Exploring the Structure-Function Loop Adaptability of a (β/α)(8)-Barrel Enzyme through Loop Swapping and Hinge Variability

Cellulosomes are large extracellular multi-enzyme complexes that exhibit elevated activity on plant cell-wall polysaccharides. In the present study, the relationships between the conformational flexibility and efficacy of cellulosomes, and the inter-modules linkers of their scaffold protein were investigated. For this purpose, the length of the intrinsically disordered Ser/Thr-rich 50-residue linker connecting a Clostridium thermocellum and a Clostridium cellulolyticum cohesin in a hybrid scaffoldin (Scaf4) was changed by sequences ranging from 4 to 128 residues. The composition was also modified and new linkers composed of series of N, S or repeats of the EPPV motif were generated. Two model cellulases (Cel48F and Cel9G) appended with appropriate dockerins were subsequently bound to the engineered scaffoldins. All the resulting minicomplexes displayed the same activity on crystalline cellulose as the complex based on the initial Scaf4, and were found to be 2-fold more active than Cel48F and Cel9G bound to separate cohesins. Small-angle X-ray scattering assays of the engineered scaffoldins confirmed, however, that the size and the conformational flexibility of some of the new inter-cohesins linkers differed significantly from that of the initial 50 residue linker displayed by the parental Scaf4. Our data suggest that the synergy induced by proximity does not require a specific inter-cohesins sequence or distance. The present study reveals that complexation onto the hybrid scaffoldins modifies the type of soluble sugars released from crystalline cellulose by the selected cellulases, compared to the free enzyme system.     

Profiling of gender-specific rat plasma proteins associated with susceptibility or resistance to diet-induced obesity

Obesity-prone (OP) and obesity-resistant (OR) rats with different responses to development of obesity in spite of the same genetic background are useful animal models for searching for markers during the development of obesity. Here, we investigated whether plasma proteins of OP and OR rats may behave in a different way in males and females. We performed a comparative proteomic analysis using 2-DE combined with MALDI-TOF/MS on proteins from OP and OR male and female rats to discover gender-specific rat plasma proteins associated with susceptibility or resistance to diet-induced obesity. A total of 29 proteins showing differential expression between the groups were identified by MALDI-TOF/MS and database searches. These proteins were classified into 4 groups according to their regulation patterns in response to diet and gender. 22 proteins showed significant differences between OP and OR rats in males and/or females (Group I, II, and III) and 7 proteins exhibited only a high fat diet (HFD)-responsive difference in male or female rats (Group IV). In conclusion, the proteins negatively (ITIH3, FGG, TUBB5, and ZAG) or positively (Hp, ITIH4, and RBP) correlated with obesity found in this study could be used for selection of new targets for gender specific-medical treatment of obesity.     

Phosphoinositide-3-kinase inhibition elevates ferritin level resulting depletion of labile iron pool and blocking of glioma cell proliferation

Background

Elevated endogenous phosphoinositide-3-kinase (PI3K) activity is critical for cell proliferation in gliomas. Iron availability is one of the essential factors for cell growth and proliferation. However, any relation between PI3K and cellular iron homeostasis has not been understood so far.

p38 MAPK and ERK1/2 pathways are involved in the pro-apoptotic effect of notoginsenoside Ft1 on human neuroblastoma SH-SY5Y cells

Aims

This study aims to investigate the effect and the mechanisms of notoginsenoside Ft1, a natural compound exclusively found in P. notoginseng, on the proliferation and apoptosis of human neuroblastoma SH-SY5Y cells.

Main methods

CCK-8 assay was used to assess the cell proliferation. Flow cytometry was performed to measure the cell cycle distribution and cell apoptosis. Hoechst 33258 staining was conducted to confirm the morphological changes of apoptotic cells. Protein expression was detected by western blot analysis and caspase 3 activity was measured by colorimetric assay kit.

Key findings

Among the saponins examined, Ft1 showed the best inhibitory effect on cell proliferation of SH-SY5Y cells with IC₅₀ of 45 μM. Ft1 not only arrested the cell cycle at S, G₂/M stages, but also promoted cell apoptosis, which was confirmed by Hoechst 33258 staining. Further studies demonstrated that Ft1 up-regulated the protein expressions of cleaved caspase 3, phospho-p53, p21, and cyclin B1, but down-regulated that of Bcl-2. Moreover, Ft1 enhanced the phosphorylation of ERK1/2, JNK and p38 MAPK. However, the phosphorylation of Jak2 and p85 PI3K was reduced by Ft1. Inhibitors of p38 MAPK and ERK1/2 but not JNK abrogated the up-regulated protein expressions of cleaved caspase 3, p21 and down-regulated protein expression of Bcl-2 as well as elevated caspase 3 activity induced by Ft1.

Significance

Ft1 arrested the proliferation and elicited the apoptosis of SH-SY5Y cells possibly via p38 MAPK and ERK1/2 pathways, which indicates the potential therapeutic effect of it on human neuroblastoma.     

光周期调节马铃薯块茎形成的分子机制

光周期调节马铃薯块茎形成的分子机制研究最近取得了很大进展.综合介绍了赤霉素(gibberellins,GAs)、马铃薯StCOL3(CONSTANS-LIKE3)基因和StFT(FLOWERING LOCUST)基因以及蔗糖运输载体(sucrose transporters,SUTs)在短日照调节马铃薯块茎形成中的作用.