Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The gene encoding a novel mouse somatostatin receptor termed mSSTR3 was isolated and characterized. The sequence of mSSTR3 shows 46 and 47% identity with mSSTR1 and mSSTR2, respectively. mSSTR3 binds somatostatin-14 and somatostatin-28 with high affinity, but shows very low affinity for the somatostatin analogs MK-678 and SMS-201-995. In addition, mSSTR3 is coupled to pertussis toxin-sensitive G proteins and mediates somatostatin inhibition of forskolin-stimulated and dopamine D1 receptor-stimulated cAMP formation, indicating that it is coupled to adenylylcyclase. The pharmacological properties of mSSTR3 and its ability to couple with adenylylcyclase distinguish SSTR3 from the other cloned somatostatin receptors and indicates that it mediates biological functions different from SSTR1 or SSTR2. In situ hybridization indicates that SSTR3 mRNA is widely distributed in the mouse brain, and its expression in the nucleus of the lateral olfactory tract and in the piriform cortex, the primary olfactory cortex in the rodent brain, suggests that SSTR3 may participate in the processing and modulation of primary sensory information.
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PMID:Cloning of a novel somatostatin receptor, SSTR3, coupled to adenylylcyclase. 132 99

Somatostatin (SRIF) receptors are coupled to the catalytic subunit of adenylyl cyclase via pertussis toxin-sensitive guanine nucleotide-binding regulatory proteins (G proteins). To identify which G proteins link SRIF receptors to adenylyl cyclase, G(o) alpha, Gi alpha, and its different subtypes were individually blocked in AtT-20 cell membranes with G alpha subtype-selective antisera. Antiserum directed against the carboxyl-terminal region of Gi alpha blocked SRIF inhibition of forskolin-stimulated adenylyl cyclase activity, and this effect was prevented by the peptide to which the antiserum was generated. However, antiserum directed against the carboxyl-terminal region of G(o) alpha did not affect SRIF inhibition of adenylyl cyclase activity, indicating that Gi alpha couples SRIF receptors to adenylyl cyclase but G(o) alpha does not. Peptide-directed antisera against Gi alpha 1 completely blocked SRIF inhibition of adenylyl cyclase activity. In contrast, antisera directed against either Gi alpha 2 or Gi alpha 3 did not affect the actions of SRIF. The results of these studies indicate that Gi alpha 1 selectively couples SRIF receptors to the catalytic subunit of adenylyl cyclase in AtT-20 cell membranes. Because previous studies have shown that SRIF receptors are able to couple to Gi alpha 1, Gi alpha 3, and G(o) alpha, the results suggest that different G proteins may specify the coupling of SRIF receptors to distinct cellular effector systems.
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PMID:Gi alpha 1 selectively couples somatostatin receptors to adenylyl cyclase in pituitary-derived AtT-20 cells. 134 39

The effects of somatostatin-28, somatostatin-14, and a synthetic somatostatin octapeptide analogue, D-Phe-Cys-Tyr-D-Trp-Lys-Thr-Cys-Nal-NH2 (cyclo SS-8) were examined on contraction of dispersed gastric smooth muscle cells from guinea pigs. The somatostatins did not cause contraction of gastric smooth muscle cells, nor did they inhibit carbachol-stimulated contraction. However, they reversed vasoactive intestinal peptide (VIP)-induced inhibition (relaxation) of carbachol-stimulated contraction. Somatostatin-28 had a half-maximal effect (EC50) at 1.6 +/- 0.8 nM, cyclo SS-8 at 0.6 +/- 0.3 nM, but somatostatin-14 had no effect even when used in concentrations as high as 1 microM. Incubation of muscle cells with peptidase inhibitors phosphoramidon (1 microM) plus amastatin (10 microM) had no effect on the EC50 of somatostatin-28 or cyclo SS-8 but increased the potency of somatostatin-14 greater than 1,000-fold. When peptides were incubated with muscle cells and the products applied to high-performance liquid chromatography, cyclo SS-8 was not degraded, but somatostatin-14 was rapidly degraded when present alone, and the addition of peptidase inhibitors partially inhibited the degradation. Cyclo SS-8 had its maximal effect at 0.5-1 min and inhibited relaxation induced by VIP, isoproterenol, glucagon, or dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP). Cyclo SS-8 partially inhibited the increase in VIP-stimulated cAMP. Preincubation with pertussis toxin blocked the inhibitory action of cyclo SS-8 on VIP or DBcAMP-induced relaxation. These results indicate that gastric smooth muscle cells rapidly degrade somatostatin-14 and suggest that muscle cell peptidases could have a major effect on the actions of somatostatin-14.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Actions of somatostatins on gastric smooth muscle cells. 134 75

Previous studies have shown that at least two subtypes of somatostatin (SRIF) receptors (SRIF1 and SRIF2) are expressed in mammalian cells. SRIF1 receptors have high affinity for MK 678, whereas SRIF2 receptors have no affinity for MK 678 but selectively bind peptides with structures similar to that of CGP 23996. Recently, two SRIF receptor genes have been cloned from human and mouse genomic libraries. In the present study, the pharmacological properties of these two cloned SRIF receptors, expressed in Chinese hamster ovary (CHO) cells, were investigated, to determine whether they have any similarity to the previously described SRIF1 and SRIF2 receptor subtypes. Both cloned receptors could be labeled with 125I-Tyr11-SRIF and exhibited high affinity for SRIF. The SSTR1 receptor could also bind CGP 23996-like compounds but not MK 678. In contrast, the SSTR2 receptor was insensitive to CGP 23996-like compounds but bound MK 678 with high affinity. These findings indicate that the peptide specificities of the cloned SSTR1 and SSTR2 receptors differ from each other. Pretreatment of CHO cells expressing the two cloned SRIF receptors with SRIF abolished high affinity agonist binding to the cloned SSTR2 receptor but not the cloned SSTR1 receptor. Agonist binding to SSTR1 receptors was not significantly affected by guanosine-5'-)-(3-thiotriphosphate) or pertussis toxin pretreatment, whereas agonist binding to SSTR2 receptors was inhibited by both treatments. These findings suggest that SSTR2 receptors can be regulated and they associate with pertussis toxin-sensitive guanine nucleotide-binding proteins, whereas SSTR1 receptors do not. SRIF is a potent inhibitor of adenylyl cyclase activity in mammalian cells. However, neither the cloned SSTR2 nor SSTR1 receptor mediated SRIF inhibition of adenylyl cyclase activity in stably transformed CHO cells or COS-1 cells transiently expressing the cloned receptors, suggesting that neither cloned receptor couples to adenylyl cyclase. The results of these studies indicate that the two cloned SRIF receptors have different pharmacological properties. The characteristics of the cloned SSTR2 receptor are similar to those of the previously described SRIF1 receptor, and the characteristics of the cloned SSTR1 receptor are similar to those of the previously described SRIF2 receptor.
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PMID:Pharmacological properties of two cloned somatostatin receptors. 135 50

A somatostatin (SRIF) receptor and its associated Gi regulatory proteins was purified from GH4C1 rat pituitary cells by: 1) saturation of the membrane-bound receptor with biotinyl-NH-[Leu8,D-Trp22,Tyr25] SRIF28 (bio-S28); 2) solubilization of receptor-ligand (R.L) complex with deoxycholate-lysophosphatidylcholine (D.L); 3) adsorption of solubilized receptor-ligand complex to immobilized streptavidin; and 4) elution of receptor and G-protein by GTP. The receptor, a glycoprotein with an average M(r) of 85,000, was then purified to substantial homogeneity on immobilized wheat germ agglutinin. The 85-kDa glycoprotein was identified as a SRIF receptor by several criteria. (a) It had the same size as the chemically cross-linked R.[125I]L complex. (b) Yield of the purified protein increased and plateaued in the same range of bio-S28 concentrations where specific high affinity binding reached saturation. (c) It was copurified with appropriate G-protein subunits. The 85-kDa receptor and two other proteins with M(r) values of 35,000 and 40,000, the sizes of G beta and G alpha, did not appear in eluates from control streptavidin columns done with SRIF receptors loaded with nonbiotinylated S14. The 40-kDa protein was identified as a Gi alpha by ADP-ribosylation from [32P]NAD catalyzed by pertussis toxin. (d) Both the chemically cross-linked R.[125I]L complex and SRIF receptor purified from [35S]methionine-labeled GH4C1 cells were reduced in size to about 38 kDa by endoglycosidase F. (e) Amino acid sequence from the purified receptor was nearly identical with that of a recently cloned SRIF receptor subtype.
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PMID:Purification of a pituitary receptor for somatostatin. The utility of biotinylated somatostatin analogs. 135 97

The effects of somatostatin-14 and bombesin on [3H]inositol phosphate accumulation were studied in 24 h myo-[3H]inositol-prelabeled cultured rat acinar cells. Bombesin, 10 nM, stimulated basal formation of phosphatidyl monophosphate (InsP1), phosphatidyl 4,5-biphosphate (InsP2) and inositol 1,4,5-triphosphate (InsP3) by 128 +/- 5.2%, 147 +/- 10% and 155 +/- 5%, respectively. At 5 s, the ED50 value for InsP3 stimulation was 0.70 +/- 0.2 nM. This stimulation was partly blocked (64 +/- 0.04% inhibition) by 10 ng/ml Bordetella pertussis toxin. In contrast to bombesin, somatostatin, 10 nM, inhibited basal InsP1, InsP2 and InsP3 formation. At 5 s, the inhibition degree for InsP3 was 18 +/- 2.5% and the IC50s values 1 +/- 0.09 nM, 1 +/- 0.12 nM and 0.07 +/- 0.005 nM for InsP1, InsP2 and InsP3, respectively. Bombesin-stimulated InsP3 formation was also inhibited by somatostatin. At 5 s, the inhibition degree was 85 +/- 3.5% at 10 nM and the IC50 value, 0.10 +/- 0.05 nM. Furthermore, somatostatin inhibition of bombesin stimulation was partly blocked (66 +/- 4% inhibition) by Bordetella pertussis toxin. These data therefore suggest that the acinar pancreatic cells contain a somatostatin receptor exerting a negative control on basal and bombesin receptor-stimulated phosphatidyl inositol turnover.
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PMID:Somatostatin inhibition of phosphoinositides turnover in isolated rat acinar pancreatic cells: interaction with bombesin. 135 13

Vasopressin (VP) stimulates insulin secretion and inositol phosphate (InsP) production in clonal hamster beta cells (HIT) via a cyclic AMP-independent V1-receptor-mediated signal-transduction pathway. Somatostatin (SRIF) inhibited VP-stimulated insulin secretion, and the effects of SRIF were abolished by pretreatment with pertussis toxin. The Ca(2+)-channel blockers verapamil and nifedipine also inhibited VP-stimulated insulin secretion during 20 min incubations, but verapamil was ineffective at 2 min, and the effects of SRIF and nifedipine together were not addictive. SRIF failed to inhibit further the attenuated insulin response to VP in Ca(2+)-free medium. VP-stimulated InsP production was also inhibited by SRIF in a pertussis-toxin-sensitive manner. Whereas VP-stimulated insulin secretion was almost completely inhibited by SRIF at an equimolar concentration, VP-stimulated InsP production was much less sensitive to inhibition by SRIF, even at a 100-fold excess concentration. VP increased cytosolic Ca2+ in HIT cells loaded with fura 2, the fluorescent Ca2+ indicator. The increase was biphasic, with an initial rapid spike increase followed by a prolonged second phase. Both SRIF, at a concentration which inhibited VP-stimulated insulin secretion but not InsP production, and verapamil failed to inhibit the rapid spike increase in intracellular Ca2+, but did inhibit the second phase. We conclude that VP induces biphasic changes in cytosolic Ca2+, secondary to mobilization of intracellular Ca2+ and influx of extracellular Ca2+. SRIF inhibits insulin secretion by interrupting influx of extracellular Ca2+, likely by inhibiting Gi-subunit activity. Inhibition of VP-stimulated phosphoinositide hydrolysis, which is also pertussis-toxin-sensitive, may represent an additional mechanism of action of SRIF.
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PMID:Somatostatin inhibits vasopressin-stimulated phosphoinositide hydrolysis and influx of extracellular calcium in clonal hamster beta (HIT) cells. 136 25

G-proteins are important mediators of hormonal inhibition of insulin secretion. To characterize the pertussis toxin-sensitive substrates present in HIT cell membranes, we performed immunoblots with specific antisera and found evidence for the presence of Gi alpha 1, Gi alpha 2, Gi alpha 3, and three forms of Go alpha. We observed that pertussis toxin-sensitive substrates mediate all of the effects of SRIF, and a major portion of the effects of EPI, on insulin secretion from rat islets during static incubations. These results agree with our previously reported studies examining phasic glucose-induced insulin secretion from HIT cells. To ascertain whether inhibition of adenylate cyclase, presumably involving coupling of the catalytic subunit to Gi, may be a common mechanism for both hormones, we studied the effects of 8-bromo-cyclic AMP and found that this agent partially prevented the inhibitory effects of both hormones. We also observed that the inhibitory effects of SRIF and EPI on insulin were nonadditive, that both hormones were additive to nickel chloride during inhibition of insulin release, and that they noncompetitively inhibited glipizide-induced insulin secretion through pertussis toxin-sensitive mechanisms. Together, these results suggest that both hormones exert their effects on insulin secretion at multiple G-protein-regulated sites including adenylate cyclase and sites distal to the glipizide-binding site on the KATP channel.
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PMID:G-proteins and hormonal inhibition of insulin secretion from HIT-T15 cells and isolated rat islets. 138 67

The physiological regulation of intestinal proglucagon-derived peptide secretion has not been well studied. We have therefore used a fetal rat intestinal cell culture model to investigate the control of secretion of the gut glucagon-like immunoreactive (GLI) peptides by other intestinal regulatory peptides in vitro. Secretion of the intestinal GLI peptides was found to be stimulated in a dose-dependent fashion by the intestinal endocrine peptide, gastric inhibitory peptide (at greater than or equal to 10(-10) M, P less than 0.05), and by the neurocrine peptides, gastrin-releasing peptide (at greater than or equal to 10(-12) M, P less than 0.05), and calcitonin gene-related peptide (at greater than or equal to 10(-8) M, P less than 0.05). Gastrin-releasing peptide and its amphibian equivalent, bombesin were equipotent in stimulating GLI peptide secretion. In contrast, the endocrine and neurocrine intestinal somatostatin-related peptides, somatostatin-28 and -14, inhibited release of the GLI peptides, at concentrations of 10(-10) (P less than 0.01) and 10(-8) (P less than 0.01) M, respectively, with significant differences in potency between the two peptides detected at 10(-10) M (P less than 0.05). The inhibitory effects of both somatostatin-28 and -14 could be blocked by preincubation of the cells with pertussis toxin (P less than 0.05). Dose-dependent stimulation of gut GLI peptide secretion was also detected in response to treatment of cultured cells with sodium oleate (at 10(-4) M; P less than 0.05), or with the cholinergic agonist bethanecol (at greater than or equal to 100 microM; P less than 0.05). Other endocrine [cholecystokinin, glucagon, glucagon-like peptide-1(1-37), glucagon-like peptide-1(7-37), glucagon-like peptide-2, neurotensin, and peptide YY] and neurocrine (vasoactive intestinal peptide) peptides, and the synthetic glucocorticoid, dexamethasone, were without effect on secretion of the gut GLI peptides, at doses of 10(-12) to 10(-6) M. The results of the present study therefore demonstrate that secretion of the intestinal proglucagon-derived peptides is under the regulatory control of a wide variety of intestinal endocrine and neurocrine peptides, as well as nutrients (fats) and neurotransmitters (acetylcholine).
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PMID:Regulation of intestinal proglucagon-derived peptide secretion by intestinal regulatory peptides. 167 88

Whole-cell voltage-clamp recordings were made from acutely dissociated neurons obtained from the embryonic chick ciliary ganglion. Recording pipettes were filled with salines containing 120 mM CsCl or 120 mM tetraethylammonium-Cl. Application of depolarizing voltage commands evoked L-type Ca2+ currents and, at voltages positive to 0 mV, an unidentified cationic conductance. The unidentified cationic conductances made the Ca2+ currents appear to undergo voltage-dependent inactivation and made a large contribution to tail currents present during repolarizing voltage steps. Ca2+ Ca2+ currents showed little or no sign of inactivation and did not reverse at voltages up to +60 mV. Application of somatostatin-14 or somatostatin-28 produced a reversible inhibition of Ca2+ currents in virtually all cells, regardless of size. Somatostatin-28 (1-14) was inactive. The effects of somatostatin-14 and somatostatin-28 were attenuated by pretreatment with pertussis toxin, suggesting a role for G-proteins in mediating the response. Somatostatin-14 and somatostatin-28 had no effect on voltage-dependent K+ currents. The results suggest that somatostatin peptides modulate the motor output of the chick ciliary ganglion.
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PMID:Properties of Ca2+ currents in acutely dissociated neurons of the chick ciliary ganglion: inhibition by somatostatin-14 and somatostatin-28. 168 10


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