Major Control Point Research Articles

The sensor of the bacterial histidine kinase CpxA is a novel dimer of extracytoplasmic Per-ARNT-Sim domains

Histidine kinases are key bacterial sensors that recognize diverse environmental stimuli. While mechanisms of phosphorylation and phosphotransfer by cytoplasmic kinase domains are relatively well-characterized, the ways in which extracytoplasmic sensor domains regulate activation remain mysterious. The Cpx envelope stress response is a conserved Gram-negative two-component system which is controlled by the sensor kinase CpxA. We report the structure of the Escherichia coli CpxA sensor domain (CpxA-SD) as a globular Per-ARNT-Sim (PAS)-like fold highly similar to that of Vibrio parahaemolyticus CpxA as determined by X-ray crystallography. Because sensor kinase dimerization is important for signaling, we used AlphaFold2 to model CpxA-SD in the context of its connected transmembrane domains, which yielded a novel dimer of PAS domains possessing a distinct dimer organization compared to previously characterized sensor domains. Gain of function cpxA* alleles map to the dimer interface, and mutation of other residues in this region also leads to constitutive activation. CpxA activation can be suppressed by mutations that restore inter-monomer interactions, suggesting that inhibitory interactions between CpxA-SD monomers are the major point of control for CpxA activation and signaling. Searching through hundreds of structural homologues revealed the sensor domain of Pseudomonas aeruginosa sensor kinase PfeS as the only PAS structure in the same novel dimer orientation as CpxA, suggesting that our dimer orientation may be utilized by other extracytoplasmic PAS domains. Overall, our findings provide insight into the diversity of the organization of PAS sensory domains and how they regulate sensor kinase activation.

Translation factor eIF5a is essential for IFNγ production and cell cycle regulation in primary CD8+ T lymphocytes

Control of mRNA translation adjusts protein production rapidly and facilitates local cellular responses to environmental conditions. Traditionally initiation of translation is considered to be a major translational control point, however, control of peptide elongation is also important. Here we show that the function of the elongation factor, eIF5a, is regulated dynamically in naïve CD8+ T cells upon activation by post-translational modification, whereupon it facilitates translation of specific subsets of proteins. eIF5a is essential for long-term survival of effector CD8+ T cells and sequencing of nascent polypeptides indicates that the production of proteins which regulate proliferation and key effector functions, particularly the production of IFNγ and less acutely TNF production and cytotoxicity, is dependent on the presence of functional eIF5a. Control of translation in multiple immune cell lineages is required to co-ordinate immune responses and these data illustrate that translational elongation contributes to post-transcriptional regulons important for the control of inflammation.

Heterogeneity of Organization of Subcompartments in DSB Repair Foci.

Cells assemble compartments around DNA double-strand breaks (DSBs). The assembly of this compartment is dependent on the phosphorylation of histone H2AX, the binding of MDC1 to phosphorylated H2AX, and the assembly of downstream signaling and repair components. The decision on whether to use homologous recombination or nonhomologous end-joining repair depends on competition between 53BP1 and BRCA1. A major point of control appears to be DNA replication and associated changes in the epigenetic state. This includes dilution of histone H4 dimethylation and an increase in acetylation of lysine residues on H2A and H4 that impair 53BP1 binding. In this article, we examined more closely the spatial relationship between 53BP1 and BRCA1 within the cell cycle. We find that 53BP1 can associate with early S-phase replicated chromatin and that the relative concentration of BRCA1 in DSB-associated compartments correlates with increased BRCA1 nuclear abundance as cells progress into and through S phase. In most cases during S phase, both BRCA1 and 53BP1 are recruited to these compartments. This occurs for both IR-induced DSBs and breaks targeted to an integrated LacO array through a LacI-Fok1-mCherry fusion protein. Having established that the array system replicates this heterogeneity, we further examined the spatial relationship between DNA repair components. This enabled us to precisely locate the DNA containing the break and map other proteins relative to that DNA. We find evidence for at least three subcompartments. The damaged DNA, single-stranded DNA generated from end resection of the array, and nuclease CtIP all localized to the center of the compartment. BRCA1 and 53BP1 largely occupied discrete regions of the focus. One of BRCA1 or 53BP1 overlaps with the array, while the other is more peripherally located. The array-overlapping protein occupied a larger volume than the array, CtIP, or single-stranded DNA (ssDNA). Rad51 often occupied a much larger volume than the array itself and was sometimes observed to be depleted in the array volume where the ssDNA exclusively localizes. These results highlight the complexity of molecular compartmentalization within DSB repair compartments.

FLOWERING LOCUS T paralogs control the annual growth cycle in Populus trees

In temperate and boreal regions, perennials adapt their annual growth cycle to the change of seasons. These adaptations ensure survival in harsh environmental conditions, allowing growth at different latitudes and altitudes, and are therefore tightly regulated. Populus tree species cease growth and form terminal buds in autumn when photoperiod falls below a certain threshold.1 This is followed by establishment of dormancy and cold hardiness over the winter. At the center of the photoperiodic pathway in Populus is the gene FLOWERING LOCUS T2 (FT2), which is expressed during summer and harbors significant SNPs in its locus associated with timing of bud set.1-4 The paralogous gene FT1, on the other hand, is hyper-induced in chilling buds during winter.3,5 Even though its function is so far unknown, it has been suggested to be involved in the regulation of flowering and the release of winter dormancy.3,5 In this study, we employ CRISPR-Cas9-mediated gene editing to individually study the function of the FT-like genes in Populus trees. We show that while FT2 is required for vegetative growth during spring and summer and regulates the entry into dormancy, expression of FT1 is absolutely required for bud flush in spring. Gene expression profiling suggests that this function of FT1 is linked to the release of winter dormancy rather than to the regulation of bud flush per se. These data show how FT duplication and sub-functionalization have allowed Populus trees to regulate two completely different and major developmental control points during the yearly growth cycle.

Several nAChRs gene variants are associated with phenotypes of heroin addiction in Chinese Han population

Heroin addiction is a chronic and complex brain disease. Nicotinic acetylcholine receptors (nAChRs) have been shown as major control points in many of the neurological and physiological disorders involved in heroin addiction. In the present study, thirty-three SNPs across nine nAChR genes were selected and probed for their associations with heroin addiction phenotypes in 801 unrelated northwestern Chinese Han patients. We found that rs2565055 in CHRNA2 gene was associated with daily dose of methadone treatment, and rs2672215, rs2672216 and rs2741865 in CHRNA10 gene were associated with the duration of the transition from first use to dependence (DTFUD). Cox multivariable regression analysis revealed that rs3743075, rs6495309 in CHRNA3, rs2304297 in CHRNA6, and rs1948 in CHRNB4 were associated with sexual desire in patients with heroin addiction. These findings were further supported by the identification of a haplotype block spanning CHRNA5, CHRNA3, and CHRNB4 that is correlated with changes in sexual desire after long-term heroin use. Our findings highlight associations between polymorphisms in nAChRs genes and the phenotypes of heroin addiction in the Chinese Han population. We suggest several nAChRs subunits as potential novel targets for the treatment of heroin addiction.

RNA polymerase II clusters form in line with surface condensation on regulatory chromatin

It is essential for cells to control which genes are transcribed into RNA. In eukaryotes, two major control points are recruitment of RNA polymerase II (Pol II) into a paused state, and subsequent pause release toward transcription. Pol II recruitment and pause release occur in association with macromolecular clusters, which were proposed to be formed by a liquid–liquid phase separation mechanism. How such a phase separation mechanism relates to the interaction of Pol II with DNA during recruitment and transcription, however, remains poorly understood. Here, we use live and super‐resolution microscopy in zebrafish embryos to reveal Pol II clusters with a large variety of shapes, which can be explained by a theoretical model in which regulatory chromatin regions provide surfaces for liquid‐phase condensation at concentrations that are too low for canonical liquid–liquid phase separation. Model simulations and chemical perturbation experiments indicate that recruited Pol II contributes to the formation of these surface‐associated condensates, whereas elongating Pol II is excluded from these condensates and thereby drives their unfolding.

Substrate binding modes of purine and pyrimidine nucleotides to human ecto-5\u2032-nucleotidase (CD73) and inhibition by their bisphosphonic acid derivatives

Human ecto-5-nucleotidase (CD73) is involved in purinergic signalling, which influences a diverse range of biological processes. CD73 hydrolyses AMP and is the major control point for the levels of extracellular adenosine. Inhibitors of CD73 thus block the immunosuppressive action of adenosine, a promising approach for cancer immunotherapy. Interestingly, ADP and ATP are competitive inhibitors of CD73, with the most potent small-molecule inhibitors to date being non-hydrolysable ADP analogues. While AMP is the major substrate of the enzyme, CD73 has been reported to hydrolyse other 5′-nucleoside monophosphates. Based on a fragment screening campaign at the BESSY II synchrotron, we present the binding modes of various deoxyribo- and ribonucleoside monophosphates and of four additional fragments binding to the nucleoside binding site of the open form of the enzyme. Kinetic analysis of monophosphate hydrolysis shows that ribonucleotide substrates are favoured over their deoxyribose equivalents with AMP being the best substrate. We characterised the initial step of AMP hydrolysis, the binding mode of AMP to the open conformation of CD73 and compared that to other monophosphate substrates. In addition, the inhibitory activity of various bisphosphonic acid derivatives of nucleoside diphosphates was determined. Although AMPCP remains the most potent inhibitor, replacement of the adenine base with other purines or with pyrimidines increases the Ki value only between twofold and sixfold. On the other hand, these nucleobases offer new opportunities to attach substituents for improved pharmacological properties.

13C-Labeled Diethyl Ketoglutarate Derivatives as Hyperpolarized Probes of 2-Ketoglutarate Dehydrogenase Activity.

The TCA cycle is a central metabolic pathway for energy production and biosynthesis. A major control point of metabolic flux through the cycle is the decarboxylation of 2-ketoglutarate by the TCA cycle enzyme 2-ketoglutarate dehydrogenase (2-KGDH). In this project, we developed 13C labeled 2-ketoglutarate derivatives to monitor 2-KGDH activity in vivo. 13C NMR analysis of liver extracts revealed that uniformly 13C labeled 2-ketogutarate, in its cell permeable ester form, was rapidly taken up and hydrolyzed in liver and underwent extensive metabolism to produce labeled glutamate, succinate, lactate and other metabolites. Diethyl [1,2-13C2]-2-ketoglutarate was successfully polarized by dynamic nuclear polarization and within seconds after injection into rats, the probe produced hyperpolarized [13C]bicarbonate in the liver reflecting flux through the TCA cycle. These experiments demonstrate that this tracer offers the possibility of directly monitoring flux through 2-KGDH in vivo.

A BRD4-mediated elongation control point primes transcribing RNA polymerase II for 3′-processing and termination

Transcription elongation has emerged as a regulatory hub in gene expression of metazoans. A major control point occurs during early elongation before RNA polymerase II (Pol II) is released into productive elongation. Prior research has linked BRD4 with transcription elongation. Here, we use rapid BET protein and BRD4-selective degradation along with quantitative genome-wide approaches to investigate direct functions of BRD4 in Pol II transcription regulation. Notably, as an immediate consequence of acute BRD4 loss, promoter-proximal pause release is impaired, and transcriptionally engaged Pol II past this checkpoint undergoes readthrough transcription. An integrated proteome-wide analysis uncovers elongation and 3'-RNA processing factors as core BRD4 interactors. BRD4 ablation disrupts the recruitment of general 3'-RNA processing factors at the 5'-control region, which correlates with RNA cleavage and termination defects. These studies, performed in human cells, reveal a BRD4-mediated checkpoint and begin to establish a molecular link between 5'-elongation control and 3'-RNA processing.

Cerebral and myocardial mitochondrial injury differ in a rat model of cardiac arrest and cardiopulmonary resuscitation

Brain mitochondria are more sensitive to global ischemia compared to heart mitochondria. Complex I in the electron transport chain (ETC) is sensitive to ischemic injury and is a major control point of the rate of ADP stimulated oxygen consumption. The purpose of this study was to explore whether changes in cerebral and myocardial mitochondria differ after cardiac arrest. Animals were randomized into 4 groups (n = 6): 1) Sham 2) VF 3) VF+CPR 4) ROSC 1hr. Ventricular Fibrillation (VF) was induced through a guide wire advanced from the right jugular vein into the ventricle and untreated for 8 min. Resuscitation was attempted with a 4J defibrillation after 8 min of cardiopulmonary resuscitation (CPR). Brain mitochondria and cardiac mitochondrial subpopulations were isolated. Calcium retention capacity was measured to assess susceptibility to mitochondrial permeability transition pore opening. ADP stimulated oxygen consumption and ETC activity assays were performed. Brain mitochondria are far more sensitive to injury during cardiac arrest and resuscitation compared to cardiac mitochondria. Complex I is highly sensitive to injury in brain mitochondria. With markedly decreased calcium retention capacity, mitochondria contribute to cerebral reperfusion injury. Therapeutic preservation of cerebral mitochondrial activity and mitochondrial function during cardiac arrest may improve post-resuscitation neurologic function.

Smoothened inhibition leads to decreased cell proliferation and suppressed tissue fibrosis in the development of benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a common disease in aging males. It has been proven that the Hedgehog (HH) is implied as an effective and fundamental regulatory growth factor signal for organogenesis, homeostasis, and regeneration. Smoothened (SMO), as the major control point of HH signals, activates aberrantly in most human solid tumors. However, the specific function of SMO and its downstream glioma-associated oncogene (GLI) family in BPH has not been well understood. Here, we first revealed that the SMO cascade was upregulated in BPH tissues and was localized in both the stromal and the epithelium compartments of human prostate tissues. Cyclopamine, as a specific SMO inhibitor, was incubated with BPH-1 and WPMY-1, and intraperitoneally injected into a BPH rat model established by castration with testosterone supplementation. SMO inhibition could induce cell apoptosis, cell cycle arrest at the G0/G1 phase, and a reduction of tissue fibrosis markers, both in vitro and in vivo. Finally, a tissue microarray, containing 104 BPH specimens, was constructed to analyze the correlations between the expression of SMO cascade and clinical parameters. The GLI2 was correlated positively with nocturia and negatively with fPSA. The GLI3 was in a positive relationship with International Prostate Symptom Score and nocturia. In conclusion, our study suggested that SMO cascade could play important roles in the development of BPH and it might be rediscovered as a promising therapeutic target for BPH.

TRPM3 expression and control of glutamate release from primary vagal afferent neurons

Vagal afferent fibers contact neurons in the nucleus of the solitary tract (NTS) and release glutamate via three distinct release pathways: synchronous, asynchronous, and spontaneous. The presence of TRPV1 in vagal afferents is predictive of activity-dependent asynchronous glutamate release along with temperature-sensitive spontaneous vesicle fusion. However, pharmacological blockade or genetic deletion of TRPV1 does not eliminate the asynchronous profile and only attenuates the temperature-dependent spontaneous release at high temperatures (>40°C), indicating additional temperature-sensitive calcium conductance(s) contributing to these release pathways. The transient receptor potential cation channel melastatin subtype 3 (TRPM3) is a calcium-selective channel that functions as a thermosensor (30-37°C) in somatic primary afferent neurons. We predict that TRPM3 is expressed in vagal afferent neurons and contributes to asynchronous and spontaneous glutamate release pathways. We investigated these hypotheses via measurements on cultured nodose neurons and in brainstem slice preparations containing vagal afferent to NTS synaptic contacts. We found histological and genetic evidence that TRPM3 is highly expressed in vagal afferent neurons. The TRPM3-selective agonist, pregnenolone sulfate, rapidly and reversibly activated the majority (∼70%) of nodose neurons; most of which also contained TRPV1. We confirmed the role of TRPM3 with pharmacological blockade and genetic deletion. In the brain, TRPM3 signaling strongly controlled both basal and temperature-driven spontaneous glutamate release. Surprisingly, genetic deletion of TRPM3 did not alter synchronous or asynchronous glutamate release. These results provide convergent evidence that vagal afferents express functional TRPM3 that serves as an additional temperature-sensitive calcium conductance involved in controlling spontaneous glutamate release onto neurons in the NTS.NEW & NOTEWORTHY Vagal afferent signaling coordinates autonomic reflex function and informs associated behaviors. Thermosensitive transient receptor potential (TRP) channels detect temperature and nociceptive stimuli in somatosensory afferent neurons, however their role in vagal signaling remains less well understood. We report that the TRPM3 ion channel provides a major thermosensitive point of control over vagal signaling and synaptic transmission. We conclude that TRPM3 translates physiological changes in temperature to neurophysiological outputs and can serve as a cellular integrator in vagal afferent signaling.

The potassium channel subunit Kvβ1 serves as a major control point for synaptic facilitation

Analysis of the presynaptic action potential's (APsyn) role in synaptic facilitation in hippocampal pyramidal neurons has been difficult due to size limitations of axons. We overcame these size barriers by combining high-resolution optical recordings of membrane potential, exocytosis, and Ca2+ in cultured hippocampal neurons. These recordings revealed a critical and selective role for Kv1 channel inactivation in synaptic facilitation of excitatory hippocampal neurons. Presynaptic Kv1 channel inactivation was mediated by the Kvβ1 subunit and had a surprisingly rapid onset that was readily apparent even in brief physiological stimulation paradigms including paired-pulse stimulation. Genetic depletion of Kvβ1 blocked all broadening of the APsyn during high-frequency stimulation and eliminated synaptic facilitation without altering the initial probability of vesicle release. Thus, using all quantitative optical measurements of presynaptic physiology, we reveal a critical role for presynaptic Kv channels in synaptic facilitation at presynaptic terminals of the hippocampus upstream of the exocytic machinery.

In vitro Analysis of O-Antigen-Specific Bacteriophage P22 Inactivation by Salmonella Outer Membrane Vesicles.

Bacteriophages use a large number of different bacterial cell envelope structures as receptors for surface attachment. As a consequence, bacterial surfaces represent a major control point for the defense against phage attack. One strategy for phage population control is the production of outer membrane vesicles (OMVs). In Gram-negative host bacteria, O-antigen-specific bacteriophages address lipopolysaccharide (LPS) to initiate infection, thus relying on an essential outer membrane glycan building block as receptor that is constantly present also in OMVs. In this work, we have analyzed interactions of Salmonella (S.) bacteriophage P22 with OMVs. For this, we isolated OMVs that were formed in large amounts during mechanical cell lysis of the P22 S. Typhimurium host. In vitro, these OMVs could efficiently reduce the number of infective phage particles. Fluorescence spectroscopy showed that upon interaction with OMVs, bacteriophage P22 released its DNA into the vesicle lumen. However, only about one third of the phage P22 particles actively ejected their genome. For the larger part, no genome release was observed, albeit the majority of phages in the system had lost infectivity towards their host. With OMVs, P22 ejected its DNA more rapidly and could release more DNA against elevated osmotic pressures compared to DNA release triggered with protein-free LPS aggregates. This emphasizes that OMV composition is a key feature for the regulation of infective bacteriophage particles in the system.

An Essential Membrane Protein Modulates the Proteolysis of LpxC to Control Lipopolysaccharide Synthesis in Escherichia coli.

Gram-negative bacteria are surrounded by a complex cell envelope that includes two membranes. The outer membrane prevents many drugs from entering these cells and is thus a major determinant of their intrinsic antibiotic resistance. This barrier function is imparted by the asymmetric architecture of the membrane with lipopolysaccharide (LPS) in the outer leaflet and phospholipids in the inner leaflet. The LPS and phospholipid synthesis pathways share an intermediate. Proper membrane biogenesis therefore requires that the flux through each pathway be balanced. In Escherichia coli, a major control point in establishing this balance is the committed step of LPS synthesis mediated by LpxC. Levels of this enzyme are controlled through its degradation by the inner membrane protease FtsH and its presumed adapter protein LapB (YciM). How turnover of LpxC is controlled has remained unclear for many years. Here, we demonstrate that the essential protein of unknown function YejM (PbgA) participates in this regulatory pathway. Suppressors of YejM essentiality were identified in lpxC and lapB, and LpxC overproduction was shown to be sufficient to allow survival of ΔyejM mutants. Furthermore, the stability of LpxC was shown to be reduced in cells lacking YejM, and genetic and physical interactions between LapB and YejM were detected. Taken together, our results are consistent with a model in which YejM directly modulates LpxC turnover by FtsH-LapB to regulate LPS synthesis and maintain membrane homeostasis.IMPORTANCE The outer membrane is a major determinant of the intrinsic antibiotic resistance of Gram-negative bacteria. It is composed of both lipopolysaccharide (LPS) and phospholipid, and the synthesis of these lipid species must be balanced for the membrane to maintain its barrier function in blocking drug entry. In this study, we identified an essential protein of unknown function as a key new factor in modulating LPS synthesis in the model bacterium Escherichia coli Our results provide novel insight into how this organism and most likely other Gram-negative bacteria maintain membrane homeostasis and their intrinsic resistance to antibiotics.

Survival Pattern and Toxin Production of Pathogens in Spiced and Non Spiced Fried Rice

Aims: There is no data regarding the survival rate of pathogens in party foods held at different temperature and time interval in Nigeria. Hence, the need to study the survival rate of selected food borne pathogens in Fried rice (spiced and non – spiced) served at parties, monitor toxin production and the rate at which it is produced with respect to time and holding temperature as well as determine the effect of spices on the survival of food pathogens.
 Place and Duration of Study: Lagelu and Ibadan North Local Government Authority Area of Ibadan, Oyo State, Nigeria, between May 2017 and September 2017.
 Methodology: We obtained 10 fried rice samples (5 spiced and 5 non- spiced) from different parties inside sterile food warmers and transferred to the Food Microbiology Laboratory. Pathogens inoculated were obtained from the culture collection unit of the Food Microbiology laboratory and they were Bacillus cereus, Staphylococcus aureus, Salmonella typhi and Escherichia coli. Inoculum size of the pathogens was determined prior to inoculation. Initial temperature of the fried rice sample was taken and after inoculation, samples were taken at an interval of 2 hours to determine the survival rate of the pathogens. Brine Shrimp Lethality (BSL) assay was used to determine the level of toxin produced.
 Results: The microbial load of all pathogens inoculated increased from its initial size as the holding temperature reduces and holding time increases. For E. coli, there was an increase from 5.3 log10CFU/g to 9.3 log10CFU/g and 8.3 log10CFU/g in non–spiced fried rice and spiced fried rice, respectively, initial load for S. typhi also increase from 4.1 log10CFU/g to 9.1 and 8.4, for B. cereus and S. aureus there was an increase form 6.3 log10CFU/g to 9.0 and 8.4 for non-spiced and spiced rice respectively. Toxicity test shows that the lethal dose was high at 8 hours (LC50:1.5) which connotes that the toxicity was high at this holding time.
 Conclusion: Holding cooked foods at ambient temperature for 6 h or longer without appropriate reheating constitute a major critical control point for party food. Keeping foods at the right temperatures is an essential food safety practice. Adequate knowledge and application of this by caterers will reduce the rate of food borne illness in the country.

Codon and amino acid content are associated with mRNA stability in mammalian cells.

Messenger RNA (mRNA) degradation plays a critical role in regulating transcript levels in the cell and is a major control point for modulating gene expression. In yeast and other model organisms, codon identity is a powerful determinant of transcript stability, contributing broadly to impact half-lives. General principles governing mRNA stability are poorly understood in mammalian systems. Importantly, however, the degradation machinery is highly conserved, thus it seems logical that mammalian transcript half-lives would also be strongly influenced by coding determinants. Herein we characterize the contribution of coding sequence towards mRNA decay in human and Chinese Hamster Ovary cells. In agreement with previous studies, we observed that synonymous codon usage impacts mRNA stability in mammalian cells. Surprisingly, however, we also observe that the amino acid content of a gene is an additional determinant correlating with transcript stability. The impact of codon and amino acid identity on mRNA decay appears to be associated with underlying tRNA and intracellular amino acid concentrations. Accordingly, genes of similar physiological function appear to coordinate their mRNA stabilities in part through codon and amino acid content. Together, these results raise the possibility that intracellular tRNA and amino acid levels interplay to mediate coupling between translational elongation and mRNA degradation rate in mammals.

S112 MLL FUSIONS AFFECT SPLICING TO INDUCE EXPLOITABLE METABOLIC DEPENDENCIES

Background:MLL fusions are aberrant transcription factors that induce highly aggressive and hard‐to‐treat leukemia with dismal prognosis. A better understanding of leukemia specific properties may reveal potential therapeutic intervention points.Aims:Known direct downstream targets of MLL‐ENL were scored for their importance for leukemic cell survival and genes with a positive readout were further investigated for their targeting potential.Methods:A shRNA screen interrogating known MLL‐ENL target genes identified the splice‐modulator PTBP1 (polypyrimidin tract binding protein 1) as rate limiting for proliferation of MLL‐ENL transformed murine cells and also in a human patient cell line.Results:Reduction of PTBP1 slowed down cell cycle without inducing apoptosis and it reduced the competitive fitness of knock‐down cells compared to controls. This was accompanied by a conspicuous phenotype characterized by reduced medium acidification during culture. Examination of the splicing pattern of PKM transcripts (pyruvate kinase muscle‐type), a known PTBP1 splicing‐target, revealed a shift towards the PKM1 isoform upon PTBP1 ablation. PKM1/PKM2 differ in the utilization of an alternate exon and the ratio of the isoforms is one of the major control points switching from anabolic (PKM2 high) to catabolic (PKM1 high) metabolism. Mechanistically PKM2 restricts the outflow of glycolytic products into oxidative phosphorylation enabling the provision of proliferating cells with necessary anabolic intermediates. PKM2 fosters glycolysis at the expense of oxidative phosphorylation thus reducing energy yields obtained from glucose (Warburg effect). As a consequence cells increase glucose uptake and recycle reduction equivalents through production of lactate. PTBP1 knock‐down reverted this phenotype, reduced glucose consumption and lowered lactate production compared to controls. Because MLL fusions obviously hardwire cells into an anabolic‐proliferative state that requires large amounts of building blocks we tested the effect of starvation mimicking drugs (SMD) affecting glucose utilization, amino acid synthesis and energy production on MLL transformed and on primary hematopoietic precursors (Kit+ fraction of bone marrow). Whereas the immediate impact of SMDs on highly proliferative normal and MLL‐ENL transformed cells was comparable, the long term effects after an intermittent treatment were dramatically different. In contrast to their normal counterpart MLL‐ENL transformed cells lost a significant portion of their colony forming potential upon treatment indicating substantial damage suffered during episodes of starvation. On a molecular level this was accompanied by drastically higher ROS (reactive oxygen species) and an altered p53 response in MLL transformed cells.Summary/Conclusion:The feasibility to exploit a differential sensitivity towards selective starvation for therapeutic purposes is currently explored and options for a possible translation into a clinically applicable strategy will be discussed.

β-Carotene in the human body: metabolic bioactivation pathways - from digestion to tissue distribution and excretion.

β-Carotene intake and tissue/blood concentrations have been associated with reduced incidence of several chronic diseases. Further bioactive carotenoid-metabolites can modulate the expression of specific genes mainly via the nuclear hormone receptors: retinoic acid receptor- and retinoid X receptor-mediated signalling. To better understand the metabolic conversion of β-carotene, inter-individual differences regarding β-carotene bioavailability and bioactivity are key steps that determine its further metabolism and bioactivation and mediated signalling. Major carotenoid metabolites, the retinoids, can be stored as esters or further oxidised and excreted via phase 2 metabolism pathways. In this review, we aim to highlight the major critical control points that determine the fate of β-carotene in the human body, with a special emphasis on β-carotene oxygenase 1. The hypothesis that higher dietary β-carotene intake and serum level results in higher β-carotene-mediated signalling is partly questioned. Alternative autoregulatory mechanisms in β-carotene / retinoid-mediated signalling are highlighted to better predict and optimise nutritional strategies involving β-carotene-related health beneficial mediated effects.

Quantification of urban water-carbon nexus using disaggregated input-output model: A case study in Beijing (China)

The range and complexity of interdependencies between water and carbon emissions, including synergies and trade-offs, are greatest in cities. Therefore, the investigation of urban water-carbon nexus is becoming vital for the urban sustainable development. Input-Output (IO) model is an effective tool to evaluate the direct and indirect environmental effects. However, the accurate quantification on urban water-carbon nexus is seriously constrained by the highly-aggregated sector classification in urban IO models, hindering the implement of specific urban policies. Thus, this study developed a Water Carbon-IO-Life Cycle Assessment (WC-IO-LCA) model based on a modified IO approach that disaggregates the construction sector into 12 subsectors according to different building types in cities. It aims to analyze and identify the key nodes and routes of urban water-carbon nexus in Beijing's economic system in 2010. Our results demonstrate that Electricity sector is the direct water-carbon nexus node and Construction sector is the high-intensive embodied water-carbon nexus node in Beijing. Of which, nearly 64% of embodied water and 83% of embodied carbon are derived from the source sectors in the upstream of the production supply chains for Construction sector. The culture sports and entertainment buildings presented the largest embodied water-carbon intensity, which is identified as the major control point in Construction sector.