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

Oestrogens regulate the expression of genes both positively and negatively in a range of cell types. These effects are mediated via the oestrogen receptor (ER) and involve direct interactions between the ER and DNA response elements, as well as interactions between the ER and other nuclear proteins. We have examined the potential of the ERalpha to regulate the expression of reporter genes under the control of oestrogen response elements (EREs), NFkappaB response elements (NREs) or AP-1/TPA response elements (TREs) in HeLa cells and in human embryonic kidney (HEK-293) cells. Transiently transfected ERalpha was able to activate expression of beta-galactosidase under the control of EREs in an oestradiol (E2)-dependent manner in both HeLa and HEK-293 cells. The ERalpha was able to repress by 80% the TNF-mediated expression of beta-galactosidase under the control of NREs in an E2-dependent manner in HeLa cells but not in HEK-293 cells. ERalpha/E2 also induced a two-fold potentiation of TPA-mediated expression of beta-galactosidase under the control of TREs in HeLa cells but not in HEK-293 cells. These results suggest that the ERalpha is capable of regulating gene expression in a cell-specific manner. We further investigated the mechanisms by which the ERalpha regulates gene expression in these systems by co-expressing the ERalpha and the reporter gene constructs with known cofactors of the ERalpha. We have shown that expression of steroid receptor coactivator-1 alpha (SRC-1alpha) and receptor interacting protein-140 (RIP-140) have no effect on the capacity of the ERalpha to modulate NFkappaB reporter gene activity in HeLa cells. Furthermore, the expression of SRC-1alpha or RIP-140 does not enable the ERalpha to repress NFkappaB or to potentiate an AP-1 response in HEK-293 cells. This suggests that factors other than SRC-1alpha or RIP-140 are responsible for the cell-specific effects seen with ERalpha.
J Steroid Biochem Mol Biol 1998 Oct
PMID:The oestrogen receptor regulates NFkappaB and AP-1 activity in a cell-specific manner. 987 7

Familial male-limited precocious puberty (FMPP) is a form of luteinizing hormone-releasing hormone (LHRH)-independent isosexual precocious puberty caused by gain-of-function mutations of the luteinizing hormone/chorionic gonadotropin receptor (hLHR). The most common mutation is 1733 A>G, which causes substitution of Asp-578 by Gly. In this study, a male infant presented at the age of 20 months with accelerated sexual development was analyzed for the presence of activating mutations of the hLHR. Analysis of exon 11 of the hLHR gene by genomic polymerase chain reaction (PCR), asymmetric PCR, and dideoxy sequencing identified a single base substitution, 1734 T>A, which led to the replacement of Asp-578 by Glu. The same mutation was found in the mother. Expression of the mutated hLHR in HEK 293 cells demonstrated elevated basal levels of intracellular cAMP in the transfected cells confirming the constitutive activating nature of the mutated hLHR. A possible genotype-phenotype relationship of the hLHR mutations was examined by a comparison of the in vitro activities of the hLHRs carrying the Asp578Gly, Asp578Tyr, Asp578Trp, and Asp578Glu mutations in HEK 293 cells. A positive correlation between the size of the substituting amino acid and the basal level of intracellular cAMP of cells expressing the mutated receptor was demonstrated.
Mol Genet Metab 1999 Jan
PMID:A novel luteinizing hormone receptor mutation in a patient with familial male-limited precocious puberty: effect of the size of a critical amino acid on receptor activity. 997 50

Juvenile neuronal ceroid lipofuscinosis is a lysosomal storage disease that causes visual impairment, progressive mental deterioration, and eventually death. A predominant 1.02-kb deletion as well as other mutations have been described in the CLN3 gene. Lacking significant identity with proteins of known function and no overt targeting signals within the primary amino acid sequence, accurate predictions of the intracellular location and function could not be made. Further, recent conflicting reports identified CLN3 as either a lysosomal or a mitochondrial protein. Transfection experiments using native and epitope-tagged fusion proteins were evaluated to help delineate CLN3 localization. We confirmed by immunohistochemistry and brefeldin A treatment that NH2-terminal green fluorescence protein (GFP)-CLN3 fusion proteins were retained in the Golgi apparatus, with no colocalization with mitochondrial markers. Anti-CLN3 antibodies directed against amino acids 67-90 of CLN3 were generated and shown to be specific for a 50-kDa protein in HEK 293 cells and GFP-CLN3 in transfected cells. However, cells transfected with nontagged CLN3 or carboxyl-terminal-tagged CLN3 were not immunoreactive with anti-CLN3 antibodies, suggesting that normally, the amino terminus interacts with other molecules. Thus, tags on the NH2-terminus probably inhibited these interactions and movement of CLN3 from the Golgi to more distal compartments. Also, CLN3 tagged at the COOH-terminus with either GFP or FLAG epitopes were retained in the ER, indicating a role for the COOH-terminus in trafficking. Taken together, these data confirm that CLN3 traffics through the ER and Golgi.
Mol Genet Metab 1999 Apr
PMID:Intracellular trafficking of the JNCL protein CLN3. 1019 Nov 11

The multidrug resistance protein MRP1 functions as an ATP-dependent conjugate export pump and confers multidrug resistance. We cloned MRP2 (symbol ABCC2), a MRP family member localized to the apical membrane of polarized cells. Stable expression of MRP2 in transfected human embryonic kidney (HEK-293) and Madin-Darby canine kidney (MDCK) cells was enhanced by inhibitors of histone deacetylase. In polarized MDCK cells, both rat and human MRP2 were sorted to the apical plasma membrane. An antibody raised against the amino terminus of rat MRP2 recognized the recombinant protein on the apical surface of nonpermeabilized cells, providing direct evidence for the extracellular localization of the amino terminus of MRP2. ATP-dependent transport by recombinant human and rat MRP2 was measured with membrane vesicles from stably transfected cells. The Km value of human MRP2 was 1.0 +/- 0.1 microM for leukotriene C4 and 7.2 +/- 0.7 microM for 17beta-glucuronosyl estradiol; the Km values of human MRP1 were 0.1 +/- 0.02 microM for leukotriene C4 and 1.5 +/- 0.3 microM for 17beta-glucoronosyl estradiol. Thus, the conjugate-transporting ATPases MRP2 and MRP1 differ not only by their domain-specific localization but also by their kinetic properties. Drug resistance conferred by recombinant MRP2 was studied in MDCK and HEK-293 cells using cell viability assays. Expression of human and rat MRP2 enhanced the resistance of MDCK cells to etoposide 5.0-fold and 3.8-fold and to vincristine 2.3- and 6.0-fold, respectively. Buthionine sulfoximine reduced resistance to these drugs. Human MRP2 overexpressed in HEK-293 cells enhanced the resistance to etoposide (4-fold), cisplatin (10-fold), doxorubicin (7.8-fold), and epirubicin (5-fold). These results demonstrate that MRP2 confers resistance to cytotoxic drugs.
Mol Pharmacol 1999 May
PMID:Drug resistance and ATP-dependent conjugate transport mediated by the apical multidrug resistance protein, MRP2, permanently expressed in human and canine cells. 1022 May 72

The mammalian GnRH receptor is an atypical G protein-coupled receptor which lacks the C-terminal cytoplasmic tail that is present in all other seven-transmembrane domain receptors. The mouse and rat GnRH receptors contain 327 amino acids, whereas human, sheep, and bovine receptors have an additional residue in the second extracellular loop at position 191. Another notable species difference is that human receptors undergo agonist-induced internalization much more rapidly than the mouse receptor. In this report, the role of the additional amino acid (Lys191) in GnRH receptor function was studied in transiently expressed mutant and wild-type human and mouse GnRH receptors. Deletion of Lys191 from the human GnRH receptor caused a 4-fold increase in receptor expression in COS-1 and HEK 293 cells and a modest increase in binding affinity. The magnitude of the agonist-induced inositol phosphate response mediated by the deltaK191 human receptor was similar to that of the wild-type receptor, but the EC50 was decreased by about 5-fold. In addition, the rate of internalization of the deltaK191 human receptor was significantly reduced and was similar to that of the mouse receptor. In contrast to these effects of deletion of Lys191, its replacement by Arg, Glu, Gln, or Ala caused no significant change in receptor expression or function. These findings demonstrate that a specific residue in the extracellular region of the human GnRH receptor is a significant determinant of receptor expression, agonist-induced activation, and internalization.
Mol Endocrinol 1999 Jun
PMID:Influence of a species-specific extracellular amino acid on expression and function of the human gonadotropin-releasing hormone receptor. 1037 88

The human olfactory system can recognize and discriminate a large number of different odorant molecules. The detection of chemically distinct odorants begins with the binding of an odorant ligand to a specific receptor protein on the olfactory neuron cell surface. To address the problem of olfactory perception at a molecular level, we have cloned, functionally expressed and characterized the first human olfactory receptor (OR 17-40). Application of a mixture of hundred different odorants elicited a transient increase in intracellular calcium at HEK 293-cells which were transfected with a plasmid containing the receptor encoding DNA and a membrane import sequence. By subdividing the odorant mixture in smaller groups we could identify a single component which represented the only effective substance: helional. Testing some structurally closely related molecules we found only one other compound which also could activate the receptor: heliotropyl acetone. All other compounds tested were completely ineffective. These findings represent the beginning of molecular understanding of odorant recognition in humans.
Cell Mol Biol (Noisy-le-grand) 1999 May
PMID:Cloning, functional expression and characterization of a human olfactory receptor. 1038 85

The muscle acetylcholine receptor (AChR) has served as a prototype for understanding allosteric mechanisms of neurotransmitter-gated ion channels. The phenomenon of cooperative agonist binding is described by the model of Monod et al. (Monod, J., Wyman, J., and Changeux, J. P. (1965) J. Mol. Biol. 12, 88-118; MWC model), which requires concerted switching of the two binding sites between low and high affinity states. The present study examines binding of acetylcholine (ACh) and epibatidine, agonists with opposite selectivity for the two binding sites of mouse muscle AChRs. We expressed either fetal or adult AChRs in 293 HEK cells and measured agonist binding by competition against the initial rate of 125I-alpha-bungarotoxin binding. We fit predictions of the MWC model to epibatidine and ACh binding data simultaneously, taking as constants previously determined parameters for agonist binding and channel gating steps, and varying the agonist-independent parameters. We find that the MWC model describes the apparent dissociation constants for both agonists but predicts Hill coefficients that are far too steep. An Uncoupled model, which relaxes the requirement of concerted state transitions, accurately describes binding of both ACh and epibatidine and provides parameters for agonist-independent steps consistent with known aspects of AChR function.
 ...
PMID:Acetylcholine and epibatidine binding to muscle acetylcholine receptors distinguish between concerted and uncoupled models. 1039 99

We previously described a splice donor site mutation in intron 4 of presenilin-1 (PSEN1) in two patients with autopsy-confirmed early-onset Alzheimer's disease (AD). Here we provide evidence that the intron 4 mutation is present in four additional unrelated early-onset AD cases, that the mutation segregates in an autosomal dominant manner and that all cases have one common ancestor. We demonstrate that the intron 4 mutation produces three different transcripts, two deletion transcripts (Delta4 and Delta4cryptic) and one insertion transcript (insTAC), by aberrant splicing. The deletion transcripts result in the formation of C-truncated (approximately 7 kDa) PSEN1 proteins while the insertion transcript produces a full-length PSEN1 with one extra amino acid (Thr) inserted between codons 113 and 114 (PSEN1 T113-114ins). The truncated proteins were not detectable in vivo in brain homogenates or lymphoblast lysates of mutation carriers. In vitro HEK-293 cells overexpressing Delta4, Delta4cryptic or insTACPSEN1 cDNAs showed increased Abeta42 secretion (approximately 3.4 times) only for the insertion cDNA construct. Increased Abeta42 production was also observed in brain homogenates. Our data indicate that in the case of intron 4 mutation, the AD pathophysiology results from the presence of the PSEN1 T113-114ins protein comparable with cases carrying dominant PSEN1 missense mutations.
Hum Mol Genet 1999 Aug
PMID:Aberrant splicing in the presenilin-1 intron 4 mutation causes presenile Alzheimer's disease by increased Abeta42 secretion. 1040 Oct 2

Agonist-elicited receptor sequestration is strikingly different for the alpha(2A)- versus alpha(2B)-adrenergic receptor (alpha(2)-AR) subtypes; the alpha(2B)-AR undergoes rapid and extensive disappearance from the HEK 293 cell surface, whereas the alpha(2A)-AR does not (Daunt, D. A., Hurt, C., Hein, L., Kallio, J., Feng, F., and Kobilka, B. K. (1997) Mol. Pharmacol. 51, 711-720; Eason, M. G., and Liggett, S. B. (1992) J. Biol. Chem. 267, 25473-25479). Since recent reports suggest that endocytosis is required for some G protein-coupled receptors to stimulate the mitogen-activated protein (MAP) kinase cascade (Daaka, Y., Luttrell, L. M., Ahn, S., Della Rocca, G. J., Ferguson, S. S., Caron, M. G., and Lefkowitz, R. J. (1998) J. Biol. Chem. 273, 685-688; Luttrell, L. M., Daaka, Y., Della Rocca, G. J., and Lefkowitz, R. J. (1997) J. Biol. Chem. 272, 31648-31656; Ignatova, E. G., Belcheva, M. M., Bohn, L. M., Neuman, M. C., and Coscia, C. J. (1999) J. Neurosci. 19, 56-63), we evaluated the differential ability of these two subtypes to activate MAP kinase. We observed no correlation between subtype-dependent agonist-elicited receptor redistribution and receptor activation of the MAP kinase cascade. Furthermore, incubation of cells with K(+)-depleted medium eliminated alpha(2B)-AR internalization but did not eliminate MAP kinase activation, suggesting that receptor internalization is not a general prerequisite for activation of the MAP kinase cascade via G(i)-coupled receptors. We also noted that neither dominant negative dynamin (K44A) nor concanavalin A treatment dramatically altered MAP kinase activation or receptor redistribution, indicating that these experimental tools do not universally block G protein-coupled receptor internalization.
 ...
PMID:Stimulation of mitogen-activated protein kinase by G protein-coupled alpha(2)-adrenergic receptors does not require agonist-elicited endocytosis. 1045 69

Previous work suggests that different neuroactive steroids may exhibit some selectivity in their blocking effects on different high-voltage activated (HVA) Ca2+ currents. At least some of these effects appear to involve direct blocking actions on Ca2+ channels. Thus, direct investigation of the effects of various steroids on cloned Ca2+ channel variants may lead to the development of potent and selective small-molecular weight Ca2+ channel blockers. Here we examine the effects of two steroids on a cloned human alpha1E Ca2+ channel both with and without a beta3 subunit, when expressed in HEK293 cells. One compound, (+)-ACN, has been previously shown to block N-, Q-, and R-subtypes of HVA current without affecting L- and P-type current. The second compound, (+)-ECN, weakly blocks total HVA current in hippocampal neurons. (+)-ECN differs from (+)-ACN in lacking effects on GABA receptors, but shares with (+)-ACN an ability to partially inhibit T current in DRG neurons (Todorovic, S.M., Prakriya, M., Nakashima, Y.M. et al., 1998. Enantioselective blockade of T-type Ca2+ current in adult rat sensory neurons by a steroid lacking GABA-mimetic activity. Mol. Pharmacol. 54, 918-927). (+)-ACN can block 100% of Ba2+ current in HEK cells arising either from the alpha1E subunit (IC50 approximate to 10 microM) or the alpha1Ebeta3 combination (IC50 approximate to 5 microM), while (+)-ECN maximally blocks only about 80% of the alpha1E (10 microM) or alpha1Ebeta3 (16 microM) current. Blockade by (+)-ACN exhibits several differences from blockade by (+)-ECN. (+)-ACN increases the apparent rate of onset of inactivation, particularly for the alpha1E variant, slows recovery from inactivation, and more profoundly shifts the voltage-dependence of current availability for both alpha1E and alpha1Ebeta3 variants than does (+)-ECN. Although the complexity of the normal inactivation kinetics of alpha1E variants makes interpretation of the (+)-ACN-induced kinetic alterations difficult, the results suggest that the two steroids are to some extent acting by distinct mechanisms, and perhaps at different sites.
 ...
PMID:Blockade of Ba2+ current through human alpha1E channels by two steroid analogs, (+)-ACN and (+)-ECN. 1046 88


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>