Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The transcriptional regulation of the rat cholesterol 7 alpha-hydroxylase gene (CYP7) by hormones and signal transduction pathways was studied by transient transfection assay of the promoter activity. HepG2 cells were transfected with deletion mutants of the CYP7 upstream region linked to the luciferase reporter gene. The transcription of CYP7/luciferase chimeric genes was higher in confluent than in subconfluent cultures of HepG2 cells. Glucocorticoid receptors, in the presence of dexamethasone, up-regulated the CYP7 gene through two regions located between -3262 and -2803, and between -344 and -222, respectively. Thyroid hormones did not have any effect on the promoter activity. Insulin inhibited the promoter activity through sequences located between -344 and -222, and abolished the stimulation by dexamethasone. Hence, the insulin effect was dominant over that of glucocorticoids. Treatment of transfected HepG2 cells with phorbol 12-myristate 13-acetate (PMA), a known activator of protein kinase C (PKC), resulted in a time-dependent inhibition of the CYP7 promoter activity. The negative phorbol ester-response sequences were mapped between -344 and -222, and between -200 and -161, respectively. The CYP7 promoter activity was induced nearly 5-fold by all-trans-retinoic acid through sequences in the region from -200 to -129. Finally, cyclic AMP and protein kinase A (PKA) stimulated the expression of the CYP7/luciferase gene through multiple sequences in the distal and proximal regions, and both positive and negative response regions were mapped. Our results revealed that the -416 fragment of the rat CYP7 gene confers the activation by glucocorticoids and retinoic acid, and inhibition by insulin, phorbol esters and cAMP. It appears that this proximal promoter may contain a pleiotropic domain that regulates the effects of multiple signals.
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PMID:Hormonal regulation of the cholesterol 7 alpha-hydroxylase gene (CYP7). 865 80

Added to HeLa cells previously exposed to recombinant human interferon (IFN)-gamma for 20 h, thyroid hormone [L-thyroxine (T4)] in physiological concentrations potentiates the antiviral action of IFN-gamma by more than 100-fold in 4 h. We examined protein kinase activities for their contributions to the mechanism of this posttranslational effect of thyroid hormone. Added concurrently with thyroid hormone, the protein kinase C (PKC) inhibitor CGP-41251 (5 nM) blocked T4 potentiation of IFN-gamma action. Coincubated with CGP-41251, phorbol 12-myristate 13-acetate (PMA) reversed the effect of the inhibitor on thyroid hormone action. U-73122 (10 nM), a phospholipase C inhibitor, also blocked hormone potentiation. KT-5720 (500 nM), a protein kinase A (PKA) inhibitor, completely inhibited the T4 effect, whereas 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) restored hormone action in the presence of KT-5720. In the absence of T4, 8-BrcAMP and PMA, added together to cells in the 4-h paradigm, fully reproduced hormone potentiation of the antiviral effect of IFN-gamma. Incubated individually with IFN-gamma-treated cells, the two agonists had no potentiating action. Thyroid hormone apparently must activate both PKA and PKC in the nongenomic pathway of IFN-gamma action to enhance antiviral activity in HeLa cells.
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PMID:Potentiation by thyroxine of interferon-gamma-induced antiviral state requires PKA and PKC activities. 889 32

Nongenomic actions of thyroid hormone are by definition independent of nuclear receptors for the hormone and have been described at the plasma membrane, various cell organelles, the cytoskeleton, and in cytoplasm. The actions include alterations in solute transport (Ca2+, Na+, glucose), changes in activities of several kinases, including protein kinase C, cAMP-dependent protein kinase and pyruvate kinase M2 (PKM2), effects on efficiency of specific mRNA translation and mRNA t1/2, modulation of mitochondrial respiration, and regulation of actin polymerization (promotion of formation of F-actin). Iodothyronines also can regulate nongenomically the state of contractile elements in vascular smooth muscle cells (VSMC). The physiologic significance at the cellular level of certain of these actions has been demonstrated, for example, in the cases of myocardiocyte Na+ current, red cell Ca2+ content, and the control by hormone-induced alterations in actin solubility of cell surface activity of iodothyronine 5'-monodeiodinase activity and the intracellular distribution of protein disulfide isomerase activity. The physiologic significance of these actions at the organ or system level is less clear, but extranuclear effects of thyroid hormone on myocardial Na+ channel, sarcoplasmic reticulum Ca(2+)-ATPase activity, and contractile state of VSMC may each contribute to acute effects of thyroid hormone on cardiac output that have recently been described clinically. The molecular mechanisms for nongenomic actions are incompletely understood; relevant binding sites and signal transduction pathways have been described for hormone actions on plasma membrane Ca(2+)-ATPase activity, and PKM2 monomer is known to bind T3 and, as a result, prevent activation of the kinase via tetramer formation. Nongenomic actions of thyroid hormone may have different structure-activity relationships of iodothyronines from those effects that depend upon nuclear receptors; they may have different time courses and may invoke complex signal transduction pathways before the action is detected.
Thyroid 1996 Oct
PMID:Nongenomic actions of thyroid hormone. 893 79

Thyroid-stimulating hormone stimulates proliferation through both the cAMP-dependent protein kinase and Ras but not through Raf-1 and mitogen-activated and extracellular signal-related kinase kinase. We now report that thyroid-stimulating hormone represses mitogen-activated protein kinase activity and that microinjection of an effector domain mutant Ha-Ras protein, Ras(12V,37G), defective in Raf-1 binding and mitogen-activated protein kinase activation, stimulates DNA synthesis in quiescent and thyroid-stimulating hormone-treated thyrocytes. A yeast two-hybrid screen identified RalGDS as a Ras(12V,37G) binding protein and therefore a potential effector of Ras in these cells. Associations between Ras and RalGDS were observed in extracts prepared from thyroid cells. Microinjection of a mutant RalA(28N) protein thought to sequester RalGDS family members reduced DNA synthesis stimulated by Ras as well as cAMP-mediated DNA synthesis in two cell lines which respond to cAMP with mitogenesis. These results support the idea that RalGDS may be an effector of Ras in cAMP-mediated growth stimulation.
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PMID:RalGDS functions in Ras- and cAMP-mediated growth stimulation. 903 68

The conserved structure of the transcription factors of the Pax gene family may reflect functional conservation. We have demonstrated that the human Pax8 transcription factor is organized in several functional domains and contains two regions responsible for its nuclear localization, in addition to an activating region at the carboxy terminus of the protein and an inhibitory region encoded by the exon 9 present only in a splice variant PAX8a. Regions of PAX8 determining the nuclear localization of the PAX8A/lacZ fusions contain short amino acid sequences similar to several described nuclear localization sites (NLS). These NLS were identified in the paired domain and between the octapeptide and the residual homeodomain, respectively. The activating domain is encoded by the exons 10 and 11 and its function is modulated by the adjacent domains encoded by the exons 9 and 12. The domain encoded by exon 9 significantly inhibits the function of the activating domain. Pax8 is expressed in thyroid cells and its product binds promoters of the thyroglobulin and thyroperoxidase genes through its paired domain. Thyroid cell growth and differentiation depend on thyrotropin which, by stimulating cAMP synthesis, activates the cAMP-dependent protein kinase A (PKA). We have investigated a link between thyrotropin stimulation and gene activation by Pax8. Stimulation of cAMP synthesis augments Pax8-specific transcription in thyroid cells, indicating that PKA is involved in Pax8 activation. Cotransfection of GAL4/PAX8 fusions and the catalytic subunit of PKA in A126, a PKA-deficient derivative of the PC12 pheochromocytoma cell line, synergistically activates the GAL4-specific reporter, suggesting the activating domain of PAX8 is dependent upon the catalytic subunit of the PKA. We propose that this dependence is due to a hypothetical adaptor which forms a target for PKA and interacts with the activating domain of PAX8. We show that PAX8 isolated from the thyroid cell line FTRL5 is a phosphoprotein in which phosphorylation is not dependant on cAMP pathway activation. Our results suggest that Pax8 is part of the cAMP signaling pathway and mediates thyrotropin-dependent gene activation in thyroid cells. Investigation of the PAX8 expression in a panel of Wilms' tumors shows a striking correlation between the expression of PAX8 and another transcription factor, WT1, indicating that these two genes may interact in vivo.
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PMID:Determination of functional domains of the human transcription factor PAX8 responsible for its nuclear localization and transactivating potential. 928 8

In the Lewis rat model of experimental autoimmune thyroiditis (EAT), decreased immunodetectable connexin assembly into gap junctions and diminished intercellular communication are associated with the loss of thyroid function (hypothyroidism) that occurs prior to significant tissue destruction. The current study explores the hypothesis that the loss of connexin 43 (Cx43)-mediated intercellular communication in these cells is caused by upregulation of protein kinase C (pKC) activity. Thyrocytes isolated from EAT rats exhibited a 78% increase in basal pKC activity; whereas, basal protein kinase A (pKA) activity was unchanged. Increased pKC activity was a result of increased isozyme protein levels. Thyroid cells expressed pKC isozymes gamma and lambda and had elevated levels of alpha (40%), beta (30%), delta (31%), and epsilon (25%) as quantified by western blot analyses. Furthermore, modulation of pKC activity inversely altered Cx43 assembly and function in monolayer thyrocytes. For example, octoacetyl glycerol (OAG) treatment of normal thyrocyte monolayers to increase pKC activity resulted in deficient Cx43 gap junction assembly and reduced intercellular communication indistinguishable from the deficits in EAT thyrocytes. Conversely, calphostin C inhibition of pKC activity in EAT thyrocyte monolayers restored these parameters to normal. Thus, pharmacological modulations of pKC activity in cultured thyrocytes support a causal relation between the changes in pKC activity and Cx43-mediated intercellular communication. Abnormalities in autoimmune diseased thyroid tissue (eg, increased pKC) appear to contribute to reduced intercellular coordination of thyroid follicles and thereby can affect subsequent thyroid function. The persistence of target cell abnormalities in the absence of infiltrating lymphocytes and their products supports an alternative mechanism by which thyroid function can be affected that does not depend on the loss of thyroid glandular epithelium.
Thyroid 1997 Dec
PMID:Elevation of protein kinase C in thyrocytes isolated from a Lewis rat model of autoimmune thyroiditis prevents assembly of immunodetectable connexin43 gap junctions and reduces intercellular communication. 945 38

Thyroid hormone receptor (T3R) alpha-1 and its oncogenic derivative, the v-ERB A protein, are phosphorylated by cAMP-dependent protein kinase A. Although this phosphorylation appears to be necessary for the oncogenic properties of v-ERB A, the mechanism by which phosphorylation influences the functions of v-ERB A and of the normal T3R has not been established. The protein kinase A phosphorylation site in T3Ralpha-1 is within a domain that is known to contribute to the DNA recognition properties of these receptors. We therefore analyzed the effects of protein kinase A phosphorylation on DNA recognition by the normal T3Ralpha and by the v-ERB A oncoprotein. We report here that phosphorylation of these receptor derivatives does not significantly alter the overall affinity of receptor dimers for DNA. However, phosphorylation does notably alter DNA recognition by preventing, or greatly inhibiting, the ability of these receptors to bind to DNA as protein monomers. These studies suggest that the phosphorylation of T3Ralpha-1 and v-ERB A by protein kinase A may provide a means of altering promoter recognition through a post-translational modification.
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PMID:Phosphorylation of thyroid hormone receptors by protein kinase A regulates DNA recognition by specific inhibition of receptor monomer binding. 955 70

Mechanisms of triiodothyronine (T3) negative regulation of the human thyrotropin-releasing hormone (TRH) gene were investigated with a chimeric construct of the 5' flanking region fused to a luciferase reporter gene, transfected into human neuroblastoma cells (HTB-11). Maximum negative regulation was achieved with constructs containing bases -242 to +54. Four sequences in this region exhibited homology with half sites of thyroid hormone response elements (TRE) (AGGTCA). The most important site was a sequence with an overlapping TRE/CRE, involving bases -53 to -60 (TGACCTCA). Potential combinatorial interactions of thyroid hormone receptors and CREB at this site were explored. Modest promoter stimulation was achieved with dibutyryl cyclic adenosine monophosphate (cAMP) (10(-3) M) plus IBMX (0.5 mM). Stimulation was greatly enhanced (+820%) by cotransfection of a constitutively activated protein kinase A (pPKA) construct. Cotransfection with pCREB increased stimulation further to 1350% above control. Stimulation of pPKA and pCREB interfered with stimulation by unliganded TRbeta1, and co-transfected pPKA and pCREB blocked T3 negative inhibition by TRbeta1-T3 complexes. When this site was mutated by polymerase chain reaction (PCR) mutagenesis, the mutant construct failed to respond to unliganded TRbeta1, and stimulation by pPKA and/or pCREB was inhibited markedly, from 12.5- to 2.1-fold, p < 0.001. Moreover, TRbeta1-T3 complexes failed to show any inhibition of the mutated promoter. These results suggest that negative regulation is achieved by inhibition of CREB stimulation of the TRH promoter at this overlapping TRE/CRE site. The two cosuppressors, NCoR and SMRT, were able to augment stimulation of the TRH promoter by unliganded TRbeta1 and enhance the magnitude of T3 inhibition. The potential role of the TRH gene and the pathophysiology of thyroid hormone resistance was investigated with three mutant TRbeta1 constructs. Thyroid hormone resistance was found to be expressed at the level of TRH gene regulation, due to lowered inhibition by mutant TRbeta1-T3 complexes and by their dominant negative effects on wild-type TRbeta1-T3 inhibition. TRH gene expression has been identified in the heart. Cardiac TRH mRNA was not regulated by T3, in contrast to HTB-11 cells, but cardiac TRH mRNA density could be augmented by glucocorticoids and by testosterone. TRH receptors were identified using Scatchard blots that showed a kilodalton of 1.4 nM and a bmax of 10 pmol/mg protein. TRH-R mRNA was identified also by reverse transcription polymerase chain reaction (RT-PCR). Enhanced ventricular contractility by TRH was demonstrated in both an open-chested dog preparation and in ex vivo ventricular myocytes, using video edge cinematography. Under controlled conditions, myocyte shortening was 13.3%, and TRH (10(-6) M) caused muscle shortening to increase 140%, (p < 0.005). TRH gene expression was demonstrated exclusively in Leydig cells of the testis. High affinity binding sites were identified in testicular membranes with a kilodalton of 1.6 x 10(-6) M. TRH was able to inhibit LH and HCG-activated testosterone secretion significantly. Thus, one paracrine role of TRH in the testis may be to serve as inhibitory modulator of gonadotropin-stimulated testosterone secretion.
Thyroid 1998 Oct
PMID:The thyrotropin-releasing hormone gene 1998: cloning, characterization, and transcriptional regulation in the central nervous system, heart, and testis. 982 56

We studied whether bovine pituitary thyrotropin (bTSH) or human recombinant thyrotropin (rhTSH) stimulated p42/p44 mitogen-activated protein kinases (MAPKs) in Chinese hamster ovary cells expressing human thyrotropin receptor (CHO-hTSHR cells). We show that p42/p44 MAPK phosphorylation was induced by both TSH preparations at similar levels in CHO-hTSHR cells and in wild-type CHO cells. In contrast, cyclic adenosine monophosphate (cAMP) production was stimulated by TSH only in CHO-hTSHR cells, demonstrating that p42/p44 MAPK stimulation was independent of the TSH receptor. Moreover, similar results were obtained with two other cell lines: the FRTL-5 thyroid cell line and the CCL39 fibroblast cell line. Maximal stimulation of p42/p44 MAPK phosphorylation was observed after a 5- to 10-minute incubation with bTSH and rhTSH preparations. At this time, the phosphorylation of GST-Elk1 was also increased in a time- and concentration-dependent manner by bTSH preparations. The phosphorylation of p42/p44 MAPKs was abolished by PD 98059 and GF 109203X, indicating the involvement of MAPK kinases (MEK 1/2) and protein kinase C. In contrast, the activation of p42/p44 MAPKs was insensitive to H89, to cholera toxin and to pertussis toxin. These data suggest that the protein kinase A pathway was not implicated in p42/p44 MAPK activation by TSH preparations. Moreover, Gs or Gi/Go proteins do not appear to participate in p42/p44 MAPK activation. We also showed that these TSH preparations failed to induce activation of c-Jun NH2 terminal kinase. We therefore conclude that the commercial TSH preparations used in this study contained factor(s) responsible for the specific activation of p42/p44 MAPKs by a TSH receptor-independent mechanism.
Thyroid 2000 Sep
PMID:The thyrotropin receptor is not involved in the activation of p42/p44 mitogen-activated protein kinases by thyrotropin preparations in Chinese hamster ovary cells expressing the human thyrotropin receptor. 1104 51

Anaplastic thyroid carcinoma (ATC) is the most malignant and aggressive form of thyroid cancer. Most patients die within months of diagnosis, primarily due to the absence of effective chemotherapeutic strategies. Identifying alternative therapies is necessary to increase long-term survival. Butyrate elicits a number of responses from cancer cells both in vitro and in vivo including growth repression, cell cycle arrest, differentiation, and apoptosis. Even though many types of cancer cells have been studied, little is known of the response of ATC cells to this drug. In this study, we report that butyrate induces differential cell cycle arrest (arrest in G1 and G2/M phases) in an ATC cell line that correlates with changes in the expression, phosphorylation, and activity of key components of the cell cycle machinery. Exposure to butyrate increases the expression of the cyclin-dependent kinase inhibitors, p21/Cip1 and p27/Kip1, decreases the expression of cyclin A and cyclin B, inhibits the phosphorylation of the retinoblastoma protein (pRb), and decreases the activity of cdk1 and cdk2-associated kinases. These results suggest that butyrate may be useful in the clinical treatment of ATC.
Thyroid 2001 Jan
PMID:Butyrate alters the expression and activity of cell cycle components in anaplastic thyroid carcinoma cells. 1127 92


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