Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is well established that dopamine (DA) effectively inhibits PRL secretion from anterior pituitary mammotropes via D2-DA receptors. Paradoxically, it is reported that the monoamine can actually increase PRL release under appropriate experimental conditions. Although the mechanism underlying this stimulatory effect remains undefined, the ability of D1- and D5-DA receptors to activate adenylyl cyclase raises the possibility that a similar receptor subtype is present in the anterior pituitary and mediates the stimulatory effects of DA on PRL release. The purpose of the present study was to explore this possibility. First, we tested whether D1 and D5 receptors could couple to and stimulate PRL secretion. Subclones of GH4C1 cells (which secrete PRL, but do not express DA receptors) stably expressing human D1 or D5 receptors were treated with DA (10(-16)-10(-6) M), and the medium PRL content was measured by RIA. Subclones transfected with short or long forms of the human D2 receptor were also tested. As expected, DA (10(-6) M) inhibited PRL release from cells expressing either short or long D2 receptors by 41% and 39%, respectively (P < 0.01; n = 4 separate experiments). In contrast, comparable concentrations of DA (10(-(8) and 10(-6) M) increased PRL release from cells expressing D1 or D5 receptors by 76% and 122%, respectively (P < 0.01; n = 4). Thus, both D1 and D5 receptors were fully capable of stimulating PRL release from transfected GH4C1 cells. We next sought to determine whether the gene for at least one of these structurally similar receptors was expressed in rat anterior pituitary tissue. First strand cDNA was synthesized, using a rat D5-specific oligonucleotide primer and reverse transcriptase, from total RNA extracted from the anterior pituitary glands of five lactating female rats. The specifically primed cDNA then served as a template for 35 cycles of polymerase chain reaction amplification in which nested primers specific for the rat D5 receptor were used. Electrophoresis of the DNA resolved a 696-basepair band corresponding to a fragment of the D5 receptor in each of five anterior pituitary samples (verified by digestion with three different restriction endonucleases). Taken together, these results demonstrate that both D1 and D5 receptors are capable of mediating the stimulatory effects of DA on PRL release and that the mRNA for DA D5 receptors is present in rat anterior pituitary glands. Our findings support the view that PRL release in vivo may be modulated via one or more stimulatory DA receptors.
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PMID:Evidence that stimulatory dopamine receptors may be involved in the regulation of prolactin secretion. 811 66

The capability of rat pituitary cells to express receptors for pituitary adenylate cyclase activating polypeptide (PACAP) and VIP was evaluated by binding studies and measurement of adenylate cyclase activity on whole gland preparations and by reverse transcriptase-polymerase chain reaction (TR-PCR) using specific primers on preparations from isolated cell populations enriched in PRL- and GH-producing cells. Data obtained on whole gland preparations indicated that selective PACAP receptors (PACAP Type I) predominated. The mRNA coding for PACAP Type I and for the non-selective PACAP receptors Type II VIP2 (but not VIP1) were identified. The mRNA coding for four different spliced variants of the PACAP Type I receptor were detected. In PRL producing cells, three variants and the VIP2 mRNA were detected, whereas in GH-producing cells the mRNA coding for the variant having a 28-amino acid insert (termed HOP) in the third intracellular loop was the only present.
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PMID:Differential alternative splicing of PACAP receptor in pituitary cell subpopulations. 867 20

Transforming growth factor-beta (TGF beta) is a member of a family of growth factors that regulates differentiation and cellular proliferation in a wide variety of tissues, including the anterior pituitary gland. TGF beta regulates the expression of various proteins, including p27Kipl (p27), a cell cycle inhibitory protein. The cell types in normal rat anterior pituitary producing TGF beta1, one of the principal isoforms of TGF beta, and p27 were examined by in situ methods. The regulation of p27 messenger RNA (mRNA) and protein by TGF beta1 was also examined in cultured anterior pituitary cells. In situ hybridization, in situ reverse transcriptase PCR, and immunocytochemical staining for pituitary hormones showed that PRL, TSH, and gonadotroph cells all had a higher percentage of cells expressing TGF beta1 mRNA and p27 protein than did GH and ACTH cells. After treatment with 10(-9) M TGF beta1 in vitro for 3 days, there were significant decreases in p27 mRNA and protein levels (P < 0.05) in normal pituitary cells. The GH3 and GHRH-CL1 cell lines, which secrete PRL and GH, had undetectable p27 protein by immunocytochemical staining and immunoblotting, although the GH3 cell line had p27 mRNA detected by reverse transcriptase PCR. Analysis of [3H]thymidine uptake in cultured dissociated pituitary cells by double staining for hormones showed that only PRL cells had significant proliferative activity during a 3-day cell culture period. There was a biphasic effect of TGF beta1 on PRL cell proliferation, with marked inhibition by 10(-9) M and a slight stimulation by 10(-13) M. These results indicate that there is a differential distribution of both TGF beta1 and p27 in various anterior pituitary cell types and that TGF beta1 directly down-regulates p27 in cultured anterior pituitary cells.
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PMID:Transforming growth factor-beta and p27 expression in pituitary cells. 877 Sep 31

The primary sequence of the prolactin receptor (PRL-R) in turkeys was deduced from a cDNA clone isolated from a kidney cDNA library and from a polymerase chain reaction (PCR) product. The open reading frame of the turkey PRL-R (tPRL-R) predicted an 831-amino acid protein composed of a leader peptide, an extracellular domain, a single transmembrane domain, and an intracellular domain. The extracellular domain contained two homologous repeat units with 63% amino acid sequence identity to each other. Each repeat unit contained all of the conserved cysteine pairs and a WSXWS motif found in mammalian PRL-Rs. A tPRL-R transcript with a molecular size of about 3000 nucleotides was identified by Northern blot analysis. The tPRL-R transcripts were detected in all 26 tissues examined using reverse transcriptase PCR (RT-PCR). The pituitary gland, hypothalamus, crop sac, duodenum, and gizzard were found to express the highest levels of tPRL-R among the 26 tissues. The expression levels of tPRL-R in 17 tissues were compared using semi-quantitative RT-PCR in nonphotostimulated, laying, out-of-lay, incubating, and maternal hens, and male birds. In most tissues examined there was no obvious relationship between blood levels of PRL, reproductive states, and estimated concentrations of the receptor mRNA. In the pituitary gland and hypothalamus, plasma levels of PRL and levels of tPRL-R transcript were inversely correlated. In the hypothalamus, increasing blood levels of PRL were associated with decreasing levels of the receptor transcript (p < or = 0.05), whereas the opposite was observed in the pituitary gland (p < or = 0.05). These findings support the hypothesis that PRL itself may participate in the neuroendocrine control of incubation behavior through actions on both the hypothalamus via a short-loop feedback mechanism and the pituitary gland via autocrine and/or paracrine effects.
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PMID:Molecular cloning, tissue distribution, and expression of the prolactin receptor during various reproductive states in Meleagris gallopavo. 890 21

To examine the existence of PRL messenger ribonucleic acid (mRNA) in the mouse placenta during late pregnancy, reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blot analysis were carried out followed by nucleotide sequence analysis of cDNA. Total RNA extracted from each tissue was reverse-transcribed, followed by PCR with two oligonucleotide primers specific or a part of mouse PRL (mPRL) cDNA. An amplified RT-PCR product of predicted size was detected in all samples from the placenta of days 16 and 18 pregnant mice. This product was specifically hybridized with a probe overlapping an entire sequence of mPRL cDNA in Southern blot analysis. Nucleotide sequence analysis also provided evidence that the amplified cDNA had a nucleotide sequence completely identical to the mPRL cDNA sequence reported previously. Furthermore, mPRL with a slightly bigger molecular weight than that of pituitary PRL was detected in the placenta of days 12, 14, 16 and 18 pregnancy by immunoblot analysis. These results suggest that PRL mRNA and its translation product are synthesized in mouse placenta during late pregnancy.
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PMID:Expression of prolactin gene in mouse placenta during late pregnancy: detection of mRNA and its translation product. 915 29

This study examined the responsiveness of dopaminergic neurons to PRL and the expression of PRL receptors in fetal hypothalamic cells. Hypothalamic cells were cultured in medium containing 5 or 25 mM potassium (K+) with or without 5% FBS. Rat PRL (rPRL) treatment (10-1000 ng/ml) for 10 days increased tyrosine hydroxylase (TH) activity 1.6- to 1.8-fold in dopaminergic neurons cultured in serum-containing medium with 25 mM K+, but not in defined medium or any medium with 5 mM K+. The rPRL-induced increase in TH activity was observed at 10-1000 ng/ml after both 1 and 10 days of rPRL treatment, whereas 1 ng/ml was not effective. TH activity was not altered after 1-12 h of rPRL treatment (100 ng/ml), but was increased 1.4-fold after 1-3 days and 1.8-fold after 5-10 days. The colocalization of PRL receptors and TH was evaluated by double labeled immunocytochemistry. PRL receptor immunostaining was observed in most TH-immunoreactive cells cultured in either defined or serum-containing medium with or without 10 days of rPRL treatment (100 ng/ml). As assessed by reverse transcriptase-PCR, the long form, but not the short form, of the PRL receptor was expressed in the hypothalamic cells regardless of medium composition, similar to the expression pattern in adult mediobasal hypothalamus from ovariectomized rats. These data indicate that a factor present in FBS imparts PRL responsiveness to hypothalamic dopaminergic neurons in vitro. The effective PRL concentrations and the time course for PRL's action in vitro are within the physiological range in vivo. The colocalization of PRL receptor in dopaminergic neurons provides anatomical evidence for a direct effect of PRL, with the long form of the PRL receptor being the predominant form in the hypothalamic cells.
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PMID:Prolactin (PRL) receptors are colocalized in dopaminergic neurons in fetal hypothalamic cell cultures: effect of PRL on tyrosine hydroxylase activity. 920 47

In this study, expression of the prolactin receptor (PRL-R) gene in the ovaries of cycling and pregnant red deer (Cervus elaphus) hinds was investigated. A 1.9-kilobase (kb) cDNA encoding the cervine long-form PRL-R was amplified by reverse transcriptase polymerase chain reaction from corpus luteum (CL) and liver poly(A)+ RNA. Northern hybridization revealed a major mRNA transcript of 3.5 kb in both tissues. PRL-R mRNA transcripts were localized by in situ hybridization in 15-micron frozen sections of red deer ovaries, collected during the estrous cycle and early pregnancy, with homologous 45-mer [35S]dATP-labeled sense and antisense oligonucleotide probes. Specific hybridization was assessed by measurement of autoradiograph optical density (OD) in CL, follicles and stroma. PRL-R mRNA expression was higher (p < 0.001) in the CL (OD = 22.2 +/- 3.77, n = 11 CL) than in follicles (OD = 2.8 +/- 0.10, n = 224 follicles) and was undetectable in the stroma (OD < 1, limit of detection). No differences in abundance of PRL-R mRNA were observed between follicles divided on the basis of size, health vs. atresia, or stage of estrous cycle or pregnancy, or between CL from pregnant and nonpregnant hinds. In the follicles, PRL-R mRNA was localized to the theca layer. These results suggest a direct role for PRL in red deer ovarian physiology during the estrous cycle and pregnancy.
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PMID:Expression and localization of prolactin receptor messenger ribonucleic acid in red deer ovary during the estrous cycle and pregnancy. 931 91

Urocortin is a recently identified neuropeptide of the CRF family in the mammalian brain, but its expression in human tissue has been little studied. In this study, we examined urocortin expression in human anterior pituitary gland and pituitary adenomas by RIA, high performance liquid chromatography, immunohistochemistry, messenger ribonucleic acid (mRNA) in situ hybridization, and reverse transcriptase-PCR. Immunoreactive urocortin concentrations in normal pituitary tissue extract were 103.25 +/- 39.05 ng/g wet wt (mean +/- SEM; n = 4), and their levels were all significantly higher than those in other portions of central nervous system of the same subjects. High performance liquid chromatography analysis of human pituitary extract demonstrated a single peak corresponding to that of the expected chromatographic mobility of synthetic human urocortin-(1-40). Urocortin-immunoreactive cells were detected in the anterior pituitary gland. Neither urocortin-immunoreactive nerve fibers nor cells were detected in the posterior lobe. Immunostaining in serial mirror tissue sections revealed that 76.55 +/- 3.06% of urocortin-immunoreactive cells expressed GH immunoreactivity, whereas 22.25 +/- 3.02% and less than 1% of urocortin-immunoreactive cells expressed PRL and ACTH, respectively. mRNA hybridization signals of urocortin were also detected in urocortin-immunopositive pituitary cells. The reverse transcriptase-PCR analysis demonstrated a 145-bp RNA band corresponding to that of the expected length of urocortin in all cases of normal pituitary glands examined (n = 3). We also immunostained urocortin in 52 cases of human anterior pituitary adenomas, including GH-producing adenomas (n = 14), ACTH-producing adenomas (n = 13), PRL-producing adenomas (n = 11), and nonfunctioning hormonally inactive adenomas (n = 14). No urocortin immunoreactivity was detected in these adenoma cells, except for one case of GH-producing adenoma and one case of nonfunctioning adenoma. We also performed mRNA in situ hybridization in 27 adenomas. No hybridization signals were detected in these adenomas, except in two cases. The results described above indicated that urocortin is synthesized in human anterior pituitary cells and may play an important role in biological features of normal pituitary gland, possibly as an autocrine or a paracrine regulator
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PMID:Urocortin expression in human pituitary gland and pituitary adenoma. 936 May 50

The growth regulatory effects of PRL on the human breast are mediated by its receptor (PRLr), a member of the cytokine receptor family. Recent reverse transcriptase-PCR studies by our laboratory and others have shown PRL expression within breast tissues at the RNA level. To confirm the role of this growth factor-receptor complex in normal and malignant breast tissues, the expression of PRL and PRLr was examined in parallel with the estrogen receptor (ER) and progesterone receptor (PR). Sixty-nine cases of primary invasive breast carcinoma were examined for PRL and PRLr expression by in situ hybridization and immunohistochemical technique, respectively. These data revealed widespread expression of PRL and its receptor in the breast cancers studied (>95%) and in the normal breast tissues (>93%), with no association between the expression of PRL-PRLr and ER or PR. These findings stand in contrast to prior RIA-based studies that detected the PRLr in only 20-60% of breast carcinomas, most commonly in ER-PR-positive cells. These results confirm prior data indicating the presence of an autocrine/paracrine loop for the PRL-PRLr complex within human breast tissues. Given the widespread expression of PRL-PRLr in breast cancer, pharmacological interventions aimed at the inhibition of function of this growth regulatory receptor complex may be of considerable utility in the therapy of this disease.
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PMID:Expression of prolactin and its receptor in human breast carcinoma. 938 44

Extrapituitary PRL is synthesized by the decidualized endometrial stromal cells from the mid to late secretory phase in the nonpregnant cycle and throughout pregnancy. The function of PRL in the uterus is unknown, but the temporal expression indicates a role in implantation and placentation. PRL is a powerful immunoregulatory agent, and thus, a role in modulating endometrial leukocytes may be envisaged. To investigate the site of action of PRL, immunohistochemistry was conducted to localize the PRL receptor (PRL-R). In addition, ribonucleic acid was extracted and reverse transcriptase-PCR for PRL-R was conducted. PRL-R protein was immunolocalized to the glandular epithelium and a subset of stromal cells from the mid to late secretory phase of the menstrual cycle and in early decidua. PRL-R transcripts were also detected from the late secretory phase and first trimester decidua. These findings indicate that the receptor is expressed in a temporal pattern similar to that of PRL. PRL-R expression in the glandular epithelium is consistent with a role in regulating glandular activity. Furthermore, immunoreactivity for PRL-R in a subset of stromal cells may be evidence for paracrine interactions between decidualized cells or an immunoregulatory role for PRL.
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PMID:Localization and temporal expression of prolactin receptor in human endometrium. 943 52


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