Polyamine Regulation of the Rat Pro‐Opiomelanocortin Gene Expression in AtT‐20 Cells

Yamamori, Etsuko; Iwasaki, Yoshinobu; Aoki, Yasumichi; Nomura, Akihiro; Tachikawa, Kazushige; Ariyoshi, Yasuo; Mutsuga, Naomi; Morishita, Minako; Yoshida, Masanori; Asai, Masato; Oiso, Yutaka; Saito, Hidehiko

doi:10.1046/j.1365-2826.2001.00691.x

Cited by 4 publications

(1 citation statement)

References 16 publications

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“…It may be a vestige of the ancestral regulation of calcium metabolism by the pituitary gland. Interestingly, some data suggest that polyamines, which are potent CaR agonists, can stimulate ACTH release from the pituitary gland (Yamamori et al, 2001; Cheng et al, 2004). Moreover, there is diurnal variation in polyamine levels in the pituitary, raising the intriguing possibility that signaling through the CaR might be involved in modulating ACTH secretion in a circadian pattern (Yamamori et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

The calcium-sensing receptor couples to Gαs and regulates PTHrP and ACTH secretion in pituitary cells

Mamillapalli¹,

Wysolmerski²

2009

Journal of Endocrinology

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The calcium-sensing receptor (CaR) is a G-protein-coupled receptor (GPCR) that binds and signals in response to extracellular calcium and other polycations. It is highly expressed on parathyroid and kidney cells, where it participates in the regulation of systemic calcium homeostasis. It is also expressed on many other cell types and is involved in a wide array of biological functions such as cell growth and differentiation, ion transport and hormone secretion. It has been described to couple to several different G-proteins including Gαi/0, Gαq/11 and Gα12/13. Recently, it has also been shown to stimulate cAMP production by coupling to Gαs in immortalized or malignant breast cells. The CaR is expressed on cells in the anterior pituitary and had previously been described to stimulate cAMP production in these cells. In this report, we examined signaling from the CaR in murine pituitary corticotroph-derived, AtT-20 cells. We found that CaR activation led to the stimulation of cAMP production, and PTHrP and ACTH secretion from these cells. Furthermore, manipulation of cAMP levels was able to modulate PTHrP and ACTH secretion independent of changes in extracellular calcium. Finally, we demonstrated that the CaR couples to Gαs in AtT-20 cells. Therefore, in pituitary corticotroph-like cells, as in breast cancer cells, the CaR utilizes Gαs and activates cAMP production to stimulate hormone secretion.

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Section: Discussionmentioning

confidence: 99%

The calcium-sensing receptor couples to Gαs and regulates PTHrP and ACTH secretion in pituitary cells

Mamillapalli¹,

Wysolmerski²

2009

Journal of Endocrinology

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Native somatostatin sst2 and sst5 receptors functionally coupled to Gi/o-protein, but not to the serum response element in AtT-20 mouse tumour corticotrophs

Cervia

Fehlmann

Hoyer

2003

Naunyn-Schmiedeberg's Arch Pharmacol

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Of the five cloned somatostatin (SRIF: somatotropin release inhibitory factor) receptors (sst1-5), only sst2 and sst5 receptors appear to be endogenously expressed and functionally active in AtT-20 mouse anterior pituitary tumour cells. In this study, the presence and the functional coupling of SRIF receptors to G-protein in AtT-20 cells was evaluated by receptor autoradiography and guanosine-5'-Omicron-(3-[35S]thio)-triphosphate ([35S]GTPgammaS) binding, respectively. In addition, transcriptional effects via the serum response element (SRE) were assessed in AtT-20-SRE-luci cells, engineered to express constitutively SRE upstream of the luciferase reporter gene. [125I]LTT-SRIF-28, [125I]CGP 23996 and [125I]Tyr3-octreotide binding illustrates the high level of sst2/5 receptor in AtT-20 cell membranes. SRIF-14 and SRIF-28 produced a concentration-dependent increase in [35S]GTPgammaS binding (pEC50=6.72 and 7.45; Emax=79 and 74.9, respectively) which was completely abolished by pertussis toxin. sst2/5 receptor-selective ligands caused a concentration-dependent increase in [35S]GTPgammaS binding (pEC50=7.74-5.84; Emax=76.6-20.2) while sst1/3/4 receptor-selective ligands were devoid of activity. The binding profiles of [125I]LTT-SRIF-28 and the inhibition of cAMP accumulation correlated highly significantly with their corresponding [35S]GTPgammaS binding profiles (r=0.862 and 0.874, respectively). The effects of the sst2 receptor-preferring agonists Tyr3-octreotide and BIM 23027 on [35S]GTPgammaS binding, but not those of SRIF-14 and the sst5/1 receptor selective-agonist L-817,818, were competitively antagonised by the sst2 receptor antagonist d-Tyr8-CYN 154806 (pKB=7.36 and 7.72, respectively; slope factors not significantly different from unity). In AtT-20-SRE-luci cells, which carry a SRE-luciferase construct functioning in a very efficient manner, SRIF and its analogues did not affect luciferase activity. Taken together, these results demonstrate that in AtT-20 cells the expression of sst2 and sst5 receptors fit with their functional coupling to G(i/o)-proteins. The pharmacological implications of the existence of different ligand/receptor complexes are discussed. However, the intracellular pathways coupled to the activation of sst2 and sst5 receptors appear not to modulate the SRE-mediated transcriptional activity, suggesting that SRIF effects on gene expression coupled to mechanisms that have promoters other than SRE.

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Biological polyamines inhibit nucleic-acid-induced polymerisation of prion protein

Bera

Nandi

2007

Arch Virol

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Nucleic-acid-induced polymerisation of prion protein, when monitored by anilino naphthalene sulfonic acid dye, shows, successively, an immediate fluorescence increase of the dye upon mixing of the reactants, followed by a lag period in which the dye fluorescence remains unchanged, and then a phase in which dye fluorescence increases with time. The biological polyamines spermine and spermidine reduce the extent of the initial fluorescence increase, increase the lag period, and reduce both the rate and the extent of increase in fluorescence intensity of the dye in the final phase of the reaction. Spermidine is less effective than spermine in all of these processes. A nearly fivefold lower concentration of spermine can inhibit polymerisation of prion protein by tRNAs compared to the same process induced by double-stranded nucleic acid. The change in the secondary structure of the globular domain of the protein induced by nucleic acid is reversed by the addition of spermine, and it prevents structural destabilization of this domain induced by nucleic acids. It is suggested that physiological event(s) that would reduce the concentrations of intracellular biological amines may make nucleic acid available to induce oligomerization and polymerisation of cellular prion protein related to prion disease.

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Polyamine Regulation of the Rat Pro‐Opiomelanocortin Gene Expression in AtT‐20 Cells

Cited by 4 publications

References 16 publications

The calcium-sensing receptor couples to Gαs and regulates PTHrP and ACTH secretion in pituitary cells

The calcium-sensing receptor couples to Gαs and regulates PTHrP and ACTH secretion in pituitary cells

Native somatostatin sst2 and sst5 receptors functionally coupled to Gi/o-protein, but not to the serum response element in AtT-20 mouse tumour corticotrophs

Biological polyamines inhibit nucleic-acid-induced polymerisation of prion protein

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