1
|
Cleveland KH, Schnellmann RG. The β 2-adrenergic receptor agonist formoterol restores mitochondrial homeostasis in glucose-induced renal proximal tubule injury through separate integrated pathways. Biochem Pharmacol 2023; 209:115436. [PMID: 36720358 DOI: 10.1016/j.bcp.2023.115436] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 01/19/2023] [Accepted: 01/23/2023] [Indexed: 01/31/2023]
Abstract
Mitochondrial dysfunction drives the development and progression of diabetic kidney disease (DKD). Previously, we discovered that the β2-adrenergic receptor (AR) agonist formoterol regulates mitochondrial dynamics in the hyperglycemic renal proximal tubule. The goal of this study was to identify signaling mechanisms through which formoterol restores the mitochondrial fission/fusion proteins Drp1 and Mfn1. Using primary renal proximal tubule cells (RPTC), the effect of chronic high glucose on RhoA/ROCK1/Drp1 and Raf/MEK1/2/ERK1/2/Mfn1 signaling was determined. In glucose-treated RPTC, RhoA became hyperactive, leading to ROCK1-induced activation of Drp1. Treatment with formoterol and/or pharmacological inhibitors targeting RhoA, ROCK1 and Drp1 blocked RhoA and Drp1 hyperactivity. Inhibiting this pathway also restored maximal mitochondrial respiration. By preventing Gβγ signaling with gallein, we determined that formoterol signals through the Gβγ subunit of the β2-AR to restore RhoA and Drp1. Furthermore, formoterol restored this pathway by blocking binding of RhoA with the guanine nucleotide exchange factor p114RhoGEF. Formoterol also restored the mitochondrial fusion protein Mfn1 through a second Gβγ-dependent mechanism composed of Raf/MEK1/2/ERK1/2/Mfn1. Glucose-treated RPTC exhibited decreased Mfn1 activity, which was restored with formoterol. Pharmacological inhibition of Gβγ, Raf and MEK1/2 also restored Mfn1 activity. We demonstrate that glucose promotes the interaction between RhoA and p114RhoGEF, leading to increased RhoA and ROCK1-mediated activation of Drp1, and decreases Mfn1 activity through Raf/MEK1/2/ERK1/2. Formoterol restores these pathways and mitochondrial function in response to elevated glucose by activating separate yet integrative pathways that promote mitochondrial biogenesis, decreased fission and increased fusion in RPTC, further supporting its potential as a therapeutic for DKD.
Collapse
Affiliation(s)
- Kristan H Cleveland
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ, United States
| | - Rick G Schnellmann
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ, United States; Southern Arizona VA Health Care System, Tucson, AZ, United States; Southwest Environmental Health Science Center, University of Arizona, Tucson, AZ, United States.
| |
Collapse
|
2
|
Ikushima YM, Awazawa M, Kobayashi N, Osonoi S, Takemiya S, Kobayashi H, Suwanai H, Morimoto Y, Soeda K, Adachi J, Muratani M, Charron J, Mizukami H, Takahashi N, Ueki K. MEK/ERK Signaling in β-Cells Bifunctionally Regulates β-Cell Mass and Glucose-Stimulated Insulin Secretion Response to Maintain Glucose Homeostasis. Diabetes 2021; 70:1519-1535. [PMID: 33906910 DOI: 10.2337/db20-1295] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 04/23/2021] [Indexed: 11/13/2022]
Abstract
In diabetic pathology, insufficiency in β-cell mass, unable to meet peripheral insulin demand, and functional defects of individual β-cells in production of insulin are often concurrently observed, collectively causing hyperglycemia. Here we show that the phosphorylation of ERK1/2 is significantly decreased in the islets of db/db mice as well as in those of a cohort of subjects with type 2 diabetes. In mice with abrogation of ERK signaling in pancreatic β-cells through deletion of Mek1 and Mek2, glucose intolerance aggravates under high-fat diet-feeding conditions due to insufficient insulin production with lower β-cell proliferation and reduced β-cell mass, while in individual β-cells dampening of the number of insulin exocytosis events is observed, with the molecules involved in insulin exocytosis being less phosphorylated. These data reveal bifunctional roles for MEK/ERK signaling in β-cells for glucose homeostasis, i.e., in regulating β-cell mass as well as in controlling insulin exocytosis in individual β-cells, thus providing not only a novel perspective for the understanding of diabetes pathophysiology but also a potential clue for new drug development for diabetes treatment.
Collapse
Affiliation(s)
- Yoshiko Matsumoto Ikushima
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Motoharu Awazawa
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Naoki Kobayashi
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Sho Osonoi
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Seiichi Takemiya
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Hiroshi Kobayashi
- Department of Stem Cell Biology, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Hirotsugu Suwanai
- Department of Diabetes, Metabolism and Endocrinology, Tokyo Medical University, Tokyo, Japan
| | - Yuichi Morimoto
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
- International Research Center for Neurointelligence (WPI-IRCN), University of Tokyo Institutes for Advanced Study (UTIAS), The University of Tokyo, Tokyo, Japan
| | - Kotaro Soeda
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Jun Adachi
- Laboratory of Proteome Research, Laboratory of Proteomics for Drug Discovery, Center for Drug Design Research, National Institutes of Biomedical Innovation, Health and Nutrition, Osaka, Japan
| | - Masafumi Muratani
- Department of Genome Biology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Jean Charron
- Centre de Recherche sur le Cancer de l'Université Laval, L'Hôtel-Dieu de Québec, Quebec City, Quebec, Canada
| | - Hiroki Mizukami
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Noriko Takahashi
- Department of Physiology, Kitasato University School of Medicine, Sagamihara, Japan
| | - Kohjiro Ueki
- Department of Molecular Diabetic Medicine, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
- Department of Molecular Diabetology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| |
Collapse
|
3
|
He XQ, Wang N, Zhao JJ, Wang D, Wang CJ, Xie L, Zheng HY, Shi SZ, He J, Zhou J, Xin HB, Deng KY. Specific deletion of CDC42 in pancreatic β cells attenuates glucose-induced insulin expression and secretion in mice. Mol Cell Endocrinol 2020; 518:111004. [PMID: 32871224 DOI: 10.1016/j.mce.2020.111004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 08/15/2020] [Accepted: 08/20/2020] [Indexed: 12/22/2022]
Abstract
Insulin is a key hormone for maintaining glucose homeostasis in organisms. In general, deficiency of insulin synthesis and secretion results in type I diabetes, whereas insulin resistance leads to type 2 diabetes. Cell division cycle 42 (CDC42), a member of Rho GTPases family, has been shown as an essential regulator in the second phase of glucose-induced insulin secretion in pancreatic islets β cells in vitro. However, the effect of CDC42 on insulin expression has not been explored. Here we reported that the glucose-induced insulin expression and secretion were significantly inhibited in mice lacking CDC42 gene in pancreatic β cells (Rip-CDC42cKO) in vivo and in vitro. Deletion of CDC42 gene in pancreatic β cells did not affect survival or reproduction in mice. However, the Rip-CDC42cKO mice showed the systemic glucose intolerance and the decrease of glucose-induced insulin secretion without apparent alterations of peripheral tissues insulin sensitivity and the morphology of islets. Furthermore, we demonstrated that deletion of CDC42 gene in pancreatic β cells significantly attenuated the insulin expression through inhibiting the ERK1/2-NeuroD1 signaling pathway. Taken together, our study presents novel evidence that CDC42 is an important modulator in glucose-induced insulin expression as well as insulin secretion in pancreatic β cells.
Collapse
Affiliation(s)
- Xiang-Qin He
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China; College of Life Science, Nanchang University, Nanchang, Jiangxi, China
| | - Ning Wang
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China
| | - Juan-Juan Zhao
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China
| | - Dan Wang
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China; Institute for Metabolic and Neuropsychiatric Disorders, Binzhou Medical University, Binzhou, Shandong, China
| | - Cai-Ji Wang
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China
| | - Lin Xie
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China; College of Life Science, Nanchang University, Nanchang, Jiangxi, China
| | - Huai-Yu Zheng
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China
| | - Shui-Zhen Shi
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China
| | - Jing He
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China
| | - Jiliang Zhou
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Hong-Bo Xin
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China; College of Life Science, Nanchang University, Nanchang, Jiangxi, China.
| | - Ke-Yu Deng
- The National Engineering Research Center for Bioengineering Drugs and the Technologies, Institute of Translational Medicine, Nanchang University, Nanchang, Jiangxi, China; College of Life Science, Nanchang University, Nanchang, Jiangxi, China.
| |
Collapse
|
4
|
Kalwat MA, Huang Z, Binns DD, McGlynn K, Cobb MH. α 2-Adrenergic Disruption of β Cell BDNF-TrkB Receptor Tyrosine Kinase Signaling. Front Cell Dev Biol 2020; 8:576396. [PMID: 33178692 PMCID: PMC7593622 DOI: 10.3389/fcell.2020.576396] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 09/14/2020] [Indexed: 12/11/2022] Open
Abstract
Adrenergic signaling is a well-known input into pancreatic islet function. Specifically, the insulin-secreting islet β cell expresses the Gi/o-linked α2-adrenergic receptor, which upon activation suppresses insulin secretion. The use of the adrenergic agonist epinephrine at micromolar doses may have supraphysiological effects. We found that pretreating β cells with micromolar concentrations of epinephrine differentially inhibited activation of receptor tyrosine kinases. We chose TrkB as an example because of its relative sensitivity to the effects of epinephrine and due to its potential regulatory role in the β cell. Our characterization of brain-derived neurotrophic factor (BDNF)-TrkB signaling in MIN6 β cells showed that TrkB is activated by BDNF as expected, leading to canonical TrkB autophosphorylation and subsequent downstream signaling, as well as chronic effects on β cell growth. Micromolar, but not nanomolar, concentrations of epinephrine blocked BDNF-induced TrkB autophosphorylation and downstream mitogen-activated protein kinase pathway activation, suggesting an inhibitory phenomenon at the receptor level. We determined epinephrine-mediated inhibition of TrkB activation to be Gi/o-dependent using pertussis toxin, arguing against an off-target effect of high-dose epinephrine. Published data suggested that inhibition of potassium channels or phosphoinositide-3-kinase signaling may abrogate the negative effects of epinephrine; however, these did not rescue TrkB signaling in our experiments. Taken together, these results show that (1) TrkB kinase signaling occurs in β cells and (2) use of epinephrine in studies of insulin secretion requires careful consideration of concentration-dependent effects. BDNF-TrkB signaling in β cells may underlie pro-survival or growth signaling and warrants further study.
Collapse
Affiliation(s)
- Michael A. Kalwat
- Department of Pharmacology, UT Southwestern Medical Center, Dallas, TX, United States
| | | | | | | | | |
Collapse
|
5
|
Toubal S, Oiry C, Bayle M, Cros G, Neasta J. Urolithin C increases glucose-induced ERK activation which contributes to insulin secretion. Fundam Clin Pharmacol 2020; 34:571-580. [PMID: 32083757 DOI: 10.1111/fcp.12551] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 02/14/2020] [Accepted: 02/20/2020] [Indexed: 12/31/2022]
Abstract
Polyphenols exert pharmacological actions through protein-mediated mechanisms and by modulating intracellular signalling pathways. We recently showed that a gut-microbial metabolite of ellagic acid named urolithin C is a glucose-dependent activator of insulin secretion acting by facilitating L-type Ca2+ channel opening and Ca2+ influx into pancreatic β-cells. However, it is still unknown whether urolithin C regulates key intracellular signalling proteins in β-cells. Here, we report that urolithin C enhanced glucose-induced extracellular signal-regulated kinases 1/2 (ERK1/2) activation as shown by higher phosphorylation levels in INS-1 β-cells. Interestingly, inhibition of ERK1/2 with two structurally distinct inhibitors led to a reduction in urolithin C effect on insulin secretion. Finally, we provide data to suggest that urolithin C-mediated ERK1/2 phosphorylation involved insulin signalling in INS-1 cells. Together, these data indicate that the pharmacological action of urolithin C on insulin secretion relies, in part, on its capacity to enhance glucose-induced ERK1/2 activation. Therefore, our study extends our understanding of the pharmacological action of urolithin C in β-cells. More generally, our findings revealed that urolithin C modulated the activation of key multifunctional intracellular signalling kinases which participate in the regulation of numerous biological processes.
Collapse
Affiliation(s)
- Slimane Toubal
- IBMM, Université de Montpellier, CNRS, ENSCM, Montpellier, France
| | - Catherine Oiry
- IBMM, Université de Montpellier, CNRS, ENSCM, Montpellier, France
| | - Morgane Bayle
- IBMM, Université de Montpellier, CNRS, ENSCM, Montpellier, France
| | - Gérard Cros
- IBMM, Université de Montpellier, CNRS, ENSCM, Montpellier, France
| | - Jérémie Neasta
- IBMM, Université de Montpellier, CNRS, ENSCM, Montpellier, France
| |
Collapse
|
6
|
cAMP-PKA dependent ERK1/2 activation is necessary for vanillic acid potentiated glucose-stimulated insulin secretion in pancreatic β-cells. J Funct Foods 2019. [DOI: 10.1016/j.jff.2019.02.047] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
|
7
|
Michael ES, Covic L, Kuliopulos A. Trace amine-associated receptor 1 (TAAR1) promotes anti-diabetic signaling in insulin-secreting cells. J Biol Chem 2019; 294:4401-4411. [PMID: 30670596 DOI: 10.1074/jbc.ra118.005464] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 01/16/2019] [Indexed: 12/25/2022] Open
Abstract
Pancreatic β-cell failure in type 2 diabetes mellitus is a serious challenge that results in an inability of the pancreas to produce sufficient insulin to properly regulate blood glucose levels. Trace amine-associated receptor 1 (TAAR1) is a G protein-coupled receptor expressed by β-cells that has recently been proposed as a potential target for improving glycemic control and suppressing binge eating behaviors. We discovered that TAAR1 is coupled to Gαs-signaling pathways in insulin-secreting β-cells to cause protein kinase A (PKA)/exchange protein activated by cAMP (Epac)-dependent release of insulin, activation of RAF proto-oncogene, Ser/Thr kinase (Raf)-mitogen-activated protein kinase (MAPK) signaling, induction of cAMP response element-binding protein (CREB)-insulin receptor substrate 2 (Irs-2), and increased β-cell proliferation. Interestingly, TAAR1 triggered cAMP-mediated calcium influx and release from internal stores, both of which were required for activation of a MAPK cascade utilizing calmodulin-dependent protein kinase II (CaMKII), Raf, and MAPK/ERK kinase 1/2 (MEK1/2). Together, these data identify TAAR1/Gαs-mediated signaling pathways that promote insulin secretion, improved β-cell function and proliferation, and highlight TAAR1 as a promising new target for improving β-cell health in type 2 diabetes mellitus.
Collapse
Affiliation(s)
- Emily S Michael
- From the Center for Hemostasis and Thrombosis Research, Tufts Medical Center, Department of Medicine, Tufts University School of Graduate Biomedical Sciences/Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Lidija Covic
- From the Center for Hemostasis and Thrombosis Research, Tufts Medical Center, Department of Medicine, Tufts University School of Graduate Biomedical Sciences/Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Athan Kuliopulos
- From the Center for Hemostasis and Thrombosis Research, Tufts Medical Center, Department of Medicine, Tufts University School of Graduate Biomedical Sciences/Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111
| |
Collapse
|
8
|
Ye R, Gordillo R, Shao M, Onodera T, Chen Z, Chen S, Lin X, SoRelle JA, Li X, Tang M, Keller MP, Kuliawat R, Attie AD, Gupta RK, Holland WL, Beutler B, Herz J, Scherer PE. Intracellular lipid metabolism impairs β cell compensation during diet-induced obesity. J Clin Invest 2018; 128:1178-1189. [PMID: 29457786 DOI: 10.1172/jci97702] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 01/09/2018] [Indexed: 12/16/2022] Open
Abstract
The compensatory proliferation of insulin-producing β cells is critical to maintaining glucose homeostasis at the early stage of type 2 diabetes. Failure of β cells to proliferate results in hyperglycemia and insulin dependence in patients. To understand the effect of the interplay between β cell compensation and lipid metabolism upon obesity and peripheral insulin resistance, we eliminated LDL receptor-related protein 1 (LRP1), a pleiotropic mediator of cholesterol, insulin, energy metabolism, and other cellular processes, in β cells. Upon high-fat diet exposure, LRP1 ablation significantly impaired insulin secretion and proliferation of β cells. The diminished insulin signaling was partly contributed to by the hypersensitivity to glucose-induced, Ca2+-dependent activation of Erk and the mTORC1 effector p85 S6K1. Surprisingly, in LRP1-deficient islets, lipotoxic sphingolipids were mitigated by improved lipid metabolism, mediated at least in part by the master transcriptional regulator PPARγ2. Acute overexpression of PPARγ2 in β cells impaired insulin signaling and insulin secretion. Elimination of Apbb2, a functional regulator of LRP1 cytoplasmic domain, also impaired β cell function in a similar fashion. In summary, our results uncover the double-edged effects of intracellular lipid metabolism on β cell function and viability in obesity and type 2 diabetes and highlight LRP1 as an essential regulator of these processes.
Collapse
Affiliation(s)
- Risheng Ye
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA.,Department of Medical Education, Texas Tech University Health Sciences Center Paul L. Foster School of Medicine, El Paso, Texas, USA
| | - Ruth Gordillo
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Mengle Shao
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Toshiharu Onodera
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Zhe Chen
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA.,Center for the Genetics of Host Defense, UTSW Medical Center, Dallas, Texas, USA
| | - Shiuhwei Chen
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Xiaoli Lin
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Jeffrey A SoRelle
- Center for the Genetics of Host Defense, UTSW Medical Center, Dallas, Texas, USA
| | - Xiaohong Li
- Center for the Genetics of Host Defense, UTSW Medical Center, Dallas, Texas, USA
| | - Miao Tang
- Center for the Genetics of Host Defense, UTSW Medical Center, Dallas, Texas, USA
| | - Mark P Keller
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, USA
| | - Regina Kuliawat
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, New York, USA
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, USA
| | - Rana K Gupta
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - William L Holland
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Bruce Beutler
- Center for the Genetics of Host Defense, UTSW Medical Center, Dallas, Texas, USA
| | - Joachim Herz
- Departments of Molecular Genetics, Neuroscience, Neurology and Neurotherapeutics, and Center for Translational Neurodegeneration Research, UTSW Medical Center, Dallas, Texas, USA.,Center for Neuroscience, Department of Neuroanatomy, Albert Ludwig University, Freiburg, Germany
| | - Philipp E Scherer
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| |
Collapse
|
9
|
Niu B, Su H, Xia XS, He Q, Xue YM, Yan XM. The role of interleukin-1β and extracellular signal-regulated kinase 1/2 in glucose-stimulated insulin secretion. Kaohsiung J Med Sci 2017; 33:224-228. [DOI: 10.1016/j.kjms.2017.02.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 01/28/2017] [Accepted: 02/13/2017] [Indexed: 01/17/2023] Open
|
10
|
Benthuysen JR, Carrano AC, Sander M. Advances in β cell replacement and regeneration strategies for treating diabetes. J Clin Invest 2016; 126:3651-3660. [PMID: 27694741 DOI: 10.1172/jci87439] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In the past decade, new approaches have been explored that are aimed at restoring functional β cell mass as a treatment strategy for diabetes. The two most intensely pursued strategies are β cell replacement through conversion of other cell types and β cell regeneration by enhancement of β cell replication. The approach closest to clinical implementation is the replacement of β cells with human pluripotent stem cell-derived (hPSC-derived) cells, which are currently under investigation in a clinical trial to assess their safety in humans. In addition, there has been success in reprogramming developmentally related cell types into β cells. Reprogramming approaches could find therapeutic applications by inducing β cell conversion in vivo or by reprogramming cells ex vivo followed by implantation. Finally, recent studies have revealed novel pharmacologic targets for stimulating β cell replication. Manipulating these targets or the pathways they regulate could be a strategy for promoting the expansion of residual β cells in diabetic patients. Here, we provide an overview of progress made toward β cell replacement and regeneration and discuss promises and challenges for clinical implementation of these strategies.
Collapse
|
11
|
Mezza T, Shirakawa J, Martinez R, Hu J, Giaccari A, Kulkarni RN. Nuclear Export of FoxO1 Is Associated with ERK Signaling in β-Cells Lacking Insulin Receptors. J Biol Chem 2016; 291:21485-21495. [PMID: 27535223 DOI: 10.1074/jbc.m116.735738] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 08/06/2016] [Indexed: 12/17/2022] Open
Abstract
The insulin/insulin-like growth factor (IGF) signaling pathway plays a critical role in the regulation of islet cell biology. However, the signaling pathway(s) utilized by insulin to directly modulate β-cells is unclear. To interrogate whether insulin exerts endocrine effects in regulating proteins in the insulin/IGF-1 signaling cascade in vivo in physiological states via the insulin receptor, we designed two experimental approaches: 1) glucose gavage and 2) hyperinsulinemic intravenous infusion, for studies in either β-cell specific insulin receptor knock-out (βIRKO) or control mice. Immunostaining of sections of pancreas (collected immediately after glucose gavage or insulin infusion) from controls showed significant increases in pAKT+, p-p70S6K+, and pERK+ β-cells and a significant decrease in % nuclear FoxO1+ β-cells compared with corresponding vehicle-treated groups. In contrast, in βIRKOs, we observed no significant changes in pAKT+ or p-p70S6K+ β-cells in either experiment; however, pERK+ β-cells were significantly increased, and an attenuated decrease in % nuclear FoxO1+ β cells was evident in response to glucose gavage or insulin infusion. Treatment of control and βIRKO β-cell lines with glucose or insulin showed significantly decreased % nuclear FoxO1+ β-cells suggesting direct effects. Furthermore, blocking MAPK signaling had virtually no effect on FoxO1 nuclear export in controls, in contrast to attenuated export in βIRKO β-cells. These data suggest insulin acts on β-cells in an endocrine manner in the normal situation; and that in β-cells lacking insulin receptors, insulin and glucose minimally activate the Akt pathway, while ERK phosphorylation and FoxO1 nuclear export occur independently of insulin signaling.
Collapse
Affiliation(s)
- Teresa Mezza
- From the Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Stem Cell Institute, Harvard Medical School, Boston, Massachusetts 02215 and.,Center for Endocrine and Metabolic Diseases, Policlinico Gemelli, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
| | - Jun Shirakawa
- From the Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Stem Cell Institute, Harvard Medical School, Boston, Massachusetts 02215 and
| | - Rachael Martinez
- From the Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Stem Cell Institute, Harvard Medical School, Boston, Massachusetts 02215 and
| | - Jiang Hu
- From the Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Stem Cell Institute, Harvard Medical School, Boston, Massachusetts 02215 and
| | - Andrea Giaccari
- Center for Endocrine and Metabolic Diseases, Policlinico Gemelli, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
| | - Rohit N Kulkarni
- From the Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Stem Cell Institute, Harvard Medical School, Boston, Massachusetts 02215 and
| |
Collapse
|
12
|
Niu B, Liu L, Su H, Xia X, He Q, Feng Y, Xue Y, Yan X. Role of extracellular signal‑regulated kinase 1/2 signal transduction pathway in insulin secretion by β‑TC6 cells. Mol Med Rep 2016; 13:4451-4. [PMID: 27035884 DOI: 10.3892/mmr.2016.5053] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Accepted: 02/29/2016] [Indexed: 11/06/2022] Open
Abstract
The present study aimed to investigate the role of the extracellular signal-regulated kinase (ERK)1/2 signal transduction pathway in glucose‑stimulated insulin secretion in β‑TC6 mouse pancreatic cells. Insulin production by β‑TC6 cells was stimulated with various concentrations of glucose, which was dose-dependently inhibited by mitogen‑activated protein kinase inhibitor PD98059, as indicated by a radioimmunoassay. Furthermore, glucose stimulation enhanced the phosphorylation of ERK1/2, which was dose-dependently inhibited by PD98059, as indicated by western blot analysis. These results indicated that the activation of the ERK1/2 signal transduction pathway may have an important role in glucose‑stimulated insulin secretion in β‑TC6 cells.
Collapse
Affiliation(s)
- Ben Niu
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, Yunnan 650500, P.R. China
| | - Lijuan Liu
- Department of Cadre Ward, WISCO General Hospital, Wuhan, Hubei 430080, P.R. China
| | - Heng Su
- Department of Endocrinology, The Affiliated Hospital of Kunming University of Science and Technology, The First People's Hospital of Yunnan, Kunming, Yunnan 650032, P.R. China
| | - Xueshan Xia
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, Yunnan 650500, P.R. China
| | - Qiu He
- Department of Endocrinology, The Affiliated Hospital of Kunming University of Science and Technology, The First People's Hospital of Yunnan, Kunming, Yunnan 650032, P.R. China
| | - Yue Feng
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, Yunnan 650500, P.R. China
| | - Yuanming Xue
- Department of Endocrinology, The Affiliated Hospital of Kunming University of Science and Technology, The First People's Hospital of Yunnan, Kunming, Yunnan 650032, P.R. China
| | - Xinming Yan
- Institute of Basic and Clinical Medicine, Center of Clinical Molecular Biology of Yunnan, The Affiliated Hospital of Kunming University of Science and Technology, The First People's Hospital of Yunnan, Kunming, Yunnan 650032, P.R. China
| |
Collapse
|
13
|
Pratt EPS, Salyer AE, Guerra ML, Hockerman GH. Ca2+ influx through L-type Ca2+ channels and Ca2+-induced Ca2+ release regulate cAMP accumulation and Epac1-dependent ERK 1/2 activation in INS-1 cells. Mol Cell Endocrinol 2016; 419:60-71. [PMID: 26435461 PMCID: PMC4684454 DOI: 10.1016/j.mce.2015.09.034] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 08/28/2015] [Accepted: 09/29/2015] [Indexed: 02/09/2023]
Abstract
We previously reported that INS-1 cells expressing the intracellular II-III loop of the L-type Ca(2+) channel Cav1.2 (Cav1.2/II-III cells) are deficient in Ca(2+)-induced Ca(2+) release (CICR). Here we show that glucose-stimulated ERK 1/2 phosphorylation (GSEP) is slowed and reduced in Cav1.2/II-III cells compared to INS-1 cells. This parallels a decrease in glucose-stimulated cAMP accumulation (GS-cAMP) in Cav1.2/II-III cells. Influx of Ca(2+) via L-type Ca(2+) channels and CICR play roles in both GSEP and GS-cAMP in INS-1 cells since both are inhibited by nicardipine or ryanodine. Further, the Epac1-selective inhibitor CE3F4 abolishes glucose-stimulated ERK activation in INS-1 cells, as measured using the FRET-based sensor EKAR. The non-selective Epac antagonist ESI-09 but not the Epac2-selective antagonist ESI-05 nor the PKA antagonist Rp-cAMPs inhibits GSEP in both INS-1 and Cav1.2/II-III cells. We conclude that L-type Ca(2+) channel-dependent cAMP accumulation, that's amplified by CICR, activates Epac1 and drives GSEP in INS-1 cells.
Collapse
Affiliation(s)
- Evan P S Pratt
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA; Purdue University Life Sciences Graduate Program, Purdue University, West Lafayette, IN, USA
| | - Amy E Salyer
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA
| | - Marcy L Guerra
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA
| | - Gregory H Hockerman
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA.
| |
Collapse
|
14
|
Wauson EM, Guerra ML, Dyachok J, McGlynn K, Giles J, Ross EM, Cobb MH. Differential Regulation of ERK1/2 and mTORC1 Through T1R1/T1R3 in MIN6 Cells. Mol Endocrinol 2015; 29:1114-22. [PMID: 26168033 DOI: 10.1210/me.2014-1181] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The MAPKs ERK1/2 respond to nutrients and other insulin secretagogues in pancreatic β-cells and mediate nutrient-dependent insulin gene transcription. Nutrients also stimulate the mechanistic target of rapamycin complex 1 (mTORC1) to regulate protein synthesis. We showed previously that activation of both ERK1/2 and mTORC1 in the MIN6 pancreatic β-cell-derived line by extracellular amino acids (AAs) is at least in part mediated by the heterodimeric T1R1/T1R3, a G protein-coupled receptor. We show here that AAs differentially activate these two signaling pathways in MIN6 cells. Pretreatment with pertussis toxin did not prevent the activation of either ERK1/2 or mTORC1 by AAs, indicating that G(I) is not central to either pathway. Although glucagon-like peptide 1, an agonist for a G(s-)coupled receptor, activated ERK1/2 well and mTORC1 to a small extent, AAs had no effect on cytosolic cAMP accumulation. Ca(2+) entry is required for ERK1/2 activation by AAs but is dispensable for AA activation of mTORC1. Pretreatment with UBO-QIC, a selective G(q) inhibitor, reduced the activation of ERK1/2 but had little effect on the activation of mTORC1 by AAs, suggesting a differential requirement for G(q). Inhibition of G(12/13) by the overexpression of the regulator of G protein signaling domain of p115 ρ-guanine nucleotide exchange factor had no effect on mTORC1 activation by AAs, suggesting that these G proteins are also not involved. We conclude that AAs regulate ERK1/2 and mTORC1 through distinct signaling pathways.
Collapse
Affiliation(s)
- Eric M Wauson
- Department of Pharmacology (E.M.W., M.L.G., J.D., K.M., E.M.R., M.H.C.) and the Green Center for Systems Biology (J.D., E.M.R.), University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041; and Department of Physiology and Pharmacology (E.M.W., J.G.), Des Moines University, Des Moines, Iowa 50312
| | - Marcy L Guerra
- Department of Pharmacology (E.M.W., M.L.G., J.D., K.M., E.M.R., M.H.C.) and the Green Center for Systems Biology (J.D., E.M.R.), University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041; and Department of Physiology and Pharmacology (E.M.W., J.G.), Des Moines University, Des Moines, Iowa 50312
| | - Julia Dyachok
- Department of Pharmacology (E.M.W., M.L.G., J.D., K.M., E.M.R., M.H.C.) and the Green Center for Systems Biology (J.D., E.M.R.), University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041; and Department of Physiology and Pharmacology (E.M.W., J.G.), Des Moines University, Des Moines, Iowa 50312
| | - Kathleen McGlynn
- Department of Pharmacology (E.M.W., M.L.G., J.D., K.M., E.M.R., M.H.C.) and the Green Center for Systems Biology (J.D., E.M.R.), University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041; and Department of Physiology and Pharmacology (E.M.W., J.G.), Des Moines University, Des Moines, Iowa 50312
| | - Jennifer Giles
- Department of Pharmacology (E.M.W., M.L.G., J.D., K.M., E.M.R., M.H.C.) and the Green Center for Systems Biology (J.D., E.M.R.), University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041; and Department of Physiology and Pharmacology (E.M.W., J.G.), Des Moines University, Des Moines, Iowa 50312
| | - Elliott M Ross
- Department of Pharmacology (E.M.W., M.L.G., J.D., K.M., E.M.R., M.H.C.) and the Green Center for Systems Biology (J.D., E.M.R.), University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041; and Department of Physiology and Pharmacology (E.M.W., J.G.), Des Moines University, Des Moines, Iowa 50312
| | - Melanie H Cobb
- Department of Pharmacology (E.M.W., M.L.G., J.D., K.M., E.M.R., M.H.C.) and the Green Center for Systems Biology (J.D., E.M.R.), University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041; and Department of Physiology and Pharmacology (E.M.W., J.G.), Des Moines University, Des Moines, Iowa 50312
| |
Collapse
|
15
|
Roy A, Dement AD, Cho KH, Kim JH. Assessing glucose uptake through the yeast hexose transporter 1 (Hxt1). PLoS One 2015; 10:e0121985. [PMID: 25816250 PMCID: PMC4376911 DOI: 10.1371/journal.pone.0121985] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 02/06/2015] [Indexed: 01/01/2023] Open
Abstract
The transport of glucose across the plasma membrane is mediated by members of the glucose transporter family. In this study, we investigated glucose uptake through the yeast hexose transporter 1 (Hxt1) by measuring incorporation of 2-NBDG, a non-metabolizable, fluorescent glucose analog, into the yeast Saccharomyces cerevisiae. We find that 2-NBDG is not incorporated into the hxt null strain lacking all glucose transporter genes and that this defect is rescued by expression of wild type Hxt1, but not of Hxt1 with mutations at the putative glucose-binding residues, inferred from the alignment of yeast and human glucose transporter sequences. Similarly, the growth defect of the hxt null strain on glucose is fully complemented by expression of wild type Hxt1, but not of the mutant Hxt1 proteins. Thus, 2-NBDG, like glucose, is likely to be transported into the yeast cells through the glucose transport system. Hxt1 is internalized and targeted to the vacuole for degradation in response to glucose starvation. Among the mutant Hxt1 proteins, Hxt1N370A and HXT1W473A are resistant to such degradation. Hxt1N370A, in particular, is able to neither uptake 2-NBDG nor restore the growth defect of the hxt null strain on glucose. These results demonstrate 2-NBDG as a fluorescent probe for glucose uptake in the yeast cells and identify N370 as a critical residue for the stability and function of Hxt1.
Collapse
Affiliation(s)
- Adhiraj Roy
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Science, 2300 Eye Street, NW, Washington, D. C., 20037, United States of America
| | - Angela D. Dement
- Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, 1015 Life Science Circle, Blacksburg, Virginia 24061, United States of America
| | - Kyu Hong Cho
- Department of Biology, Indiana State University, 200N 7th St, Terre Haute, Indiana 47809, United States of America
| | - Jeong-Ho Kim
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Science, 2300 Eye Street, NW, Washington, D. C., 20037, United States of America
- * E-mail:
| |
Collapse
|
16
|
Yao XG, Xu X, Wang GH, Lei M, Quan LL, Cheng YH, Wan P, Zhou JP, Chen J, Hu LH, Shen X. BBT improves glucose homeostasis by ameliorating β-cell dysfunction in type 2 diabetic mice. J Endocrinol 2015; 224:327-41. [PMID: 25572265 DOI: 10.1530/joe-14-0721] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Impaired glucose-stimulated insulin secretion (GSIS) and increasing β-cell death are two typical dysfunctions of pancreatic β-cells in individuals that are destined to develop type 2 diabetes, and improvement of β-cell function through GSIS enhancement and/or inhibition of β-cell death is a promising strategy for anti-diabetic therapy. In this study, we discovered that the small molecule, N-(2-benzoylphenyl)-5-bromo-2-thiophenecarboxamide (BBT), was effective in both potentiating GSIS and protecting β-cells from cytokine- or streptozotocin (STZ)-induced cell death. Results of further studies revealed that cAMP/PKA and long-lasting (L-type) voltage-dependent Ca(2) (+) channel/CaMK2 pathways were involved in the action of BBT against GSIS, and that the cAMP/PKA pathway was essential for the protective action of BBT on β-cells. An assay using the model of type 2 diabetic mice induced by high-fat diet combined with STZ (STZ/HFD) demonstrated that BBT administration efficiently restored β-cell functions as indicated by the increased plasma insulin level and decrease in the β-cell loss induced by STZ/HFD. Moreover, the results indicated that BBT treatment decreased fasting blood glucose and HbA1c and improved oral glucose tolerance further highlighting the potential of BBT in anti-hyperglycemia research.
Collapse
MESH Headings
- Animals
- Cells, Cultured
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/physiopathology
- Diabetes Mellitus, Type 2/drug therapy
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/physiopathology
- Diet, High-Fat
- Drug Evaluation, Preclinical
- Glucose/metabolism
- HEK293 Cells
- Homeostasis/drug effects
- Humans
- Hypoglycemic Agents/pharmacology
- Hypoglycemic Agents/therapeutic use
- Insulin-Secreting Cells/drug effects
- Insulin-Secreting Cells/physiology
- Male
- Mice
- Mice, Inbred C57BL
- Streptozocin
- Thiophenes/pharmacology
- Thiophenes/therapeutic use
Collapse
Affiliation(s)
- Xin-gang Yao
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| | - Xin Xu
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| | - Gai-hong Wang
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| | - Min Lei
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| | - Ling-ling Quan
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| | - Yan-hua Cheng
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| | - Ping Wan
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| | - Jin-pei Zhou
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| | - Jing Chen
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| | - Li-hong Hu
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| | - Xu Shen
- Key Laboratory of Receptor ResearchShanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, ChinaCollege of Life and Environmental SciencesShanghai Normal University, 100 Guilin Road, Shanghai 200234, ChinaDepartment of PharmacologyChina Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
| |
Collapse
|
17
|
Role of the mammalian target of rapamycin (mTOR) complexes in pancreatic β-cell mass regulation. VITAMINS AND HORMONES 2014; 95:425-69. [PMID: 24559928 DOI: 10.1016/b978-0-12-800174-5.00017-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Exquisite regulation of insulin secretion by pancreatic β-cells is essential to maintain metabolic homeostasis. β-Cell mass must be accordingly adapted to metabolic needs and can be largely modified under different situations. The mammalian target of rapamycin (mTOR) complexes has been consistently identified as key modulators of β-cell mass. mTOR can be found into two different complexes, mTORC1 and mTORC2. Under systemic insulin resistance, mTORC1/mTORC2 signaling in β-cells is needed to increase β-cell mass and insulin secretion. However, type 2 diabetes arises when these compensatory mechanisms fail, being the role of mTOR complexes still obscure in β-cell failure. In this chapter, we introduce the protein composition and regulation of mTOR complexes and their role in pancreatic β-cells. Furthermore, we describe their main signaling effectors through the review of numerous animal models, which indicate the essential role of mTORC1/mTORC2 in pancreatic β-cell mass regulation.
Collapse
|
18
|
Signaling mechanisms of glucose-induced F-actin remodeling in pancreatic islet β cells. Exp Mol Med 2013; 45:e37. [PMID: 23969997 PMCID: PMC3789261 DOI: 10.1038/emm.2013.73] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 06/24/2013] [Indexed: 12/12/2022] Open
Abstract
The maintenance of whole-body glucose homeostasis is critical for survival, and is controlled by the coordination of multiple organs and endocrine systems. Pancreatic islet β cells secrete insulin in response to nutrient stimuli, and insulin then travels through the circulation promoting glucose uptake into insulin-responsive tissues such as liver, skeletal muscle and adipose. Many of the genes identified in human genome-wide association studies of diabetic individuals are directly associated with β cell survival and function, giving credence to the idea that β-cell dysfunction is central to the development of type 2 diabetes. As such, investigations into the mechanisms by which β cells sense glucose and secrete insulin in a regulated manner are a major focus of current diabetes research. In particular, recent discoveries of the detailed role and requirements for reorganization/remodeling of filamentous actin (F-actin) in the regulation of insulin release from the β cell have appeared at the forefront of islet function research, having lapsed in prior years due to technical limitations. Recent advances in live-cell imaging and specialized reagents have revealed localized F-actin remodeling to be a requisite for the normal biphasic pattern of nutrient-stimulated insulin secretion. This review will provide an historical look at the emergent focus on the role of the actin cytoskeleton and its regulation of insulin secretion, leading up to the cutting-edge research in progress in the field today.
Collapse
|
19
|
Wauson EM, Guerra ML, Barylko B, Albanesi JP, Cobb MH. Off-target effects of MEK inhibitors. Biochemistry 2013; 52:5164-6. [PMID: 23848362 DOI: 10.1021/bi4007644] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mitogen-activated protein kinases (MAPKs) ERK1/2 regulate numerous cellular processes, including gene transcription, proliferation, and differentiation. The only known substrates of the MAP2Ks MEK1/2 are ERK1/2; thus, MEK inhibitors PD98059, U0126, and PD0325901 have been important tools in determining the functions of ERK1/2. By using these inhibitors and genetically manipulating MEK, we found that ERK1/2 activation is neither sufficient nor necessary for regulated secretion of insulin from pancreatic β cells or secretion of epinephrine from chromaffin cells. We show that both PD98059 and U0126 reduce agonist-induced entry of calcium into cells in a manner independent of their ability to inhibit ERK1/2. Caution should be used when interpreting results from experiments using these compounds.
Collapse
Affiliation(s)
- Eric M Wauson
- Department of Pharmacology, University of Texas Southwestern Medical Center , Dallas, Texas 75390-9041, United States
| | | | | | | | | |
Collapse
|
20
|
Abstract
The RNA-binding protein RNA-binding motif protein 4 (RBM4) modulates alternative splicing of muscle-specific mRNA isoforms during muscle cell differentiation. To better understand the physiological function of RBM4, we exploited a gene knockout strategy in the present study. Mice with targeted disruption of one of the two Rbm4 genes exhibited hyperglycemia coincident with reduced levels of serum insulin and reduced size of pancreatic islets. The embryonic pancreases of Rbm4-deficient mice showed reduced expression or aberrant splicing of many transcripts encoding factors required for pancreas cell differentiation and function. Using pancreatic acinar AR42J cells, we demonstrated that RBM4 promoted insulin gene expression by altering the isoform balance of the transcription factors Isl1 and Pax4 via alternative splicing control. RBM4 overexpression was sufficient to convert AR42J cells into insulin-producing cells. Moreover, RBM4 may mediate glucose-induced insulin expression and insulin receptor isoform switches. These results suggest that RBM4 may have role in promoting pancreas cell differentiation and endocrine function, essentially via alternative splicing regulation.
Collapse
|
21
|
Kim HS, Tian L, Lin S, Cha JH, Jung HS, Park KS, Moon WK. Magnetic labeling of pancreaticβ-cells modulates the glucose- and insulin-induced phosphorylation of ERK1/2 and AKT. CONTRAST MEDIA & MOLECULAR IMAGING 2012; 8:20-6. [DOI: 10.1002/cmmi.1490] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Hoe Suk Kim
- Department of Radiology; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
- Institute of Radiation Medicine, Medical Research Center; Seoul National University; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Lianji Tian
- Department of Radiology; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
- Department of Biomedical Science, College of Medicine; Seoul National University; Seoul, 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Shunmei Lin
- Department of Radiology; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Joo Hee Cha
- Department of Radiology; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Hye Seung Jung
- Department of Internal Medicine; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Kyong Soo Park
- Department of Internal Medicine; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| | - Woo Kyung Moon
- Department of Radiology; Seoul National University Hospital; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
- Institute of Radiation Medicine, Medical Research Center; Seoul National University; 101 Daehangno, Jongno-gu Seoul 110-744 Korea
- Department of Biomedical Science, College of Medicine; Seoul National University; Seoul, 101 Daehangno, Jongno-gu Seoul 110-744 Korea
| |
Collapse
|
22
|
Taniguchi S, Kimura T, Umeki T, Kimura Y, Kimura H, Ishii I, Itoh N, Naito Y, Yamamoto H, Niki I. Protein phosphorylation involved in the gene expression of the hydrogen sulphide producing enzyme cystathionine γ-lyase in the pancreatic β-cell. Mol Cell Endocrinol 2012; 350:31-8. [PMID: 22133746 DOI: 10.1016/j.mce.2011.11.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 11/16/2011] [Accepted: 11/16/2011] [Indexed: 01/24/2023]
Abstract
Cystathionine γ-lyase (CSE) is one of the major enzymes for the production of hydrogen sulphide (H(2)S), a multifunctional gasotransmitter in the pancreatic β-cell. We examined the mechanisms by which glucose induces CSE expression in mouse pancreatic islets and the insulin-secreting cell line MIN6. CSE expression was increased by anti-diabetic sulphonylureas, and decreased by the ATP-sensitive K(+)-channel opener diazoxide and the voltage-dependent Ca(2+) channel blocker nitrendipine. Application of the synthetic inhibitors of protein kinases revealed the involvement of Ca(2+)/calmodulin-dependent protein kinase (CaMK) II and extracellular signal-regulated protein kinase (ERK) in glucose- and thapsigargin-induced CSE expression. The CaMK IIδ knockdown also suppressed CSE expression. Knockdown of the transcription factors Sp1 and Elk1, both of which can be phosphorylated by ERK, blunted CSE expression. By a reporter assay, we found Sp1 may directly and Elk1 may indirectly regulate CSE expression. These findings suggest Ca(2+)-dependent CSE expression may be mediated via protein phosphorylation of Sp1 and Elk1 in pancreatic β-cells.
Collapse
Affiliation(s)
- Shigeki Taniguchi
- Department of Pharmacology, Oita University, 1-1 Idaigaoka, Hasama, Oita 879-5593, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Tarabra E, Pelengaris S, Khan M. A simple matter of life and death-the trials of postnatal Beta-cell mass regulation. Int J Endocrinol 2012; 2012:516718. [PMID: 22577380 PMCID: PMC3346985 DOI: 10.1155/2012/516718] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 12/31/2011] [Indexed: 12/17/2022] Open
Abstract
Pancreatic beta-cells, which secrete the hormone insulin, are the key arbiters of glucose homeostasis. Defective beta-cell numbers and/or function underlie essentially all major forms of diabetes and must be restored if diabetes is to be cured. Thus, the identification of the molecular regulators of beta-cell mass and a better understanding of the processes of beta-cell differentiation and proliferation may provide further insight for the development of new therapeutic targets for diabetes. This review will focus on the principal hormones and nutrients, as well as downstream signalling pathways regulating beta-cell mass in the adult. Furthermore, we will also address more recently appreciated regulators of beta-cell mass, such as microRNAs.
Collapse
Affiliation(s)
- Elena Tarabra
- School of Life Sciences, Warwick University, Gibbet Hill Road, Coventry CV4 7AL, UK
- *Elena Tarabra:
| | - Stella Pelengaris
- School of Life Sciences, Warwick University, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Michael Khan
- School of Life Sciences, Warwick University, Gibbet Hill Road, Coventry CV4 7AL, UK
| |
Collapse
|
24
|
Lombardi A, Ulianich L, Treglia AS, Nigro C, Parrillo L, Lofrumento DD, Nicolardi G, Garbi C, Beguinot F, Miele C, Di Jeso B. Increased hexosamine biosynthetic pathway flux dedifferentiates INS-1E cells and murine islets by an extracellular signal-regulated kinase (ERK)1/2-mediated signal transmission pathway. Diabetologia 2012; 55:141-53. [PMID: 22006246 DOI: 10.1007/s00125-011-2315-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 08/25/2011] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS Beta cell failure is caused by loss of cell mass, mostly by apoptosis, but also by simple dysfunction (decline of glucose-stimulated insulin secretion, downregulation of specific gene expression). Apoptosis and dysfunction are caused, at least in part, by lipoglucotoxicity. The mechanisms implicated are oxidative stress, increase in the hexosamine biosynthetic pathway (HBP) flux and endoplasmic reticulum (ER) stress. Oxidative stress plays a role in glucotoxicity-induced beta cell dedifferentiation, while glucotoxicity-induced ER stress has been mostly linked to beta cell apoptosis. We sought to clarify whether ER stress caused by increased HBP flux participates in a dedifferentiating response of beta cells, in the absence of relevant apoptosis. METHODS We used INS-1E cells and murine islets. We analysed the unfolded protein response and the expression profile of beta cells by real-time RT-PCR and western blot. The signal transmission pathway elicited by ER stress was investigated by real-time RT-PCR and immunofluorescence. RESULTS Glucosamine and high glucose induced ER stress, but did not decrease cell viability in INS-1E cells. ER stress caused dedifferentiation of beta cells, as shown by downregulation of beta cell markers and of the transcription factor, pancreatic and duodenal homeobox 1. Glucose-stimulated insulin secretion was inhibited. These effects were prevented by the chemical chaperone, 4-phenyl butyric acid. The extracellular signal-regulated kinase (ERK) signal transmission pathway was implicated, since its inhibition prevented the effects induced by glucosamine and high glucose. CONCLUSIONS/INTERPRETATION Glucotoxic ER stress dedifferentiates beta cells, in the absence of apoptosis, through a transcriptional response. These effects are mediated by the activation of ERK1/2.
Collapse
Affiliation(s)
- A Lombardi
- Dipartimento di Scienze e Tecnologie Biologiche e Ambientali, Università degli Studi del Salento, 73100 Lecce, Italy
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Goehring I, Sauter NS, Catchpole G, Assmann A, Shu L, Zien KS, Moehlig M, Pfeiffer AFH, Oberholzer J, Willmitzer L, Spranger J, Maedler K. Identification of an intracellular metabolic signature impairing beta cell function in the rat beta cell line INS-1E and human islets. Diabetologia 2011; 54:2584-94. [PMID: 21796486 DOI: 10.1007/s00125-011-2249-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 06/06/2011] [Indexed: 12/12/2022]
Abstract
AIMS/HYPOTHESIS Chronic hyperglycaemia promotes the progressive failure of pancreatic beta cells in patients with type 2 diabetes mellitus, a clinically highly relevant phenomenon known as glucotoxicity. The intracellular metabolic consequences of a chronically high availability of glucose in beta cells are, as yet, poorly understood in its full complexity. METHODS An unbiased metabolite profiling analysis (GC-time-of-flight-MS) was used to identify the time course of core metabolite patterns in rat beta cell line INS-1E during exposure to high glucose concentrations and its relation to insulin expression. RESULTS We report here that pentose phosphate pathway (PPP) metabolites accumulate remarkably during chronic but not acute glucose treatment, indicating altered processing of glucose through the pentose phosphate pathway. Subsequent functional studies in INS-1E cells and human islets revealed that a disturbance in this pathway contributes to decreases in insulin gene expression and a lack of glucose-stimulated insulin secretion. These effects were found to depend on the activation of extracellular-regulated-kinase (ERK1/2). Long-term inhibition of 6-phosphogluconic acid dehydrogenase resulted in accumulation of PPP metabolites, induced ERK1/2 activation independently of high glucose and impaired beta cell function. In turn, inhibition of ERK1/2 overstimulation during chronic glucose exposure partly inhibited metabolite accumulation and restored beta cell function. CONCLUSIONS/INTERPRETATION Based on unbiased metabolite analyses, the data presented here provide novel targets, namely the inhibition of PPP metabolite accumulation towards the therapeutic goal to preserve and potentially improve beta cell function in diabetes.
Collapse
Affiliation(s)
- I Goehring
- Department of Endocrinology, Diabetes and Nutrition, Charité-Universitaetsmedizin Berlin, Nuthetal, Germany
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Zhang L, Yang G, Tang G, Wu L, Wang R. Rat pancreatic level of cystathionine γ-lyase is regulated by glucose level via specificity protein 1 (SP1) phosphorylation. Diabetologia 2011; 54:2615-25. [PMID: 21618058 DOI: 10.1007/s00125-011-2187-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 04/19/2011] [Indexed: 01/24/2023]
Abstract
AIMS/HYPOTHESIS Cystathionine γ-lyase (CSE) catalyses the endogenous production of hydrogen sulphide (H(2)S) in pancreatic beta cells, and H(2)S has been shown to inhibit insulin release from these cells. As altered pancreatic H(2)S production modulated by glucose has been previously shown, we hypothesised that the Cse gene could be regulated by glucose level in insulin-secreting cells. METHODS The effects of glucose on CSE protein level and mRNA level were analysed in INS-1E cells. Glucose effect on Cse promoter activity was tested by constructing a proximal Cse promoter vector including specificity protein 1 (Sp1) consensus sequence. RESULTS High glucose (20 mmol/l) inhibited H(2)S production in INS-1E cells and freshly isolated rat pancreatic islets. Cse mRNA expression, CSE activity and protein abundance were also profoundly reduced by high glucose. The involvement of SP1 in basal and high-glucose-regulated CSE production was demonstrated. Sp1-knockdown abolished a large portion of CSE production at basal glucose. Phosphorylation of SP1 stimulated by high glucose was inhibited by p38 mitogen-activated protein kinase (MAPK) inhibitors SB203580 and SB202190. After blocking p38 MAPK phosphorylation, the inhibitive effects of high glucose on CSE protein production and promoter activity in INS-1E cells were also virtually abolished. CONCLUSIONS/INTERPRETATION Glucose stimulates the phosphorylation of SP1 via p38 MAPK activation, which leads to decreased Cse promoter activity and subsequent downregulation of Cse gene expression. Inhibited H(2)S production through glucose-mediated CSE activity and production alterations may be involved in the fine control of glucose-induced insulin secretion.
Collapse
Affiliation(s)
- L Zhang
- Department of Biology, Lakehead University, 955 Oliver Road, Thunder Bay, ON, Canada, P7B 5E1
| | | | | | | | | |
Collapse
|
27
|
Dalle S, Ravier MA, Bertrand G. Emerging roles for β-arrestin-1 in the control of the pancreatic β-cell function and mass: New therapeutic strategies and consequences for drug screening. Cell Signal 2011; 23:522-8. [DOI: 10.1016/j.cellsig.2010.09.014] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Accepted: 09/06/2010] [Indexed: 01/09/2023]
|
28
|
Yu T, Jhun BS, Yoon Y. High-glucose stimulation increases reactive oxygen species production through the calcium and mitogen-activated protein kinase-mediated activation of mitochondrial fission. Antioxid Redox Signal 2011; 14:425-37. [PMID: 20518702 PMCID: PMC3025178 DOI: 10.1089/ars.2010.3284] [Citation(s) in RCA: 206] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Increased production of reactive oxygen species (ROS) from mitochondria is the main cause of hyperglycemic complications. We previously showed that hyperglycemic conditions induce mitochondrial fragmentation that is causal for ROS overproduction. This study was to identify signaling components that induce mitochondrial fragmentation in high-glucose stimulation. We found that exposing cells to the high-glucose concentration evokes increases in cytosolic Ca(2+). Chelating Ca(2+) in the high-glucose medium prevented not only the Ca(2+) transient but also mitochondrial fragmentation and the ROS increase, indicating that the Ca(2+) influx across the plasma membrane is an upstream event governing mitochondrial fission and the ROS generation in high-glucose stimulation. We found that the high-glucose-induced Ca(2+) increase activates the mitogen-activated protein kinase extracellular signal-regulated kinase 1/2 (ERK1/2). The Ca(2+) chelation prevented the ERK1/2 activation, and inhibition of the ERK1/2 phosphorylation decreased mitochondrial fragmentation as well as ROS levels in high-glucose stimulation. In addition, the level of the mitochondrial fission protein dynamin-like protein 1 in mitochondria increased in high-glucose incubation in a Ca(2+)-dependent manner. In vitro kinase assays showed that ERK1/2 is capable of phosphorylating dynamin-like protein 1. These results demonstrate that high-glucose stimulation induces the activation of mitochondrial fission via signals mediated by intracellular Ca(2+) and ERK1/2.
Collapse
Affiliation(s)
- Tianzheng Yu
- Department of Anesthesiology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
| | | | | |
Collapse
|
29
|
Calcineurin increases glucose activation of ERK1/2 by reversing negative feedback. Proc Natl Acad Sci U S A 2010; 107:22314-9. [PMID: 21135229 DOI: 10.1073/pnas.1016630108] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
In pancreatic β cells, ERK1 and ERK2 participate in nutrient sensing, and their activities rise and fall as a function of glucose concentration over the physiologic range. Glucose metabolism triggers calcium influx and release of calcium from intracellular stores to activate ERK1/2. Calcium influx also activates the calcium-dependent phosphatase calcineurin, which is required for maximal ERK1/2 activation by glucose. Calcineurin controls insulin gene expression by ERK1/2-dependent and -independent mechanisms. Here, we show that, in β cells, glucose activates the ERK1/2 cascade primarily through B-Raf. Glucose activation of B-Raf, like that of ERK1/2, is calcineurin-sensitive. Calcineurin binds to B-Raf in both unstimulated and stimulated cells. We show that B-Raf is a calcineurin substrate; among calcineurin target residues on B-Raf is T401, a site of negative feedback phosphorylation by ERK1/2. Blocking calcineurin activity in β cells prevents dephosphorylation of B-Raf T401 and decreases B-Raf and ERK1/2 activities. We conclude that the major calcineurin-dependent event in glucose sensing by ERK1/2 is the activation of B-Raf.
Collapse
|
30
|
Youl E, Bardy G, Magous R, Cros G, Sejalon F, Virsolvy A, Richard S, Quignard JF, Gross R, Petit P, Bataille D, Oiry C. Quercetin potentiates insulin secretion and protects INS-1 pancreatic β-cells against oxidative damage via the ERK1/2 pathway. Br J Pharmacol 2010; 161:799-814. [PMID: 20860660 DOI: 10.1111/j.1476-5381.2010.00910.x] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND AND PURPOSE Quercetin lowers plasma glucose, normalizes glucose tolerance tests and preserves pancreatic β-cell integrity in diabetic rats. However, its mechanism of action has never been explored in insulin-secreting β-cells. Using the INS-1 β-cell line, the effects of quercetin were determined on glucose- or glibenclamide-induced insulin secretion and on β-cell dysfunctions induced by hydrogen peroxide (H(2)O(2)). These effects were analysed along with the activation of the extracellular signal-regulated kinase (ERK)1/2 pathway. N-acetyl-L-cysteine (NAC) and resveratrol, two antioxidants also known to exhibit some anti-diabetic properties, were used for comparison. EXPERIMENTAL APPROACH Insulin release was quantified by the homogeneous time resolved fluorescence method and ERK1/2 activation tested by Western blot experiments. Cell viability was estimated by the [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (MTT) colorimetric assay. KEY RESULTS Quercetin (20 µmol·L(-1)) potentiated both glucose (8.3 mmol·L(-1))- and glibenclamide (0.01 µmol·L(-1))-induced insulin secretion and ERK1/2 phosphorylation. The ERK1/2 (but not the protein kinase A) signalling pathway played a crucial role in the potentiation of glucose-induced insulin secretion by quercetin. In addition, quercetin (20 µmol·L(-1)), protected β-cell function and viability against oxidative damage induced by 50 µmol·L(-1) H(2)O(2) and induced a major phosphorylation of ERK1/2. In the same conditions, resveratrol or NAC were ineffective. CONCLUSION AND IMPLICATIONS Quercetin potentiated glucose and glibenclamide-induced insulin secretion and protected β-cells against oxidative damage. Our study suggested that ERK1/2 played a major role in those effects. The potential of quercetin in preventing β-cell dysfunction associated with diabetes deserves further investigation.
Collapse
Affiliation(s)
- E Youl
- Université Montpellier I et CNRS UMR 5232, Centre de Pharmacologie et Innovation dans le Diabète (CPID), Montpellier, France
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Abstract
Pancreatic β-cell response to glucose stimulation is governed by tightly regulated signaling pathways which have not been fully characterized. A screen for novel signaling intermediates identified Pim3 as a glucose-responsive gene in the β cell, and here, we characterize its role in the regulation of β-cell function. Pim3 expression in the β-cell was first observed through microarray analysis on glucose-stimulated murine insulinoma (MIN6) cells where expression was strongly and transiently induced. In the pancreas, Pim3 expression exhibited similar dynamics and was restricted to the β cell. Perturbation of Pim3 function resulted in enhanced glucose-stimulated insulin secretion, both in MIN6 cells and in isolated islets from Pim3-/- mice, where the augmentation was specifically seen in the second phase of secretion. Consequently, Pim3-/- mice displayed an increased glucose tolerance in vivo. Interestingly, Pim3-/- mice also exhibited increased insulin sensitivity. Glucose stimulation of isolated Pim3-/- islets resulted in increased phosphorylation of ERK1/2, a kinase involved in regulating β-cell response to glucose. Pim3 was also found to physically interact with SOCS6 and SOCS6 levels were strongly reduced in Pim3-/- islets. Overexpression of SOCS6 inhibited glucose-induced ERK1/2 activation, strongly suggesting that Pim3 regulates ERK1/2 activity through SOCS6. These data reveal that Pim3 is a novel glucose-responsive gene in the β cell that negatively regulates insulin secretion by inhibiting the activation of ERK1/2, and through its effect on insulin sensitivity, has potentially a more global function in glucose homeostasis.
Collapse
Affiliation(s)
- Gregory Vlacich
- Department of Medicine, University of Chicago, Chicago, IL, USA
| | | | | | | |
Collapse
|
32
|
Bernal-Mizrachi E, Cras-Méneur C, Ye BR, Johnson JD, Permutt MA. Transgenic overexpression of active calcineurin in beta-cells results in decreased beta-cell mass and hyperglycemia. PLoS One 2010; 5:e11969. [PMID: 20689817 PMCID: PMC2914754 DOI: 10.1371/journal.pone.0011969] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Accepted: 07/09/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Glucose modulates beta-cell mass and function through an initial depolarization and Ca(2+) influx, which then triggers a number of growth regulating signaling pathways. One of the most important downstream effectors in Ca(2+) signaling is the calcium/Calmodulin activated serine threonine phosphatase, calcineurin. Recent evidence suggests that calcineurin/NFAT is essential for beta-cell proliferation, and that in its absence loss of beta-cells results in diabetes. We hypothesized that in contrast, activation of calcineurin might result in expansion of beta-cell mass and resistance to diabetes. METHODOLOGY/PRINCIPAL FINDINGS To determine the role of activation of calcineurin signaling in the regulation of pancreatic beta-cell mass and proliferation, we created mice that expressed a constitutively active form of calcineurin under the insulin gene promoter (caCn(RIP)). To our surprise, these mice exhibited glucose intolerance. In vitro studies demonstrated that while the second phase of Insulin secretion is enhanced, the overall insulin secretory response was conserved. Islet morphometric studies demonstrated decreased beta-cell mass suggesting that this was a major component responsible for altered Insulin secretion and glucose intolerance in caCn(RIP) mice. The reduced beta-cell mass was accompanied by decreased proliferation and enhanced apoptosis. CONCLUSIONS Our studies identify calcineurin as an important factor in controlling glucose homeostasis and indicate that chronic depolarization leading to increased calcineurin activity may contribute, along with other genetic and environmental factors, to beta-cell dysfunction and diabetes.
Collapse
Affiliation(s)
- Ernesto Bernal-Mizrachi
- Division of Metabolism, Endocrinology, Diabetes, The Brehm Center for Type 1 Diabetes, University of Michigan, Ann Arbor, Michigan, United States of America.
| | | | | | | | | |
Collapse
|
33
|
Shao C, Lawrence MC, Cobb MH. Regulation of CCAAT/enhancer-binding protein homologous protein (CHOP) expression by interleukin-1 beta in pancreatic beta cells. J Biol Chem 2010; 285:19710-9. [PMID: 20424162 DOI: 10.1074/jbc.m109.087486] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Apoptosis contributes to immune-mediated pancreatic beta cell destruction in type I diabetes. Exposure of beta cells to interleukin-1beta (IL-1beta) causes endoplasmic reticulum stress and activates proapoptotic networks. Here, we show that nuclear factor kappaB (NF-kappaB) and mitogen-activated protein kinase (MAPK) signaling pathways regulate the expression of CCAAT/enhancer-binding protein homologous protein (CHOP), which mediates endoplasmic reticulum stress-induced apoptosis. Both CHOP mRNA and protein increase in beta cells treated with IL-1beta. In addition, prolonged exposure to high glucose further increases IL-1beta-triggered CHOP expression. IL-1beta also causes increased expression of C/EBP-beta and a reduction of MafA, NFATc2, and Pdx-1 expression in beta cells. Inhibition of the NF-kappaB and MAPK signaling pathways differentially attenuates CHOP expression. Knocking down CHOP by RNA interference protects beta cells from IL-1beta-induced apoptosis. These studies provide direct mechanistic links between cytokine-induced signaling pathways and CHOP-mediated apoptosis of beta cells.
Collapse
Affiliation(s)
- Chunli Shao
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041, USA
| | | | | |
Collapse
|
34
|
Kowluru A, Veluthakal R, Rhodes CJ, Kamath V, Syed I, Koch BJ. Protein farnesylation-dependent Raf/extracellular signal-related kinase signaling links to cytoskeletal remodeling to facilitate glucose-induced insulin secretion in pancreatic beta-cells. Diabetes 2010; 59:967-77. [PMID: 20071600 PMCID: PMC2844844 DOI: 10.2337/db09-1334] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OBJECTIVE Posttranslational prenylation (e.g., farnesylation) of small G-proteins is felt to be requisite for cytoskeletal remodeling and fusion of secretory vesicles with the plasma membrane. Here, we investigated roles of protein farnesylation in the signaling steps involved in Raf-1/extracellular signal-related kinase (ERK1/2) signaling pathway in glucose-induced Rac1 activation and insulin secretion in the pancreatic beta-cell. RESEARCH DESIGN AND METHODS These studies were carried out in INS 832/13 cells and normal rat islets. Molecular biological (e.g., overexpression or small interfering RNA [siRNA]-mediated knockdown) and pharmacologic approaches were used to determine roles for farnesylation in glucose-mediated activation of ERK1/2, Rac1, and insulin secretion. Activation of ERK1/2 was determined by Western blotting. Rac1 activation (i.e., Rac1.GTP) was quantitated by p21-activated kinase pull-down assay. Insulin release was quantitated by enzyme-linked immunosorbent assay. RESULTS Coprovision of structure-specific inhibitors of farnesyl transferase (FTase; e.g., FTI-277 or FTI-2628) or siRNA-mediated knockdown of FTase beta-subunit resulted in a significant inhibition of glucose-stimulated ERK1/2 and Rac1 activation and insulin secretion. Pharmacologic inhibition of Raf-1 kinase using GW-5074 markedly reduced the stimulatory effects of glucose on ERK1/2 phosphorylation, Rac1 activation, and insulin secretion, suggesting that Raf-1 kinase activation may be upstream to ERK1/2 and Rac1 activation leading to glucose-induced insulin release. Lastly, siRNA-mediated silencing of endogenous expression of ERK1/2 markedly attenuated glucose-induced Rac1 activation and insulin secretion. CONCLUSIONS Together, our findings provide the first evidence of a role for protein farnesylation in glucose-mediated regulation of the Raf/ERK signaling pathway culminating in the activation of Rac1, which has been shown to be necessary for cytoskeletal reorganization and exocytotic secretion of insulin.
Collapse
Affiliation(s)
- Anjaneyulu Kowluru
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan, USA.
| | | | | | | | | | | |
Collapse
|
35
|
Qiu Y, Mao T, Zhang Y, Shao M, You J, Ding Q, Chen Y, Wu D, Xie D, Lin X, Gao X, Kaufman RJ, Li W, Liu Y. A crucial role for RACK1 in the regulation of glucose-stimulated IRE1alpha activation in pancreatic beta cells. Sci Signal 2010; 3:ra7. [PMID: 20103773 PMCID: PMC2940714 DOI: 10.1126/scisignal.2000514] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Autophosphorylation of inositol-requiring enzyme 1alpha (IRE1alpha) is required for its activation, which elicits the cellular unfolded protein response (UPR) and is functionally connected with insulin biosynthesis in pancreatic beta cells. We found that the scaffold protein receptor for activated C-kinase 1 (RACK1) interacted with IRE1alpha in a glucose-stimulated or endoplasmic reticulum (ER) stress-responsive manner in pancreatic beta cells and primary islets. RACK1 mediated the glucose-inducible assembly of a complex containing IRE1alpha, RACK1, and protein phosphatase 2A (PP2A) to promote dephosphorylation of IRE1alpha by PP2A, thereby inhibiting glucose-stimulated IRE1alpha activation and attenuating IRE1alpha-dependent increases in insulin production. Moreover, IRE1alpha activation was increased and RACK1 abundance was decreased in a mouse model of diabetes. Thus, our findings demonstrate that RACK1 functions as a key component in regulating the IRE1alpha signaling pathway in pancreatic beta cells.
Collapse
Affiliation(s)
- Yifu Qiu
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Ting Mao
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Yongliang Zhang
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Mengle Shao
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Jia You
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Qiurong Ding
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Yan Chen
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Dongmei Wu
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Dong Xie
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Xu Lin
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Xiang Gao
- Model Animal Research Center, Nanjing University, Nanjing 210093, China
| | - Randal J. Kaufman
- Department of Biological Chemistry and Internal Medicine, Howard Hughes Medical Institute, University of Michigan Medical Center, Ann Arbor, Michigan 48105, USA
| | - Wenjun Li
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| | - Yong Liu
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences; Graduate School of the Chinese Academy of Sciences; Shanghai 200031, China
| |
Collapse
|
36
|
Multiple chromatin-bound protein kinases assemble factors that regulate insulin gene transcription. Proc Natl Acad Sci U S A 2009; 106:22181-6. [PMID: 20018749 DOI: 10.1073/pnas.0912596106] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
During the onset of diabetes, pancreatic beta cells become unable to produce sufficient insulin to maintain blood glucose within the normal range. Proinflammatory cytokines have been implicated in impaired beta cell function. To understand more about the molecular events that reduce insulin gene transcription, we examined the effects of hyperglycemia alone and together with the proinflammatory cytokine interleukin-1beta (IL-1beta) on signal transduction pathways that regulate insulin gene transcription. Exposure to IL-1beta in fasting glucose activated multiple protein kinases that associate with the insulin gene promoter and transiently increased insulin gene transcription in beta cells. In contrast, cells exposed to hyperglycemic conditions were sensitized to the inhibitory actions of IL-1beta. Under these conditions, IL-1beta caused the association of the same protein kinases, but a different combination of transcription factors with the insulin gene promoter and began to reduce transcription within 2 h; stimulatory factors were lost, RNA polymerase II was lost, and inhibitory factors were bound to the promoter in a kinase-dependent manner.
Collapse
|
37
|
KSR2 Is a Calcineurin Substrate that Promotes ERK Cascade Activation in Response to Calcium Signals. Mol Cell 2009; 34:652-62. [DOI: 10.1016/j.molcel.2009.06.001] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 01/29/2009] [Accepted: 06/04/2009] [Indexed: 12/30/2022]
|
38
|
Khoo S, Gibson TB, Arnette D, Lawrence M, January B, McGlynn K, Vanderbilt CA, Griffen SC, German MS, Cobb MH. MAP kinases and their roles in pancreatic beta-cells. Cell Biochem Biophys 2009; 40:191-200. [PMID: 15289654 DOI: 10.1385/cbb:40:3:191] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We discuss our work examining regulation and functions of mitogen-activated protein kinases, particularly ERK1 and ERK2, in pancreatic beta-cells. These enzymes are activated by glucose, other nutrients, and insulinogenic hormones. Their activation by these agents is calcium-dependent. A number of other stimuli also activate ERK1/2, but by mechanisms distinct from those involved in nutrient sensing. Inhibition of ERK1/2 has no apparent effect on insulin secretion measured after 2 h. On the other hand, ERK1/2 activity is required for maximal glucose-dependent activation of the insulin gene promoter. The primary effort has focused on INS-1 cell lines, with supporting and confirmatory studies in intact islets and other beta-cell lines, indicating the generality of our findings in beta-cell function. Thus ERK1/2 participate in transmitting glucose-sensing information to beta-cell functions. These kinases most likely act directly and indirectly on multiple pathways that regulate beta-cell function and, in particular, to transduce an elevated glucose signal into insulin gene transcription.
Collapse
Affiliation(s)
- Shih Khoo
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
39
|
Glucose effects on beta-cell growth and survival require activation of insulin receptors and insulin receptor substrate 2. Mol Cell Biol 2009; 29:3219-28. [PMID: 19273608 DOI: 10.1128/mcb.01489-08] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Insulin and insulin-like growth factor I (IGF-I) are ubiquitous hormones that regulate growth and metabolism of most mammalian cells, including pancreatic beta-cells. In addition to being an insulin secretagogue, glucose regulates proliferation and survival of beta-cells. However, it is unclear whether the latter effects of glucose occur secondary to autocrine activation of insulin signaling proteins by secreted insulin. To examine this possibility we studied the effects of exogenous glucose or insulin in beta-cell lines completely lacking either insulin receptors (betaIRKO) or insulin receptor substrate 2 (betaIRS2KO). Exogenous addition of either insulin or glucose activated proteins in the insulin signaling pathway in control beta-cell lines with the effects of insulin peaking earlier than glucose. Insulin stimulation of betaIRKO and betaIRS2KO cells led to blunted activation of phosphatidylinositol 3-kinase and Akt kinase, while surprisingly, glucose failed to activate either kinase but phosphorylated extracellular signal-regulated kinase. Control beta-cells exhibited low expression of IGF-1 receptors compared to compensatory upregulation in betaIRKO cells. The signaling data support the slow growth and reduced DNA and protein synthesis in betaIRKO and betaIRS2KO cells in response to glucose stimulation. Together, these studies provide compelling evidence that the growth and survival effects of glucose on beta-cells require activation of proteins in the insulin signaling pathway.
Collapse
|
40
|
Sol ERM, Sundsten T, Bergsten P. Role of MAPK in apolipoprotein CIII-induced apoptosis in INS-1E cells. Lipids Health Dis 2009; 8:3. [PMID: 19196457 PMCID: PMC2647908 DOI: 10.1186/1476-511x-8-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 02/05/2009] [Indexed: 11/19/2022] Open
Abstract
Background Individuals with type 2 diabetes mellitus (T2DM) have elevated levels of circulating apolipoprotein CIII (apoCIII). ApoCIII plays an important role for plasma triglyceride levels and elevated levels of the apolipoprotein have been connected with dyslipidemia in T2DM subjects. In addition, apoCIII has been linked to enhanced β-cell apoptosis. The present study was undertaken to investigate apoptotic mechanisms induced by the apolipoprotein. Results ApoCIII (10 μg/ml) enhanced apoptosis 2-fold in insulin-producing INS-1E cells after 24 hours exposure to the apolipoprotein. At this time point phosphorylation of mitogen activated protein kinase (MAPK) p38 had doubled but ERK1/2 and JNK were not activated. Instead, ERK1/2 showed rapid and transient phosphorylation (2-fold after 0.5 hour). No JNK phosphorylation was observed. In support of a role of activation of not only p38 but also ERK1/2 in apoCIII-induced apoptosis, inclusion of p38 inhibitor SB203580 (10 μM) or ERK1/2 inhibitor PD98059 (100 μM) normalized apoptosis. Whereas influx of Ca2+ was linked to apoCIII-induced ERK1/2 activation, pro-apoptotic protein CHOP/GADD of the unfolded protein response (UPR) was not affected by apoCIII. Conclusion It is suggested that elevated circulating apoCIII levels may contribute to β-cell apoptosis via activation of p38 and ERK1/2 in individuals with T2DM. Therapies aiming at normalizing levels of apoCIII could be beneficial not only for the function of the β-cell but also for cardiovascular protection.
Collapse
Affiliation(s)
- E-ri M Sol
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.
| | | | | |
Collapse
|
41
|
Shao C, Cobb MH. Sumoylation regulates the transcriptional activity of MafA in pancreatic beta cells. J Biol Chem 2009; 284:3117-3124. [PMID: 19029092 PMCID: PMC2631948 DOI: 10.1074/jbc.m806286200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Revised: 11/21/2008] [Indexed: 01/01/2023] Open
Abstract
MafA is a transcriptional regulator expressed primarily in pancreatic beta cells. It binds to the RIPE3b/C1-binding site within the ins gene promoter, which plays a critical role in regulating ins gene expression in response to glucose. Here, we show that MafA is post-translationally modified by the small ubiquitin-related modifiers SUMO-1 and -2. Mutation of a single site in MafA, Lys(32), blocks its sumoylation in beta cells. Incubation of beta cells in low glucose (2 mm) or exposure to hydrogen peroxide increases sumoylation of endogenous MafA. Forced sumoylation of MafA results in reduced transcriptional activity toward the ins gene promoter and increased suppression of the CHOP-10 gene promoter. Sumoylation of MafA has no apparent effect on either its nuclear localization in beta cells or its ubiquitin-dependent degradation. This study suggests that modification of MafA by SUMO modulates gene transcription and thereby beta cell function.
Collapse
Affiliation(s)
- Chunli Shao
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041
| | - Melanie H Cobb
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041.
| |
Collapse
|
42
|
Farrelly AM, Wobser H, Bonner C, Anguissola S, Rehm M, Concannon CG, Prehn JHM, Byrne MM. Early loss of mammalian target of rapamycin complex 1 (mTORC1) signalling and reduction in cell size during dominant-negative suppression of hepatic nuclear factor 1-alpha (HNF1A) function in INS-1 insulinoma cells. Diabetologia 2009; 52:136-44. [PMID: 18949455 DOI: 10.1007/s00125-008-1168-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Accepted: 09/07/2008] [Indexed: 01/19/2023]
Abstract
AIMS/HYPOTHESIS Mutations in the HNF1A (previously known as TCF1) gene encoding hepatocyte nuclear factor-1alpha (HNF1A) lead to the development of maturity-onset diabetes of the young, type 3 (HNF1A-MODY), characterised by impaired insulin secretion and a reduction in beta cell mass. HNF1A plays an important role in pancreatic beta cell differentiation and survival. The mammalian target of rapamycin (mTOR) is a central growth factor- and nutrient-activated protein kinase controlling cell metabolism, growth and survival. We investigated the role of mTOR inactivation in the decline in beta cell mass in a cellular model of HNF1A-MODY. METHODS Previously we showed that suppression of HNF1A function via expression of a dominant-negative mutant (DN-HNF1A) decreases insulin gene transcription in insulinoma (INS-1) cells. We investigated the signalling of two distinct mTOR protein complexes, mTORC1 and mTORC2, in response to DN-HNF1A induction. RESULTS We observed delayed inactivation of mTORC2 48 h after DN-HNF1A induction, evidenced by a reduction in serine 473 phosphorylation of thymoma viral proto-oncogene 1 (AKT1). We also observed an early inactivation of mTORC1 24 h after DN-HNF1A induction, which was detected by decreases in threonine 389 phosphorylation of p70 ribosomal protein S6 kinase (S6K1) and serine 65 phosphorylation of translational inhibitor eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1). Flow cytometry and gene expression analysis demonstrated a pre-apoptotic decrease in INS-1 cell size in response to DN-HNF1A induction, and an increase in the level of the mTORC1-regulated cell-cycle inhibitor, cyclin-dependent kinase inhibitor 1B p27. CONCLUSIONS/INTERPRETATION Our data suggest that mTOR kinase and signalling through mTORC1 are highly sensitive to suppression of HNF1A function, and may contribute to disturbance of cell-size regulation and cell-cycle progression in HNF1A-MODY.
Collapse
Affiliation(s)
- A M Farrelly
- Department of Endocrinology, Mater Misericordiae University Hospital, Eccles Street, Dublin 7, Ireland
| | | | | | | | | | | | | | | |
Collapse
|
43
|
Broca C, Quoyer J, Costes S, Linck N, Varrault A, Deffayet PM, Bockaert J, Dalle S, Bertrand G. beta-Arrestin 1 is required for PAC1 receptor-mediated potentiation of long-lasting ERK1/2 activation by glucose in pancreatic beta-cells. J Biol Chem 2008; 284:4332-42. [PMID: 19074139 DOI: 10.1074/jbc.m807595200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
In pancreatic beta-cells, the pituitary adenylate cyclase-activating polypeptide (PACAP) exerts a potent insulin secretory effect via PAC(1) and VPAC receptors (Rs) through the Galpha(s)/cAMP/protein kinase A pathway. Here, we investigated the mechanisms linking PAC(1)R to ERK1/2 activation in INS-1E beta-cells and pancreatic islets. PACAP caused a transient (5 min) increase in ERK1/2 phosphorylation via PAC(1)Rs and promoted nuclear translocation of a fraction of cytosolic p-ERK1/2. Both protein kinase A- and Src-dependent pathways mediated this transient ERK1/2 activation. Moreover, PACAP potentiated glucose-induced long-lasting ERK1/2 activation. Blocking Ca(2+) influx abolished glucose-induced ERK1/2 activation and PACAP potentiating effect. Glucose stimulation during KCl depolarization showed that, in addition to the triggering signal (rise in cytosolic [Ca(2+)]), the amplifying pathway was also involved in glucose-induced sustained ERK1/2 activation and was required for PACAP potentiation. The finding that at 30 min glucose-induced p-ERK1/2 was detected in both cytosol and nucleus while the potentiating effect of PACAP was only observed in the cytosol, suggested the involvement of the scaffold protein beta-arrestin. Indeed, beta-arrestin 1 (beta-arr1) depletion (in beta-arr1 knockout mouse islets or in INS-1E cells by siRNA) completely abolished PACAP potentiation of long-lasting ERK1/2 activation by glucose. Finally, PACAP potentiated glucose-induced CREB transcriptional activity and IRS-2 mRNA expression mainly via the ERK1/2 signaling pathway, and likewise, beta-arr1 depletion reduced the PACAP potentiating effect on IRS-2 expression. These results establish for the first time that PACAP potentiates glucose-induced long-lasting ERK1/2 activation via a beta-arr1-dependent pathway and thus provide new insights concerning the mechanisms of PACAP and glucose actions in pancreatic beta-cells.
Collapse
Affiliation(s)
- Christophe Broca
- Institut de Génomique Fonctionnelle, CNRS, Unité Mixte de Recherche 5203, INSERM, U661, Université Montpellier I, and Université Montpellier II, 34094 Montpellier Cedex 5, France
| | | | | | | | | | | | | | | | | |
Collapse
|
44
|
TAKETANI T, YAMAGATA Y, TAKASAKI A, MATSUOKA A, TAMURA H, SUGINO N. Effects of growth hormone and insulin-like growth factor 1 on progesterone production in human luteinized granulosa cells. Fertil Steril 2008; 90:744-8. [DOI: 10.1016/j.fertnstert.2007.07.1304] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2007] [Revised: 06/18/2007] [Accepted: 06/18/2007] [Indexed: 11/26/2022]
|
45
|
Matsushita Y, Nakajima K, Tohyama Y, Kurihara T, Kohsaka S. Activation of microglia by endotoxin suppresses the secretion of glial cell line-derived neurotrophic factor (GDNF) through the action of protein kinase C alpha (PKCalpha) and mitogen-activated protein kinases (MAPKS). J Neurosci Res 2008; 86:1959-71. [PMID: 18438912 DOI: 10.1002/jnr.21657] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The ability of microglia to produce/secrete glial cell line-derived neurotrophic factor (GDNF) in vitro was examined. Immunoblotting analysis revealed that nonstimulated microglia release limited amounts of GDNF with molecular sizes of 14 and 17 kDa. However, the secreted amounts significantly decreased when the microglia were activated with the endotoxin lipopolysaccharide (LPS). Comparison of the amounts of GDNF in the cells and the conditioned medium between the nonstimulated microglia and LPS-stimulated microglia clarified that the secretion of GDNF, but not its production, is strongly suppressed when the microglia are activated with LPS. The inhibitor experiments suggested that the GDNF secretion is depressed by a signaling cascade associated with protein kinase C alpha (PKCalpha) and/or mitogen-activated protein kinases (MAPKs). As expected from the above results, a PKC activator suppressed the secretion of GDNF in nonstimulated microglia. Taken together, these results demonstrated that microglia have the ability to produce and secrete GDNF in vitro, and that the secretion is suppressed by stimulation with endotoxin, probably due to a signaling mechanism involving PKCalpha and/or MAPKs.
Collapse
Affiliation(s)
- Yuichi Matsushita
- Department of Bioinformatics, Faculty of Engineering, Soka University, Hachioji, Tokyo, Japan
| | | | | | | | | |
Collapse
|
46
|
Ramos LS, Zippin JH, Kamenetsky M, Buck J, Levin LR. Glucose and GLP-1 stimulate cAMP production via distinct adenylyl cyclases in INS-1E insulinoma cells. ACTA ACUST UNITED AC 2008; 132:329-38. [PMID: 18695009 PMCID: PMC2518727 DOI: 10.1085/jgp.200810044] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In β cells, both glucose and hormones, such as GLP-1, stimulate production of the second messenger cAMP, but glucose and GLP-1 elicit distinct cellular responses. We now show in INS-1E insulinoma cells that glucose and GLP-1 produce cAMP with distinct kinetics via different adenylyl cyclases. GLP-1 induces a rapid cAMP signal mediated by G protein–responsive transmembrane adenylyl cyclases (tmAC). In contrast, glucose elicits a delayed cAMP rise mediated by bicarbonate, calcium, and ATP-sensitive soluble adenylyl cyclase (sAC). This glucose-induced, sAC-dependent cAMP rise is dependent upon calcium influx and is responsible for the glucose-induced activation of the mitogen-activated protein kinase (ERK1/2) pathway. These results demonstrate that sAC-generated and tmAC-generated cAMP define distinct signaling cascades.
Collapse
Affiliation(s)
- Lavoisier S Ramos
- Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10065, USA
| | | | | | | | | |
Collapse
|
47
|
Fei H, Zhao B, Zhao S, Wang Q. Requirements of calcium fluxes and ERK kinase activation for glucose- and interleukin-1β-induced β-cell apoptosis. Mol Cell Biochem 2008; 315:75-84. [DOI: 10.1007/s11010-008-9791-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 05/06/2008] [Indexed: 10/22/2022]
|
48
|
Abstract
The healthy beta-cell has an enormous capacity to adapt to conditions of higher insulin demand (e.g. in obesity, pregnancy, cortisol excess) to maintain normoglycaemia with an increase in its functional beta-cell mass. This compensates in 80-90% of individuals for insulin resistance. However, in 10-20% of individuals, the beta-cells are unable to match the demands of insulin resistance and insulin levels are relatively insufficient to maintain normal glycaemic control. This eventually leads to glucose intolerance and type 2 diabetes (T2DM). Accordingly, preservation of functional beta-cell mass has become central in the treatment of type 1 diabetes as well as T2DM. The purpose of this review is to summarize the recently described mechanisms of beta-cell death in T2DM and to postulate possible new targets for treatment.
Collapse
Affiliation(s)
- Kathrin Maedler
- Department of Medicine, Larry L. Hillblom Islet Research Center, University of California at Los Angeles, Los Angeles, CA 90095-7345, USA.
| |
Collapse
|
49
|
Donath MY, Størling J, Berchtold LA, Billestrup N, Mandrup-Poulsen T. Cytokines and beta-cell biology: from concept to clinical translation. Endocr Rev 2008; 29:334-50. [PMID: 18048762 DOI: 10.1210/er.2007-0033] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The tale of cytokines and the beta-cell is a long story, starting with in vitro discovery in 1984, evolving via descriptive and phenomenological studies to detailed mapping of the signalling pathways, gene- and protein expression patterns, molecular and biochemical effector mechanisms to in vivo studies in spontaneously diabetic and transgenic animal models. Only very recently have steps been taken to translate the accumulating compelling preclinical data into clinical trials. The aim of this chapter is to present an overview of early and recent key observations from our own groups as well as other laboratories that serve to illuminate the road from concept to clinical translation.
Collapse
Affiliation(s)
- Marc Y Donath
- The Clinic for Endocrinology and Diabetes, University Hospital Zurich, Zurich, Switzerland
| | | | | | | | | |
Collapse
|
50
|
Abstract
MAP kinases transduce signals that are involved in a multitude of cellular pathways and functions in response to a variety of ligands and cell stimuli. Aberrant or inappropriate functions of MAPKs have now been identified in diseases ranging from cancer to inflammatory disease to obesity and diabetes. In many cell types, the MAPKs ERK1/2 are linked to cell proliferation. ERK1/2 are thought to play a role in some cancers, because mutations in Ras and B-Raf, which can activate the ERK1/2 cascade, are found in many human tumors. Abnormal ERK1/2 signaling has also been found in polycystic kidney disease, and serious developmental disorders such as cardio-facio-cutaneous syndrome arise from mutations in components of the ERK1/2 cascade. ERK1/2 are essential in well-differentiated cells and have been linked to long-term potentiation in neurons and in maintenance of epithelial polarity. Additionally, ERK1/2 are important for insulin gene transcription in pancreatic beta cells, which produce insulin in response to increases in circulating glucose to permit efficient glucose utilization and storage in the organism. Nutrients and hormones that induce or repress insulin secretion activate and/or inhibit ERK1/2 in a manner that reflects the secretory demand on beta cells. Disturbances in this and other regulatory pathways may result in the contribution of ERK1/2 to the etiology of certain human disorders.
Collapse
|