Cellular functions of cardiolipin in yeast

Cardiolipin (CL), the signature lipid of mitochondria, plays a critical role in mitochondrial function and biogenesis. The availability of yeast mutants blocked in CL synthesis has facilitated studies of the biological role of this lipid. Perturbation of CL synthesis leads to growth defects not only during respiratory growth but also under conditions in which respiration is not essential. CL was shown to play a role in mitochondrial protein import, cell wall biogenesis, aging and apoptosis, ceramide synthesis, and translation of electron transport chain components. The genetic disorder Barth syndrome (BTHS) is caused by mutations in the tafazzin gene resulting in decreased total CL levels, accumulation of monolysocardiolipin (MLCL), and decreased unsaturated fatty acyl species of CL. The variation in clinical presentation of BTHS indicates that other physiological factors play a significant role in modifying the phenotype resulting from tafazzin deficiency. Elucidating the functions of CL is expected to shed light on the role of this important lipid in BTHS and other disorders of mitochondrial dysfunction.     

ATP in current biotechnology: Regulation,applications and perspectives

Adenosine tri-phosphate (ATP), the most important energy source for metabolic reactions and pathways, plays a vital role in the growth of industrial strain and the production of target metabolites. In this review, current advances in manipulating ATP in industrial strains, including altering NADH availability, and regulating NADH oxidation pathway, oxygen supply, proton gradient, the electron transfer chain activity and the F₀F₁-ATPase activity, are summarized and discussed. By applying these strategies, optimal product concentrations, yields and productivity in industrial biotechnology have been achieved. Furthermore, the mechanisms by which ATP extends the substrate utilization spectra and enhances the ability to challenge harsh environmental stress have been elucidated. Finally, three critical issues related to ATP manipulation have been addressed.     

Curcumin-Induced DNA Damage and Inhibited DNA Repair Genes Expressions in Mouse–Rat Hybrid Retina Ganglion Cells (N18)

Curcumin is reported to be a potent inhibitor of the initiation and promotion of many cancer cells. We investigated to examine whether or not curcumin induce DNA damage in mouse–rat hybrid retina ganglion cell line N18 cells. The Comet assay showed that incubation of N18 cells with 10, 25 and 30 μM of curcumin led to a longer DNA migration smear (Comet tail). The DNA gel electrophoresis showed that 20 μM of curcumin for 24 and 48 h treatment induced DNA damage and fragments in N18 cells. The real time PCR analysis showed that 20 μM of curcumin for 48 h treatment decreased ATM, ATR, BRCA1, 14-3-3σ, DNA-PK and MGMT mRNA, and ATM and MGMT mRNA expression were inhibited in a time-dependent manner. Our results indicate that curcumin caused DNA damage and inhibited DNA repair genes which may be the factors for curcumin-inhibited cell growth. H.-F. Lu and J.-S. Yang are contributed equally to this study.     

Thirty allele-level haplotypes centered around KIR2DL5 define the diversity in an African American population

KIR2DL5 alleles were physically linked to alleles at adjacent KIR loci to define this region of KIR haplotypes in 55 gene-positive random African Americans. The majority carried KIR2DL5B. Three KIR2DL5A and six KIR2DL5B alleles that have been previously described and 11 novel KIR2DL5 alleles were identified by DNA sequencing. Novel alleles included variation that may impact promoter activity; two alleles carried nonsynonymous coding region variation. Based on linkage with KIR2DS1, KIR2DS3, KIR2DS5, KIR2DL2, KIR2DL3, and KIR3DS1 alleles, seven haplotypes of KIR2DL5A and 23 haplotypes of KIR2DL5B were observed. The phylogenetic relationships among the KIR2DL5 alleles predicted their association with either KIR2DS3 (six alleles) or KIR2DS5 (seven alleles). All of the KIR2DL5A alleles were linked either to KIR3DS1*01301 or KIR3DS1*049N. The majority of the KIR2DL5B alleles were linked to seven KIR2DL2 alleles; two were linked to a novel allele of KIR2DL3. These findings underscore the diversity of KIR haplotypes present in this population.     

Functional characterization of the translationally controlled tumor protein (<Emphasis Type="Italic">TCTP</Emphasis>) gene associated with growth and defense response in cabbage

The translationally controlled tumor protein (TCTP) is an important component of the target of rapamycin (TOR) signaling pathway, the major regulator of cell growth in animals and fungi. Despite its relevance, knowledge on plant TCTP homologs is still limited. In the present study, the full-length BoTCTP cDNA was isolated from a cabbage (Brassica oleracea L.) cDNA library. The BoTCTP cDNA encodes a polypeptide of 168 amino acids and shared the highly conserved GTPase binding surface in all of the species analyzed. Northern blotting analysis showed that BoTCTP was specifically expressed in the root and stem. Furthermore, the expression of BoTCTP could be obviously enhanced by stress stimuli, including high temperature and salt stresses, while no significant changes in the BoTCTP expression were observed under ABA stress. Functional analysis of BoTCTP was performed by the silencing of BoTCTP using RNA interference (RNAi) and the BoTCTP RNAi plants exhibited reduced vegetative growth rate and decreased tolerance of the cold, high temperature, and salt stresses. The reported results clearly suggest that the BoTCTP gene is involved in the regulation of both growth and stress response in cabbage.     

Potential of a simple solid-phase extraction method coupled to analytical and bioanalytical methods for an improved determination of microcystins in algal samples

Artemia assays and protein phosphatase assays are commonly used for the screening of microcystins (MCs) in algal samples instead of the standard mouse toxicity assay. However, it has been shown that their results are often biased because of the matrix effects. To eliminate the possible interferences in the algal matrices, a new solid-phase extraction (SPE) method using silica gel as a sorbent was developed and evaluated. Results show that this SPE method could not only reduce the toxicity of the Microcystis samples towards brine shrimp by 50-80% but also eliminate 90-100% of the endogenous phosphatase activity from Spirulina and Chlorella samples, thus improving the determination of microcystins in algal samples using either of the two bioanalytical methods. The application of this SPE method as an off-line cleanup for high-performance liquid chromatography (HPLC) with UV detection is also described in this study. After SPE, the HPLC chromatograms of Microcystis samples have clear baselines that have no interferences with the analyte peaks.     

Stage-dependent effects of starvation on the growth, metamorphosis, and ecdysteroidogenesis by the prothoracic glands during the last larval instar of the silkworm, Bombyx mori

The stage-dependent effects of starvation on the growth, metamorphosis, and ecdysteroidogenesis of the prothoracic glands during the last larval instar of the silkworm, Bombyx mori, were studied in the present study. When last instar larvae were starved beginning on day 1 of that instar, all larvae died between days 5 and 7 of the instar. Although the prothoracicotropic hormone (PTTH) release from the brain-corpus cardiacum-corpus allatum (BR-CC-CA) did not significantly change during starvation, a deficiency in PTTH signal transduction was maintained, which led to very low levels of hemolymph ecdysteroids after the beginning of starvation. However, when starvation began on day 3 of the last larval instar, the major hemolymph ecdysteroid peak, preceding larval-pupal transformation, occurred 1 day earlier than that in control larvae. Protein content of the prothoracic glands in day 3-starved larvae was maintained at a low level as compared to that of control larvae. The secretory activity of the prothoracic glands in day 3-starved larvae was maintained at a level similar to that of control larvae. However, the rate of ecdysteroidogenesis, expressed per microgram of glandular protein, was greatly enhanced in these starved larvae, indicating that upon starvation, larvae increased the ecdysteroid production rate to enhance the rate of survival.     

Differences in binding specificity for the homologous gamma- and beta-chain "holes" on fibrinogen: exclusive binding of Ala-His-Arg-Pro-amide by the beta-chain hole

The beta-chain amino-terminal sequences of all known mammalian fibrins begin with the sequence Gly-His-Arg-Pro- (GHRP-), but the homologous sequence in chicken fibrin begins with the sequence Ala-His-Arg-Pro- (AHRP-). Nonetheless, chicken fibrinogen binds the synthetic peptide GHRPam, and a previously reported crystal structure has revealed that the binding is in exact conformance with that observed for the human GHRPam-fragment D complex. We now report that human fibrinogen, which is known not to bind APRP, binds the synthetic peptide AHRPam. Moreover, a crystal structure of AHRPam complexed with fragment D from human fibrinogen shows that AHRPam binds exclusively to the beta-chain hole and, unlike GHRPam, not at all to the homologous gamma-chain hole. The difference can be attributed to the methyl group of the alanine residue clashing with a critical carboxyl group in the gammaC hole but being accommodated in the roomier betaC hole where the equivalent carboxyl is situated more flexibly.