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)

Proglucagon (proG) is processed in a tissue-specific manner to glucagon in the pancreas and to gilcentin, oxyntomodulin, glucagon-like peptide (GLP)-1, and GLP-2 in the intestine. Recombinant vaccinia virus (vv) vectors were used to infect prohormone convertase 1 (PC1) or PC2 into nonendocrine (BHK-proG) cells, which stably express proG. Similarly, endocrine (GH3, AtT-20) cells were coinfected with proG along with PC1 or PC2 alone, or in combination with furin, PACE4, PC5a, or PC5b. Cell extracts were analyzed for various proG-derived peptides by RIA of fractions obtained from HPLC. Upon infection of BHK-proG cells with either vv: furin or vv:PC1, glicentin was produced, while vv: PC2 did not process proG. In GH3 and AtT-20 cells, vv:PC1 produced glicentin, oxyntomodulin, GLP-1(1-37), GLP-1(7-37), and GLP-2. All other enzymes tested produced only glicentin. Interestingly, no enzyme or combination produced glucagon. Coinfection of GH3 cells with vv:PC2 and members of the chromogranin family of peptides, including chromogranin A and B and secretogranin II, as well as the PC2-binding protein 7B2, did not result in processing to glucagon. It is concluded that: 1) PC1 is responsible for the processing of proG to produce the intestinal peptides glicentin, oxyntomodulin, GLP-1(1-37), GLP-1(7-37), and GLP-2, and 2) PC2 processes proG to glicentin but does not produce glucagon, alone or in combination with other enzymes or with known molecular chaperones.
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PMID:Role of prohormone convertases in the tissue-specific processing of proglucagon. 872 80

The indirect peroxidase method was employed to study the endocrine pancreas of the Cape fur seal. Immunoreactivity to insulin was confined to the cores of the islets and the insulin cells were more abundant than the other endocrine cell types, which occurred mainly in the mantles of the islets. Of these, glucagon cells were the most numerous, followed by somatostatin and pancreatic polypeptide (PP) cells. The latter were observed in the mantles of the islets and scattered in the exocrine tissue of the duodenal lobe. The marked variation in the shape and the distribution of the endocrine cells in the mantles of the islets seen in the pancreas of the seal, seems to be typical of carnivorous species like the cat and dog.
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PMID:The endocrine pancreas of the Cape fur seal, Arctocephalus pusillus (Schreber, 1776): an immunocytochemical study. 946 81

Prohormone convertase (PC) 1/3 and PC2 are neuroendocrine-specific enzymes that convert prohormones to active hormones. To learn more about the role of these PCs in normal and neoplastic islet cells, we analyzed a series of pancreatic endocrine tumors to determine the role of PC1/3 and PC2 in islet cell hormone processing. In situ hybridization with insulin and glucagon probes and immunostaining with antibodies to PC1/3 and PC2 were done with 6 normal pancreases, 33 insulinomas, and 7 glucagonomas. The intensity of the reactions was graded from 0 to 3+. Normal islets stained strongly for both proinsulin and proglucagon mRNAs. Insulinomas and glucagonomas had readily detected hormone mRNAs for proinsulin and proglucagon, respectively. Normal pancreatic insulin cells stained weakly for PC1/3 (1+) and PC2 (1-2+), and glucagon cells stained weakly for PC1/3 (1-2+) and strongly for PC2 (2-3+). Both insulinomas and glucagonomas stained strongly for PC2 (2-3+) with less intense staining for PC1 (1-2+). These results indicate that PC2 is more highly expressed in insulin- and glucagon-producing pancreatic islet cell tumors and that there is increased expression of PC2 in insulinomas compared to normal insulin-producing cells.
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PMID:Insulin and Glucagon mRNA Expression and Prohormone Convertase Immunoreactivity in Normal and Neoplastic Pancreatic Endocrine Tissue. 1211 24

Glucagon-like peptide-1 (GLP-1) is a potent stimulator of glucose-dependent insulin secretion. Exendin-4(1-39) (Ex-4), isolated from Gila monster venom, is a highly specific GLP-1 receptor agonist that exhibits a prolonged duration of action in vivo. Although the processing mechanisms underlying liberation of GLP-1 from its prohormone have been elucidated, those for Ex-4 remain unknown. To examine the requirements for proEx-4 processing in mammalian cells, BHK fibroblasts, InR1-G9 islet A cells, and AtT-20 corticotropes, which express different prohormone convertases (furin, prohormone convertase 2, and prohormone convertase 1, respectively) were transfected with full-length lizard proEx-4, and the processing of proexendin was examined by HPLC and RIA (n = 3). All of the transfected cell lines exhibited Ex-4-like immunoreactivity in the media, and Ex-4-like immunoreactivity was detected in extracts of InR1-G9 and AtT-20 cells. However, only media and extracts from AtT-20 cells (not InR1-G9 and BHK cells) contained a single peak by HPLC corresponding to synthetic Ex-4. To establish whether proEx-4 can be processed to Ex-4 in nonimmortalized mammalian cells in vivo, the molecular forms of exendin-4 were examined in mice expressing a metallothionein-proEx-4 transgene (n = 3-6 for both males and females). ProEx4 mRNA transcripts were detected by RT-PCR in a broad range of both endocrine and nonendocrine tissues. Ex-4-like immunoreactivity was detected in pituitary, fat, adrenals, and testes; however HPLC analyses demonstrated that processed Ex-4 was found only in adrenals and testes. These results indicate that lizard proEx-4 is processed to mature bioactive Ex-4 in both rodent endocrine and nonendocrine mammalian cell types in vitro and in murine tissues in vivo. These findings may be useful for engineering cells that express a lizard pro-Ex4 transgene for the treatment of type 2 diabetes.
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PMID:Cellular specificity of proexendin-4 processing in mammalian cells in vitro and in vivo. 1219 59

Glucagon-like peptide-1 (GLP-1) is a potent insulinotrophic hormone, which makes GLP-1 an attractive candidate for the treatment of type 2 diabetes. However, the short plasma half-life of the active forms of GLP-1 poses an obstacle to the sustained delivery of this peptide. In this study, we evaluated the effect of GLP-1 gene delivery both in vitro and in vivo using a new plasmid constructed with a modified GLP-1 (7-37) cDNA. This cDNA contains a furin cleavage site between the start codon and the GLP-1 coding region. The expression of the GLP-1 gene was driven by a chicken beta-actin promoter (pbetaGLP1). The level of the GLP-1 mRNA was evaluated by RT-PCR 24 h after transfection. The in vitro results showed a dose-dependent expression of GLP-1. Coculture assay of the GLP-1 plasmid-transfected cells with isolated rat islet cells demonstrated that GLP-1 increased insulin secretion by twofold, compared to controls during a hyperglycemic challenge. A single injection of polyethyleneimine/pbetaGLP1 complex into ZDF rats resulted in increasing insulin secretion and decreasing blood glucose level that was maintained for 2 weeks. This GLP-1 gene delivery system may provide an effective and safe treatment modality for type 2 diabetes.
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PMID:GLP-1 gene delivery for the treatment of type 2 diabetes. 1272 10

We have investigated the proteolytic mechanisms of glucagon degradation within hepatic endosomes at neutral pH before lumen acidification. Hepatic endosomes incubated at neutral pH rapidly degraded native glucagon into 13 intermediate products, one of which corresponded to the bioactive fragment glucagon-(19-29) (miniglucagon). The serine protease inhibitor phenylmethylsulfonyl fluoride as well as the nonspecific protease inhibitor bacitracin inhibited the endosomal degradation of glucagon at pH 7. In purified endosomal fractions, miniglucagon endopeptidase was undetectable as evaluated by immunoblotting, and immunoprecipitation with antibodies to insulin-degrading enzyme, cathepsins B and D, or furin failed to remove the endosomal neutral glucagonase activity. Incubation of endosomal fractions and [125I]iodoglucagon with the zero-length bifunctional cross-linker 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide resulted in specific labeling of a 170-kDa polypeptide. The labeling was completely inhibited by unlabeled glucagon (IC50 value, 5 x 10-7 m) and bacitracin (IC50 value, 1 microg/ml), suggesting that it may correspond to a bacitracin-sensitive glucagon-degrading enzyme. Treatment of the 125I-labeled 170-kDa cross-linked polypeptide with N-glycanase demonstrated that the cross-linked complex contained approximately 30 kDa of N-linked oligosaccharides. Specific cross-linking of the 170-kDa polypeptide was also observed using [125I]Tyr12-miniglucagon as the radioligand. Together, these data suggest that the 170-kDa glycoprotein represents a novel glucagon-degrading activity that could mediate glucagon proteolysis within endosomes before the acidification step and generate the bioactive (19-29) miniglucagon peptide.
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PMID:Endosomal proteolysis of glucagon at neutral pH generates the bioactive degradation product miniglucagon-(19-29). 1295 81

To define the biological significance of the initial cleavage at the proglucagon (PG) interdomain site, K70-R71 downward arrow, we created two interdomain mutants, K70Q-R71Q and R71A. Cotransfection studies in GH4C1 cells show significant amounts of glucagon production by PC2 along with some glicentin, glicentin-related polypeptide-glucagon (GRPP-glucagon) and oxyntomodulin from wild-type PG. In contrast, a larger peptide, PG 33-158, and low amounts of GRPP-glucagon are predominantly generated from interdomain mutants. HPLC analysis shows a 5-fold increase in glucagon production by PC2 from wild-type PG and a corresponding 4-fold lower accumulation and secretion of unprocessed precursor relative to interdomain mutants. PC2 generates significant levels of glucagon from a glicentin (PG 1-69) expression plasmid, whereas PC1/3 produces only modest amounts of oxyntomodulin. Employing a major PG fragment (PG 72-158) expression plasmid, we show that PC1/3 predominantly generates glucagon-like peptide (GLP)-1, whereas PC2 produces only N-terminally extended GLP-1. Surprisingly, production of GLP-1 and GLP-2 by PC1/3 from interdomain mutants, compared with wild-type PG, is not significantly impaired. In addition to PC2 and PC1/3, PC5/6A and furin are also able to cleave the sites, K70-R71 downward arrow and R107-X-R-R110 downward arrow in PG. We show a much greater ability of furin to cleave the monobasic site, R77 downward arrow, than at the dibasic site, R124-R125 downward arrow, which is also weakly processed by PC5/6A, indicating overlapping specificities of these two convertases mainly with PC1/3. We propose here a trimer-like model of the spatial organization of the hormonal sequences within the PG molecule in which the accessibility to prohormone convertase action of most cleavage sites is restricted with the exception of the interdomain site, K70-R71, which is maximally accessible.
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PMID:Significance of prohormone convertase 2, PC2, mediated initial cleavage at the proglucagon interdomain site, Lys70-Arg71, to generate glucagon. 1552 3

Prohormone convertases (PCs) are proteinases that cleave inactive prohormones to biologically active peptides. Seven PCs have been identified; two of them, PC1/3 and PC2, have only been localized in neuroendocrine (NE) tissues; a third, furin, in both endocrine and exocrine tissues. We have studied the immunoreactivity of PC1/3, PC2 and furin in the four major NE cell types of the human pancreas by using double immunofluorescence techniques. The study also included the expression of NE secretory protein 7B2 (secretogranin V), a member of the granin family, which influences the function of PC2. The results showed that the three PCs and 7B2 were expressed only in endocrine pancreas, furin also in exocrine cells. Insulin (B) cells harboured PC1/3 and PC2, but not furin. Glucagon (A) cells were immunoreactive to all three PCs; all glucagon cells expressed PC2, but one subpopulation showed PC1/3 immunoreactivity and another furin. Only a few somatostatin (D) cells contained PC2, but no other proconvertase. Pancreatic polypeptide (PP) cells were non-reactive to all three PCs. 7B2 occurred only in insulin and glucagon cells. A varying co-localization pattern was observed between PCs and between PCs and 7B2, with the exception of PC1/3 and furin which were not co-localized. In conclusion, our study shows that PCs are localized in insulin and glucagon cells and do seem to be important in these cell types for processing of hormone and other protein precursors, especially chromogranins, but for the two other major cell types probably other enzymes are of importance.
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PMID:Prohormone convertases 1/3, 2, furin and protein 7B2 (Secretogranin V) in endocrine cells of the human pancreas. 1795 63

The proprotein convertases are believed to be responsible for the proteolytic maturation of a large number of peptide hormone precursors. Although potent furin inhibitors have been identified, thus far, no small-molecule prohormone convertase 1/3 or prohormone convertase 2 (PC2) inhibitors have been described. After screening 38 small-molecule positional scanning libraries against recombinant mouse PC2, two promising chemical scaffolds were identified: bicyclic guanidines, and pyrrolidine bis-piperazines. A set of individual compounds was designed from each library and tested against PC2. Pyrrolidine bis-piperazines were irreversible, time-dependent inhibitors of PC2, exhibiting noncompetitive inhibition kinetics; the most potent inhibitor exhibited a K(i) value for PC2 of 0.54 microM. In contrast, the most potent bicyclic guanidine inhibitor exhibited a K(i) value of 3.3 microM. Cross-reactivity with other convertases was limited: pyrrolidine bis-piperazines exhibited K(i) values greater than 25 microM for PC1/3 or furin, whereas the K(i) values of bicyclic guanidines for these other convertases were more than 15 microM. We conclude that pyrrolidine bis-piperazines and bicyclic guanidines represent promising initial leads for the optimization of therapeutically active PC2 inhibitors. PC2-specific inhibitors may be useful in the pharmacological blockade of PC2-dependent cleavage events, such as glucagon production in the pancreas and ectopic peptide production in small-cell carcinoma, and to study PC2-dependent proteolytic events, such as opioid peptide production.
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PMID:Synthetic small-molecule prohormone convertase 2 inhibitors. 1907 44

Due to the limited supply of donor pancreas, it is imperative that we identify alternative cell sources that can be used to treat diabetes mellitus (DM). Multipotent adipose tissue-derived stem cells (ADSC) can be abundantly and safely isolated for autologous transplantation and therefore are an ideal candidate. Here, we report the derivation of insulin-producing cells from human or rat ADSC by transduction with the pancreatic duodenal homeobox 1 (Pdx1) gene. RT-PCR analyses showed that native ADSC expressed insulin, glucagon, and NeuroD genes that were up-regulated following Pdx1 transduction. ELISA analyses showed that the transduced cells secreted increasing amount of insulin in response to increasing concentration of glucose. Transplantation of these cells under the renal capsule of streptozotocin-induced diabetic rats resulted in lowered blood glucose, higher glucose tolerance, smoother fur, and less cataract. Histological examination showed that the transplanted cells formed tissue-like structures and expressed insulin. Thus, ADSC-expressing Pdx1 appear to be suitable for treatment of DM.
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PMID:Treatment of type 1 diabetes with adipose tissue-derived stem cells expressing pancreatic duodenal homeobox 1. 1924 9


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