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)

A major role for Ca2+ and calmodulin in stimulus-secretion coupling has been suggested for several neuropeptides; however, the cellular mechanisms of GH-releasing hormone (GHRH) release have been little investigated so far. We have used a previously validated acute rat hypothalamic explant system in order to elucidate whether Ca2+ acts as a second messenger in the regulation of GHRH release, and whether calmodulin-dependent pathways are involved. Calcium dependence of somatostatin (SRIH) release was assessed in the same experiments. Calmodulin dependence of SRIH was not investigated in detail, as it has been established previously. The calcium-entry antagonist, verapamil, antagonized K(+)-stimulated GHRH and SRIH release in a dose-dependent manner, with maximal inhibition shown at 10(-4) M. The calmodulin antagonist W7 also blocked K(+)-evoked GHRH release in a dose-dependent manner, with significant inhibition in the dose range 5 X 10(-5) M to 2 X 10(-4) M; similarly, a more specific calmodulin inhibitor, the W7 derivative 5-iodo-C8 (W8), reversed K(+)-stimulated GHRH release, showing slightly higher potency than W7. W7 also reversed GHRH release in response to the calcium-ionophore A23187, although verapamil had no effect on A23187-evoked GHRH or SRIH release. Thapsigargin, which increases the efflux of Ca2+ from calciosomes, did not affect either GHRH or SRIH release at 10(-5) M or 10(-4) M. The basal release of GHRH was clearly suppressed by W7 and W8 (10(-4) M), whereas verapamil had no effect. We conclude that calcium influx is crucial for depolarization-induced GHRH and SRIH release. Calcium entrance in response to A23187 appears to be independent of verapamil-sensitive calcium channels. The lack of effect of thapsigargin suggests that increased intracellular Ca2+ from intracellular stores is not equivalent to an increase in Ca2+ influx. Both basal and depolarization-induced release of GHRH in this system are calmodulin dependent.
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PMID:Calcium and calmodulin mediation of growth hormone-releasing hormone release from the rat hypothalamus in vitro. 167 85

1. In this study we have investigated neuropeptide Y (NPY) and somatostatin (SRIF) receptor-mediated elevation of intracellular Ca2+ concentration ([Ca2+]i) in the human neuroblastoma cell line SH-SY5Y. 2. The Ca(2+)-sensitive dye fura 2 was used to measure [Ca2+]i in confluent monolayers of SH-SY5Y cells. Neither NPY (30-100 nM) nor SRIF (100 nM) elevated [Ca2+]i when applied alone. However, when either NPY (300 pM-1 microM) or SRIF (300 pM-1 microM) was applied in the presence of the cholinoceptor agonist carbachol (1 microM or 100 microM) they evoked an elevation of [Ca2+]i above that caused by carbachol alone. 3. The elevation of [Ca2+]i by NPY was independent of the concentration of carbachol. In the presence of 1 microM or 100 microM carbachol NPY elevated [Ca2+]i with a pEC50 of 7.80 and 7.86 respectively. 4. In the presence of 1 microM carbachol the NPY Y2 selective agonist peptide YY(3-36) (PYY(3-36)) elevated [Ca2+]i with a pEC50 of 7.94, the NPY Y1 selective agonist [Leu31, Pro34]-NPY also elevated [Ca2+]i when applied in the presence of carbachol, but only at concentrations > 300 nM. The rank order of potency, PYY(3-36) > or = NPY > > [Leu31, Pro34]-NPY indicates that an NPY Y2-like receptor is involved in the elevation of [Ca2+]i. 5. In the presence of 1 microM carbachol, SRIF elevated [Ca2+]i with a pEC50 of 8.24. The sst2 receptor-preferring analogue BIM-23027 (c[N-Me-Ala-Tyr-D-Trp-Lys-Abu-Phe]) elevated [Ca2+]i with a pEC50 of 8.63, and the sst5-receptor preferring analogue L-362855 (c[Aha-Phe-Trp-D-Trp-Lys-Thr-Phe]) elevated [Ca2+]i with a pEC50 of approximately 6.1. Application of the sst3 receptor-preferring analogue BIM-23056 (D-Phe-Phe-Tyr-D-Trp-Lys-Val-Phe-D-Nal-NH2, 1 microM) to SH-SY5Y cells in the presence of carbachol neither elevated [Ca2+]i nor affected the elevations of [Ca2+]i caused by a subsequent coapplication of SRIF. The rank order of potency, BIM-23026 > or = SRIF > > L-362855 > > > BIM-23026 suggests that an sst2-like receptor is involved in the elevation of [Ca2+]i. 6. Block of carbachol activation of muscarinic receptors with atropine (1 microM) abolished the elevation of [Ca2+]i by the SRIF and NPY. 7. Muscarinic receptor activation, not a rise in [Ca2+]i, was required to reveal the NPY or SRIF response. The Ca2+ channel activator maitotoxin (2 ng ml-1) also elevated [Ca2+]i but subsequent application of either NPY or SRIF in the presence of maitotoxin caused no further changes in [Ca2+]i. 8. The elevations of [Ca2+]i by NPY and SRIF were abolished by pretreatment of the cells with pertussis toxin (200 ng-ml-1, 16 h). This treatment did not significantly affect the response of the cells to carbachol. 9. NPY and SRIF appeared to elevate [Ca2+]i by mobilizing Ca2+ from intracellular stores. Both NPY and SRIF continued to elevate [Ca2+]i when applied in nominally Ca(2+)-free external buffer. Thapsigargin (100 nM), an agent which discharges intracellular Ca2+ stores, also blocked the NPY and SRIF elevations of [Ca2+]i. 10. Delta-Opioid receptor agonists applied in the presence of carbachol also elevate [Ca2+]i in SH-SY5Y cells. When NPY (30 nM) or SRIF (100 nM) was applied together with a maximally effective concentration of the delta-opioid receptor agonist DPDPE ([D-Pen2,5]-enkephalin) (1 microM), the resulting elevations of [Ca2+]i were not greater than those caused by application of DPDPE alone. 11. Thus, in SH-SY5Y cells, NPY and SRIF can mobilize Ca2+ from intracellular stores via activation of NPY Y2 and sst2-like receptors, respectively. Neither NPY nor SRIF elevated [Ca2+]i when applied alone. The requirements for the elevations of [Ca2+]i by NPY and SRIF are the same as those for delta- and mu-opioid receptor and nociceptin receptor mobilization of [Ca2+]i in SH-SY5Y cells.
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PMID:Neuropeptide Y Y2 receptor and somatostatin sst2 receptor coupling to mobilization of intracellular calcium in SH-SY5Y human neuroblastoma cells. 903 49

1. Somatostatin (somatotropin release inhibiting factor; SRIF) acts via five G protein-coupled receptors (sst(1)-sst(5)) that modulate multiple cellular effectors. The aim of this study was to compare two functional effects of the human sst(2) receptor stably expressed in CHO-K1 cells in a single experiment using a duplex assay for intracellular calcium and serum response element (SRE)-driven luciferase expression. 2. Intracellular calcium was measured using a fluorometric imaging plate reader II (FLIPR II). SRIF-14 rapidly and transiently increased intracellular calcium with a pEC(50) of 8.74+/-0.03 (n=52). At 5 h after FLIPR II measurements, luciferase expression was determined. SRIF-14 concentration-dependently increased luciferase expression (pEC(50)=9.06+/-0.03, n=52). 3. Natural and synthetic agonist/antagonist ligands for SRIF receptors were tested in the duplex assay. Correlation of agonist potencies and efficacies between the two responses were significant (r(2)=0.83 and 0.90, pEC(50) and E(max), respectively). 4. Pertussis toxin pretreatment reduced SRIF-14/octreotide-mediated intracellular calcium increases by 45-47% and luciferase expression by 95-98%. 5. Thapsigargin pretreatment abolished the SRIF-14/octreotide-mediated intracellular calcium increase but had no effect on luciferase expression. 6. In conclusion, SRIF stimulates an increase in intracellular calcium and SRE-luciferase expression via human sst(2) receptors in CHO-K1 cells. The increase in luciferase is mediated via G(i)/G(o) while intracellular calcium increase is mediated by both G(i)/G(o) proteins and pertussis toxin-insensitive G proteins, and is mainly via release of calcium from intracellular stores. SRIF ligands display a similar recognition profile suggesting that the ligand/receptor/G protein/effector interaction is similar for the two parameters.
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PMID:Comparison of functional profiles at human recombinant somatostatin sst2 receptor: simultaneous determination of intracellular Ca2+ and luciferase expression in CHO-K1 cells. 1503 13