Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hypoxia is a common environmental stimulus. However, very little is known about the mechanisms by which cells sense and respond to changes in oxygen. Our laboratory has utilized the PC12 cell line in order to study the biophysical and molecular response to hypoxia. The current review summarizes our results. We demonstrate that the O2-sensitive K(+) channel, Kv1.2, is present in PC12 cells and plays a critical role in the hypoxia-induced depolarization of PC12 cells. Previous studies have shown that PC12 cells secrete a variety of autocrine/paracrine factors, including dopamine, norepinephrine, and adenosine during hypoxia. We investigated the mechanisms by which adenosine modulates cell function and the effect of chronic hypoxia on this modulation. Finally, we present results identifying the mitogen- and stress-activated protein kinases (MAPKs and SAPKs) as hypoxia-regulated protein kinases. Specifically, we show that p38 and an isoform, p38gamma, are activated by hypoxia. In addition, our results demonstrate that the p42/p44 MAPK protein kinases are activated by hypoxia. We further show that p42/p44 MAPK is critical for the hypoxia-induced transactivation of endothelial PAS-domain protein 1 (EPAS1), a hypoxia-inducible transcription factor. Together, these results provide greater insight into the mechanisms by which cells sense and adapt to hypoxia.
Comp Biochem Physiol B Biochem Mol Biol 2001 Feb
PMID:The molecular basis of O2-sensing and hypoxia tolerance in pheochromocytoma cells. 1120 33

Central cellular functions such as metabolism, solute transport and signal transduction are regulated, in part, via binding of small molecules by specialized domains. Using sensitive methods for sequence profile analysis and protein structure comparison, we exhaustively surveyed the protein sets from completely sequenced genomes for all occurrences of 21 intracellular small-molecule-binding domains (SMBDs) that are represented in at least two of the three major divisions of life (bacteria, archaea and eukaryotes). These included previously characterized domains such as PAS, GAF, ACT and ferredoxins, as well as three newly predicted SMBDs, namely the 4-vinyl reductase (4VR) domain, the NIFX domain and the 3-histidines (3H) domain. Although there are only a limited number of different superfamilies of these ancient SMBDs, they are present in numerous distinct proteins combined with various enzymatic, transport and signal-transducing domains. Most of the SMBDs show considerable evolutionary mobility and are involved in the generation of many lineage-specific domain architectures. Frequent re-invention of analogous architectures involving functionally related, but not homologous, domains was detected, such as, fusion of different SMBDs to several types of DNA-binding domains to form diverse transcription regulators in prokaryotes and eukaryotes. This is suggestive of similar selective forces affecting the diverse SMBDs and resulting in the formation of multidomain proteins that fit a limited number of functional stereotypes. Using the "guilt by association approach", the identification of SMBDs allowed prediction of functions and mode of regulation for a variety of previously uncharacterized proteins.
J Mol Biol 2001 Apr 13
PMID:Regulatory potential, phyletic distribution and evolution of ancient, intracellular small-molecule-binding domains. 1129 41

The FixL/FixJ two-component regulatory system of Sinorhizobium meliloti controls the expression of nitrogen fixation genes in response to O2. When phosphorylated, the transcription factor FixJ binds to the nifA and fixK promoters in S. meliloti and induces expression of the corresponding genes, both of which encode key transcription activators. Phosphorylation of FixJ has been proposed to occur via the following cascade. The sensor kinase FixL reacts with ATP independently of FixJ, transferring a phosphoryl group to one of its own histidine residues. Dissociation of O2 from a heme-binding PAS domain in FixL greatly accelerates the rate of this autophosphorylation. The phosphoryl group is rapidly transferred from phospho-FixL to an aspartate residue on FixJ. The resulting phospho-FixJ is short-lived, due to a FixL-catalyzed hydrolysis of the aspartyl phosphate. Here, we show that phosphorylation of FixLJ, i.e. the complex of FixL with FixJ, is at least tenfold faster than the phosphorylation of FixL without FixJ. We further show that a phospho-FixJ phosphatase, thought to reside in FixL, is absent from this complex. These results indicate that FixLJ reacts with ATP as a unit and much more efficiently than FixL alone, and that autophosphorylation and phosphoryl transfer do not occur independently, in sequence, but rather in a closely coupled processive reaction. These findings highlight the possible influence of synergistic interactions of the regulatory components in two-component-system signal transduction.
J Mol Biol 2001 May 04
PMID:Complexation precedes phosphorylation for two-component regulatory system FixL/FixJ of Sinorhizobium meliloti. 1132 79

Grape seed extract, primarily a mixture of proanthocyanidins, has been shown to modulate a wide-range of biological, pharmacological and toxicological effects which are mainly cytoprotective. This study assessed the ability of IH636 grape seed proanthocyanidin extract (GSPE) to prevent acetaminophen (AAP)-induced nephrotoxicity, amiodarone (AMI)-induced lung toxicity, and doxorubicin (DOX)-induced cardiotoxicity in mice. Experimental design consisted of four groups: control (vehicle alone), GSPE alone, drug alone and GSPE+drug. For the cytoprotection study, animals were orally gavaged 100 mg/Kg GSPE for 7-10 days followed by i.p. injections of organ specific three drugs (AAP: 500 mg/Kg for 24 h; AMI: 50 mg/Kg/day for four days; DOX: 20 mg/Kg for 48 h). Parameters of study included analysis of serum chemistry (ALT, BUN and CPK), and orderly fragmentation of genomic DNA (both endonuclease-dependent and independent) in addition to microscopic evaluation of damage and/or protection in corresponding PAS stained tissues. Results indicate that GSPE preexposure prior to AAP, AMI and DOX, provided near complete protection in terms of serum chemistry changes (ALT, BUN and CPK), and significantly reduced DNA fragmentation. Histopathological examination of kidney, heart and lung sections revealed moderate to massive tissue damage with a variety of morphological aberrations by all the three drugs in the absence of GSPE preexposure than in its presence. GSPE+drug exposed tissues exhibited minor residual damage or near total recovery. Additionally, histopathological alterations mirrored both serum chemistry changes and the pattern of DNA fragmentation. Interestingly, all the drugs, such as, AAP, AMI and DOX induced apoptotic death in addition to necrosis in the respective organs which was very effectively blocked by GSPE. Since AAP, AMI and DOX undergo biotransformation and are known to produce damaging radicals in vivo, the protection by GSPE may be linked to both inhibition of metabolism and/or detoxification of cytotoxic radicals. In addition, its' presumed contribution to DNA repair may be another important attribute, which played a role in the chemoprevention process. Additionally, this may have been the first report on AMI-induced apoptotic death in the lung tissue. Taken together, these events undoubtedly establish GSPE's abundant bioavailability, and the power to defend multiple target organs from toxic assaults induced by structurally diverse and functionally different entities in vivo.
Res Commun Mol Pathol Pharmacol 2000
PMID:In vivo protection of dna damage associated apoptotic and necrotic cell deaths during acetaminophen-induced nephrotoxicity, amiodarone-induced lung toxicity and doxorubicin-induced cardiotoxicity by a novel IH636 grape seed proanthocyanidin extract. 1133 64

The bHLH-PAS transcription factor SIM1 is required for the development of the paraventricular nucleus (PVN) of the hypothalamus. Mice homozygous for a null allele of Sim1 (Sim1(-/-)) lack a PVN and die perinatally. In contrast, we show here that Sim1 heterozygous mice are viable but develop early-onset obesity, with increased linear growth, hyperinsulinemia and hyperleptinemia. Sim1(+/-) mice are hyperphagic but their energy expenditure is not decreased, distinguishing them from other mouse models of early-onset obesity such as deficiencies in leptin and melanocortin receptor 4. Quantitative histological comparison with normal littermates showed that the PVN of Sim1(+/-) mice contains on average 24% fewer cells without a selective loss of any identifiable major cell type. Since acquired lesions in the PVN also induce increased appetite without a decrease in energy expenditure, we propose that abnormalities of PVN development cause the obesity of Sim1(+/-) mice. Severe obesity was described recently in a patient with a balanced translocation disrupting SIM1. Pathways controlling the development of the PVN thus have the potential to cause obesity in both mice and humans.
Hum Mol Genet 2001 Jul 01
PMID:Sim1 haploinsufficiency causes hyperphagia, obesity and reduction of the paraventricular nucleus of the hypothalamus. 1144 38

Hypoxia is a potent inducer of tumor angiogenesis, the process of which is mostly mediated by induction of vascular endothelial growth factor (VEGF). In this study, we investigated the effect of hypoxia on the expression of hypoxia-inducible factor-1alpha (HIF-1alpha) and endothelial PAS domain protein-1 (EPAS1). These two similar but distinct basic helix-loop-helix-PAS proteins have been postulated to activate VEGF expression in response to hypoxia. We showed that EPAS1, but not HIF-1alpha, is abundantly expressed in human lung adenocarcinoma A549 cells. Exposure of cultured A549 cells to hypoxia increased EPAS1 mRNA and protein levels. A specific inhibitor for Src family kinases, PP1, abolished the hypoxia-induced expression of EPAS1. Transient transfection assays revealed that forced expression of EPAS1 increased the reporter gene activity driven by EPAS1 promoter as well as by VEGF promoter. Finally, overexpression of EPAS1 by infection of adenoviral vector expressing EPAS1 cDNA evidently induced the endogenous EPAS1 gene expression. Together, these data demonstrate Src family kinases mediate the hypoxia-mediated EPAS1 gene expression, which in turn positively autoregulates its own expression. Given an EPAS1 as a potent activator of the VEGF gene, these findings will provide a novel insight into the mechanisms underlying the enhancement of growth property of EPAS1-expressing tumor cells under the hypoxic environment.
Am J Respir Cell Mol Biol 2002 Jan
PMID:Inducible expression of endothelial PAS domain protein-1 by hypoxia in human lung adenocarcinoma A549 cells. Role of Src family kinases-dependent pathway. 1175 Dec 12

In the frq-wc-based circadian feedback loops of Neurospora, two PAS domain-containing transcription factors, WHITE COLLAR-1 (WC-1) and WC-2, form heterodimeric complexes that activate the transcription of frequency (frq). FRQ serves two roles in these feedback loops: repressing its own transcription by interacting with the WC complex and positively upregulating the levels of WC-1 and WC-2 proteins. We report here that the steady-state level of WC-1 protein is independently regulated by both FRQ and WC-2 through different posttranscriptional mechanisms. The WC-1 level is extremely low in wc-2 knockout strains, and this low level of expression is independent of wc-1 transcription and FRQ protein expression. In addition, our data show that the PAS domain of WC-2 mediates the interactions of this protein with both WC-1 and FRQ in vivo. Such interactions are essential for maintaining the steady-state level of WC-1 and the proper function of WC-1 and WC-2 in circadian clock and light responses.
Mol Cell Biol 2002 Jan
PMID:PAS domain-mediated WC-1/WC-2 interaction is essential for maintaining the steady-state level of WC-1 and the function of both proteins in circadian clock and light responses of Neurospora. 1175 47

Aryl hydrocarbon receptor (AhR) belongs to the bHLH/PAS transcription factor family and is activated by various polycyclic or halogenated aromatic hydrocarbons, e.g. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 3-methylcholanthrene (3MC). In the present study, we showed that in U937 cells and human macrophages AhR, with its partner cofactor Arnt, is expressed and CYP1A1 mRNA expression is induced in the presence of AhR ligand 3MC. Moreover, we showed that AhR, associating with Arnt, binds to target DNA sequences and activates transcription. Since part of AhR is activated into DNA binding species in the absence of exogenous ligand and competitive AhR antagonist alpha-naphthoflavone inhibits this activation process with reducing CYP1A1 mRNA expression levels, the presence of endogenous ligand is indicated.
Mol Cell Biochem 2001 Oct
PMID:Aryl hydrocarbon receptor/dioxin receptor in human monocytes and macrophages. 1176 31

CDP-diacylglycerol synthase (CDS) is a key rate-limiting enzyme in the phospholipid metabolism of Plasmodium falciparum, converting phosphatidic acid to CDP-diacylglycerol. The CDS gene is predominantly expressed in the mature intraerythrocytic stages. Consequently, we physically and functionally characterized the CDS gene promoter. The mRNA transcription initiation site was mapped 121 bp upstream of the CDS gene translation start site. A 1909 bp 5' upstream sequence was isolated and found to be transcriptionally active thus constituting a functional CDS promoter. Mapping of this promoter identified a 44 bp cis-acting sequence, located between -1640 and -1596 bp upstream of the ATG codon, essential for efficient transcriptional activity. This 44 bp sequence binds specifically to nuclear factors from trophozoite stage parasites. We further showed that a 24 bp element, lying within the 44 bp sequence, mediates the specific binding to nuclear proteins and shows no significant homology to known eukaryotic DNA consensus sequence elements that bind transcription factors. The deletion of the 24 bp element abrogated promoter activity, indicating that this cis-acting sequence element is essential for efficient transcription of the CDS gene.
Mol Biochem Parasitol 2002 Apr 30
PMID:A 24 bp cis-acting element essential for the transcriptional activity of Plasmodium falciparum CDP-diacylglycerol synthase gene promoter. 1198 65

The aryl hydrocarbon receptor complex heterodimeric transcription factor, comprising the basic helix-loop-helix-Per-ARNT-Sim (bHLH-PAS) domain aryl hydrocarbon receptor (AHR) and aryl hydrocarbon receptor nuclear translocator (ARNT) proteins, mediates the toxic effects of TCDD (2,3,7,8 tetrachlorodibenzo-p-dioxin). The molecular events underlying TCDD-inducible gene activation, beyond the activation of the AHRC, are poorly understood. The SRC-1/NCoA-1, NCoA-2/GRIP-1/TIF-2, and p/CIP/AIB/ACTR proteins have been shown to act as mediators of transcriptional activation. In this report, we demonstrate that SRC-1, NCoA-2, and p/CIP are capable of independently enhancing TCDD-dependent induction of a luciferase reporter gene by the AHR/ARNT dimer. Furthermore, injection of anti-SRC-1 or anti-p/CIP immunoglobulin G into mammalian cells abolishes the transcriptional activity of a TCDD-dependent reporter gene. We demonstrate by coimmunoprecipitation and by a reporter gene assay that SRC-1 and NCoA-2 but not p/CIP are capable of interacting with ARNT in vivo after transient transfection into mammalian cells, while AHR is capable of interacting with all three coactivators. We confirm the interactions of ARNT and AHR with SRC-1 with immunocytochemical techniques. Furthermore, SRC-1, NCoA-2, and p/CIP all associate with the CYP1A1 enhancer region in a TCDD-dependent fashion, as demonstrated by chromatin immunoprecipitation assays. We demonstrate by yeast two-hybrid, glutathione S-transferase pulldown, and mammalian reporter gene assays that ARNT requires its helix 2 domain but not its transactivation domain to interact with SRC-1. This indicates a novel mechanism of action for SRC-1. SRC-1 does not require its bHLH-PAS domain to interact with ARNT or AHR, but utilizes distinct domains proximal to its p300/CBP interaction domain. Taken together, these data support a role for the SRC family of transcriptional coactivators in TCDD-dependent gene regulation.
Mol Cell Biol 2002 Jun
PMID:Recruitment of the NCoA/SRC-1/p160 family of transcriptional coactivators by the aryl hydrocarbon receptor/aryl hydrocarbon receptor nuclear translocator complex. 1202 42


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