Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recently, it was shown that lipoprotein lipase (LPL) was produced in neonatal but not in adult rat liver. In an attempt to further define the mechanism involved in liver LPL expression, we identified a neonatal mouse hepatoma cell line, BWTG3, capable of producing LPL. The regulation of LPL expression by various extracellular stimuli was investigated in this cell line. Progesterone caused a rise in LPL production by BWTG3 cells. Other hormones tested, such as insulin, glucagon, adrenalin, testosterone, and thyroid hormone, had no effect on LPL production. The effects of progesterone on LPL production showed slow kinetics reaching a maximum 24 h after addition. Cotransfection of a progesterone receptor expression vector with a 5'-LPL-CAT reporter construct resulted in an induction of CAT activity, suggesting that the increase in LPL accumulation after progesterone was linked to transcriptional induction of the LPL gene. Stimuli causing an elevation of protein kinase A activity in the cells also increased LPL production. Three agents capable of elevating intracellular cAMP levels, i.e., forskolin, dBcAMP, and choleratoxin, caused an elevation of LPL production. The increase in LPL activity caused by forskolin and choleratoxin was paralleled by an elevation of LPL mRNA levels, while dBcAMP only induced a small elevation of LPL mRNA levels. The increase in LPL production was shown to be linked to the stimulation of the PKA signal transduction pathway and was apparently transmitted via the transcription factor CREB. No effect of the stimulation of protein kinase C or calcium/calmodulin-dependent kinase on LPL production was detected.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Lipoprotein lipase expression in undifferentiated hepatoma cells is regulated by progesterone and protein kinase A. 132 33

Although it is well-established that TSH activates a cAMP-dependent pathway in the thyroid follicular cell leading to thyroid hormone synthesis and release, the present review provides new evidence that TSH also activates a non-cAMP-dependent signal transduction system. This cascade involves phosphoinositide (PI) turnover, diacylglycerol accumulation and protein kinase C (PKC) activation. Activation of this pathway leads to an inhibition of differentiated thyroid function in vitro. Recent evidence suggests that TSH can activate both pathways via a single transcription unit. Unlike TSH, TSH-receptor antibodies may selectively activate cAMP with no effects on PI turnover. In contrast, preliminary studies suggest TSH-blocking antibodies may activate PKC. PKC may be an important mediator of TSH and, possibly, thyroid autoantibody action.
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PMID:Protein kinase C as a mediator of TSH and thyroid autoantibody action. 135 38

Lithium has been reported to alter thyroid function and cause goiter in some patients. To explain the mechanism of lithium action in the thyroid gland, we studied the effect of lithium on thyroid function and cell growth in FRTL-5 rat thyroid cells and on de novo thyroid hormone formation in primary cultures of porcine thyroid follicles. TSH-induced iodide uptake was suppressed at 2 mM lithium in both FRTL-5 cells and porcine follicles. In porcine thyroid follicles, iodide uptake stimulated by 8-bromo-cAMP, iodine organification, and de novo thyroid hormone formation were also reduced by lithium; however, 2 mM lithium did not inhibit TSH-induced cAMP production. In FRTL-5 cells, lithium also inhibited forskolin-stimulated iodide uptake. These results suggested that lithium exerts its effect at a step involving cAMP signal transduction rather than inhibiting cAMP production. In both FRTL-5 thyroid cells and porcine follicles, lithium enhanced cell growth in basal states (lacking TSH) and with TSH treatment. In porcine thyroid cells, the protein kinase C activator, tetradecanoyl phorbol-13-acetate, increased cell growth, and lithium had an additive effect with tetradecanoyl phorbol-13-acetate on cell growth. To examine the possibility that the action of lithium was mediated by the protein kinase C pathway, porcine cells were incubated with lithium and H7, a selective protein kinase C inhibitor. Lithium-induced cell growth was suppressed to the basal level by H7. These results suggest that lithium exerts its growth-promoting effect through the protein kinase C system.
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PMID:Effect of lithium on function and growth of thyroid cells in vitro. 164 47

Carbachol, through a muscarinic receptor, thyrotropin-releasing hormone (TRH), prostaglandin F2 alpha (PGF2 alpha), bradykinin, and adenosine triphosphate (ATP) increased the apparent [Ca2+]i (intracellular free Ca2(+)-concentration) of dog thyrocytes in primary culture. The [Ca2+]i measured by the Quin-2 technique rose immediately after the addition of the agonists and reached a maximal value after less than 30 seconds. Afterwards, the [Ca2+]i declined to a plateau higher than the basal level when the cells were triggered with carbachol. By contrast, in most experiments with PGF2 alpha and in the case of bradykinin, TRH, and ATP, the [Ca2+]i returned to the basal value. If the extracellular Ca2+ was chelated by excess of EGTA, the addition of all agents caused a sharp reduced transient rise in the [Ca2+]i followed by a decline of the [Ca2+]i often below the basal level (especially in the case of carbachol). It is suggested that the first transient phase of these responses is due at least in part to the mobilisation of Ca2+ from intracellular stores whereas the second sustained phase of the response to carbachol mainly originates from an increased Ca2+ influx into the thyrocytes. Carbachol, bradykinin, TRH, PGF2 alpha, and ATP also increased generation of inositol phosphates in dog thyrocytes. This effect was sustained when the cells were triggered with carbachol and was more transient with bradykinin, TRH, PGF2 alpha, or ATP. All these agents and the phorbdester TPA as well as forskolin enhanced to various extent the thyrocyte H2O2 generation. This enhancement was severely reduced in the absence of extracellular Ca2+ and was mimicked by Ca2+ ionophores in the presence of extracellular Ca2+ especially in synergy with protein kinase C activators. These data suggest that the dog thyrocyte H2O2 generation, the limiting step of the thyroid hormone synthesis, is modulated by carbachol, TRH, PGF2 alpha, bradykinin, and ATP through their action on the Ca2(+)-phosphatidylinositol cascade.
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PMID:Control of the intracellular Ca(2+)-concentration and the inositol phosphate accumulation in dog thyrocyte primary culture: evidence for different kinetics of Ca(2+)-phosphatidylinositol cascade activation and for involvement in the regulation of H2O2 production. 199 73

We have found that the thyroid hormone 3,5',3'-triiodo-L-thyronine stimulates the transformation of Rat 6 fibroblasts when these cells are transfected with an activated human c-Ha-ras oncogene (T24). 3,5',3'-Triiodo-L-thyronine did not further augment the stimulation of oncogene-induced transformation obtained with a phorbol ester tumor promoter (12-O-tetradecanoylphorbol-13-acetate) or a factor from fetal calf serum. On the other hand, tamoxifen, an antiestrogen that also inhibits protein kinase C, markedly inhibited Ha-ras-induced cell transformation in the presence of 12-O-tetradecanoylphorbol-13-acetate or fetal calf serum. Time course studies and Southern blot analyses of DNAs isolated from transformed foci provided evidence that 3,5',3'-triiodo-L-thyronine and tamoxifen do not exert their effects simply by enhancing or inhibiting integration of the transfected oncogene into cellular DNA. These findings indicate that hormonal factors can modulate the ability of an activated Ha-ras oncogene to transform cells. They may be relevant to the process of multistage carcinogenesis in vivo.
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PMID:Effects of triiodothyronine and tamoxifen on cell transformation induced by an activated c-Ha-ras oncogene. 264 66

We examined the extranuclear effects of thyroid hormones on human platelets. Pretreatment with DL-thyroxine or DL-triiodothyronine inhibited collagen-induced aggregation, in a dose-dependent manner, but other derivatives of thyroid hormone had no significant effects. In contrast to collagen, 12-O-tetradecanoylphorbol-13-acetate-induced aggregation was not affected by thyroid hormones at the same concentration range. Thyroxine also inhibited the release of [14C] serotonin from collagen-stimulated platelets, with a marked reduction in the phosphorylation of 20,000-dalton protein. Thyroxine and triiodothyronine had inhibitory effects on myosin light chain kinase purified from human platelets and inhibited more markedly the myosin light chain kinase than protein kinase C (Ca2+/phospholipid-dependent enzyme) and cAMP-dependent protein kinase. In addition, L-thyroxine behaved as a competitive inhibitor of myosin light chain kinase toward calmodulin, and the Ki value was calculated to be 2.6 microM. To determine whether or not thyroxine directly binds myosin light chain kinase, we prepared an affinity column, using L-thyroxine as the ligand. Myosin light chain kinase was selectively bound to the column while calmodulin passed through. We also designed a procedure for the purification of myosin light chain kinase from human platelets, using L-thyroxine-affinity chromatography. A markedly increased purification was thus achieved, and DEAE-cellulose and L-thyroxine-affinity chromatography were made feasible. These results suggest that thyroxine can serve as a pharmacological tool for elucidating the biological significance of myosin light chain kinase-mediated reactions and is a pertinent ligand which can be used to purify myosin light chain kinase from platelets as a substitute for calmodulin.
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PMID:Thyroid hormones inhibit platelet function and myosin light chain kinase. 272 89

The enzyme thyroid peroxidase (TPO) plays a central role in thyroid hormone synthesis and is the target for the autoimmune attack in lymphocytic thyroiditis. We have examined the activation of the TPO gene in cultured human thyrocytes using slot-blot hybridization with a synthetic 40 mer oligonucleotide probe derived from the nucleotide sequence of the human TPO gene. The oligonucleotide probe was shown by Northern blotting to hybridize specifically to an approximately 3 kb RNA species from thyroid tissue of patients with Graves' disease, but not to RNA preparations from human or bovine retinal tissue, providing compelling evidence for the specificity of the probe for TPO mRNA. Addition of TSH (10 mU/ml) to primary thyroid cultures for 4 h led to increased TPO mRNA levels which were maximal after 48 h and significantly higher than basal even after 7 days of co-culture. Activation of TPO mRNA by TSH showed dose dependency over a wide range (0.01-100 mU/ml), with a maximal effect at 10 mU TSH/ml in cells cultured for a period of 72 h. Comparison of TPO mRNA levels with the accumulation of thyroglobulin mRNA levels following stimulation by TSH indicated that the induction of the gene encoding thyroglobulin precedes transcription of the TPO gene. The adenylate cyclase activator forskolin (1-100 microM) mimicked TSH in increasing TPO mRNA levels whilst, in contrast, the phorbol ester 12-O-tetradecanoyl phorbol 13-acetate (TPA; 0.01-1 microM) led to levels of TPO mRNA that were lower than basal. Thus TSH induces a specific dose-dependent activation of TPO mRNA which is mimicked by agents which increase cyclic AMP. In contrast, TPA-induced activation of protein kinase C inhibits this response.
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PMID:Activation of the thyroid peroxidase gene in human thyroid cells: effect of thyrotrophin, forskolin and phorbol ester. 274 42

The c-erbA proto-oncogene encodes a nuclear receptor for thyroid hormone (T3), which is believed to stimulate transcription from specific target promoters upon binding to cis-acting DNA sequence elements. The v-erbA oncogene of avian erythroblastosis virus (AEV) encodes a ligand-independent version of this nuclear receptor. The v-erbA product inhibits terminal differentiation of avian erythroblasts, presumably by affecting the transcription of specific genes. We show here that the c-erbA-encoded nuclear receptor (p46c-erbA) is phosphorylated on serine residues on two distinct sites. One of these sites, defined by the limit tryptic phosphopeptide 28SSQCLVK, is retained on the v-erbA-encoded P75gag-v-erbA protein. This site is located in the amino-terminal domain of these molecules, 21 amino acids upstream of the DNA-binding region. Phosphorylation of this site in both p46c-erbA and P75gag-v-erbA is enhanced 10-fold following treatment of cells with activators of either protein kinase C or cAMP-dependent protein kinase. Since cAMP-dependent protein kinase phosphorylates both p46c-erbA and P75gag-v-erbA in vitro at the same site as that observed in vivo, at least part of the cAMP-dependent phosphorylation of erbA molecules in cells could result from direct phosphorylation by this enzyme. The possible role phosphorylation may play in the function of the erbA-encoded transcriptional factors is discussed.
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PMID:Activation of protein kinase C or cAMP-dependent protein kinase increases phosphorylation of the c-erbA-encoded thyroid hormone receptor and of the v-erbA-encoded protein. 290 25

The regulation of T4 5'-deiodinase activity was studied in cultured GH4C1 cells. Enzyme activity was measured in cell sonicates as the release of radioiodide from [125I]T4. Enzyme activity was stimulated 2- to 3-fold by hypothyroid serum and activators of protein kinase C, such as TRH and phorbol esters. The hypothyroid serum effect was maximal by 3 h, whereas TRH and phorbol esters required 6 h to achieve a maximal effect. The hypothyroid serum effect was gone within 4 h of returning the cells to control medium. In contrast, the TRH and phorbol ester effects persisted 24-48 h after removal of those agents. Both T4 and rT3 were at least as potent as T3 in blocking the effect of hypothyroid serum. The stimulation of 5'-deiodinase induced by hypothyroid serum was additive with that induced by kinase C activators. Trifluoperazine blocked the effect of TRH and phorbol esters, but not that of hypothyroid serum. It is concluded that stimulation of 5'-deiodinase activity can occur by at least two independent mechanisms: one involving hypothyroidism and another involving activation of protein kinase C. The relative potencies of various iodothyronines for abolishing the hypothyroid effect differ markedly from the relative binding affinities of these agents for the nuclear T3 receptor, suggesting that this thyroid hormone effect may not be mediated by the classical nuclear thyroid hormone receptor.
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PMID:Regulation of thyroxine 5'-deiodinase by thyroid hormones and activators of protein kinase C in GH4C1 cells. 300 18

Phorbols stimulated 32P incorporation into several proteins in mouse thyroid lobes. Phosphoproteins (34 K and 23 K) were detected by SDS-polyacrylamide gel electrophoresis and autoradiography. Among phorbols tested, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) was the strongest stimulator of protein phosphorylation. On the other hand, TPA at 50-200 ng/ml significantly stimulated free T3 release by mouse thyroid lobes. The stimulatory effect of TPA was not additive to that of TPA or dibutyryl cAMP. TSH stimulation of free T3 release by mouse thyroid lobes, however, was significantly inhibited by H-7 (an inhibitor of protein kinase C) at a concentration of 50 microM. These results suggest that protein kinase C may play some role in thyroid hormone secretion by phosphorylating the endogenous substrates.
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PMID:Effects of phorbol esters on protein phosphorylation and free T3 release by mouse thyroid lobes. 301 36


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