acrylonitrile (AN) is a vinyl monomer used in the production of synthetic fibers, rubber and plastics. AN is acutely toxic but its mechanism of toxicity remains to be established. AN is metabolized to cyanide in vivo but cyanide production alone cannot explain acute AN toxicity. Previous work in our laboratory has shown that AN can alkylate highly reactive cysteine residues in proteins. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a critical enzyme involved in glycolysis, has a catalytically active cysteine 149 in its active site. We report that AN irreversibly inhibits GAPDH with second-order rate constants, at pH 7.4, of 3.7 and 9.2 M⁻¹ s⁻¹ at 25 and 37 °C, respectively. A combination of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) and electrospray ionization–mass spectrometry–mass spectrometry (ESI–MS–MS) was used to show that AN inactivates GAPDH by covalently binding to cysteine 149 in the active site of the enzyme. Inactivation of GAPDH by AN would be expected to impair glycolytic ATP production and when coupled with the inhibition of mitochondrial ATP synthesis by the AN metabolite cyanide would result in metabolic arrest. The brain can withstand metabolic arrest for only a few minutes thus these combined actions may account for the acute toxicity of AN in vivo.     

Ganglioside GM(1) biphasically regulates the activity of protein kinase C by the effects on the structure of the lipid bilayer

Addition of a small amount of ganglioside GM(1) to phosphatidylserine (PS) liposomes, a gradual increase of protein kinase C (PKC) activity was recorded up to about 2 mol% GM(1) where the maximal enzyme activity was obtained. Then the activity of PKC began to decline and even turned to be inhibited with the further increase of GM(1) content. It was also indicated that GM(1)/PS binary liposomes had the highest membrane fluidity and very low spatial density of lipid headgroups which was demonstrated in the MC-540 studies due to the interposition of GM(1) when the liposomes contained about 2 mol% GM(1). Besides, the liposomes containing about 2 mol% GM(1) provided a more hydrophobic environment for PKC than the liposomes containing less or more GM(1) which was indicated in the Acrylodan experiments. These factors commonly induced PKC to be stimulated maximally. Whether at the lower or higher GM(1) content, the membrane structure was not the most suitable to support the activity of PKC, which declined as a consequence.     

Characterization of a heparan sulfate octasaccharide that binds to herpes simplex virus type 1 glycoprotein D

Herpes simplex virus type 1 utilizes cell surface heparan sulfate as receptors to infect target cells. The unique heparan sulfate saccharide sequence offers the binding site for viral envelope proteins and plays critical roles in assisting viral infections. A specific 3-O-sulfated heparan sulfate is known to facilitate the entry of herpes simplex virus 1 into cells. The 3-O-sulfated heparan sulfate is generated by the heparan sulfate d-glucosaminyl-3-O-sulfotransferase isoform 3 (3-OST-3), and it provides binding sites for viral glycoprotein D (gD). Here, we report the purification and structural characterization of an oligosaccharide that binds to gD. The isolated gD-binding site is an octasaccharide, and has a binding affinity to gD around 18 microm, as determined by affinity coelectrophoresis. The octasaccharide was prepared and purified from a heparan sulfate oligosaccharide library that was modified by purified 3-OST-3 enzyme. The molecular mass of the isolated octasaccharide was determined using both nanoelectrospray ionization mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry. The results from the sequence analysis suggest that the structure of the octasaccharide is a heptasulfated octasaccharide. The proposed structure of the octasaccharide is DeltaUA-GlcNS-IdoUA2S-GlcNAc-UA2S-GlcNS-IdoUA2S-GlcNH(2)3S6S. Given that the binding of 3-O-sulfated heparan sulfate to gD can mediate viral entry, our results provide structural information about heparan sulfate-assisted viral entry.