Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous investigations have shown that Ca2+ strongly and specifically stimulates endogenous PRL gene expression by GH3 cells. In this study, addition of Ca2+ to Ca2+-deprived GH3 cells yielded a large (ca. 8-fold) stimulation of transient expression of a transfected PRL-chloramphenical acetyltransferase (CAT) construct containing ca. 1 kilo-base-pair of the PRL promoter region, but only a slight (less than or equal to 2-fold) nonspecific stimulation of CAT activity directed by any of three control promoters: dihydrofolate reductase, Rous sarcoma virus, or thymidine kinase. In GH3 cells never deprived of Ca2+, expression of a PRL-CAT construct was specifically stimulated and inhibited, respectively, by the dihydropyridine voltage-dependent Ca2+ channel modulators Bay K8644 and nimodipine; Ca2+ can thus regulate expression of an exogenous PRL promoter in cells incubated under physiological Ca2+ conditions. By employing a combined protocol, in which Ca2+-deprived cells are exposed to Ca2+ in the presence of Bay K8644, a very large (greater than 35-fold) but still promoter-specific induction of expression of a PRL-CAT construct was obtained. Analysis of 5'-deleted PRL-CAT constructs implied that the PRL gene Ca2+ response element is contained entirely within the first 174 base pairs of upstream flanking DNA sequence.
Mol Endocrinol 1988 Nov
PMID:Proximal upstream flanking sequences direct calcium regulation of the rat prolactin gene. 246 50

Since insulin-like growth factors I (IGF-I) and II (IGF-II) appeared involved in paracrine or autocrine regulation of both cell multiplication and differentiation of the rat testis, we have investigated the pituitary hormonal dependence of IGF-I and IGF-II mRNA production in the testis of immature hypophysectomized rats (22 days old) supplemented with highly purified FSH, LH, GH or PRL. Our data show that testicular expression of IGF-I mRNA as measured by dot-blot hybridization, is increased by LH, FSH or GH treatments of 7-, 6-, and 4-fold, respectively, above controls. Intensity of the signal was 3-fold lower after PRL treatment than in hypophysectomized control rats. On the contrary, IGF-II mRNA expression, was found low in the immature hypophysectomized rat testis and unmodified by any hormonal treatment. In contrast to the increase of IGF-I expression in the testis no significant change in the IGF-I plasma concentration was observed after LH or FSH supplementation. GH treatment, as expected, increased 4-fold the IGF-I plasma concentration of the experimental animals. Since we have previously shown that LH, FSH, and GH exhibit selective cell multiplication and differentiation in the testis of our animal model, it is proposed that testicular IGF-I expression could be the tissue response to pituitary hormone in these phenomena.
Mol Endocrinol 1989 Jul
PMID:Pituitary hormones dependent expression of insulin-like growth factors I and II in the immature hypophysectomized rat testis. 247 94

Binding of TRH to specific cell surface receptors on clonal GH4C1 cells is followed within 10 min by receptor sequestration and over 24 h by receptor down-regulation. These experiments were designed to determine if TRH-activated second messenger systems are responsible for changes in receptor localization or number. BAY K8644 and A23187, which increase intracellular calcium, alone or together with 12-O-tetradecanoyl phorbol acetate (TPA), which activates protein kinase C, did not appear to internalize TRH receptors. Drug treatment did not alter the rate of [3H]MeTRH association or internalization, determined by resistance to an acid/salt wash, or the amount of [3H]MeTRH able to bind at 0 C, where only surface receptors are accessible. TPA (0-100 nM) alone or in combination with BAY K8644 or A23187, also failed to change receptor number or affinity after 48 h when TRH caused a 75% decrease in the density of specific binding sites. Chlordiazepoxide has been reported antagonize TRH binding and TRH-induced phospholipid breakdown. Chlordiazepoxide shifted the dose-response curves for TRH stimulation of PRL release and synthesis to the right, and did not change PRL release alone. The affinity of receptors for chlordiazepoxide was not affected by a nonhydrolyzable analog of GTP whereas affinity for TRH was decreased; these properties are consistent with the classification of chlordiazepoxide as a competitive antagonist. Several experiments tested whether chlordiazepoxide would cause receptor internalization and down-regulation. Chlordiazepoxide did not appear to internalize TRH receptors, because TRH-binding sites became available rapidly and at the same rate after they had been saturated with chlordiazepoxide at 0 or 37 C.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1989 Sep
PMID:Pituitary thyrotropin-releasing hormone (TRH) receptors: effects of TRH, drugs mimicking TRH action, and chlordiazepoxide. 248 18

Thyroidectomized rats were used to study the effects of a single injection of T3 on pituitary mRNA synthesis and hormone secretion. T3 was injected ip at doses of 0, 0.2, 1, or 5 micrograms/100 g body weight, and and animals were killed 24 h later. T3 caused a significant decrease in serum TSH, but caused no significant change in either serum GH or PRL. Pituitary mRNA was quantified by slot blot hybridization with cDNA probes specific for alpha-TSH, beta-TSH, PRL, and GH. We found that both the alpha and beta mRNA subunits decreased, that PRL mRNA remained relatively unchanged, and that GH mRNA increased with increasing T3 dose. The data show that a single dose of T3 can profoundly influence mRNA levels in the anterior pituitary; the lowest dose of T3 caused maximum inhibition of alpha-TSH mRNA while beta-TSH mRNA declined further in a dose-dependent manner.
Mol Endocrinol 1987 Jun
PMID:Influence of thyroidal status on pituitary content of thyrotropin beta- and alpha-subunit, growth hormone, and prolactin messenger ribonucleic acids. 248 16

In order to investigate the molecular mechanism(s) by which TRH regulates the biosynthesis of TSH, we are studying the effects of TRH on the expression of the TSH subunit genes (alpha and TSH beta). To study the structure-function relation of TRH stimulation of the activity of the single rat TSH beta gene, chimaeric plasmids were constructed. The 5'-flanking region of the rat TSH beta gene including exon 1 (5'-untranslated region) was inserted into a promoterless, modified pBR, chloramphenicol acetyltransferase (CAT) expression vector. After transfection, specific TSH beta promoter activity was evident in both TRH-responsive pituitary-derived GH3 and primary pituitary cell cultures. To determine potential regulation of TSH beta promoter-directed activity in these cells by TRH, cells were incubated with media containing TRH (10(-7) to 10(-11) M) for 1 to 48 h. TRH stimulated a 1.5- to 3-fold increase in TSH beta promoter activity. Concomitant with an increase in CAT activity was an anticipated increase in PRL synthesis in the GH3 cells in response to TRH. The TRH effect on the TSH beta gene was specific; no increase in CAT activity was detected for TKCAT (thymidine kinase of herpes simplex virus promoter), pBRCAT (no promoter), or TSH beta CAT (3'-5'-orientation). Similar results were obtained using primary pituitary cell cultures. Deletion mutation analysis indicated that TRH sensitivity was detected in a 1.1 kilobase, but not in a 0.38 kilobase TSH beta gene fragment suggesting that the TRH responsive element(s) resides at least in part within the 700 base pairs of the 5'-flanking sequence.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1989 Apr
PMID:Thyrotropin-releasing hormone stimulates the activity of the rat thyrotropin beta-subunit gene promoter transfected into pituitary cells. 249 52

Our previous work demonstrated that in vivo estradiol (E2) administration to ovariectomized rats suppressed the transcription of the LH subunit genes within 4 h. To determine whether these effects were mediated directly at the level of the gonadotrope, the transcription rates of the LH beta, FSH beta, and alpha-subunits were measured in short term cultures of pituitary fragments from female rats in various physiological states. In each in vitro experiment, fragments from matched sets of hemipituitaries were used for control and treatment (10(-8)ME2) groups. In pituitaries from ovariectomized animals, treated in vitro with or without E2, there was no significant effect of 2 h or 6 h of E2 on FSH beta or alpha-subunit gene transcription, but a consistent 2- to 3-fold stimulation of LH beta mRNA synthesis. In pituitaries from intact randomly cycling rats, E2 in culture had no effect on the transcription rate of alpha-subunit, FSH beta, or TSH beta genes, but stimulated LH beta and PRL transcription 2-fold. Thyroid hormone treatment specifically suppressed alpha-subunit (38% of control) and TSH beta (17% of control) mRNA synthesis, indicating that the culture system is responding in an appropriate physiological manner and that decreases in transcription can be easily and accurately measured with this system. Basal and E2-treated transcription rates for each gonadotropin subunit gene were measured as a function of stage of the estrous cycle. Basal transcription of the alpha-subunit gene did not vary significantly throughout the cycle and did not respond to E2 treatment in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1989 Mar
PMID:Divergent effects of estradiol on gonadotropin gene transcription in pituitary fragments. 250 67

To investigate the relationship of changes in cytosolic free calcium concentrations [( Ca2+]c) caused by TRH to changes in PRL secretion, we simultaneously monitored PRL release and [Ca2+]c, using the fluorescent Ca2+ indicator indo-1, in freshly isolated perifused cells from rat anterior pituitary glands. We found that a 30-sec pulse of 100 nM TRH triggered a transient spike of [Ca2+]c, but prolonged PRL release for up to 30 min; continuous administration of TRH caused a sustained elevation in [Ca2+]c, but the same pattern and amount of PRL release as that caused by the pulse of TRH. PRL secretion was refractory to further pulses of TRH given at 10-min intervals for 40 min, but did respond to a second pulse of TRH given 40 min after the first pulse with no intervening pulses. Pulses of TRH given every 10 min still triggered spikes of [Ca2+]c of the same magnitude as the first pulse, indicating that the cause of the refractory state must occur at a post-receptor step that is after the mobilization of [Ca2+]c. A 30-sec pulse of a high concentration of KCl caused a transient spike of [Ca2+]c and transient, not prolonged, release. Additional pulses of KCl cause progressively less PRL release, although the magnitude of the spikes in [Ca2+]c did not change.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1989 Mar
PMID:Ca2+ transients induced by thyrotropin-releasing hormone rapidly lose their ability to cause release of prolactin. 250 68

Previous studies have demonstrated that the high basal level of transcription of the rat PRL gene in pituitary tumor GH3 cells is dependent on [CA2+]e. In the present study, we have extended these findings by examining the effects of the Ca2+ ionophores, A23187 and ionomycin, on [Ca2+]i, and on PRL mRNA levels and glucose-regulated protein (GRP) mRNA levels in GH3 cells cultured in a low Ca2+, serum-free medium (SFM). Using digital imaging microscopy of individual Fura 2-loaded GH3 cells in SFM plus 0.4 mM CaCl2, extranuclear and nuclear [Ca2+] were both about 70 nM. Addition of 600 nM ionomycin increased these levels by 10-fold within minutes, and by about 45-fold after 120 min. As previously published, addition of 0.4 mM CaCl2 to GH3 cells cultured in SFM significantly increased PRL mRNA, and had little or no effect on GRP78 and GRP94 mRNA after 16 h. Addition of 0.4 mM CaCl2 plus 100 nM A23187 significantly increased GRP78 and GRP94 mRNA. Surprisingly, the Ca2+ ionophore significantly inhibited PRL gene expression below that obtained in 0.4 mM CaCl2 without A23187. This same pattern of stimulation of GRP78 gene expression, but inhibition of PRL gene expression, was observed with 125 and 600 nM ionomycin. Both Ca2+ ionophores had no effect on histone 3 mRNA, and A23187 depressed PRL gene expression at a concentration (50 nM) that did not affect protein synthesis. Although A23187 reproducibly lowered PRL mRNA levels, it slightly inhibited its degradation in cells in which RNA synthesis was blocked by actinomycin D.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1989 Nov
PMID:Calcium regulation of prolactin gene expression: opposing effects of extracellular CaCl2 and Ca2+ ionophores. 251 48

The major PRL-inducible gene product from pigeon cropsac was cloned from lambda gt11 and sequenced by chain termination. The sequence of pGcp35 includes an open reading frame which yields a polypeptide which highly similar to mammalian calpactin II (lipocortin I). Like the other calpactins, the deduced protein (cp35) consists of a 4-fold repeating structure which has a conserved core characteristic of a large group of calcium-dependent membrane-binding proteins. PRL-stimulated cropsac expresses a calcium-dependent membrane-binding protein which is the proper size for endogenous cp35. Detailed comparison of the sequences of cp35 and human calpactin II shows that the only substantial sequence dissimilarity is a domain encoding amino acids between residues 20 and 40 which includes a tyrosine phosphorylation site in the human molecule, along with other residues of possible physiological significance. These results raise the possibility that calpactins are regulated by PRL in other tissues; and, that the sequences of the avian form and the mammalian form may have selectively diverged to yield different regulatory mechanisms.
Mol Endocrinol 1989 May
PMID:A prolactin-inducible gene product which is a member of the calpactin/lipocortin family. 252 23

The ability of an upstream element of the rat PRL gene to permit transcriptional regulation in response to several different hormones has been examined. To test the ability of specific DNA sequences to mediate hormone responsiveness, DNA fragments were subcloned upstream of a thymidine kinase-chloramphenicol acetyltransferase fusion gene and transferred into GH3 pituitary tumor cells. Initially, fragments representing a distal enhancer element (positions -1713 to -1495) and a more proximal element (positions -292 to -38) were tested. The results demonstrate that the distal enhancer permits cAMP, TRH, epidermal growth factor (EGF), and estradiol to stimulate expression of the thymidine kinase-chloramphenicol acetyltransferase gene. The proximal element permitted fusion gene regulation in response to cAMP, TRH, EGF, and phorbol esters. For the cAMP, TRH, and EGF responses, the distal element permitted responses approximately equal to or greater than responses conferred by the proximal PRL gene fragment. The response of the distal element to cAMP and TRH was more than additive with the response to estradiol, suggesting that the estrogen response element is distinct but may interact cooperatively with the other hormone response elements. Mutation of the estrogen-responsive element abolished both the response to estrogen and the cooperative response with cAMP, but not the response to cAMP itself. Mutation of a sequence involved in basal enhancer activity of the distal element reduced both basal transcription and the response to cAMP. These results suggest that the distal enhancer sequence of the PRL gene contains, in addition to an estrogen response element, elements that confer responsiveness to cAMP, TRH, and EGF.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1989 Jan
PMID:The distal enhancer region of the rat prolactin gene contains elements conferring response to multiple hormones. 253 91


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