Novel polymer biomaterials and interfaces inspired from cell membrane functions

Background

Materials with excellent biocompatibility on interfaces between artificial system and biological system are needed to develop any equipments and devices in bioscience, bioengineering and medicinal science. Suppression of unfavorable biological response on the interface is most important for understanding real functions of biomolecules on the surface. So, we should design and prepare such biomaterials.

Scoop of review

One of the best ways to design the biomaterials is generated from mimicking a cell membrane structure. It is composed of a phospholipid bilayered membrane and embedded proteins and polysaccharides. The surface of the cell membrane-like structure is constructed artificially by molecular integration of phospholipid polymer as platform and conjugated biomolecules. Here, it is introduced as the effectiveness of biointerface with highly biological functions observed on artificial cell membrane structure.

Major conclusions

Reduction of nonspecific protein adsorption is essential for suppression of unfavorable bioresponse and achievement of versatile biomedical applications. Simultaneously, bioconjugation of biomolecules on the phospholipid polymer platform is crucial for a high-performance interface.

General significance

The biointerfaces with both biocompatibility and biofunctionality based on biomolecules must be installed on advanced devices, which are applied in the fields of nanobioscience and nanomedicine.This article is part of a Special Issue entitled Nanotechnologies - Emerging Applications in Biomedicine.     

Systematic characterization of Escherichia coli genes/ORFs affecting biofilm formation

To understand the nature and function of bacterial biofilm and the process of its formation, we have performed systematic screening of a complete set of Escherichia coli genes/open reading frames (ORFs) to identify those that affect biofilm development upon over-expression. In contrast to the biofilm of strain AG1 used as a control, some of the genes/ORFs when over-expressed led to the formation of an abnormal biofilm such as thin, mat-like, filamentous or one easily detaching from various surfaces. Disruptants of selected genes were constructed in order to clarify their roles in the different stages of biofilm formation. Our results suggest that diverse metabolic pathways contribute to the development of biofilm.     

L1cam Is Crucial for Cell Locomotion and Terminal Translocation of the Soma in Radial Migration during Murine Corticogenesis

L1cam (L1) is a cell adhesion molecule associated with a spectrum of human neurological diseases, the most well-known being X-linked hydrocephalus. Although we recently demonstrated that L1 plays an important role in neuronal migration during cortical histogenesis, the mechanisms of delayed migration have still not been clarified. In this study, we found that cell locomotion in the intermediate zone and terminal translocation in the primitive cortical zone (PCZ) were affected by L1-knockdown (L1-KD). Time-lapse analyses revealed that L1-KD neurons produced by in utero electroporation of shRNA targeting L1 (L1-shRNAs) molecules showed decreased locomotion velocity in the intermediate zone, compared with control neurons. Furthermore, L1-KD neurons showed longer and more undulated leading processes during translocation through the primitive cortical zone. The curvature index, a quantitative index for curvilinearity, as well as the length of the leading process, were increased, whereas the somal movement was decreased in L1-KD neurons during terminal translocation in the PCZ. These results suggest that L1 has a role in radial migration of cortical neurons.     

A Novel Non-canonical Forkhead-associated (FHA) Domain-binding Interface Mediates the Interaction between Rad53 and Dbf4 Proteins

Forkhead-associated (FHA) and BRCA1 C-terminal (BRCT) domains are overrepresented in DNA damage and replication stress response proteins. They function primarily as phosphoepitope recognition modules but can also mediate non-canonical interactions. The latter are rare, and only a few have been studied at a molecular level. We have identified a crucial non-canonical interaction between the N-terminal FHA1 domain of the checkpoint effector kinase Rad53 and the BRCT domain of the regulatory subunit of the Dbf4-dependent kinase that is critical to suppress late origin firing and to stabilize stalled forks during replication stress. The Rad53-Dbf4 interaction is phosphorylation-independent and involves a novel non-canonical interface on the FHA1 domain. Mutations within this surface result in hypersensitivity to genotoxic stress. Importantly, this surface is not conserved in the FHA2 domain of Rad53, suggesting that the FHA domains of Rad53 gain specificity by engaging additional interaction interfaces beyond their phosphoepitope-binding site. In general, our results point to FHA domains functioning as complex logic gates rather than mere phosphoepitope-targeting modules.     

Genetic structure of <Emphasis Type="Italic">Cerasus jamasakura</Emphasis>, a Japanese flowering cherry,revealed by nuclear SSRs: implications for conservation

The genetic resources of a particular species of flowering cherry, Cerasus jamasakura, have high conservation priority because of its cultural, ecological and economic value in Japan. Therefore, the genetic structures of 12 natural populations of C. jamasakura were assessed using ten nuclear SSR loci. The population differentiation was relatively low (F _ST, 0.043), reflecting long-distance dispersal of seeds by animals and historical human activities. However, a neighbor-joining tree derived from the acquired data, spatial analysis of molecular variance and STRUCTURE analysis revealed that the populations could be divided into two groups: one located on Kyusyu Island and one on Honshu Island. Genetic diversity parameters such as allelic richness and gene diversity were significantly lower in the Kyushu group than the Honshu group. Furthermore, STRUCTURE analysis revealed that the two lineages were admixed in the western part of Honshu Island. Thus, although the phylogeographical structure of the species and hybridization dynamics among related species need to be evaluated in detail using several marker systems, the Kyusyu Island and Honshu Island populations should be considered as different conservation units, and the islands should be regarded as distinct seed transfer zones for C. jamasakura, especially when rapid assessments are required.     

Synergistic saccharification, and direct fermentation to ethanol, of amorphous cellulose by use of an engineered yeast strain codisplaying three types of cellulolytic enzyme

A whole-cell biocatalyst with the ability to induce synergistic and sequential cellulose-degradation reaction was constructed through codisplay of three types of cellulolytic enzyme on the cell surface of the yeast Saccharomyces cerevisiae. When a cell surface display system based on alpha-agglutinin was used, Trichoderma reesei endoglucanase II and cellobiohydrolase II and Aspergillus aculeatus beta-glucosidase 1 were simultaneously codisplayed as individual fusion proteins with the C-terminal-half region of alpha-agglutinin. Codisplay of the three enzymes on the cell surface was confirmed by observation of immunofluorescence-labeled cells with a fluorescence microscope. A yeast strain codisplaying endoglucanase II and cellobiohydrolase II showed significantly higher hydrolytic activity with amorphous cellulose (phosphoric acid-swollen cellulose) than one displaying only endoglucanase II, and its main product was cellobiose; codisplay of beta-glucosidase 1, endoglucanase II, and cellobiohydrolase II enabled the yeast strain to directly produce ethanol from the amorphous cellulose (which a yeast strain codisplaying beta-glucosidase 1 and endoglucanase II could not), with a yield of approximately 3 g per liter from 10 g per liter within 40 h. The yield (in grams of ethanol produced per gram of carbohydrate consumed) was 0.45 g/g, which corresponds to 88.5% of the theoretical yield. This indicates that simultaneous and synergistic saccharification and fermentation of amorphous cellulose to ethanol can be efficiently accomplished using a yeast strain codisplaying the three cellulolytic enzymes.     

Construction of Yeast Strains with High Cell Surface Lipase Activity by Using Novel Display Systems Based on the Flo1p Flocculation Functional Domain

We constructed a novel cell-surface display system, using as a new type of cell-wall anchor 3,297 or 4,341 bp of the 3′ region of the FLO1 gene (FS or FL gene, respectively), which encodes the flocculation functional domain of Flo1p. In this system, the N terminus of the target protein was fused to the FS or FL protein and the fusion proteins were expressed under the control of the inducible promoter UPR-ICL (5′ upstream region of the isocitrate lyase of Candida tropicalis). Using this new system, recombinant lipase with a pro sequence from Rhizopus oryzae (rProROL), which has its active site near the C terminus, was displayed on the cell surface. Cell-surface display of the FSProROL and FLProROL fusion proteins was confirmed by immunofluorescence microscopy and immunoblotting. Lipase activity reached 145 IU/liter (61.3 IU/g [dry cell weight]) on the surface of the yeast cells, which successfully catalyzed the methanolysis reaction. Using these whole-cell biocatalysts, methylesters synthesized from triglyceride and methanol reached 78.3% after 72 h of reaction. To our knowledge, this is the first example of cell-surface display of lipase with high activity. Interestingly, the yeast cells displaying the FLProROL protein showed strong flocculation, even though the glycosylphosphatidylinositol anchor attachment signal and cell-membrane-anchoring region of Flo1p had been deleted from this gene. The cell-surface display system based on FL thus endows the yeast strain with both novel enzyme display and strong flocculation ability.