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 expression of the genes encoding the hormones glucagon, insulin, somatostatin, and pancreatic polypeptide in the endocrine islets of the pancreas is regulated in a cell-specific manner, defining four distinct cellular phenotypes (A-, B-, D-, and F-cells, respectively). Binding of nuclear proteins to cognate DNA sequences within cis-acting regulatory elements mediates the transcriptional events that result in the cell-specific activation or repression of gene expression. In a parallel study, we describe the functional properties of the SMS-UE, a pancreatic islet D-cell specific enhancer element that regulates the expression of the somatostatin gene and contains two interdependent domains, A and B. In the studies described herein, we have characterized the nuclear proteins that recognize the SMS-UE. Domain A of the SMS-UE is a DNA enhancer sequence that is identical to that bound by the ubiquitously distributed CCAAT box-binding protein alpha-CBF, a transcription factor that regulates the expression of the human chorionic gonadotrophin alpha-subunit gene. The B-domain, on the other hand, binds an islet cell-specific protein with characteristics similar to those of Isl-1, a transcriptional activator protein that binds to the E2 enhancer of the rat insulin-1 gene. In addition, the SMS-UE binds transcription factor CREB but not CREM, the close homolog of CREB, on a site adjacent to, or overlapping, the 3' end of domain B. We show that the carboxyl-terminal bZIP domain of CREB binds to the cAMP response element of the somatostatin gene but is not sufficient for binding to the SMS-UE, and we present evidence suggesting that CREB.SMS-UE binding requires stabilization by a region of the protein located within the transactivation domain.
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PMID:Somatostatin gene upstream enhancer element activated by a protein complex consisting of CREB, Isl-1-like, and alpha-CBF-like transcription factors. 135 92

Hepatocytes isolated from adult fasted rats and cultured in the presence of thyroid hormones, glucocorticoids, and in a serum-free medium conserve the essentials of their differentiated function and hormonal sensitivity for at least 1 week. In these cells, the gene for L-type pyruvate kinase is expressed only when glucose and insulin are present together, each of them being inactive by itself. Inhibition of the expression of the L-type pyruvate kinase gene which occurs when glucose and/or insulin are removed from the culture medium is not associated with accumulation of the phosphoenolpyruvate carboxykinase mRNA, which argues against the involvement of intracellular cyclic AMP in this phenomenon. Rather, a transcriptional activator, derived from carbohydrate metabolism and accumulating in the presence of insulin, seems to be needed to support the expression of the L-type pyruvate kinase gene. Glucagon, in vitro as in vivo, inhibits production of the L-type pyruvate kinase mRNAs. In addition to their roles on the production of these mRNAs, glucose and insulin on the one hand and glucagon on the other have profound effects on the stability of the L-type pyruvate kinase messengers: the half-life of the mRNA whose production has been blocked by actinomycin D is 1 h in the presence of glucagon and 24 h in the presence of glucose and insulin. Glucagon and glucose/insulin partially antagonize each other's effect on mRNA stability.
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PMID:Regulation of the expression of the L-type pyruvate kinase gene in adult rat hepatocytes in primary culture. 254 75

The paired-homeodomain transcription factor PAX4 is expressed in the developing pancreas and along with PAX6 is required for normal development of the endocrine cells. In the absence of PAX4, the numbers of insulin-producing beta cells and somatostatin-producing delta cells are drastically reduced, while the numbers of glucagon-producing alpha cells are increased. To gain insight into PAX4 function, we cloned a full-length Pax4 cDNA from a beta-cell cDNA library and identified a bipartite consensus DNA binding sequence consisting of a homeodomain binding site separated from a paired domain binding site by 15 nucleotides. The paired half of this consensus sequence has similarities to the PAX6 paired domain consensus binding site, and the two proteins bind to common sequences in several islet genes, although with different relative affinities. When expressed in an alpha-cell line, PAX4 represses transcription through the glucagon or insulin promoters or through an isolated PAX4 binding site. This repression is not simply due to competition with the PAX6 transcriptional activator for the same binding site, since PAX4 fused to the unrelated yeast GAL4 DNA binding domain also represses transcription through the GAL4 binding site in the alpha-cell line and to a lesser degree in beta-cell lines and NIH 3T3 cells. Repressor activity maps to more than one domain within the molecule, although the homeodomain and carboxyl terminus give the strongest repression. PAX4 transcriptional regulation apparently plays a role only early in islet development, since Pax4 mRNA as determined by reverse transcriptase PCR peaks at embryonic day 13.5 in the fetal mouse pancreas and is undetectable in adult islets. In summary, PAX4 can function as a transcriptional repressor and is expressed early in pancreatic development, which may allow it to suppress alpha-cell differentiation and permit beta-cell differentiation.
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PMID:Paired-homeodomain transcription factor PAX4 acts as a transcriptional repressor in early pancreatic development. 1056 52

The paired box and homeodomain containing transcription factors Pax4 and Pax6 are known to be essential for development of the pancreatic endocrine cells. In this report we demonstrate that stable expression of Pax4 in a rat glucagon-producing cell line inhibits the endogenously expressed glucagon gene completely. Furthermore, Pax4 represses Pax6 independent transcription of the insulin promoter, suggesting that Pax4 can actively repress transcription in addition to acting by competition with the transcriptional activator Pax6.
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PMID:Pax4 represses pancreatic glucagon gene expression. 1089

The LIM homeodomain protein Islet-1 (Isl1), one of the earliest markers for motor neuron differentiation, is also expressed in all classes of islet cells in the pancreas. Isl1 is known to bind and regulate the promoters of the insulin, glucagon and somatostatin genes. In this study, we describe isolation of a novel isl1 cDNA species from the mouse islet beta cell line betaTC6, which arose from the utilization of an alternative splicing acceptor site in the fifth exon. This shorter cDNA encodes an Isl1 isoform (Isl1-beta) lacking the carboxy-terminal 23 amino acids of the previously reported product Isl1-alpha. Although the level of isl1-beta mRNA is much lower than that of isl1-alpha, isl1-beta is preferentially expressed in murine insulinoma cell lines but not in glucagonoma cell line. Upon transient transfection, both Isl1-alpha and Isl1-beta accumulate in the nuclei of murine insulinoma cells. We found that Isl1-beta is a relatively more potent transcriptional activator of the insulin promoter than Isl1-alpha and that the Isl1-alpha isoform undergoes phosphorylation. Therefore, the transcriptional activity of Isl1 is potentially regulated by the alternative splicing of its mRNA and by phosphorylation.
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PMID:Isolation and characterization of an alternatively spliced variant of transcription factor Islet-1. 1466 3

During fasting periods, hepatic glucose production is enhanced by glucagon to provide fuels for other organs. This process is mediated via cAMP-dependent induction of the CREB regulated transcriptional coactivator (CRTC) 2, a critical transcriptional activator for hepatic gluconeogenesis. We have previously shown that CRTC2 activity is regulated by AMP activated protein kinase (AMPK) family members. Here we show that adiponectin and thiazolidinedione directly regulate AMPK to modulate CRTC2 activity in hepatocytes. Adiponectin or thiazolidinedione lowered glucose production from primary hepatocytes. Treatment of both reagents reduced gluconeogenic gene expression as well as cAMP-mediated induction of CRE reporter, suggesting that these reagents directly affect CREB/CRTC2- dependent transcription. Furthermore, adiponectin or thiazolidinedione mediated repression of CRE activity is largely blunted by co-expression of phosphorylation defective mutant CRTC2, underscoring the importance of serine 171 residue of this factor. Taken together, we propose that adiponectin and thiazolidinedione promote the modulation of AMPK-dependent CRTC2 activity to influence hepatic gluconeogenesis.
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PMID:Adiponectin and thiazolidinedione targets CRTC2 to regulate hepatic gluconeogenesis. 1938 Oct 67

Liver plays a major role in maintaining glucose homeostasis in mammals. Under fasting conditions, hepatic glucose production is critical as a source of fuel to maintain the basic functions in other tissues, including skeletal muscle, red blood cells, and the brain. Fasting hormones glucagon and cortisol play major roles during the process, in part by activating the transcription of key enzyme genes in the gluconeogenesis such as phosphoenol pyruvate carboxykinase (PEPCK) and glucose 6 phosphatase catalytic subunit (G6Pase). Conversely, gluconeogenic transcription is repressed by pancreatic insulin under feeding conditions, which effectively inhibits transcriptional activator complexes by either promoting post-translational modifications or activating transcriptional inhibitors in the liver, resulting in the reduction of hepatic glucose output. The transcriptional regulatory machineries have been highlighted as targets for type 2 diabetes drugs to control glycemia, so understanding of the complex regulatory mechanisms for transcription circuits for hepatic gluconeogenesis is critical in the potential development of therapeutic tools for the treatment of this disease. In this review, the current understanding regarding the roles of two key transcriptional activators, CREB and FoxO1, in the regulation of hepatic gluconeogenic program is discussed.
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PMID:CREB and FoxO1: two transcription factors for the regulation of hepatic gluconeogenesis. 2423 63