Distinctive roles of receptor‐interacting protein kinases 1 and 3 in caspase‐independent cell death of L929

Upon tumour necrosis factor alpha (TNFα) stimulation, cells respond actively by way of cell survival, apoptosis or programmed necrosis. The receptor‐interacting proteins 1 (RIP1) and 3 (RIP3) are responsible for TNFα‐mediated programmed necrosis. To delineate the differential contributions of RIP3 and RIP1 to programmed necrosis, L929 cells were stimulated with TNFα, carbobenzoxy‐valyl‐alanyl‐aspartyl‐[O‐methyl]‐fluoromethylketone (zVAD) or zVAD along with TNFα following RNA interference against RIP1 and RIP3, respectively. RIP1 silencing did not protect cells from TNFα‐mediated cell death, while RIP3 down‐regulation made them refractory to TNFα. The heat shock protein 90 inhibitor geldanamycin (GA) down‐regulated both RIP1 and RIP3 expression, which rendered cells resistant to zVAD/TNFα‐mediated cell death but not to TNFα‐mediated cell death alone. Therefore, the protective effect of GA on zVAD/TNFα‐stimulated necrosis might be attributed to RIP3, not RIP1, down‐regulation. Pretreatment of L929 cells with rapamycin mitigated zVAD‐mediated cell death, while the autophagy inhibitor chloroquine did not affect necrotic cell death. Meanwhile, necrotic cell death by zVAD and TNFα was caused by reactive oxygen species generation and effectively diminished by lipid‐soluble butylated hydroxyanisole. Taken together, the results indicate that RIP1 and RIP3 can independently mediate death signals being transduced by two different death stimuli, zVAD and TNFα. Copyright © 2013 John Wiley & Sons, Ltd.     

Continuous production of fructooligosaccharides using fructosyltransferase immobilized on ion exchange resin

A continuous production of fructooligosaccharides from sucrose was investigated by fructosyltransferase immobilized on a high porous resin, Diaion HPA 25. The optimum pH (5.5) and temperature (55°C) of the enzyme for activity was unaltered by immobilization, and the immobilized enzyme became less sensitive to the pH change. The optimal operation conditions of the immobilized enzyme column for maximizing the productivity were as follows: 600 g/L of sucrose feed concentration, flow rate of superficial space velocity 2.7 h^?1. When the enzyme column was run at 50°C, about 8% loss of the initial activity of immobilized enzyme was observed after 30 days of continuous operation, during which high productivity of 1174 g/L·h was achieved. The kinds of products obtained using the immobilized enzyme were almost the same as those using soluble enzymes or free cells.     

TBCD Links Centriologenesis,Spindle Microtubule Dynamics,and Midbody Abscission in Human Cells

Microtubule-organizing centers recruit α- and β-tubulin polypeptides for microtubule nucleation. Tubulin synthesis is complex, requiring five specific cofactors, designated tubulin cofactors (TBCs) A–E, which contribute to various aspects of microtubule dynamics in vivo. Here, we show that tubulin cofactor D (TBCD) is concentrated at the centrosome and midbody, where it participates in centriologenesis, spindle organization, and cell abscission. TBCD exhibits a cell-cycle-specific pattern, localizing on the daughter centriole at G1 and on procentrioles by S, and disappearing from older centrioles at telophase as the protein is recruited to the midbody. Our data show that TBCD overexpression results in microtubule release from the centrosome and G1 arrest, whereas its depletion produces mitotic aberrations and incomplete microtubule retraction at the midbody during cytokinesis. TBCD is recruited to the centriole replication site at the onset of the centrosome duplication cycle. A role in centriologenesis is further supported in differentiating ciliated cells, where TBCD is organized into “centriolar rosettes”. These data suggest that TBCD participates in both canonical and de novo centriolar assembly pathways.     

Inverted patterns of genetic diversity in continental and island populations of the heather Erica scoparia s.l.

Aim Using the heather Erica scoparia s.l. as a model, this paper aims to test theoretical predictions that island populations are genetically less diverse than continental ones and to determine the extent to which island and continental populations are connected by pollen‐ and seed‐mediated gene flow. Location Macaronesia, Mediterranean, Atlantic fringe of Europe. Methods Patterns of genetic diversity are described based on variation at two chloroplast DNA (cpDNA) loci and one nuclear DNA (nDNA) locus for 109 accessions across the entire distribution range of the species. Global patterns of genetic differentiation were investigated using principal coordinates analysis. Genetic differentiation between island and continental areas, estimations of pollen‐ and seed‐mediated gene flow, and the presence of phylogeographical signal were assessed by means of F_st /N_ST (continental scale) and F_ij/N_ij (local scale). Extant and past distribution ranges of the species were inferred from niche modelling using layers describing present and Last Glacial Maximum (LGM) macroclimatic conditions. Results The Azores exhibited a significantly higher genetic diversity than the continent. The lowest levels of genetic differentiation were observed between the Azores and the western Mediterranean, and the diversity observed in the Azores resulted from at least two colonization waves. Within the Azores, kinship coefficients showed a significant and much steeper decrease with geographical distance in the cpDNA than in the nDNA. The distribution predicted by LGM models was markedly different from the current potential distribution, particularly in western Europe, where no suitable areas were predicted by LGM models, and along the Atlantic coast of the African continent, where LGM models predicted highly suitable climatic conditions. Main conclusions The higher diversity observed in Azorean than in continental populations is inconsistent with MacArthur and Wilson’s equilibrium model and derived theoretical population genetic expectations. This inverted pattern may be the result of extinction on the continent coupled with multiple island colonization events and subsequent allopatric diversification and lineage hybridization in the Azores. The results highlight the role of allopatric diversification in explaining diversification on islands and suggest that this process has played a much more significant role in shaping Azorean biodiversity than previously thought.     

Role of interferons in the regulation of cell proliferation,differentiation, and development

There now appears to be evidence to support the view that the type I IFNs are naturally produced negative regulators of growth that also modify cell differentiation. Consistent with this, it appears that the ability to produce and respond to IFN is suppressed in early embryonic development when cell proliferation and differentiation are essential. In the later stages of fetal development, IFN production is de-repressed, and cells show increased sensitivity to IFN, which may be important in regulating cell proliferation and/or differentiation processes or the interaction between fetal and maternal tissues. Interestingly, the IFN system can also be suppressed in disease states such as the development of tumours or in the establishment of a (chronic) viral infection. Therefore, understanding the developmental regulation of the IFN system may be important to understanding and controlling the IFN system in disease. More extensive studies of the developmental stage and tissue-specific expression of type I IFNs and their receptors are necessary, as well as more direct in vivo experiments to further elucidate the role of the IFN system in reproduction and development. © 1994 Wiley-Liss, Inc.