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)

Rat brain somatostatin (SRIF) receptors were solubilized in an active form with the detergent 3-[(cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). Solubilized SRIF receptors were detected with the stable SRIF analog 125I-MK 678. CHAPS solubilized approximately 30% of membrane-bound SRIF receptors. 125I-MK 678 binding to the solubilized SRIF receptors reached equilibrium by 90 min and dissociated from the receptor with a t1/2 of 60 min. The binding of 125I-MK 678 to the solubilized SRIF receptor was of high affinity and was selective. The characteristics of 125I-MK 678 binding to the solubilized and membrane-bound SRIF receptors were similar. The solubilized brain SRIF receptor specifically bound to a wheat germ agglutinin-Sepharose column, suggesting that it is a glycoprotein. Analysis of the solubilized SRIF receptor by gel exclusion chromatography on an AcA 34 Ultrogel column revealed that its molecular mass is approximately 400 kDa. This mass is probably representative of the receptor complexed with other proteins or molecules. Further characterization of the fractionated 400-kDa species by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting indicated that Gi and Go may be associated with the solubilized SRIF receptor. This is supported by the finding that guanosine-5'-O-(3-thio)triphosphate abolished 125I-MK 678 binding to the solubilized SRIF receptor. Antibodies directed against a synthetic peptide corresponding to a region of the C-terminal of Gia, which specifically immunoprecipitate Gia, immunoprecipitated over 24% of the solubilized SRIF receptor, suggesting that the receptor, in part, is coupled to Gi. These studies describe for the first time the characterization of the solubilized SRIF receptor in an active form. The ability to solubilize the SRIF receptor should allow for further characterization of its physical properties.
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PMID:Solubilization of active somatostatin receptors from rat brain. 197 Oct 88

We characterized structurally the receptors for somatostatin in rat cerebral cortex by affinity labeling with [125I-Tyr1] somatostatin. [125I-Tyr1] somatostatin was cross-linked to cerebrocortical membranes using photoreactive cross-linker: N-5-azido-2-nitrobenzoyloxy-succinimide. Analysis by autoradiography revealed a broad band centered at Mr = 72,000 in the presence or absence of dithiothreitol. Affinity labeling of and specific [125I-Tyr1] somatostatin binding to cerebrocortical membranes were decreased similarly by adding unlabeled somatostatin or nonhydrolyzable guanine nucleotide analogue, guanyl-5'-yl imidodiphosphate, in a dose dependent manner. The pretreatment of cerebrocortical membranes with islet activating protein resulted in a decrease in subsequent affinity labeling of the protein. The cross-linked protein could be solubilized with Zwittergent 3-12 and poorly with digitonin, triton X-100 and NP-40. When exposed to agarose-coupled lectins, the solubilized labeled protein was absorbed to wheat germ agglutinin, partially to ricin communis-II, and not to concanavalin A or lentil lectin. The Mr = 72,000 protein bound to wheat germ agglutinin-agarose was eluted with not only N,N',N"-triacetylchitotriose but also N-acetylglucosamine. These results suggest that somatostatin receptors on cerebrocortical membranes are a monomeric glycoprotein with a Mr = 70,000 containing no disulfide-linked binding subunit, which is coupled to islet activating protein-sensitive guanine nucleotide regulatory protein.
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PMID:[Structural characterization of the somatostatin receptors on rat cerebrocortical membranes]. 198 Aug 94

We have examined the binding of factors in rat liver nuclear extracts to the phosphoenolpyruvate carboxykinase (PEPCK) gene cyclic AMP (cAMP) response element (CRE) and other CREs and have isolated a rat liver CRE-binding protein (CREBP) cDNA. In addition, we have examined the influence of altering the phosphorylation state of nuclear factors on both CRE binding and in vitro transcription. Specific binding to the PEPCK CRE was measured in a mobility shift assay. CRE sequences of the PEPCK, somatostatin, and glycoprotein hormone alpha subunit genes competed equally for binding of rat liver nuclear factors to the PEPCK CRE, whereas mutant PEPCK CRE sequences did not compete for binding. Oligonucleotides complementary to rat pheochromocytoma CREBP (Gonzalez et al., Nature [London] 337:749-752, 1989) were used to prime rat liver and brain cDNA in the polymerase chain reaction. The predominant CREBP molecule obtained was identical to the rat pheochromocytoma CREBP except for a 14-amino-acid deletion in the N-terminal half that was also present in a human placental cDNA (Hoeffler et al., Science 242:1430-1433, 1988). The regulation of transcription by cAMP was examined by coincubation of rat liver nuclear extract with the purified catalytic subunit of cAMP-dependent protein kinase (protein kinase A). Although binding to the CRE was unaffected, in vitro transcription directed by the PEPCK promoter was stimulated by catalytic subunit, and this effect was blocked by protein kinase inhibitor peptide. In contrast, when nuclear extract was coincubated with phosphatase, there was substantial inhibition of in vitro transcription directed by the PEPCK promoter, but there was no effect on binding to the CRE. The major effects of catalytic subunit were exerted through the CRE, but residual stimulation was evident in promoter fragments containing only the TATA element. These data suggest that factors are bound to the CRE at constitutively high levels and that their capacity for transcriptional activation is regulated by phosphorylation.
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PMID:Cyclic AMP-dependent protein kinase regulates transcription of the phosphoenolpyruvate carboxykinase gene but not binding of nuclear factors to the cyclic AMP regulatory element. 214 84

Somatostatin (SRIF) induces its biological actions by binding to and stimulating membrane-associated receptors. To investigate the molecular mechanisms by which SRIF induces its biological effects, we have characterized the biochemical properties of SRIF receptors. SRIF receptors can be solubilized in an active form with the detergent CHAPS and can be detected with the high-affinity SRIF analog [125I]MK 678. The pharmacological characteristics of solubilized SRIF receptors from brain are similar to the receptors in membranes, suggesting that the solubilized receptors retain their biological activity. Solubilized SRIF receptors appear to be tightly associated with GTP-binding proteins, since analogs of GTP can greatly reduce agonist labeling of the solubilized SRIF receptor. The solubilized SRIF receptor migrates as a mass of approximately 400 kd and is a glycoprotein since it can specifically interact with lectin columns. The solubilization of the SRIF receptor has allowed for its purification by affinity chromatography. The purified SRIF receptor migrates as a mass of 60 kd in denaturing gels. Using affinity chromatography, the receptor can be purified to near homogeneity. Present studies are directed toward sequencing and cloning cDNA encoding the SRIF receptor in order to further characterize its physical properties and expression.
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PMID:Biochemical properties of somatostatin receptors. 216 74

The diagnosis of "poorly differentiated" carcinoma was made in 47 of 683 colon cancers on the basis of conventional light microscopy which showed poorly defined glands, solid architecture or variable admixtures thereof. Samples from 44 of these 47 tumors were assessed by immunohistochemical analysis for the presence of neuroendocrine (NE) antigens. Paraffin sections were immunostained with antibodies to NSE, chromogranin, serotonin, VIP, substance P and somatostatin. Additional sections were also stained with monoclonal antibody (Mab) A-80 that recognizes a glycoprotein related to exocrine (EX) differentiation. Based on our findings, the tumors were phenotypically reclassified as follows: I) pure EX (n = 8), II) pure NE (n = 4), III) mixed EX-NE carcinomas (n = 23), and IV) predominantly EX carcinomas with occasional NE cells (n = 9). Survival among groups II and III appeared to be less than group I and survival in group IV was significantly less than group I. Survival among the four pure NE (group II) and 11 predominantly NE mixed carcinomas (group III) taken together was significantly less than the pure EX carcinomas. This study indicates: 1) The incidence of NE differentiation in tumors of the colon and rectum is higher than previously believed. 2) The poorly differentiated colon carcinomas comprise four distinct groups: pure EX, pure NE, mixed EX-NE carcinomas, and predominantly EX carcinomas with a NE cell subpopulation. 3) The presence of NE differentiation or of a NE cell subpopulation in colon carcinoma appears to be associated with a poorer prognosis.
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PMID:Neuroendocrine differentiation in "poorly differentiated" colon carcinomas. 236 84

Eighty colon carcinomas reflecting the histologic spectrum were studied immunohistochemically; their epithelial characteristics had been established by demonstrating cytokeratin polypeptides. Paraffin sections were immunostained with monoclonal antibody (Mab) A-80 that recognizes a mucin-like glycoprotein related to exocrine differentiation. Sequential sections were immunostained with neuroendocrine (NE) differentiation antibodies: NSE, human chromogranin A, serotonin, somatostatin, substance P and VIP. Twenty-one/80 carcinomas immunoreacted exclusively with Mab A-80; these included adenocarcinomas with variably defined glands, colloid, "solid", and linitits plastica carcinomas. Eleven/80 carcinomas immunoreacted only with antibodies to NE markers. Twenty-nine/80 carcinomas of histologically variable patterns expressed both exocrine and NE antigens. A notable group of 19 adenocarcinomas immunostaining with Mab A-870 included a minority NE cell subpopulation. We tentatively conclude that given a limited battery of immunoprobes, colon carcinomas comprise 4 groups: 1) pure exocrine carcinomas, 2) pure NE carcinomas, 3) mixed exocrine and NE carcinomas, and 4) exocrine carcinomas with occasional NE cells. Thus, phenotypically mixed exocrine and NE carcinomas comprise the largest group while the second largest group exhibited exclusively features of exocrine phenotype. Preliminary clinical correlative data indicate that pure NE colon carcinomas behave more aggressively than their exocrine counterparts; moreover, colon carcinomas containing a NE subpopulation, even if small, also seem to behave worse than their counterparts without an NE subpopulation.
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PMID:Immunohistochemical analysis of colon carcinomas applying exocrine and neuroendocrine markers. 246 47

The glycoprotein hormone alpha-gene is preferentially expressed in placental cell lines, but it is also expressed in several other cell lines indicating that the differential activity of the alpha-gene regulatory elements in various cell types is more quantitative than qualitative. The 5'-flanking region of the alpha-gene contains several distinct DNA regulatory sequences including an upstream regulatory element [(URE) -181 to -150 base pairs (bp)] that stimulates basal expression and an 18 bp twice-repeated cAMP-responsive element [(CRE) -146 to -111 bp]. We constructed an array of fusion genes containing the URE and/or the CRE linked to different truncated promoters [alpha-gene, somatostatin (SRIF), glucagon, Simian Virus 40]. These constructions were transiently expressed in placental, fibroblast, or islet cell lines to identify regulatory sequences involved in cell-specific expression as well as interactions between the URE, the CRE, and different promoter elements. The URE, CRE, and alpha-promoter elements contribute approximately 3-, 6-, and 5-fold, respectively, to preferential expression in JEG-3 cells. In JEG-3 cells, the URE is strictly dependent on the CRE for activity, but it functions in a promoter-independent manner. In contrast, the CRE is markedly promoter dependent. When linked to heterologous enhancers, the alpha-promoter is more active in JEG-3 cells than in other cell lines, thereby contributing substantially to preferential expression in placental cells. Although the CREs derived from the alpha and SRIF genes both activate expression of the alpha promoter, only the alpha CRE activates the SRIF promoter in JEG-3 cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Enhancer and promoter element interactions dictate cyclic adenosine monophosphate mediated and cell-specific expression of the glycoprotein hormone alpha-gene. 247 27

Heterotopic gastric mucosa in the rectum is particularly uncommon; only 23 cases have been reported to date. Moreover, no studies have been done on the neuroendocrine apparatus and glycoprotein production of the heterotopic mucosa. This study reports on a 13-year-old boy, admitted with rectal bleeding and persistent tenesmus. An ulcerative lesion was found on colonoscopy; biopsies revealed a fundic-type gastric tissue. Medical therapy (H2-blockers) promptly healed the rectal ulcer; surgical excision of the heterotopia was performed with complete and permanent relief of symptoms (3-year follow-up). Immunocytochemistry (PAP) revealed 5-Ht and somatostatin cells in the gastric-type mucosa, as in the normal human stomach. These cells also were present in the surrounding rectal epithelium where PYY-enteroglucagon cells were detected, which were absent in the heterotopic tissue. Mucin histochemistry showed PAS-positive cells also strongly stained by LA lectin in the heterotopic tissue, differentiating the rectal epithelium that remained unstained. Therefore, the morphofunctional status (endocrine cells and mucins) of the gastric heterotopia was almost identical to its orthotopic counterpart, confirming the hypothesis that endocrine cells and mucin-producing cells differentiate their metabolic products according to the anatomic and functional activity of the epithelium where they grow.
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PMID:Heterotopic gastric mucosa of the rectum--characterization of endocrine and mucin-producing cells by immunocytochemistry and lectin histochemistry. Report of a case. 256 45

The physical properties of brain and pituitary somatostatin receptors were characterized using photocrosslinking techniques. Somatostatin receptors in rat corpus striatum and anterior pituitary membranes were covalently bound to the non-reducible somatostatin analog, [125I]CGP 23996, using the crosslinking agent n-hydroxysuccinimidyl-4-azidobenzoate and ultraviolet light. In striatal membranes, a protein of 60,000 mol. wt was labeled by [125I]CGP 23996. The binding was potently inhibited by somatostatin analogs but not by other biologically active peptides. The labeling of the 60,000 mol. wt protein by [125I]CGP 23996 was diminished by guanine triphosphate gamma thiol, which is consistent with the labeling of a somatostatin receptor coupled to guanine triphosphate binding proteins. The migration of the [125I]CGP 23996 labeled 60,000 mol. wt protein in native sodium dodecyl sulfate-gels was not affected by the reducing agent dithiothreitol, indicating that there is a general lack of disulfide bridges in the striatal somatostatin receptor. The striatal somatostatin receptor was solubilized with the detergent 3-[(3-cholamidopropyl)-dimethylaminoio]-1-propanesulfonate and specifically bound to the lectin wheat germ agglutinin, suggesting that the striatal somatostatin receptor is a glycoprotein. [125I]CGP 23996 also labeled a 60,000 mol. wt protein in anterior pituitary membranes. The characteristics of [125I]CGP 23996 binding to anterior pituitary membranes were consistent with the labeling of a somatostatin receptor. Interestingly, a comparison of the [125I]CGP 23996 labeled material from striatal and anterior pituitary membranes by two-dimensional polyacrylamide gel electrophoresis revealed the presence of several striatal somatostatin receptors of varying charge (pI values between 6 and 6.5) but only a single pituitary receptor. These findings indicate that physical differences may exist between subtypes of somatostatin receptors.
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PMID:Biochemical properties of brain somatostatin receptors. 257 Mar 75

Somatostatin receptors of plasma membranes from beta cells of hamster insulinoma were covalently labelled with 125I-[Leu8,D-Trp22,Tyr25]somatostatin-28 (125I-somatostatin-28) and solubilized with the non-denaturing detergent Triton X-100. Analysis by SDS/PAGE and autoradiography revealed three specific 125I-somatostatin-28 receptor complexes with similar molecular masses (228 kDa, 128 kDa and 45 kDa) to those previously identified [Cotroneo, P., Marie, J.-C. & Rosselin, G. (1988) Eur. J. Biochem. 174, 219-224]. The major labelled complex (128 kDa) was adsorbed to a wheat-germ-agglutinin agarose column and eluted by N-acetylglucosamine. Also, the binding of 125I-somatostatin-28 to plasma membranes was specifically inhibited by the GTP analog, guanosine-5'-O-(3-thiotriphosphate) (GTP[S]) in a dose-dependent manner. Furthermore, when somatostatin-28 receptors were solubilized by Triton X-100 as a reversible complex with 125I-somatostatin-28, GTP[S] specifically dissociated the bound ligand to a larger extent from the soluble receptors than from the plasma-membrane-embedded receptors, the radioactivity remaining bound after 15 min at 37 degrees C being 30% and 83% respectively. After pertussis-toxin-induced [32P]ADP-ribosylation of pancreatic membranes, a 41-kDa [32P]ADP-ribose-labelled inhibitory guanine nucleotide binding protein coeluted with the 128-kDa and 45-kDa receptor complexes. The labelling of both receptor proteins was sensitive to GTP[S]. The labelling of the 228-kDa band was inconsistent. These results support the conclusion that beta cell somatostatin receptors can be solubilized as proteins of 128 kDa and 45 kDa. The major labeled species corresponds to the 128-kDa band and is a glycoprotein. The pancreatic membrane contains a 41-kDa GTP-binding protein that can complex with somatostatin receptors.
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PMID:Solubilization of somatostatin receptors in hamster pancreatic beta cells. Characterization as a glycoprotein interacting with a GTP-binding protein. 257 68


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