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

Several lines of evidence indicate that estrogen inhibits parathyroid hormone (PTH)-induced bone resorption in vivo and in vitro. However, its precise mechanism remains unknown. The present study was performed to investigate whether osteoclast precursor cells possess the receptors for PTH/PTH-related protein (PTHrP) and/or estrogen and to clarify the mechanism by which estrogen affects PTH-induced osteoclast-like cell (Ocl) formation. The polymerase chain reaction (PCR) product corresponding in size to the mouse PTH/PTHrP receptor cDNA was detected in mouse hemopoietic blast cells supported by granulocyte-macrophage colony-stimulating factor (GM-CSF) as well as in osteoblastic MC3T3-E1 cells. The nucleotide sequence of the PTH/PTHrP receptor PCR product of hemopoietic blast cells was found to be 95.4% identical to that of PTH/PTHrP receptor cDNA of rat osteoblastic ROS cells. The PCR product corresponding in size to the mouse estrogen receptor cDNA was detected in mouse hemopoietic blast cells supported by GM-CSF as well as in MC3T3-E1 cells. The nucleotide sequence of the estrogen receptor PCR product of hemopoietic blast cells was completely identical to that of mouse estrogen receptor cDNA. 17Beta-estradiol (17beta-E2) but not 17alpha-E2 dose dependently antagonized Ocl formation stimulated by human (h) PTH(1-34) at a minimal effective concentration of 10(-10) M in the hemopoietic blast cell culture. 17Beta-E2 also significantly inhibited Ocl formation stimulated by 10(-8) M hPTHrP(1-34), while it did not affect 1,25-dihydroxyvitamin D3-induced Ocl formation. However, 10(-8) M 17beta-E2 significantly inhibited Ocl formation stimulated by dibutyryladenosine cAMP (10(-4) M) and Sp-cAMPS (10(-4) M), an activator of cAMP-dependent protein kinase (PKA) as well as forskolin (10(-5) M). In contrast, 17beta-E2 did not affect Ocl formation by either phorbol myristate acetate (10(-7) M), an activator of protein kinase C (PKC), or A23187 (10(-7) M), a calcium ionophore. The pretreatment with 17beta-E2 significantly inhibited Ocl formation induced by the combined treatment with PTH and PKC inhibitors (H7 or staurosporine), while it did not affect Ocl formation stimulated by the combined treatment with PTH and Rp-cAMPS, a PKA inhibitor. The present data indicate that estrogen inhibits PTH-stimulated Ocl formation by directly acting on hemopoietic blast cells, possibly through blocking a PKA pathway but not a calcium/PKC pathway.
 ...
PMID:Estrogen via the estrogen receptor blocks cAMP-mediated parathyroid hormone (PTH)-stimulated osteoclast formation. 961 Jul 50

Several reports have shown an interaction between the estrogen receptor (ER) and the protein kinase C (PKC) intracellular pathways. Data from our laboratory showed that PKC activation can modulate ER levels and responsiveness in estrogen target tissues such as uterus and bone. In particular, ROS.SMER #14 osteoblastic cells, stably transfected with the mouse ER, undergo specific morphological changes in vitro. ROS.SMER #14 cells at post-confluence express a differentiated phenotype and become unresponsive to estrogenic stimulation. Interestingly, ER mRNA and protein levels were not modified by post-confluence, but ER binding sites/cell (2500-3000/cell at subconfluence) were undetectable. Moreover, PKC activity was significantly increased in post-confluent cells. Inhibition of PKC by H7 or staurosporin (PKC inhibitors) or down-regulation by long-term treatment with 12-O-tetradecanoylphorbol-13-acetate enchanced ER binding capacity in a dose-dependent manner. Since the PKC family includes several different isoforms that play different roles in cell homeostasis, we evaluated whether specific isoenzymes were involved in this event. To address this question, Western blotting analysis was performed on both sub- and post-confluent ROS.SMER #14 cells using antibodies against different PKC isoforms. In conclusion, our preliminary data indicate that estrogen responsiveness of osteoblastic cells can be highly regulated by PKC. Finally, these data suggest that this intracellular interaction might play an important role in modulating hormonal and pharmacological responsiveness of bone tissue.
 ...
PMID:Protein kinase C modulates estrogen receptors in differentiated osteoblastic cells in vitro. 961 1

The role of female hormones in the prevalence of cardiac diseases are recognized but not fully explored. Proliferation of cardiac fibroblasts, the cellular origin of the extracellular matrix proteins, growth factors and cytokines in the heart, is an important underlying mechanism in the pathophysiological remodeling of the myocardium. In this study, we have investigated the effect of estrogen (17 beta-estradiol) on proliferative capacity of cardiac fibroblasts obtained from adult female rat heart. DNA synthesis, as determined by incorporation of 3H-thymidine into DNA, increased in estrogen-treated cells. In the presence of tamoxifen, an anti-estrogen with high affinity for estrogen receptor. 17 beta-estradiol-induced stimulation of DNA synthesis was abolished. Alpha-estradiol, a stereo-isomer which does not bind the estrogen receptor, did not change DNA synthesis. In the presence of a synthetic inhibitor of MAP kinase pathway. PD98059, estrogen failed to stimulate DNA synthesis. In-gel kinase assays showed rapid and transient increased phosphorylation of MAP kinase substrate, myelin basic protein (MBP), at 42 and 44 kDa by 17 beta-estradiol, which was not observed in the presence of PD98059 and tamoxifen, not induced by alpha-estradiol and persisted in the absence of protein kinase C. In vitro kinase assay confirmed 17 beta-estradiol-induced activation of ERK1 and ERK2, with predominant effect on ERK2 in cardiac fibroblasts. The results of immunofluorescent light microscopy using anti-type alpha and beta estrogen receptor antibodies showed the expression of estrogen receptor types alpha and beta in control untreated cells, and indicated that type beta receptor is the predominant type with both cytoplasmic and nuclear localization. 17 beta-estradiol treatment of cardiac fibroblasts induced the translocation of receptor protein to the nuclei. Together, these data provide evidence that cardiac fibroblasts are cellular targets for direct effects of estrogen, and that this hormone enhances proliferative capacity of cardiac fibroblasts via estrogen receptor- and MAP kinase-dependent mechanisms. These data further suggest that estrogen, by its growth-enhancing effects in cardiac fibroblasts, can regulate the remodeling of the extracellular matrix and alter the microenvironment of cardiac cells, and hence exert an impact on the integrity of myocardial function.
 ...
PMID:Estrogen enhances proliferative capacity of cardiac fibroblasts by estrogen receptor- and mitogen-activated protein kinase-dependent pathways. 971 Aug 4

Tamoxifen, a synthetic antiestrogen, is known for its antitumoral action in vivo; however, it is well accepted that many tamoxifen effects are elicited via estrogen receptor-independent routes. Previously, we reported that tamoxifen induces PKC translocation in fibroblasts. In the present study, we investigated the influence of tamoxifen, and several triphenylethylene derivatives, on protein kinase C (PKC) in MCF-7 human breast cancer cells. As measured by Western blot analysis, tamoxifen elicited isozyme-specific membrane association of PKC-epsilon, which was time-dependent (as early as 5 min post-treatment) and dose-dependent (5.0-20 microM). Tamoxifen did not influence translocation of alpha, beta, gamma, delta or zeta PKC isoforms. Structure-activity relationship studies demonstrated chemical requirements for PKC-epsilon translocation, with tamoxifen, 3-OH-tamoxifen and clomiphene being active. Compounds without the basic amino side chain, such as triphenylethylene, or minus a phenyl group, such as N,N-dimethyl-2-[(4-phenylmethyl)phenoxy]ethanamine, were not active. In vitro cell growth assays showed a correlation between agent-induced PKC-epsilon translocation and inhibition of cell growth. Exposure of cells to clomiphene resulted in apoptosis. Since PKC-epsilon has been associated with cell differentiation and cellular growth-related processes, the antiproliferative influence of tamoxifen on MCF-7 cells may be related to the interaction with PKC-epsilon.
 ...
PMID:Tamoxifen induces selective membrane association of protein kinase C epsilon in MCF-7 human breast cancer cells. 971 66

Susceptibility to drug-induced coronary vasospasm in rhesus monkeys increases after removal of the ovaries and can be normalized by adding back physiological levels of estradiol-17ss (E2) and/or natural progesterone (P) in vivo as reported recently by our group. Furthermore, the reactivity status (Ca2+ and protein kinase C responses) of freshly isolated and primary culture coronary artery vascular muscle cells (VMC) mimic the intact coronary artery responses to 5-HT + U46619. Since coronary reactivity is maintained in the isolated VMC, we hypothesized that the reactivity state inherent in the VMC was modulated directly by ovarian steroids in vitro as in the whole animal. To test this hypothesis, we treated hyperreactive VMC from ovariectomized (ovx) monkeys in vitro with E2 or P and measured VMC reactivity to combined stimulation with 5-HT and U46619, as determined by the amplitude and especially the duration of intracellular Ca2+ signals, as well as protein kinase C (PKC) activation/translocation. VMC were treated for 12 96 h with 3 100 pg/ml E2 (10 365 pM) and/or 0.3 3 ng/ml P (0.95 9.5 nM). Hyperreactive responses to the combination of 5-HT and U46619 in untreated VMC were significantly and dose-dependently reduced by treatment in vitro with physiological levels of either E2 or P for at least 24 h. Both the early transient and late sustained increases in intracellular Ca2+ and PKC translocation were blunted, and the effects of 0.2 nM E2 and 3.2 nM P were specifically antagonized by the receptor blockers ICI 182,780 (200 nM) and RU486 (15 nM), respectively. Antibodies to the estrogen receptor and progesterone receptor labeled nuclei in VMC, which were also positively labeled by a smooth muscle myosin heavy chain monoclonal antibody. These data indicate that natural ovarian steroids directly reduce hyperreactive 5-HT and thromboxane A2-stimulated Ca2+ and PKC responses of coronary artery VMC from surgically menopausal rhesus macaques. We hypothesize that vascular hyperreactivity, which may be a critical factor involved in the increased incidence of coronary artery vasospasm and ischemic heart disease in postmenopausal women, can be normalized by E2 and/or P through direct actions on coronary artery vascular muscle cells.
 ...
PMID:In vitro modulation of primate coronary vascular muscle cell reactivity by ovarian steroid hormones. 976 86

We have recently shown that protein kinase C (PKC) modifies estrogen receptor (ER) binding and modulates the responsiveness to estrogens in a clonal osteoblast-like cell line stably transfected with the ER. The purpose of the present study was to determine whether the interaction observed between the ER and PKC signaling in these cells occurs in additional estrogen target organs, such as the uterus. When uteri were incubated for 2 h with increasing concentrations of a kinase inhibitor (H7), ER binding was enhanced in a dose-dependent manner. Stimulation of PKC with phorbol ester reduced PKC activity levels, but increased ER binding. Interestingly, the changes in binding appeared to be due primarily to alterations in cytosolic ER levels, as binding in the nuclear fraction was minimally enhanced. When levels of ER messenger RNA were evaluated by Northern blot analysis, no differences were observed among the H7- or 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated and untreated groups. Western blot analysis, however, demonstrated that levels of ER cytosolic protein in the H7-, TPA-, and staurosporine-treated groups were increased relative to those in the untreated controls. When uteri were incubated with diethylstilbestrol in the presence of either H7 or TPA, no change in cytosolic ER levels was found, suggesting that only unoccupied ERs are responsive to modulation by PKC. Western blotting of the various PKC isoforms indicated that although PKC alpha, -beta1, -betaII, -delta, and -zeta are expressed in the uterus, only PKC alpha and -beta1 are translocated from the soluble to the particulate fraction and then degraded after phorbol ester stimulation. Hence, one or both of these latter PKC isoforms may regulate cytosolic ER levels. Collectively, these data indicate that PKC may play an important role in the modulation of uterine ER levels and that PKC may exert its effect on the ER at some posttranscriptional or posttranslational step. Finally, our results show that an ER-PKC interaction occurs in a whole organ such as the uterus and that this interaction may be important in the regulation of the ER activity in a variety of estrogen-responsive tissues.
 ...
PMID:Modulation of estrogen receptor levels in mouse uterus by protein kinase C isoenzymes. 979 71

Endothelial cell function is regulated by interactions among cells, the extracellular matrix (ECM), and soluble mediators. We investigated this interaction by examining the effect of 17beta-estradiol (E2) on release of basic fibroblast growth factor (FGF-2) by human coronary artery endothelial cells (HCAEC) cultured on ECM proteins. After estrogen-depleted HCAEC were treated with E2 for 2 h, the conditioned media and cell layers were evaluated by immunoblot or ELISA for FGF-2. Release of FGF-2 into conditioned media was enhanced 10-fold compared to that on plastic and a further 2.4-fold by E2. As FGF-2 release from cells into the media increases, there is a corresponding decrease in the cellular content of FGF-2. By ELISA, FGF-2 release increased 406, 179, and 262%, on type IV collagen, laminin, or fibronectin, respectively. HCAEC cultured on type I collagen did not show E2-enhanced FGF-2 release by ELISA or immunoblot analysis. No changes were noted in HCAEC release of lactate dehydrogenase, tested as a control protein for cellular integrity. The estrogen receptor antagonist ICI182,780 blocked E2-induced, but not basal, FGF-2 release. Increased FGF-2 release occurred via a cycloheximide-insensitive pathway. Neither brefeldin-A nor genistein inhibited E2 enhancement of FGF-2 release by HCAEC cultured on fibronectin. However, the protein kinase C inhibitor calphostin C inhibited the E2-augmented FGF-2 release. These data show that E2 enhances FGF-2 release by HCAEC cultured on basement membrane proteins in the absence of wounding. This action requires the estrogen receptor and PKC activity, but does not require new protein synthesis, endoplasmic reticulum-to-Golgi-mediated secretion, or protein tyrosine phosphorylation. E2-enhanced FGF-2 release could contribute to the cardioprotective effects of estrogen.
 ...
PMID:Basic fibroblast growth factor release by human coronary artery endothelial cells is enhanced by matrix proteins, 17beta-estradiol, and a PKC signaling pathway. 982 12

We have investigated whether the raf-1 kinase, a downstream mediator of both receptor tyrosine kinase and protein kinase C signalling, is activated by estrogen (E2) in an estrogen receptor positive human breast cancer cell line. Autophosphorylation of raf-1 kinase was studied after treatment of MCF-7 cells with E2. E2-deprived cells contained low levels of raf-1 kinase activity. Treatment of cells for 1 min with E2 resulted in raf-1 autophosphorylation which was maximal within 5 min. Western blot analysis showed that raf-1 undergoes an electrophoretic mobility shift following E2 treatment. Egr-1 is a zinc finger-containing transcription factor which is expressed in association with raf-1 activation. Untreated MCF-7 cells expressed low levels of Egr-1 while E2 treatment resulted in an induction of egr-1 mRNA expression. These kinetics followed closely behind the E2 induction of c-myc mRNA. Egr-1 protein was similarly low in E2-deprived MCF-7 cells and was transiently increased following E2 treatment. Several studies have suggested that kinase activity may play a role in estrogen receptor (ER) activation. While activated v-raf failed to augment ER activation of transcription in transient transfection assays, a dominant negative mutant of raf-1 inhibited E2-induced transcription by 50% primarily as a result of increased baseline levels of E2 independent transcription. The results show that E2 can induce raf-1 kinase activity in MCF-7 breast cancer cells associated with the expression of an early growth response gene and modulation of ER signalling.
 ...
PMID:Estrogen activates raf-1 kinase and induces expression of Egr-1 in MCF-7 breast cancer cells. 987 62

In an attempt to find the key to reducing the excessive morbidity and mortality seen with mood disorders, our laboratory has been extensively investigating lithium's mechanisms of action in an integrated series of clinical and preclinical studies. We have found that the chronic administration of the 2 structurally highly dissimilar agents, lithium and valproate, brings about a strikingly similar reduction in protein kinase C (PKC) alpha and epsilon isozymes in rat frontal cortex and hippocampus. In view of PKC's critical role in regulating neuronal excitability and neurotransmitter release, we have postulated that PKC inhibition may have antimanic efficacy. In a small study, we have found that tamoxifen (which, in addition to its estrogen receptor blockade, is also a PKC inhibitor) has marked antimanic efficacy. These exciting preliminary results suggest that PKC inhibitors may represent a novel class of improved therapeutic agents for bipolar disorder, and this is under further investigation. The beneficial effects of mood stabilizers require a lag period for onset of action and are generally not immediately reversed upon drug discontinuation; such patterns of effects suggest alterations at the genomic level. We have therefore undertaken a series of studies to investigate the effects of these agents on the AP-1 family of transcription factors and have found that both drugs increase AP-1 DNA binding activity in areas of rodent brain ex vivo and in human neuronal cells in culture. Both treatments also increase the expression of a reporter gene driven by an AP-1-containing promoter, and mutations in the AP-1 sites of the reporter gene promoter markedly attenuate these effects. Both treatments also increase the expression of several endogenous proteins, whose genes are known to be regulated by AP-1. Although the precise mechanisms have not been fully elucidated, preliminary results suggest that these effects may be mediated, in part, by mitogen-activating protein kinases and glycogen synthase kinase 3beta. We have also utilized mRNA reverse transcription-polymerase chain reaction (RT-PCR) differential display to identify concordant changes in gene expression induced by the chronic administration of both lithium and valproate. We have identified concordant changes in a number of cDNA bands by both lithium and valproate. Cloning and characterizing of these genes is currently underway. The identification of the functions of these genes offers the potential not only for improved therapeutics for reducing the morbidity and mortality associated with mood disorders, but may also provide important clues about the underlying pathophysiology.
 ...
PMID:Modulation of CNS signal transduction pathways and gene expression by mood-stabilizing agents: therapeutic implications. 1007 85

We have previously shown that estrogen up-regulates expression of protein kinase C (PKC) delta in the rat and rabbit corpus luteum as well as in luteinized rat granulosa primary cell cultures. To determine whether a similar regulation of the PKC delta isoform by estrogen occurred in another estrogen responsive system, we investigated the estrogen receptor positive MCF-7 human breast cancer cells. In a characterization of PKC isoforms in MCF-7 cells we determined that PKC delta was the predominant PKC isoform. However in contrast to the effect of estrogen on PKC delta expression in ovarian cells, estrogen treatment of MCF-7 cells resulted in a significant decrease in PKC delta protein and mRNA expression in a time and dose dependent manner. Treatment of MCF-7 cells with 10(-10)-10(-8) M estrogen for 7 days down-regulated specifically PKC delta mRNA and protein while expression of other PKC isoforms was unchanged. The opposite regulation of PKC delta expression in ovarian and breast cancer cells prompted us to evaluate the type of estrogen receptor present in both cell types. Results showed that luteinized rat granulosa cells expressed predominantly estrogen receptor beta while the MCF-7 cells expressed predominantly estrogen receptor alpha and barely detectable levels of estrogen receptor beta. These results suggest that the differential ability of estrogen to regulate PKC beta expression could potentially be a result of differential signaling through the two estrogen receptor subtypes.
 ...
PMID:Regulation of protein kinase C delta by estrogen in the MCF-7 human breast cancer cell line. 1022 76


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