Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Key pathway”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55Linked to original sources
PubMed2003

A novel polygalacturonic acid bioflocculant REA-11 produced by Corynebacterium glutamicum: a proposed biosynthetic pathway and experimental confirmation.

Corynebacterium glutamicum CCTCC M201005 produces a novel polygalacturonic acid bioflocculant, REA-11, consisting of galacturonic acid as the main structural unit. A biosynthetic pathway of REA-11 in C. glutamicum CCTCC M201005 was proposed. Evidence for the biosynthetic pathway was provided by: (1) analyzing the response upon addition of UDP-glucose to the culture medium; (2) detecting the presence of several key intermediates in the pathway; and (3) correlating the activities of several key enzymes involved in the pathway with the yields of polygalacturonic acid. The production of polygalacturonic acid was improved by 24%, while the activities of UDP-galactose epimerase and UDP-galactose dehydrogenase were improved by 200% and 50%, respectively, upon addition of 100 microM UDP-glucose. In addition, the key intermediates in the proposed biosynthetic pathway, such as UDP-glucose, UDP-galactose, and UDP-glucuronic acid, were detected in cell-free extracts. Furthermore, the activities of UDP-glucose pyrophosphorylase (R2=0.97), UDP-galactose epimerase (R2=0.75) and UDP-galactose dehydrogenase (R2=0.89) were well correlated with the yields of polygalacturonic acid when different sugars were used as sole carbon sources. Therefore, the biosynthetic pathway of REA-11 in C. glutamicum CCTCC M201005 starts from phosphate-1-glucose, which was then converted to UDP-glucose by UDP-pyrophosphorylase. Predominantly, the UDP-glucose was converted to UDP-galactose by UDP-galactose epimerase; the latter was further converted to UDP-galacturonic acid by UDP-galactose dehydrogenase, which was presumably polymerized to polygalacturonic acid bioflocculant REA-11 by an unknown glucosyltransferase and a polymerase.

Corynebacterium↗
PubMed2001

Key role of Shc signaling in the transforming pathway triggered by Ret/ptc2 oncoprotein.

The RET/PTC oncogenes, generated by chromosomal rearrangements in papillary thyroid carcinomas, are constitutively activated versions of protoRET, a gene encoding two protein isoforms of a transmembrane tyrosine kinase receptor. By using Ret/ptc2 short isoform (iso9), we have previously demonstrated that Tyr586 (Tyr1062 of protoRet) is the docking site for both the PTB and the SH2 domains of Shc. To determine the relevance of this interaction for the transforming activity of Ret/ptc oncogenes, we have generated and characterized novel Ret/ptc mutants unable to activate Shc: Ret/ptc2 long isoform (iso51)-Y586F and both isoforms of Ret/ptc2-N583A. These mutants neither activate Shc nor transform NIH3T3 cells. Since Tyr1062 shows features of a multifunctional docking site, we have used a Shc mutant (Shc Y317F) to directly assess Shc role. We have demonstrated that in our cell system Shc Y317F behaves like a dominant interfering mutant on the activation of the Grb2-Sos pathway by endogenous Shc triggered by Ret/ptc2. A strong reduction of the transforming activity of Ret/ptc2 in presence of this mutant was also demonstrated. Our data suggest that Shc activation play a key role in the transforming pathways triggered by Ret/ptc oncoproteins. Moreover, we have shown that coexpression of the Shc-Y317F mutant with Ret/ptc2 specifically causes apoptosis, and that the surviving cells lose the long-term expression of one of the two genes.

3T3 Cells↗
PubMed2005

Polymerase chain reaction for identification of aldoxime dehydratase in aldoxime- or nitrile-degrading microorganisms.

We developed a molecular screening procedure using Southern hybridization and polymerase chain reaction (PCR) to identify aldoxime dehydratase (Oxd) encoding genes (oxds) among 14 aldoxime- or nitrile-degrading microorganisms. When an oxd gene of Rhodococcus erythropolis N-771 was used as a probe, positive hybridization signals were seen with the chromosomal DNA of eight strains, suggesting that these strains have similar oxd genes to R. erythoropolis N-771. By analyzing the PCR-amplified fragments with degenerate consensus primers, the occurrence of homologous Oxd coexisting with Fe-containing NHase in the active eight strains was demonstrated coinciding with the results of Southern hybridization. Whole length of oxd gene was cloned as an example from one of the positive strains, Pseudomonas sp. K-9, sequenced, and expressed in E. coli. Analysis of the primary structure of the protein (OxdK) encoded by the oxd gene of Pseudomonas sp. K-9 led to identify an Oxd having a new primary structure. Thus, the PCR-based analysis of oxd gene is a useful tool to detect and analyze the "aldoxime-nitrile pathway" in nature, since Oxd is the key enzyme for the pathway.

Amino Acid Sequence↗
PubMed2001

Triclosan offers protection against blood stages of malaria by inhibiting enoyl-ACP reductase of Plasmodium falciparum.

The antimicrobial biocide triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol] potently inhibits the growth of Plasmodium falciparum in vitro and, in a mouse model, Plasmodium berghei in vivo. Inhibition of [14C]acetate and [14C]malonyl-CoA incorporation into fatty acids in vivo and in vitro, respectively, by triclosan implicate FabI as its target. Here we demonstrate that the enoyl-ACP reductase purified from P. falciparum is triclosan sensitive. Also, we present the evidence for the existence of FabI gene in P. falciparum. We establish the existence of the de novo fatty acid biosynthetic pathway in this parasite, and identify a key enzyme of this pathway for the development of new antimalarials.

Amino Acid Sequence↗
PubMed2000

Functional analysis of oxidative stress-activated mitogen-activated protein kinase cascade in plants.

Despite the recognition of H(2)O(2) as a central signaling molecule in stress and wounding responses, pathogen defense, and regulation of cell cycle and cell death, little is known about how the H(2)O(2) signal is perceived and transduced in plant cells. We report here that H(2)O(2) is a potent activator of mitogen-activated protein kinases (MAPKs) in Arabidopsis leaf cells. Using epitope tagging and a protoplast transient expression assay, we show that H(2)O(2) can activate a specific Arabidopsis mitogen-activated protein kinase kinase kinase, ANP1, which initiates a phosphorylation cascade involving two stress MAPKs, AtMPK3 and AtMPK6. Constitutively active ANP1 mimics the H(2)O(2) effect and initiates the MAPK cascade that induces specific stress-responsive genes, but it blocks the action of auxin, a plant mitogen and growth hormone. The latter observation provides a molecular link between oxidative stress and auxin signal transduction. Finally, we show that transgenic tobacco plants that express a constitutively active tobacco ANP1 orthologue, NPK1, display enhanced tolerance to multiple environmental stress conditions without activating previously described drought, cold, and abscisic acid signaling pathways. Thus, manipulation of key regulators of an oxidative stress signaling pathway, such as ANP1/NPK1, provides a strategy for engineering multiple stress tolerance that may greatly benefit agriculture.

Arabidopsis↗
PubMed2001

Analysis of repair and PCNA complex formation induced by ionizing radiation in human fibroblast cell lines.

Proliferating cell nuclear antigen (PCNA), an auxiliary factor for DNA polymerase delta and epsilon, is involved in both DNA replication and repair. Previous studies in vitro have demonstrated the requirement of PCNA in the resynthesis step of nucleotide excision repair (NER) and base excision repair (BER). Using a native chromatin template isolated under near physiological conditions, we have analysed the involvement of PCNA in the BER pathway in different NER defective human cell lines. The repair sites and PCNA were visualized by indirect immunolabelling followed by fluorescence microscopy. The results indicate that exposure to X-rays triggers the induction of PCNA in all the three human fibroblast cell lines studied, namely normal, xeroderma pigmentosum group A (XP-A) and Cockayne syndrome group B (CS-B). In all the cell lines, induction of PCNA and repair patches occurred in a dose- and time-dependent fashion. Induction of repair patches in NER-deficient XP-A cells suggests that the X-ray-induced lesions are largely repaired via the BER pathway involving PCNA as one of the key components of this pathway. X-ray-induced repair synthesis was greatly inhibited by treatment of cells with DNA polymerase inhibitors aphidicolin and cytosine arabinoside. Interestingly, inhibition of repair resynthesis did not affect the intensity of PCNA staining in X-irradiated cells indicating that the PCNA may be required for the BER pathway at a step preceding the resynthesis step.

Cell Line↗
PubMed2001

Molecular pathways involved in response to ionizing radiation of ID-8 mouse ovarian cancer cells expressing exogenous full-length Brca1 or truncated Brca1 mutant.

BRCA1 germline mutations have been linked to the development of hereditary breast and ovarian cancers. Recent studies suggest that BRCA1 may function in the regulation of basic cellular processes, including gene transcription, and sensing and/or repair of DNA damage. To further delineate the BRCA1 upstream and downstream steps involved in its role in the cellular response to ionizing radiation, we compared the effects of expression of an exogenous full-length Brca1 with those of a truncated Brca1 mutant in the ID-8 mouse ovarian cancer cell line after irradiation. We found that expression of both full-length and truncated Brca1 increased resistance to ionizing radiation. Expression of truncated, but not full-length, Brca1 then allowed us to identify new potential downstream targets of mutated BRCA1 like MAPK/ERK pathway members and also key genes involved in mutated BRCA1 signaling pathway response to ionizing radiation such as p53 and p21WAF1/CIP1. We therefore established an in vitro mouse model for studying the molecular effects of human BRCA1 germline mutations.

Animals↗
PubMedDate not supplied

[Role of the vagus nerves in regulating the activity of the pentosephosphate carbohydrate metabolic pathway in the thymus and mesenteric lymph nodes].

Activity of key enzymes of pentosephosphate pathway glucose-6-phosphate dehydrogenase (G6PD) and transketolase was similar in extracts of thymus and mesenteric lymphatic ganglia. Within four weeks after dissection of vagus nerve at the level of thyroid gland the specific activity of G6PD and the total activity of the enzymes metabolizing ribose-5-phosphate were not altered in the tissue studied. The transketolase activity was inhibited in thymus tissue and lymphoid cells after right-side vagotomy. The pH-dependence of the transketolase reaction was studied in thymus extracts. After vagotomy the enzymatic activity was lower at all the pH values as compared with controls; the enzyme optimum activity was found at pH 7.5-7.8.

Animals↗
PubMedDate not supplied

[Regulation of the dopamine D2 receptor gene and the early genes in the CNS by neuroleptics].

The interaction of a ligand with its cognate receptor not only activates signal transduction pathways but also determines adaptive responses affecting key elements in these pathways, in particular the cell surface receptor. Such is the case for G protein-linked receptors, the expression and functional status of which are highly regulated. The regulatory mechanisms involved can be divided according to two distinct time frames, acute and chronic. In the short-term, posttranslational mechanisms alter the functional status of the elements without changing steady-state levels or gene expression. Protein phosphorylation plays a prominent role in these acute adaptive responses. Thus agonists promote phosphorylation and the desensitization of several G protein-linked receptors. And we have shown in the case of the dopamine D2 receptor that protein kinase C modulates receptor coupling to its G-protein. Longer-term regulation involves transcriptional (gene expression), posttranslational (mRNA stability), and posttranslational (protein phosphorylation) regulation of the turnover of the elements in the information transduction pathway. In the case of G protein-linked receptors, long-term regulation is often reflected in changes in steady-state levels of mRNA (which can be quantified by techniques such as northern blot analysis, solution hybridization or in-situ hybridization). For dopamine D2 receptors, prolonged administration of neuroleptic drugs induces an up-regulation of receptor mRNA in various brain regions, probably through an increase in gene transcription. Receptor-transduced extracellular stimuli are converted into long-term changes in gene expression through specific nuclear transcription factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Why is DNA damage signaling so complicated? Chaos and molecular signaling.

Molecular signaling in eukaryotic cells is accomplished by complex and redundant pathways converging on key molecules that are allosterically controlled by a limited number of signaling proteins. The p53-signaling pathway is an example of a complicated sequence of signals produced in response to DNA damage. This pattern of signaling may arise from chance occurrences at the origin of life and the necessities imposed on a nanomolar system. From this viewpoint, chaos theory may explain the origin, complexity, and convergence of these pathways.

Animals↗
PubMedDate not supplied

Melatonin synthesis pathway: circadian regulation of the genes encoding the key enzymes in the chicken pineal gland and retina.

The mRNAs encoding three enzymes of the melatonin synthesis pathway (tryptophan hydroxylase (TPH), arylalkylamine-N-acetyltransferase (AANAT) and hydroxyindole-O-methyl-transferase (HIOMT)) are expressed with a day/night rhythm in the chicken pineal gland and retina. TPH and AANAT mRNA levels reach their peak at night. HIOMT mRNA levels peak at night in the retina, but during the day in the pineal gland. In this tissue, the rhythm of TPH, AANAT and HIOMT mRNA levels persisted in constant darkness (DD), both in vivo and in vitro, indicating that the three genes are controlled by the circadian oscillator of the chicken pineal. In the retina, the rhythms of TPH and AANAT mRNA levels also persisted in DD in vivo, suggesting that they are driven by a circadian oscillator. In contrast, the rhythm of HIOMT mRNA in the retina appeared to be controlled only by light. The clones of chicken AANAT and HIOMT genes that we have isolated should help us to understand the molecular mechanisms of: 1) their transcriptional regulation by circadian oscillators and by light; 2) their tissue-specific expression in the pineal gland and the retina.

ARNTL Transcription Factors↗
PubMed2004

Using checklists and reminders in clinical pathways to improve hospital inpatient care.

OBJECTIVES: To determine whether the quality of hospital inpatient care can be improved by using checklists and reminders in clinical pathways. DESIGN: Comparison of key indicators before and after the introduction of clinical pathways incorporating daily checklists and reminders of best practice integrated into patient medical records. SETTING AND PARTICIPANTS: The study, at Wimmera Base Hospital in Horsham, Victoria, included patients admitted between 1 January 1999 and 31 December 2002 with ST-elevation acute myocardial infarction (AMI) and patients admitted between 31 July 1999 and 31 December 2002 with stroke. MAIN OUTCOME MEASURES: Compliance with key process measures determined as best practice for each clinical pathway. RESULTS: 116 patients with AMI and 123 patients with stroke were included in the study. ST-elevation AMI. After introducing the clinical pathway program, percentage-point increases for treatment compliance were 21.4% (95% CI, 7.3%-32.7%) for patients receiving aspirin in the emergency department; 42.7% (95% CI, 26.3%-59.0%) for eligible patients receiving beta-blockers within 24 h of admission; 48.1% (95% CI, 31.4%-64.8%) for eligible patients being prescribed beta-blockers on discharge; 43.7% (95% CI, 28.4%-59.1%) for patients having fasting lipid levels measured; and 41.2% (95% CI, 19.0%-63.5%) for eligible patients having lipid therapy. Stroke. After introducing the clinical pathway program, percentage-point increases for treatment compliance were 40.7% (95% CI, 21.0%-60.2%) for dysphagia screening within 24 h of admission; 55.4% (95% CI, 32.9%-77.9%) for patients with ischaemic stroke receiving aspirin or clopidogrel within 24 h of admission; and 52.4% (95% CI, 33.8%-70.9%) for patients having regular neurological observations during the first 48 h after a stroke. There was a fall of 1.0 percentage point (ie, a difference of -1% [95% CI, -4.7% to 10.0%]) in the proportion of patients having a computed tomography brain scan within 24 h of admission. CONCLUSION: Significant improvements in the quality of patient care can be achieved by incorporating checklists and reminders into clinical pathways.

Critical Pathways↗
PubMed2000

Mutation analysis of the pRb pathway in 2',3'-dideoxycytidine- and 1, 3-butadiene-induced mouse lymphomas.

The pRb pathway plays a key role in controlling the G1/S transition in cell cycle progression. Aberrations of various components of the pRb pathway, such as retinoblastoma protein and its upstream actors including cyclin D1, cyclin dependence kinase-4 and p16/p15 cyclin dependent kinase inhibitors, have been reported in a variety of human tumors. Furthermore, the alterations of retinoblastoma protein and its upstream components often occur in a reciprocal manner. Previously, we have reported frequent inactivation of the Cdkn2a/Cdkn2b loci encoding p16/p15 cyclin dependent kinase inhibitors in a subset of 2',3'-dideoxycytidine- and 1, 3-butadiene-induced mouse lymphomas (S.-M. Zhuang, A. Schippert, A. Haugen-Strano, R.W. Wiseman, P. Söderkvist, Inactivation of p16(INK4a)-alpha, p16(INK4a)-beta and p15(INK4b) genes in 2', 3'-dideoxycytidine- and 1,3-butadiene-induced lymphomas, Oncogene 16 (1998) 803-808), indicating the involvement of pRb pathway in lymphomagenesis. To investigate whether alteration of other components in pRb pathway is an alternative mechanism underlying the development of these chemically induced lymphomas, we have examined the genetic status of Rb1, Ccnd1 and Cdk4 genes that encode retinoblastoma protein, cyclin D1 and cyclin dependence kinase-4, respectively. Gross alterations of the Rb1, Ccnd1, and Cdk4 genes were not detected by Southern analysis in any of the tumors examined. In addition, single-strand conformation analysis failed to reveal point mutations in the Cdk4 amino terminal domain that is important for its association with Cdkn2a gene products. These results indicate that the mechanisms underlying the development of 2', 3'-dideoxycytidine- and 1,3-butadiene-induced lymphomas involve inactivation of p16/p15 cyclin-dependent kinase inhibitors but not genomic alterations of the Rb1, Ccnd1 and Cdk4 genes.

Animals↗
PubMed2005

PI3-kinase/Akt is constitutively active in primary acute myeloid leukaemia cells and regulates survival and chemoresistance via NF-kappaB, Mapkinase and p53 pathways.

The phosphoinositide 3-kinase (PI3-kinase) signalling pathway plays a key role in the regulation of cell survival and proliferation. We show that the PI3-kinase/Akt pathway is constitutively active in primary acute myeloid leukaemia (AML) cells and that blockade by the selective inhibitor LY294002 reduces survival of the total blast population (mean 52%). The ERK/MAPK module is also constitutively active and treatment with the MAPKK inhibitor U0126 reduces cell survival by 22%. In 10 of 18 samples, PI3-kinase contributes to MAPK activation as incubation with LY294002 leads to a marked reduction in its phosphorylation. PI3-kinase inhibition reduces survival of the CD34+38- AML progenitor subset by 44%, whereas MAPKK inhibition has little effect. Reporter assays in primary AML cells show that blocking PI3-kinase leads to a marked reduction of constitutive NF-kappaB activity and promotes p53-mediated transcription. This is associated with a synergistic interaction between LY294002 and Ara-C. An inducible activated form of Akt protects normal myeloid cells from Ara-C and etoposide-mediated apoptosis. These results show that blocking PI3-kinase has direct antileukaemic effects and potentiates the response to conventional cytotoxics via a number of targets including NF-kappaB, p53 and MAPK. Inhibitors of PI3-kinase and Akt may be useful in the treatment of AML.

ADP-ribosyl Cyclase↗
PubMed2006

Care pathways in obstetrics: the effectiveness in reducing the incidence of episiotomy in childbirth.

AIM: To develop a care pathway for childbirth. BACKGROUND: Care pathways are emerging as an effective tool to improve clinical and organizational performance. METHODS: A pre- and postimplementation analysis model was used to evaluate the effect of introducing a care pathway for childbirth. Key outcome indicators and costs were reviewed to compare the traditional care processes with those of the care pathway. The study involved 380 women. RESULTS: There was a significant reduction in episiotomy rate (from 14.90% to 8.6%, P = 0.02) in patients being cared for using a care pathway approach; however, there were no differences in caesarean section and in perineal wound rates. The average costs per patient on the care pathway were euro 1278.42 ( pound 873.64) compared with euro 1,146.87 ( pound 783.74) preimplementation. The study also demon- strated an increase in patient satisfaction for women cared for using the care pathway approach. CONCLUSIONS: The care pathway proved to be a valid methodological approach to childbirth, allowing healthcare workers to efficiently share the care of the women, guaranteeing safe and effective care.

Adult↗
PubMedDate not supplied

[Alternativity of methane assimilation pathways in obligate methylotrophs].

The activity of key enzymes involved in the primary pathways of methane assimilation and enzymes of the citrate cycle was determined in various obligate methylotrophs: mesophilic, thermotolerant, and thermophilic. The bacteria are characterized by the membrane ultrastructure of the I type, high activity of hexosephosphate synthase, NAD- and NADP-specific isocitrate dehydrogenase, and the absence of alpha-ketoglutarate dehydrogenase. The bacteria also displayed the activity of key enzymes of the serine cycle, hydroxypyruvate reductase, and serineglyoxylate aminotransferase. Therefore, both the ribulose monophosphate and serine pathways are involved in methane assimilation, and the division of methanotrophs into two groups, according to their metabolism, is tentative.

Aldehyde-Lyases↗
PubMed2005

Ero1-L alpha plays a key role in a HIF-1-mediated pathway to improve disulfide bond formation and VEGF secretion under hypoxia: implication for cancer.

Oxygen is the ultimate source of oxidizing power for disulfide bond formation, suggesting that under limiting oxygen proper protein folding might be compromised. We show that secretion of vascular endothelial growth factor (VEGF), a protein with multiple disulfide bonds, was indeed impeded under hypoxia and was partially restored by artificial increase of oxidizing equivalents with diamide. Physiologically, the oxireductase endoplasmic reticulum oxidoreductin-1 (Ero1)-L alpha, but not other proteins in the relay of disulfide formation, was strongly upregulated by hypoxia and independently by hypoglycemia, two known accompaniments of tumors. Further, we provide genetic evidence that induction of Ero1-L alpha by hypoxia and hypoglycemia is mediated by the transcription factor hypoxia-inducible factor 1 (HIF-1) but is independent of p53. In natural human tumors, Ero1-L alpha mRNA was specifically induced in hypoxic microenvironments coinciding with that of upregulated VEGF expression. To establish a physiological relevance to modulations in Ero1-L alpha levels, we showed that even a modest, two- to three-fold reduction in Ero1-L alpha production via siRNA leads to significant inhibition of VEGF secretion, a compromised proliferation capacity and enhanced apoptosis. Together, these findings demonstrate that hypoxic induction of Ero1-L alpha is the key adaptive response in a previously unrecognized HIF-1-mediated pathway that operates to improve protein secretion under hypoxia and might be harnessed for inhibiting tumor growth via inhibiting VEGF-driven angiogenesis.

Animals↗
PubMed2006

New paradigms in anticancer therapy: targeting multiple signaling pathways with kinase inhibitors.

Signal transduction in cancer cells is a sophisticated process that involves receptor tyrosine kinases (RTKs) that eventually trigger multiple cytoplasmic kinases, which are often serine/threonine kinases. A number of tumor models have identified several key cellular signaling pathways that work independently, in parallel, and/or through interconnections to promote cancer development. Three major signaling pathways that have been identified as playing important roles in cancer include the phosphatidyl inositol-3-kinase (PI3K)/AKT, protein kinase C (PKC) family, and mitogen-activated protein kinase (MAPK)/Ras signaling cascades. In clinical trials, highly selective or specific blocking of only one of the kinases involved in these signaling pathways has been associated with limited or sporadic responses. Improved understanding of the complexity of signal transduction processes and their roles in cancer has suggested that simultaneous inhibition of several key kinases at the level of receptors and/or downstream serine/threonine kinases may help to optimize the overall therapeutic benefit associated with molecularly targeted anticancer agents. Using targeted agents to inhibit multiple signaling pathways has emerged as a new paradigm for anticancer treatment based on preclinical and clinical data showing potent anti-tumor activity of single drugs inhibiting multiple molecular targets or combination therapies involving multiple drugs with selective or narrow target specificity. Preclinical and clinical studies point to molecules on vascular endothelial cells and pericytes as being important targets for anticancer therapies, as well as molecules on or within tumor cells themselves. This suggests that optimal therapeutic approaches to cancer may involve targeting multiple molecules found in both the tumor and supportive tissues. In this review, we will use the most recent preclinical and clinical data to describe this emerging paradigm for anticancer therapy involving targeting multiple signaling pathways with tyrosine or serine/threonine kinase inhibitors.

Antineoplastic Agents↗