Purification and characterization of sea urchin initiation factor 2. The requirement of guanine nucleotide exchange factor for the release of eukaryotic polypeptide chain initiation factor 2-bound GDP

Protein synthesis in sea urchin eggs is stimulated dramatically upon fertilization. We previously demonstrated that this stimulation is primarily due to an increase in the rate of polypeptide chain initiation which in turn may be regulated at the level of recycling of eukaryotic initiation factor 2 (eIF-2) (Colin, A. M., Brown, B. D., Dholakia, J. N., Woodley, C. L., Wahba, A. J., and Hille, M. B. (1987) Dev. Biol. 123, 354-363). We have now purified eIF-2 from sea urchin Strongylocentrotus purpuratus blastulae to apparent homogeneity by chromatography on DEAE-cellulose, phosphocellulose, Mono Q, Mono P, and Mono S columns. The factor, which differs from mammalian eIF-2, is composed of three non-identical subunits with apparent molecular weights of 40,000-alpha; 47,000-beta, and 58,000-gamma as estimated by sodium dodecyl-polyacrylamide gel electrophoresis. Antibodies raised against rabbit reticulocyte eIF-2 do not cross-react with sea urchin eIF-2. The binding of Met-tRNA(f) to sea urchin eIF-2 is totally dependent on GTP. A 4-fold stimulation in the rate of protein synthesis in unfertilized sea urchin egg extracts is observed by the addition of 1 micrograms of purified eIF-2. The factor also binds GDP to form a binary (eIF-2.GDP) complex which is stable in the presence of Mg2+. GDP binding to sea urchin eIF-2 inhibits ternary (eIF-2-GTP.[35S]Met-tRNA(f) complex formation. The rabbit reticulocyte guanine nucleotide exchange factor (GEF) catalyzes the exchange of GDP bound to sea urchin eIF-2 for GTP and stimulates ternary complex formation. The requirement of GEF for the recycling of eIF-2 suggests that protein synthesis in sea urchins is similar to that in mammalian systems and may also be regulated at the level of GEF activity. The reticulocyte heme-controlled repressor phosphorylates the alpha-subunit of eIF-2 from both sea urchins and rabbit reticulocytes. However, casein kinase II which phosphorylates the beta-subunit of the reticulocyte factor specifically phosphorylates the alpha-subunit of sea urchin eIF-2. In this respect, the sea urchin factor is similar to eIF-2 isolated from other nonmammalian sources. Since both heme controlled repressor and casein kinase II phosphorylate the alpha-subunit of sea urchin eIF-2 caution should be exercised when interpreting the significance of eIF-2(alpha) phosphorylation in sea urchins.     

AZD8835 inhibits osteoclastogenesis and periodontitis-induced alveolar bone loss in rats

Chronic periodontitis (CP) is one of the most common oral diseases, which is characterized by the loss of connective tissue and alveolar bone in adults. AZD8835, a novel dual phosphoinositide-3-kinase (PI3K) inhibitor, is currently in phase 1 clinical evaluation to treat breast cancer. However, whether AZD8835 has any effect on teeth and alveolar bone health remains unclear. In the current study, we aimed to investigate the potential effect of AZD8835 in treating CP in vitro and in vivo. We found that AZD8835 could inhibit osteoclast differentiation, bone resorption, and downregulate the expression of osteoclast marker genes, such as tartrate-resistant acid phosphatase (Trap), cathepsin K (Ctsk), V-ATPase d2 (Atp6v0d2), and calcitonin receptor (Ctr). In addition, AZD8835 suppressed osteoclastogenesis by inhibiting receptor activator of nuclear factor kappa B ligand (RANKL)-induced PI3K/protein kinase B (AKT), extracellular signal-regulated kinase, and nuclear factor-κB signaling in BMMs. In vivo, AZD8835 greatly ameliorated alveolar bone (ABL) loss in rats with CP. Meanwhile, histological examination showed fewer osteoclasts in the treatment group. In conclusion, these results indicated that AZD8835 is a promising agent to reduce ABL in CP.     

Tomato stigma exsertion induced by high temperature is associated with the jasmonate signalling pathway

High temperature (HT) is becoming an increasingly serious factor in limiting crop production with global climate change. During hot seasons, owing to prevailing HT, cultivated tomatoes are prone to exhibiting stigma exsertion, which hampers pollination and causes fruit set failure. However, the underlying regulatory mechanisms of the HT‐induced stigma exsertion remain largely unknown. Here, we demonstrate that stigma exsertion induced by HT in cultivated tomato is caused by more seriously shortened stamens than pistils, which is different from the stigma exsertion observed in wild tomato species. Under the HT condition, the different responses of pectin, sugar, expansin, and cyclin cause cell wall remodelling and differentially localized cell division and selective cell enlargement, which further determine the lengths of stamens and pistils. In addition, auxin and jasmonate (JA) are implicated in regulating cell division and cell expansion in stamens and pistils, and exogenous JA instead of auxin treatment can effectively rescue tomato stigma exsertion through regulating the JA/COI1 signalling pathway. Our findings provide a better understanding of stigma exsertions under the HT condition in tomato and uncover a new function of JA in improving plant abiotic stress tolerance.     

Multi‐spectroscopic and molecular dynamics simulations investigation of the binding mechanism of polybrominated diphenyl ethers to hen egg white lysozyme

Three PBDEs (BDE25, BDE47, and BDE154) were selected to investigate the interactions between PBDEs and hen egg white lysozyme (HEWL) by molecular modeling, fluorescence spectroscopy, and FT‐IR spectra. The docking results showed that hydrogen bonds were formed between BDE25 and residue TRP63 and between BDE47 and TRP63 with bond lengths of 2.178 Å and 2.146 Å, respectively. The molecular dynamics simulations indicated that van der Waals forces played a predominant role in the binding of three PBDEs to HEWL. The observed fluorescence quenching can be attributed to the formation of complexes between HEWL and PBDEs, and the quenching mechanism is a static quenching. According to Förster's non‐radiative energy transfer theory, the binding distances r were < 7 nm, indicating a high probability of energy transfer from HEWL to the three PBDEs. The synchronous fluorescence showed that the emission maximum wavelength of tryptophan (TRP) residues emerged a red‐shift. FT‐IR spectra indicated that BDE25, BDE47 and BDE154 induced the α‐helix percentage of HEWL decreased from 32.70% ± 1.64% to 28.27% ± 1.41%, 27.50% ± 1.38% and 29.78% ± 1.49%, respectively, whereas the percentage of random coil increased from 26.67% ± 1.33% to 27.60% ± 1.38%, 29.18% ± 1.46% and 30.59% ± 1.53%, respectively.     

Correction to: Diversity and symbiotic divergence of endophytic and non-endophytic rhizobia of Medicago sativa

The authors wish to clarify that the right Fund No. of National Natural Science Foundation of China (NSFC) is 31560666. The Fund No. in the original article was wrong. The authors apologise for this error.     

Identification of Two Species of Yeast-like Symbiotes in the Brown Planthopper, <Emphasis Type="Italic">Nilaparvata lugens</Emphasis>

To determine the species of the yeast-like symbionts (YLS) in the brown planthoppers (BPH), Nilaparvata lugens, YLS were first isolated and purified by ultracentrifugation from the fat bodies of BPH, and then 18S rDNA and internal transcribed spacer (ITS)–5.8S rDNA sequences of YLS were amplified with the different general primers for fungi. The results showed that the two different 18S and ITS–5.8S rDNA sequences of YLS were obtained. One 2291-bp DNA sequence, which contained 18S and ITS–5.8S rDNA, showed the high similarity to Cryptococcus and was named Cryp-Like symbiotes. Another 1248-bp DNA sequence, which contained a part of 18S and ITS–5.8S rDNA, showed the high similarity to Pichia guilliermondii and was named Pichia-Like symbiotes. It was further proved that Cryp- and Pichia-Like symbiotes existed in BPH through nested PCR with specific primers for two symbiotes and in situ hybridization analysis using digoxigenin-labeled probes. Our results showed that BPH harbored more than one species of eukaryotic YLS, which suggested that diversity of fungal endosymbiotes may be occurred in planthoppers, just like bacterial endosymbiotes.     

Targeted overexpression of inducible 6-phosphofructo-2-kinase in adipose tissue increases fat deposition but protects against diet-induced insulin resistance and inflammatory responses

Increasing evidence demonstrates the dissociation of fat deposition, the inflammatory response, and insulin resistance in the development of obesity-related metabolic diseases. As a regulatory enzyme of glycolysis, inducible 6-phosphofructo-2-kinase (iPFK2, encoded by PFKFB3) protects against diet-induced adipose tissue inflammatory response and systemic insulin resistance independently of adiposity. Using aP2-PFKFB3 transgenic (Tg) mice, we explored the ability of targeted adipocyte PFKFB3/iPFK2 overexpression to modulate diet-induced inflammatory responses and insulin resistance arising from fat deposition in both adipose and liver tissues. Compared with wild-type littermates (controls) on a high fat diet (HFD), Tg mice exhibited increased adiposity, decreased adipose inflammatory response, and improved insulin sensitivity. In a parallel pattern, HFD-fed Tg mice showed increased hepatic steatosis, decreased liver inflammatory response, and improved liver insulin sensitivity compared with controls. In both adipose and liver tissues, increased fat deposition was associated with lipid profile alterations characterized by an increase in palmitoleate. Additionally, plasma lipid profiles also displayed an increase in palmitoleate in HFD-Tg mice compared with controls. In cultured 3T3-L1 adipocytes, overexpression of PFKFB3/iPFK2 recapitulated metabolic and inflammatory changes observed in adipose tissue of Tg mice. Upon treatment with conditioned medium from iPFK2-overexpressing adipocytes, mouse primary hepatocytes displayed metabolic and inflammatory responses that were similar to those observed in livers of Tg mice. Together, these data demonstrate a unique role for PFKFB3/iPFK2 in adipocytes with regard to diet-induced inflammatory responses in both adipose and liver tissues.     

小鼠血管内膜增生模型的建立

该文主要介绍一种可以在小鼠中有效地诱导血管内膜增生的方法。该方法使用硅胶管嵌套小鼠股动脉,造成股动脉血管内膜增生。病理切片观察表明,实验组小鼠股动脉与假手术组相比出现了内膜层和中膜层不规则增厚,管腔狭窄,细胞排列紊乱,内膜炎症细胞浸润等。免疫组织化学染色显示内膜增生部分是由于血管平滑肌细胞（VsMCs）增生和基质积聚所致。该模型的建立对动脉粥样硬化病理机制研究和治疗药物的研发具有重要意义。