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Zhang M, Wang J, Wang W, Yang G, Peng J. Predicting cell-type specific disease genes of diabetes with the biological network. Comput Biol Med 2024; 169:107849. [PMID: 38101116 DOI: 10.1016/j.compbiomed.2023.107849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 11/21/2023] [Accepted: 12/11/2023] [Indexed: 12/17/2023]
Abstract
Type 2 diabetes (T2D) is a chronic condition that can lead to significant harm, such as heart disease, kidney disease, nerve damage, and blindness. Although T2D-related genes have been identified through Genome-wide association studies (GWAS) and various computational methods, the biological mechanism of T2D at the cell type level remains unclear. Exploring cell type-specific genes related to T2D is essential to understand the cellular mechanisms underlying the disease. To address this issue, we introduce DiGCellNet (predicting Disease Genes with Cell type specificity based on biological Networks), a model that integrates graph convolutional network (GCN) and multi-task learning (MTL) to predict T2D-associated cell type-specific genes based on the biological network. Our work represents the first attempt to predict cell type-specific disease genes using GCN and MTL. We evaluate our approach by predicting genes specific to four cell types and demonstrate that the proposed DiGCellNet outperforms other models that combine node embeddings with traditional machine learning algorithms. Moreover, DiGCellNet successfully identifies CALM1 as a gene specific to beta cell type in T2D cases, and this association is confirmed using an independent dataset. The code is available at https://github.com/23AIBox/23AIBox-DiGCellNet.
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Affiliation(s)
- Menghan Zhang
- School of Computer Science, Northwestern Polytechnical University, Xi'an, 710072, China; Key Laboratory of Big Data Storage and Management, Northwestern Polytechnical University, Ministry of Industry and Information Technology, Xi'an, 710072, China; The National Engineering Laboratory for Integrated Aerospace-Ground-Ocean Big Data Application Technology, Xi'an, 710072, China
| | - Jingru Wang
- School of Computer Science, Northwestern Polytechnical University, Xi'an, 710072, China; Key Laboratory of Big Data Storage and Management, Northwestern Polytechnical University, Ministry of Industry and Information Technology, Xi'an, 710072, China; The National Engineering Laboratory for Integrated Aerospace-Ground-Ocean Big Data Application Technology, Xi'an, 710072, China
| | - Wei Wang
- School of Computer Science, Northwestern Polytechnical University, Xi'an, 710072, China; Key Laboratory of Big Data Storage and Management, Northwestern Polytechnical University, Ministry of Industry and Information Technology, Xi'an, 710072, China; The National Engineering Laboratory for Integrated Aerospace-Ground-Ocean Big Data Application Technology, Xi'an, 710072, China
| | - Guang Yang
- School of Computer Science, Northwestern Polytechnical University, Xi'an, 710072, China; Key Laboratory of Big Data Storage and Management, Northwestern Polytechnical University, Ministry of Industry and Information Technology, Xi'an, 710072, China; The National Engineering Laboratory for Integrated Aerospace-Ground-Ocean Big Data Application Technology, Xi'an, 710072, China
| | - Jiajie Peng
- School of Computer Science, Northwestern Polytechnical University, Xi'an, 710072, China; Key Laboratory of Big Data Storage and Management, Northwestern Polytechnical University, Ministry of Industry and Information Technology, Xi'an, 710072, China; The National Engineering Laboratory for Integrated Aerospace-Ground-Ocean Big Data Application Technology, Xi'an, 710072, China; School of Computer Science, Research and Development Institute of Northwestern Polytechnical University in Shenzhen, Shenzhen, 518000, China.
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2
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Basu S, Mitra S, Singh O, Chandramohan B, Singru PS. Secretagogin in the brain and pituitary of the catfish, Clarias batrachus: Molecular characterization and regulation by insulin. J Comp Neurol 2022; 530:1743-1772. [PMID: 35322425 DOI: 10.1002/cne.25311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 02/02/2022] [Accepted: 02/04/2022] [Indexed: 11/12/2022]
Abstract
Secretagogin (scgn), is a novel hexa EF-hand, phylogenetically conserved calcium-binding protein. It serves as Ca2+ sensor and participates in Ca2+ -signaling and neuroendocrine regulation in mammals. However, its relevance in the brain of non-mammalian vertebrates has largely remained unexplored. To address this issue, we studied the cDNA encoding scgn, scgn mRNA expression, and distribution of scgn-equipped elements in the brain and pituitary of a teleost, Clarias batrachus (cb). The cbscgn cDNA consists of three transcripts (T) variants: T1 (2185 bp), T2 (2151 bp) and T3 (2060 bp). While 816 bp ORF in T1 and T2 encodes highly conserved six EF-hand 272 aa protein fully capable of Ca2+ -binding, 726-bp ORF in T3 encodes 242 aa protein. The T1 showed >90% and >70% identity with scgn of catfishes, and other teleosts and mammals, respectively. The T1-mRNA was widely expressed in the brain and pituitary, while the expression of T3 was restricted to the telencephalon. Application of the anti-scgn antiserum revealed a ∼32 kDa scgn-immunoreactive (scgn-i) band (known molecular weight of scgn) in the forebrain tissue, and immunohistochemically labeled neurons in the olfactory epithelium and bulb, telencephalon, preoptic area, hypothalamus, thalamus, and hindbrain. In the pituitary, scgn-i cells were seen in the pars distalis and intermedia. Insulin is reported to regulate scgn mRNA in the mammalian hippocampus, and feeding-related neuropeptides in the telencephalon of teleost. Intracranial injection of insulin significantly increased T1-mRNA expression and scgn-immunoreactivity in the telencephalon. We suggest that scgn may be an important player in the regulation of olfactory, neuroendocrine system, and energy balance functions in C. batrachus.
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Affiliation(s)
- Sumela Basu
- School of Biological Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar, India.,Homi Bhabha National Institute (HBNI), Mumbai, India
| | - Saptarsi Mitra
- School of Biological Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar, India.,Homi Bhabha National Institute (HBNI), Mumbai, India
| | - Omprakash Singh
- School of Biological Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar, India.,Homi Bhabha National Institute (HBNI), Mumbai, India
| | - Bathrachalam Chandramohan
- School of Biological Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar, India
| | - Praful S Singru
- School of Biological Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar, India.,Homi Bhabha National Institute (HBNI), Mumbai, India
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3
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Zibolka J, Bähr I, Peschke E, Mühlbauer E, Bazwinsky-Wutschke I. Human and Rodent Cell Lines as Models of Functional Melatonin-Responsive Pancreatic Islet Cells. Methods Mol Biol 2022; 2550:329-352. [PMID: 36180704 DOI: 10.1007/978-1-0716-2593-4_35] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Cell culture of different pancreatic islet cell lines, like the murine α-cell line αTC1.9, the rat β-cell lines INS-1 and INS-1 832/13, and the human δ-cell line QGP-1, can serve as valuable cell models for the analysis of melatonin-dependent modulation of hormone secretion. The paper summarizes in detail the requirements of culture for each cell line and includes batch protocols to stimulate hormone secretion and to treat cells with several melatonin concentrations as previously published. We here describe the processing of collected cell pellets or cell culture supernatants as well as different methods to analyze cell experiments after melatonin treatment on the basis of our own experience. Finally, we outlined for each cell line under which conditions the melatonin treatment should be performed to gain reproducible results.
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Affiliation(s)
- Juliane Zibolka
- Institute of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Ina Bähr
- Institute of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Elmar Peschke
- Institute of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Eckhard Mühlbauer
- Saxon Academy of Sciences and Humanities in Leipzig, Leipzig, Germany
| | - Ivonne Bazwinsky-Wutschke
- Institute of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany.
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4
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Yang J, Lv Y, Zhao Z, Li W, Xiang S, Zhou L, Gao A, Yan B, Ou L, Ling H, Xiao X, Liu J. A microRNA‑24‑to‑secretagogin regulatory pathway mediates cholesterol‑induced inhibition of insulin secretion. Int J Mol Med 2019; 44:608-616. [PMID: 31173188 PMCID: PMC6605698 DOI: 10.3892/ijmm.2019.4224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 05/20/2019] [Indexed: 12/16/2022] Open
Abstract
Hypercholesterolemia is a key factor leading to β‑cell dysfunction, but its underlying mechanisms remain unclear. Secretagogin (Scgn), a Ca2+ sensor protein that is expressed at high levels in the islets, has been shown to play a key role in regulating insulin secretion through effects on the soluble N‑ethylmaleimide‑sensitive factor attachment receptor protein complexes. However, further studies are required to determine whether Scgn plays a role in hypercholesterolemia‑associated β‑cell dysfunction. The present study investigated the involvement of a microRNA‑24 (miR‑24)‑to‑Scgn regulatory pathway in cholesterol‑induced β‑cell dysfunction. In the present study, MIN6 cells were treated with increasing concentrations of cholesterol and then, the cellular functions and changes in the miR‑24‑to‑Scgn signal pathway were observed. Excessive uptake of cholesterol in MIN6 cells increased the expression of miR‑24, resulting in a reduction in Sp1 expression by directly targeting its 3' untranslated region. As a transcriptional activator of Scgn, downregulation of Sp1 decreased Scgn levels and subsequently decreased the phosphorylation of focal adhesion kinase and paxillin, which is regulated by Scgn. Therefore, the focal adhesions in insulin granules were impaired and insulin exocytosis was reduced. The present study concluded that a miR‑24‑to‑Scgn pathway participates in the mechanism regulating cholesterol accumulation‑induced β‑cell dysfunction.
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Affiliation(s)
- Jing Yang
- Department of Endocrinology, The First Affiliated Hospital of The University of South China, Hengyang, Hunan 421001, P.R. China
| | - Yuncheng Lv
- Laboratory of Clinical Anatomy and Reproductive Medicine, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Zhibo Zhao
- Department of Endocrinology, The First Affiliated Hospital of The University of South China, Hengyang, Hunan 421001, P.R. China
| | - Wu Li
- Department of Endocrinology, The First Affiliated Hospital of The University of South China, Hengyang, Hunan 421001, P.R. China
| | - Sunmin Xiang
- Department of Endocrinology, The First Affiliated Hospital of The University of South China, Hengyang, Hunan 421001, P.R. China
| | - Lingzhi Zhou
- Department of Paediatrics, The First Affiliated Hospital of The University of South China, Hengyang, Hunan 421001, P.R. China
| | - Anbo Gao
- Laboratory of Clinical Anatomy and Reproductive Medicine, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Bin Yan
- Department of Endocrinology, The First Affiliated Hospital of The University of South China, Hengyang, Hunan 421001, P.R. China
| | - Lingling Ou
- Department of Endocrinology, The First Affiliated Hospital of The University of South China, Hengyang, Hunan 421001, P.R. China
| | - Hong Ling
- Emergency Surgery, The First Affiliated Hospital of The University of South China, Hengyang, Hunan 421001, P.R. China
| | - Xinhua Xiao
- Department of Endocrinology, The First Affiliated Hospital of The University of South China, Hengyang, Hunan 421001, P.R. China
| | - Jianghua Liu
- Department of Endocrinology, The First Affiliated Hospital of The University of South China, Hengyang, Hunan 421001, P.R. China
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5
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Sharma AK, Khandelwal R, Sharma Y. Veiled Potential of Secretagogin in Diabetes: Correlation or Coincidence? Trends Endocrinol Metab 2019; 30:234-243. [PMID: 30772140 DOI: 10.1016/j.tem.2019.01.007] [Citation(s) in RCA: 10] [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: 11/09/2018] [Revised: 01/18/2019] [Accepted: 01/22/2019] [Indexed: 12/19/2022]
Abstract
Secretagogin (SCGN) is a calcium sensor protein enriched in neuroendocrine cells in general and pancreatic β-cells in particular. SCGN regulates insulin secretion through several Ca2+-dependent interactions. Recent studies implicate SCGN in the β-cell physiology and extracellular insulin function, making it an intriguing candidate in diabetes research. Here, we propose a conjoining theme of diversified SCGN function in diabetes pathology. In our opinion, SCGN is an attractive therapeutic candidate ascribed by its role in β-cell maintenance and neuronal functions and in the efficacy of insulin. To scrutinize the therapeutic prospects of SCGN, we abridge putative diabetes-related properties of SCGN and put forth strategies to determine the precise role of SCGN in the pathogenesis/preclusion of diabetes.
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Affiliation(s)
- Anand Kumar Sharma
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad-500 007, India.
| | - Radhika Khandelwal
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad-500 007, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Yogendra Sharma
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad-500 007, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India.
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Malenczyk K, Szodorai E, Schnell R, Lubec G, Szabó G, Hökfelt T, Harkany T. Secretagogin protects Pdx1 from proteasomal degradation to control a transcriptional program required for β cell specification. Mol Metab 2018; 14:108-120. [PMID: 29910119 PMCID: PMC6034064 DOI: 10.1016/j.molmet.2018.05.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 05/30/2018] [Accepted: 05/31/2018] [Indexed: 02/07/2023] Open
Abstract
OBJECTIVE Specification of endocrine cell lineages in the developing pancreas relies on extrinsic signals from non-pancreatic tissues, which initiate a cell-autonomous sequence of transcription factor activation and repression switches. The steps in this pathway share reliance on activity-dependent Ca2+ signals. However, the mechanisms by which phasic Ca2+ surges become converted into a dynamic, cell-state-specific and physiologically meaningful code made up by transcription factors constellations remain essentially unknown. METHODS We used high-resolution histochemistry to explore the coincident expression of secretagogin and transcription factors driving β cell differentiation. Secretagogin promoter activity was tested in response to genetically manipulating Pax6 and Pax4 expression. Secretagogin null mice were produced with their pancreatic islets morphologically and functionally characterized during fetal development. A proteomic approach was utilized to identify the Ca2+-dependent interaction of secretagogin with subunits of the 26S proteasome and verified in vitro by focusing on Pdx1 retention. RESULTS Here, we show that secretagogin, a Ca2+ sensor protein that controls α and β cell turnover in adult, is in fact expressed in endocrine pancreas from the inception of lineage segregation in a Pax4-and Pax6-dependent fashion. By genetically and pharmacologically manipulating secretagogin expression and interactome engagement in vitro, we find secretagogin to gate excitation-driven Ca2+ signals for β cell differentiation and insulin production. Accordingly, secretagogin-/- fetuses retain a non-committed pool of endocrine progenitors that co-express both insulin and glucagon. We identify the Ca2+-dependent interaction of secretagogin with subunits of the 26S proteasome complex to prevent Pdx1 degradation through proteasome inactivation. This coincides with retained Nkx6.1, Pax4 and insulin transcription in prospective β cells. CONCLUSIONS In sum, secretagogin scales the temporal availability of a Ca2+-dependent transcription factor network to define β cell identity.
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Affiliation(s)
- Katarzyna Malenczyk
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, A-1090, Vienna, Austria; Department of Neuroscience, Karolinska Institutet, Retzius väg 8, SE-17177, Stockholm, Sweden
| | - Edit Szodorai
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, A-1090, Vienna, Austria; Paracelsus Medical University, Strubergasse 21, A-5020, Salzburg, Austria
| | - Robert Schnell
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheeles väg 2, SE-17177, Stockholm, Sweden
| | - Gert Lubec
- Paracelsus Medical University, Strubergasse 21, A-5020, Salzburg, Austria
| | - Gábor Szabó
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony utca 43, H-1083, Budapest, Hungary
| | - Tomas Hökfelt
- Department of Neuroscience, Karolinska Institutet, Retzius väg 8, SE-17177, Stockholm, Sweden
| | - Tibor Harkany
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, A-1090, Vienna, Austria; Department of Neuroscience, Karolinska Institutet, Retzius väg 8, SE-17177, Stockholm, Sweden.
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7
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Hansson SF, Zhou AX, Vachet P, Eriksson JW, Pereira MJ, Skrtic S, Jongsma Wallin H, Ericsson-Dahlstrand A, Karlsson D, Ahnmark A, Sörhede Winzell M, Magnone MC, Davidsson P. Secretagogin is increased in plasma from type 2 diabetes patients and potentially reflects stress and islet dysfunction. PLoS One 2018; 13:e0196601. [PMID: 29702679 PMCID: PMC5922551 DOI: 10.1371/journal.pone.0196601] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 04/16/2018] [Indexed: 01/09/2023] Open
Abstract
Beta cell dysfunction accompanies and drives the progression of type 2 diabetes mellitus (T2D), but there are few clinical biomarkers available to assess islet cell stress in humans. Secretagogin, a protein enriched in pancreatic islets, demonstrates protective effects on beta cell function in animals. However, its potential as a circulating biomarker released from human beta cells and islets has not been studied. In this study primary human islets, beta cells and plasma samples were used to explore secretion and expression of secretagogin in relation to the T2D pathology. Secretagogin was abundantly and specifically expressed and secreted from human islets. Furthermore, T2D patients had an elevated plasma level of secretagogin compared with matched healthy controls, which was confirmed in plasma of diabetic mice transplanted with human islets. Additionally, the plasma secretagogin level of the human cohort had an inverse correlation to clinical assessments of beta cell function. To explore the mechanism of secretagogin release in vitro, human beta cells (EndoC-βH1) were exposed to elevated glucose or cellular stress-inducing agents. Secretagogin was not released in parallel with glucose stimulated insulin release, but was markedly elevated in response to endoplasmic reticulum stressors and cytokines. These findings indicate that secretagogin is a potential novel biomarker, reflecting stress and islet cell dysfunction in T2D patients.
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Affiliation(s)
- Sara F. Hansson
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
- * E-mail:
| | - Alex-Xianghua Zhou
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Paulina Vachet
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Jan W. Eriksson
- Department of Medical Sciences, Clinical Diabetes and Metabolism, Uppsala University, Uppsala, Sweden
| | - Maria J. Pereira
- Department of Medical Sciences, Clinical Diabetes and Metabolism, Uppsala University, Uppsala, Sweden
| | - Stanko Skrtic
- Translational Medicine Unit CVRM, Early Clinical Development, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
- Institute of Medicine at Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | | | | | - Daniel Karlsson
- Bioscience, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Andrea Ahnmark
- Bioscience, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Maria Sörhede Winzell
- Bioscience, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Maria Chiara Magnone
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Pia Davidsson
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
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Malenczyk K, Girach F, Szodorai E, Storm P, Segerstolpe Å, Tortoriello G, Schnell R, Mulder J, Romanov RA, Borók E, Piscitelli F, Di Marzo V, Szabó G, Sandberg R, Kubicek S, Lubec G, Hökfelt T, Wagner L, Groop L, Harkany T. A TRPV1-to-secretagogin regulatory axis controls pancreatic β-cell survival by modulating protein turnover. EMBO J 2017; 36:2107-2125. [PMID: 28637794 PMCID: PMC5510001 DOI: 10.15252/embj.201695347] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 04/27/2017] [Accepted: 05/09/2017] [Indexed: 12/20/2022] Open
Abstract
Ca2+-sensor proteins are generally implicated in insulin release through SNARE interactions. Here, secretagogin, whose expression in human pancreatic islets correlates with their insulin content and the incidence of type 2 diabetes, is shown to orchestrate an unexpectedly distinct mechanism. Single-cell RNA-seq reveals retained expression of the TRP family members in β-cells from diabetic donors. Amongst these, pharmacological probing identifies Ca2+-permeable transient receptor potential vanilloid type 1 channels (TRPV1) as potent inducers of secretagogin expression through recruitment of Sp1 transcription factors. Accordingly, agonist stimulation of TRPV1s fails to rescue insulin release from pancreatic islets of glucose intolerant secretagogin knock-out(-/-) mice. However, instead of merely impinging on the SNARE machinery, reduced insulin availability in secretagogin-/- mice is due to β-cell loss, which is underpinned by the collapse of protein folding and deregulation of secretagogin-dependent USP9X deubiquitinase activity. Therefore, and considering the desensitization of TRPV1s in diabetic pancreata, a TRPV1-to-secretagogin regulatory axis seems critical to maintain the structural integrity and signal competence of β-cells.
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Affiliation(s)
- Katarzyna Malenczyk
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Fatima Girach
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Edit Szodorai
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Petter Storm
- Department of Clinical Sciences, Diabetes and Endocrinology CRC, Skåne University Hospital Malmö, Malmö, Sweden
| | - Åsa Segerstolpe
- Integrated Cardio Metabolic Centre, Karolinska Institutet, Huddinge, Sweden
| | | | - Robert Schnell
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Jan Mulder
- Science for Life Laboratory, Karolinska Institutet, Solna, Sweden
| | - Roman A Romanov
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Erzsébet Borók
- Department of Cognitive Neurobiology, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Fabiana Piscitelli
- Endocannabinoid Research Group, Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche, Pozzuoli Naples, Italy
| | - Vincenzo Di Marzo
- Endocannabinoid Research Group, Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche, Pozzuoli Naples, Italy
| | - Gábor Szabó
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Rickard Sandberg
- Integrated Cardio Metabolic Centre, Karolinska Institutet, Huddinge, Sweden
| | - Stefan Kubicek
- CeMM Research Centre for Molecular Medicine, Vienna, Austria
| | - Gert Lubec
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | - Tomas Hökfelt
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Ludwig Wagner
- University Clinic for Internal Medicine III, General Hospital Vienna, Vienna, Austria
| | - Leif Groop
- Department of Clinical Sciences, Diabetes and Endocrinology CRC, Skåne University Hospital Malmö, Malmö, Sweden
| | - Tibor Harkany
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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9
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SUMOylation and calcium control syntaxin-1A and secretagogin sequestration by tomosyn to regulate insulin exocytosis in human ß cells. Sci Rep 2017; 7:248. [PMID: 28325894 PMCID: PMC5428262 DOI: 10.1038/s41598-017-00344-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 02/22/2017] [Indexed: 11/09/2022] Open
Abstract
Insulin secretion from pancreatic ß cells is a multistep process that requires the coordination of exocytotic proteins that integrate diverse signals. These include signals derived from metabolic control of post-translational SUMOylation and depolarization-induced rises in intracellular Ca2+. Here we show that tomosyn, which suppresses insulin exocytosis by binding syntaxin1A, does so in a manner which requires its SUMOylation. Glucose-dependent de-SUMOylation of tomosyn1 at K298 releases syntaxin1A and controls the amplification of exocytosis in concert with a recently-identified tomosyn1-interacting partner; the Ca2+-binding protein secretagogin, which dissociates from tomosyn1 in response to Ca2+-raising stimuli and is required for insulin granule trafficking and exocytosis downstream of Ca2+ influx. Together our results suggest that tomosyn acts as a key signaling hub in insulin secretion by integrating signals mediated by metabolism-dependent de-SUMOylation and electrically-induced entry of Ca2+ to regulate the availability of exocytotic proteins required for the amplification of insulin secretion.
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10
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Khandelwal R, Sharma AK, Chadalawada S, Sharma Y. Secretagogin Is a Redox-Responsive Ca2+ Sensor. Biochemistry 2017; 56:411-420. [DOI: 10.1021/acs.biochem.6b00761] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Radhika Khandelwal
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
- Academy of Scientific and Innovative Research (AcSIR), New Delhi, India
| | - Anand Kumar Sharma
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Swathi Chadalawada
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
| | - Yogendra Sharma
- CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, Hyderabad 500 007, India
- Academy of Scientific and Innovative Research (AcSIR), New Delhi, India
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Offenborn JN, Waadt R, Kudla J. Visualization and translocation of ternary Calcineurin-A/Calcineurin-B/Calmodulin-2 protein complexes by dual-color trimolecular fluorescence complementation. THE NEW PHYTOLOGIST 2015; 208:269-79. [PMID: 25919910 DOI: 10.1111/nph.13439] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 03/31/2015] [Indexed: 06/04/2023]
Abstract
Fluorescence complementation (FC) techniques are expedient for analyzing bimolecular protein-protein interactions. Here we aimed to develop a method for visualization of ternary protein complexes using dual-color trimolecular fluorescence complementation (TriFC). Dual-color TriFC combines protein fragments of mCherry and mVenus, in which a scaffold protein is bilaterally fused to C-terminal fragments of both fluorescent proteins and combined with potential interacting proteins fused to an N-terminal fluorescent protein fragment. For efficient visual verification of ternary complex formation, TriFC was combined with a cytoplasm to plasma membrane translocation assay. Modular vector sets were designed which are fully compatible with previously reported bimolecular fluorescence complementation (BiFC) vectors. As a proof-of-principle, the ternary complex formation of the PP2B protein phosphatase Calcineurin-A/Calcineurin-B with Calmodulin-2 was investigated in transiently transformed Nicotiana benthamiana leaf epidermal cells. The results indicate a Calcineurin-B-induced interaction of Calmodulin-2 with Calcineurin-A. TriFC and the translocation of TriFC complexes provide a novel tool to investigate ternary complex formations with the simplicity of a BiFC approach. The robustness of FC applications and the opportunity to quantify fluorescence complementation render this assay suitable for a broad range of interaction analyses.
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Affiliation(s)
- Jan Niklas Offenborn
- Institut für Biologie und Biotechnologie der Pflanzen, Universität Münster, Schlossplatz 7, Münster, 48149, Germany
| | - Rainer Waadt
- Institut für Biologie und Biotechnologie der Pflanzen, Universität Münster, Schlossplatz 7, Münster, 48149, Germany
- Plant Developmental Biology, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 230, Heidelberg, 69120, Germany
| | - Jörg Kudla
- Institut für Biologie und Biotechnologie der Pflanzen, Universität Münster, Schlossplatz 7, Münster, 48149, Germany
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12
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Peschke E, Bähr I, Mühlbauer E. Experimental and clinical aspects of melatonin and clock genes in diabetes. J Pineal Res 2015; 59:1-23. [PMID: 25904189 DOI: 10.1111/jpi.12240] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 04/20/2015] [Indexed: 12/15/2022]
Abstract
The pineal hormone melatonin influences insulin secretion, as well as glucagon and somatostatin secretion, both in vivo and in vitro. These effects are mediated by two specific, high-affinity, seven transmembrane, pertussis toxin-sensitive, Gi-protein-coupled melatonin receptors, MT1 and MT2. Both isoforms are expressed in the β-cells, α-cells as well as δ-cells of the pancreatic islets of Langerhans and are involved in the modulation of insulin secretion, leading to inhibition of the adenylate cyclase-dependent cyclic adenosine monophosphate as well as cyclic guanosine monophosphate formation in pancreatic β-cells by inhibiting the soluble guanylate cyclase, probably via MT2 receptors. In this way, melatonin also likely inhibits insulin secretion, whereas using the inositol triphosphate pathway after previous blocking of Gi-proteins by pertussis toxin, melatonin increases insulin secretion. Desynchrony of receptor signaling may lead to the development of type 2 diabetes. This notion has recently been supported by genomewide association studies pinpointing variances of the MT2 receptor as a risk factor for this rapidly spreading metabolic disturbance. As melatonin is secreted in a clearly diurnal fashion, it is safe to assume that it also has a diurnal impact on the blood-glucose-regulating function of the islet. Observations of the circadian expression of clock genes (Clock, Bmal1, Per1,2,3, and Cry1,2) in pancreatic islets, as well as in INS1 rat insulinoma cells, may indicate that circadian rhythms are generated in the β-cells themselves. The circadian secretion of insulin from pancreatic islets is clock-driven. Disruption of circadian rhythms and clock function leads to metabolic disturbances, for example, type 2 diabetes. The study of melatonin-insulin interactions in diabetic rat models has revealed an inverse relationship between these two hormones. Both type 2 diabetic rats and patients exhibit decreased melatonin levels and slightly increased insulin levels, whereas type 1 diabetic rats show extremely reduced levels or the absence of insulin, but statistically significant increases in melatonin levels. Briefly, an increase in melatonin levels leads to a decrease in stimulated insulin secretion and vice versa. Melatonin levels in blood plasma, as well as the activity of the key enzyme of melatonin synthesis, AA-NAT (arylalkylamine-N-acetyltransferase) in pineal, are lower in type 2 diabetic rats compared to controls. In contrast, melatonin and pineal AA-NAT mRNA are increased and insulin receptor mRNA is decreased in type 1 diabetic rats, which also indicates a close relationship between insulin and melatonin. As an explanation, it was hypothesized that catecholamines, which reduce insulin levels and stimulate melatonin synthesis, control insulin-melatonin interactions. This conviction stems from the observation that catecholamines are increased in type 1 but are diminished in type 2 diabetes. In this context, another important line of inquiry involves the fact that melatonin protects β-cells against functional overcharge and, consequently, hinders the development of type 2 diabetes.
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Affiliation(s)
| | - Ina Bähr
- Institute of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Halle, Germany
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13
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Christensen GL, Jacobsen MLB, Wendt A, Mollet IG, Friberg J, Frederiksen KS, Meyer M, Bruun C, Eliasson L, Billestrup N. Bone morphogenetic protein 4 inhibits insulin secretion from rodent beta cells through regulation of calbindin1 expression and reduced voltage-dependent calcium currents. Diabetologia 2015; 58:1282-90. [PMID: 25828920 DOI: 10.1007/s00125-015-3568-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 03/04/2015] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS Type 2 diabetes is characterised by progressive loss of pancreatic beta cell mass and function. Therefore, it is of therapeutic interest to identify factors with the potential to improve beta cell proliferation and insulin secretion. Bone morphogenetic protein 4 (BMP4) expression is increased in diabetic animals and BMP4 reduces glucose-stimulated insulin secretion (GSIS). Here, we investigate the molecular mechanism behind this inhibition. METHODS BMP4-mediated inhibition of GSIS was investigated in detail using single cell electrophysiological measurements and live cell Ca(2+) imaging. BMP4-mediated gene expression changes were investigated by microarray profiling, quantitative PCR and western blotting. RESULTS Prolonged exposure to BMP4 reduced GSIS from rodent pancreatic islets. This inhibition was associated with decreased exocytosis due to a reduced Ca(2+) current through voltage-dependent Ca(2+) channels. To identify proteins involved in the inhibition of GSIS, we investigated global gene expression changes induced by BMP4 in neonatal rat pancreatic islets. Expression of the Ca(2+)-binding protein calbindin1 was significantly induced by BMP4. Overexpression of calbindin1 in primary islet cells reduced GSIS, and the effect of BMP4 on GSIS was lost in islets from calbindin1 (Calb1) knockout mice. CONCLUSIONS/INTERPRETATION We found BMP4 treatment to markedly inhibit GSIS from rodent pancreatic islets in a calbindin1-dependent manner. Calbindin1 is suggested to mediate the effect of BMP4 by buffering Ca(2+) and decreasing Ca(2+) channel activity, resulting in diminished insulin exocytosis. Both BMP4 and calbindin1 are potential pharmacological targets for the treatment of beta cell dysfunction.
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Affiliation(s)
- Gitte L Christensen
- Department of Biomedical Sciences, University of Copenhagen, Nørre Alle 20, 2100, Copenhagen, Denmark
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14
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Expression of nucleobindin 1 (NUCB1) in pancreatic islets and other endocrine tissues. Cell Tissue Res 2014; 358:331-42. [DOI: 10.1007/s00441-014-1948-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 06/06/2014] [Indexed: 01/01/2023]
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15
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Bazwinsky-Wutschke I, Mühlbauer E, Albrecht E, Peschke E. Calcium-signaling components in rat insulinoma β-cells (INS-1) and pancreatic islets are differentially influenced by melatonin. J Pineal Res 2014; 56:439-49. [PMID: 24650091 DOI: 10.1111/jpi.12135] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 03/14/2014] [Indexed: 11/28/2022]
Abstract
The pineal secretory product melatonin exerts its influence on the insulin secretion of pancreatic islets by different signaling pathways. The purpose of this study was to analyze the impact of melatonin on calcium-signaling components under different conditions. In a transfected INS-1 cell line overexpressing the human MT2 receptor (hMT2-INS-1), melatonin treatment induced even stronger depressive effects on calcium/calmodulin-dependent kinase 2d and IV (Camk2d, CamkIV) transcripts during 3-isobutyl-1-methylxanthine (IBMX) treatment than in normal INS-1 cells, indicating a crucial influence of melatonin receptor density on transcript-level regulation. In addition, melatonin induced a significant downregulation of calmodulin (Calm1) in IBMX-treated hMT2-INS-1 cells. Long-term administration of melatonin alone reduced CamkIV transcript levels in INS-1 cells; however, transcript levels of Camk2d remained unchanged. The release of insulin was diminished under long-term melatonin treatment. The impact of melatonin also involved reductions in CAMK2D protein during IBMX or forskolin treatments in INS-1 cells, as measured by an enzyme-linked immunosorbent assay, indicating a functional significance of transcriptional changes in pancreatic islets. Furthermore, analysis of melatonin receptor knockout mice showed that the transcript levels of Camk2d, CamkIV, and Calm1 were differentially influenced according to the melatonin receptor subtype deleted. In conclusion, this study provides evidence that melatonin has different impacts on the regulation of Calm1 and Camk. These calcium-signaling components are known as participants in the calcium/calmodulin pathway, which plays an important functional role in the modulation of the β-cell signaling pathways leading to insulin secretion.
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16
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Bazwinsky-Wutschke I, Bieseke L, Mühlbauer E, Peschke E. Influence of melatonin receptor signalling on parameters involved in blood glucose regulation. J Pineal Res 2014; 56:82-96. [PMID: 24117965 DOI: 10.1111/jpi.12100] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 09/20/2013] [Indexed: 12/18/2022]
Abstract
The pineal hormone melatonin is known to influence insulin secretion via the G-protein-coupled receptor isoforms MT1 and MT2. The present study was aimed to further elucide the impact of melatonin on blood glucose regulation. To this end, mouse lines were used, in which one of the two or both melatonin receptors were deleted. In comparison with wild-type mice of the same age (8-12 months old), increased plasma insulin and melatonin levels and decreased blood glucose levels and body weights were detected in the MT1- and double-knockout lines. The elimination of melatonin receptor signalling also altered blood glucose concentrations, body weight and melatonin and insulin levels when comparing wild-type and receptor knockout mice of different ages (6 wk and 8-12 months old); such changes, however, were dependent on the type of receptor deleted. Furthermore, reverse transcription polymerase chain reaction results provided evidence that melatonin receptor deficiency has an impact on transcript levels of pancreatic islet hormones as well as on pancreatic and hepatic glucose transporters (Glut1 and 2). Under stimulated insulin secretion in the presence of melatonin in the rat insulinoma β-cells INS-1, the Glut1 transcript level was decreased. In conclusion, the present findings demonstrate that melatonin receptor knockout types affect blood glucose levels, body weight, plasma levels of melatonin and insulin, as well as pancreatic hormone and Glut1 expression in significantly different manners.
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MESH Headings
- Analysis of Variance
- Animals
- Blood Glucose/genetics
- Blood Glucose/metabolism
- Body Weight/genetics
- Cell Line, Tumor
- Female
- Glucagon/analysis
- Glucagon/genetics
- Glucagon/metabolism
- Glucose Transporter Type 1/analysis
- Glucose Transporter Type 1/genetics
- Glucose Transporter Type 1/metabolism
- Insulin/blood
- Male
- Melatonin/blood
- Mice
- Mice, Knockout
- Organ Specificity
- RNA, Messenger/analysis
- RNA, Messenger/genetics
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/metabolism
- Somatostatin/analysis
- Somatostatin/genetics
- Somatostatin/metabolism
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17
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Mahmazi S, Parivar K, Rahnema M, Ohadi M. Calreticulin novel mutations in type 2 diabetes mellitus. Int J Diabetes Dev Ctries 2013. [DOI: 10.1007/s13410-013-0152-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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18
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Bazwinsky-Wutschke I, Wolgast S, Mühlbauer E, Albrecht E, Peschke E. Phosphorylation of cyclic AMP-response element-binding protein (CREB) is influenced by melatonin treatment in pancreatic rat insulinoma β-cells (INS-1). J Pineal Res 2012; 53:344-57. [PMID: 22616931 DOI: 10.1111/j.1600-079x.2012.01004.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The pineal hormone melatonin exerts its influence on the insulin secretion of pancreatic islets by a variety of signalling pathways. The purpose of the present study was to analyse the impact of melatonin on the phosphorylated transcription factor cAMP-response element-binding protein (pCREB). In pancreatic rat insulinoma β-cells (INS-1), pCREB immunofluorescence intensities in cell nuclei using digitised confocal image analysis were measured to semi-quantify differences in the pCREB immunoreactivity (pCREB-ir) caused by different treatments. Increasing concentrations of forskolin or 3-isobutyl-1-methylxanthine (IBMX) resulted in a dose-dependent rise of the mean fluorescence intensity in pCREB-ir nuclear staining. Concomitant melatonin application significantly decreased pCREB-ir in INS-1 cells after 30-min, 1-hr and 3-hr treatment. The melatonin receptor antagonists luzindole and 4-phenyl-2-propionamidotetraline (4P-PDOT) completely abolished the pCREB phosphorylation-decreasing effect of melatonin, indicating that both melatonin receptor isoforms (MT(1) and MT(2)) are involved. In a transfected INS-1 cell line expressing the human MT(2) receptor, melatonin caused the greatest reduction in pCREB after IBMX treatment compared with nontransfected INS-1 cells, indicating a crucial influence of melatonin receptor density on pCREB regulation. Furthermore, the downregulation of pCREB by melatonin is concomitantly associated with a statistically significant downregulation of Camk2d transcript levels, as measured after 3 hr. In conclusion, the present study provides evidence that the phosphorylation level of CREB is modulated in pancreatic β-cells by melatonin. Mediated via CREB, melatonin regulates the expression of genes that play an important functional role in the regulation of β-cell signalling pathways.
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MESH Headings
- 1-Methyl-3-isobutylxanthine/pharmacology
- Animals
- Calcium-Calmodulin-Dependent Protein Kinase Type 2/genetics
- Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism
- Cell Line, Tumor
- Colforsin/pharmacology
- Cyclic AMP Response Element-Binding Protein/metabolism
- Dose-Response Relationship, Drug
- Fluorescent Antibody Technique
- Humans
- Insulin-Secreting Cells/drug effects
- Insulin-Secreting Cells/metabolism
- Insulinoma/genetics
- Insulinoma/metabolism
- Melatonin/pharmacology
- Microscopy, Confocal
- Pancreatic Neoplasms/genetics
- Pancreatic Neoplasms/metabolism
- Phosphorylation
- Rats
- Receptor, Melatonin, MT1/drug effects
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/drug effects
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/metabolism
- Signal Transduction/drug effects
- Tetrahydronaphthalenes/pharmacology
- Time Factors
- Transfection
- Tryptamines/pharmacology
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19
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Structural insights into the calcium-dependent interaction between calbindin-D28K and caspase-3. FEBS Lett 2012; 586:3582-9. [PMID: 22982862 DOI: 10.1016/j.febslet.2012.08.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 08/27/2012] [Accepted: 08/30/2012] [Indexed: 11/21/2022]
Abstract
The regulation of apoptosis involves a complicated cascade requiring numerous protein interactions including the pro-apoptotic executioner protein caspase-3 and the anti-apoptotic calcium-binding protein calbindin-D28K. Using isothermal titration calorimetry, we show that calbindin-D28K binds caspase-3 in a Ca(2+)-dependent fashion. Molecular docking and conformational sampling studies of the Ca(2+)-loaded capase-3/calbindin-D28K interaction were performed in order to isolate potentially crucial intermolecular contacts. Residues in the active site loops of caspase-3 and EF-hands 1 and 2 of calbindin-D28K were shown to be critical to the interaction. Based on these studies, a model is proposed to help understand how calbindin-D28K may deactivate caspase-3 upon binding.
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20
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Maj M, Milenkovic I, Bauer J, Berggård T, Veit M, Ilhan-Mutlu A, Wagner L, Tretter V. Novel insights into the distribution and functional aspects of the calcium binding protein secretagogin from studies on rat brain and primary neuronal cell culture. Front Mol Neurosci 2012; 5:84. [PMID: 22888312 PMCID: PMC3412267 DOI: 10.3389/fnmol.2012.00084] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 07/17/2012] [Indexed: 11/13/2022] Open
Abstract
Secretagogin is a calcium binding protein (CBP) highly expressed in neuroendocrine cells. It has been shown to be involved in insulin secretion from pancreatic beta cells and is a strong candidate as a biomarker for endocrine tumors, stroke, and eventually psychiatric conditions. Secretagogin has been hypothesized to exert a neuroprotective role in neurodegenerative diseases like Alzheimer's disease. The expression pattern of Secretagogin is not conserved from rodents to humans. We used brain tissue and primary neuronal cell cultures from rat to further characterize this CBP in rodents and to perform a few functional assays in vitro. Immunohistochemistry on rat brain slices revealed a high density of Secretagogin-positive cells in distinct brain regions. Secretagogin was found in the cytosol or associated with subcellular compartments. We tested primary neuronal cultures for their suitability as model systems to further investigate functional properties of Secretagogin. These cultures can easily be manipulated by treatment with drugs or by transfection with test constructs interfering with signaling cascades that might be linked to the cellular function of Secretagogin. We show that, like in pancreatic beta cells and insulinoma cell lines, also in neurons the expression level of Secretagogin is dependent on extracellular insulin and glucose. Further, we show also for rat brain neuronal tissue that Secretagogin interacts with the microtubule-associated protein Tau and that this interaction is dependent on Ca(2+). Future studies should aim to study in further detail the molecular properties and function of Secretagogin in individual neuronal cell types, in particular the subcellular localization and trafficking of this protein and a possible active secretion by neurons.
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Affiliation(s)
- Magdalena Maj
- Department of Internal Medicine III, Division of Nephrology and Dialysis, Medizinische Universität Wien Vienna, Austria
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21
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Mühlbauer E, Albrecht E, Hofmann K, Bazwinsky-Wutschke I, Peschke E. Melatonin inhibits insulin secretion in rat insulinoma β-cells (INS-1) heterologously expressing the human melatonin receptor isoform MT2. J Pineal Res 2011; 51:361-72. [PMID: 21585522 DOI: 10.1111/j.1600-079x.2011.00898.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Melatonin exerts some of its effects via G-protein-coupled membrane receptors. Two membrane receptor isoforms, MT1 and MT2, have been described. The MT1 receptor is known to inhibit second messenger cyclic adenosine monophosphate (cAMP) signaling through receptor-coupling to inhibitory G-proteins (G(i) ). Much less is known about the MT2 receptor, but it has also been implicated in signaling via G(i) -proteins. In rat pancreatic β-cells, it has recently been reported that the MT2 receptor plays an inhibitory role in the cyclic guanosine monophosphate (cGMP) pathway. This study addresses the signaling features of the constitutively expressed human recombinant MT2 receptor (hMT2) and its impact on insulin secretion, using a rat insulinoma β-cell line (INS-1). On the basis of a specific radioimmunoassay, insulin secretion was found to be more strongly reduced in the clones expressing hMT2 than in INS-1 controls, when incubated with 1 or 100 nm melatonin. Similarly, cAMP and cGMP levels, measured by specific enzyme-linked immunosorbent assays (ELISAs), were reduced to a greater extent in hMT2 clones after melatonin treatment. In hMT2-expressing cells, the inhibitory effect of melatonin on insulin secretion was blocked by pretreatment with pertussis toxin, demonstrating the coupling of the hMT2 to G(i) -proteins. These results indicate that functional hMT2 expression leads to the inhibition of cyclic nucleotide signaling and a reduction in insulin release. Because genetic variants of the hMT2 receptor are considered to be risk factors in the development of type 2 diabetes, our results are potentially significant in explaining and preventing the pathogenesis of this disease.
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22
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Hübner S, Efthymiadis A. Histochemistry and cell biology: the annual review 2010. Histochem Cell Biol 2011; 135:111-40. [PMID: 21279376 DOI: 10.1007/s00418-011-0781-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/12/2011] [Indexed: 10/18/2022]
Abstract
This review summarizes recent advances in histochemistry and cell biology which complement and extend our knowledge regarding various aspects of protein functions, cell and tissue biology, employing appropriate in vivo model systems in conjunction with established and novel approaches. In this context several non-expected results and discoveries were obtained which paved the way of research into new directions. Once the reader embarks on reading this review, it quickly becomes quite obvious that the studies contribute not only to a better understanding of fundamental biological processes but also provide use-oriented aspects that can be derived therefrom.
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Affiliation(s)
- Stefan Hübner
- Institute of Anatomy and Cell Biology, University of Würzburg, Koellikerstrasse 6, 97070 Würzburg, Germany.
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