Nucleolar retention of a translational C/EBPα isoform stimulates rDNA transcription and cell size

The messenger RNA of the intronless CEBPA gene is translated into distinct protein isoforms through the usage of consecutive translation initiation sites. These translational isoforms have distinct functions in the regulation of differentiation and proliferation due to the presence of different N‐terminal sequences. Here, we describe the function of an N‐terminally extended protein isoform of CCAAT enhancer‐binding protein α (C/EBPα) that is translated from an alternative non‐AUG initiation codon. We show that a basic amino‐acid motif within its N‐terminus is required for nucleolar retention and for interaction with nucleophosmin (NPM). In the nucleoli, extended‐C/EBPα occupies the ribosomal DNA (rDNA) promoter and associates with the Pol I‐specific factors u pstream‐b inding f actor 1 (UBF‐1) and SL1 to stimulate rRNA synthesis. Furthermore, during differentiation of HL‐60 cells, endogenous expression of extended‐C/EBPα is lost concomitantly with nucleolar C/EBPα immunostaining probably reflecting the reduced requirement for ribosome biogenesis in differentiated cells. Finally, overexpression of extended‐C/EBPα induces an increase in cell size. Altogether, our results suggest that control of rRNA synthesis is a novel function of C/EBPα adding to its role as key regulator of cell growth and proliferation.     

Protective Role of miR-34c in Hypoxia by Activating Autophagy through BCL2 Repression

Hypoxia leads to significant cellular stress that has diverse pathological consequences such as cardiovascular diseases and cancers. MicroRNAs (miRNAs) are one of regulators of the adaptive pathway in hypoxia. We identified a hypoxia-induced miRNA, miR-34c, that was significantly upregulated in hypoxic human umbilical cord vein endothelial cells (HUVECs) and in murine blood vessels on day 3 of hindlimb ischemia (HLI). miR-34c directly inhibited BCL2 expression, acting as a toggle switch between apoptosis and autophagy in vitro and in vivo. BCL2 repression by miR-34c activated autophagy, which was evaluated by the expression of LC3-II. Overexpression of miR-34c inhibited apoptosis in HUVEC as well as in a murine model of HLI, and increased cell viability in HUVEC. Importantly, the number of viable cells in the blood vessels following HLI was increased by miR-34c overexpression. Collectively, our findings show that miR-34c plays a protective role in hypoxia, suggesting a novel therapeutic target for hypoxic and ischemic diseases in the blood vessels.     

赤水河外来鱼类尖头(鱥)和董氏须鳅的引种溯源及生态适应性分析

历史上,赤水河流域干流及支流的鱼类物种组成中未曾出现过尖头(鱥)(Rhynchocypris oxycephalus)和董氏须鳅(Barbatula toni).但是,近年来在赤水河支流白沙河的鱼类资源调查中发现了这两个物种的分布,其来源及未来的生存可能性受到关注.本研究比较了尖头(鱥)赤水河野外种群与养殖种群形态上的...     

Synthesis of cyclooctapeptides: constraints analogues of the peptidic neurotoxin, ω‐agatoxine IVB—an experimental point of view

ω‐AGA IVB is an important lead structure when considering the design of effectors of glutamate release inducting P/Q‐type calcium channels. The best route to achieve the analogues possessing the three‐dimensional arrangement corresponding to the native binding loop was the introduction of constraint by ring formation via side chain to side chain lactamization for suitably protected Lys and Glu residues. Since tryptophane residue located at position 14 of this neuropeptide has been suggested as essential for binding, analogues in which this amino acid was replaced by aza‐tryptophane and alanine were synthesized. The synthesis was carried out on various acid‐labile resins (BARLOS chlorotrityl, Rink amide, PEG‐based or Wang resins), by Fmoc strategy. In this paper, we describe optimization of the peptide cyclization with various protecting groups, and on resin or in solution cyclization experimental parameters. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.     

Synthesis of novel acridine and bis acridine sulfonamides with effective inhibitory activity against the cytosolic carbonic anhydrase isoforms II and VII

4-Amino-N-(4-sulfamoylphenyl)benzamide was synthesized by reduction of 4-nitro-N-(4-sulfamoylphenyl)benzamide and used to synthesize novel acridine sulfonamide compounds, by a coupling reaction with cyclic-1,3-diketones and aromatic aldehydes. The new compounds were investigated as inhibitors of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1), and more precisely the cytosolic isoforms hCA I, II and VII. hCA I was inhibited in the micromolar range by the new compounds (K_Is of 0.16–9.64 μM) whereas hCA II and VII showed higher affinity for these compounds, with K_Is in the range of 15–96 nM for hCA II, and of 4–498 nM for hCA VII. The structure–activity relationships for the inhibition of these isoforms with the acridine–sulfonamides reported here were also elucidated.     

Drosophila p24 homologues eclair and baiser are necessary for the activity of the maternally expressed Tkv receptor during early embryogenesis

p24 proteins are assumed to play an important role in the transport of secreted and transmembrane proteins into membranes. However, only few cargo proteins are known that partially, but in no case completely require p24 proteins for membrane transport. Here, we show that two p24 proteins are essential for dorsoventral patterning of Drosophila melanogaster embryo. Mutations in the genes, eclair (eca) and baiser (bai), encoding two p24 proteins reduce signalling by the TGF-beta homologue, Dpp, in early embryos. This effect is strictly maternal and specific to early embryogenesis, as Dpp signalling in other contexts is not notably affected. We provide genetic evidence that in the absence of eca or bai function in the oocyte, the maternally expressed type I TGF-beta receptor Tkv is not active. We propose that during early embryogenesis eca and bai are specifically required for the activity of the maternal Tkv, while the zygotic Tkv is not affected in the mutant embryos. Mutations in either eca or bai are sufficient for the depletion of Tkv activity and no enhancement of the phenotypes was observed in embryos derived from oocytes mutant for both genes. The dependence of maternal Tkv protein on the products of p24 genes may serve as an in vivo model for studying p24 proteins.     

Effect of Electroconvulsive Shock on Mitochondrial Respiratory Chain in Rat Brain

It is well described that impairment of energy production has been implicated in the pathogenesis of a number of diseases. Although several advances have occurred over the past 20 years concerning the use and administration of electroconvulsive therapy (ECT) to minimize its side effects, little progress has been made in understanding its mechanism of action. In this work, our aim was to measure the activities of mitochondrial respiratory chain complexes II and IV and succinate dehydrogenase from rat brain after acute and chronic electroconvulsive shock (ECS). Our results showed that mitochondrial respiratory chain enzymes activities were increased after acute ECS in hippocampus, striatum and cortex of rats. Besides, we also demonstrated that complex II activity was increased after chronic ECS in cortex, while hippocampus and striatum were not affected. Succinate dehydrogenase, however, was inhibited after chronic ECS in striatum, activated in cortex and not affected in hippocampus. Finally, complex IV was not affected by chronic ECS in hippocampus, striatum and cortex. Our findings demonstrated that brain metabolism is altered by ECS.     

Porin and cytochrome oxidase containing contact sites involved in the oxidation of cytosolic NADH

Cytochrome c (cyto-c) added to isolated mitochondria promotes the oxidation of extra-mitochondrial NADH and the reduction of molecular oxygen associated to the generation of an electrochemical membrane potential available for ATP synthesis. The electron transport pathway activated by exogenous cyto-c molecules is completely distinct from the one catalyzed by the respiratory chain. Dextran sulfate (500 kDa), known to interact with porin (the voltage-dependent anion channel), other than to inhibit the release of ATP synthesized inside the mitochondria, greatly decreases the activity of exogenous NADH/cyto-c system of intact mitochondria but has no effect on the reconstituted system made of mitoplasts and external membrane preparations. The results obtained are consistent with the existence of specific contact sites containing cytochrome oxidase and porin, as components of the inner and the outer membrane respectively, involved in the oxidation of cytosolic NADH. The proposal is put forward that the bi-trans-membrane electron transport chain activated by cytosolic cyto-c becomes, in physio-pathological conditions: (i) functional in removing the excess of cytosolic NADH; (ii) essential for cell survival in the presence of an impairment of the first three respiratory complexes; and (iii) an additional source of energy at the beginning of apoptosis.     

microRNA-30c reduces plasma cholesterol in homozygous familial hypercholesterolemic and type 2 diabetic mouse models

High plasma cholesterol levels are found in several metabolic disorders and their reductions are advocated to reduce the risk of atherosclerosis. A way to lower plasma lipids is to curtail lipoprotein production; however, this is associated with steatosis. We previously showed that microRNA (miR)-30c lowers diet-induced hypercholesterolemia and atherosclerosis in C57BL/6J and Apoe^−/− mice. Here, we tested the effect of miR-30c on plasma lipids, transaminases, and hepatic lipids in different mouse models. Hepatic delivery of miR-30c to chow-fed leptin-deficient (ob/ob) and leptin receptor-deficient (db/db) hypercholesterolemic and hyperglycemic mice reduced cholesterol in total plasma and VLDL/LDL by ∼28% and ∼25%, respectively, without affecting triglyceride and glucose levels. And these mice had lower plasma transaminases and creatine kinase activities than controls. Moreover, miR-30c significantly lowered plasma cholesterol and atherosclerosis in Western diet-fed Ldlr^−/− mice with no effect on plasma triglyceride, glucose, and transaminases. In these studies, hepatic lipids were similar in control and miR-30c-injected mice. Mechanistic studies showed that miR-30c reduced hepatic microsomal triglyceride transfer protein activity and lipid synthesis. Thus miR-30c reduced plasma cholesterol in several diet-induced and diabetic hypercholesterolemic mice. We speculate that miR-30c may be beneficial in lowering plasma cholesterol in different metabolic disorders independent of the origin of hypercholesterolemia.     

Estrogen therapy and brain muscarinic receptor density in healthy females: a SPET study

Estrogen Therapy (ET) may protect against age-related cognitive decline and neuropsychiatric disorders (e.g. Alzheimer's disease). The biological basis for this putative neuroprotective effect is not fully understood, but may include modulation of cholinergic systems. Cholinergic dysfunction has been implicated in age-related memory impairment and Alzheimer's disease. However, to date no one has investigated the effect of long-term ET on brain cholinergic muscarinic receptor aging, and related this to cognitive function. We used Single Photon Emission Tomography (SPET) and (R,R)[(123)I]-I-QNB, a novel ligand with high affinity for m(1)/m(4) muscarinic receptors, to examine the effect of long-term ET and age on brain m(1)/m(4) receptors in healthy females. We included 10 younger premenopausal subjects and 22 postmenopausal women; 11 long-term ET users (all treated following surgical menopause) and 11 ET never-users (surgical menopause, n=2). Also, verbal memory and executive function was assessed in all postmenopausal subjects. Compared to young women, postmenopausal women (ET users and never-users combined) had significantly lower muscarinic receptor density in all brain regions examined. ET users also had higher muscarinic receptor density than ET never-users in all the brain regions, and this reached statistical significance in left striatum and hippocampus, lateral frontal cortex and thalamus. Moreover, in ET users, (R,R)[(123)I]-I-QNB binding in left hippocampus and temporal cortex was significantly positively correlated with plasma estradiol levels. We also found evidence for improved executive function in ET users as compared to ET never-users. However, there was no significant relationship between receptor binding and cognitive function within any of the groups. In healthy postmenopausal women use of long-term ET is associated with reduced age-related differences in muscarinic receptor binding, and this may be related to serum estradiol levels.