Inhibition of aconitase by nitric oxide leads to induction of the alternative oxidase and to a shift of metabolism towards biosynthesis of amino acids

Nitric oxide (NO) is a free radical molecule involved in signalling and in hypoxic metabolism. This work used the nitrate reductase double mutant of Arabidopsis thaliana (nia) and studied metabolic profiles, aconitase activity, and alternative oxidase (AOX) capacity and expression under normoxia and hypoxia (1% oxygen) in wild-type and nia plants. The roots of nia plants accumulated very little NO as compared to wild-type plants which exhibited ～20-fold increase in NO emission under low oxygen conditions. These data suggest that nitrate reductase is involved in NO production either directly or by supplying nitrite to other sites of NO production (e.g. mitochondria). Various studies revealed that NO can induce AOX in mitochondria, but the mechanism has not been established yet. This study demonstrates that the NO produced in roots of wild-type plants inhibits aconitase which in turn leads to a marked increase in citrate levels. The accumulating citrate enhances AOX capacity, expression, and protein abundance. In contrast to wild-type plants, the nia double mutant failed to show AOX induction. The overall induction of AOX in wild-type roots correlated with accumulation of glycine, serine, leucine, lysine, and other amino acids. The findings show that NO inhibits aconitase under hypoxia which results in accumulation of citrate, the latter in turn inducing AOX and causing a shift of metabolism towards amino acid biosynthesis.     

Proteome-wide overexpression of host proteins for identification of factors affecting tombusvirus RNA replication: an inhibitory role of protein kinase C

To identify host genes affecting replication of Tomato bushy stunt virus (TBSV), a small model positive-stranded RNA virus, we overexpressed 5,500 yeast proteins individually in Saccharomyces cerevisiae, which supports TBSV replication. In total, we identified 141 host proteins, and overexpression of 40 of those increased and the remainder decreased the accumulation of a TBSV replicon RNA. Interestingly, 36 yeast proteins were identified previously by various screens, greatly strengthening the relevance of these host proteins in TBSV replication. To validate the results from the screen, we studied the effect of protein kinase C1 (Pkc1), a conserved host kinase involved in many cellular processes, which inhibited TBSV replication when overexpressed. Using a temperature-sensitive mutant of Pkc1p revealed a high level of TBSV replication at a semipermissive temperature, further supporting the idea that Pkc1p is an inhibitor of TBSV RNA replication. A direct inhibitory effect of Pkc1p was shown in a cell-free yeast extract-based TBSV replication assay, in which Pkc1p likely phosphorylates viral replication proteins, decreasing their abilities to bind to the viral RNA. We also show that cercosporamide, a specific inhibitor of Pkc-like kinases, leads to increased TBSV replication in yeast, in plant single cells, and in whole plants, suggesting that Pkc-related pathways are potent inhibitors of TBSV in several hosts.     

Methylenebissantin: a rare methylene-bridged bisflavonoid from Dodonaea viscosa which inhibits Plasmodium falciparum enoyl-ACP reductase

A new methylene-bridged bisflavonoid, methylenebissantin (1), and nine known compounds, including flavonoids (2-5), diterpenoids (6 and 7), and phenol derivatives (8-10) were isolated from the aerial parts of Dodonaea viscosa Jacq. The structure elucidation was based on spectroscopic data analyses. The isolated compounds were evaluated for the inhibition of Plasmodium falciparum enoyl-ACP reductase (PfENR). Methylenebissantin (1) exhibited a moderate inhibition (IC(50) 91.13 μM) against PfENR.     

Long-acting peptidomimetics based DPP-IV inhibitors

Pyrrolidine based peptidomimetics are reported as potent and selective DPP-IV inhibitors for the treatment of T2DM. Compounds 16c and 16d showed excellent in vitro potency and selectivity towards DPP-IV and the lead compound 16c showed sustained antihyperglycemic effects, along with improved pharmacokinetic profile.     

Novel bis(indolyl)hydrazide-hydrazones as potent cytotoxic agents

A series of bis(indolyl) hydrazide-hydrazones 5a-n were synthesized and evaluated for their cytotoxicity against selected human cancer cell lines. The reaction of indole-3-carboxaldehyde 2 with indole-3-carbohydrazide 4 in presence of catalytic amount of acetic acid afforded 5a-n in good yields. Among the synthesized bis(indolyl)hydrazide-hydrazones, the compound 5b with N-(p-chlorobenzyl) and bromo substituents was found to be the most potent against multiple cancer cell lines (IC(50)=1.0 μM, MDA-MB-231). The compound 5k exhibited selective cytotoxicity against breast cancer cell line MCF7 (IC(50)=3.1 μM).     

Urea/thiourea catalyzed, solvent-free synthesis of 5-arylidenethiazolidine-2,4-diones and 5-arylidene-2-thioxothiazolidin-4-ones

An efficient and organo-catalyzed method has been developed for the synthesis of 5-arylidenethiazolidine-2,4-diones and 5-arylidene-2-thioxothiazolidin-4-ones via Knoevenagel condensation of arylaldehydes 1 and 2,4-thiazolidinedione 2a/2-thioxothiazolidin-4-one 2b under mild conditions. Urea-adduct 4 and azomethine 5 also afford arylidene-products 3 by reacting with 2a-b via addition-elimination reaction. This protocol has the features of use of inexpensive, ecofriendly readily available, effective catalyst system viz. urea/thiourea, avoidance of volatile solvents, excellent yield and simple work-up procedure.     

Extracellular and intracellular esterase processing of SCFA–hexosamine analogs: Implications for metabolic glycoengineering and drug delivery

This report provides a synopsis of the esterase processing of short chain fatty acid (SCFA)-derivatized hexosamine analogs used in metabolic glycoengineering by demonstrating that the extracellular hydrolysis of these compounds is comparatively slow (e.g., with a t_1/2 of ～4 h to several days) in normal cell culture as well as in high serum concentrations intended to mimic in vivo conditions. Structure–activity relationship (SAR) analysis of common sugar analogs revealed that O-acetylated and N-azido ManNAc derivatives were more refractory against extracellular inactivation by FBS than their butanoylated counterparts consistent with in silico docking simulations of Ac₄ManNAc and Bu₄ManNAc to human carboxylesterase 1 (hCE1). By contrast, all analogs tested supported increased intracellular sialic acid production within 2 h establishing that esterase processing once the analogs are taken up by cells is not rate limiting.     

Trisomy 8 in leukemia: A GCRI experience

Trisomy of chromosome 8 is frequently reported in myeloid lineage disorders and also detected in lymphoid neoplasms as well as solid tumors suggesting its role in neoplastic progression in general. It is likely to be a disease-modulating secondary event with underlying cryptic aberrations as it has been frequently reported in addition to known abnormalities contributing to clinical heterogeneity and modifying prognosis. Here, we share our findings of trisomy 8 in leukemia patients referred for diagnostic and prognostic cytogenetic assessment. Total 60 cases of trisomy 8, as a sole anomaly or in addition to other chromosomal aberrations, were reported (January 2005-September 2008). Unstimulated bone marrow or blood samples were cultured, followed by GTG banding and karyotyping as per the ISCN 2005. Patients with +8 were chronic myeloid leukemia (CML) (36), acute myeloid leukemia (AML) (17), and acute lymphoblastic leukemia (ALL) (7). In 7 patients, trisomy 8 was the sole anomaly, whereas in 6 patients +8 was in addition to normal clone, in 47 patients, the +8 was in addition to t(9;22), t(15;17), and others, including 3 with tetrasomy 8. Only one patient showed constitutional +8. The present study will form the basis of further cumulative studies to correlate potential differential effects of various karyotypic anomalies on disease progression and survival following a therapeutic regime. To unravel the role of extra 8 chromosome, constitutional chromosomal analysis and uniparental disomy will be considered.