Akt inhibits apoptosis downstream of BID cleavage via a glucose-dependent mechanism involving mitochondrial hexokinases

The serine/threonine kinase Akt/protein kinase B inhibits apoptosis induced by a variety of stimuli, including overexpression or activation of proapoptotic Bcl-2 family members. The precise mechanisms by which Akt prevents apoptosis are not completely understood, but Akt may function to maintain mitochondrial integrity, thereby preventing cytochrome c release following an apoptotic insult. This effect may be mediated, in part, via promotion of physical and functional interactions between mitochondria and hexokinases. Here we show that growth factor deprivation induced proteolytic cleavage of the proapoptotic Bcl-2 family member BID to yield its active truncated form, tBID. Activated Akt inhibited mitochondrial cytochrome c release and apoptosis following BID cleavage. Akt also antagonized tBID-mediated BAX activation and mitochondrial BAK oligomerization, two downstream events thought to be critical for tBID-induced apoptosis. Glucose deprivation, which impaired the ability of Akt to maintain mitochondrion-hexokinase association, prevented Akt from inhibiting BID-mediated apoptosis. Interestingly, tBID independently elicited dissociation of hexokinases from mitochondria, an effect that was antagonized by activated Akt. Ectopic expression of the amino-terminal half of hexokinase II, which is catalytically active and contains the mitochondrion-binding domain, consistently antagonized tBID-induced apoptosis. These results suggest that Akt inhibits BID-mediated apoptosis downstream of BID cleavage via promotion of mitochondrial hexokinase association and antagonism of tBID-mediated BAX and BAK activation at the mitochondria.     

Carbonic anhydrase inhibitors: aliphatic N-phosphorylated sulfamates--a novel zinc-anchoring group leading to nanomolar inhibitors

A small library of phosphorylated sulfamates (N-(O-alkylsulfamoyl)-phosphoramidic acids) incorporating long aliphatic chains (C8-C16) has been synthesized and investigated for their interaction with two physiologically relevant carbonic anhydrase (CA) isozymes. These compounds behaved as very potent inhibitors of both isozymes, with inhibition constants in the range of 8.2-16.1nM against isozyme hCA I, and 5.3-11.9nM against isozyme hCA II. Activity was optimal for the n-octyl derivative (similarly with that of the corresponding unsubstituted sulfamates) and gradually decreased for the longer chain derivatives. Some of these compounds are much more effective CA inhibitors as compared to the clinically used derivatives acetazolamide, sulfanilamide or topiramate, which are used as standards for the enzymatic determinations. The phosphorylated sulfamate moiety represents a novel zinc-binding group for the design of effective CA inhibitors.     

Use of siRNAs and antisense oligonucleotides against survivin RNA to inhibit steps leading to tumor angiogenesis

The antiapoptotic protein survivin is an attractive target in cancer therapy because it is expressed differently in tumors and normal tissues and it is potentially required for cancer cells to remain viable. Given that survivin is also overexpressed in endothelial cells (ECs) of newly formed blood vessels found in tumors, its RNA targeting might compromise EC viability and interfere with tumor angiogenesis. We used two antisense strategies against survivin expression, antisense oligonucleotides (aODN) and small interfering RNA (siRNA), to study in ECs the contribution of survivin in various steps leading to tumor angiogenesis. A 21-mer phosphorothioate aODN and two siRNA oligonucleotides against survivin mRNA were designed to downregulate survivin expression. Survivin targeting caused (1) a strong growth-inhibitory effect, (2) a 4-fold increase in apoptosis, (3) an accumulation of cells in the S phase and a decrease in G2/M phase, (4) a dose-dependent inhibition of EC migration on Vitronectin, and (5) a decrease in capillary formation. Control oligonucleotides, an unrelated oligonucleotide, and one with four mismatches, had no significant effect. All these results show that survivin is a suitable target in cancer therapy because its inhibition in EC causes both a proapoptotic effect and an interruption of tumor angiogenesis. The two strategies used, classic aODN and siRNA technology, were very effective. Moreover, the latter can be used in the low nanomolar range, thus increasing the sensitivity of the treatment.     

Crossing the Red Sea: phylogeography of the hamadryas baboon, Papio hamadryas hamadryas

The hamadryas baboon (Papio hamadryas hamadryas) is found both in East Africa and western Arabia and is the only free-ranging nonhuman primate in Arabia. It has been hypothesized that hamadryas baboons colonized Arabia in the recent past and were possibly even transported there by humans. We investigated the phylogeography of hamadryas baboons by sequencing a portion of the control region of mtDNA in 107 baboons from four Saudi Arabian populations and combing these data with published data from Eritrean (African) P. h. hamadryas. Analysis grouped sequences into three distinct clades, with clade 1 found only in Arabia, clade 3 found only in Africa, but clade 2 found in both Arabian and African P. h. hamadryas and also in the olive baboon, P. h. anubis. Patterns of variation within Arabia are neither compatible with the recent colonization of Arabia, implying that baboons were not transported there by humans, nor with a northerly route of colonization of Arabia. We propose that hamadryas baboons reached Arabia via land bridges that have formed periodically during glacial maxima at the straits of Bab el Mandab in the southern Red Sea. We suggest that the genetic differentiation of Arabian from African populations suggests that Arabian populations have a higher conservation status than recognized previously.     

Modelling Si-N-limited growth of diatoms

A mechanistic model for silicon (Si) physiology is developed,interfaced with a model of nitrogen (N) physiology, which iscapable of simulating the major documented facets of Si–Nphysiology in diatoms. The model contains a cell cycle componentthat is involved in regulating the timing of the synthesis ofvalves, girdles and setae. In addition to reproducing the timingof diatom cell division within a light–dark cycle, themodel simulates the following features seen in real diatoms.Synthesis of valves only occurs during G₂ interphase and M,while the girdles and (if appropriate) setae are synthesizedduring G₁. Si stress alone results in a loss of setae, followedby a thinning of the valves in successive generations untila minimum Si cell quota is attained. After this point, the durationof G₂ increases and growth is Si limited. Concurrently, thecarbon (C) cell quota increases, offering the capability tosimulate the documented increase in sinking rates with Si stress.N stress alone results in an increase in the duration of G₁and G₂ interphases, and high Si cell quotas. From this complexmodel, which must be run for arrays of subpopulations to simulatenon-synchronous growth, a simpler model is developed. This iscapable of reproducing similar growth dynamics, although withno reference to component parts of the frustule. When alliedto a photoacclimative submodel, a prediction of the model isthat diatoms starved of Si will release increased amounts ofdissolved organic C because cell growth is halted more rapidlythan the photosystems can be degraded.     

Structure based design of nicotinamide phosphoribosyltransferase (NAMPT) inhibitors from a phenotypic screen

Nicotinamide phosphoribosyltransferase is a key metabolic enzyme that is a potential target for oncology. Utilizing publicly available crystal structures of NAMPT and in silico docking of our internal compound library, a NAMPT inhibitor, 1, obtained from a phenotypic screening effort was replaced with a more synthetically tractable scaffold. This compound then provided an excellent foundation for further optimization using crystallography driven structure based drug design. From this approach, two key motifs were identified, the (S,S) cyclopropyl carboxamide and the (S)-1-N-phenylethylamide that endowed compounds with excellent cell based potency. As exemplified by compound 27e such compounds could be useful tools to explore NAMPT biology in vivo.     

Leaf litter quality drives litter mixing effects through complementary resource use among detritivores

To comprehend the potential consequences of biodiversity loss on the leaf litter decomposition process, a better understanding of its underlying mechanisms is necessary. Here, we hypothesize that positive litter mixture effects occur via complementary resource use, when litter species complement each other in terms of resource quality for detritivores. To investigate this, monocultures and mixtures of two leaf litter species varying in quality were allowed to decompose with and without a single macro-detritivore species (the terrestrial woodlice Oniscus asellus). Resource quality of the mixture was assessed by the mean concentration, the dissimilarity in absolute and relative concentrations, and the covariance between nitrogen (N), phosphorus (P) and calcium (Ca) supply. Our results clearly show that litter mixing effects were driven by differences in their resource quality for detritivores. In particular, complementary supply of N and P was a major driver of litter mixing effects. Interestingly, litter mixing effects caused by the addition of woodlice were predominantly driven by N dissimilarity, whereas in their absence, increased P concentration was the main driver of litter mixing effects. These results show that ultimately, litter diversity effects on decomposition may be driven by complementary resource use of the whole decomposer community (i.e., microbes and macro-detritivores).     

Influence of hydraulics on the uptake of ammonium by two freshwater plants

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A strategy to determine HLA class II restriction broadly covering the DR, DP, and DQ allelic variants most commonly expressed in the general population

Classic ways to determine MHC restriction involve inhibition with locus-specific antibodies and antigen presentation assays with panels of cell lines matched or mismatched at the various loci of interest. However, these determinations are often complicated by T cell epitope degeneracy and promiscuity. We describe a selection of 46 HLA DR, DQ, and DP specificities that provide worldwide population (phenotypic) coverage of almost 90 % at each locus, and account for over 66 % of all genes at each locus. This panel afforded coverage of at least four HLA class II alleles in over 95 % of the individuals in four study populations of diverse ethnicity from the USA and South Africa. Next, a panel of single HLA class II-transfected cell lines, corresponding to these 46 allelic variants was assembled, consisting of lines previously developed and 15 novel lines generated for the present study. The novel lines were validated by assessing their HLA class II expression by FACS analysis, the in vitro peptide binding activity of HLA molecules purified from the cell lines, and their antigen presenting capacity to T cell lines of known restriction. We also show that these HLA class II-transfected cell lines can be used to rapidly and unambiguously determine HLA restriction of epitopes recognized by an individual donor in a single experiment. This panel of lines will enable high throughput determination of HLA restriction, enabling better characterization of HLA class II-restricted T cell responses and facilitating the development of HLA tetrameric staining reagents.     

Long-Term Prognostic Performance of Ki67 Rate in Early Stage,pT1-pT2, pN0, Invasive Breast Carcinoma

Background

Molecular signatures may become of use in clinical practice to assess the prognosis of breast cancers. However, although international consensus conferences sustain the use of these new markers in the near future, concerns remain about their degree of discordance and cost-effectiveness in different international settings. The present study aims to validate Ki67 as prognostic factor in a large cohort of early-stage (pT1–pT2, pN0) breast cancer patients.

Methods

456 patients treated in 1995–1996 were identified in the Institut Curie database. Ki67 (MIB1) was retrospectively assessed by immunohistochemistry for all cases. The prognostic value of this index was compared to that of histological grade (HG), Estrogen receptor (ER) and HER2 status. Distant disease free interval, loco-regional recurrence, time-lapse from first metastatic diagnosis to death were analyzed.

Results

All 456 patients were treated by lumpectomy plus axillary dissection and radiotherapy. 27 patients (5.9%) received systemic treatment. Tumors were classified as HG1 in 35%, HG2 in 42% and HG3 in 23% of cases. ER was expressed in 86% of the tumors, HER2 in 5% and 14% were triple negative. The median follow-up was 151 [5–191] months. Distant and loco-regional disease recurrences were observed in 16% and 18%, respectively. High (>20%) Ki67 rate [HR = 3 (1.8–4.8), p<10e−06] and HG3 [HR = 4.4 (2.2–8.6), p = 0.00002] were associated with an increased rate of distant relapse. In multivariate analysis, the Ki67 remained the only significant prognostic factor in the subgroups of ER positive HER2 negative [HR = 2.6 (1.5–4.6), p = 0.0006] and ER positive HER2 negative HG2 tumors [HR = 2.2 (1.01–4.8), p = 0.04].

Conclusions

We validate the prognosis value of the Ki67 rate in small size node negative breast cancer. We conclude that Ki67 is a potential cost-effective decision marker for adjuvant therapy in early-stage HG2, pT1–pT2, pN0, breast cancers.