Serum response factor expression is enriched in pancreatic β cells and regulates insulin gene expression

2011 ◽  
Vol 25 (8) ◽  
pp. 2592-2603 ◽  
Author(s):  
Aloke Sarkar ◽  
Mao Zhang ◽  
Shi‐He Liu ◽  
Swapna Sarkar ◽  
F. Charles Brunicardi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Serum Response Factor ◽  
Insulin Gene ◽  
Response Factor ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Factor Expression ◽  
Insulin Gene Expression ◽  
Serum Response

scholarly journals MafA Stability in Pancreatic β Cells Is Regulated by Glucose and Is Dependent on Its Constitutive Phosphorylation at Multiple Sites by Glycogen Synthase Kinase 3

2007 ◽  
Vol 27 (19) ◽  
pp. 6593-6605 ◽  
Author(s):  
Song-iee Han ◽  
Shinsaku Aramata ◽  
Kunio Yasuda ◽  
Kohsuke Kataoka
Keyword(s):  
Gene Expression ◽  
Glycogen Synthase ◽  
Glucose Sensing ◽  
Insulin Gene ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Amino Terminal ◽  
Insulin Gene Expression

ABSTRACT Regulation of insulin gene expression by glucose in pancreatic β cells is largely dependent on a cis-regulatory element, termed RIPE3b/C1, in the insulin gene promoter. MafA, a member of the Maf family of basic leucine zipper (bZip) proteins, is a β-cell-specific transcriptional activator that binds to the C1 element. Based on increased C1-binding activity, MafA protein levels appear to be up-regulated in response to glucose, but the underlying molecular mechanism for this is not well understood. In this study, we show evidence supporting that the amino-terminal region of MafA is phosphorylated at multiple sites by glycogen synthase kinase 3 (GSK3) in β cells. Mutational analysis of MafA and pharmacological inhibition of GSK3 in MIN6 β cells strongly suggest that the rate of MafA protein degradation is regulated by glucose, that MafA is constitutively phosphorylated by GSK3, and that phosphorylation is a prerequisite for rapid degradation of MafA under low-glucose conditions. Our data suggest a new glucose-sensing signaling pathway in islet β cells that regulates insulin gene expression through the regulation of MafA protein stability.

scholarly journals Hedgehog Signaling Regulation of Homeodomain Protein Islet Duodenum Homeobox-1 Expression in Pancreatic β-Cells*

Endocrinology ◽  
2001 ◽  
Vol 142 (3) ◽  
pp. 1033-1040 ◽  
Author(s):  
Melissa K. Thomas ◽  
Jee H. Lee ◽  
Naina Rastalsky ◽  
Joel F. Habener
Keyword(s):  
Gene Expression ◽  
Transcriptional Activation ◽  
Gene Promoter ◽  
Insulin Gene ◽  
Reporter Construct ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Insulin Promoter ◽  
Insulin Gene Expression ◽  
Hh Signaling

Abstract Insulin gene expression in pancreatic β-cells is regulated by signals from developmental morphogen proteins known as hedgehogs (Hhs). By analyzing 5′-deletion insulin promoter-reporter constructs in transient transfections of clonal INS-1 β-cells, we located activating Hh-responsive regions within the rat insulin I promoter that include the glucose-response elements Far (E2) and Flat (A2/A3). Activation of Hh signaling in INS-1 cells by ectopic Hh expression increased (and inhibition of Hh signaling with the Hh-specific inhibitor cyclopamine decreased) transcriptional activation of a multimerized FarFlat enhancer-reporter construct. In DNA-binding studies, nuclear extracts from INS-1 cells activated by ectopic Hh expression increased (and extracts from INS-1 cells treated with cyclopamine decreased) protein binding to a radiolabeled FarFlat oligonucleotide probe. An antiserum directed against the transcription factor islet duodenum homeobox-1 (IDX-1), a regulator of pancreas development and activator of the insulin gene promoter, attenuated the binding activity of Hh-responsive protein complexes. Nuclear IDX-1 protein levels on Western blots were increased by ectopic Hh expression, thereby providing a mechanism for Hh-mediated regulation of the insulin promoter. Addition of cyclopamine to INS-1 cells decreased IDX-1 messenger RNA expression. In transient transfections of a− 4.5-kb mouse IDX-1 promoter-reporter construct, ectopic Hh expression increased (and cyclopamine administration decreased) transcriptional activation of the IDX-1 promoter in a dose-dependent manner. Thus, the IDX-1 gene is a direct regulatory target of Hh signaling in insulin-producing pancreatic β-cells. We propose that Hh signaling activates the insulin gene promoter indirectly via the direct activation of IDX-1 expression. Because IDX-1 gene expression is essential for insulin gene expression, pancreatic β-cell development, and normal glucose homeostasis, our findings that Hh signaling regulates IDX-1 expression in the endocrine pancreas suggest possible novel therapeutic approaches for diabetes mellitus.

Blockage of ceramide metabolism exacerbates palmitate inhibition of pro-insulin gene expression in pancreatic β-cells

2010 ◽  
Vol 338 (1-2) ◽  
pp. 283-290 ◽  
Author(s):  
Jun Guo ◽  
YingYing Qian ◽  
XiaoXue Xi ◽  
XiaoHan Hu ◽  
JianXi Zhu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Insulin Gene ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Insulin Gene Expression

scholarly journals PRMT4 is involved in insulin secretion via the methylation of histone H3 in pancreatic β cells

2015 ◽  
Vol 54 (3) ◽  
pp. 315-324 ◽  
Author(s):  
Joong Kwan Kim ◽  
Yongchul Lim ◽  
Jung Ok Lee ◽  
Young-Sun Lee ◽  
Nam Hee Won ◽  
...  
Keyword(s):  
Gene Expression ◽  
Insulin Secretion ◽  
High Glucose ◽  
Histone H3 ◽  
Insulin Gene ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Protein Arginine Methyltransferases ◽  
Insulin Synthesis ◽  
Insulin Gene Expression

The relationship between protein arginine methyltransferases (PRMTs) and insulin synthesis in β cells is not yet well understood. In the present study, we showed that PRMT4 expression was increased in INS-1 and HIT-T15 pancreatic β cells under high-glucose conditions. In addition, asymmetric dimethylation of Arg17 in histone H3 was significantly increased in both cell lines in the presence of glucose. The inhibition or knockdown of PRMT4 suppressed glucose-induced insulin gene expression in INS-1 cells by 81.6 and 79% respectively. Additionally, the overexpression of mutant PRMT4 also significantly repressed insulin gene expression. Consistently, insulin secretion induced in response to high levels of glucose was decreased by both PRMT4 inhibition and knockdown. Moreover, the inhibition of PRMT4 blocked high-glucose-induced insulin gene expression and insulin secretion in primary pancreatic islets. These results indicate that PRMT4 might be a key regulator of high-glucose-induced insulin secretion from pancreatic β cells via H3R17 methylation.

scholarly journals Comparison of enteroendocrine cells and pancreatic β-cells using gene expression profiling and insulin gene methylation

PLoS ONE ◽  
2018 ◽  
Vol 13 (10) ◽  
pp. e0206401 ◽  
Author(s):  
Gyeong Ryul Ryu ◽  
Esder Lee ◽  
Jong Jin Kim ◽  
Sung-Dae Moon ◽  
Seung-Hyun Ko ◽  
...  
Keyword(s):  
Gene Expression ◽  
Gene Expression Profiling ◽  
Expression Profiling ◽  
Enteroendocrine Cells ◽  
Insulin Gene ◽  
Gene Methylation ◽  
Β Cells ◽  
Pancreatic Β Cells

scholarly journals Regulation of Insulin Gene Transcription by the Immediate-Early Growth Response Gene Egr-1

Endocrinology ◽  
2006 ◽  
Vol 147 (6) ◽  
pp. 2923-2935 ◽  
Author(s):  
Kazuhiro Eto ◽  
Varinderpal Kaur ◽  
Melissa K. Thomas
Keyword(s):  
Transcriptional Activation ◽  
Growth Response ◽  
Insulin Gene ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Expression Levels ◽  
Promoter Sequences ◽  
Early Growth Response ◽  
Insulin Promoter ◽  
Insulin Gene Expression

Abstract Changes in extracellular glucose levels regulate the expression of the immediate-early response gene and zinc finger transcription factor early growth response-1 (Egr-1) in insulin-producing pancreatic β-cells, but key target genes of Egr-1 in the endocrine pancreas have not been identified. We found that overexpression of Egr-1 in clonal (INS-1) β-cells increased transcriptional activation of the rat insulin I promoter. In contrast, reductions in Egr-1 expression levels or function with the introduction of either small interfering RNA targeted to Egr-1 (siEgr-1) or a dominant-negative form of Egr-1 decreased insulin promoter activation, and siEgr-1 suppressed insulin gene expression. Egr-1 did not directly interact with insulin promoter sequences, and mutagenesis of a potential G box recognition sequence for Egr-1 did not impair the Egr-1 responsiveness of the insulin promoter, suggesting that regulation of insulin gene expression by Egr-1 is probably mediated through additional transcription factors. Overexpression of Egr-1 increased, and reduction of Egr-1 expression decreased, transcriptional activation of the glucose-responsive FarFlat minienhancer within the rat insulin I promoter despite the absence of demonstrable Egr-1-binding activity to FarFlat sequences. Notably, augmenting Egr-1 expression levels in insulin-producing cells increased the mRNA and protein expression levels of pancreas duodenum homeobox-1 (PDX-1), a major transcriptional regulator of glucose-responsive activation of the insulin gene. Increasing Egr-1 expression levels enhanced PDX-1 binding to insulin promoter sequences, whereas mutagenesis of PDX-1-binding sites reduced the capacity of Egr-1 to activate the insulin promoter. We propose that changes in Egr-1 expression levels in response to extracellular signals, including glucose, can regulate PDX-1 expression and insulin production in pancreatic β-cells.

scholarly journals New Role for Serum Response Factor in Postnatal Skeletal Muscle Growth and Regeneration via the Interleukin 4 and Insulin-Like Growth Factor 1 Pathways

2006 ◽  
Vol 26 (17) ◽  
pp. 6664-6674 ◽  
Author(s):  
Claude Charvet ◽  
Christophe Houbron ◽  
Ara Parlakian ◽  
Julien Giordani ◽  
Charlotte Lahoute ◽  
...  
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Growth Factor ◽  
Serum Response Factor ◽  
Muscle Growth ◽  
Interleukin 4 ◽  
Specific Gene ◽  
Response Factor ◽  
Insulin Like Growth Factor ◽  
Serum Response

ABSTRACT Serum response factor (SRF) is a crucial transcriptional factor for muscle-specific gene expression. We investigated SRF function in adult skeletal muscles, using mice with a postmitotic myofiber-targeted disruption of the SRF gene. Mutant mice displayed severe skeletal muscle mass reductions due to a postnatal muscle growth defect resulting in highly hypotrophic adult myofibers. SRF-depleted myofibers also failed to regenerate following injury. Muscles lacking SRF had very low levels of muscle creatine kinase and skeletal alpha-actin (SKA) transcripts and displayed other alterations to the gene expression program, indicating an overall immaturity of mutant muscles. This loss of SKA expression, together with a decrease in beta-tropomyosin expression, contributed to myofiber growth defects, as suggested by the extensive sarcomere disorganization found in mutant muscles. However, we observed a downregulation of interleukin 4 (IL-4) and insulin-like growth factor 1 (IGF-1) expression in mutant myofibers which could also account for their defective growth and regeneration. Indeed, our demonstration of SRF binding to interleukin 4 and IGF-1 promoters in vivo suggests a new crucial role for SRF in pathways involved in muscle growth and regeneration.

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