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)

Somatostatin (SRIF) SS-2 binding sites were originally defined in rat brain cerebral cortex membranes using [125I]Tyr11-SRIF-14 in the presence of 120 mM NaCl. These sites were characterized by their high affinity for SRIF-14 and SRIF-28, but very low affinity for cyclic peptides such as octreotide (SMS 201-995) and seglitide (MK 678). The characteristics of SS-2 sites are reminiscent of 125I]CGP 23996-labelled sites in rat brain which have been termed SRIF-2 sites. In the present study, the pharmacological profile of SS-2 sites was determined in radioligand binding studies performed in rat cortex membranes using [125I]SRIF-14 in the presence of 120 mM NaCl and compared to that of human SSTR-1 receptors expressed in human embryonic kidney (HEK 293) cells, using [125I]SRIF-14. The rank orders of affinity of a variety of SRIF analogues and synthetic peptides for SS-2 binding sites and recombinant human SSTR-1 receptors were very similar and correlated highly significantly (r = 0.99). However, SS-2 binding correlated also with binding to recombinant SSTR-4 receptors (r = 0.91). Autoradiographic studies were performed using the radioligand [125I]CGP 23996 which has been claimed to label selectively SRIF-2 binding sites and compared with the distribution of SSTR-1 receptor mRNA determined using in situ hybridization in rat brain. Although some overlap was observed between the distribution of SSTR-1 mRNA and [125I]CGP 23996 binding sites, the latter were clearly more widespread, suggesting this ligand to label SSTR-1 and other sites. In addition, inhibition of forskolin-stimulated adenylate cyclase was investigated in HEK 293 cells transfected with human SSTR-1 receptors; a variety of SRIF analogues and short synthetic peptides behaved as agonists at adenylate cyclase and displayed a rank order of potency highly similar to that observed for these compounds at SS-2 binding sites. Seglitide acted as an antagonist at SSTR-1 receptor mediated inhibition of adenylate cyclase activity with a pKB of 4.42. It is concluded that the pharmacological profile of SS-2 binding sites resembles most closely that of SSTR-1 receptors (although similarities with SSTR-4 receptors were observed), that [125I]CGP 23996 labels presumably several SRIF receptors in rat brain, and that SSTR-1 receptors are negatively and efficiently coupled to adenylate cyclase activity.
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PMID:Pharmacological identity between somatostatin SS-2 binding sites and SSTR-1 receptors. 778 6

The mRNA distribution in the brain and the coupling to cellular effector systems of four somatostatin receptors (SSTR1-4) was studied. All four SRIF receptor subtypes were expressed in cortex and hippocampus. In addition, SSTR1 mRNA was relatively abundant in the spinal cord whereas SSTR2 mRNA was also present in the striatum. The SSTR3 gene was predominantly expressed in the olfactory bulb and in the cerebellum. Conflicting results about the effector coupling of SSTR1-3 have been published previously. We have stably expressed human SSTR1-4 in HEK 293 human embryonal kidney cells. Agonist binding to the receptor subtypes, including the recently cloned SSTR4, inhibited the formation of forskolin-induced cAMP. Is is concluded that, in an appropriate cellular environment, all four receptor subtypes can functionally couple to the inhibition of adenylyl cyclase.
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PMID:Distribution and second messenger coupling of four somatostatin receptor subtypes expressed in brain. 840 11

GH release is thought to occur under the reciprocal regulation of two hypothalamic peptides, GH releasing hormone (GHRH) and somatostatin, via their engagement with specific cell surface receptors on the anterior pituitary somatotroph. In addition, GH-releasing peptides, such as GHRP-6 and the nonpeptide mimetics, L-692,429 and MK-0677, stimulate GH release through their activation of a distinct receptor, the GH secretagogue receptor (GHS-R). The recent cloning of the GHS-R from human and swine pituitary gland identifies yet a third G protein-coupled receptor (GPC-R) involved in the control of GH release and further supports the existence of an undiscovered hormone that may activate this receptor. Using the human GHS-R as a probe, we report the isolation of a rat pituitary GHS-R cDNA derived from an unspliced, precursor mRNA. The rat cDNA encodes a protein of 364 amino acids containing seven transmembrane domains (7-TM) with >90% sequence identity to both the human and swine GHS-Rs. A single intron of approximately 2 kb divides the open reading frame into two exons encoding TM 1-5 and TM 6-7, thus placing the GHS-R into the intron-containing class of GPC-Rs. The intron maps to the site of sequence divergence between the human and swine type 1a and 1b GHS-R mRNAs. In addition, determination of the nucleotide sequence for the human GHS-R gene confirmed the position of an intron in the human GHS-R gene at this position. A full-length contiguous cDNA from rat hypothalamus was isolated and shown to be identical in its nucleotide and deduced amino acid sequence to the rat pituitary GHS-R. The cloned rat GHS-R binds [35S]MK-0677 with high affinity [dissociation constant (K(D)) = 0.7 nM] and is functionally active when expressed in HEK-293 cells. Expression of the rat GHS-R was observed specifically in the pituitary and hypothalamus when compared with control tissues.
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PMID:Molecular analysis of rat pituitary and hypothalamic growth hormone secretagogue receptors. 909 93

G-protein-coupled or 7-transmembrane receptors (7TMRs) are often studied after heterologous expression in mammalian cells such as COS-7, CHO-K1, or HEK-293s. In this paper, we describe the development of a rapid and generic method for producing stable Chinese hamster ovary cell lines expressing high levels of recombinant 7TMRs by N-terminal tagging these proteins with the hemagglutinin (HA) sequence. To illustrate the broad applicability of this technique, we have presented data from cell lines expressing a glycoprotein hormone receptor for follicle-stimulating hormone (FSHR), CXC- (CXCR-2), and CC-chemokine (CCR-1) receptors and peptide receptors from the somatostatin (SSTR1, 2, 5) and neuropeptide Y (NPY-Y2, -Y4 Rs) families. Typically, cell lines with a receptor density of 1 to 15 pmol/mg protein are produced with this method. The presence of the HA tag does not adversely affect the binding or functional activity of the receptors.
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PMID:A generic method for the production of cell lines expressing high levels of 7-transmembrane receptors. 923 98

The type 9 adenylyl cyclase (AC9) is a widely distributed adenylyl cyclase that was originally cloned from a mouse cDNA library. Here we report the cloning, chromosomal mapping, and regulatory properties of human AC9 (HGMW-approved symbol ADCY9). Although the human AC9 sequence shows 86% homology with mouse AC9, divergence at the C2a/C2b junction results in an alternative C2b amino acid sequence. In situ hybridization localized the human AC9 gene to both human and mouse chromosomes 16. AC9 mRNA is present in all tissues examined, with the highest levels found in skeletal muscle, heart, and brain. To characterize the regulatory properties of human AC9 in vivo, the enzyme was expressed in HEK-293 cells. Human AC9 is stimulated by beta-adrenergic receptor activation but is insensitive to forskolin, Ca2+ and somatostatin. In contrast to mouse AC9, the activity of human AC9 is unaffected by inhibitors of calcineurin. These data emphasize the importance of determining the regulatory properties of human adenylyl cyclases.
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PMID:Cloning, chromosomal mapping, and regulatory properties of the human type 9 adenylyl cyclase (ADCY9). 962 27

Utilizing NNC 26-9100 (11) as a structural lead, a variety of nonpeptide derivatives of somatostatin were synthesized and evaluated for sst2 and sst4 receptor binding affinity. A novel thiourea scaffold was utilized to attach (1) a heteroaromatic nucleus to mimic the Trp8 residue, (2) a nonheteroaromatic nucleus to mimic Phe7, and (3) a primary amine or other basic group to mimic the Lys9 residue of somatostatin. Displacement studies were carried out using membranes from cell lines expressing ssts [BHK cells (sst4) and HEK 293 cells (sst2)] utilizing [125I]Tyr11-SRIF as the radioligand. Several thioureas (11, 38, 39, 41, and 42) and the urea 66 exhibited Ki values of less than 100 nM. The thioureas 11 (Ki = 6 nM) and 41 (Ki = 16 nM) and the urea 66 (Ki = 14 nM) are believed to be the most potent nonpeptide sst4 agonists known. Since the thiourea 11 and the urea 66 exhibit high sst4 selectivity, these novel nonpeptide derivatives may be useful tools for studying the sst4 receptor. Studies are currently in progress to evaluate the therapeutic potential of NNC 26-9100 (11) in the treatment of glaucoma.
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PMID:Nonpeptide somatostatin agonists with sst4 selectivity: synthesis and structure-activity relationships of thioureas. 982 40

The activity of native L-type Ca channels can be facilitated by strong depolarizations. The cardiac Ca channel alpha(1C)-subunit was transiently expressed in human embryonic kidney (HEK-293) cells, but these channels did not exhibit voltage-dependent facilitation. Coexpression of the Ca channel beta(1a)- or beta(2a)-subunit with the alpha(1C)-subunit enabled voltage-dependent facilitation in 40% of cells tested. The onset of facilitation in alpha(1C) + beta(1a)-expressing HEK-293 cells was rapid after a depolarization to +100 mV (tau = 7.0 ms). The kinetic features of the facilitated currents were comparable to those observed for voltage-dependent relief of G protein inhibition demonstrated for many neuronal Ca channels; however, intracellular dialysis with guanosine 5'-O-(2-thiodiphosphate) and guanosine 5'-O-(3-thiotriphosphate) in the patch pipette had no effect on facilitation. Stimulation of G protein-coupled receptors, either endogenous (somatostatin receptors) or coexpressed (adenosine A(1) receptors), did not affect voltage-dependent facilitation. These results indicate that the cardiac Ca channel alpha(1C)-subunit can exhibit voltage-dependent facilitation in HEK-293 cells only when coexpressed with an auxiliary beta-subunit and that this facilitation is independent of G protein pathways.
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PMID:Voltage-dependent facilitation of cardiac L-type Ca channels expressed in HEK-293 cells requires beta-subunit. 1064 92

Somatostatin mediates its diverse physiological effects through a family of five G-protein-coupled receptors (sst(1)-sst(5)); however, knowledge about the distribution of individual somatostatin receptor proteins in mammalian brain is incomplete. In the present study, we have examined the regional and subcellular distribution of the somatostatin receptor sst(4) in the rat CNS by raising anti-peptide antisera to the C-terminal tail of sst(4). The specificity of affinity-purified antibodies was demonstrated using immunofluorescent staining of HEK 293 cells stably transfected with an epitope-tagged sst(4) receptor. In Western blotting, the antiserum reacted specifically with a broad band in rat brain, which migrated at approximately 70 kDa before and approximately 50 kDa after enzymatic deglycosylation. sst(4)-Like immunoreactivity was most prominent in many forebrain regions, including the cerebral cortex, hippocampus, striatum, amygdala, and hypothalamus. Analysis at the electron microscopic level revealed that sst(4)-expressing neurons target this receptor preferentially to their somatodendritic domain. Like the sst(2A) receptor, sst(4)-immunoreactive dendrites were often closely apposed by somatostatin-14-containing fibers and terminals. However, unlike the sst(2A) receptor, sst(4) was not internalized in response to intracerebroventricular administration of somatostatin-14. After percussion trauma of the cortex, neuronal sst(4) receptors progressively declined at the sites of damage. This decline coincided with an induction of sst(4) expression in cells with a glial-like morphology. Together, this study provides the first description of the distribution of immunoreactive sst(4) receptor proteins in rat brain. We show that sst(4) is strictly somatodendritic and most likely functions in a postsynaptic manner. In addition, the sst(4) receptor may have a previously unappreciated function during the neuronal degeneration-regeneration process.
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PMID:Distribution, targeting, and internalization of the sst4 somatostatin receptor in rat brain. 1080 19

Orexins (hypocretins) are recently discovered excitatory transmitters implicated in arousal and sleep. Yet, their ionic and signal transduction mechanisms have not been fully clarified. Here we show that orexins suppress G-protein-coupled inward rectifier (GIRK) channel activity, and this suppression is likely to lead to neuronal excitation. Cultured neurons from the locus coeruleus (LC) and the nucleus tuberomammillaris (TM) were used, as well as HEK293A cells transfected with GIRK1 and 2, either human orexin receptor type 1 (OX1R) or type 2 (OX2R), mu opioid receptor and GFP cDNAs. In GTPgammaS-loaded cells, orexin A (OXA, 3 microM) inhibited GIRK currents that had previously been activated by somatostatin (in LC cells), nociceptin (TM cells), or the mu opioid agonist DAMGO (HEK cells). In guanosine triphosphate (GTP)-loaded HEK cells, in which GIRK currents were not preactivated, OXA induced a biphasic response through both types of orexin receptors: an initial current increase and a subsequent decrease to below resting levels. Current-voltage (I-V) relationships revealed that both the OXA-induced and suppressed currents are inwardly rectifying with reversal potentials around EK. The OXA-induced initial current was partially pertussis toxin (PTX) sensitive and partially PTX insensitive, whereas the OXA-suppressed current was PTX insensitive. These data suggest that orexin receptors couple with more than one type of G-protein, including PTX-sensitive (such as Gi/o) and PTX-insensitive (such as Gq/11) G-proteins. The modulation of GIRK channels by orexins may be one of the cellular mechanisms for the regulation of brain nuclei (e.g., LC and TM) that are crucial for arousal, sleep, and appetite.
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PMID:Effects of orexin (hypocretin) on GIRK channels. 1270 4

In the last few years, significant experimental evidence has accumulated showing that many G protein coupled receptors (GPCRs) are structurally and perhaps functionally homodimers. Recently, a number of studies have demonstrated that many GPCRs, notably GABA(B), somatostatin, and delta and kappa opioid receptors form heterodimers, as well. Based on these observations, we undertook a pharmacological and functional analysis of HEK 293 cells transiently transfected with the beta1AR or beta2AR or with both subtypes together. High-affinity binding for subtype-specific ligands (betaxolol and xamoterol for the beta1AR, and ICI 118,551 and procaterol for the beta2AR) was detected in cells expressing the cognate receptors alone with values similar to those reported in the literature. However, a significant portion of these high-affinity interactions were lost when both receptors were expressed together while nonspecific ligands (propranolol and isoproterenol) retained their normal affinities. When competition assays were performed with each subtype-specific ligand in the presence of a constant concentration of the other subtype-specific ligand, the high-affinity binding site was rescued, suggesting that the two receptor subtypes were interacting in a fashion consistent with positive cooperativity. Our data suggest that the beta1AR and beta2AR can form heterodimers and that these receptors have altered pharmacological properties from the receptor homodimers.
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PMID:Pharmacological characterization of putative beta1-beta2-adrenergic receptor heterodimers. 1271 May 33


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