Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neuropeptides such as gastrin releasing peptide and pituitary adenylate cyclase activating polypeptide (PACAP) stimulate CCK secretion from CCK producing cells. We hypothesized that in addition to somatostatin, galanin may also play an inhibitory role on CCK secretion. The effect of galanin on CCK secretion was studied in a CCK-producing murine neuroendocrine tumor cell line, STC-1. Galanin below 10 nM did not affect basal CCK secretion but dose- and time-dependently inhibited KCl-stimulated CCK secretion. Galanin also inhibited forskolin-, bombesin- and PACAP- but not dibutyryl cAMP- or beta-TPA-stimulated CCK secretion. The inhibitory effect of galanin was reduced partially by a blocker of ATP-sensitive K+ channel (K+ ATP), glibenclamide, and prevented by pretreatment of the cells with PTX. The results indicated galanin regulates CCK secretion by modulation of K+ ATP and cAMP production through receptors coupled to a PTX-sensitive G protein.
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PMID:Galanin inhibits cholecystokinin secretion in STC-1 cells. 748 89

Isolated sheep thyroid follicles release insulin-like growth factors (IGF)-I and -II together with IGF-binding proteins (IGFBPs). We previously showed that TSH suppresses the biosynthesis and release of IGFBPs in vitro which may increase the tissue availability of IGFs, allowing a synergy with TSH which potentiates both thyroid growth and function. Many of the actions of TSH on thyroid cell function are dependent upon activation of adenylate cyclase, although increased synthesis of inositol trisphosphate and activation of protein kinase C (PKC) have also been implicated. We have now examined whether probable changes in intracellular cyclic adenosine monophosphate (cAMP) or PKC are involved in TSH-mediated suppression of IGFBP release. Confluent primary cultures of ovine thyroid cells were maintained in serum-free Ham's modified F-12M medium containing transferrin, somatostatin and glycyl-histidyl-lysine (designated 3H), and further supplemented with sodium iodide (10(-8)-10(-3) mol/l), dibutyryl cAMP (0.25-1 mmol/l), forskolin (5-20 mumol/l) or 12-O-tetradecanoylphorbol-13-acetate (TPA; 10(-11)-10(-6) mol/l), with or without exposure to TSH (200 microU/ml). The uptake and organification of Na [125I] by cells was examined after test incubations of up to 48 h, and IGFBPs in conditioned media were analysed by ligand blot using 125I-labelled IGF-II. The PKC activity in the cytosol and plasma membrane fractions of cells was measured by phosphorylation of histone using [gamma-32P]ATP, and PKC immunoreactivity was visualized by Western immunoblot analysis. While dibutyryl cAMP or forskolin largely reproduced the stimulatory effect of TSH on iodine organification, they did not mimic the inhibitory effect of TSH on the secretion of IGFBPs of 43, 34, 28 and 19 kDa. Incubation with physiological or pharmacological concentrations of iodide (10(-6)-10(-3) mol/l) for up to 48 h significantly decreased TSH action on iodide uptake and organification but did not alter the inhibitory action of TSH on IGFBP release. Incubation of cells with 10(-11)-10(-6) mol TPA/l for 24 h inhibited the subsequent ability of TSH both to potentiate iodine organification and to suppress IGFBP release. In 3H medium, PKC activity was predominantly recovered from the membrane fraction but, following incubation for 48 h with TSH, the enzyme was no longer translocated to the membrane and was recovered predominantly from the cytosol.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Role of 3', 5' cyclic adenosine monophosphate and protein kinase C in the regulation of insulin-like growth factor-binding protein secretion by thyroid-stimulating hormone in isolated ovine thyroid cells. 751 34

We have previously shown that a Long Terminal Repeat (LTR) of the Intracisternal A-type Particle (IAP) element was activated by ras oncogenes. Here we show that, like the somatostatin CRE (som CRE) and the collagenase TPA Response Element (coll TRE), the IAP CRE is activated by c-jun and that Val 12 Ha-ras cooperates with c-jun to activate these motifs. Neither jun-B nor jun-D activated the IAP CRE, although they were able to act on the som CRE and the coll TRE and to synergize with ras. The CREB factor activated both CREs and modestly inhibited the coll TRE, but diminished the effect of ras on the coll TRE. Finally, forskolin was shown to cooperate with Ha-ras to activate the CRE and the coll TRE. Taken together, these results show that CREB is not involved in ras activation of the CRE and suggest that c-jun is at least one of the elements implicated in this phenomenon.
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PMID:Differential effects of c-jun and CREB on c-AMP response element activation by Ha-ras. 790 82

Several promoter elements with sequence similarity to the prototype TPA-responsive element (TRE) were compared by mobility-shift analyses. Activities within whole cell extracts were identified that bind to the TRE-like elements in the collagenase, the somatostatin, and the c-jun promoters. The corresponding factors appeared to differ in their degree of selectivity for these TRE-like sequences. One protein species bound equally well to all TREs. In addition, a subset of specific activities recognised only the somatostatin and the c-jun-derived element and one DNA-protein complex had exclusive specificity for the TRE present in the c-jun promoter. By antibody 'supershift' assays some of the protein components of the specific complexes were identified as CREB- and ATF-related products. Based on these data we postulate that bZip protein dimers differ in their ability to tolerate variations from the canonical TRE sequence. We propose that TRE-like promoter elements are distinguished by this ability to bind to different subsets of a family of related transcription factors.
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PMID:Different TRE-related elements are distinguished by sets of DNA-binding proteins with overlapping sequence specificity. 847 9

In cultured pituitary cells of tilapia, gonadotropin-releasing hormone (GnRH; 10 nM 4-24 h), elevation of cyclic AMP (by 10 microM forskolin or 0.2 mM 3-isobutyl-1-methylxanthine: IBMX 0.5-36 h) or activation of protein kinase C (PKC; by 12.5 nM tetradecanoyl phorbol-13-acetate: TPA, 0.5-24 h) all increased gonadotropin (GtH) II beta steady state mRNA levels by three to four-fold. The involvement of PKA and PKC in the GnRH stimulatory effect on both GtH release and GtH II beta mRNA levels was corroborated by use of the PKA and PKC inhibitors, H89 and GF109203X, respectively (100 nM) which attenuated the GnRH effect. Incubation with actinomycin D (8 microM, 4-21 h) after preexposure for 24 h to either forskolin (10 microM) or TPA (12.5 nM), revealed that rates of transcript degradation were slower in forskolin-treated cells (T 1/2 = 14.1 h) than in control or TPA-treated cells (T 1/2 = 8.47 or 8.38 h), suggesting a stabilizing effect on the mRNA. Dopamine (DA; 10 microM, 4-36 h) had no apparent effect on steady state mRNA levels of GtH II beta, but reduced GtH release by as much as 75%. Steady state levels of growth hormone (GH) mRNA were not affected by exposure to GnRH (10 nM, 4-24 h), although GH release was more than doubled. Similarly, activation of PKC (by TPA 12.5 nM, 1.5-36 h), which was shown to be essential for the GnRH-stimulatory effect on GH release, did not alter levels of the GH transcript, but increased GH release by more than fivefold. DA (10 microM, 4-24 h) moderately increased GH transcript levels (160%) with similar kinetics but lower potency than direct elevation of cAMP (by 10 microM forskolin or 0.2 mM IBMX, 0.5-36 h) which increased transcript levels by more than fourfold. The involvement of PKA in the DA effect was confirmed when the PKA inhibitor H89 (100 nM, 15 min prior to DA exposure) attenuated the DA effect on GH mRNA levels. Exposure of cells to actinomycin D (8 microM, 2-16 h) after treatment with forskolin (10 microM, 24 h) led to a slower rate of transcript degradation than in control cells (T 1/2 = 6.5 h vs. T 1/2 = 4.36 h), suggesting that cAMP also elicits a stabilizing effect on GH mRNA. Somatostatin (100 nM, 0.5-36 h) had no clear effect on GH transcript levels, but reduced GH release by as much as 90%. These results suggest that activation of either cAMP-PKA or PKC pathways can, possibly by different mechanisms, stimulate mRNA levels of the GtH II beta gene, but that only the cAMP-PKA pathway stimulates GH mRNA levels. It would appear therefore that GnRH, although stimulating GH release, does not regulate GH transcription in this fish.
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PMID:Differential effects of gonadotropin-releasing hormone, dopamine and somatostatin and their second messengers on the mRNA levels of gonadotropin II beta subunit and growth hormone in the teleost fish, tilapia. 889 62

Somatostatin exerts inhibitory effects on virtually all endocrine and exocrine secretions. The somatostatin receptor subtype 2 (sst2) acts as a critical molecule for growth hormone regulation and cell proliferation. We investigated the structure and regulation of the human sst2 gene. A genomic clone including the sst2 gene was isolated, 1.5 kb of the promoter was sequenced and putative transcription factor binding sites were identified. The transcription start site was located 93 nucleotides upstream of the translation start site. The nucleotide sequences of the complete gene and 0.5 kb of 3' region were determined. A possible polyadenylation signal was identified. Transcriptional regulation was investigated by transient transfections using various promoter fragments. A -1100 sst2 promoter directed significant levels of luciferase expression in GH4 rat pituitary cells and Skut1-B endometrium cells whereas only low activity was detected in JEG3 chorion carcinoma cells or COS-7 monkey kidney cells. A minimal -252 promoter allowed cell specific expression. We did not find any regulation of the sst2 promoter by somatostatin, forskolin, TRH, TPA, T3, and 17beta-estradiol. Glucocorticoids lead to a significant inhibition of sst2 promoter activity. Further mapping suggest a glucocorticoid-responsive element between -905 and -707 and between -252 and -163. These studies demonstrate the nature of the human sst2 gene and identify its 5' and 3' flanking regions. Furthermore, specific activity of the promoter and regulation by various hormones is demonstrated.
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PMID:Genomic structure and transcriptional regulation of the human somatostatin receptor type 2. 1061 99

In mammals, growth hormone (GH) is under a dual hypothalamic control exerted by growth hormone-releasing hormone (GHRH) and somatostatin (SRIH). We investigated GH release in a pleuronectiform teleost, the turbot (Psetta maxima), using a serum-free primary culture of dispersed pituitary cells. Cells released GH for up to 12 days in culture, indicating that turbot somatotropes do not require releasing hormone for their regulation. SRIH dose-dependently inhibited GH release up to a maximal inhibitory effect of 95%. None of the potential stimulators tested induced any change in basal GH release. Also, neither forskolin, an activator of adenylate cyclase, nor phorbol ester (TPA), an activator of protein kinase C, were able to modify GH release, suggesting that spontaneous basal release already represents the maximal secretory capacity of turbot somatotropes. In contrast, forskolin and TPA were able to increase GH release in the presence of SRIH. In this condition (coincubation with SRIH), pituitary adenylate cyclase-activating polypeptide (PACAP) stimulated GH release, whereas none of the other neuropeptides tested (GHRHs; sea bream or salmon or chicken II GnRHs; TRH; CRH) had any significant effect. These data indicate that inhibitory control by SRIH may be the basic control of GH production in teleosts and lower vertebrates, while PACAP may represent the ancestral growth hormone-releasing factor in teleosts, a role taken over in higher vertebrates by GHRH.
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PMID:Pituitary growth hormone secretion in the turbot, a phylogenetically recent teleost, is regulated by a species-specific pattern of neuropeptides. 1175 94

Somatostatin (SRIF) exerts inhibitory effects on virtually all endocrine and exocrine secretions. Five distinct SRIF receptor subtypes (sst 1-5) have been identified. In contrast to the other subtypes, very little is known about specific functions of sst4. We investigated structure and regulation of the human sst4 gene. A genomic clone containing the 5' region of the sst4 gene was isolated. 1.5 kb of the promoter was sequenced and putative transcription factor binding sites were identified. The transcription start site was located 88 nucleotides upstream of the translation start site. A -984 sst4 promoter directed significant levels of luciferase expression in GH4 rat pituitary cells, Skut-1B endometrium cells, and BEAS-2B human bronchial epithelial cells, whereas only low activity was detected in JEG3 chorion carcinoma cells or COS-7 monkey kidney cells. A minimal -209 promoter allowed cell specific expression, its activity in COS-7 cells is not enhanced by co-transfection of the pituitary-specific transcription factor Pit-1. An enhancer element was localized between nt -459 and -984. We did not find any regulation of the sst4 promoter region analyzed by SRIF, forskolin, TPA, IGF-1, EGF, T3, glucocorticoids or 17beta-estradiol. These studies identify the 5' region of the sst4 gene. Furthermore, specific activity of the promoter in various cell lines is demonstrated.
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PMID:Characterization of the human somatostatin receptor type 4 promoter. 1191 48

Goldfish prolactin cDNA was subcloned into a pRSET A vector and expressed in Escherichia coli. Recombinant goldfish prolactin was expressed mainly as insoluble inclusion bodies in the form of N-terminal 6x His-tagged fusion protein. This fusion protein was purified, refolded, and (125)I-labeled to generate a radioligand for receptor binding and validation of a radioimmunoassay for goldfish prolactin. Using goldfish gill membrane as the substrate for prolactin receptor binding, both recombinant and native forms of goldfish prolactin were effective in displacing the specific binding of the radioligand in a similar dose range, suggesting that the fusion protein was refolded properly and could be recognized by goldfish prolactin receptors. To quantify prolactin contents in biological samples from the goldfish, a radioimmunoassay using the (125)I-labeled recombinant prolactin as a tracer was established. This assay was shown to be selective for goldfish prolactin without cross-reactivity with mammalian prolactin and pituitary hormones from other fish species (e.g., growth hormone and gonadotropin II). This newly validated assay system was used to investigate neuroendocrine and signal transduction mechanisms regulating prolactin release in the goldfish. In this case, the Ca(2+) ionophore A23187 and protein kinase C activator TPA were effective in elevating basal levels of prolactin secretion in perifused goldfish pituitary cells. In parallel studies using a static incubation approach, somatostatin and dopamine, but not vasoactive intestinal polypeptide, were inhibitory to basal prolactin release in goldfish pituitary cells. These results suggest that somatostatin and dopamine may serve as negative regulators of basal prolactin secretion and that extracellular Ca(2+) influx and protein kinase C activation may be important signaling events mediating prolactin release in the goldfish.
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PMID:Production of recombinant goldfish prolactin and its applications in radioreceptor binding assay and radioimmunoassay. 1194 69


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