Purine nucleotides are necessary for various biological processes related to cell proliferation. Despite their importance in DNA and RNA synthesis, cellular signaling, and energy-dependent reactions, ...the impact of changes in cellular purine levels on cell physiology remains poorly understood. Here, we find that purine depletion stimulates cell migration, despite effective reduction in cell proliferation. Blocking purine synthesis triggers a shunt of glycolytic carbon into the serine synthesis pathway, which is required for the induction of cell migration upon purine depletion. The stimulation of cell migration upon a reduction in intracellular purines required one-carbon metabolism downstream of de novo serine synthesis. Decreased purine abundance and the subsequent increase in serine synthesis triggers an epithelial-mesenchymal transition (EMT) and, in cancer models, promotes metastatic colonization. Thus, reducing the available pool of intracellular purines re-routes metabolic flux from glycolysis into de novo serine synthesis, a metabolic change that stimulates a program of cell migration.
BACKGROUND:The unfolded protein response plays versatile roles in physiology and pathophysiology. Its connection to cell growth, however, remains elusive. Here, we sought to define the role of ...unfolded protein response in the regulation of cardiomyocyte growth in the heart.
METHODS:We used both gain- and loss-of-function approaches to genetically manipulate XBP1s (spliced X-box binding protein 1), the most conserved signaling branch of the unfolded protein response, in the heart. In addition, primary cardiomyocyte culture was used to address the role of XBP1s in cell growth in a cell-autonomous manner.
RESULTS:We found that XBP1s expression is reduced in both human and rodent cardiac tissues under heart failure. Furthermore, deficiency of XBP1s leads to decompensation and exacerbation of heart failure progression under pressure overload. On the other hand, cardiac-restricted overexpression of XBP1s prevents the development of cardiac dysfunction. Mechanistically, we found that XBP1s stimulates adaptive cardiac growth through activation of the mechanistic target of rapamycin signaling, which is mediated via FKBP11 (FK506-binding protein 11), a novel transcriptional target of XBP1s. Moreover, silencing of FKBP11 significantly diminishes XBP1s-induced mechanistic target of rapamycin activation and adaptive cell growth.
CONCLUSIONS:Our results reveal a critical role of the XBP1s–FKBP11–mechanistic target of rapamycin axis in coupling of the unfolded protein response and cardiac cell growth regulation.
Phloem-feeding aphids deprive plants of assimilates, but mostly manage to avoid causing the mechanical tissue damage inflicted by chewing insects. Nevertheless, jasmonate signalling that is induced ...by infestation is important in mediating resistance to phloem feeders. Aphid attack induces the jasmonic acid signalling pathway, but very little is known about the specific impact jasmonates have on the expression of genes that respond to aphid attack.
We have evaluated the function that jasmonates have in regulating Arabidopsis thaliana responses to cabbage aphid (Brevicoryne brassicae) by conducting a large-scale transcriptional analysis of two mutants: aos, which is defective in jasmonate production, and fou2, which constitutively induces jasmonic acid biosynthesis. This analysis enabled us to determine which genes' expression patterns depend on the jasmonic acid signalling pathway. We identified more than 200 genes whose expression in non-challenged plants depended on jasmonate levels and more than 800 genes that responded differently to infestation in aos and fou2 plants than in wt. Several aphid-induced changes were compromised in the aos mutant, particularly genes connected to regulation of transcription, defence responses and redox changes. Due to jasmonate-triggered pre-activation of fou2, its transcriptional profile in non-challenged plants mimicked the induction of defence responses in wt. Additional activation of fou2 upon aphid attack was therefore limited. Insect fitness experiments revealed that the physiological consequences of fou2 mutation contributed to more effective protection against B. brassicae. However, the observed resistance of the fou2 mutant was based on antibiotic rather than feeding deterrent properties of the mutant as indicated by an analysis of aphid feeding behaviour.
Analysis of transcriptional profiles of wt, aos and fou2 plants revealed that the expression of more than 200 genes is dependent on jasmonate status, regardless of external stimuli. Moreover, the aphid-induced response of more than 800 transcripts is regulated by jasmonate signalling. Thus, in plants lacking jasmonates many of the defence-related responses induced by infestation in wt plants are impaired. Constant up-regulation of jasmonate signalling as evident in the fou2 mutant causes reduction in aphid population growth, likely as a result of antibiotic properties of fou2 plants. However, aos mutation does not seem to affect aphid performance when the density of B. brassicae populations on plants is low and aphids are free to move around.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Purine nucleotides are vital for RNA and DNA synthesis, signaling, metabolism, and energy homeostasis. To synthesize purines, cells use two principal routes: the de novo and salvage pathways. ...Traditionally, it is believed that proliferating cells predominantly rely on de novo synthesis, whereas differentiated tissues favor the salvage pathway. Unexpectedly, we find that adenine and inosine are the most effective circulating precursors for supplying purine nucleotides to tissues and tumors, while hypoxanthine is rapidly catabolized and poorly salvaged in vivo. Quantitative metabolic analysis demonstrates comparative contribution from de novo synthesis and salvage pathways in maintaining purine nucleotide pools in tumors. Notably, feeding mice nucleotides accelerates tumor growth, while inhibiting purine salvage slows down tumor progression, revealing a crucial role of the salvage pathway in tumor metabolism. These findings provide fundamental insights into how normal tissues and tumors maintain purine nucleotides and highlight the significance of purine salvage in cancer.
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•The small intestine has high de novo synthesis, while kidney shows high purine salvage•The de novo synthesis and salvage pathway contribute similarly to tumor purine pools•The purine salvage pathway plays a crucial role in promoting tumor growth•Dietary supplementation of nucleotides accelerates tumor growth
Comprehensive isotope tracing analyses reveal the contribution of de novo synthesis and salvage pathways in supplying purine nucleotides across major tissues and tumors.
The unpredictable Anthropocene poses the challenge of imagining a radically different, equitable and sustainable world. Looking 100 years ahead is not easy, and especially as millennials, it appears ...quite bleak. This paper is the outcome of a visioning exercise carried out in a 2-day workshop, attended by 33 young early career professionals under the auspices of IPBES. The process used Nature Futures Framework in an adapted visioning method from the Seeds of Good Anthropocene project. Four groups envisioned more desirable future worlds; where humanity has organised itself, the economy, politics and technology, to achieve improved nature-human well-being. The four visions had differing conceptualisations of this future. However, there were interesting commonalities in their leverage points for transformative change, including an emphasis on community, fundamentally different economic systems based on sharing and technological solutions to foster sustainability and human-nature connectedness. Debates included questioning the possibility of maintaining local biocultural diversity with increased connectivity globally and the prominence of technology for sustainability outcomes. These visions are the first step towards a wider galvanisation of youth visions for a brighter future, which is often missing in the arena where it can be taken seriously, to trigger more transformative pathways towards meeting global goals
Nicotinamide adenine dinucleotide phosphate (NADP
) is vital to produce NADPH, a principal supplier of reducing power for biosynthesis of macromolecules and protection against oxidative stress. NADPH ...exists in separate pools, in both the cytosol and mitochondria; however, the cellular functions of mitochondrial NADPH are incompletely described. Here, we find that decreasing mitochondrial NADP(H) levels through depletion of NAD kinase 2 (NADK2), an enzyme responsible for production of mitochondrial NADP
, renders cells uniquely proline auxotrophic. Cells with NADK2 deletion fail to synthesize proline, due to mitochondrial NADPH deficiency. We uncover the requirement of mitochondrial NADPH and NADK2 activity for the generation of the pyrroline-5-carboxylate metabolite intermediate as the bottleneck step in the proline biosynthesis pathway. Notably, after NADK2 deletion, proline is required to support nucleotide and protein synthesis, making proline essential for the growth and proliferation of NADK2-deficient cells. Thus, we highlight proline auxotrophy in mammalian cells and discover that mitochondrial NADPH is essential to enable proline biosynthesis.
The purpose of this study was to assess the overall results of recipients undergoing transplantation for biliary atresia (BA), according to age, surgical techniques, and transplant eras, and to ...identify the prognostic factors affecting outcome.
Between 1984 and 2000, 328 pediatric recipients with BA who underwent orthotopic liver transplantation (OLT) were reviewed. Median age at OLT was 1.5 years (range, 0.4-14.5 years). Kasai hepatoportoenterostomy (KHPE) had been previously performed in 285 (87%) children. Regarding surgical techniques, 125 (38%) children received a whole-liver graft, 128 (39%) received a reduced-size graft, 16 (5%) received a split-liver graft, and 59 (18%) received a living-related (LR) donor graft.
Overall actuarial patient survivals were 87%, 83%, and 81% at 1, 5, and 10 years, respectively. One-year patient survivals in children undergoing transplantation at the different age ranges were 85% (under 1 year), 86% (1-3 years), 83% (3-6 years), 100% (6-10 years), and 100% (beyond 10 years) (not significant). One-year patient survivals for the different transplant eras were 75% (1984-1988), 85% (1989-1992), 93% (1993-1996), and 98% (1997-2000) (P=0.0001). Multivariate analysis demonstrated that pretransplant recipient weight (P=0.004), indication for OLT (P=0.083), and age at OLT (P=0.024) predicted patient survival. The type of baseline calcineurin inhibitor (tacrolimus) and the age at OLT (beyond 6 years) were significantly associated with a better graft survival.
Best results in children undergoing transplantation beyond 6 years indicate the importance of performing a KHPE as the first therapeutic step in BA; innovative surgical techniques, particularly LR donor graft, allowed successful transplantation in infants with early failure of KHPE.
X-ray absorption spectroscopy (XAS) was utilized to gain insights into the structure and electronic properties of the reduced copper active site in NCU08746, a polysaccharide monooxygenase (PMO) from ...Neurospora crassa that activates O2 to cleave glycosidic linkages in starch. The reaction of NCU08746 likely starts with binding of O2 to the copper(I) center. However, the solution structure of the reduced active site in NCU08746 has not been properly elucidated. In this study, we prepared Cu(I)-NCU08746 in solution, which was snap-frozen to preserve the solution structure of the copper(I) active site prior to XAS analysis. Results show that the copper(I) center in Cu(I)-NCU08746 exhibits a 4-coordinate geometry, which is different from the 3-coordinate geometry observed for some other PMOs. This difference likely arises from the coordination of the active site tyrosine residue and could contribute to the difference in activity between NCU08746 and other PMOs.
Abstract only Background & significance: Heart failure affects approximately 6 million Americans, with 5-year survival of 50%, which is responsible for a huge burden on the US economy and healthcare ...system. The relevance and significance of the metabolic alteration to the pathogenesis of pressure overload-induced cardiac hypertrophy and heart failure are largely unknown. The hexosamine biosynthetic pathway (HBP) that is linked to metabolism of glucose, fatty acids and amino acids, has been implicated in the pathophysiology of heart diseases. Methods & results: Thoracic aortic constriction (TAC) was performed to induce heart failure by pressure overload in mice. At the in vitro levels, treatment of phenylephrine (PE, 50 μM) was used to induce cellular hypertrophy in neonatal rat ventricular myocytes (NRVM). Our data revealed that all the enzymes of the HBP were upregulated while induction of hypertrophy at both in vivo and in vitro levels. Consistently, the intermediate product of the HBP was elevated in heart by afterload stress, as measured by metabolomics analyses. In the transgenic mice model for Gfat1, the rate-limiting enzyme of the HBP, we found more profound cardiac hypertrophy and cardiac remodeling in response to pressure overload. The increase of O-GlcNAc was also observed. In addition, the regulation of O-GlcNAcylation by specific targeting of two enzymes of the HBP (1 mM Alloxan, an inhibitor of OGT and 10 μM PUGNAc, an inhibitor of OGA) in NRVM suggested an involvement of the mTOR signaling in the activation of O-GlcNAc levels and the hypertrophy response. Targeting of the HBP by either specific siRNA or Gfat1 inhibitor (Azaserine, 5 μM) led to decrease in cellular hypertrophic response. Conclusions: Together, our data strongly suggest that the HBP participates in cardiac hypertrophic growth and pharmacologic targeting of the HBP may represent a novel approach to ameliorate pathological remodeling.
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