PKA modulates GSK-3beta- and cdk5-catalyzed phosphorylation of tau in site- and kinase-specific manners

Phosphorylation of tau protein is regulated by several kinases, especially glycogen synthase kinase 3beta (GSK-3beta), cyclin-dependent protein kinase 5 (cdk5) and cAMP-dependent protein kinase (PKA). Phosphorylation of tau by PKA primes it for phosphorylation by GSK-3beta, but the site-specific modulation of GSK-3beta-catalyzed tau phosphorylation by the prephosphorylation has not been well investigated. Here, we found that prephosphorylation by PKA promotes GSK-3beta-catalyzed tau phosphorylation at Thr181, Ser199, Ser202, Thr205, Thr217, Thr231, Ser396 and Ser422, but inhibits its phosphorylation at Thr212 and Ser404. In contrast, the prephosphorylation had no significant effect on its subsequent phosphorylation by cdk5 at Thr181, Ser199, Thr205, Thr231 and Ser422; inhibited it at Ser202, Thr212, Thr217 and Ser404; and slightly promoted it at Ser396. These studies reveal the nature of the inter-regulation of tau phosphorylation by the three major tau kinases.     

A meta-analysis of HLA-DR polymorphism and genetic susceptibility to idiopathic dilated cardiomyopathy

Idiopathic dilated cardiomyopathy (IDC) has been hypothesized as a multifactorial disorder initiated by an environment trigger in individuals with predisposing human leukocyte antigen (HLA) alleles. Published data on the association between HLA-DR polymorphism and IDC risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. A total of 19 case–control studies including 1,378 cases and 10,383 controls provided data on the association between HLA-DR polymorphism and genetic susceptibility to IDC. Overall, statistically elevated frequencies of HLA-DR4 (OR 1.58; 95% CI 1.21–2.07; P = 0.0009) and HLA-DR5 (OR 1.35; 95% CI 1.05–1.73; P = 0.02) alleles were found in patients with IDC compared with controls. Individuals with HLA-DR3 antigen have a protective effect against IDC (OR 0.72; 95% CI 0.58–0.90; P = 0.004). In summary, this meta-analysis indicated that certain HLA-DR alleles may be genetic markers for susceptibility and resistance to IDC.     

Studies of lysozyme binding to histamine as a ligand for hydrophobic charge induction chromatography

Histamine was immobilized on Sepharose CL‐6B (Sepharose) for use as a ligand of hydrophobic charge induction chromatography (HCIC) of proteins. Lysozyme adsorption onto Histamine‐Sepharose (HA‐S) was studied by adsorption equilibrium and calorimetry to uncover the thermodynamic mechanism of the protein binding. In both the experiments, the influence of salt (ammonium sulfate and sodium sulfate) was examined. Adsorption isotherms showed that HA‐S exhibited a high salt tolerance in lysozyme adsorption. This property was well explained by the combined contributions of hydrophobic interaction and aromatic stacking. The isotherms were well fitted to the Langmuir equation, and the equilibrium parameters for lysozyme adsorption were obtained. In addition, thermodynamic parameters (ΔH_ads, ΔS_ads, and ΔG_ads) for the adsorption were obtained by isothermal titration calorimetry by titrating lysozyme solutions into the adsorbent suspension. Furthermore, free histamine was titrated into lysozyme solution in the same salt‐buffers. Compared with the binding of lysozyme to free histamine, lysozyme adsorption onto HA‐S was characterized by a less favorable ΔG_ads and an unfavorable ΔS_ads because histamine was covalently attached to Sepharose via a three‐carbon‐chain spacer. Consequently, the immobilized histamine could only associate with the residues on the protein surface rather than those in the hydrophobic pocket, causing a less favorable orientation between histamine and lysozyme. Further comparison of thermodynamic parameters indicated that the unfavorable ΔS_ads was offset by a favorable ΔH_ads, thus exhibiting typical enthalpy‐entropy compensation. Moreover, thermodynamic analyses indicated the importance of the dehydration of lysozyme molecule and HA‐S during the adsorption and a substantial conformational change of the protein during adsorption. The results have provided clear insights into the adsorption mechanisms of lysozyme onto the new HCIC material. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

ILK在肺鳞状细胞癌和肺腺癌的表达及其与临床病理特征和预后的关系

目的 探讨ILK在肺鳞状细胞癌和肺腺癌组织中的表达情况,及其与病理分型、肿瘤分化、分期、淋巴结转移及预后的关系。方法采用S-P免疫组织化学方法和Western Blot法,检测肺鳞状细胞癌和肺腺癌组织及相应癌旁肺组织中整合连接激酶（integrin-linkedkinase,ILK）的表达情况,并结合临床和病理资料进行分析。结果免疫组化结果显示：ILK在53／76（70％）的肺癌组织中阳性表达。其中鳞状细胞癌阳性率75％（33／44）,腺癌阳性率62．5％（20／32）,其表达与肺鳞状细胞癌的分化呈负相关（P〈0．01）,与临床分期（P〈0．01）、淋巴结转移（P〈0．01）呈正相关;与肺腺癌的临床分期（P〈0．01）和淋巴结转移（P〈0．01）正相关,与分化程度无相关性（P〉0．05）。同时,其表达与患者的生存时间呈负相关（P〈0．01）,与年龄、性别、肿瘤大小和组织类型等因素无关。Western Blot法进一步证实ILK在肺癌组织中的表达显著高于癌旁正常肺组织（P〈0．01）,其表达与肺癌的分化（P〈0．01）显著负相关。结论肺鳞状细胞癌和肺腺癌中,ILK与肺癌的侵袭和转移有关。ILK可作为判断肺鳞状细胞癌和肺腺癌预后的参考指标。     

大鼠生后发育期间胰腺IAPP免疫组织化学定位研究

本文应用免疫组织化学ＰＡＰ法对正常雄性Ｗｉｓｔａｒ大鼠生后发育期间胰腺ＩＡＰＰ－ＩＲ阳性细胞进行了定位研究。结果表明;生后１天的大鼠胰岛内即已存在ＩＡＰＰ－ＩＲ阳性细胞,双染法证实ＩＡＰＰ与胰岛素共存于胰岛Ｂ细胞的胞质内。ＩＡＰＰ细胞免疫反应强度随生后发育而变化,２８天以后趋于稳定。胰腺外分泌部也有散在的ＩＡＰＰ－ＩＲ细胞。本文初步探讨了上述结果的生物学意义。     

外源蛋白在大肠杆菌中的表达定位策略

外源基因在大肠杆菌中表达是对基因重组技术的成功应用。外源基因在不同的大肠杆菌表达系统中表达产物可能定位于大肠杆菌空间结构的不同位置:胞质,胞质膜,胞周质,胞外膜和胞外培养基,五种表达定位方式各有其特点和用途 。     

Monitoring vegetation recovery after China’s May 2008 Wenchuan earthquake using Landsat TM time-series data: a case study in Mao County

The Wenchuan earthquake (Richter scale 8) on 12 May 2008 in southwestern China caused widespread ecosystem damage in the Longmenshan area. It is important to evaluate natural vegetation recovery processes and provide basic information on ecological aspects of the recovering environment after the earthquake. To circumvent the weather limits of remote sensing in the Wenchuan earthquake-hit areas, and to meet the need for regional observation analyses, three Landsat TM images pre- and post-earthquake in Mao County were used for analysis. Post-earthquake normalized difference vegetation index (NDVI) values were compared to pre-earthquake values with an NDVI-based index differencing method to determine the extent to which the vegetation was damaged in relation to the pre-earthquake pattern, and the rate of recovery was evaluated. The spatial characteristics of vegetation loss and natural recovery patterns were analyzed in relation to elevation, slope and aspect. The results indicated that severely damaged sites occurred mainly in river valleys, within a range of 1,500?C2,500?m elevation and on slopes of 25?C55°. The distance from rivers, rather than the distance from active faults, controls the damage patterns. After 1?year of natural regeneration, 36?% of the destroyed areas showed a decrease in NDVI value, 28.8?% showed very little change, 19.1?% showed an increase, and 16.1?% also increased with a recovery rate greater than 100?%. Moreover, there is a good correlation between recovery rate and both slope and elevation, but recovery patterns in the damaged area are complicated. Our results indicate that natural recovery in this arid valley is a slow process.     

Suppression of tumorigenesis by human mesenchymal stem cells in a hepatoma model

Human mesenchymal stem cells (hMSCs) can home to tumor sites and inhibit the growth of tumor cells. Little is known about the underlying molecular mechanisms that link hMSCs to the targeted inhibition of tumor cells. In this study, we investigated the effects of hMSCs on two human hepatoma cell lines (H7402 and HepG2) using an animal transplantation model, a co-culture system and conditioned media from hMSCs. Animal transplantation studies showed that the latent time for tumor formation was prolonged and that the tumor size was smaller when SCID mice were injected with H7402 cells and an equal number of Z3 hMSCs. When co-cultured with Z3 cells, H7402 cell proliferation decreased, apoptosis increased, and the expression of Bcl-2, c-Myc, proliferating cell nuclear antigen (PCNA) and survivin was downregulated. After treatment with conditioned media derived from Z3 hMSC cultures, H4702 cells showed decreased colony-forming ability and decreased proliferation. Immunoblot analysis showed that beta-catenin, Bcl-2, c-Myc, PCNA and survivin expression was downregulated in H7402 and HepG2 cells. Taken together, our findings demonstrate that hMSCs inhibit the malignant phenotypes of the H7402 and HepG2 human liver cancer cell lines, which include proliferation, colony-forming ability and oncogene expression both in vitro and in vivo. Furthermore, our studies provide evidence that the Wnt signaling pathway may have a role in hMSC-mediated targeting and tumor cell inhibition.