1
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Lee TY, Cho IS, Bashyal N, Naya FJ, Tsai MJ, Yoon JS, Choi JM, Park CH, Kim SS, Suh-Kim H. ERK Regulates NeuroD1-mediated Neurite Outgrowth via Proteasomal Degradation. Exp Neurobiol 2020; 29:189-206. [PMID: 32606250 PMCID: PMC7344372 DOI: 10.5607/en20021] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 06/16/2020] [Accepted: 06/16/2020] [Indexed: 12/22/2022] Open
Abstract
Neurogenic differentiation 1 (NeuroD1) is a class B basic helix-loop-helix (bHLH) transcription factor and regulates differentiation and survival of neuronal and endocrine cells by means of several protein kinases, including extracellular signal-regulated kinase (ERK). However, the effect of phosphorylation on the functions of NeuroD1 by ERK has sparked controversy based on context-dependent differences across diverse species and cell types. Here, we evidenced that ERK-dependent phosphorylation controlled the stability of NeuroD1 and consequently, regulated proneural activity in neuronal cells. A null mutation at the ERK-dependent phosphorylation site, S274A, increased the half-life of NeuroD1 by blocking its ubiquitin-dependent proteasomal degradation. The S274A mutation did not interfere with either the nuclear translocation of NeuroD1 or its heterodimerization with E47, its ubiquitous partner and class A bHLH transcription factor. However, the S274A mutant increased transactivation of the E-box-mediated gene and neurite outgrowth in F11 neuroblastoma cells, compared to the wild-type NeuroD1. Transcriptome and Gene Ontology enrichment analyses indicated that genes involved in axonogenesis and dendrite development were downregulated in NeuroD1 knockout (KO) mice. Overexpression of the S274A mutant salvaged neurite outgrowth in NeuroD1-deficient mice, whereas neurite outgrowth was minimal with S274D, a phosphomimicking mutant. Our data indicated that a longer protein half-life enhanced the overall activity of NeuroD1 in stimulating downstream genes and neuronal differentiation. We propose that blocking ubiquitin-dependent proteasomal degradation may serve as a strategy to promote neuronal activity by stimulating the expression of neuron-specific genes in differentiating neurons.
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Affiliation(s)
- Tae-Young Lee
- Department of Anatomy, Ajou University School of Medicine, Suwon 16499, Korea.,Department of Biomedical Sciences, Graduate School, Ajou University School of Medicine, Suwon 16499, Korea.,Research Center, CelleBrain Ltd., Jeonju 54871, Korea
| | - In-Su Cho
- Department of Anatomy, Ajou University School of Medicine, Suwon 16499, Korea
| | - Narayan Bashyal
- Department of Anatomy, Ajou University School of Medicine, Suwon 16499, Korea.,Department of Biomedical Sciences, Graduate School, Ajou University School of Medicine, Suwon 16499, Korea
| | - Francisco J Naya
- Department of Biology, Life Science and Engineering Building, Boston University, Boston, MA 00215, USA
| | - Ming-Jer Tsai
- Department of Medicine and Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jeong Seon Yoon
- Department of Anatomy, Ajou University School of Medicine, Suwon 16499, Korea
| | - Jung-Mi Choi
- Department of Anatomy, Ajou University School of Medicine, Suwon 16499, Korea
| | - Chang-Hwan Park
- Graduate School of Biomedical Science and Engineering, Hanyang University, Seoul 04763, Korea
| | - Sung-Soo Kim
- Department of Anatomy, Ajou University School of Medicine, Suwon 16499, Korea.,Department of Biomedical Sciences, Graduate School, Ajou University School of Medicine, Suwon 16499, Korea
| | - Haeyoung Suh-Kim
- Department of Anatomy, Ajou University School of Medicine, Suwon 16499, Korea.,Department of Biomedical Sciences, Graduate School, Ajou University School of Medicine, Suwon 16499, Korea.,Research Center, CelleBrain Ltd., Jeonju 54871, Korea
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2
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Abstract
Production and secretion of insulin from the β-cells of the pancreas is very crucial in maintaining normoglycaemia. This is achieved by tight regulation of insulin synthesis and exocytosis from the β-cells in response to changes in blood glucose levels. The synthesis of insulin is regulated by blood glucose levels at the transcriptional and post-transcriptional levels. Although many transcription factors have been implicated in the regulation of insulin gene transcription, three β-cell-specific transcriptional regulators, Pdx-1 (pancreatic and duodenal homeobox-1), NeuroD1 (neurogenic differentiation 1) and MafA (V-maf musculoaponeurotic fibrosarcoma oncogene homologue A), have been demonstrated to play a crucial role in glucose induction of insulin gene transcription and pancreatic β-cell function. These three transcription factors activate insulin gene expression in a co-ordinated and synergistic manner in response to increasing glucose levels. It has been shown that changes in glucose concentrations modulate the function of these β-cell transcription factors at multiple levels. These include changes in expression levels, subcellular localization, DNA-binding activity, transactivation capability and interaction with other proteins. Furthermore, all three transcription factors are able to induce insulin gene expression when expressed in non-β-cells, including liver and intestinal cells. The present review summarizes the recent findings on how glucose modulates the function of the β-cell transcription factors Pdx-1, NeuroD1 and MafA, and thereby tightly regulates insulin synthesis in accordance with blood glucose levels.
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3
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Cho JH, Kwon IS, Kim S, Ghil SH, Tsai MJ, Kim YS, Lee YD, Suh-Kim H. Overexpression of BETA2/NeuroD induces neurite outgrowth in F11 neuroblastoma cells. J Neurochem 2008. [DOI: 10.1046/j.1471-4159.2001.00230.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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4
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Oda H, Fushimi F, Kato M, Kitagawa M, Araki K, Seki N, Ohkubo H. Microarray analysis of the genes induced by tetracycline-regulated expression of NDRF/NeuroD2 in P19 cells. Biochem Biophys Res Commun 2005; 335:458-68. [PMID: 16083855 DOI: 10.1016/j.bbrc.2005.07.093] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Accepted: 07/15/2005] [Indexed: 11/17/2022]
Abstract
NeuroD-related factor (NDRF)/NeuroD2 is a basic helix-loop-helix (bHLH) protein that plays important roles in neuronal development. To elucidate the NDRF transcription network, we used mouse cDNA microarray analysis combined with a tetracycline-regulatable expression system in P19 embryonal carcinoma cells. Five genes were identified to be up-regulated in the presence of NDRF protein. RNA hybridization analysis confirmed that brain-lipid-binding protein (BLBP) and inhibitor of differentiation 1 (Id1) genes were among the five genes that were rapidly and significantly up-regulated after induction of NDRF. When a dominant negative form of NDRF protein was expressed during retinoic acid-induced neuronal differentiation of P19 cells, the BLBP gene, but not the Id1 gene, was potently repressed. Immunohistochemical analysis revealed that both NDRF and Id1 immunoreactivities were observed in some granule cells of the cerebellum in the postnatal period. These results suggest that NDRF or its related bHLH proteins may act upstream of these genes in a subset of developing neurons.
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Affiliation(s)
- Hisanobu Oda
- Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 862-0976, Japan.
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5
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Harmon JS, Stein R, Robertson RP. Oxidative stress-mediated, post-translational loss of MafA protein as a contributing mechanism to loss of insulin gene expression in glucotoxic beta cells. J Biol Chem 2005; 280:11107-13. [PMID: 15664999 DOI: 10.1074/jbc.m410345200] [Citation(s) in RCA: 168] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Glucose toxicity in pancreatic islet beta cells causes loss of insulin gene expression, content, and secretion due to loss of binding of transcription factors, most notably PDX-1 and RIPE-3b1 activator, to the promoter region of the insulin gene. Recently, RIPE-3b1 activator was cloned and identified as the mammalian homologue of avian MafA/Maf-L (MafA). This enabled us to carry out more extensive studies of the role of MafA in glucotoxicity than were hitherto possible. Northern analysis of glucotoxic HIT-T15 cells revealed normal amounts of MafA mRNA, but Western analysis demonstrated a 97 +/- 1% reduction in MafA protein (p < 0.0001). The proteasome is a likely site for MafA degradation as lactacystin, an irreversible proteasome inhibitor, caused an accumulation of MafA protein. Antioxidants have previously been shown to prevent the adverse effects of glucose toxicity on beta cell function both in vivo and in vitro. In the current study, chronic culturing of HIT-T15 cells with the antioxidant N-acetylcysteine (NAC) prevented loss of MafA protein (late passage = 18.9 +/- 10.4% of early passage, p < 0.001; late passage with NAC = 68.7 +/- 19.7% of early passage, p = not significant) and loss of DNA binding (late passage = 63.7 +/- 9% of early passage, p < 0.02; late passage with NAC = 116 +/- 10% of early passage, p = not significant). Additionally, transient transfection of PDX-1 or MafA cDNA into glucotoxic cells increased PDX-1 and MafA protein levels and individually increased insulin promoter activity (untreated = 34%, PDX-1 = 70%, MafA = 78%; percentage of activity of early passage cells), whereas the combined transfection of MafA and PDX-1 completely restored insulin promoter activity. This recovery of promoter activity following transient transfection had no effect on endogenous insulin mRNA. However, adenoviral infection of MafA and PDX-1 significantly increased endogenous insulin mRNA levels by 93% (121 +/- 9 versus 233 +/- 18 density light units; n = 5, p < 0.001). We conclude that the absence of MafA protein from beta cells via chronic oxidative stress contributes importantly to the loss of endogenous insulin gene expression as glucose toxicity develops.
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Affiliation(s)
- Jamie S Harmon
- Pacific Northwest Research Institute, Seattle, Washington 98122, USA
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6
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Kajihara M, Sone H, Amemiya M, Katoh Y, Isogai M, Shimano H, Yamada N, Takahashi S. Mouse MafA, homologue of zebrafish somite Maf 1, contributes to the specific transcriptional activity through the insulin promoter. Biochem Biophys Res Commun 2004; 312:831-42. [PMID: 14680841 DOI: 10.1016/j.bbrc.2003.10.196] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2003] [Indexed: 10/26/2022]
Abstract
Large Maf transcription factors, which are members of the basic leucine zipper (b-Zip) superfamily, have been reported to be involved in embryonic development and cell differentiation. Previously, we isolated a novel zebrafish large Maf cDNA, somite Maf1 (SMaf1), which possesses transactivational activity within its N-terminus domain. To elucidate SMaf1 function in mammals, we tried to isolate the mouse homologue of zebrafish SMaf1. We isolated the mouse homologue of zebrafish SMaf1, which is the same molecule as the recently reported MafA. MafA mRNA was detected in formed somites, head neural tube, and liver cells in the embryos. In the adult mouse, MafA transcript was amplified in the brain, lung, spleen, and kidney by RT-PCR. MafA mRNA was also detectable in beta-cell line. Next, we analyzed the transcriptional activity of MafA using rat insulin promoters I and II (RIPI and II), since a part of RIP sequence was similar to the Maf recognition element (MARE) and MafA was expressed in pancreatic beta cells. MafA was able to activate transcription from RIPII, but not RIPI, in a dose dependent manner and the activity was dependent on RIPE3b/C1 sequences. In addition, the amount of MafA protein was regulated by glucose concentration. These results indicate that MafA is the homologue of zebrafish SMaf1 and acts as a transcriptional activator of the insulin gene promoter through the RIPE3b element.
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Affiliation(s)
- Miwako Kajihara
- Department of Internal Medicine, University of Tsukuba, 1-1-1, Tennodai, Tsukuba 305-8575, Japan
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7
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Abstract
Type 2 diabetes mellitus is increasing worldwide with a trend of declining age of onset. It is characterized by insulin resistance and a progressive loss of beta-cell function. The ability to secrete adequate amounts of insulin is determined by the functional integrity of beta-cells and their overall mass. Glucose, the main regulator of insulin secretion and production, exerts negative effects on beta-cell function when present in excessive amounts over a prolonged period. The multiple metabolic aberrations induced by chronic hyperglycemia in the beta-cell include increased sensitivity to glucose, increased basal insulin release, reduced response to stimulus to secrete insulin, and a gradual depletion of insulin stores. Inadequate insulin production during chronic hyperglycemia results from decreased insulin gene transcription due to hyperglycemia-induced changes in the activity of beta-cell specific transcription factors. Hyperglycemia may negatively affect beta-cell mass by inducing apoptosis without a compensatory increase in beta-cell proliferation and neogenesis. The detrimental effect of excessive glucose concentrations is referred to as 'glucotoxicity'. The present review discusses the role of glucotoxicity in beta-cell dysfunction in type 2 diabetes mellitus.
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Affiliation(s)
- Nurit Kaiser
- Endocrinology and Metabolism Service, Department of Medicine and The Hadassah Diabetes Center, Hebrew University-Hadassah Medical Center, Jerusalem, Israel.
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8
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Kim JW, Seghers V, Cho JH, Kang Y, Kim S, Ryu Y, Baek K, Aguilar-Bryan L, Lee YD, Bryan J, Suh-Kim H. Transactivation of the mouse sulfonylurea receptor I gene by BETA2/NeuroD. Mol Endocrinol 2002; 16:1097-107. [PMID: 11981044 DOI: 10.1210/mend.16.5.0934] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The sulfonylurea receptor 1 (SUR1) plays a key role in regulation of insulin secretion in pancreatic beta-cells. In this study we investigated the mechanism for tissue-specific expression of the SUR1 gene. A -138/-20 fragment exhibited basal promoter activity while the -660/-20 fragment contained a regulatory element for tissue-specific expression of the mouse SUR1 gene. A pancreatic beta-cell-specific transcription factor, BETA2 (beta-cell E box transcription factor)/NeuroD, enhanced the promoter activity of the -660/-20 fragment in cooperation with E47. Coexpression of a dominant negative mutant of BETA2/NeuroD, BETA2(1-233), repressed the promoter activity of the -660/-20 fragment. BETA2/NeuroD bound specifically to the E3 element located at -141. The E3 sequence in a heterologous context conferred transactivation by BETA2/NeuroD in HeLa and HIT cells. Mutation of E3 eliminated the stimulatory effect of BETA2/NeuroD. Unlike BETA2/NeuroD, neurogenin 3 (ngn3) could not activate the E3 element in HeLa cells. Overexpression of ngn3 concomitantly increased expression of BETA2/NeuroD and SUR1 in HIT cells but not in HeLa cells. These results indicate that BETA2/NeuroD induces tissue-specific expression of the SUR1 gene through the E3 element. These results also suggest that E3 is specific for BETA2/NeuroD, and the stimulatory effect of ngn3 in HIT cells may require factors specifically expressed in HIT cells.
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Affiliation(s)
- Ji-Won Kim
- Department of Anatomy, Ajou University, School of Medicine, Suwon, 442-749, Korea
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9
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Bramblett DE, Copeland NG, Jenkins NA, Tsai MJ. BHLHB4 is a bHLH transcriptional regulator in pancreas and brain that marks the dimesencephalic boundary. Genomics 2002; 79:402-12. [PMID: 11863370 DOI: 10.1006/geno.2002.6708] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have cloned a basic helix-loop-helix (bHLH) factor gene, Bhlhb4, from a mouse beta-cell line. Fluorescence in situ hybridization (FISH) and genetic mapping place Bhlhb4 at the telomeric end of mouse chromosome 2 (H3-H4), syntenic to human chromosome 20q13. Based on phylogenetic analysis, BHLHB4 belongs to a new subgroup of bHLH factors including at least four previously identified mouse bHLH factors: BHLHB5, MIST1, OLIG1, OLIG2, and OLIG3. In the developing nervous system, Bhlhb4 was found to mark the dimesencephalic boundary, suggesting that Bhlhb4 may have a role in diencephalic regionalization. In the pancreas, Bhlhb4 is expressed in a transient fashion that suggests a role in the pancreatic endocrine cell lineage. Transfection experiments show that BHLHB4 can repress transcriptional activation mediated through the pancreatic beta-cell specific insulin promoter enhancer RIPE3. Together, these data suggest that BHLHB4 may modulate the expression of genes required for the differentiation and/or maintenance of pancreatic and neuronal cell types.
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Affiliation(s)
- Debra E Bramblett
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
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10
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Harrington RH, Sharma A. Transcription factors recognizing overlapping C1-A2 binding sites positively regulate insulin gene expression. J Biol Chem 2001; 276:104-13. [PMID: 11024035 DOI: 10.1074/jbc.m008415200] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcription factors binding the insulin enhancer region, RIPE3b, mediate beta-cell type-specific and glucose-responsive expression of the insulin gene. Earlier studies demonstrate that activator present in the beta-cell-specific RIPE3b1-binding complex is critical for these actions. The DNA binding activity of the RIPE3b1 activator is induced in response to glucose stimulation and is inhibited under glucotoxic conditions. The C1 element within the RIPE3b region has been implicated as the binding site for RIPE3b1 activator. The RIPE3b region also contains an additional element, A2, which shares homology with the A elements in the insulin enhancer. Transcription factors (PDX-1 and HNF-1 alpha) binding to A elements are critical regulators of insulin gene expression and/or pancreatic development. Hence, to understand the roles of C1 and A2 elements in regulating insulin gene expression, we have systematically mutated the RIPE3b region and analyzed the effect of these mutations on gene expression. Our results demonstrate that both C1 and A2 elements together constitute the binding site for the RIPE3b1 activator. In addition to C1-A2 (RIPE3b) binding complexes, three binding complexes that specifically recognize A2 elements are found in nuclear extracts from insulinoma cell lines; the A2.2 complex is detected only in insulin-producing cell lines. Furthermore, two base pairs in the A2 element were critical for binding of both RIPE3b1 and A2.2 activators. Transient transfection results indicate that both C1-A2 and A2-specific binding activators cooperatively activate insulin gene expression. In addition, RIPE3b1- and A2-specific activators respond differently to glucose, suggesting that their overlapping binding specificity and functional cooperation may play an important role in regulating insulin gene expression.
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Affiliation(s)
- R H Harrington
- Section of Islet Transplantation & Cell Biology, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts 02215, USA
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11
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Chronic exposure to high glucose impairs multiple β-cell functions in cultured human pancreatic islets. ACTA ACUST UNITED AC 2000. [DOI: 10.1097/00060793-200002000-00007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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12
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Shibata H, Oda H, Mukai H, Oishi K, Misaki K, Ohkubo H, Ono Y. Interaction of PKN with a neuron-specific basic helix-loop-helix transcription factor, NDRF/NeuroD2. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1999; 74:126-34. [PMID: 10640683 DOI: 10.1016/s0169-328x(99)00273-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
By the yeast two-hybrid screening of a human brain cDNA library with the amino-terminal regulatory region of PKN as a bait, a clone encoding a neuron-specific basic Helix-Loop-Helix (bHLH) transcription factor, NDRF/NeuroD2 was isolated. NDRF/NeuroD2 was co-precipitated with PKN from the lysate of COS-7 cells transfected with both expression constructs for NDRF/NeuroD2 and PKN. In vitro binding studies using the deletion mutants of NDRF/NeuroD2 synthesized in a rabbit reticulocyte lysate indicated that the internal region containing the bHLH domain of NDRF/NeuroD2 was necessary and sufficient for the interaction with PKN. In addition, recombinant NDRF/NeuroD2 purified from Escherichia coli could bind PKN, suggesting the direct interaction between NDRF/NeuroD2 and PKN. Transient transfection assays using P19 cells revealed that expression of NDRF/NeuroD2 increased the transactivation of the rat insulin promoter element 3 (RIPE3) enhancer up to approximately 12-fold and that co-expression of catalytically active form of PKN, but not kinase-deficient derivative, resulted in a further threefold increase of NDRF/NeuroD2-mediated transcription. These findings suggest that PKN may contribute to transcriptional responses through the post-translational modification of the NDRF/NeuroD2-dependent transcriptional machinery.
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Affiliation(s)
- H Shibata
- Department of Biology, Faculty of Science, Kobe University, Kobe, Japan
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13
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Bramblett DE, Huang HP, Tsai MJ. Pancreatic islet development. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1999; 47:255-315. [PMID: 10582089 DOI: 10.1016/s1054-3589(08)60114-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- D E Bramblett
- Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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14
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Dumonteil E, Laser B, Constant I, Philippe J. Differential regulation of the glucagon and insulin I gene promoters by the basic helix-loop-helix transcription factors E47 and BETA2. J Biol Chem 1998; 273:19945-54. [PMID: 9685329 DOI: 10.1074/jbc.273.32.19945] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The insulin and glucagon genes are expressed in the beta and alpha cells of the islets of Langerhans, respectively. The factors controlling their cell- and islet-specific expression are poorly known. Insulin-enhancer factor-1 (IEF1) has previously been shown to interact with the E boxes of the rat insulin I and II genes and was proposed to play a critical role in beta cell-specific expression. BETA2, a recently identified basic helix-loop-helix (bHLH) protein, binds with high affinity and transactivates the rat insulin II gene upon dimerization with the ubiquitous bHLH protein E47. We show here that the heterodimer E47/BETA2 also binds and transactivates the rat insulin I and glucagon genes and exhibits the same characteristics as IEF1. In transfection experiments, the E boxes of the insulin I and glucagon genes confer transcriptional activity in both insulin- and glucagon-producing cells, which is increased by overexpression of E47 and BETA2. However, overexpression of E47 inhibits only E box-mediated glucagon gene expression, whereas it activates insulin gene transcription, indicating that the E boxes of the insulin and glucagon genes display gene-specific characteristics. We conclude that the heterodimer E47/BETA2 represents an islet-specific factor that controls both insulin and glucagon gene transcription and that the E47/BETA2 ratio may be important for regulated gene expression.
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Affiliation(s)
- E Dumonteil
- Unité de Diabétologie Clinique, Centre Médical Universitaire, CH-1211 Genève 4, Switzerland
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15
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Sussel L, Kalamaras J, Hartigan-O'Connor DJ, Meneses JJ, Pedersen RA, Rubenstein JL, German MS. Mice lacking the homeodomain transcription factor Nkx2.2 have diabetes due to arrested differentiation of pancreatic beta cells. Development 1998; 125:2213-21. [PMID: 9584121 DOI: 10.1242/dev.125.12.2213] [Citation(s) in RCA: 404] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The endocrine pancreas is organized into clusters of cells called islets of Langerhans comprising four well-defined cell types: alpha beta, delta and PP cells. While recent genetic studies indicate that islet development depends on the function of an integrated network of transcription factors, the specific roles of these factors in early cell-type specification and differentiation remain elusive. Nkx2.2 is a member of the mammalian NK2 homeobox transcription factor family that is expressed in the ventral CNS and the pancreas. Within the pancreas, we demonstrate that Nkx2.2 is expressed in alpha, beta and PP cells, but not in delta cells. In addition, we show that mice homozygous for a null mutation of Nkx2.2 develop severe hyperglycemia and die shortly after birth. Immunohistochemical analysis reveals that the mutant embryos lack insulin-producing beta cells and have fewer glucagon-producing alpha cells and PP cells. Remarkably, in the mutants there remains a large population of islet cells that do not produce any of the four endocrine hormones. These cells express some beta cell markers, such as islet amyloid polypeptide and Pdx1, but lack other definitive beta cell markers including glucose transporter 2 and Nkx6.1. We propose that Nkx2.2 is required for the final differentiation of pancreatic beta cells, and in its absence, beta cells are trapped in an incompletely differentiated state.
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Affiliation(s)
- L Sussel
- Nina Ireland Laboratory of Developmental Neurobiology, Department of Psychiatry, University of California, San Francisco, CA 94143, USA
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16
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Read ML, Masson MR, Docherty K. A RIPE3b1-like factor binds to a novel site in the human insulin promoter in a redox-dependent manner. FEBS Lett 1997; 418:68-72. [PMID: 9414097 DOI: 10.1016/s0014-5793(97)01352-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In the human insulin gene, a regulatory sequence upstream of the transcription start site at -229 to -258 (the E2 element) binds a ubiquitous factor USF. The present study led to the identification of a second factor, D0, that binds to an adjacent upstream site, the C2 element, that has previously not been described. The results demonstrate that D0 exhibits similar properties to RIPE3b1, a factor shown to be an important determinant of insulin gene beta-cell-specific expression. Binding of D0 to the C2 element was abolished by the oxidising agent diamide, and the alkylating agent N-ethylmaleimide. The results indicate that expression of the insulin gene may be regulated by a redox-dependent pathway involving RIPE3b1 or a RIPE3b1-like factor.
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Affiliation(s)
- M L Read
- Department of Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, UK
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17
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Li Q, Notkins AL, Lan MS. Molecular characterization of the promoter region of a neuroendocrine tumor marker, IA-1. Biochem Biophys Res Commun 1997; 236:776-81. [PMID: 9245732 DOI: 10.1006/bbrc.1997.7054] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
IA-1 is an intronless gene, which encodes a 510 amino acid protein with a zinc-finger DNA-binding motif that is expressed in tumors of neuroendocrine origin. The 5'-upstream region of the IA-1 gene was recently sequenced. In this paper, the regulatory elements and the promoter region of the 5'-upstream region were analyzed by use of a series of deletion mutants (ranging from +26 bp to -2090 bp upstream of the IA-1 gene), which were tested in a pituitary tumor cell line, AtT-20, and Hela cells by transient transfection assays. These experiments showed that a 506 base pair upstream sequence was sufficient for maximal expression of a reporter gene. Multiple known regulatory elements were found within this region including three E boxes and a clustered Sp-1 site. In addition, Southwestern blot analysis, using a radiolabeled promoter sequence (extending from -108 bp to -66 bp) and nuclear extracts from both neuroendocrine and non-neuroendocrine cell lines, revealed four promoter binding proteins designated PBP1, PBP2, PBP3 and PBP4 with molecular weights of 55 kD, 32 kD, 29 kD, and 27/28 kD, respectively. These studies suggest that several different regulatory elements in the 5'-upstream region of the IA-1 gene and at least four different nuclear proteins may be involved in the cell-specific expression of IA-1.
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Affiliation(s)
- Q Li
- Oral Infection and Immunity Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892, USA
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18
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Stellrecht CM, DeMayo FJ, Finegold MJ, Tsai MJ. Tissue-specific and developmental regulation of the rat insulin II gene enhancer, RIPE3, in transgenic mice. J Biol Chem 1997; 272:3567-72. [PMID: 9013607 DOI: 10.1074/jbc.272.6.3567] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The rat insulin II gene enhancer, RIPE3 (-126 to -86), mediates beta-islet cell-specific activity in transfection assays. To investigate the in vivo activity of RIPE3, we generated mice carrying a transgene consisting of three copies of RIPE3 linked to a minimal chicken ovalbumin promoter in conjunction with sequences encoding the human growth hormone gene. 13 transgenic mice were obtained, 11 of which expressed the transgene, as determined by serum radioimmunoassay for human growth hormone. Expression of the transgene was assessed for cell specificity by immunocytochemistry. The pancreatic islet cells invariably stained for growth hormone, while the acinar and ductal cells did not. Staining of adjacent sections for insulin, glucagon, and somatostatin revealed that growth hormone was expressed in the beta-cell in all of the mice analyzed, but in some mice alpha-cells also contained growth hormone. RNase protection analysis revealed that the tissues that consistently express the transgene in these animals are the pancreas and brain. Developmental analysis revealed that the transgene was expressed in the pancreatic bud at embryonic day 9.5, corresponding to the temporal expression pattern of the insulin gene. These results signify that an element as small as 41 base pairs is capable of regulating pancreatic temporal and spatial gene expression in vivo.
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Affiliation(s)
- C M Stellrecht
- Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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19
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Goodman PA, Medina-Martinez O, Fernandez-Mejia C. Identification of the human insulin negative regulatory element as a negative glucocorticoid response element. Mol Cell Endocrinol 1996; 120:139-46. [PMID: 8832573 DOI: 10.1016/0303-7207(96)03830-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Insulin gene transcription in adults is restricted to pancreatic beta cells. Studies with both transgenic mice and islet cell lines have demonstrated that beta cell specific expression is conferred by the 5' flanking region of the insulin gene. Transfection analysis has shown that cell specific expression involved an interaction between both positive and negative promoter cis elements. An upstream region (between -258 and -279) of the human insulin promoter served as a site of negative regulation. Transfection analysis in the pancreatic cell line HIT T-15 M 2.2.2 revealed that a DNA fragment containing this region causes a 45% reduction in promoter activity when linked to the native insulin promoter and a 72% reduction when linked to a heterologous tk promoter. Electrophoretic mobility shift analysis of this negative regulatory region (NRE) reveals a complex pattern of binding, wherein two major and several minor complexes are observed. Competition experiments demonstrated that formation of the fastest mobility complex is completely inhibited with excess cold glucocorticoid responsive element (GRE) consensus oligonucleotide. Purified glucocorticoid receptor binding domain (T7X556) demonstrated binding to the NRE oligonucleotide. Functional studies showed that dexamethasone treatment of HIT T-15 M 2.2.2 cells containing an NRE-tk CAT plasmid decreased CAT gene expression by 48%. Analysis of the NRE revealed 73% homology with the negative GRE consensus sequence. These data show that the human insulin NRE is a negative glucocorticoid response element.
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Affiliation(s)
- P A Goodman
- Research Institute, Cedars Sinai Medical Center, Los Angeles, CA, USA
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20
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Odagiri H, Wang J, German MS. Function of the human insulin promoter in primary cultured islet cells. J Biol Chem 1996; 271:1909-15. [PMID: 8567638 DOI: 10.1074/jbc.271.4.1909] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Pancreatic islet beta cells regulate the rate of insulin gene transcription in response to a number of nutrients, the most potent of which is glucose. To test for its regulation by glucose, the promoter sequence was isolated from the human insulin gene. When linked to chloramphenicol acetyltransferase and transfected into primary islet cultures, the human insulin promoter is activated by glucose. In parallel islet transfections, glucose also activates the L-pyruvate kinase and islet amyloid chain ketoacid dehydrogenase E1a promoter, but it does not affect the beta cell glucose kinase promoter. Using deletion and substitution mutations of the proximal human insulin promoter, we mapped a metabolic response element to the E box, E1, at -100 base pairs relative to the transcription start site. Although the isolated E1 element responds to glucose, inclusion of either of two AT-rich sequences, A1 or A2/C1 on either side of E1, results in dramatic synergistic activation. Inclusion of A2/C1 also increases the response to glucose. The A2-E1-A1 region alone, however, does not explain all of the activity of the human insulin promoter in cultured islets, and other transcriptionally important elements likely to contribute to the glucose response as well.
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Affiliation(s)
- H Odagiri
- Hormone Research Institute, University of California at San Francisco 94143-0534, USA
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21
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Shieh SY, Stellrecht CM, Tsai MJ. Molecular characterization of the rat insulin enhancer-binding complex 3b2. Cloning of a binding factor with putative helicase motifs. J Biol Chem 1995; 270:21503-8. [PMID: 7665561 DOI: 10.1074/jbc.270.37.21503] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Cell-specific expression of the rat insulin II gene is in part mediated through an element located in the 5'-flanking region. The element, termed RIPE3b (-126 to -101), confers beta-cell-specific expression in conjunction with an adjacent element RIPE3a (-110 to -86). Here we report the characterization of one of the RIPE3b-binding complexes, 3b2. UV cross-linking analysis demonstrated that it is composed of at least three polypeptides: p58, p62, and p110. Furthermore, a cDNA was isolated via expression screening for binding to RIPE3b. Sequence analysis reveals that the encoded protein, designated Rip-1, possessed putative helicase motifs and a potential transcription activation domain. Overexpression of Rip-1 in cells greatly enhances the 3b2 binding complex, suggesting that Rip-1 is involved in the binding of 3b2.
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Affiliation(s)
- S Y Shieh
- Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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22
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Peyton M, Moss LG, Tsai MJ. Two distinct class A helix-loop-helix transcription factors, E2A and BETA1, form separate DNA binding complexes on the insulin gene E box. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)47336-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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23
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Melloul D, Cerasi E. Transcription of the insulin gene: towards defining the glucose-sensitive cis-element and trans-acting factors. Diabetologia 1994; 37 Suppl 2:S3-10. [PMID: 7821736 DOI: 10.1007/bf00400820] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Previous work has shown that the sequence -196 to -247 of the rat insulin I gene mediates the stimulatory effect of glucose in fetal islets. We have used adult rat and human islets to delineate the glucose-sensitive cis-element to the sequence -193 to -227. In electrophoretic mobility shift assays, a 22 bp nucleotide corresponding to the sequence -206 to -227 bound all the nuclear proteins that could be bound by the entire minienhancer sequence -196 to -247. The rat insulin I sequence -206 to -227 formed three major complexes; in contrast, the corresponding human insulin sequence formed one single band with human and rat islet nuclear extracts, corresponding to the complex C1 of the rat insulin gene. Incubation of islets with varying glucose levels resulted in a dose-dependent increase in the intensity of the C1 band, while the other nuclear complexes formed with the insulin sequence, or the AP1 and SP1 binding activities used as control, were glucose insensitive. This is thus the first demonstration of a physiologic glucose-sensitive trans-acting factor for the insulin gene, whose further study may markedly enhance our understanding of the regulation of insulin biosynthesis in normal and diabetic beta cells. Furthermore, once cloned, the introduction of this glucose sensitive factor may enable the construction of truly physiologic artificial beta cells.
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Affiliation(s)
- D Melloul
- Department of Endocrinology and Metabolism, Hebrew University Hadassah Medical Center, Jerusalem, Israel
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24
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Stein R, Henderson E, Cordle SR. Analysis of an insulin gene transcription control element. Positive and negative regulation appears to be mediated by different element sequences. FEBS Lett 1994; 338:187-90. [PMID: 8307179 DOI: 10.1016/0014-5793(94)80362-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Pancreatic beta-cell-type-specific transcription of the insulin gene is controlled by cis-acting sequence elements lying within its enhancer region. An essential element required for expression is the insulin control element (ICE). The activity of this element is regulated by both positive- and negative-acting transcription factors. In this study, we have identified the nucleotide sequences within the ICE that are required for repression in noninsulin producing cells. Our results indicate that the cis-acting sequences involved in negative control are distinct from those required in activating expression in beta cells.
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Affiliation(s)
- R Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232
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25
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Robinson G, Peshavaria M, Henderson E, Shieh S, Tsai M, Teitelman G, Stein R. Expression of the trans-active factors that stimulate insulin control element-mediated activity appear to precede insulin gene transcription. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41967-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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26
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Lamian V, Gonzalez BY, Michel FJ, Simmen RC. Non-consensus progesterone response elements mediate the progesterone-regulated endometrial expression of the uteroferrin gene. J Steroid Biochem Mol Biol 1993; 46:439-50. [PMID: 8217875 DOI: 10.1016/0960-0760(93)90098-h] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A 2.0 kilobase-pair (kb) fragment encompassing the promoter and 5' flanking region of the uteroferrin (UF) gene was previously demonstrated to confer progesterone (P) responsiveness to chimeric UF gene promoter-reporter gene constructs when transfected in endometrial cells. In the present study, transient transfection experiments with the chloramphenicol acetyltransferase reporter gene linked to the sequentially deleted UF gene 5' flanking region and to genomic fragments within this region subcloned into the heterologous SV40 promoter were used to define the progesterone-responsive elements (PRE). The identified PREs are located distal to the promoter in the region between -1754 to -1601 bp and -893 to -678 bp of the UF gene and exhibit only limited similarities to the half-sites of the consensus palindromic PRE. The non-consensus PREs bind the progesterone receptor (PR) and independently exhibit P-dependent enhancer activities within the context of homologous and heterologous promoters in endometrial and placental cell lines. The unique features of these functional PREs suggest that formation of the P-PR complex with its cognate sequences upstream of the UF gene may be less dependent on the sequence per se but may require the binding of nuclear factors proximal to the PRE to stabilize PRE-PRE interactions.
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Affiliation(s)
- V Lamian
- Department of Animal Science, University of Florida, Gainesville 32611
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27
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Toda K, Miyahara K, Kawamoto T, Ikeda H, Sagara Y, Shizuta Y. Characterization of a cis-acting regulatory element involved in human-aromatase P-450 gene expression. ACTA ACUST UNITED AC 1992; 205:303-9. [PMID: 1372865 DOI: 10.1111/j.1432-1033.1992.tb16781.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The characteristics of a cis-acting regulatory region involved in the human-aromatase P-450 gene have been examined by transient expression analysis. The region spans from -242 - -166 relative to the cap site of the gene. A fragment containing the region excised from the gene enhances heterologous promoter activity as well as its own promoter activity in a position-independent and orientation-independent manner. The fragment exerts its enhancer activity in human BeWo choriocarcinoma cells in which the aromatase P-450 gene is expressed, but not in other cell lines tested. Deletion of 38 bp from the 3' end of the fragment results in a complete loss of enhancer activity. A gel-retardation assay with nuclear extracts from BeWo cells suggests the existence of a nuclear factor(s) which interacts with the fragment. These results suggest that the regulatory element in the fragment is involved in efficient transcription of the human-aromatase P-450 gene.
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Affiliation(s)
- K Toda
- Department of Medical Chemistry, Kochi Medical School, Japan
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28
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Shieh S, Tsai M. Cell-specific and ubiquitous factors are responsible for the enhancer activity of the rat insulin II gene. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)55359-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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