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)

Interest in the problem of anteroposterior specification has quickened because of our near understanding of the mechanism in Drosophila and because of the homology of Antennapedia-like homeobox gene expression patterns in Drosophila and vertebrates. But vertebrates differ from Drosophila because of morphogenetic movements and interactions between tissue layers, both intimately associated with anteroposterior specification. The purpose of this article is to review classical findings and to enquire how far these have been confirmed, refuted or extended by modern work. The "pre-molecular" work suggests that there are several steps to the process: (i) Formation of anteroposterior pattern in mesoderm during gastrulation with posterior dominance. (ii) Regional specific induction of ectoderm to form neural plate. (iii) Reciprocal interactions from neural plate to mesoderm. (iv) Interactions within neural plate with posterior dominance. Unfortunately, almost all the observable markers are in the CNS rather than in the mesoderm where the initial specification is thought to occur. This has meant that the specification of the mesoderm has been assayed indirectly by transplantation methods such as the Einsteckung. New molecular markers now supplement morphological ones but they are still mainly in the CNS and not the mesoderm. A particular interest attaches to the genes of the Antp-like HOX clusters since these may not only be markers but actual coding factors for anteroposterior levels. We have a new understanding of mesoderm induction based on the discovery of activins and fibroblast growth factors (FGFs) as candidate inducing factors. These factors have later consequences for anteroposterior pattern with activin tending to induce anterior, and FGF posterior structures. Recent work on neural induction has implicated cAMP and protein kinase C (PKC) as elements of the signal transduction pathway and has provided new evidence for the importance of tangential neural induction. The regional specificity of neural induction has been reinvestigated using molecular markers and provides conclusions rather similar to the classical work. Defects in the axial pattern may be produced by retinoic acid but it remains unclear whether its effects are truly coordinate ones or are concentrated in certain regions of high sensitivity. In general the molecular studies have supported and reinforced the "pre-molecular ones". Important questions still remain: (i) How much pattern is there in the mesoderm (how many states?) (ii) How is this pattern generated by the invaginating organizer? (iii) Is there one-to-one transmission of codings to the neural plate? (iv) What is the nature of the interactions within the neural plate? (v) Are the HOX cluster genes really the anteroposterior codings?
 ...
PMID:Mechanism of anteroposterior axis specification in vertebrates. Lessons from the amphibians. 135 May 31

The effects of bovine FSH-suppressing protein (FSP) or follistatin on activin- and GnRH-stimulated FSH synthesis and secretion have been studied using cultured pituitary cells from adult male Sprague-Dawley rats. Exposure to FSP (0.001-10 nM) for 3 days dose-dependently suppressed basal FSH secretion (IC50 = 146 +/- 21 pM., mean +/- SE), cellular content (IC50 = 269 +/- 8 pM) and total FSH (IC50 = 181 +/- 25 pM), with no effect on LH. Activin (0.3 nM) increased FSH secretion 2.1-fold, cellular content 1.3-fold, and total FSH 1.9-fold during a 3-day incubation, but these increases were dose-dependently inhibited by concomitant treatment with 35-kDa bovine FSP (0.1-3 nM), with complete inhibition occurring at concentrations between 1 and 3 nM. The 31- and 39-kDa forms of bovine FSP also antagonized the actions of activin. GnRH (1 nM) increased FSH secretion 1.8-fold and total FSH 1.6-fold during a 3-day incubation, effects that were dose-dependently inhibited by concomitant treatment with 35-kDa bovine FSP. The highest tested concentration of FSP (3 nM) suppressed GnRH-stimulated FSH secretion and total FSH to 59 and 57%, respectively, of the levels found in untreated cultures. All three forms of bovine FSP produced a significant inhibition of FSH secretion and total FSH stimulated by GnRH. FSP also suppressed FSH secretion and total FSH in response to activators of protein kinase C including 100 nM phorbol 12-myristate 13-acetate (43 and 59%, respectively) and 100 nM mezerein (40 and 60%, respectively). Finally, treatment of cultured pituitary cells with 35-kDa FSP at 1 and 3 nM for 3 days resulted in 21 and 24% decreases in GnRH binding sites, respectively. It is concluded that (i) FSP inhibits not only the secretion but also the synthesis of FSH induced by activin and GnRH in long-term culture, and (ii) FSP may cause its inhibitory effects on GnRH by suppression of the protein kinase C system, and possibly by reduction of GnRH binding sites.
 ...
PMID:Chronic inhibitory effect of follicle-stimulating hormone (FSH)-suppressing protein (FSP) or follistatin on activin- and gonadotropin-releasing hormone-stimulated FSH synthesis and secretion in cultured rat anterior pituitary cells. 211 27

The actions of FSH on ovarian follicular development and steroidogenesis are mediated through its binding to FSH receptors and required in the differentiation and maturation of ovarian follicles. Therefore it is clear that the ability of the gonadotropins to modulate ovarian function depends not only on the circulating levels of the gonadotropins, but also on the expression of appropriate receptor proteins by potential target cells in the ovary. We have observed a rapid and tentative down-regulation of FSH receptor mRNA after FSH treatment first time in granulosa cell culture. Using this culture cells, we investigated the mechanism of hormonal regulation of FSH receptor mRNA. The fact that both FSH and PMA show tentative down-regulation of FSH receptor mRNA suggests that these agents could be acting, at least in part, through a common mechanism, namely the activation of protein kinase C. Indeed, a role of the C kinase in cellular responses to hCG and TSH is consistent with findings that exposure to hCG or TSH stimulate the accumulation of inositol phosphates in nongonadal cells transfected with LH or TSH receptor. Activin, a stimulator or FSH secretion from the cultured pituitary cells, has been isolated from the mammalian follicular fluids and found to be a dimer of beta-subunits of inhibin. Activin has been shown to induce FSH receptor expression and FSH receptor mRNA on cultured rat granulosa cells. Since activin alone did not increase intracellular cAMP accumulation, to further clarify the role of activin and cAMP in the induction of FSH receptors, we examined the interactive effect of activin with cAMP on the induction of FSH receptors on cultured rat granulosa cells by 125I-FSH binding analysis. We have shown activin can up-regulate the expression of FSH receptor mRNA and protein by increasing both stability of mRNA and transcription rate. Using the cDNA clones of activin receptor type I and II, we have shown that both receptors are expressed in this cultured cells. This fact indicates that activin acts through autocrine/paracrine mechanism. On the other hands, follistatin can decrease the number of FSH binding sites elevated by addition of activin. Therefore, we examined the effects of endocrine manipulations (cAMP and PMA), FSH and activin, that are known to modulate granulosa cell function, on the follistatin productions. According to our data, these factors stimulate the production of follistatin mRNA in this cell culture, particularly the effect of activin on the follistatin mRNA indicates that the existence of negative regulation of activin effect by activin itself.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:[The regulation of gonadotropin receptor by the nonsteroidal intraovarian regulatory molecules during ovarian folliculogenesis]. 759 84

The regulation of the follistatin mRNA by hormones and endocrine manipulations was examined in granulosa cell cultures. The follistatin mRNA accumulation was stimulated in a dose-dependent manner by follicle-stimulating hormone (FSH) with a maximal response twice as great as in control cultures at a dose of 100 ng/ml FSH. The time course of the FSH effect on follistatin mRNA had a biphasic effect in which FSH increased follistatin mRNA within 2 h, and subsequently reduced it to below the control level. 8-Br-8 brom-adenosine 3,5-cyclic monophosphate (cAMP) (2 mM) and phorbol 12-myristate 13-acetate (PMA) (10 nm) induced a time-dependent increase in follistatin mRNA levels, with the maximal response at 6 h and 2 h, respectively. Co-treatment of the granulosa cells with cAMP and PMA demonstrated that 0.2 mM of 8-Br-cAMP suppressed the follistatin mRNA of the control and the samples with a small amount of PMA in the granulosa cells. Follistatin expression is therefore regulated by protein kinase A and protein kinase C pathways in rat granulosa cells. A more dramatic stimulation of follistatin mRNA was observed when this culture was treated with activin, and follistatin also blocked the effect of activin on the follistatin mRNA.
 ...
PMID:Regulation of follistatin messenger ribonucleic acid in cultured rat granulosa cells. 766 79

Follistatin is a 35-kilodalton monomer isolated from follicular fluid that acts on pituitary gonadotropes to suppress the production of FSH. Transfection of rat granulosa cells with specific oncogenes, such as simian virus 40 (SV40) DNA and Ha-ras oncogene, leads to their immortalization concomitant with preservation of their capacity for inducible steroidogenesis. Experiments were designed to investigate the regulation of follistatin messenger RNA (mRNA) accumulation upon stimulation with forskolin, 2-O-tetradecanol-phorbol-13-acetate (TPA), FSH, and hCG in four different granulosa cell lines. Granulosa cells were transfected with SV40 DNA alone (POGS5); with SV40 DNA and Ha-ras oncogene (POGRS1); with SV40 DNA, Ha-ras oncogene, and LH/CG receptor (GLHR15); or with FSH receptor (GFSHR17) expression plasmid. Cells were cultured to reach confluence and then stimulated for 6 or 24 h with ovine FSH (oFSH; 0.004-4 nM), hCG (9 nM), forskolin (50 microM), and TPA (50 nM), alone or in combination. In the POGS5 cell line, forskolin caused a 15-fold stimulation of follistatin mRNA after 24-h incubation. The POGRS1 cell line showed a time-dependent stimulation of follistatin gene expression induced by both forskolin (5.7-fold) and TPA (9.4-fold). In the GFSHR17 cells, forskolin, oFSH, and TPA induced an increase in follistatin mRNA. When oFSH (1.6 nM) was added to cells treated with forskolin (50 microM) or TPA (50 nM), no additional stimulation was observed. The GLHR15 cell line treated with hCG showed a 2.7-fold increase in follistatin mRNA accumulation within 6 h. Our data demonstrate that 1) follistatin mRNA is detectable and induced by forskolin and TPA in transformed granulosa cell lines that do not express the FSH or LH receptors; 2) in the GFSHR17 cell line, FSH, forskolin, and TPA caused a time- and dose-dependent regulation of the gene; and 3) follistatin gene expression is up-regulated by hCG in the GLHR15 cell line. We conclude that these transformed steroidogenic cell lines can serve as a useful model to study the regulation of follistatin gene expression, a peptide known to regulate pituitary and ovarian hormone secretion and differentiation of granulosa cells by its activin-binding action. Moreover, this gene can be regulated in immortalized granulosa cells by both the protein kinase A and protein kinase C pathways, although these cells express the large T antigen and the Ha-ras oncogenic proteins.
 ...
PMID:Regulation of follistatin messenger ribonucleic acid in steroidogenic rat granulosa cell lines. 778 14

Inhibins and activins are dimeric peptide hormones that regulate the circulating levels of follicle-stimulating hormone (FSH). In turn, FSH stimulates inhibin gene expression in the ovarian follicle; studies to date suggest that this effect is mediated by cAMP and that a cAMP-responsive element, identified in the 5'-flanking region of the alpha-inhibin gene, at least partially effects this response. To explore further the transcriptional regulation of the inhibin/activin genes, we have isolated and sequenced the 5'-flanking regions of the bovine alpha-, beta A- and beta B-inhibin/activin subunit genes and have analysed these regions by primer-extension analysis and DNase I footprinting with the transcription factor AP-2. Analyses indicated that all three gene promoter regions have a number of AP-2-binding sites that are resistant to competition by poly(dI-dC), suggesting that cAMP may control the inhibin/activin ratio by operating through alternative signal-transduction pathways or that inhibin/activin gene expression may be controlled by signals operating through the protein kinase C pathway. A comparison of the DNA sequences protected by AP-2 against DNase I digestion revealed a consensus AP-2-binding site of 5'-GSCCCDSS-3', where S represents a base pairing involving three (C or G) hydrogen bonds and D represents any base other than C. The nucleotide sequences of the bovine beta-subunit structural genes also are reported.
 ...
PMID:Genomic cloning and sequence analyses of the bovine alpha-, beta A- and beta B-inhibin/activin genes. Identification of transcription factor AP-2-binding sites in the 5'-flanking regions by DNase I footprinting. 781 65

The production of inhibin/activin by cultured rat anterior pituitary cells was evaluated using specific antisera to inhibin/activin alpha, beta A, and beta B subunit proteins (anti-alpha, anti-beta A, and anti-beta B). Cellular or secreted proteins recognized by the antisera were immunoprecipitated from metabolically labeled cells then analyzed by denaturing polyacrylamide gel electrophoresis. Immunoreactive inhibin/activin beta B proteins were visualized in both cell lysates and the media. Experiments with anti-beta B confirmed that activin-B (beta B beta B) is a local secretory product of cultured rat anterior pituitary cells. The secreted beta B-immunoreactive protein band had an apparent size of 24-25 kilodaltons (kDa) or 14-15 kDa, consistent with the size of unreduced beta B dimer or reduced monomer, respectively. Cell lysates contained two proteins that were specifically immunoprecipitated by anti-beta B. One of these had a mobility of greater than 95 kDa (unreduced) or 55-60 kDa (reduced), probably representing dimers or monomers of the beta B precursor, respectively. The second 14- to 15-kDa (reduced and unreduced) immunoreactive beta B protein band was verified to be the mature beta B monomer. Mature heterodimeric inhibin-B (alpha beta B) was not detected by either anti-alpha or anti-beta B. Multiple protein species, however, were observed to be specifically immunoprecipitated by incubation of cell lysates with anti-alpha. Mature beta A monomer was not detected in any of the samples. The regulation of cellular beta B production was monitored by evaluating its rate of synthesis in pulse-labeled cells. Treatment with either forskolin or 12-O-tetradecanoylphorbol acetate enhanced the rate of [35S]cysteine incorporation into the cellular 14- to 15-kDa beta B monomer, indicating that the activation of either protein kinase A or protein kinase C regulates its production. The rate of cellular beta B accumulation was also regulated by activin-A, inhibin-A, and follistatin; activin-A caused a 30% inhibition in contrast to the 70% stimulation by treatment with either inhibin-A or follistatin. Equimolar concentrations of activin-A and follistatin prevented the net effect produced by either factor alone. None of the immunoreactive alpha-forms was detectable under similar pulse-labeling conditions, and there was no apparent change in their level after labeling to equilibrium (up to 48 h). The observed changes in beta B accumulation may, therefore, reflect the regulated production of pituitary activin-B. Taken together, these results suggest that locally produced activin-B or gonadal activins exert an inhibitory tone on the production of pituitary activin-B and that this negative-feedback control is in turn modulated by inhibins and follistatins. The relative importance of pituitary and gonadal activins, inhibins, and follistatins in the proposed regulatory loop remains to be established.
 ...
PMID:Characterization and the regulation of inhibin/activin subunit proteins of cultured rat anterior pituitary cells. 824 76

The activin-binding protein, follistatin (FS), was immunoprecipitated from metabolically labeled rat anterior pituitary cells or their media using a specific antiserum to purified porcine FS (anti-FS). Several immunoreactive proteins, including one that had a mobility in the range of 42-44 kilodaltons (kDa), were detected in the cell lysates. When immunoprecipitates of the culture medium were subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis, a broad 35- to 46-kDa or 39- to 53-kDa band was visualized under unreducing or reducing conditions, respectively. Upon deglycosylation by treatment with N-glycosidase-F, the secreted product migrated as a sharp protein band with an apparent size of 35 kDa. The identity or the relatedness of the immunoprecipitated proteins to FS was verified by the ability of the C-terminally truncated form of recombinant human FS (rhFS288) to compete for binding to anti-FS. When the cultured rat anterior pituitary cells were treated with either forskolin or 12-O-tetradecanoylphorbol acetate, the accumulation of FS in the culture medium was stimulated by approximately 2.5-fold. These observations suggest that the activation of either the protein kinase A or the protein kinase C signaling pathway has a stimulatory effect on anterior pituitary FS production. A more dramatic stimulation of FS secretion (up to 7-fold) was observed when the rat anterior pituitary cells were treated with activin-A. The concentration dependence for this effect was within the same range that has been reported for most of the actions of activin-A. Inhibin-A suppressed basal FS secretion and blocked its stimulation by activin-A. To determine if locally produced FS exerts an influence on the response of gonadotropes to activins, the effects of anti-FS on FSH secretion were monitored. The ability of this FS antiserum to immunoneutralize the activity of FS was initially confirmed; anti-FS attenuated the inhibitory action of exogenous follistatin on FSH secretion. Treatment of cells with the antiserum increased the apparent sensitivity of gonadotropes to submaximal concentrations of activin-A. Moreover, the presence of the antiserum lowered the concentration of activin-A that was required to produce the maximum amount of FSH secretion, without changing the magnitude of the response. These results suggested that locally produced FS interferes with the secretory response of gonadotropes to activins. Changes in locally secreted FS may, therefore, represent a mechanism by which the response of rat anterior pituitary cells to incoming stimuli are tightly regulated.
 ...
PMID:Activin-A regulates follistatin secretion from cultured rat anterior pituitary cells. 824 77

Follistatin, activin and inhibin proteins are produced by granulosa cells, but the mechanisms controlling their production remain unclear. Here, we examined how the protein kinase A (PKA) and protein kinase C (PKC) pathways act and interact to regulate production of these proteins. Granulosa cells from immature rats were cultured with activators of the PKA pathway (100 ng/ml FSH, 10 microM forskolin) and/or activators of the PKC pathway (100 nM GnRH agonist, 100nM 2-0-tetradecanoyl-phorbol-13-acetate, TPA). Conditioned media were assayed for inhibin and activin by ligand blotting using recombinant human 125I-follistatin and for follistatin by double ligand blotting using cold activin plus 125I-follistatin. FSH and forskolin stimulated inhibin but not activin production. In contrast, GnRH and TPA stimulated activin, and to a lesser degree, inhibin production; significantly, this is the first demonstration of activin dimer production by granulosa cells. Activators of the PKA pathway antagonized the actions of PKC effectors and vice versa. All agents increased follistatin protein production, and the PKA and PKC activators interacted to generate further increases in follistatin production. These results show that the FSH-PKA signalling pathway favors formation of alpha beta inhibin dimers while the GnRH-PKC pathway favors formation of beta-subunit activin dimers. Both pathways act to increase follistatin protein production.
 ...
PMID:Differential control of activin, inhibin and follistatin proteins in cultured rat granulosa cells. 833 40

This study was undertaken to assess the role of protein kinase C (PKC) in activin action in the rat pituitary. Pretreatment with 500 nM phorbol 12-myristate 13-acetate (PMA) for 22-24 h reduced subsequent FSH and LH release (percentage of total cellular FSH and LH released) in response to 100 nM PMA. This action persisted for 2 days after the pretreatment. Pretreatment with 500 nM 4 alpha-phorbol 12,13-didecanoate (4 alpha PDD, a phorbol ester which does not activate PKC) did not affect cell responsiveness to 100 nM PMA. Both PKC-down-regulated cells and cells with a full complement of PKC responded similarly to 100 nM GnRH and 100 microM A23187 during this period. Incubation with 50 ng/ml activin A for 48 h significantly increased both FSH release and total FSH (extracellular plus intracellular) compared to corresponding basal values in PMA-pretreated cells, as well as in vehicle-or 4 alpha PDD-pretreated cells. Activin stimulation of basal FSH release and total FSH was significantly more potent in PMA-pretreated cells than in cells not pretreated with PMA. Activin did not alter basal LH release or total LH in vehicle- or 4 alpha PDD-pretreated cells but significantly increased both in PMA-pretreated cells. When PMA was present only during the initial 2 h of the 22- to 24-h pretreatment period at 50 nM, PKC was not down-regulated. In these cells, the potency of activin stimulation of basal FSH release was not affected, but stimulation of basal LH release by activin was still observed. These results suggest that PKC is not required for activin to stimulate FSH release but is involved as a modulator of potency and specificity of the activin action.
 ...
PMID:Modulation of activin A action and specificity in the rat gonadotrope by protein kinase C. 834 95


1 2 3 4 Next >>