1
|
Kimani CN, Reuter H, Kotzé SH, Muller CJF. Regeneration of Pancreatic Beta Cells by Modulation of Molecular Targets Using Plant-Derived Compounds: Pharmacological Mechanisms and Clinical Potential. Curr Issues Mol Biol 2023; 45:6216-6245. [PMID: 37623211 PMCID: PMC10453321 DOI: 10.3390/cimb45080392] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 07/20/2023] [Accepted: 07/22/2023] [Indexed: 08/26/2023] Open
Abstract
Type 2 diabetes (T2D) is characterized by pancreatic beta-cell dysfunction, increased cell death and loss of beta-cell mass despite chronic treatment. Consequently, there has been growing interest in developing beta cell-centered therapies. Beta-cell regeneration is mediated by augmented beta-cell proliferation, transdifferentiation of other islet cell types to functional beta-like cells or the reprograming of beta-cell progenitors into fully differentiated beta cells. This mediation is orchestrated by beta-cell differentiation transcription factors and the regulation of the cell cycle machinery. This review investigates the beta-cell regenerative potential of antidiabetic plant extracts and phytochemicals. Various preclinical studies, including in vitro, in vivo and ex vivo studies, are highlighted. Further, the potential regenerative mechanisms and the intra and extracellular mediators that are of significance are discussed. Also, the potential of phytochemicals to translate into regenerative therapies for T2D patients is highlighted, and some suggestions regarding future perspectives are made.
Collapse
Affiliation(s)
- Clare Njoki Kimani
- Biomedical Research and Innovation Platform (BRIP), South African Medical Research Council (SAMRC), Cape Town 7505, South Africa;
- Division of Clinical Pharmacology, Department of Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town 7505, South Africa
| | - Helmuth Reuter
- Division of Clinical Pharmacology, Department of Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town 7505, South Africa
| | - Sanet Henriët Kotzé
- Division of Clinical Anatomy, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town 7505, South Africa
- Division of Anatomy, Department of Biomedical Sciences, School of Veterinary Medicine, Ross University, Basseterre P.O. Box 334, Saint Kitts and Nevis
| | - Christo John Fredrick Muller
- Biomedical Research and Innovation Platform (BRIP), South African Medical Research Council (SAMRC), Cape Town 7505, South Africa;
- Centre for Cardio-Metabolic Research in Africa, Division of Medical Physiology, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch 7600, South Africa
- Department of Biochemistry and Microbiology, University of Zululand, KwaDlangezwa 3886, South Africa
| |
Collapse
|
2
|
Mandal N, Grambergs R, Mondal K, Basu SK, Tahia F, Dagogo-Jack S. Role of ceramides in the pathogenesis of diabetes mellitus and its complications. J Diabetes Complications 2021; 35:107734. [PMID: 33268241 PMCID: PMC8663915 DOI: 10.1016/j.jdiacomp.2020.107734] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/24/2020] [Accepted: 08/24/2020] [Indexed: 12/12/2022]
Abstract
Diabetes mellitus (DM) is a systemic metabolic disease that affects 463 million adults worldwide and is a leading cause of cardiovascular disease, blindness, nephropathy, peripheral neuropathy, and lower-limb amputation. Lipids have long been recognized as contributors to the pathogenesis and pathophysiology of DM and its complications, but recent discoveries have highlighted ceramides, a class of bioactive sphingolipids with cell signaling and second messenger capabilities, as particularly important contributors to insulin resistance and the underlying mechanisms of DM complications. Besides their association with insulin resistance and pathophysiology of type 2 diabetes, evidence is emerging that certain species of ceramides are mediators of cellular mechanisms involved in the initiation and progression of microvascular and macrovascular complications of DM. Advances in our understanding of these associations provide unique opportunities for exploring ceramide species as potential novel therapeutic targets and biomarkers. This review discusses the links between ceramides and the pathogenesis of DM and diabetic complications and identifies opportunities for novel discoveries and applications.
Collapse
Affiliation(s)
- Nawajes Mandal
- The University of Tennessee Health Science Center, Department of Ophthalmology, Memphis, TN 38163, USA.; The University of Tennessee Health Science Center, Department of Anatomy and Neurobiology, Memphis, TN 38163, USA..
| | - Richard Grambergs
- The University of Tennessee Health Science Center, Department of Ophthalmology, Memphis, TN 38163, USA
| | - Koushik Mondal
- The University of Tennessee Health Science Center, Department of Ophthalmology, Memphis, TN 38163, USA
| | - Sandip K Basu
- The University of Tennessee Health Science Center, Department of Ophthalmology, Memphis, TN 38163, USA
| | - Faiza Tahia
- The University of Tennessee Health Science Center, Department of Ophthalmology, Memphis, TN 38163, USA.; The University of Tennessee Health Science Center, Department of Pharmaceutical Sciences, College of Pharmacy, Memphis, TN 38163, USA
| | - Sam Dagogo-Jack
- The University of Tennessee Health Science Center, Division of Endocrinology, Memphis, TN 38163, USA.; The University of Tennessee Health Science Center, Clinical Research Center, Memphis, TN 38163, USA..
| |
Collapse
|
3
|
Li H, Wang Z, Li Y, Fang R, Wang H, Shi H, Zhang X, Zhang W, Ye L. Hepatitis B X-interacting protein promotes the formation of the insulin gene-transcribing protein complex Pdx-1/Neurod1 in animal pancreatic β-cells. J Biol Chem 2017; 293:2053-2065. [PMID: 29259128 DOI: 10.1074/jbc.m117.809582] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 12/04/2017] [Indexed: 12/26/2022] Open
Abstract
The activation of insulin gene transcription depends on multiple nuclear proteins, including the transcription factors PDX-1 and NEUROD1, which form a transcriptional complex. We recently reported that hepatitis B X-interacting protein (HBXIP, also termed LAMTOR5) can modulate glucose metabolism reprogramming in cancer cells. However, the physiological role of HBXIP in the modulation of glucose metabolism in normal tissues is poorly understood. Here, we report that Hbxip is an essential regulator of the effect of the Pdx-1/Neurod1 complex on insulin gene transcription in murine pancreatic β-cells in vitro and in vivo We found that pancreatic β-cell-specific Hbxip-knockout mice displayed higher fasting blood glucose levels and impaired glucose tolerance. Furthermore, Hbxip was involved in the regulation of insulin in the pancreas islets and increased insulin gene expression in rat pancreatic β-cells. Mechanistically, Hbxip stimulated insulin enhancer activity by interacting with Pdx-1 and recruiting Neurod1 to Pdx-1. Functionally, we provide evidence that Hbxip is required for Pdx-1/Neurod1-mediated insulin expression in rat pancreatic β-cells. Collectively, these results indicate that Hbxip is involved in the transcription of insulin by increasing the levels of the Pdx-1/Neurod1 complex in animal pancreatic β-cells. Our finding provides the insight into the mechanism by which Hbxip stimulates the transcription of the insulin gene.
Collapse
Affiliation(s)
- Hang Li
- From the State Key Laboratory of Medicinal Chemical Biology, Departments of Biochemistry and
| | - Zhen Wang
- From the State Key Laboratory of Medicinal Chemical Biology, Departments of Biochemistry and
| | - Yinghui Li
- From the State Key Laboratory of Medicinal Chemical Biology, Departments of Biochemistry and
| | - Runping Fang
- From the State Key Laboratory of Medicinal Chemical Biology, Departments of Biochemistry and
| | - Huawei Wang
- From the State Key Laboratory of Medicinal Chemical Biology, Departments of Biochemistry and
| | - Hui Shi
- From the State Key Laboratory of Medicinal Chemical Biology, Departments of Biochemistry and
| | - Xiaodong Zhang
- Cancer Research, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Weiying Zhang
- From the State Key Laboratory of Medicinal Chemical Biology, Departments of Biochemistry and
| | - Lihong Ye
- From the State Key Laboratory of Medicinal Chemical Biology, Departments of Biochemistry and
| |
Collapse
|
4
|
Corydalis edulis Maxim. Promotes Insulin Secretion via the Activation of Protein Kinase Cs (PKCs) in Mice and Pancreatic β Cells. Sci Rep 2017; 7:40454. [PMID: 28091547 PMCID: PMC5238372 DOI: 10.1038/srep40454] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 11/30/2016] [Indexed: 12/29/2022] Open
Abstract
Corydalis edulis Maxim., a widely grown plant in China, had been proposed for the treatment for type 2 diabetes mellitus. In this study, we found that C. edulis extract (CE) is protective against diabetes in mice. The treatment of hyperglycemic and hyperlipidemic apolipoprotein E (ApoE)−/− mice with a high dose of CE reduced serum glucose by 28.84% and serum total cholesterol by 17.34% and increased insulin release. We also found that CE significantly enhanced insulin secretion in a glucose-independent manner in hamster pancreatic β cell (HIT-T15). Further investigation revealed that CE stimulated insulin exocytosis by a protein kinase C (PKC)-dependent signaling pathway and that CE selectively activated novel protein kinase Cs (nPKCs) and atypical PKCs (aPKCs) but not conventional PKCs (cPKCs) in HIT-T15 cells. To the best of our knowledge, our study is the first to identify the PKC pathway as a direct target and one of the major mechanisms underlying the antidiabetic effect of CE. Given the good insulinotropic effect of this herbal medicine, CE is a promising agent for the development of new drugs for treating diabetes.
Collapse
|
5
|
Kuzmenko DI, Klimentyeva TK. Role of Ceramide in Apoptosis and Development of Insulin Resistance. BIOCHEMISTRY (MOSCOW) 2017; 81:913-27. [PMID: 27682164 DOI: 10.1134/s0006297916090017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
This review presents data on the functional biochemistry of ceramide, one of the key sphingolipids with properties of a secondary messenger. Molecular mechanisms of the involvement of ceramide in apoptosis in pancreatic β-cells and its role in the formation of insulin resistance in pathogenesis of type 2 diabetes are reviewed. One of the main predispositions for the development of insulin resistance and diabetes is obesity, which is associated with ectopic fat deposition and significant increase in intracellular concentrations of cytotoxic ceramides. A possible approach to the restoration of tissue sensitivity to insulin in type 2 diabetes based on selective reduction of the content of cytotoxic ceramides is discussed.
Collapse
Affiliation(s)
- D I Kuzmenko
- Siberian State Medical University, Ministry of Healthcare of the Russian Federation, Tomsk, 634050, Russia.
| | | |
Collapse
|
6
|
Li F, Peng Y, Zhang M, Yang P, Qu S. Sleeve gastrectomy activates the GLP-1 pathway in pancreatic β cells and promotes GLP-1-expressing cells differentiation in the intestinal tract. Mol Cell Endocrinol 2016; 436:33-40. [PMID: 27436347 DOI: 10.1016/j.mce.2016.07.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 06/25/2016] [Accepted: 07/16/2016] [Indexed: 01/19/2023]
Abstract
Db/db mouse was used to study the underlying mechanisms by which Sleeve gastrectomy (SG) improves β-cell function. We investigated β-cell function, plasma active GLP-1 levels, the GLP-1R pathway in β cells and L cell differentiation. After SG, β-cell function was significantly increased, and the GLP-1R-PKCζ-PDX-1 pathway was active in β cells. Plasma active GLP-1 levels, as well as the number of L cells in the jejunum, were significantly increased after SG. The expression of early transcription factors (TF), including Ngn3, FoxA1 and Nkx2.2, was not compromised by chronic hyperglycemia. In contrast, the expression of the downstream TF PAX6 was affected, and this down-regulation could be reversed by SG. So, SG can maintain L cell differentiation, increase plasma active GLP-1 level, sustain the activation of the GLP-1R pathway and improve β cell function in Db/db mice. Our results show that SG can overall improve the function of the entero-insular axis.
Collapse
Affiliation(s)
- Feng Li
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tong-Ji University, 301 Middle Yan-Chang Road, Shanghai, 200072, China.
| | - Ying Peng
- Department of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases and Shanghai Institute of Endocrinology and Metabolism, Rui-Jin Hospital, Shanghai Jiao-Tong University School of Medicine, 197 Rui-Jin 2nd Road, Shanghai, 200025, China
| | - Manna Zhang
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tong-Ji University, 301 Middle Yan-Chang Road, Shanghai, 200072, China
| | - Peng Yang
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tong-Ji University, 301 Middle Yan-Chang Road, Shanghai, 200072, China
| | - Shen Qu
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tong-Ji University, 301 Middle Yan-Chang Road, Shanghai, 200072, China.
| |
Collapse
|
7
|
IL-32θ downregulates CCL5 expression through its interaction with PKCδ and STAT3. Cell Signal 2014; 26:3007-15. [PMID: 25280942 DOI: 10.1016/j.cellsig.2014.09.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 08/15/2014] [Accepted: 09/15/2014] [Indexed: 01/11/2023]
Abstract
Interleukin-32 (IL-32) exists in several isoforms and plays an important role in inflammatory response. Recently, we identified a new isoform, IL-32θ, and performed a microarray analysis to identify IL-32θ-regulated genes in THP-1 myelomonocytic cells. Upon stimulating IL-32θ-expressing THP-1 cells with phorbol myristate acetate (PMA), we found that the CCL5 transcript level was significantly reduced. We confirmed the downregulation of CCL5 protein expression by using an enzyme-linked immunosorbent assay (ELISA). Because STAT3 phosphorylation on Ser727 by PKCδ is reported to suppress CCL5 protein expression, we examined whether IL-32θ-mediated STAT3 Ser727 phosphorylation occurs through an interaction with PKCδ. In this study, we first demonstrate that IL-32θ interacts with PKCδ and STAT3 using co-immunoprecipitation (Co-IP) and pulldown assay. Moreover, STAT3 was rarely phosphorylated on Ser727 in the absence of IL-32θ, leading to the binding of STAT3 to the CCL5 promoter. These results indicate that IL-32θ, through its interaction with PKCδ, downregulates CCL5 expression by mediating the phosphorylation of STAT3 on Ser727 to render it transcriptionally inactive. Therefore, similar to what we have reported for IL-32α and IL-32β, our data from this study suggests that the newly identified IL-32θ isoform also acts as an intracellular modulator of inflammation.
Collapse
|
8
|
Liu SH, Zhou G, Yu J, Wu J, Nemunaitis J, Senzer N, Dawson D, Li M, Fisher WE, Brunicardi FC. Notch1 activation up-regulates pancreatic and duodenal homeobox-1. Genes (Basel) 2013; 4:358-74. [PMID: 24705209 PMCID: PMC3924823 DOI: 10.3390/genes4030358] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 07/02/2013] [Accepted: 07/11/2013] [Indexed: 12/28/2022] Open
Abstract
Transcription factor pancreatic and duodenal homeobox-1 (PDX-1) plays an essential role in pancreatic development, β-cell differentiation, maintenance of normal β-cell function and tumorigenesis. PDX-1 expression is tightly controlled through a variety of mechanisms under different cellular contexts. We report here that overexpression of Notch1 intracellular domain (NICD), an activated form of Notch1, enhanced PDX-1 expression in both PDX-1 stable HEK293 cells and mouse insulinoma β-TC-6 cells, while NICD shRNA inhibited the enhancing effect. NICD-enhanced PDX-1 expression was accompanied by increased insulin expression/secretion and cell proliferation in β-TC-6 cells, which was reversed by NICD shRNA. Cre activation-induced specific expression of NICD in islet β cells of transgenic βNICD+/+ mice induced increased expression of PDX-1, insulin and proliferating cell nuclear antigen (PCNA) and decreased expression of p27 with accompanied fasting hyperinsulinemia and hypoglycemia and altered responses to intraperitoneal glucose tolerance test. Systemically delivered NICD shRNA suppressed islet expression of PDX-1 and reversed the hypoglycemia and hyperinsulinemia. Moreover, expression levels of NICD were correlated with those of PDX-1 in human pancreatic neuroendocrine tumor. Thus, Notch1 acts as a positive regulator for PDX-1 expression, cooperates with PDX-1 in the development of insulin overexpression and islet cell neoplasia and represents a potential therapeutic target for islet neoplasia.
Collapse
Affiliation(s)
- Shi-He Liu
- Department of Surgery, David Geffen School of Medicine at University of California, Los Angeles, CA 90095, USA.
| | - Guisheng Zhou
- Department of Surgery, David Geffen School of Medicine at University of California, Los Angeles, CA 90095, USA.
| | - Juehua Yu
- Department of Surgery, David Geffen School of Medicine at University of California, Los Angeles, CA 90095, USA.
| | - James Wu
- Department of Surgery, David Geffen School of Medicine at University of California, Los Angeles, CA 90095, USA.
| | | | - Neil Senzer
- Mary Crowley Cancer Research Center, Dallas, TX 75230, USA.
| | - David Dawson
- CURE: Digestive Disease Research Center, David Geffen School of Medicine at University of California, Los Angeles, CA 90095, USA.
| | - Min Li
- Department of Neurosurgery, UT-Houston School of Medicine, Houston, TX 77030, USA.
| | - William E Fisher
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, TX 77030, USA.
| | - F Charles Brunicardi
- Department of Surgery, David Geffen School of Medicine at University of California, Los Angeles, CA 90095, USA.
| |
Collapse
|
9
|
Role of ceramide in diabetes mellitus: evidence and mechanisms. Lipids Health Dis 2013; 12:98. [PMID: 23835113 PMCID: PMC3716967 DOI: 10.1186/1476-511x-12-98] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 06/28/2013] [Indexed: 02/06/2023] Open
Abstract
Diabetes mellitus is a metabolic disease with multiple complications that causes serious diseases over the years. The condition leads to severe economic consequences and is reaching pandemic level globally. Much research is being carried out to address this disease and its underlying molecular mechanism. This review focuses on the diverse role and mechanism of ceramide, a prime sphingolipid signaling molecule, in the pathogenesis of type 1 and type 2 diabetes and its complications. Studies using cultured cells, animal models, and human subjects demonstrate that ceramide is a key player in the induction of β-cell apoptosis, insulin resistance, and reduction of insulin gene expression. Ceramide induces β-cell apoptosis by multiple mechanisms namely; activation of extrinsic apoptotic pathway, increasing cytochrome c release, free radical generation, induction of endoplasmic reticulum stress and inhibition of Akt. Ceramide also modulates many of the insulin signaling intermediates such as insulin receptor substrate, Akt, Glut-4, and it causes insulin resistance. Ceramide reduces the synthesis of insulin hormone by attenuation of insulin gene expression. Better understanding of this area will increase our understanding of the contribution of ceramide to the pathogenesis of diabetes, and further help in identifying potential therapeutic targets for the management of diabetes mellitus and its complications.
Collapse
|
10
|
Nyren-Erickson EK, Jones JM, Srivastava DK, Mallik S. A disintegrin and metalloproteinase-12 (ADAM12): function, roles in disease progression, and clinical implications. Biochim Biophys Acta Gen Subj 2013; 1830:4445-55. [PMID: 23680494 DOI: 10.1016/j.bbagen.2013.05.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 05/03/2013] [Accepted: 05/06/2013] [Indexed: 12/18/2022]
Abstract
BACKGROUND A disintegrin and metalloproteinase-12 (ADAM12) is a member of the greater ADAM family of enzymes: these are multifunctional, generally membrane-bound, zinc proteases for which there are forty genes known (21 of these appearing in humans). ADAM12 has been implicated in the pathogenesis of various cancers, liver fibrogenesis, hypertension, and asthma, and its elevation or decrease in human serum has been linked to these and other physiological/pathological conditions. SCOPE In this review, we begin with a brief overview of the ADAM family of enzymes and protein structure. We then discuss the role of ADAM12 in the progression and/or diagnosis of various disease conditions, and we will conclude with an exploration of currently known natural and synthetic inhibitors. MAJOR CONCLUSION ADAM12 has potential to emerge as a successful drug target, although targeting the metalloproteinase domain with any specificity will be difficult to achieve due to structural similarity between the members of the ADAM and MMP family of enzymes. Overall, more research is required to establish ADAM12 being as a highly desirable biomarker and drug target of different diseases, and their selective inhibitors as potential therapeutic agents. GENERAL SIGNIFICANCE Given the appearance of elevated levels of ADAM12 in various diseases, particularly breast cancer, our understanding of this enzyme both as a biomarker and a potential drug target could help make significant inroads into both early diagnosis and treatment of disease.
Collapse
Affiliation(s)
- Erin K Nyren-Erickson
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, ND 58108-6050, USA
| | | | | | | |
Collapse
|
11
|
Zhou G, Liu SH, Shahi KM, Wang H, Duan X, Lin X, Feng XH, Li M, Fisher WE, Demayo FJ, Dawson D, Brunicardi FC. Negative regulation of pancreatic and duodenal homeobox-1 by somatostatin receptor subtype 5. Mol Endocrinol 2012; 26:1225-34. [PMID: 22669743 DOI: 10.1210/me.2012-1095] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Somatostatin receptor subtype 5 (SSTR5) mediates the inhibitory effect of somatostatin and its analogs on insulin expression/secretion and islet cell proliferation. We provide biochemical and genetic evidence that SSTR5 exerted its physiological actions via down-regulating pancreatic and duodenal homeobox-1 (PDX-1), a β-cell-specific homeodomain-containing transcription factor. Cotransfection of SSTR5 with PDX-1 resulted in dose-dependent inhibition of PDX-1 expression in human embryonic kidney 293 cells. SSTR5 agonist RPL-1980 inhibited PDX-1 expression and abolished glucagon-like peptide 1-stimulated PDX-1 expression in mouse insulinoma β-TC-6 cells. SSTR5 knockdown by short hairpin RNA led to increased PDX-1 expression that was accompanied by enhanced insulin secretion stimulated by high glucose in β-TC6 cells and alternated expressions of cell cycle proteins that favor cell proliferation in mouse insulinoma MIN6 cells. Quantitative RT-PCR analysis showed that cotransfected SSTR5 inhibited PDX-1 mRNA expression, whereas knockdown of SSTR5 increased PDX-1 mRNA expression. In addition, we found that cotransfected wild-type SSTR5 increased PDX-1 ubiquitination in human embryonic kidney 293 cells, whereas SSTR5 P335L, a hypofunctional single nucleotide polymorphism of SSTR5, inhibited PDX-1 ubiquitination. SSTR5 knockout resulted in increased expression of PDX-1, insulin, and proliferating cell nuclear antigen in the islets of sstr(-/-) mice. Immunohistochemistry analysis showed that SSTR5 P335L was associated with elevated expression of PDX-1 in human pancreatic neuroendocrine tumor. Taken together, our studies demonstrated that SSTR5 is a negative regulator for PDX-1 expression and that SSTR5 may mediate the inhibitory effects of somatostatin and its analogs on insulin expression/secretion and cell proliferation via down-regulating PDX-1 at both transcriptional and posttranslational levels.
Collapse
Affiliation(s)
- Guisheng Zhou
- Department of Surgery, David Geffen School of Medicine at University of California, Los Angeles, California 90095, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Suefuji M, Furukawa N, Matsumoto K, Oiso H, Shimoda S, Yoshinaga T, Matsuyama R, Miyagawa K, Kondo T, Kawashima J, Tsuruzoe K, Araki E. The impact of Ca²⁺/calmodulin-dependent protein kinase II on insulin gene expression in MIN6 cells. Biochem Biophys Res Commun 2012; 421:801-7. [PMID: 22554507 DOI: 10.1016/j.bbrc.2012.04.091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 04/17/2012] [Indexed: 10/28/2022]
Abstract
Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is expressed in insulin-secreting β cells. However, the effects of CaMKII on insulin synthesis are unknown. Although Ser133 phosphorylation of cyclic AMP-responsive element-binding protein (CREB) typically increases CREB transcriptional activity, CaMKII phosphorylates CREB at Ser142 and at Ser133 to exert a dominant inhibitory effect. Our objective was to characterize the role of CaMKII in insulin gene expression. In MIN6 cells, insulin gene promoter activity was significantly down-regulated by wild-type (WT) CaMKIIδ2, but was significantly upregulated after small interfering RNA (siRNA) knockdown of CaMKIIδ expression. These results were independent of glucose concentrations and membrane depolarization. Insulin mRNA levels were also decreased by WT CaMKIIδ2 and increased by CaMKIIδ siRNA. Downregulation of insulin gene promoter activity by WT CaMKIIδ2 was partly mediated via cyclic AMP-responsive element 2 (CRE2). WT CaMKIIδ2 significantly increased CREB phosphorylation at Ser142 and significantly decreased binding to CREB binding protein (CBP), whereas kinase dead CaMKIIδ2 did not. Our results indicate that CaMKIIδ2 downregulates insulin gene expression by Ser142 phosphorylation of CREB and reducing binding of CREB to CBP.
Collapse
Affiliation(s)
- Mihoshi Suefuji
- Department of Metabolic Medicine, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Velazquez-Garcia S, Valle S, Rosa TC, Takane KK, Demirci C, Alvarez-Perez JC, Mellado-Gil JM, Ernst S, Scott DK, Vasavada RC, Alonso LC, Garcia-Ocaña A. Activation of protein kinase C-ζ in pancreatic β-cells in vivo improves glucose tolerance and induces β-cell expansion via mTOR activation. Diabetes 2011; 60:2546-59. [PMID: 21911744 PMCID: PMC3178296 DOI: 10.2337/db10-1783] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
OBJECTIVE PKC-ζ activation is a key signaling event for growth factor-induced β-cell replication in vitro. However, the effect of direct PKC-ζ activation in the β-cell in vivo is unknown. In this study, we examined the effects of PKC-ζ activation in β-cell expansion and function in vivo in mice and the mechanisms associated with these effects. RESEARCH DESIGN AND METHODS We characterized glucose homeostasis and β-cell phenotype of transgenic (TG) mice with constitutive activation of PKC-ζ in the β-cell. We also analyzed the expression and regulation of signaling pathways, G1/S cell cycle molecules, and β-cell functional markers in TG and wild-type mouse islets. RESULTS TG mice displayed increased plasma insulin, improved glucose tolerance, and enhanced insulin secretion with concomitant upregulation of islet insulin and glucokinase expression. In addition, TG mice displayed increased β-cell proliferation, size, and mass compared with wild-type littermates. The increase in β-cell proliferation was associated with upregulation of cyclins D1, D2, D3, and A and downregulation of p21. Phosphorylation of D-cyclins, known to initiate their rapid degradation, was reduced in TG mouse islets. Phosphorylation/inactivation of GSK-3β and phosphorylation/activation of mTOR, critical regulators of D-cyclin expression and β-cell proliferation, were enhanced in TG mouse islets, without changes in Akt phosphorylation status. Rapamycin treatment in vivo eliminated the increases in β-cell proliferation, size, and mass; the upregulation of cyclins Ds and A in TG mice; and the improvement in glucose tolerance-identifying mTOR as a novel downstream mediator of PKC-ζ-induced β-cell replication and expansion in vivo. CONCLUSIONS PKC:-ζ, through mTOR activation, modifies the expression pattern of β-cell cycle molecules leading to increased β-cell replication and mass with a concomitant enhancement in β-cell function. Approaches to enhance PKC-ζ activity may be of value as a therapeutic strategy for the treatment of diabetes.
Collapse
Affiliation(s)
- Silvia Velazquez-Garcia
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shelley Valle
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Taylor C. Rosa
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Karen K. Takane
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Cem Demirci
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Juan C. Alvarez-Perez
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Jose M. Mellado-Gil
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Sara Ernst
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Donald K. Scott
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Rupangi C. Vasavada
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Laura C. Alonso
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Adolfo Garcia-Ocaña
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
- Corresponding author: Adolfo Garcia-Ocaña,
| |
Collapse
|
14
|
Abstract
Type 2 diabetes occurs due to a relative deficit in β-cell mass or function. Glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), cholecystokinin (CCK), and gastrin are gastrointestinal hormones that are secreted in response to nutrient intake, regulating digestion, insulin secretion, satiety, and β-cell mass. In this review, we focus upon β-cell mass regulation. β-cell mass expands through β-cell proliferation and islet neogenesis; β-cell mass is lost via apoptosis. GLP-1 and GIP are well-studied gastrointestinal hormones and influence β-cell proliferation, apoptosis, and islet neogenesis. CCK regulates β-cell apoptosis and mitogenesis, and gastrin stimulates islet neogenesis. GLP-1 and GIP bind to G protein-coupled receptors and regulate β-cell mass via multiple signaling pathways. The protein kinase A pathway is central to this process because it directly regulates proliferative and anti-apoptotic genes and transactivates several signaling cascades, including Akt and mitogen-activated protein kinases. However, the signaling pathways downstream of G protein-coupled CCK receptors that influence β-cell mass remain unidentified. Gastrointestinal hormones integrate nutrient signals from the gut to the β-cell, regulating insulin secretion and β-cell mass adaptation.
Collapse
Affiliation(s)
- Jeremy A Lavine
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | | |
Collapse
|
15
|
Shieh JM, Wu HT, Cheng KC, Cheng JT. Melatonin ameliorates high fat diet-induced diabetes and stimulates glycogen synthesis via a PKCzeta-Akt-GSK3beta pathway in hepatic cells. J Pineal Res 2009; 47:339-44. [PMID: 19817973 DOI: 10.1111/j.1600-079x.2009.00720.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Low levels of melatonin in circulation had been reported to be related to the development of diabetes. Melatonin administration in animals increases hepatic glycogen content to lower blood glucose. However, the signaling pathway for these effects is still unclear. The present study shows that intraperitoneal injection of 10 mg/kg melatonin ameliorated glucose utilization and insulin sensitivity in high fat diet-induced diabetic mice with an increase in hepatic glycogen and improvement in liver steatosis. We used HepG2 cells to investigate the signaling pathways for the melatonin-stimulated hepatic glycogen increment. Treatment of HepG2 cells with 1 nm melatonin markedly increased glycogen synthesis which was blocked by the melatonin receptor antagonist luzindole. In addition, melatonin increased the phosphorylation of subcellular signals at the level of protein kinase C zeta (PKCzeta), Akt, and glycogen synthase kinase 3beta (GSK3beta) while the increase in glycogen synthesis induced by melatonin was inhibited by PKCzeta pseudo-peptide. However, 3',5'-cyclic adenosine monophosphate-activated protein kinase (AMPK) was not influenced by melatonin treatment. Taken together, melatonin improves glucose intolerance and insulin resistance in high fat diet-induced diabetic mice and stimulates glycogen synthesis via a PKCzeta-Akt-GSK3beta pathway in HepG2 cells.
Collapse
Affiliation(s)
- Jiunn-Min Shieh
- Department of Chest Medicine, Chi-Mei Medical Center, Yong Kang City, Taiwan
| | | | | | | |
Collapse
|
16
|
Abstract
Members of the serine/threonine PKC (protein kinase C) family perform diverse functions in multiple cell types. All members of the family are activated in signalling cascades triggered by occupation of cell surface receptors, but the cPKC (conventional PKC) and nPKC (novel PKC) isoforms are also responsive to fatty acid metabolites. PKC isoforms are involved in various aspects of pancreatic beta-cell function, including cell proliferation, differentiation and death, as well as regulation of secretion in response to glucose and muscarinic receptor agonists. Recently, the nPKC isoform, PKCepsilon, has also been implicated in the loss of insulin secretory responsiveness that underpins the development of Type 2 diabetes.
Collapse
|
17
|
Schmitz-Peiffer C, Biden TJ. Protein kinase C function in muscle, liver, and beta-cells and its therapeutic implications for type 2 diabetes. Diabetes 2008; 57:1774-83. [PMID: 18586909 PMCID: PMC2453608 DOI: 10.2337/db07-1769] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 04/15/2008] [Indexed: 01/27/2023]
Affiliation(s)
| | - Trevor J. Biden
- From the Garvan Institute of Medical Research, Darlinghurst, Australia
| |
Collapse
|
18
|
Carlotti F, Zaldumbide A, Charif H, de Koning EJ, Luider TM, Hoeben RC. The 45-kDa form of Pdx-1 does not result from post-translational modifications. Biochem Biophys Res Commun 2008; 370:225-9. [PMID: 18361919 DOI: 10.1016/j.bbrc.2008.03.071] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Accepted: 03/12/2008] [Indexed: 10/22/2022]
Abstract
Pdx-1 is a key regulator of glucose-stimulated insulin gene transcription in beta-cells. The regulation of Pdx-1 in response to glucose has previously been associated with a remarkable shift in electrophoretic mobility on SDS-PAGE from 31 to 45kDa. This has been attributed to different post-translational modifications including phosphorylation, sumoylation or glycosylation. However, and in contrast with previous studies, we describe in this paper that Pdx-1 produced in Escherichia coli, by in vitro transcription/translation or exogenously expressed in eukaryotic cells, migrates with an apparent molecular mass of 45kDa despite a calculated mass of 31kDa. Moreover, we show that the migration of endogenous Pdx-1 obtained from a mouse beta-cell line as well as from human primary islets is not dependent on glucose concentration. Taken together, these data, validated by mass spectrometry techniques, establish that anomalous migration of Pdx-1 on SDS-PAGE does not result from post-translational modifications.
Collapse
Affiliation(s)
- Françoise Carlotti
- Department of Molecular Cell Biology-Virus and Stem Cell Biology Laboratory, Leiden University Medical Center, Postal Zone S1-P, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
| | | | | | | | | | | |
Collapse
|
19
|
Vasavada RC, Wang L, Fujinaka Y, Takane KK, Rosa TC, Mellado-Gil JMD, Friedman PA, Garcia-Ocaña A. Protein kinase C-zeta activation markedly enhances beta-cell proliferation: an essential role in growth factor mediated beta-cell mitogenesis. Diabetes 2007; 56:2732-43. [PMID: 17686945 DOI: 10.2337/db07-0461] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Diabetes results from a deficiency of functional beta-cells. Previous studies have identified hepatocyte growth factor (HGF) and parathyroid hormone-related protein (PTHrP) as two potent beta-cell mitogens. The objective of this study is to determine 1) whether HGF and PTHrP have additive/synergistic effects on beta-cell growth and proliferation; 2) the signaling pathways through which these growth factors mediate beta-cell mitogenesis; and 3) whether activation of this/these signaling pathway(s) enhances human beta-cell replication. RESEARCH DESIGN AND METHODS We generated and phenotypically analyzed doubly transgenic mice overexpressing PTHrP and HGF in the beta-cell. INS-1 and primary mouse and human islet cells were used to identify mitogenic signaling pathways activated by HGF and/or PTHrP. RESULTS Combined overexpression of HGF and PTHrP in the beta-cell of doubly transgenic mice did not result in additive/synergistic effects on beta-cell growth and proliferation, suggesting potential cross-talk between signaling pathways activated by both growth factors. Examination of these signaling pathways in INS-1 cells revealed atypical protein kinase C (PKC) as a novel intracellular target activated by both HGF and PTHrP in beta-cells. Knockdown of PKC zeta, but not PKC iota/lambda, expression using specific small-interfering RNAs blocked growth factor-induced INS-1 cell proliferation. Furthermore, adenovirus-mediated delivery of kinase-dead PKC zeta completely inhibited beta-cell proliferation in primary islet cells overexpressing PTHrP and/or HGF. Finally, adenovirus-mediated delivery of constitutively active PKC zeta in mouse and human primary islet cells significantly enhanced beta-cell proliferation. CONCLUSIONS PKC zeta is essential for PTHrP- and HGF-induced beta-cell proliferation. PKC zeta activation could be useful in therapeutic strategies for expanding beta-cell mass in vitro and in vivo.
Collapse
Affiliation(s)
- Rupangi C Vasavada
- Department of Medicine, Division of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
| | | | | | | | | | | | | | | |
Collapse
|
20
|
Kuribayashi K, Nakamura K, Tanaka M, Sato T, Kato J, Sasaki K, Takimoto R, Kogawa K, Terui T, Takayama T, Onuma T, Matsunaga T, Niitsu Y. Essential role of protein kinase C zeta in transducing a motility signal induced by superoxide and a chemotactic peptide, fMLP. ACTA ACUST UNITED AC 2007; 176:1049-60. [PMID: 17389234 PMCID: PMC2064088 DOI: 10.1083/jcb.200607019] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Under various pathological conditions, including infection, malignancy, and autoimmune diseases, tissues are incessantly exposed to reactive oxygen species produced by infiltrating inflammatory cells. We show augmentation of motility associated with morphological changes of human squamous carcinoma SASH1 cells, human peripheral monocytes (hPMs), and murine macrophage-like cell line J774.1 by superoxide stimulation. We also disclose that motility of hPMs and J774.1 induced by a chemotactic peptide (N-formyl-methionyl-leucyl-phenylalanine [fMLP]) was inhibited by superoxide dismutase or N-acetylcystein, indicating stimulation of motility by superoxide generated by fMLP stimulation. In these cells, protein kinase C (PKC) ζ was activated to phosphorylate RhoGDI-1, which liberated RhoGTPases, leading to their activation. These events were inhibited by dominant-negative PKCζ in SASH1 cells, myristoylated PKCζ peptides in hPMs and J774.1, or a specific inhibitor of RhoGTPase in SASH1, hPMs, and J774.1. These results suggest a new approach for manipulation of inflammation as well as tumor cell invasion by targeting this novel signaling pathway.
Collapse
Affiliation(s)
- Kageaki Kuribayashi
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, Chuo-ku, Sapporo 060-8543, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Miele C, Raciti GA, Cassese A, Romano C, Giacco F, Oriente F, Paturzo F, Andreozzi F, Zabatta A, Troncone G, Bosch F, Pujol A, Chneiweiss H, Formisano P, Beguinot F. PED/PEA-15 regulates glucose-induced insulin secretion by restraining potassium channel expression in pancreatic beta-cells. Diabetes 2007; 56:622-33. [PMID: 17327429 DOI: 10.2337/db06-1260] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes (ped/pea-15) gene is overexpressed in human diabetes and causes this abnormality in mice. Transgenic mice with beta-cell-specific overexpression of ped/pea-15 (beta-tg) exhibited decreased glucose tolerance but were not insulin resistant. However, they showed impaired insulin response to hyperglycemia. Islets from the beta-tg also exhibited little response to glucose. mRNAs encoding the Sur1 and Kir6.2 potassium channel subunits and their upstream regulator Foxa2 were specifically reduced in these islets. Overexpression of PED/PEA-15 inhibited the induction of the atypical protein kinase C (PKC)-zeta by glucose in mouse islets and in beta-cells of the MIN-6 and INS-1 lines. Rescue of PKC-zeta activity elicited recovery of the expression of the Sur1, Kir6.2, and Foxa2 genes and of glucose-induced insulin secretion in PED/PEA-15-overexpressing beta-cells. Islets from ped/pea-15-null mice exhibited a twofold increased activation of PKC-zeta by glucose; increased abundance of the Sur1, Kir6.2, and Foxa2 mRNAs; and enhanced glucose effect on insulin secretion. In conclusion, PED/PEA-15 is an endogenous regulator of glucose-induced insulin secretion, which restrains potassium channel expression in pancreatic beta-cells. Overexpression of PED/PEA-15 dysregulates beta-cell function and is sufficient to impair glucose tolerance in mice.
Collapse
Affiliation(s)
- Claudia Miele
- Department of Cellular and Molecular Biology and Pathology, Federico II University of Naples, via Sergio Pansini 5, Naples 80131, Italy
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Liu XJ, He AB, Chang YS, Fang FD. Atypical protein kinase C in glucose metabolism. Cell Signal 2006; 18:2071-6. [PMID: 16787739 DOI: 10.1016/j.cellsig.2006.04.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Accepted: 04/28/2006] [Indexed: 01/17/2023]
Abstract
Type 2 diabetes mellitus is a multigenic disease with evident genetic predisposition, and complex pathogenesis in which environmental and genetic factors interact. The disorder of body utilization glucose is a crucial reason for causing diabetes. Atypical PKCs, belonging to Ser/Thr protein kinase, have many important biological functions in vivo, and may be involved in the pathogenesis of diabetes mellitus. APKCs participate in glucose metabolism by regulating glucose transport and absorption, glycogen synthesis, and insulin secretion. The exact mechanism by which aPKCs participate in glucose metabolism remains unclear. So far, the clarification of which will be helpful for the prevention and cure of type 2 diabetes.
Collapse
Affiliation(s)
- Xiao-Jun Liu
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences and School of Basic Medicine Peking Union Medical College, Beijing 100005, China
| | | | | | | |
Collapse
|
23
|
BINETTE TANYAM, DUFOUR JANNETTEM, KORBUTT GREGORYS. In Vitro Maturation of Neonatal Porcine Islets. Ann N Y Acad Sci 2006. [DOI: 10.1111/j.1749-6632.2001.tb03822.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
24
|
Hashimoto N, Kido Y, Uchida T, Matsuda T, Suzuki K, Inoue H, Matsumoto M, Ogawa W, Maeda S, Fujihara H, Ueta Y, Uchiyama Y, Akimoto K, Ohno S, Noda T, Kasuga M. PKClambda regulates glucose-induced insulin secretion through modulation of gene expression in pancreatic beta cells. J Clin Invest 2005; 115:138-45. [PMID: 15630453 PMCID: PMC539193 DOI: 10.1172/jci22232] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2004] [Accepted: 10/26/2004] [Indexed: 12/15/2022] Open
Abstract
Altered regulation of insulin secretion by glucose is characteristic of individuals with type 2 diabetes mellitus, although the mechanisms that underlie this change remain unclear. We have now generated mice that lack the lambda isoform of PKC in pancreatic beta cells (betaPKClambda(-/-) mice) and show that these animals manifest impaired glucose tolerance and hypoinsulinemia. Furthermore, insulin secretion in response to high concentrations of glucose was impaired, whereas the basal rate of insulin release was increased, in islets isolated from betaPKClambda(-/-) mice. Neither the beta cell mass nor the islet insulin content of betaPKClambda(-/-) mice differed from that of control mice, however. The abundance of mRNAs for Glut2 and HNF3beta was reduced in islets of betaPKClambda(-/-) mice, and the expression of genes regulated by HNF3beta was also affected (that of Sur1 and Kir6.2 genes was reduced, whereas that of hexokinase 1 and hexokinase 2 genes was increased). Normalization of HNF3beta expression by infection of islets from betaPKClambda(-/-) mice with an adenoviral vector significantly reversed the defect in glucose-stimulated insulin secretion. These results indicate that PKClambda plays a prominent role in regulation of glucose-induced insulin secretion by modulating the expression of genes important for beta cell function.
Collapse
Affiliation(s)
- Naoko Hashimoto
- Department of Clinical Molecular Medicine, Division of Diabetes and Digestive and Kidney Diseases, Kobe University Graduate School of Medicine, Kobe, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Yang SN, Berggren PO. CaV2.3 channel and PKClambda: new players in insulin secretion. J Clin Invest 2005; 115:16-20. [PMID: 15630435 PMCID: PMC539207 DOI: 10.1172/jci23970] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Insulin secretion is critically dependent on the proper function of a complex molecular network. Ca(V)2.3-knockout (Ca(V)2.3(-/-)) and PKClambda-knockout (PKClambda(-/-)) mouse models now suggest that these 2 players, the Ca(v)2.3 channel and PKClambda, are important constituents of this molecular network. Subsequent to glucose stimulation, insulin is released from the pancreatic beta cell in a biphasic pattern, i.e., a rapid initial phase followed by a slower, more sustained phase. Interestingly, Ca(2+) influx through the Ca(V)2.3 channel regulates only the second phase of insulin secretion. PKClambda seems to enter the beta cell nucleus and in turn modulates the expression of several genes critical for beta cell secretory function. Studies by Hashimoto et al. and Jing et al. in this issue of the JCI set out to answer the question of why numerous isoforms of proteins with similar functions are present in the beta cell. This is important, since it has been difficult to understand the modulatory and/or regulatory roles of different isoforms of proteins in defined subcellular compartments and at various times during the secretory process in both beta cell physiology and pathophysiology.
Collapse
Affiliation(s)
- Shao-Nian Yang
- The Rolf Luft Center for Diabetes Research, Karolinska Diabetes Center, Department of Molecular Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | | |
Collapse
|
26
|
|
27
|
Chuang LY, Guh JY, Liu SF, Hung MY, Liao TN, Chiang TA, Huang JS, Huang YL, Lin CF, Yang YL. Regulation of type II transforming-growth-factor-beta receptors by protein kinase C iota. Biochem J 2003; 375:385-93. [PMID: 12841849 PMCID: PMC1223681 DOI: 10.1042/bj20030522] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2003] [Revised: 06/16/2003] [Accepted: 07/04/2003] [Indexed: 11/17/2022]
Abstract
TGF-beta (transforming growth factor-beta) is implicated in the pathogenesis of diabetic nephropathy. We previously demonstrated that up-regulation of type II TGF-beta receptor (TbetaRII) induced by high glucose might contribute to distal tubular hypertrophy [Yang, Guh, Yang, Lai, Tsai, Hung, Chang and Chuang (1998) J. Am. Soc. Nephrol. 9, 182-193]. We have elucidated the mechanism by using cultured Madin-Darby canine kidney cells. Enhancer assay and electrophoretic-mobility-shift assay were used to estimate the involvement of transcription factors. Western blotting and an in vitro kinase assay were used to evaluate the level and activity of protein kinase. We showed that glucose (100-900 mg/dl) induced an increase in mRNA level and promoter activity of TbetaRII (note: 'mg/dl' are the units commonly used in diabetes studies). The promoter region -209 to -177 appeared to contribute to positive transactivation of TbetaRII promoter by comparing five TbetaRII-promoter-CAT (chloramphenicol acetyl-transferase) plasmids. Moreover, the transcription factor AP-1 (activator protein 1) was significantly activated and specifically binds to TbetaRII promoter (-209 to -177). More importantly, we found that atypical PKC iota might be pivotal for high glucose-induced increase in both AP-1 binding and TbetaRII promoter activity. First, high glucose induced cytosolic translocation, activation and autophosphorylation of PKC iota. Secondly, antisense PKC iota expression plasmids attenuated high-glucose-induced increase in AP-1 binding and TbetaRII promoter activity; moreover, sense PKC iota expression plasmids enhanced these instead. Finally, we showed that antisense PKC iota expression plasmids might partly attenuate a high-glucose/TGF-beta1-induced increase in fibronectin. We conclude that PKC iota might mediate high-glucose-induced increase in TbetaRII promoter activity. In addition, antisense PKC iota expression plasmid effectively suppressed up-regulation of TbetaRII and fibronectin in hyperglycaemic distal-tubule cells.
Collapse
MESH Headings
- Analysis of Variance
- Animals
- Blotting, Northern
- Cell Line
- Cell Membrane/enzymology
- Chloramphenicol O-Acetyltransferase/genetics
- Chloramphenicol O-Acetyltransferase/metabolism
- Cytosol/enzymology
- Dose-Response Relationship, Drug
- Enzyme Activation/drug effects
- Gene Expression Regulation/drug effects
- Glucose/pharmacology
- Immunoblotting
- Isoenzymes/metabolism
- Kidney Tubules, Distal/cytology
- Kidney Tubules, Distal/drug effects
- Kidney Tubules, Distal/metabolism
- Promoter Regions, Genetic/genetics
- Protein Binding/drug effects
- Protein Kinase C/metabolism
- Protein Serine-Threonine Kinases
- Protein Transport/drug effects
- RNA, Messenger/drug effects
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptor, Transforming Growth Factor-beta Type II
- Receptors, Transforming Growth Factor beta/genetics
- Receptors, Transforming Growth Factor beta/metabolism
- Recombinant Fusion Proteins/drug effects
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Transcription Factor AP-1/metabolism
- Transcription Factors/metabolism
Collapse
Affiliation(s)
- Lea-Yea Chuang
- Department of Biochemistry, Kaohsiung Medical University, Tainan, Taiwan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Kelpe CL, Moore PC, Parazzoli SD, Wicksteed B, Rhodes CJ, Poitout V. Palmitate inhibition of insulin gene expression is mediated at the transcriptional level via ceramide synthesis. J Biol Chem 2003; 278:30015-21. [PMID: 12771145 DOI: 10.1074/jbc.m302548200] [Citation(s) in RCA: 194] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Chronic exposure to elevated levels of fatty acids impairs pancreatic beta cell function, a phenomenon thought to contribute to the progressive deterioration of insulin secretion in type 2 diabetes. We have previously demonstrated that prolonged exposure of isolated islets to elevated levels of palmitate inhibits preproinsulin mRNA levels in the presence of high glucose concentrations. However, whether this occurs via transcriptional or post-transcriptional mechanisms has not been determined. In addition, the nature of the lipid metabolites involved in palmitate inhibition of insulin gene expression is unknown. In this study, we show that palmitate decreases glucose-stimulated preproinsulin mRNA levels in isolated rat islets, an effect that is not mediated by changes in preproinsulin mRNA stability, but is associated with inhibition of glucose-stimulated insulin promoter activity. Prolonged culture of isolated islets with palmitate is associated with increased levels of intracellular ceramide. Palmitate-induced ceramide generation is prevented by inhibitors of de novo ceramide synthesis. Further, exogenous ceramide inhibits insulin mRNA levels, whereas blockade of de novo ceramide synthesis prevents palmitate inhibition of insulin gene expression. We conclude that prolonged exposure to elevated levels of palmitate affects glucose-stimulated insulin gene expression via transcriptional mechanisms and ceramide synthesis.
Collapse
Affiliation(s)
- Cynthia L Kelpe
- Pacific Northwest Research Institute, Seattle, Washington 98122, USA
| | | | | | | | | | | |
Collapse
|
29
|
Gao Z, Young RA, Trucco MM, Greene SR, Hewlett EL, Matschinsky FM, Wolf BA. Protein kinase A translocation and insulin secretion in pancreatic beta-cells: studies with adenylate cyclase toxin from Bordetella pertussis. Biochem J 2002; 368:397-404. [PMID: 12180908 PMCID: PMC1223000 DOI: 10.1042/bj20020999] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2002] [Accepted: 08/15/2002] [Indexed: 11/17/2022]
Abstract
Activation of protein kinase A (cAMP-dependent protein kinase; PKA) triggers insulin secretion in the beta-cell. Adenylate cyclase toxin (ACT), a bacterial exotoxin with adenylate cyclase activity, and forskolin, an activator of adenylate cyclase, both dose-dependently increased insulin secretion in the presence, but not the absence, of glucose in insulin-secreting betaTC3 cells. The stimulation of cAMP release by either agent was dose-dependent but glucose-independent. Omission of extracellular Ca(2+) totally abolished the effects of ACT on insulin secretion and cytosolic cAMP accumulation. ACT and forskolin caused rapid and dramatic increases in cytosolic Ca(2+), which were blocked by nifedipine and the omission of extracellular Ca(2+). Omission of glucose completely blocked the effects of forskolin and partially blocked the effects of ACT on cytosolic Ca(2+). PKA alpha, beta and gamma catalytic subunits (Calpha, Cbeta and Cgamma respectively) were identified in betaTC6 cells by confocal microscopy. Glucose and glucagon-like polypeptide-1 (GLP-1) caused translocation of Calpha to the nucleus and of Cbeta to the plasma membrane and the nucleus, but did not affect the distribution of Cgamma. In conclusion, glucose and GLP-1 amplify insulin secretion via cAMP production and PKAbeta activation.
Collapse
Affiliation(s)
- Zhiyong Gao
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia and University of Pennsylvania School of Medicine, 5135 Main Building, 34th Street and Civic Center Blvd, Philadelphia, PA 19104-4399, U.S.A
| | | | | | | | | | | | | |
Collapse
|
30
|
Pinton P, Tsuboi T, Ainscow EK, Pozzan T, Rizzuto R, Rutter GA. Dynamics of glucose-induced membrane recruitment of protein kinase C beta II in living pancreatic islet beta-cells. J Biol Chem 2002; 277:37702-10. [PMID: 12149258 DOI: 10.1074/jbc.m204478200] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanisms by which glucose may affect protein kinase C (PKC) activity in the pancreatic islet beta-cell are presently unclear. By developing adenovirally expressed chimeras encoding fusion proteins between green fluorescent protein and conventional (betaII), novel (delta), or atypical (zeta) PKCs, we show that glucose selectively alters the subcellular localization of these enzymes dynamically in primary islet and MIN6 beta-cells. Examined by laser scanning confocal or total internal reflection fluorescence microscopy, elevated glucose concentrations induced oscillatory translocations of PKCbetaII to spatially confined regions of the plasma membrane. Suggesting that increases in free cytosolic Ca(2+) concentrations ([Ca(2+)](c)) were primarily responsible, prevention of [Ca(2+)](c) increases with EGTA or diazoxide completely eliminated membrane recruitment, whereas elevation of cytosolic [Ca(2+)](c) with KCl or tolbutamide was highly effective in redistributing PKCbetaII both to the plasma membrane and to the surface of dense core secretory vesicles. By contrast, the distribution of PKCdelta.EGFP, which binds diacylglycerol but not Ca(2+), was unaffected by glucose. Measurement of [Ca(2+)](c) immediately beneath the plasma membrane with a ratiometric "pericam," fused to synaptic vesicle-associated protein-25, revealed that depolarization induced significantly larger increases in [Ca(2+)](c) in this domain. These data demonstrate that nutrient stimulation of beta-cells causes spatially and temporally complex changes in the subcellular localization of PKCbetaII, possibly resulting from the generation of Ca(2+) microdomains. Localized changes in PKCbetaII activity may thus have a role in the spatial control of insulin exocytosis.
Collapse
Affiliation(s)
- Paolo Pinton
- Henry Wellcome Signalling Laboratories and the Department of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom
| | | | | | | | | | | |
Collapse
|
31
|
Furukawa N, Shirotani T, Nakamaru K, Matsumoto K, Shichiri M, Araki E. Regulation of the insulin gene transcription by glucose. Endocr J 2002; 49:121-30. [PMID: 12081229 DOI: 10.1507/endocrj.49.121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Affiliation(s)
- Noboru Furukawa
- Department of Metabolic Medicine, Kumamoto University School of Medicine, Honjo, Japan
| | | | | | | | | | | |
Collapse
|
32
|
Buteau J, Foisy S, Rhodes CJ, Carpenter L, Biden TJ, Prentki M. Protein kinase Czeta activation mediates glucagon-like peptide-1-induced pancreatic beta-cell proliferation. Diabetes 2001; 50:2237-43. [PMID: 11574404 DOI: 10.2337/diabetes.50.10.2237] [Citation(s) in RCA: 182] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Glucagon-like peptide-1 (GLP-1), an insulinotropic and glucoincretin hormone, is a potentially important therapeutic agent in the treatment of diabetes. We previously provided evidence that GLP-1 induces pancreatic beta-cell growth nonadditively with glucose in a phosphatidylinositol-3 kinase (PI-3K)-dependent manner. In the present study, we investigated the downstream effectors of PI-3K to determine the precise signal transduction pathways that mediate the action of GLP-1 on beta-cell proliferation. GLP-1 increased extracellular signal-related kinase 1/2, p38 mitogen-activated protein kinase (MAPK), and protein kinase B activities nonadditively with glucose in pancreatic beta(INS 832/13) cells. GLP-1 also caused nuclear translocation of the atypical protein kinase C (aPKC) zeta isoform in INS as well as in dissociated normal rat beta-cells as shown by immunolocalization and Western immunoblotting analysis. Tritiated thymidine incorporation measurements showed that the p38 MAPK inhibitor SB203580 suppressed GLP-1-induced beta-cell proliferation. Further investigation was performed using isoform-specific pseudosubstrates of classical (alpha, beta, and gamma) or zeta aPKC isoforms. The PKCzeta pseudosubstrate suppressed the proliferative action of GLP-1, whereas the inhibitor of classical PKC isoforms had no effect. Overexpression of a kinase-dead PKCzeta acting as a dominant negative protein suppressed GLP-1-induced proliferation. In addition, ectopic expression of a constitutively active PKCzeta mutant stimulated tritiated thymidine incorporation to the same extent as GLP-1, and the glucoincretin had no growth-promoting action under this condition. The data indicate that GLP-1-induced activation of PKCzeta is implicated in the beta-cell proliferative signal of the insulinotropic hormone. The results are consistent with a model in which GLP-1-induced PI-3K activation results in PKCzeta translocation to the nucleus, which may play a role in the pleiotropic effects (DNA synthesis, metabolic enzymes, and insulin gene expression) of the glucoincretin.
Collapse
Affiliation(s)
- J Buteau
- Molecular Nutrition Unit, Department of Nutrition, University of Montreal, the Centre de Recherche du CHUM and Institut du Cancer, Montreal, Quebec, Canada
| | | | | | | | | | | |
Collapse
|
33
|
Abstract
Pancreatic duodenal homeobox-1 (PDX-1) is a homeodomain protein that plays an important role in the development of the pancreas and in maintaining the identity and function of the islets of Langerhans. It also regulates the expression of the insulin gene in response to changes in glucose and insulin concentrations. Glucose and insulin regulate PDX-1 by way of a signaling pathway involving phosphatidylinositol 3-kinase (PI 3-kinase) and SAPK2/p38. Activation of this pathway leads to phosphorylation of PDX-1 and its movement into the nucleus. To investigate the intracellular trafficking of PDX-1, immunocytochemistry was used to localize PDX-1 in the human beta-cell line NesPDX-1, in which PDX-1 is overexpressed, and in MIN6 beta-cells. In low-glucose conditions, PDX-1 localized predominantly to the nuclear periphery, with some staining in the cytoplasm. After stimulation with glucose, PDX-1 was present in the nucleoplasm. The translocation of PDX-1 to the nucleoplasm was complete within 15 min and occurred in 5-10 mmol/l glucose. Insulin and sodium arsenite, an activator of the stress-activated pathway, also stimulated PDX-1 movement from the nuclear periphery to the nucleoplasm. When cells were transferred between high glucose- and low glucose-containing medium, PDX-1 rapidly shuttled between the nuclear periphery and the nucleoplasm. Glucose- and insulin-stimulated translocation of PDX-1 to the nucleoplasm was inhibited by wortmannin and SB 203580, indicating that a pathway involving PI 3-kinase and SAPK2/p38 was involved; translocation was unaffected by PD 098959 and rapamycin, suggesting that neither mitogen-activated protein kinase nor p70(s6k) were involved. Arsenite-stimulated import of PDX-1 into the nucleus was inhibited by SB 203580 but not by wortmannin. Export from the nucleoplasm to the nuclear periphery was inhibited by calyculin A and okadaic acid, suggesting that dephosphorylation of PDX-1 was involved. These results demonstrated that PDX-1 shuttles between the nuclear periphery and nucleoplasm in response to changes in glucose and insulin concentrations and that these events are dependent on PI 3-kinase, SAPK2/p38, and a nuclear phosphatase(s).
Collapse
Affiliation(s)
- L J Elrick
- Department of Molecular and Cell Biology, University of Aberdeen, Institute of Medical Sciences, Aberdeen, UK
| | | |
Collapse
|
34
|
Hua H, Goldberg HJ, Fantus IG, Whiteside CI. High glucose-enhanced mesangial cell extracellular signal-regulated protein kinase activation and alpha1(IV) collagen expression in response to endothelin-1: role of specific protein kinase C isozymes. Diabetes 2001; 50:2376-83. [PMID: 11574422 DOI: 10.2337/diabetes.50.10.2376] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
High glucose (HG) stimulates glomerular mesangial cell (MC) expression of extracellular matrix, a process involving protein kinase C (PKC) isozymes and enhanced signaling by autocrine peptides such as endothelin-1 (ET-1). The purpose of this study was to identify the specific PKC isozymes mediating the effects of HG on MC extracellular signal-regulated protein kinase (ERK1/2) signaling and alpha1(IV) collagen expression in response to ET-1. HG (30 mmol/l for 72 h) enhanced ET-1-stimulated alpha1(IV) collagen mRNA expression from 1.2 +/- 0.1-fold to 1.9 +/- 0.2-fold (P < 0.05 vs. normal glucose [NG] + ET-1), and the effect was significantly reduced by Calphostin C or the MEK (mitogen-activated protein kinase kinase) inhibitor PD98059. In transiently transfected MCs, dominant-negative (DN)-PKC-delta, -epsilon, or -zeta inhibited ET-1 activation of ERK1/2. Likewise, downstream of ERK1/2, ET-1 stimulated Elk-1-driven GAL4 luciferase activity to 11 +/- 1-fold (P < 0.002 vs. NG + ET-1) in HG, and DN-PKC-delta, -epsilon, or -zeta attenuated this response to NG levels. HG enhanced ET-1-stimulated intracellular alpha1(IV) collagen protein expression, assessed by confocal immunofluorescence imaging, showed that individual DN-PKC-delta, -epsilon, -zeta, as well as DN-PKC-alpha and -beta, attenuated the response. Thus, HG-enhanced ET-1 stimulation of alpha1(IV) collagen expression requires PKC-delta, -epsilon, and -zeta to act through an ERK1/2-dependent pathway and via PKC-alpha and -beta, which are independent of ERK1/2.
Collapse
Affiliation(s)
- H Hua
- Institute of Medical Science, the University Health Network. Department of Medicine, University of Toronto, Toronto, Canada
| | | | | | | |
Collapse
|
35
|
Abstract
Aberrant gene expression is a fundamental cause of many disease-associated pathophysiologies. The pharmacological modulation of transcription factor activity therefore represents an attractive therapeutic approach to such disorders. With the exception of nuclear receptors, which are the direct targets of pharmaceuticals, other known classes of transcription factors are largely regulated indirectly by drugs that impact upon those signal transduction cascades that alter transcription factor phosphorylation and dephosphorylation and/or nuclear import. However, recent advances in drug discovery technologies now enable high-throughput screens that can identify molecules that act directly at the level of transcription factor complexes.
Collapse
Affiliation(s)
- J G Emery
- Dept of Musculoskeletal Diseases, GlaxoSmithKline Pharmaceuticals, UW2109, King of Prussia, PA 19406-0939, USA
| | | | | |
Collapse
|
36
|
|
37
|
Yamakawa K, Yamasaki H, Ozaki M, Yamauchi MD, Fujita N, Abe T, Miyazoe H, Sera Y, Uotani S, Kawasaki E, Takino H, Yamaguchi Y, Eguchi K. Hepatocyte nuclear factor-1alpha inhibits insulin promoter factor 1-dependent transactivation of the human insulin gene. Endocr Res 2001; 27:63-74. [PMID: 11428722 DOI: 10.1081/erc-100107170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
To investigate the regulational interaction of hepatocyte nuclear factor-1alpha (HNF-1alpha) and insulin promoter factor 1 (IPF1) on insulin gene expression, either or both of the expression vectors carrying each transcription factor were transiently transfected into HeLa cells, RINm5F cells and MIN6 cells together with the luciferase reporter construct driven by a human preproinsulin gene promoter (-1998 to +237) designated as, pINS-1998/luc. IPF1-transfection into HeLa cells strongly stimulated the luciferase activity to 725 fold that of the basal level. In contrast, HNF-1alpha-transfection resulted in only a 6.7 fold increase. In co-transfection experiments, increasing the amount of HNF-1alpha resulted in an 84.5% and 74.4% decrease in IPF1-stimulated luciferase activity in HeLa and RINm5F cells, respectively. Deletion constructs designated as pINS-248/luc, pINS-213/luc and pINS-185/luc were transfected into RINm5F cells to determine the role of the A3 element and its 5' flanking sequence in the inhibitory effect of HNF-1alpha. The results showed that the inhibiting effects of HNF-1alpha with pINS-213/luc and pINS-185/luc were significantly smaller than those with both pINS-1998/luc and pINS-248/luc. Transfection into MN6 cells with pINS-1998/luc in the absence of IPF1 resulted in constitutional transactivation of the insulin gene, and this transactivation was abolished by the co-transfection with HNF-1alpha. The present data indicate that IPF1 rather than HNF-1alpha predominantly transactivates the insulin gene, and that HNF-1alpha inhibits IPF1-dependent insulin gene transactivation mediated through the 5' flanking sequence of the A3 element. It is suggested that HNF-1alpha may be involved in insulin gene expression as a negative regulator.
Collapse
Affiliation(s)
- K Yamakawa
- First Department of Internal Medicine, Nagasaki University School of Medicine, Sakamoto, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
38
|
Yoshizato K, Shirotani T, Furukawa N, Taguchi T, Motoshima H, Toyonaga T, Hirashima Y, Kawashima J, Ebina Y, Shichiri M, Araki E. Identification of a cis-acting element and a novel trans-acting factor of the human insulin receptor gene in HepG2 and rat liver cells. Biochem Biophys Res Commun 2001; 280:428-34. [PMID: 11162534 DOI: 10.1006/bbrc.2000.4140] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The liver is a major target organ of insulin and is important for glucose homeostasis. We analyzed the tissue specific regulation of the insulin receptor gene in the liver by studying the cis-acting element and trans-acting factor of the human insulin receptor gene in human hepatoma cell line, HepG2 cells. In the chloramphenicol acetyl transferase (CAT) assay with chimeric plasmids containing various deletions and insertions of the human insulin receptor promoter/CAT gene, a HepG2 cell specific cis-acting element was identified between nt -592 to -577 of the promoter. In electrophoretic mobility shift assay and UV cross-link analysis, a 35-kDa nuclear protein that bound to 5'-TCCCTCCC-3' (nt -588 to -581) sequence was identified in HepG2 cells as well as in rat hepatocytes. This nuclear protein, designated as hepatocyte-specific transcription factor of the insulin receptor gene (HTFIR), might play an important role in tissue-specific expression of the insulin receptor gene in the liver.
Collapse
Affiliation(s)
- K Yoshizato
- Department of Metabolic Medicine, Kumamoto University School of Medicine, Kumamoto, Japan
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
39
|
Hussain MA, Habener JF. Glucagon-like peptide 1 increases glucose-dependent activity of the homeoprotein IDX-1 transactivating domain in pancreatic beta-cells. Biochem Biophys Res Commun 2000; 274:616-9. [PMID: 10924326 DOI: 10.1006/bbrc.2000.3198] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Both glucose and glucagon-like peptide 1 (GLP-1) stimulate insulin gene transcription in endocrine pancreatic beta-cells within the islets of Langerhans. The effects of glucose are mediated by the homeodomain transcription factor islet duodenum homeobox -1 (IDX-1) that binds to two adenine thymidine-rich (A1 and A2/3) motifs within the rat insulin promoter. Glucose stimulates the activity of the transactivation domain of IDX-1 that lies within the first 80 amino acids of the IDX-1 protein. The effects of GLP-1 on insulin gene expression are primarily conferred by the cAMP responsive element (CRE) within the insulin promoter. GLP-1 stimulates glucose-dependent insulin release from beta-cells. We hypothesize that GLP-1 may augment the effects of glucose on insulin gene transcription. Here we show that GLP-1 stimulates insulin gene transcription independent of the CRE and is glucose-dependent. Furthermore, we show that GLP-1 stimulates the transactivational activity of IDX-1.
Collapse
Affiliation(s)
- M A Hussain
- Laboratory of Molecular Endocrinology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | | |
Collapse
|