Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The components of fat cell membranes responsible for the binding of insulin were solubilized by treatment with the nonionic detergent Triton X-100. By using a polyethylene glycol precipitation method to assay specific insulin binding, the soluble preparation was shown to have insulin-binding characteristics similar to those of intact fat cells. Further studies of this preparation by polyacrylamide gel electrophoresis in the presence of (125)I-labeled insulin demonstrated two distinct insulin binding activities, designated species I and II. The two species were separated by electrophoresis in the absence of iodo-labeled hormone and eluted from the gel. Scatchard analysis of the insulin binding data for species I showed a curvilinear plot with the initial portion having a K(d) of 1.3 x 10(-10) M. The Scatchard plot for species II was linear with a K(d) of 6.0 x 10(-9) M. Desoctapeptide insulin and glucagon failed to compete for the insulin-binding sites in both species whereas desalanine insulin was an effective competitor. High concentrations of proinsulin competed with the iodo-labeled hormone for binding to species I but not to species II. In the presence of a low concentration of (125)I-labeled insulin (0.3 nM) some species I activity appeared to be converted to species II activity; there was no evidence of interconversion between the two species in the absence of insulin. Neither species degraded insulin as measured by trichloroacetic acid precipitation or rebinding to intact fat cells. These findings indicate the existence in the adipocyte plasma membrane of two insulin-binding species that have distinct physicochemical properties.
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PMID:Insulin binding to solubilized material from fat cell membranes: evidence for two binding species. 27 28

The HLB dependency for the solubilization of membrane proteins and adenylate cyclase activity from a plasma membrane-enriched fraction from rat liver has been determined. The HLB (hydrophilic/lipophilic/balance) number of a detergent is an empirical measure of its relative hydrophobicity. Detergent HLB numbers vary systematically with the length of the ethylene oxide chain for a homologous series of detergents such as the Triton X series. These detergents have a constant hydrophobic moiety, octylphenyl, and a variable polar portion, polyethoxyethanol. Basal-NaF-epinephrine-, and glucagon-stimulated adenylate cyclase activities were solubilized in the HLB range of 16.8-17.4. Solubilization was most effective in 0.01 M Tris buffers at pH 7.5 containing 1-5 mM mercaptoethanol, 1 mM MgCl2, and 0.1% Triton X-305. The detergent to membrane protein ratio used in these studies was 3:1. Criteria for solubilization included lack of sedimentation at 100,000 X g, the absence of particulate material in the supernatant when examined by electron microscopy, and inclusion of hormonally sensitive adenylate cyclase activity in Sephadex G-200 gels. The apparent molecular weight of the solubilized enzyme was approximately 200,000 in the presence of Triton X-305. The solubilized enzyme was stimulated 5-fold by NaF, 7-fold by glucagon, and 20-fold by epinephrine compared to the particulate enzyme used in this study which was stimulated 10-fold, 3.4-fold, and 4-fold by NaF, epinephrine, and glucagon, respectively. The solubilized enzyme is stable for several weeks when stored at -60 degrees C.
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PMID:The HLB dependency for detergent solubilization of hormonally sensitive adenylate cyclase. 126 11

Glucagon-like peptide-1 (7-36)amide (GLP-1 (7-36)amide) represents a physiologically important incretin in mammals including man. Receptors for GLP-1 (7-36)amide have been described in RINm5F cells. We have solubilized active GLP-1(7-36)amide receptors from RINm5F cell membranes utilizing the detergents octyl-beta-glucoside and CHAPS; Triton X-100 and Lubrol PX were ineffective. Binding of radiolabeled GLP-1(7-36)amide to the solubilized receptor was inhibited concentration-dependently by addition of unlabeled peptide. Scatchard analysis of binding data revealed a single class of binding sites with Kd = 0.26 +/- 0.03 nM and Bmax = 65.4 +/- 21.24 fmol/mg of protein for the membrane-bound receptor and Kd = 22.54 +/- 4.42 microM and Bmax = 3.9 +/- 0.79 pmol/mg of protein for the solubilized receptor. The binding of the radiolabel to the solubilized receptor was dependent both on the concentrations of mono- and divalent cations and the protein/detergent ratio in the incubation buffer. The membrane bound receptor is sensitive to guanine-nucleotides, however neither GTP-gamma-S nor GDP-beta-S affected binding of labeled peptide to solubilized receptor. These data indicate that the solubilized receptor may have lost association with its G-protein. In conclusion, the here presented protocol allows solubilization of the GLP-1(7-36)amide receptor in a functional state, and opens up the possibility for further molecular characterization of the receptor protein.
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PMID:Solubilization of active GLP-1 (7-36)amide receptors from RINm5F plasma membranes. 131 74

Pituitary adenylate-cyclase-activating polypeptide (PACAP), a novel brain-gut hormone, was isolated from ovine hypothalami and represents the latest mammalian member of the secretin-glucagon peptide family. PACAP exists in two C-terminally amidated molecular forms, PACAP(1-27) and PACAP(1-38), comprising 27 or 38 amino acid residues, respectively. In order to identify a specific receptor for PACAP, we studied binding of 125I-labelled PACAP(1-27) to plasma membranes from rat brain. We identified a single high-affinity binding site (Kd, 340 pM and Bmax, 3.34 pmol/mg), specific for synthetic PACAP(1-38) and PACAP(1-27). Hormone binding was reversible and time, protein and temperature dependent. In contrast, neither the analogues PACAP(1-23), PACAP(18-38) and PACAP(3-25), nor vasoactive intestinal peptide (VIP), secretin and growth-hormone-releasing factor (GRF) revealed significant binding at concentrations up to 1 microM. A specific receptor protein, with an apparent molecular mass of 60 kDa, was identified by means of affinity cross-linking with disuccinimidyl suberate (DSS) and ethylene glycol disuccinimidyl suberate (EGS). PACAP receptors are associated with a GTP-binding protein as determined by the influence of different nucleotides on PACAP binding. PACAP-binding activity was solubilized with the detergents 3-[(3-cholamidopropyl)dimethylammonio]2-hydroxy-1-propane sulfonate (Chapso) or Triton X-100 and was characterized as a high-molecular-mass receptor complex (400 kDa) by non-reducing size-exclusion chromatography on Sepharose CL-6B. These data imply the following: high-affinity PACAP receptors are expressed abundantly on rat-brain plasma membranes; PACAP receptors are specific for PACAP and show no affinity for VIP, secretin and GRF; the PACAP receptor molecule has an apparent molecular mass of 60 kDa; the PACAP receptor complex is associated with a GTP-binding protein.
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PMID:Characterization of a guanosine-nucleotide-binding-protein-coupled receptor for pituitary adenylate-cyclase-activating polypeptide on plasma membranes from rat brain. 166 20

This report describes a new method for detecting and quantitating those immunoglobulins G (IgG) in serum that are related to Graves' disease. The method is based on previous observations which indicate that the guinea pig fat cell membrane (FCM) is capable of binding Graves'-specific IgG, but does not bind the IgG common to Graves' disease and Hashimoto's disease, such as antimicrosomal antibodies. Crude FCM preparations were iodinated by a lactoperoxidase technique and were then treated with Triton X-100 to yield a solubilized radioiodinated FCM (SFCM) preparation. SFCM, which retained bovine (b) TSH binding and Graves'-IgG binding properties, provided a radioactively labeled receptor with which to test for the presence of fat cell-binding IgG (FBI) in immunoprecipitates prepared by reacting these IgG with antibody against the Fc fragment of human IgG. FBI values (percentage of added SFCM bound to immunoprecipitate; mean + SD) in IgG from 16 patients with thyrotoxicosis caused by Graves' disease (6.0 +/- 1.7) were completely separated from those in IgG from 16 normal subjects (0.4 +/- 0.3). IgG from 2 hypothyroid patients with Hashimoto's disease, which were strongly positive in the TSH binding inhibition (TBI) assay, yielded FBI values within the range in Graves' disease, but values in TBI-negative IgG from 15 other patients with Hashimoto's disease were normal (0.0 +/- 0.9). Moderately false positive FBI values were found in the IgG of 15 patients with rheumatoid arthritis or systemic lupus erythematosis, all rheumatoid factor positive, 3 of which were also TBI positive. In IgG from Graves' disease and those from patients with TBI-positive collagen-vascular disease, binding of SFCM was inhibited by bTSH in a dose-dependent manner. As with binding of TSH to thyroid plasma membranes, similar but less potent inhibition of binding of IgG to SFCM was produced by LH, FSH, and hCG, but not by insulin, glucagon, PRL, or ACTH. FBI values in TBI-negative IgG from patients with collagen-vascular disease were also decreased by TSH, but higher concentrations of bTSH were required. In 40 IgG from among the various clinical groups tested, a significant correlation was found between FBI values and TBI activity (r = 0.48; P less than 0.01). In addition, among 10 IgG from Graves' disease and 6 from collagen-vascular disease patients, a very close correlation (r = 0.89; P less than 0.001) was noted between their TBI activity and the extent to which their FBI values were decreased by a standard concentration of bTSH.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Detection and measurement of fat cell-binding immunoglobulins: a new method applicable to the diagnosis and study of Graves' disease. 299 73

Insulin binding was studied in rabbit semimembranosus proprius and psoas major muscles composed of slow-twitch oxidative (SO) and fast-twitch glycolytic (FG) fibers, respectively. For this purpose, we developed a technique using cryostat microtome muscle slices. Degradation of 125(I)-insulin during the incubation period was prevented by the addition of 1 mM bacitracin in the buffer. Specific binding to muscle slices plateaued by the 24 hrs. of incubation at 4 degrees C. It increased as a function of the amount of muscle, with a maximum binding occurring at about 5 mg of muscle slices. Triton X-100 has been shown to increase specific binding from a critical concentration of 10(-4) M with a maximum effect occurring at 3.3 10(-4) M. Under this condition, the binding was specific since displacement studies showed no inhibition of 125(I)-insulin binding by GH, HCG, ACTH and glucagon, whereas half maximal inhibition was achieved using 5 10(-10) M insulin, 3 10(-9) M IGF1 and 2 10(-8) M proinsulin. The analysis of the binding data yielded curvilinear Scatchard plots. The number of high affinity insulin receptors was higher in the SO muscle than in the FG muscle (4.3 +/- 0.7 vs 0.7 +/- 0.2 fmol/mg fresh muscle; P less than 0.001) with similar high affinity dissociation constants (Kd = 1.5 10(-10) M). Analogous results were obtained using muscle microsomal fractions. The differences in insulin binding might be related to the more intense metabolism of SO fibres which contract more often than FG fibres in vivo.
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PMID:Characterization of insulin binding to slices of slow and fast twitch skeletal muscles in the rabbit. 353 33

125I-glucagon binding and degradation were studied in highly purified plasma membranes from rat livers. Specific 125I-glucagon binding increased rapidly with time at 30 degrees C and reached a maximum between 30 and 120 min. At 120 min the labelled material present in the supernatants from incubation mixtures had extensively lost its ability to rebind to fresh membranes whatever the glucagon concentration. This impairment was not due to the release of a degradative activity into the incubation mixture, suggesting a membrane-mediated process. The presence of proteinase inhibitors (bacitracin/aprotinin) resulted both in an increase in specific 125I-glucagon binding to membranes and an improvement in the ability of the labelled material from the supernatant to rebind to fresh membranes. When analysed by Bio-Gel P-10 chromatography the loss in the ability of the labelled material in the supernatants to rebind to fresh membranes correlated with a decrease in the labelled material which eluted as 125I-glucagon from the column. Chromatographic analysis overestimated 125I-glucagon when compared to the radioreceptor assay. The labelled material extracted from membranes by Triton X-100 solubilization or dissociated from membranes after exposure to an excess of unlabelled glucagon mainly eluted as 125I-glucagon. However, a significant amount (20-30%) of the labelled material eluted in the low molecular weight region.
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PMID:Binding and degradation of 125I-glucagon by highly purified rat liver plasma membranes. 376 3

Incubation of rat adipocytes with the same range of noradrenaline concentrations that stimulate lipolysis caused a rapid and stable decrease in the activity of fatty acyl-CoA synthetase. Corticotropin, glucagon and dibutyryl cyclic AMP also decreased the activity of the enzyme. The effect of noradrenaline was apparent over a wide range of concentrations for the three substrates of the enzyme. A novel fluorescence assay of fatty acyl-CoA synthetase using (1,N6-etheno)-CoA is described. The effect of noradrenaline was not abolished by inclusion of albumin in homogenization buffers, persisted through subcellular fractionation and isolation of microsomes (microsomal fractions) and even survived treatment of microsomes with Triton X-100. The effect of noradrenaline was rapidly reversed within cells by the subsequent addition of insulin or propranolol. The inclusion of fluoride in homogenization buffers did not alter the observed effect of noradrenaline. Additions of cyclic AMP-dependent protein kinase to adipocyte microsomes caused considerable phosphorylation of microsomal protein by [gamma-32P]ATP, but did not affect the activity of fatty acyl-CoA synthetase.
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PMID:Reversible inactivation by noradrenaline of long-chain fatty acyl-CoA synthetase in rat adipocytes. 388 97

1. Guanylate cyclase activity was determined in homogenates of guinea-pig islets of Langerhans by measurement of the conversion of [alpha-(32)P]GTP into cyclic [(32)P]GMP, the reaction products being separated on columns of neutral alumina. 2. The pH optimum of the enzyme was 7.3; it showed a requirement for bivalent cations, the effectiveness of the cations tested being Mn(2+)>>Ca(2+)>Mg(2+). 3. About 70% of enzyme activity was sedimented by centrifugation at 105000g for 60min; activity was increased 2.3-fold by treatment of homogenates with 0.1% Triton X-100. 4. Guanylate cyclase activity of homogenates was increased by acetylcholine, secretin or pancreozymin, but was inhibited by adrenaline, noradrenaline or ATP. Insulin, glucagon, prostaglandins E(1) or E(2), glucose, F(-), diazoxide or glibenclamide were ineffective. 5. Determination of cyclic GMP amounts in islets by radioimmunoassay showed a basal concentration of 2.0pmol/mg of protein, which was increased by incubation of the islets in the presence of acetylcholine or the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, but was unaffected by glucose. 6. Dibutyryl cyclic GMP had significant stimulatory effects on rates of insulin biosynthesis in isolated rat islets of Langerhans. 7. These results suggest a possible role for cyclic GMP in the regulation of insulin biosynthesis and secretion.
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PMID:Regulation of guanylate cyclase in guinea-pig islets of Langerhans. 415 94

The adenylate cyclase system of normal mouse islets was characterized. The pH optimum of the system was 7.6. The enzyme preparation contained particulate phosphodiesterase activity. This could be removed by treatment with 0.4% (v/v) Triton X-100 or inhibited by 8mm-theophylline in the presence of 2mm-cyclic AMP (adenosine 3':5'-cyclic monophosphate). ATP at 0.32mm produced one-half maximal enzyme activity. The enzyme was stimulated in the presence of F(-) and strongly inhibited by Ca(2+). The isolated enzyme retained hormonal sensitivity and was stimulated by glucagon, pancreozymin and secretin at physiological concentrations. Glucose at 17mm, 8mm and 2mm had no direct effect on the activity of the enzyme; neither did galactose at the same concentrations. Groups of islets incubated in 17mm- or 2mm-glucose for 5 or 15min and then homogenized and assayed for adenylate cyclase activity showed no differences in adenylate cyclase activity. The results suggest that the mechanism of glucose-mediated insulin release is not via the adenylate cyclase system. Hormones, however, could mediate insulin secretion via their effects on the adenylate cyclase system.
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PMID:Insulin release from mouse islets. Effect of glucose and hormones on adenylate cyclase. 434 73


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