Crystallization scale purification of α7 nicotinic acetylcholine receptor from mammalian cells using a BacMam expression system

Aim:

To report our methods for expression and purification of α7 nicotinic acetylcholine receptor (α7-nAChR), a ligand-gated pentameric ion channel and an important drug target.

Methods:

α7-nAChRs of 10 different species were cloned into an inducible BacMam vector with an N-terminal tag of a tandem maltose-binding protein (MBP) and a TEV cleavage site. This α7-nAChR fusion receptor was expressed in mammalian HEK293F cells and detected by Western blot. The expression was scaled up to liters. The receptor was purified using amylose resin and size-exclusion chromatography. The quality of the purified receptor was assessed using SDS-PAGE gels, thermal stability analysis, and negative stain electron microscopy (EM). The expression construct was optimized through terminal truncations and site-directed mutagenesis.

Results:

Expression screening revealed that α7-nAChR from Taeniopygia guttata had the highest expression levels. The fusion receptor was expressed mostly on the cell surface, and it could be efficiently purified using one-step amylose affinity chromatography. One to two milligrams of the optimized α7-nAChR expression construct were purified from one liter of cell culture. The purified α7-nAChR samples displayed high thermal stability with a Tm of 60 °C, which was further enhanced by antagonist binding but decreased in the presence of agonist. EM analysis revealed ring-like structures with a central hydrophilic hole, which was consistent with the pentameric assembly of the α7-nAChR channel.

Conclusion:

We have established methods for crystallization scale expression and purification of α7-nAChR, which lays a foundation for high-resolution structural studies using X-ray crystallography or single particle cryo-EM analysis.     

A recombinant varicella vaccine harboring a respiratory syncytial virus gene induces humoral immunity

The varicella-zoster virus (VZV) Oka vaccine strain (vOka) is highly efficient and causes few adverse events; therefore, it is used worldwide. We previously constructed recombinant vOka (rvOka) harboring the mumps virus gene. Immunizing guinea pigs with rvOka induced the production of neutralizing antibodies against the mumps virus and VZV.Here, we constructed recombinant vOka viruses containing either the respiratory syncytial virus (RSV) subgroup A fusion glycoprotein (RSV A–F) gene or RSV subgroup B fusion glycoprotein (RSV B–F) gene (rvOka-RSV A–F or rvOka-RSV B–F). Indirect immunofluorescence and Western blot analyses confirmed the expression of each recombinant RSV protein in virus-infected cells. Immunizing guinea pigs with rvOka-RSV A–F or rvOka-RSV B–F led to the induction of antibodies against RSV proteins. These results suggest that the current varicella vaccine genome can be used to generate custom-made vaccine vectors to develop the next generation of live vaccines.     

Maltese Mushroom (Cynomorium coccineum L.) as Source of Oil with Potential Anticancer Activity

The present study aimed to examine the potential anticancer properties of fixed oil obtained from Maltese mushroom (Cynomorium coccineum L.), an edible, non-photosynthetic plant, used in traditional medicine of Mediterranean countries to treat various ailments and as an emergency food during the famine. We investigated the effect of the oil, obtained from dried stems by supercritical fractioned extraction with CO₂, on B16F10 melanoma and colon cancer Caco-2 cell viability and lipid profile. The oil, rich in essential fatty acids (18:3n-3 and 18:2n-6), showed a significant growth inhibitory effect on melanoma and colon cancer cells. The incubation (24 h) with non-toxic oil concentrations (25 and 50 μg/mL) induced in both cancer cell lines a significant accumulation of the fatty acids 18:3n-3 and 18:2n-6 and an increase of the cellular levels of eicosapentaenoic acid (20:5n-3) with anticancer activity. Moreover, the oil exhibited the ability to potentiate the growth inhibitory effect of the antitumor drug 5-fluorouracil in Caco-2 cells and to influence the melanin content in B16F10 cells. The results qualify C. coccineum as a resource of oil, with potential benefits in cancer prevention, for nutraceutical and pharmaceutical applications.     

截断逆挽方对慢加急性肝衰竭大鼠肝细胞进入S期关键蛋白的影响

目的:观察截断逆挽方对慢加急性肝衰竭(ACLF)大鼠肝脏细胞进入S期关键蛋白的影响。方法:将150只Wistar大鼠随机分成3组,正常组(NC)、模型组(MC)及截断逆挽方组(JD)。采用人血清白蛋白联合D-氨基半乳糖和脂多糖急性攻击制作ACLF模型。JD组大鼠在急性攻击24 h后连续灌胃,在第5、10、15天平行取材。运用HE染色法观察大鼠肝脏组织结构,Western blot法检测转录因子E2F1的表达量,RT-PCR检测CyclinA、E和Cdc25 mRNA表达量。结果:与模型组相比,JD组大鼠E2F1的表达量明显增高,并在第10天时差异最为显著(P<0.05),CyclinA、E、Cdc25表达量均有不同程度升高;与正常组相比,JD组大鼠10 d、15 d时CyclinA mRNA表达量差异显著,JD组大鼠在10 d、15 d时Cdc25和CyclinE mRNA表达量均差异显著(P<0.05)。结论:截断逆挽方可以通过调节E2F1介导的细胞再生信号通路上的关键蛋白E2F1、CyclinA、CyclinE、Cdc25的表达,从而促使细胞进入S期,加快DNA复制进程,提高肝细胞的增殖率,发挥治疗ACLF的作用。     

Frequency and significance of M-mode echocardiographic evidence of mitral valve prolapse in clinically isolated pure mitral regurgitation: analysis of 65 patients having mitral valve replacement

To assess the reliability of M-mode echocardiographic patterns of mitral valve prolapse (MVP) (echo MVP) in detection of morphologic evidence of MVP (morphologic MVP), operatively excised mitral valves and corresponding M-mode echocardiograms from 65 patients with chronic, severe, isolated, pure mitral regurgitation (MR) were studied. Of the 65 patients, 45 (69%) had echo MVP (either holosystolic or mid-to-late systolic prolapse patterns on preoperative M-mode echograms) and 42 (93%) of them had morphologic MVP; of the 3 without morphologic MVP, 2 had ruptured chordae tendineae from infective endocarditis and 1 had papillary muscle dysfunction from atherosclerotic coronary heart disease. Of the 20 patients without echo MVP, 14 (70%) had no morphologic MVP (9 had papillary muscle dysfunction from coronary heart disease, 4 had infective endocarditis on previous normal valves and 1 had rheumatic heart disease). Of the 48 patients with morphologic MVP, 42 (88%) had echo MVP and most had considerably dilated mitral anulae; the other 6 had ruptured chordae tendineae with less degrees of anular dilatation. Of the 17 patients without morphologic MVP, 3 had echo MVP (coronary artery disease in 1 and infective endocarditis on a previous normal valve in 2); of the 14 with neither echo nor morphologic MVP, 9 had papillary muscle dysfunction from coronary artery disease, 4 had infective endocarditis on previously normal valves and 1 had rheumatic heart disease. The patients with very dilated mitral anuli and leaflet areas generally had holosystolic (hammocking) patterns on echo; the patients with small anuli and leaflet areas usually had mid-to-late systolic (buckling) prolapse patterns.     

Coincidence of familial platelet glycoprotein Ib/IX deficiency (Bernard-Soulier syndrome), idiopathic autoantibody against platelet glycoprotein Ib/IX,familial appearence of antiphospholipid antibodies,and familial factor XII deficiency

Summary The case of an 8-year-old boy with apparently homozygous Bernard-Soulier syndrome (platelet GP Ib/IX complex deficiency) and a transient idiopathic autoantibody against GP Ib/IX is described. He had been diagnosed with chronic autoimmune thrombocytopenia (due to the detection of antiplatelet autoantibodies) before Bernard-Soulier syndrome was proven. Both parents and his brother displayed intermediate deficiency of GP Ib/IX, thus indicating a heterozygote state for Bernard-Soulier syndrome. Alloimmunization as an explanation for the appearance of GP Ib/IX antiplatelet antibodies in the propositus can be excluded. A so-called pseudo Bernard-Soulier syndrome due to selective antibodies was also excluded. Flow cytometric analysis revealed residual expression of 2% GP Ib and 13% GP IX on the propositus' platelets. It seems that the propositus showed an idiopathic autoantibody against a platelet glycoprotein in which he is genetically deficient (but which is not completely lacking). Thus, in patients with untypical behavior upon therapy of autoimmune thrombocytopenia, other differential diagnoses should also be considered even if antiplatelet antibodies are detected. In addition, all family members displayed elevated concentrations of antiphospholipid antibodies. These findings raise the question of a genetic predisposition for the development of autoantibodies. Moreover, an F. XII deficiency was found in all family members except the mother.     

Prediction of maximal cardiac output in preoperative patients with coronary artery disease

Of 100 patients (89 men, 11 women) studied preoperatively to determine their aerobic and hemodynamic profiles at rest and during upright treadmill exercise. The mean maximal cardiac output (CO), measured using the direct Fick principle, was 57 ± 14% of average normal values. The reduction in maximal heart rate (63 ± 13% of normal) was a greater factor in the reduction in CO than stroke volume (88 ± 16% of normal). Maximal oxygen consumption (V?O₂max) was 48 ± 15% of normal and the greater reduction in V?O₂₂max compared with CO was due to lower peripheral extraction in the coronary patients. Variables that correlated with maximal CO in a univariate analysis included angina severity (r = ?0.45), V?O₂₂max (r = 0.67), maximal heart rate (r = ?0.31), left ventricular dysfunction (r = ?0.45), maximal systolic blood pressure (r = ?0.31) and number of vessels with ≥ 50% diameter reduction (r = ?0.3). Resting ejection fraction did not correlate with maximal CO. In a multivariate analysis, 4 variables correlated significantly (r = 0.77) with maximal CO: in order, V?O₂₂max, number of vessels with ≥ 50% stenosis, magnitude of ST depression and sex.