1
|
Štepihar D, Florke Gee RR, Hoyos Sanchez MC, Fon Tacer K. Cell-specific secretory granule sorting mechanisms: the role of MAGEL2 and retromer in hypothalamic regulated secretion. Front Cell Dev Biol 2023; 11:1243038. [PMID: 37799273 PMCID: PMC10548473 DOI: 10.3389/fcell.2023.1243038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 08/31/2023] [Indexed: 10/07/2023] Open
Abstract
Intracellular protein trafficking and sorting are extremely arduous in endocrine and neuroendocrine cells, which synthesize and secrete on-demand substantial quantities of proteins. To ensure that neuroendocrine secretion operates correctly, each step in the secretion pathways is tightly regulated and coordinated both spatially and temporally. At the trans-Golgi network (TGN), intrinsic structural features of proteins and several sorting mechanisms and distinct signals direct newly synthesized proteins into proper membrane vesicles that enter either constitutive or regulated secretion pathways. Furthermore, this anterograde transport is counterbalanced by retrograde transport, which not only maintains membrane homeostasis but also recycles various proteins that function in the sorting of secretory cargo, formation of transport intermediates, or retrieval of resident proteins of secretory organelles. The retromer complex recycles proteins from the endocytic pathway back to the plasma membrane or TGN and was recently identified as a critical player in regulated secretion in the hypothalamus. Furthermore, melanoma antigen protein L2 (MAGEL2) was discovered to act as a tissue-specific regulator of the retromer-dependent endosomal protein recycling pathway and, by doing so, ensures proper secretory granule formation and maturation. MAGEL2 is a mammalian-specific and maternally imprinted gene implicated in Prader-Willi and Schaaf-Yang neurodevelopmental syndromes. In this review, we will briefly discuss the current understanding of the regulated secretion pathway, encompassing anterograde and retrograde traffic. Although our understanding of the retrograde trafficking and sorting in regulated secretion is not yet complete, we will review recent insights into the molecular role of MAGEL2 in hypothalamic neuroendocrine secretion and how its dysregulation contributes to the symptoms of Prader-Willi and Schaaf-Yang patients. Given that the activation of many secreted proteins occurs after they enter secretory granules, modulation of the sorting efficiency in a tissue-specific manner may represent an evolutionary adaptation to environmental cues.
Collapse
Affiliation(s)
- Denis Štepihar
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
- Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Rebecca R. Florke Gee
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
| | - Maria Camila Hoyos Sanchez
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
| | - Klementina Fon Tacer
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
| |
Collapse
|
2
|
Zhao X, Ma Y, Shi M, Huang M, Xin J, Ci S, Chen M, Jiang T, Hu Z, He L, Pan F, Guo Z. Excessive iron inhibits insulin secretion via perturbing transcriptional regulation of SYT7 by OGG1. Cell Mol Life Sci 2023; 80:159. [PMID: 37209177 PMCID: PMC11072990 DOI: 10.1007/s00018-023-04802-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Revised: 05/08/2023] [Accepted: 05/08/2023] [Indexed: 05/22/2023]
Abstract
Although iron overload is closely related to the occurrence of type 2 diabetes mellitus (T2DM), the specific mechanism is unclear. Here, we found that excessive iron inhibited the secretion of insulin (INS) and impaired islet β cell function through downregulating Synaptotagmin 7 (SYT7) in iron overload model in vivo and in vitro. Our results further demonstrated that 8-oxoguanine DNA glycosylase (OGG1), a key protein in the DNA base excision repair, was an upstream regulator of SYT7. Interestingly, such regulation could be suppressed by excessive iron. Ogg1-null mice, iron overload mice and db/db mice exhibit reduced INS secretion, weakened β cell function and subsequently impaired glucose tolerance. Notably, SYT7 overexpression could rescue these phenotypes. Our data revealed an intrinsic mechanism by which excessive iron inhibits INS secretion through perturbing the transcriptional regulation of SYT7 by OGG1, which suggested that SYT7 was a potential target in clinical therapy for T2DM.
Collapse
Affiliation(s)
- Xingqi Zhao
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, 1 WenYuan Road, Nanjing, 210023, China
| | - Ying Ma
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, 1 WenYuan Road, Nanjing, 210023, China
| | - Munan Shi
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, 1 WenYuan Road, Nanjing, 210023, China
| | - Miaoling Huang
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, 1 WenYuan Road, Nanjing, 210023, China
| | - Jingyu Xin
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, 1 WenYuan Road, Nanjing, 210023, China
| | - Shusheng Ci
- School of Basic Medical Sciences, Nanjing Medical University, Nanjing, 211166, Jiangsu, China
| | - Meimei Chen
- Department of Endocrinology, The Second Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing, 210000, Jiangsu, China
| | - Tao Jiang
- Department of Geriatrics, The Second Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing, 210000, Jiangsu, China
| | - Zhigang Hu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, 1 WenYuan Road, Nanjing, 210023, China
| | - Lingfeng He
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, 1 WenYuan Road, Nanjing, 210023, China
| | - Feiyan Pan
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, 1 WenYuan Road, Nanjing, 210023, China.
| | - Zhigang Guo
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, 1 WenYuan Road, Nanjing, 210023, China.
| |
Collapse
|
3
|
Piekarska K, Bonowicz K, Grzanka A, Jaworski ŁM, Reiter RJ, Slominski AT, Steinbrink K, Kleszczyński K, Gagat M. Melatonin and TGF-β-Mediated Release of Extracellular Vesicles. Metabolites 2023; 13:metabo13040575. [PMID: 37110233 PMCID: PMC10142249 DOI: 10.3390/metabo13040575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 04/12/2023] [Accepted: 04/17/2023] [Indexed: 04/29/2023] Open
Abstract
The immune system, unlike other systems, must be flexible and able to "adapt" to fully cope with lurking dangers. The transition from intracorporeal balance to homeostasis disruption is associated with activation of inflammatory signaling pathways, which causes modulation of the immunology response. Chemotactic cytokines, signaling molecules, and extracellular vesicles act as critical mediators of inflammation and participate in intercellular communication, conditioning the immune system's proper response. Among the well-known cytokines allowing for the development and proper functioning of the immune system by mediating cell survival and cell-death-inducing signaling, the tumor necrosis factor α (TNF-α) and transforming growth factor β (TGF-β) are noteworthy. The high bloodstream concentration of those pleiotropic cytokines can be characterized by anti- and pro-inflammatory activity, considering the powerful anti-inflammatory and anti-oxidative stress capabilities of TGF-β known from the literature. Together with the chemokines, the immune system response is also influenced by biologically active chemicals, such as melatonin. The enhanced cellular communication shows the relationship between the TGF-β signaling pathway and the extracellular vesicles (EVs) secreted under the influence of melatonin. This review outlines the findings on melatonin activity on TGF-β-dependent inflammatory response regulation in cell-to-cell communication leading to secretion of the different EV populations.
Collapse
Affiliation(s)
- Klaudia Piekarska
- Department of Histology and Embryology, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, 85-092 Bydgoszcz, Poland
| | - Klaudia Bonowicz
- Department of Histology and Embryology, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, 85-092 Bydgoszcz, Poland
| | - Alina Grzanka
- Department of Histology and Embryology, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, 85-092 Bydgoszcz, Poland
| | - Łukasz M Jaworski
- Department of Histology and Embryology, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, 85-092 Bydgoszcz, Poland
| | - Russel J Reiter
- Department of Cell Systems and Anatomy, UT Health, Long School of Medicine, San Antonio, TX 78229, USA
| | - Andrzej T Slominski
- Department of Dermatology, Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA
- Pathology and Laboratory Medicine Service, VA Medical Center, Birmingham, AL 35294, USA
| | - Kerstin Steinbrink
- Department of Dermatology, University of Münster, Von-Esmarch-Str. 58, 48149 Münster, Germany
| | - Konrad Kleszczyński
- Department of Dermatology, University of Münster, Von-Esmarch-Str. 58, 48149 Münster, Germany
| | - Maciej Gagat
- Department of Histology and Embryology, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, 85-092 Bydgoszcz, Poland
| |
Collapse
|
4
|
Role of Melatonin in Daily Variations of Plasma Insulin Level and Pancreatic Clock Gene Expression in Chick Exposed to Monochromatic Light. Int J Mol Sci 2023; 24:ijms24032368. [PMID: 36768693 PMCID: PMC9916459 DOI: 10.3390/ijms24032368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/14/2023] [Accepted: 01/16/2023] [Indexed: 01/27/2023] Open
Abstract
To clarify the effect of monochromatic light on circadian rhythms of plasma insulin level and pancreatic clock gene expression and its mechanism, 216 newly hatched chicks were divided into three groups (intact, sham operation and pinealectomy) and were raised under white (WL), red (RL), green (GL) or blue (BL) light for 21 days. Their plasma and pancreas were sampled at six four-hour intervals. For circadian rhythm analysis, measurements of plasma melatonin, insulin, and clock gene expression (cClock, cBmal1, cBmal2, cCry1, cCry2, cPer2, and cPer3) were made. Plasma melatonin, insulin, and the pancreatic clock gene all expressed rhythmically in the presence of monochromatic light. Red light reduced the mesor and amplitude of plasma melatonin in comparison to green light. The mesor and amplitude of the pancreatic clock gene in chickens exposed to red light were dramatically reduced, which is consistent with the drop in plasma melatonin levels. Red light, on the other hand, clearly raised the level of plasma insulin via raising the expression of cVamp2, but not cInsulin. After the pineal gland was removed, the circadian expressions of plasma melatonin and pancreatic clock gene were significantly reduced, but the plasma insulin level and the pancreatic cVamp2 expression were obviously increased, resulting in the disappearance of differences in insulin level and cVamp2 expression in the monochromatic light groups. Therefore, we hypothesize that melatonin may be crucial in the effect of monochromatic light on the circadian rhythm of plasma insulin level by influencing the expression of clock gene in chicken pancreas.
Collapse
|
5
|
Zhao G, Xu H, Li H, Zhang J, Gao J, Cai M, Wang H, Shi Y, Wang H. Regulatory Mechanisms of SNAP-25-Associated Insulin Release Revealed by Live-Cell Confocal and Single-Molecule Localization Imaging. Anal Chem 2022; 94:15307-15314. [DOI: 10.1021/acs.analchem.2c02677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Guanfang Zhao
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China
- University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
| | - Haijiao Xu
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China
| | - Hongru Li
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China
- University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
| | - Jinrui Zhang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China
| | - Jing Gao
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China
| | - Mingjun Cai
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China
| | - Huili Wang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China
| | - Yan Shi
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China
| | - Hongda Wang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China
- University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong 266237, P. R. China
| |
Collapse
|
6
|
Dissanayake WC, Shepherd PR. β-cells retain a pool of insulin-containing secretory vesicles regulated by adherens junctions and the cadherin binding protein p120 catenin. J Biol Chem 2022; 298:102240. [PMID: 35809641 PMCID: PMC9358467 DOI: 10.1016/j.jbc.2022.102240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 06/16/2022] [Accepted: 06/17/2022] [Indexed: 11/03/2022] Open
Abstract
The β-cells of the islets of Langerhans are the sole producers of insulin in the human body. In response to rising glucose levels, insulin-containing vesicles inside β-cells fuse with the plasma membrane and release their cargo. However, the mechanisms regulating this process are only partly understood. Previous evidence indicated reductions in α-catenin elevate insulin release, while reductions in β-catenin decrease insulin release. α- and β-catenin contribute to cellular regulation in a range of ways but one is as members of the adherens junction complex and these contribute to the development of cell polarity in b-cells. Therefore, we investigated the effects of adherens junctions on insulin release. We show in INS-1E β-cells knockdown of either E- or N-cadherin had only small effects on insulin secretion, but simultaneous knockout of both cadherins resulted in a significant increase in basal insulin release to the same level as glucose-stimulated release. This double knockdown also significantly attenuated levels of p120 catenin, a cadherin binding partner involved in regulating cadherin turnover. Conversely, reducing p120 catenin levels with siRNA destabilized both E- and N-cadherin, and this was also associated with an increase in levels of insulin secreted from INS-1E cells. Furthermore, there were also changes in these cells consistent with higher insulin release, namely reductions in levels of F-actin and increased intracellular free Ca2+ levels in response to KCl-induced membrane depolarization. Taken together, these data provide evidence that adherens junctions play important roles in retaining a pool of insulin secretory vesicles within the cell and establish a role for p120 catenin in regulating this process.
Collapse
Affiliation(s)
- Waruni C Dissanayake
- Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Peter R Shepherd
- Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
| |
Collapse
|
7
|
Huang S, Liao X, Wu J, Zhang X, Li Y, Xiang D, Luo S. The microglial membrane receptor TREM2 mediates exosome secretion to promote phagocytosis of amyloid-β by microglia. FEBS Lett 2022; 596:1059-1071. [PMID: 35292963 DOI: 10.1002/1873-3468.14336] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/03/2022] [Accepted: 03/04/2022] [Indexed: 11/06/2022]
Abstract
Considerable evidence links the microglial transmembrane receptor TREM2 to the progression of Alzheimer's disease through its involvement in Aβ phagocytosis by microglia. While previous studies have mainly focused on the phagocytic regulation of microglia itself, the antigen presentation of microglial exosomes in the process of immunity has been less investigated. Here, we identified TREM2 expressed on the membrane of microglial exosomes and found that it controlled exosome secretion without affecting exosome size. Microglial exosomes bind to Aβ in a TREM2-dependent manner, which changes the inflammatory environment around Aβ and promotes microglia to phagocytose Aβ. These findings delineate a novel exosome-mediated mechanism of microglial cell-Aβ crosstalk that facilitates Aβ clearance under either physiological or pathological conditions in the central nervous system.
Collapse
Affiliation(s)
- Si Huang
- Department of Pharmacy, the Second Xiangya Hospital, Central South University, Changsha, 410011, PR China.,Hunan Provincial Engineering Research Centre of Translational Medicine and Innovative Drug, Changsha, 410011, PR China
| | - Xiaoli Liao
- Clinical Nursing Teaching and Research Section, the Second Xiangya Hospital, Central South University, Changsha, 410011, PR China
| | - Junyong Wu
- Department of Pharmacy, the Second Xiangya Hospital, Central South University, Changsha, 410011, PR China.,Hunan Provincial Engineering Research Centre of Translational Medicine and Innovative Drug, Changsha, 410011, PR China
| | - Xiaojie Zhang
- Department of Psychiatry, the Second Xiangya Hospital, Central South University, Changsha, 410011, PR China
| | - Yamin Li
- Clinical Nursing Teaching and Research Section, the Second Xiangya Hospital, Central South University, Changsha, 410011, PR China
| | - Daxiong Xiang
- Department of Pharmacy, the Second Xiangya Hospital, Central South University, Changsha, 410011, PR China.,Hunan Provincial Engineering Research Centre of Translational Medicine and Innovative Drug, Changsha, 410011, PR China
| | - Shilin Luo
- Department of Pharmacy, the Second Xiangya Hospital, Central South University, Changsha, 410011, PR China.,Hunan Provincial Engineering Research Centre of Translational Medicine and Innovative Drug, Changsha, 410011, PR China
| |
Collapse
|
8
|
Mahameed M, Xue S, Stefanov B, Hamri GC, Fussenegger M. Engineering a Rapid Insulin Release System Controlled By Oral Drug Administration. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2105619. [PMID: 35048556 PMCID: PMC8948567 DOI: 10.1002/advs.202105619] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Indexed: 05/14/2023]
Abstract
Rapid insulin release plays an essential role in maintaining blood-glucose homeostasis in mammalians. Patients diagnosed with type-I diabetes mellitus experience chronic and remarkably high blood-sugar levels, and require lifelong insulin injection therapy, so there is a need for more convenient and less invasive insulin delivery systems to increase patients' compliance and also to enhance their quality of life. Here, an endoplasmic-reticulum-localized split sec-tobacco etch virus protease (TEVp)-based rapamycin-actuated protein-induction device (RAPID) is engineered, which is composed of the rapamycin-inducible dimerization domains FK506 binding protein (FKBP) and FKBP-rapamycin binding protein fused with modified split sec-TEVp components. Insulin accumulation inside the endoplasmic reticulum (ER) is achieved through tagging its C-terminus with KDEL, an ER-retention signal, spaced by a TEVp cleavage site. In the presence of rapamycin, the split sec-TEVp-based RAPID components dimerize, regain their proteolytic activity, and remove the KDEL retention signal from insulin. This leads to rapid secretion of accumulated insulin from cells within few minutes. Using liver hydrodynamic transfection methodology, it is shown that RAPID quickly restores glucose homeostasis in type-1-diabetic (T1DM) mice treated with an oral dose of clinically licensed rapamycin. This rapid-release technology may become the foundation for other cell-based therapies requiring instantaneous biopharmaceutical availability.
Collapse
Affiliation(s)
- Mohamed Mahameed
- Department of Biosystems Science and EngineeringETH ZurichMattenstrasse 26BaselCH‐4058Switzerland
| | - Shuai Xue
- Department of Biosystems Science and EngineeringETH ZurichMattenstrasse 26BaselCH‐4058Switzerland
| | - Bozhidar‐Adrian Stefanov
- Department of Biosystems Science and EngineeringETH ZurichMattenstrasse 26BaselCH‐4058Switzerland
| | - Ghislaine Charpin‐El Hamri
- Département Génie BiologiqueInstitut Universitaire de TechnologieUniversité Claude Bernard Lyon 1Villeurbanne CedexF‐69622France
| | - Martin Fussenegger
- Department of Biosystems Science and EngineeringETH ZurichMattenstrasse 26BaselCH‐4058Switzerland
- University of BaselFaculty of Life ScienceBaselCH‐4058Switzerland
| |
Collapse
|
9
|
Das UN. Arachidonic Acid as Mechanotransducer of Renin Cell Baroreceptor. Nutrients 2022; 14:nu14040749. [PMID: 35215399 PMCID: PMC8874622 DOI: 10.3390/nu14040749] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Revised: 01/31/2022] [Accepted: 02/02/2022] [Indexed: 11/16/2022] Open
Abstract
For normal maintenance of blood pressure and blood volume a well-balanced renin-angiotensin-aldosterone system (RAS) is necessary. For this purpose, renin is secreted as the situation demands by the juxtaglomerular cells (also called as granular cells) that are in the walls of the afferent arterioles. Juxtaglomerular cells can sense minute changes in the blood pressure and blood volume and accordingly synthesize, store, and secrete appropriate amounts of renin. Thus, when the blood pressure and blood volume are decreased JGA cells synthesize and secrete higher amounts of renin and when the blood pressure and blood volume is increased the synthesis and secretion of renin is decreased such that homeostasis is restored. To decipher this important function, JGA cells (renin cells) need to sense and transmit the extracellular physical forces to their chromatin to control renin gene expression for appropriate renin synthesis. The changes in perfusion pressure are sensed by Integrin β1 that is transmitted to the renin cell’s nucleus via lamin A/C that produces changes in the architecture of the chromatin. This results in an alteration (either increase or decrease) in renin gene expression. Cell membrane is situated in an unique location since all stimuli need to be transmitted to the cell nucleus and messages from the DNA to the cell external environment can be conveyed only through it. This implies that cell membrane structure and integrity is essential for all cellular functions. Cell membrane is composed to proteins and lipids. The lipid components of the cell membrane regulate its (cell membrane) fluidity and the way the messages are transmitted between the cell and its environment. Of all the lipids present in the membrane, arachidonic acid (AA) forms an important constituent. In response to pressure and other stimuli, cellular and nuclear shape changes occur that render nucleus to act as an elastic mechanotransducer that produces not only changes in cell shape but also in its dynamic behavior. Cell shape changes in response to external pressure(s) result(s) in the activation of cPLA2 (cytosolic phospholipase 2)-AA pathway that stretches to recruit myosin II which produces actin-myosin cytoskeleton contractility. Released AA can undergo peroxidation and peroxidized AA binds to DNA to regulate the expression of several genes. Alterations in the perfusion pressure in the afferent arterioles produces parallel changes in the renin cell membrane leading to changes in renin release. AA and its metabolic products regulate not only the release of renin but also changes in the vanilloid type 1 (TRPV1) expression in renal sensory nerves. Thus, AA and its metabolites function as intermediate/mediator molecules in transducing changes in perfusion and mechanical pressures that involves nuclear mechanotransduction mechanism. This mechanotransducer function of AA has relevance to the synthesis and release of insulin, neurotransmitters, and other soluble mediators release by specialized and non-specialized cells. Thus, AA plays a critical role in diseases such as diabetes mellitus, hypertension, atherosclerosis, coronary heart disease, sepsis, lupus, rheumatoid arthritis, and cancer.
Collapse
Affiliation(s)
- Undurti N Das
- UND Life Sciences, 2221 NW 5th St., Battle Ground, WA 98604, USA
| |
Collapse
|
10
|
Cataldo LR, Singh T, Achanta K, Bsharat S, Prasad RB, Luan C, Renström E, Eliasson L, Artner I. MAFA and MAFB regulate exocytosis-related genes in human β-cells. Acta Physiol (Oxf) 2022; 234:e13761. [PMID: 34978761 DOI: 10.1111/apha.13761] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 12/22/2021] [Accepted: 01/01/2022] [Indexed: 12/13/2022]
Abstract
AIMS Reduced expression of exocytotic genes is associated with functional defects in insulin exocytosis contributing to impaired insulin secretion and type 2 diabetes (T2D) development. MAFA and MAFB transcription factors regulate β-cell physiology, and their gene expression is reduced in T2D β cells. We investigate if loss of MAFA and MAFB in human β cells contributes to T2D progression by regulating genes required for insulin exocytosis. METHODS Three approaches were performed: (1) RNAseq analysis with the focus on exocytosis-related genes in MafA-/- mouse islets, (2) correlational analysis between MAFA, MAFB and exocytosis-related genes in human islets and (3) MAFA and MAFB silencing in human islets and EndoC-βH1 cells followed by functional in vitro studies. RESULTS The expression of 30 exocytosis-related genes was significantly downregulated in MafA-/- mouse islets. In human islets, the expression of 29 exocytosis-related genes correlated positively with MAFA and MAFB. Eight exocytosis-related genes were downregulated in MafA-/- mouse islets and positively correlated with MAFA and MAFB in human islets. From this analysis, the expression of RAB3A, STXBP1, UNC13A, VAMP2, NAPA, NSF, STX1A and SYT7 was quantified after acute MAFA or MAFB silencing in EndoC-βH1 cells and human islets. MAFA and MAFB silencing resulted in impaired insulin secretion and reduced STX1A, SYT7 and STXBP1 (EndoC-βH1) and STX1A (human islets) mRNA expression. STX1A and STXBP1 protein expression was also impaired in islets from T2D donors which lack MAFA expression. CONCLUSION Our data indicate that STXBP1 and STX1A are important MAFA/B-regulated exocytosis genes which may contribute to insulin exocytosis defects observed in MAFA-deficient human T2D β cells.
Collapse
Affiliation(s)
- Luis Rodrigo Cataldo
- Endocrine Cell Differentiation and Function Group Stem Cell Centre Lund University Lund Sweden
- Lund University Diabetes Centre Clinical Research Center Malmo Sweden
- The Novo Nordisk Foundation Centre for Basic Metabolic Research Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | - Tania Singh
- Endocrine Cell Differentiation and Function Group Stem Cell Centre Lund University Lund Sweden
- Lund University Diabetes Centre Clinical Research Center Malmo Sweden
| | - Kavya Achanta
- Endocrine Cell Differentiation and Function Group Stem Cell Centre Lund University Lund Sweden
- Lund University Diabetes Centre Clinical Research Center Malmo Sweden
| | - Sara Bsharat
- Endocrine Cell Differentiation and Function Group Stem Cell Centre Lund University Lund Sweden
- Lund University Diabetes Centre Clinical Research Center Malmo Sweden
| | - Rashmi B. Prasad
- Lund University Diabetes Centre Clinical Research Center Malmo Sweden
- Department of Clinical Sciences in Malmö Malmo Sweden
| | - Cheng Luan
- Lund University Diabetes Centre Clinical Research Center Malmo Sweden
| | - Erik Renström
- Lund University Diabetes Centre Clinical Research Center Malmo Sweden
| | - Lena Eliasson
- Lund University Diabetes Centre Clinical Research Center Malmo Sweden
- Department of Clinical Sciences in Malmö Malmo Sweden
- Islet Cell Exocytosis Lund University Lund Sweden
| | - Isabella Artner
- Endocrine Cell Differentiation and Function Group Stem Cell Centre Lund University Lund Sweden
- Lund University Diabetes Centre Clinical Research Center Malmo Sweden
| |
Collapse
|
11
|
Gaus B, Brüning D, Groß S, Müller M, Rustenbeck I. The changing view of insulin granule mobility: From conveyor belt to signaling hub. Front Endocrinol (Lausanne) 2022; 13:983152. [PMID: 36120467 PMCID: PMC9478610 DOI: 10.3389/fendo.2022.983152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 08/11/2022] [Indexed: 11/28/2022] Open
Abstract
Before the advent of TIRF microscopy the fate of the insulin granule prior to secretion was deduced from biochemical investigations, electron microscopy and electrophysiological measurements. Since Calcium-triggered granule fusion is indisputably necessary to release insulin into the extracellular space, much effort was directed to the measure this event at the single granule level. This has also been the major application of the TIRF microscopy of the pancreatic beta cell when it became available about 20 years ago. To better understand the metabolic modulation of secretion, we were interested to characterize the entirety of the insulin granules which are localized in the vicinity of the plasma membrane to identify the characteristics which predispose to fusion. In this review we concentrate on how the description of granule mobility in the submembrane space has evolved as a result of progress in methodology. The granules are in a state of constant turnover with widely different periods of residence in this space. While granule fusion is associated +with prolonged residence and decreased lateral mobility, these characteristics may not only result from binding to the plasma membrane but also from binding to the cortical actin web, which is present in the immediate submembrane space. While granule age as such affects granule mobility and fusion probability, the preceding functional states of the beta cell leave their mark on these parameters, too. In summary, the submembrane granules form a highly dynamic heterogeneous population and contribute to the metabolic memory of the beta cells.
Collapse
Affiliation(s)
- Bastian Gaus
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Dennis Brüning
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Sofie Groß
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Michael Müller
- Institute of Dynamics and Vibrations, Technische Universität Braunschweig, Braunschweig, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
- *Correspondence: Ingo Rustenbeck,
| |
Collapse
|
12
|
Wang L, Wang J, Wang Z, Zhou J, Zhang Y. Higher Urine Exosomal miR-193a Is Associated With a Higher Probability of Primary Focal Segmental Glomerulosclerosis and an Increased Risk of Poor Prognosis Among Children With Nephrotic Syndrome. Front Cell Dev Biol 2021; 9:727370. [PMID: 34708038 PMCID: PMC8542839 DOI: 10.3389/fcell.2021.727370] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 09/22/2021] [Indexed: 12/29/2022] Open
Abstract
Background: In children, focal segmental glomerulosclerosis (FSGS) is one of the most common primary glomerular diseases leading to end-stage renal disease. Exosomes facilitate communication between cells by transporting proteins and microRNAs. We aimed to investigate the utility of urine exosomal miR-193a for diagnosis and prognosis estimation among patients with primary FSGS, and preliminarily explore the regulation mechanism of exosome secretion from podocytes. Methods: Specimens of urine were obtained from patients with primary FSGS, minimal change nephropathy (MCN) and IgA nephropathy (IgAN), followed by exosome isolation. We quantified urine exosomal miR-193a based on quantitative reverse transcription-polymerase chain reaction, and evaluated its applicability using area-under-receiver-operating-characteristics curves (AUROCs). The semiquantitative glomerulosclerosis index (GSI) was used to evaluate the degree of glomerulosclerosis according to the method of Raij et al. We further used FAM-labeled miR-193a-5p to examine exosome shuttling using confocal microscopy for visualization, and explored the regulation mechanism of exosomes release from podocytes using Fluo-3AM dye. Results: Urine exosomal miR-193a levels were significantly higher in patients with primary FSGS than those with MCN and IgAN. The AUROCs for discriminating between primary FSGS and MCN or IgAN were 0.85 and 0.821, respectively. Urine exosomal miR-193a levels positively correlated with GSI in patients with primary FSGS. We further found that kidney tissues from these patients had increased CD63 expression involving podocytes in non-sclerotic tufts. Exosomes from cultured podocytes could transport miR-193a-5p to recipient cells, potentially through a calcium-dependent release mechanism. Conclusion: Urine exosomal miR-193a might be harnessed as a non-invasive marker for diagnosis and outcome assessment among patients with primary FSGS. Exosomes were potential vehicles for miRNAs shuttling between podocytes, and released from podocytes in a calcium-dependent manner.
Collapse
Affiliation(s)
- Lixia Wang
- Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Department of Neonatology, Maternal and Child Health Hospital of Hubei Province, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jie Wang
- Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhimin Wang
- Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jianhua Zhou
- Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yu Zhang
- Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| |
Collapse
|
13
|
Chen S, Chen K, Xu J, Li F, Ding J, Ma Z, Li G, Li H. Insights Into mRNA and Long Non-coding RNA Profiling RNA Sequencing in Uterus of Chickens With Pink and Blue Eggshell Colors. Front Vet Sci 2021; 8:736387. [PMID: 34692811 PMCID: PMC8529033 DOI: 10.3389/fvets.2021.736387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 08/30/2021] [Indexed: 11/17/2022] Open
Abstract
The blue egg is both of biological interest and economic importance for consumers, egg retailers, and scientists. To date, the genetic mechanisms underlying pigment have mainly focused on protein-coding genes. However, the underpinning mechanism of non-coding RNAs on the pigment deposition among different eggshell colors remains unknown. In this study, RNA sequencing was employed to profile the uterine gland transcriptome (lncRNA and mRNA) of 15 Changshun blue eggshell layers, to better understand the genetic mechanisms of deposition of blue eggshell color. Results showed that differentially expressed mRNAs, GO terms, and KEGG pathways among pink-eggshell and blue-eggshell chickens were mainly targeting immune- and transporter-related terms with the SLC family, IgJ, CD family, and MTMR genes. Furthermore, the progesterone-mediated oocyte maturation and cortisol synthesis and secretion pathway with targeted gene PGR and Pbx1 were significantly enriched between blue- and pink-eggshell chickens. Integrating analysis of lncRNA and mRNA profiles predicted 4 and 25 lncRNA–gene pairs by antisense and cis analysis. They were relative to immune, nerve, and lipids and amino acid metabolisms, porphyrin, and chlorophyll metabolism with targeted gene FECH and oxidative phosphorylation and cardiac muscle contraction pathways with targeted gene COX6A1. Within blue-eggshell chickens, the GO terms hindbrain tangential cell migration and phosphatidylinositol monophosphate phosphatase activity with targeted gene Plxna2 and MTRM1 were identified. Integrating analysis of lncRNA and mRNA profiles predicted 8 and 22 lncRNA–gene pairs. Most pathways were mainly enriched on lipid-related metabolisms as found in mRNA sequencing. The lncRNAs did exert similar functions in color formation by modulating pigment disposition and immune- and lipid-related metabolisms. Our results provide a catalog of chicken uterine lncRNAs and genes worthy of further studies to understand their roles in the selection for blue eggshell color layers.
Collapse
Affiliation(s)
- Siyu Chen
- Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, Key Laboratory of Animal Molecular Design and Precise Breeding of Guangdong Higher Education Institutes, School of Life Science and Engineering, Foshan University, Foshan, China
| | - Kecheng Chen
- Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, Key Laboratory of Animal Molecular Design and Precise Breeding of Guangdong Higher Education Institutes, School of Life Science and Engineering, Foshan University, Foshan, China
| | - Jiaming Xu
- Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, Key Laboratory of Animal Molecular Design and Precise Breeding of Guangdong Higher Education Institutes, School of Life Science and Engineering, Foshan University, Foshan, China
| | - Fangwei Li
- Guizhou Changshun Tiannong Green Shell Laying Hen Industrial Co. Ltd, Chang Shun City, China
| | - Jinlong Ding
- Guizhou Changshun Tiannong Green Shell Laying Hen Industrial Co. Ltd, Chang Shun City, China
| | - Zheng Ma
- Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, Key Laboratory of Animal Molecular Design and Precise Breeding of Guangdong Higher Education Institutes, School of Life Science and Engineering, Foshan University, Foshan, China
| | - Gen Li
- Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, Key Laboratory of Animal Molecular Design and Precise Breeding of Guangdong Higher Education Institutes, School of Life Science and Engineering, Foshan University, Foshan, China
| | - Hua Li
- Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, Key Laboratory of Animal Molecular Design and Precise Breeding of Guangdong Higher Education Institutes, School of Life Science and Engineering, Foshan University, Foshan, China
| |
Collapse
|
14
|
Oleaga C, Shapiro MD, Hay J, Mueller PA, Miles J, Huang C, Friz E, Tavori H, Toth PP, Wójcik C, Warden BA, Purnell JQ, Duell PB, Pamir N, Fazio S. Hepatic Sensing Loop Regulates PCSK9 Secretion in Response to Inhibitory Antibodies. J Am Coll Cardiol 2021; 78:1437-1449. [PMID: 34593126 PMCID: PMC8486917 DOI: 10.1016/j.jacc.2021.07.056] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 07/08/2021] [Accepted: 07/26/2021] [Indexed: 01/06/2023]
Abstract
BACKGROUND Monoclonal antibodies against proprotein convertase subtilisin/kexin type 9 (PCSK9i) lower LDL-C by up to 60% and increase plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) levels by 10-fold. OBJECTIVES The authors studied the reasons behind the robust increase in plasma PCSK9 levels by testing the hypothesis that mechanisms beyond clearance via the low-density lipoprotein receptor (LDLR) contribute to the regulation of cholesterol homeostasis. METHODS In clinical cohorts, animal models, and cell-based studies, we measured kinetic changes in PCSK9 production and clearance in response to PCSK9i. RESULTS In a patient cohort receiving PCSK9i therapy, plasma PCSK9 levels rose 11-fold during the first 3 months and then plateaued for 15 months. In a cohort of healthy volunteers, a single injection of PCSK9i increased plasma PCSK9 levels within 12 hours; the rise continued for 9 days until it plateaued at 10-fold above baseline. We recapitulated the rapid rise in PCSK9 levels in a mouse model, but only in the presence of LDLR. In vivo turnover and in vitro pulse-chase studies identified 2 mechanisms contributing to the rapid increase in plasma PCSK9 levels in response to PCSK9i: 1) the expected delayed clearance of the antibody-bound PCSK9; and 2) the unexpected post-translational increase in PCSK9 secretion. CONCLUSIONS PCSK9 re-entry to the liver via LDLR triggers a sensing loop regulating PCSK9 secretion. PCSK9i therapy enhances the secretion of PCSK9, an effect that contributes to the increased plasma PCSK9 levels in treated subjects.
Collapse
Affiliation(s)
- Carlota Oleaga
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Michael D Shapiro
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Joshua Hay
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Paul A Mueller
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Joshua Miles
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Cecilia Huang
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Emily Friz
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Hagai Tavori
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Peter P Toth
- Ciccarone Center for the Prevention of Cardiovascular Disease, Johns Hopkins University, and School of Medicine, Baltimore, Maryland, USA; CGH Medical Center, Sterling, Illinois, USA
| | - Cezary Wójcik
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Bruce A Warden
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Jonathan Q Purnell
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - P Barton Duell
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Nathalie Pamir
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA.
| | - Sergio Fazio
- Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Portland, Oregon, USA
| |
Collapse
|
15
|
Gaus B, Brüning D, Hatlapatka K, Rustenbeck I. Changes in granule mobility and age contribute to changes in insulin secretion after desensitization or rest. BMJ Open Diabetes Res Care 2021; 9:9/1/e002394. [PMID: 34620619 PMCID: PMC8499263 DOI: 10.1136/bmjdrc-2021-002394] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 09/14/2021] [Indexed: 12/17/2022] Open
Abstract
INTRODUCTION Functional impairment of the stimulus secretion coupling in pancreatic beta cells is an essential component of type 2 diabetes. It is known that prolonged stimulation desensitizes the secretion of insulin and thus contributes to beta cell dysfunction. Beta cell rest, in contrast, was shown to enhance the secretory response. Here, the underlying mechanisms were investigated. RESEARCH DESIGN AND METHODS To characterize the consequences of desensitization or rest for the number and mobility of submembrane granules, insulin-secreting MIN6 cells were desensitized by 18-hour culture with 500 µM tolbutamide or rested by 18-hour culture with 1 µM clonidine. The granules were labeled by hIns-EGFP or hIns-DsRed E5, imaged by TIRF microscopy of the cell footprint area and analyzed with an observer-independent program. Additionally, the insulin content and secretion were measured. RESULTS Concurrent with the insulin content, submembrane granules were only slightly reduced after desensitization but markedly increased after rest. Both types of pretreatment diminished arrivals and departures of granules in the submembrane space and increased the proportion of immobile long-term resident granules, but desensitization lowered and rest increased the number of exocytoses, in parallel with the effect on insulin secretion. Labeling with hIns-DsRed E5 ('timer') showed that desensitization did not affect the proportion of aged granules, whereas rest increased it. Aged granules showed a high mobility and made up only a minority of long-term residents. Long-term resident granules were more numerous after rest and had a lower lateral mobility, suggesting a firmer attachment to the membrane. CONCLUSION The number, mobility and age of submembrane granules reflect the preceding functional states of insulin-secreting cells. Representing the pool of releasable granules, their quantity and quality may thus form part of the beta cell memory on renewed stimulation.
Collapse
Affiliation(s)
- Bastian Gaus
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Dennis Brüning
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Kathrin Hatlapatka
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
- DHD-Consulting GmbH, Hildesheim, Germany
| | - Ingo Rustenbeck
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| |
Collapse
|
16
|
Asadi F, Dhanvantari S. Pathways of Glucagon Secretion and Trafficking in the Pancreatic Alpha Cell: Novel Pathways, Proteins, and Targets for Hyperglucagonemia. Front Endocrinol (Lausanne) 2021; 12:726368. [PMID: 34659118 PMCID: PMC8511682 DOI: 10.3389/fendo.2021.726368] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 09/13/2021] [Indexed: 12/15/2022] Open
Abstract
Patients with diabetes mellitus exhibit hyperglucagonemia, or excess glucagon secretion, which may be the underlying cause of the hyperglycemia of diabetes. Defective alpha cell secretory responses to glucose and paracrine effectors in both Type 1 and Type 2 diabetes may drive the development of hyperglucagonemia. Therefore, uncovering the mechanisms that regulate glucagon secretion from the pancreatic alpha cell is critical for developing improved treatments for diabetes. In this review, we focus on aspects of alpha cell biology for possible mechanisms for alpha cell dysfunction in diabetes: proglucagon processing, intrinsic and paracrine control of glucagon secretion, secretory granule dynamics, and alterations in intracellular trafficking. We explore possible clues gleaned from these studies in how inhibition of glucagon secretion can be targeted as a treatment for diabetes mellitus.
Collapse
Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Western University, London, ON, Canada
- Program in Metabolism and Diabetes, Lawson Health Research Institute, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Western University, London, ON, Canada
- Program in Metabolism and Diabetes, Lawson Health Research Institute, London, ON, Canada
- Imaging Research Program, Lawson Health Research Institute, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
| |
Collapse
|
17
|
Lizarraga-Valderrama LR, Sheridan GK. Extracellular vesicles and intercellular communication in the central nervous system. FEBS Lett 2021; 595:1391-1410. [PMID: 33728650 DOI: 10.1002/1873-3468.14074] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 03/07/2021] [Accepted: 03/08/2021] [Indexed: 12/30/2022]
Abstract
Neurons and glial cells of the central nervous system (CNS) release extracellular vesicles (EVs) to the interstitial fluid of the brain and spinal cord parenchyma. EVs contain proteins, nucleic acids and lipids that can be taken up by, and modulate the behaviour of, neighbouring recipient cells. The functions of EVs have been extensively studied in the context of neurodegenerative diseases. However, mechanisms involved in EV-mediated neuron-glial communication under physiological conditions or healthy ageing remain unclear. A better understanding of the myriad roles of EVs in CNS homeostasis is essential for the development of novel therapeutics to alleviate and reverse neurological disturbances of ageing. Proteomic studies are beginning to reveal cell type-specific EV cargo signatures that may one day allow us to target specific neuronal or glial cell populations in the treatment of debilitating neurological disorders. This review aims to synthesise the current literature regarding EV-mediated cell-cell communication in the brain, predominantly under physiological conditions.
Collapse
Affiliation(s)
| | - Graham K Sheridan
- School of Life Sciences, Queens Medical Centre, University of Nottingham, UK
| |
Collapse
|
18
|
Schulze T, Mattern K, Erfle P, Brüning D, Scherneck S, Dietzel A, Rustenbeck I. A Parallel Perifusion Slide From Glass for the Functional and Morphological Analysis of Pancreatic Islets. Front Bioeng Biotechnol 2021; 9:615639. [PMID: 33763408 PMCID: PMC7982818 DOI: 10.3389/fbioe.2021.615639] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 02/12/2021] [Indexed: 12/15/2022] Open
Abstract
An islet-on-chip system in the form of a completely transparent microscope slide optically accessible from both sides was developed. It is made from laser-structured borosilicate glass and enables the parallel perifusion of five microchannels, each containing one islet precisely immobilized in a pyramidal well. The islets can be in inserted via separate loading windows above each pyramidal well. This design enables a gentle, fast and targeted insertion of the islets and a reliable retention in the well while at the same time permitting a sufficiently fast exchange of the media. In addition to the measurement of the hormone content in the fractionated efflux, parallel live cell imaging of the islet is possible. By programmable movement of the microscopic stage imaging of five wells can be performed. The current chip design ensures sufficient time resolution to characterize typical parameters of stimulus-secretion coupling. This was demonstrated by measuring the reaction of the islets to stimulation by glucose and potassium depolarization. After the perifusion experiment islets can be removed for further analysis. The live-dead assay of the removed islets confirmed that the process of insertion and removal was not detrimental to islet structure and viability. In conclusion, the present islet-on-chip design permits the practical implementation of parallel perifusion experiments on a single and easy to load glass slide. For each immobilized islet the correlation between secretion, signal transduction and morphology is possible. The slide concept allows the scale-up to even higher degrees of parallelization.
Collapse
Affiliation(s)
- Torben Schulze
- Institute of Pharmacology and Toxicology, Technische Universität Braunschweig, Braunschweig, Germany.,Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, Braunschweig, Germany
| | - Kai Mattern
- Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, Braunschweig, Germany.,Institute of Microtechnology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Per Erfle
- Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, Braunschweig, Germany.,Institute of Microtechnology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Dennis Brüning
- Institute of Pharmacology and Toxicology, Technische Universität Braunschweig, Braunschweig, Germany.,Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, Braunschweig, Germany
| | - Stephan Scherneck
- Institute of Pharmacology and Toxicology, Technische Universität Braunschweig, Braunschweig, Germany.,Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, Braunschweig, Germany
| | - Andreas Dietzel
- Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, Braunschweig, Germany.,Institute of Microtechnology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology and Toxicology, Technische Universität Braunschweig, Braunschweig, Germany.,Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, Braunschweig, Germany
| |
Collapse
|
19
|
Wilhelmi I, Grunwald S, Gimber N, Popp O, Dittmar G, Arumughan A, Wanker EE, Laeger T, Schmoranzer J, Daumke O, Schürmann A. The ARFRP1-dependent Golgi scaffolding protein GOPC is required for insulin secretion from pancreatic β-cells. Mol Metab 2020; 45:101151. [PMID: 33359402 PMCID: PMC7811047 DOI: 10.1016/j.molmet.2020.101151] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/15/2020] [Accepted: 12/15/2020] [Indexed: 12/13/2022] Open
Abstract
Objective Hormone secretion from metabolically active tissues, such as pancreatic islets, is governed by specific and highly regulated signaling pathways. Defects in insulin secretion are among the major causes of diabetes. The molecular mechanisms underlying regulated insulin secretion are, however, not yet completely understood. In this work, we studied the role of the GTPase ARFRP1 on insulin secretion from pancreatic β-cells. Methods A β-cell-specific Arfrp1 knockout mouse was phenotypically characterized. Pulldown experiments and mass spectrometry analysis were employed to screen for new ARFRP1-interacting proteins. Co-immunoprecipitation assays as well as super-resolution microscopy were applied for validation. Results The GTPase ARFRP1 interacts with the Golgi-associated PDZ and coiled-coil motif-containing protein (GOPC). Both proteins are co-localized at the trans-Golgi network and regulate the first and second phase of insulin secretion by controlling the plasma membrane localization of the SNARE protein SNAP25. Downregulation of both GOPC and ARFRP1 in Min6 cells interferes with the plasma membrane localization of SNAP25 and enhances its degradation, thereby impairing glucose-stimulated insulin release from β-cells. In turn, overexpression of SNAP25 as well as GOPC restores insulin secretion in islets from β-cell-specific Arfrp1 knockout mice. Conclusion Our results identify a hitherto unrecognized pathway required for insulin secretion at the level of trans-Golgi sorting. β-cell specific deletion of the trans-Golgi residing small GTPase ARFRP1 leads to elevated blood glucose levels in mice. GOPC is a newly identified ARFRP1 dependent scaffolding protein. ARFRP1 and GOPC are required for glucose-stimulated insulin secretion from pancreatic β-cells.
Collapse
Affiliation(s)
- Ilka Wilhelmi
- German Institute of Human Nutrition (DIfE) Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD) Munich Neuherberg, Germany
| | - Stephan Grunwald
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany; Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany
| | - Niclas Gimber
- Advanced Medical Bioimaging Core Facility - AMBIO, Charité-Universitätsmedizin Berlin, Germany
| | - Oliver Popp
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany
| | - Gunnar Dittmar
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany
| | - Anup Arumughan
- Neuroproteomics, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC) Berlin, Germany
| | - Erich E Wanker
- Neuroproteomics, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC) Berlin, Germany
| | - Thomas Laeger
- German Institute of Human Nutrition (DIfE) Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD) Munich Neuherberg, Germany
| | - Jan Schmoranzer
- Advanced Medical Bioimaging Core Facility - AMBIO, Charité-Universitätsmedizin Berlin, Germany
| | - Oliver Daumke
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany; Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany
| | - Annette Schürmann
- German Institute of Human Nutrition (DIfE) Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD) Munich Neuherberg, Germany; University of Potsdam, Institute of Nutritional Sciences, Nuthetal, Germany; Faculty of Health Sciences, Joint Faculty of the Brandenburg University of Technology Cottbus - Senftenberg, the Brandenburg Medical School Theodor Fontane and the University of Potsdam, Germany.
| |
Collapse
|
20
|
Toth AE, Holst MR, Nielsen MS. Vesicular Transport Machinery in Brain Endothelial Cells: What We Know and What We Do not. Curr Pharm Des 2020; 26:1405-1416. [PMID: 32048959 DOI: 10.2174/1381612826666200212113421] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 12/03/2019] [Indexed: 12/20/2022]
Abstract
The vesicular transport machinery regulates numerous essential functions in cells such as cell polarity, signaling pathways, and the transport of receptors and their cargoes. From a pharmaceutical perspective, vesicular transport offers avenues to facilitate the uptake of therapeutic agents into cells and across cellular barriers. In order to improve receptor-mediated transcytosis of biologics across the blood-brain barrier and into the diseased brain, a detailed understanding of intracellular transport mechanisms is essential. The vesicular transport machinery is a highly complex network and involves an array of protein complexes, cytosolic adaptor proteins, and the subcellular structures of the endo-lysosomal system. The endo-lysosomal system includes several types of vesicular entities such as early, late, and recycling endosomes, exosomes, ectosomes, retromer-coated vesicles, lysosomes, trans-endothelial channels, and tubules. While extensive research has been done on the trafficking system in many cell types, little is known about vesicular trafficking in brain endothelial cells. Consequently, assumptions on the transport system in endothelial cells are based on findings in polarised epithelial cells, although recent studies have highlighted differences in the endothelial system. This review highlights aspects of the vesicular trafficking machinery in brain endothelial cells, including recent findings, limitations, and opportunities for further studies.
Collapse
Affiliation(s)
- Andrea E Toth
- Department of Biomedicine, Faculty of Health, Aarhus University, Høegh-Guldberg Gade 10, 8000 Aarhus C, Denmark
| | - Mikkel R Holst
- Department of Biomedicine, Faculty of Health, Aarhus University, Høegh-Guldberg Gade 10, 8000 Aarhus C, Denmark
| | - Morten S Nielsen
- Department of Biomedicine, Faculty of Health, Aarhus University, Høegh-Guldberg Gade 10, 8000 Aarhus C, Denmark
| |
Collapse
|
21
|
Gheibi S, Ghasemi A. Insulin secretion: The nitric oxide controversy. EXCLI JOURNAL 2020; 19:1227-1245. [PMID: 33088259 PMCID: PMC7573190 DOI: 10.17179/excli2020-2711] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 08/31/2020] [Indexed: 12/14/2022]
Abstract
Nitric oxide (NO) is a gas that serves as a ubiquitous signaling molecule participating in physiological activities of various organ systems. Nitric oxide is produced in the endocrine pancreas and contributes to synthesis and secretion of insulin. The potential role of NO in insulin secretion is disputable - both stimulatory and inhibitory effects have been reported. Available data indicate that effects of NO critically depend on its concentration. Different isoforms of NO synthase (NOS) control this and have the potential to decrease or increase insulin secretion. In this review, the role of NO in insulin secretion as well as the possible reasons for discrepant findings are discussed. A better understanding of the role of NO system in the regulation of insulin secretion may facilitate the development of new therapeutic strategies in the management of diabetes.
Collapse
Affiliation(s)
- Sevda Gheibi
- Department of Clinical Sciences in Malmö, Unit of Molecular Metabolism, Lund University Diabetes Centre, Clinical Research Center, Malmö University Hospital, Lund University, Malmö, Sweden
| | - Asghar Ghasemi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| |
Collapse
|
22
|
Lee CE, Singleton KS, Wallin M, Faundez V. Rare Genetic Diseases: Nature's Experiments on Human Development. iScience 2020; 23:101123. [PMID: 32422592 PMCID: PMC7229282 DOI: 10.1016/j.isci.2020.101123] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/25/2020] [Accepted: 04/29/2020] [Indexed: 01/25/2023] Open
Abstract
Rare genetic diseases are the result of a continuous forward genetic screen that nature is conducting on humans. Here, we present epistemological and systems biology arguments highlighting the importance of studying these rare genetic diseases. We contend that the expanding catalog of mutations in ∼4,000 genes, which cause ∼6,500 diseases and their annotated phenotypes, offer a wide landscape for discovering fundamental mechanisms required for human development and involved in common diseases. Rare afflictions disproportionately affect the nervous system in children, but paradoxically, the majority of these disease-causing genes are evolutionarily ancient and ubiquitously expressed in human tissues. We propose that the biased prevalence of childhood rare diseases affecting nervous tissue results from the topological complexity of the protein interaction networks formed by ubiquitous and ancient proteins encoded by childhood disease genes. Finally, we illustrate these principles discussing Menkes disease, an example of the discovery power afforded by rare diseases.
Collapse
Affiliation(s)
- Chelsea E Lee
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA
| | - Kaela S Singleton
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA
| | - Melissa Wallin
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA
| | - Victor Faundez
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA.
| |
Collapse
|
23
|
Herrmann M, Engelke K, Ebert R, Müller-Deubert S, Rudert M, Ziouti F, Jundt F, Felsenberg D, Jakob F. Interactions between Muscle and Bone-Where Physics Meets Biology. Biomolecules 2020; 10:biom10030432. [PMID: 32164381 PMCID: PMC7175139 DOI: 10.3390/biom10030432] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 02/27/2020] [Accepted: 03/05/2020] [Indexed: 02/06/2023] Open
Abstract
Muscle and bone interact via physical forces and secreted osteokines and myokines. Physical forces are generated through gravity, locomotion, exercise, and external devices. Cells sense mechanical strain via adhesion molecules and translate it into biochemical responses, modulating the basic mechanisms of cellular biology such as lineage commitment, tissue formation, and maturation. This may result in the initiation of bone formation, muscle hypertrophy, and the enhanced production of extracellular matrix constituents, adhesion molecules, and cytoskeletal elements. Bone and muscle mass, resistance to strain, and the stiffness of matrix, cells, and tissues are enhanced, influencing fracture resistance and muscle power. This propagates a dynamic and continuous reciprocity of physicochemical interaction. Secreted growth and differentiation factors are important effectors of mutual interaction. The acute effects of exercise induce the secretion of exosomes with cargo molecules that are capable of mediating the endocrine effects between muscle, bone, and the organism. Long-term changes induce adaptations of the respective tissue secretome that maintain adequate homeostatic conditions. Lessons from unloading, microgravity, and disuse teach us that gratuitous tissue is removed or reorganized while immobility and inflammation trigger muscle and bone marrow fatty infiltration and propagate degenerative diseases such as sarcopenia and osteoporosis. Ongoing research will certainly find new therapeutic targets for prevention and treatment.
Collapse
Affiliation(s)
- Marietta Herrmann
- Orthopedic Department, Bernhard-Heine-Center for Locomotion Research, IZKF Research Group Tissue regeneration in musculoskeletal diseases, University Hospital Würzburg, University of Wuerzburg, 97070 Würzburg, Germany;
| | - Klaus Engelke
- Department of Medicine 3, FAU University Erlangen-Nürnberg and Universitätsklinikum Erlangen, 91054 Erlangen, Germany;
| | - Regina Ebert
- Orthopedic Department, Bernhard-Heine-Center for Locomotion Research, University of Würzburg, IGZ, 97076 Würzburg, Germany; (R.E.)
| | - Sigrid Müller-Deubert
- Orthopedic Department, Bernhard-Heine-Center for Locomotion Research, University of Würzburg, IGZ, 97076 Würzburg, Germany; (R.E.)
| | - Maximilian Rudert
- Orthopedic Department, Bernhard-Heine-Center for Locomotion Research, University of Würzburg, 97074 Würzburg, Germany;
| | - Fani Ziouti
- Department of Internal Medicine II, University Hospital Würzburg, 97080 Würzburg, Germany; (F.Z.); (F.J.)
| | - Franziska Jundt
- Department of Internal Medicine II, University Hospital Würzburg, 97080 Würzburg, Germany; (F.Z.); (F.J.)
| | - Dieter Felsenberg
- Privatpraxis für Muskel- und Knochenkrankheiten, 12163 Berlin Germany;
| | - Franz Jakob
- Orthopedic Department, Bernhard-Heine-Center for Locomotion Research, University of Würzburg, IGZ, 97076 Würzburg, Germany; (R.E.)
- Orthopedic Department, Bernhard-Heine-Center for Locomotion Research, University of Würzburg, 97074 Würzburg, Germany;
- Correspondence:
| |
Collapse
|
24
|
Ye Y, Barghouth M, Luan C, Kazim A, Zhou Y, Eliasson L, Zhang E, Hansson O, Thevenin T, Renström E. The TCF7L2-dependent high-voltage activated calcium channel subunit α2δ-1 controls calcium signaling in rodent pancreatic beta-cells. Mol Cell Endocrinol 2020; 502:110673. [PMID: 31805307 DOI: 10.1016/j.mce.2019.110673] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 11/19/2019] [Accepted: 11/30/2019] [Indexed: 12/16/2022]
Abstract
The transcription factor TCF7L2 remains the most important diabetes gene identified to date and genetic risk carriers exhibit lower insulin secretion. We show that Tcf7l2 regulates the auxiliary subunit of voltage-gated Ca2+ channels, Cacna2d1 gene/α2δ-1 protein levels. Furthermore, suppression of α2δ-1 decreased voltage-gated Ca2+ currents and high glucose/depolarization-evoked Ca2+ signaling which mimicked the effect of silencing of Tcf7l2. This appears to be the result of impaired voltage-gated Ca2+ channel trafficking to the plasma membrane, as Cav1.2 channels accumulated in the recycling endosomes after α2δ-1 suppression, in clonal as well as primary rodent beta-cells. This impaired the capacity for glucose-induced insulin secretion in Cacna2d1-silenced cells. Overexpression of α2δ-1 increased high-glucose/K+-stimulated insulin secretion. Furthermore, overexpression of α2δ-1 in Tcf7l2-silenced cells rescued the Tcf7l2-dependent impairment of Ca2+ signaling, but not the reduced insulin secretion. Taken together, these data clarify the connection between Tcf7l2, α2δ-1 in Ca2+-dependent insulin secretion.
Collapse
Affiliation(s)
- Yingying Ye
- Lund University, Department of Clinical Sciences, Islet Pathophysiology Group, Sweden
| | - Mohammad Barghouth
- Lund University, Department of Clinical Sciences, Islet Pathophysiology Group, Sweden
| | - Cheng Luan
- Lund University, Department of Clinical Sciences, Islet Pathophysiology Group, Sweden
| | - Abdulla Kazim
- Lund University, Department of Clinical Sciences, Islet Pathophysiology Group, Sweden
| | - Yuedan Zhou
- Lund University, Department of Clinical Sciences, Diabetes and Endocrinology Group, Sweden
| | - Lena Eliasson
- Lund University, Department of Clinical Sciences, Islet Pathophysiology Group, Sweden
| | - Enming Zhang
- Lund University, Department of Clinical Sciences, Islet Pathophysiology Group, Sweden
| | - Ola Hansson
- Lund University, Department of Clinical Sciences, Diabetes and Endocrinology Group, Sweden
| | - Thomas Thevenin
- Lund University, Department of Clinical Sciences, Islet Pathophysiology Group, Sweden
| | - Erik Renström
- Lund University, Department of Clinical Sciences, Islet Pathophysiology Group, Sweden.
| |
Collapse
|
25
|
Gadkar S, Nair S, Patil S, Kalamani S, Bandivdekar A, Patel V, Chaudhari U, Sachdeva G. Membrane-initiated estrogen signaling in prostate cancer: A route to epithelial-to-mesenchymal transition. Mol Carcinog 2019; 58:2077-2090. [PMID: 31411358 DOI: 10.1002/mc.23099] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 07/22/2019] [Accepted: 07/31/2019] [Indexed: 02/06/2023]
Abstract
The plasma membrane (PM) is considered as a major druggable site. More than 50% of the existing drugs target PM proteins. In the wake of emerging data indicating a key role of estrogens in prostate cancer (PCa) pathogenesis, the study was undertaken to explore whether the estrogen binding sites exist on the PM and if such sites are functionally relevant in PCa. Estradiol (E2) binding to the PM was detected in androgen-dependent (LNCaP), androgen-independent (PC3, DU145) PCa cell lines, nontumorigenic (RWPE1) prostate epithelial cell line, and rat prostate cells. Conventional estrogen receptors (nuclear estrogen receptors), known for their nuclear localization, were detected in the PM enriched extracts. This was indirectly confirmed by reduced localization of ERs on the PM of cells, silenced for the expression of their cognate genes. Further, unlike cell-permeable E2, stimulation with cell-impermeable estradiol (E2-BSA) did not induce proliferation in LNCaP cells. However, stimulation with E2-BSA led to alterations in the phosphorylation status of several kinases including GSK3 and AKT, along with the hyperphosphorylation of cytoskeletal proteins such as β-actin and cytokeratin 8 in LNCaP. This was accompanied by epithelial-to-mesenchymal (EMT) features such as increased migration and invasion; higher vimentin expression, and a concomitant decrease in the E-cadherin expression. These effects were not observed in RWPE1 cells. Interestingly, cell-permeable E2 failed to induce EMT in PCa cells. This in vitro study is the first to suggest that the PM-initiated estrogen signaling contributes to higher invasiveness in PCa cells. Plasma membrane ERs may act as novel targets for PCa therapeutics.
Collapse
Affiliation(s)
- Sushama Gadkar
- Primate Biology Laboratory, ICMR-National Institute for Research in Reproductive Health (ICMR-NIRRH), Indian Council of Medical Research (ICMR), Mumbai, India
| | - Shardool Nair
- Primate Biology Laboratory, ICMR-National Institute for Research in Reproductive Health (ICMR-NIRRH), Indian Council of Medical Research (ICMR), Mumbai, India
| | - Smita Patil
- Primate Biology Laboratory, ICMR-National Institute for Research in Reproductive Health (ICMR-NIRRH), Indian Council of Medical Research (ICMR), Mumbai, India
| | - Shilpa Kalamani
- Primate Biology Laboratory, ICMR-National Institute for Research in Reproductive Health (ICMR-NIRRH), Indian Council of Medical Research (ICMR), Mumbai, India
| | - Atmaram Bandivdekar
- Biochemistry Laboratory, ICMR-National Institute for Research in Reproductive Health (ICMR-NIRRH), Indian Council of Medical Research (ICMR), Mumbai, India
| | - Vainav Patel
- Biochemistry Laboratory, ICMR-National Institute for Research in Reproductive Health (ICMR-NIRRH), Indian Council of Medical Research (ICMR), Mumbai, India
| | - Uddhav Chaudhari
- Primate Biology Laboratory, ICMR-National Institute for Research in Reproductive Health (ICMR-NIRRH), Indian Council of Medical Research (ICMR), Mumbai, India
| | - Geetanjali Sachdeva
- Primate Biology Laboratory, ICMR-National Institute for Research in Reproductive Health (ICMR-NIRRH), Indian Council of Medical Research (ICMR), Mumbai, India
| |
Collapse
|
26
|
Abstract
In this chapter, we introduce a nanodisc-based experimental platform to study Ca2+-triggered membrane interaction of synaptotagmin-1. We describe and discuss in detail how to assemble this soluble mimetic of the docked vesicle-plasma membrane junction, with fluorescently labeled synaptotagmin-1 bound to trans SNAREpins assembled between nanodiscs and present the stopped-flow rapid mixing method used to monitor the conformational dynamics of Ca2+-activation process on a millisecond timescale.
Collapse
|
27
|
Suzuki A, Iwata J. Molecular Regulatory Mechanism of Exocytosis in the Salivary Glands. Int J Mol Sci 2018; 19:E3208. [PMID: 30336591 PMCID: PMC6214078 DOI: 10.3390/ijms19103208] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 10/10/2018] [Accepted: 10/11/2018] [Indexed: 12/12/2022] Open
Abstract
Every day, salivary glands produce about 0.5 to 1.5 L of saliva, which contains salivary proteins that are essential for oral health. The contents of saliva, 0.3% proteins (1.5 to 4.5 g) in fluid, help prevent oral infections, provide lubrication, aid digestion, and maintain oral health. Acinar cells in the lobular salivary glands secrete prepackaged secretory granules that contain salivary components such as amylase, mucins, and immunoglobulins. Despite the important physiological functions of salivary proteins, we know very little about the regulatory mechanisms of their secretion via exocytosis, which is a process essential for the secretion of functional proteins, not only in salivary glands, but also in other secretory organs, including lacrimal and mammary glands, the pancreas, and prostate. In this review, we discuss recent findings that elucidate exocytosis by exocrine glands, especially focusing on the salivary glands, in physiological and pathological conditions.
Collapse
Affiliation(s)
- Akiko Suzuki
- Department of Diagnostic & Biomedical Sciences, The University of Texas Health Science Center at Houston School of Dentistry, Houston, TX 77054, USA.
- Center for Craniofacial Research, The University of Texas Health Science Center at Houston School of Dentistry, Houston, TX 77054, USA.
| | - Junichi Iwata
- Department of Diagnostic & Biomedical Sciences, The University of Texas Health Science Center at Houston School of Dentistry, Houston, TX 77054, USA.
- Center for Craniofacial Research, The University of Texas Health Science Center at Houston School of Dentistry, Houston, TX 77054, USA.
- Program of Biochemistry and Cell Biology, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX 77030, USA.
| |
Collapse
|
28
|
Hall E, Dekker Nitert M, Volkov P, Malmgren S, Mulder H, Bacos K, Ling C. The effects of high glucose exposure on global gene expression and DNA methylation in human pancreatic islets. Mol Cell Endocrinol 2018; 472:57-67. [PMID: 29183809 DOI: 10.1016/j.mce.2017.11.019] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 10/20/2017] [Accepted: 11/23/2017] [Indexed: 01/02/2023]
Abstract
BACKGROUND Type 2 diabetes (T2D) is a complex disease characterised by chronic hyperglycaemia. The effects of elevated glucose on global gene expression in combination with DNA methylation patterns have not yet been studied in human pancreatic islets. Our aim was to study the impact of 48 h exposure to high (19 mM) versus control (5.6 mM) glucose levels on glucose-stimulated insulin secretion, gene expression and DNA methylation in human pancreatic islets. RESULTS While islets kept at 5.6 mM glucose secreted significantly more insulin in response to short term glucose-stimulation (p = 0.0067), islets exposed to high glucose for 48 h were desensitised and unresponsive to short term glucose-stimulation with respect to insulin secretion (p = 0.32). Moreover, the exposure of human islets to 19 mM glucose resulted in significantly altered expression of eight genes (FDR<5%), with five of these (GLRA1, RASD1, VAC14, SLCO5A1, CHRNA5) also exhibiting changes in DNA methylation (p < 0.05). A gene set enrichment analysis of the expression data showed significant enrichment of e.g. TGF-beta signalling pathway, Notch signalling pathway and SNARE interactions in vesicular transport; these pathways are of relevance for islet function and possibly also diabetes. We also found increased DNA methylation of CpG sites annotated to PDX1 in human islets exposed to 19 mM glucose for 48 h. Finally, we could functionally validate a role for Glra1 in insulin secretion. CONCLUSION Our data demonstrate that high glucose levels affect human pancreatic islet gene expression and several of these genes also exhibit epigenetic changes. This might contribute to the impaired insulin secretion seen in T2D.
Collapse
Affiliation(s)
- Elin Hall
- Epigenetics and Diabetes, Lund University Diabetes Centre (LUDC), Box 50332, 20213 Malmö, Sweden
| | - Marloes Dekker Nitert
- School of Medicine, Royal Brisbane Clinical School, The University of Queensland, Herston Qld 4029, Australia
| | - Petr Volkov
- Epigenetics and Diabetes, Lund University Diabetes Centre (LUDC), Box 50332, 20213 Malmö, Sweden
| | - Siri Malmgren
- Epigenetics and Diabetes, Lund University Diabetes Centre (LUDC), Box 50332, 20213 Malmö, Sweden; Molecular Metabolism, Lund University Diabetes Centre (LUDC), Box 50332, 20213 Malmö, Sweden
| | - Hindrik Mulder
- Molecular Metabolism, Lund University Diabetes Centre (LUDC), Box 50332, 20213 Malmö, Sweden
| | - Karl Bacos
- Epigenetics and Diabetes, Lund University Diabetes Centre (LUDC), Box 50332, 20213 Malmö, Sweden
| | - Charlotte Ling
- Epigenetics and Diabetes, Lund University Diabetes Centre (LUDC), Box 50332, 20213 Malmö, Sweden.
| |
Collapse
|
29
|
Seemann N, Welling A, Rustenbeck I. The inhibitor of connexin Cx36 channels, mefloquine, inhibits voltage-dependent Ca 2+ channels and insulin secretion. Mol Cell Endocrinol 2018; 472:97-106. [PMID: 29208420 DOI: 10.1016/j.mce.2017.11.024] [Citation(s) in RCA: 7] [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: 06/27/2017] [Revised: 11/27/2017] [Accepted: 11/29/2017] [Indexed: 12/13/2022]
Abstract
The antimalarial agent, mefloquine, inhibits the function of connexin Cx36 gap junctions and hemichannels and has thus become a tool to investigate their physiological relevance in pancreatic islets. In view of earlier reports on a KATP channel-block by mefloquine, the specificity of mefloquine as a pharmacological tool was investigated. Mouse pancreatic islets and single beta cells were used to measure membrane potential, whole cell currents, Ca2+ channel activity, cytosolic Ca2+ concentration ([Ca2+]i) and insulin secretion. Mefloquine was tested in the concentration range of 5-50 μM 25 μM mefloquine was as effective as 500 μM tolbutamide to depolarize the plasma membrane of beta cells, but did not induce action potentials. Rather, it abolished tolbutamide-induced action potentials and the associated increase of [Ca2+]i. In the range of 5-50 μM mefloquine inhibited voltage-dependent Ca2+ currents in primary beta cells as effectively as 1 μM nisoldipine, a specific blocker of L-type Ca2+ channels. The Ca2+ channel opening effect of Bay K8644 was completely antagonized by mefloquine. Likewise, the increase of [Ca2+]i and of insulin secretion stimulated by 40 mM KCl, but not that by 30 mM glucose was antagonized by 50 μM mefloquine. Neither at 5 μM nor at 50 μM did mefloquin stimulate insulin secretion at basal glucose. In conclusion, mefloquine blocks KATP channels and L-type Ca2+ channels in pancreatic beta cells in the range from 5 to 50 μM. Thus it inhibits depolarization-induced insulin secretion, but in the presence of a stimulatory glucose concentration additional effects of mefloquine, possibly on intracellular Ca2+ mobilization, and the metabolic amplification by glucose permit a sustained rate of secretion.
Collapse
Affiliation(s)
- Nele Seemann
- Institute of Pharmacology and Toxicology, Technische Universität Braunschweig, D-38106 Braunschweig, Germany
| | - Andrea Welling
- Institute of Pharmacology and Toxicology, Technische Universität München, D-80802 München, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology and Toxicology, Technische Universität Braunschweig, D-38106 Braunschweig, Germany.
| |
Collapse
|
30
|
Synaptotagmin oligomerization is essential for calcium control of regulated exocytosis. Proc Natl Acad Sci U S A 2018; 115:E7624-E7631. [PMID: 30038018 DOI: 10.1073/pnas.1808792115] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Regulated exocytosis, which underlies many intercellular signaling events, is a tightly controlled process often triggered by calcium ion(s) (Ca2+). Despite considerable insight into the central components involved, namely, the core fusion machinery [soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)] and the principal Ca2+ sensor [C2-domain proteins like synaptotagmin (Syt)], the molecular mechanism of Ca2+-dependent release has been unclear. Here, we report that the Ca2+-sensitive oligomers of Syt1, a conserved structural feature among several C2-domain proteins, play a critical role in orchestrating Ca2+-coupled vesicular release. This follows from pHluorin-based imaging of single-vesicle exocytosis in pheochromocytoma (PC12) cells showing that selective disruption of Syt1 oligomerization using a structure-directed mutation (F349A) dramatically increases the normally low levels of constitutive exocytosis to effectively occlude Ca2+-stimulated release. We propose a parsimonious model whereby Ca2+-sensitive oligomers of Syt (or a similar C2-domain protein) assembled at the site of docking physically block spontaneous fusion until disrupted by Ca2+ Our data further suggest Ca2+-coupled vesicular release is triggered by removal of the inhibition, rather than by direct activation of the fusion machinery.
Collapse
|
31
|
Canales J, Henriquez-Valencia C, Brauchi S. The Integration of Electrical Signals Originating in the Root of Vascular Plants. FRONTIERS IN PLANT SCIENCE 2018; 8:2173. [PMID: 29375591 PMCID: PMC5767606 DOI: 10.3389/fpls.2017.02173] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 12/12/2017] [Indexed: 05/07/2023]
Abstract
Plants have developed different signaling systems allowing for the integration of environmental cues to coordinate molecular processes associated to both early development and the physiology of the adult plant. Research on systemic signaling in plants has traditionally focused on the role of phytohormones as long-distance signaling molecules, and more recently the importance of peptides and miRNAs in building up this communication process has also been described. However, it is well-known that plants have the ability to generate different types of long-range electrical signals in response to different stimuli such as light, temperature variations, wounding, salt stress, or gravitropic stimulation. Presently, it is unclear whether short or long-distance electrical communication in plants is linked to nutrient uptake. This review deals with aspects of sensory input in plant roots and the propagation of discrete signals to the plant body. We discuss the physiological role of electrical signaling in nutrient uptake and how nutrient variations may become an electrical signal propagating along the plant.
Collapse
Affiliation(s)
- Javier Canales
- Facultad de Ciencias, Instituto de Bioquimica y Microbiologia, Universidad Austral de Chile, Valdivia, Chile
- Millennium Institute for Integrative Systems and Synthetic Biology, Santiago, Chile
| | - Carlos Henriquez-Valencia
- Facultad de Ciencias, Instituto de Bioquimica y Microbiologia, Universidad Austral de Chile, Valdivia, Chile
| | - Sebastian Brauchi
- Facultad de Medicina, Instituto de Fisiologia, Universidad Austral de Chile, Valdivia, Chile
- Millennium Nucleus of Ion Channels-Associated Diseases, Valdivia, Chile
| |
Collapse
|
32
|
Schulze T, Mattern K, Früh E, Hecht L, Rustenbeck I, Dietzel A. A 3D microfluidic perfusion system made from glass for multiparametric analysis of stimulus-secretioncoupling in pancreatic islets. Biomed Microdevices 2018; 19:47. [PMID: 28540469 DOI: 10.1007/s10544-017-0186-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Microfluidic perfusion systems (MPS) are well suited to perform multiparametric measurements with small amounts of tissue to function as an Organ on Chip device (OOC). Such microphysiolgical characterization is particularly valuable in research on the stimulus-secretion-coupling of pancreatic islets. Pancreatic islets are fully functional competent mini-organs, which serve as fuel sensors and transduce metabolic activity into rates of hormone secretion. To enable the simultaneous measurement of fluorescence and oxygen consumption we designed a microfluidic perfusion system from borosilicate glass by 3D femtosecond laser ablation. Retention of islets was accomplished by a plain well design. The characteristics of flow and shear force in the microchannels and wells were simulated and compared with the measured exchange of the perfusion media. Distribution of latex beads, MIN6 cell pseudo islets and isolated mouse islets in the MPS was characterized in dependence of flow rate and well depth. Overall, the observations suggested that a sufficient retention of the islets at low shear stress, together with sufficient exchange of test medium, was achieved at a well depth of 300 μm and perfusion rates between 40 and 240 μl/min. This enabled multiparametric measurement of oxygen consumption, NAD(P)H autofluorescence, cytosolic Ca2+ concentration, and insulin secretion by isolated mouse islets. After appropriate correction for different lag times, kinetics of these processes could be compared. Such measurements permit a more precise insight into metabolic changes underlying the regulation of insulin secretion. Thus, rapid prototyping using laser ablation enables flexible adaption of borosilicate MPS designs to different demands of biomedical research.
Collapse
Affiliation(s)
- Torben Schulze
- Institute of Pharmacology and Toxicology, Technische Universität Braunschweig, Mendelssohnstr. 1, 38106, Braunschweig, Germany.,Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, 38106, Braunschweig, Germany
| | - Kai Mattern
- Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, 38106, Braunschweig, Germany.,Institute of Microtechnology, Technische Universität Braunschweig, Alte Salzdahlumer Str. 203, 38124, Braunschweig, Germany
| | - Eike Früh
- Institute of Pharmacology and Toxicology, Technische Universität Braunschweig, Mendelssohnstr. 1, 38106, Braunschweig, Germany
| | - Lars Hecht
- Institute of Microtechnology, Technische Universität Braunschweig, Alte Salzdahlumer Str. 203, 38124, Braunschweig, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology and Toxicology, Technische Universität Braunschweig, Mendelssohnstr. 1, 38106, Braunschweig, Germany. .,Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, 38106, Braunschweig, Germany.
| | - Andreas Dietzel
- Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, 38106, Braunschweig, Germany. .,Institute of Microtechnology, Technische Universität Braunschweig, Alte Salzdahlumer Str. 203, 38124, Braunschweig, Germany.
| |
Collapse
|
33
|
Molecular regulation of insulin granule biogenesis and exocytosis. Biochem J 2017; 473:2737-56. [PMID: 27621482 DOI: 10.1042/bcj20160291] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 04/19/2016] [Indexed: 12/15/2022]
Abstract
Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by hyperglycemia, insulin resistance and hyperinsulinemia in early disease stages but a relative insulin insufficiency in later stages. Insulin, a peptide hormone, is produced in and secreted from pancreatic β-cells following elevated blood glucose levels. Upon its release, insulin induces the removal of excessive exogenous glucose from the bloodstream primarily by stimulating glucose uptake into insulin-dependent tissues as well as promoting hepatic glycogenesis. Given the increasing prevalence of T2DM worldwide, elucidating the underlying mechanisms and identifying the various players involved in the synthesis and exocytosis of insulin from β-cells is of utmost importance. This review summarizes our current understanding of the route insulin takes through the cell after its synthesis in the endoplasmic reticulum as well as our knowledge of the highly elaborate network that controls insulin release from the β-cell. This network harbors potential targets for anti-diabetic drugs and is regulated by signaling cascades from several endocrine systems.
Collapse
|
34
|
Müller TD, Finan B, Clemmensen C, DiMarchi RD, Tschöp MH. The New Biology and Pharmacology of Glucagon. Physiol Rev 2017; 97:721-766. [PMID: 28275047 DOI: 10.1152/physrev.00025.2016] [Citation(s) in RCA: 206] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In the last two decades we have witnessed sizable progress in defining the role of gastrointestinal signals in the control of glucose and energy homeostasis. Specifically, the molecular basis of the huge metabolic benefits in bariatric surgery is emerging while novel incretin-based medicines based on endogenous hormones such as glucagon-like peptide 1 and pancreas-derived amylin are improving diabetes management. These and related developments have fostered the discovery of novel insights into endocrine control of systemic metabolism, and in particular a deeper understanding of the importance of communication across vital organs, and specifically the gut-brain-pancreas-liver network. Paradoxically, the pancreatic peptide glucagon has reemerged in this period among a plethora of newly identified metabolic macromolecules, and new data complement and challenge its historical position as a gut hormone involved in metabolic control. The synthesis of glucagon analogs that are biophysically stable and soluble in aqueous solutions has promoted biological study that has enriched our understanding of glucagon biology and ironically recruited glucagon agonism as a central element to lower body weight in the treatment of metabolic disease. This review summarizes the extensive historical record and the more recent provocative direction that integrates the prominent role of glucagon in glucose elevation with its under-acknowledged effects on lipids, body weight, and vascular health that have implications for the pathophysiology of metabolic diseases, and the emergence of precision medicines to treat metabolic diseases.
Collapse
Affiliation(s)
- T D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - B Finan
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - C Clemmensen
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - R D DiMarchi
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - M H Tschöp
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| |
Collapse
|
35
|
Krasnyi AM, Volgina NE, Sadekova AA, Shchipitsyna VS, Sukhikh GT, Adamyan LV, Ozernyuk ND. Activation of α7-nicotinic acetylcholine receptors causes secretion of matrix metalloproteinases-9 in the human endometrium. BIOL BULL+ 2017. [DOI: 10.1134/s1062359017020078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
36
|
Sharif M, Silva E, Shah STA, Miller DJ. Redistribution of soluble N-ethylmaleimide-sensitive-factor attachment protein receptors in mouse sperm membranes prior to the acrosome reaction. Biol Reprod 2017; 96:352-365. [PMID: 28203732 DOI: 10.1095/biolreprod.116.143735] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 12/12/2016] [Accepted: 01/10/2017] [Indexed: 02/03/2023] Open
Abstract
Formation of complexes between soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) proteins on opposing membranes is the minimal requirement for intracellular membrane fusion. The SNARE, syntaxin 2, is found on the sperm plasma membrane and a second SNARE, vesicle associated membrane protein 2 (VAMP2, also known as synaptobrevin 2, SYB2), is on the apposing outer acrosomal membrane. During the acrosome reaction, the outer acrosomal membrane fuses at hundreds of points with the plasma membrane. We hypothesized that syntaxin 2 and VAMP2 redistribute within their respective membranes prior to the acrosome reaction to form trans-SNARE complexes and promote membrane fusion. Immunofluorescence and superresolution structured illumination microscopy were used to localize syntaxin 2 and VAMP2 in mouse sperm during capacitation. Initially, syntaxin 2 was found in puncta throughout the acrosomal region. At 60 and 120 min of capacitation, syntaxin 2 was localized in puncta primarily in the apical ridge. Although deletion of bicarbonate during incubation had no effect, syntaxin 2 puncta were relocated in the restricted region in less than 20% of sperm incubated without albumin. In contrast, VAMP2 was already found in puncta within the apical ridge prior to capacitation. The puncta containing syntaxin 2 and VAMP2 did not precisely co-localize at 0 or 60 min of capacitation time. In summary, syntaxin 2 shifted its location to the apical ridge on the plasma membrane during capacitation in an albumin-dependent manner but VAMP2 was already localized to the apical ridge. Puncta containing VAMP2 did not co-localize with those containing syntaxin 2 during capacitation; therefore, formation of trans-SNARE complexes containing these SNAREs does not occur until after capacitation, immediately prior to acrosomal exocytosis.
Collapse
Affiliation(s)
- Momal Sharif
- Institute of Animal Sciences, University of Agriculture, Faisalabad, Pakistan
| | - Elena Silva
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1207 West Gregory Drive, Urbana, IL, USA
| | - Syed Tahir Abbas Shah
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1207 West Gregory Drive, Urbana, IL, USA
| | - David J Miller
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1207 West Gregory Drive, Urbana, IL, USA
| |
Collapse
|
37
|
Nagaraj V, Kazim AS, Helgeson J, Lewold C, Barik S, Buda P, Reinbothe TM, Wennmalm S, Zhang E, Renström E. Elevated Basal Insulin Secretion in Type 2 Diabetes Caused by Reduced Plasma Membrane Cholesterol. Mol Endocrinol 2016; 30:1059-1069. [PMID: 27533789 PMCID: PMC5045496 DOI: 10.1210/me.2016-1023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Elevated basal insulin secretion under fasting conditions together with insufficient stimulated insulin release is an important hallmark of type 2 diabetes, but the mechanisms controlling basal insulin secretion remain unclear. Membrane rafts exist in pancreatic islet cells and spatially organize membrane ion channels and proteins controlling exocytosis, which may contribute to the regulation of insulin secretion. Membrane rafts (cholesterol and sphingolipid containing microdomains) were dramatically reduced in human type 2 diabetic and diabetic Goto-Kakizaki (GK) rat islets when compared with healthy islets. Oxidation of membrane cholesterol markedly reduced microdomain staining intensity in healthy human islets, but was without effect in type 2 diabetic islets. Intriguingly, oxidation of cholesterol affected glucose-stimulated insulin secretion only modestly, whereas basal insulin release was elevated. This was accompanied by increased intracellular Ca2+ spike frequency and Ca2+ influx and explained by enhanced single Ca2+ channel activity. These results suggest that the reduced presence of membrane rafts could contribute to the elevated basal insulin secretion seen in type 2 diabetes.
Collapse
Affiliation(s)
- Vini Nagaraj
- Department of Clinical Sciences Malmö (V.N., A.S.K., J.H., C.L., S.B., P.B., T.M.R., E.Z., E.R.), Lund University Diabetes Centre, Lund University, SE-20502 Malmö, Sweden; and Science for Life Laboratory (S.W.), KTH Royal Institute of Technology, SE-171 77 Stockholm, Sweden
| | - Abdulla S Kazim
- Department of Clinical Sciences Malmö (V.N., A.S.K., J.H., C.L., S.B., P.B., T.M.R., E.Z., E.R.), Lund University Diabetes Centre, Lund University, SE-20502 Malmö, Sweden; and Science for Life Laboratory (S.W.), KTH Royal Institute of Technology, SE-171 77 Stockholm, Sweden
| | - Johan Helgeson
- Department of Clinical Sciences Malmö (V.N., A.S.K., J.H., C.L., S.B., P.B., T.M.R., E.Z., E.R.), Lund University Diabetes Centre, Lund University, SE-20502 Malmö, Sweden; and Science for Life Laboratory (S.W.), KTH Royal Institute of Technology, SE-171 77 Stockholm, Sweden
| | - Clemens Lewold
- Department of Clinical Sciences Malmö (V.N., A.S.K., J.H., C.L., S.B., P.B., T.M.R., E.Z., E.R.), Lund University Diabetes Centre, Lund University, SE-20502 Malmö, Sweden; and Science for Life Laboratory (S.W.), KTH Royal Institute of Technology, SE-171 77 Stockholm, Sweden
| | - Satadal Barik
- Department of Clinical Sciences Malmö (V.N., A.S.K., J.H., C.L., S.B., P.B., T.M.R., E.Z., E.R.), Lund University Diabetes Centre, Lund University, SE-20502 Malmö, Sweden; and Science for Life Laboratory (S.W.), KTH Royal Institute of Technology, SE-171 77 Stockholm, Sweden
| | - Pawel Buda
- Department of Clinical Sciences Malmö (V.N., A.S.K., J.H., C.L., S.B., P.B., T.M.R., E.Z., E.R.), Lund University Diabetes Centre, Lund University, SE-20502 Malmö, Sweden; and Science for Life Laboratory (S.W.), KTH Royal Institute of Technology, SE-171 77 Stockholm, Sweden
| | - Thomas M Reinbothe
- Department of Clinical Sciences Malmö (V.N., A.S.K., J.H., C.L., S.B., P.B., T.M.R., E.Z., E.R.), Lund University Diabetes Centre, Lund University, SE-20502 Malmö, Sweden; and Science for Life Laboratory (S.W.), KTH Royal Institute of Technology, SE-171 77 Stockholm, Sweden
| | - Stefan Wennmalm
- Department of Clinical Sciences Malmö (V.N., A.S.K., J.H., C.L., S.B., P.B., T.M.R., E.Z., E.R.), Lund University Diabetes Centre, Lund University, SE-20502 Malmö, Sweden; and Science for Life Laboratory (S.W.), KTH Royal Institute of Technology, SE-171 77 Stockholm, Sweden
| | - Enming Zhang
- Department of Clinical Sciences Malmö (V.N., A.S.K., J.H., C.L., S.B., P.B., T.M.R., E.Z., E.R.), Lund University Diabetes Centre, Lund University, SE-20502 Malmö, Sweden; and Science for Life Laboratory (S.W.), KTH Royal Institute of Technology, SE-171 77 Stockholm, Sweden
| | - Erik Renström
- Department of Clinical Sciences Malmö (V.N., A.S.K., J.H., C.L., S.B., P.B., T.M.R., E.Z., E.R.), Lund University Diabetes Centre, Lund University, SE-20502 Malmö, Sweden; and Science for Life Laboratory (S.W.), KTH Royal Institute of Technology, SE-171 77 Stockholm, Sweden
| |
Collapse
|
38
|
Abstract
High-resolution deep tissue imaging is possible with two-photon excitation microscopy. With the combined application of two-photon imaging and perfusion with a polar fluorescent tracer, we have established a method to detect exocytic events inside secretory tissues. This method displays the spatiotemporal distribution of exocytic sites, dynamics of fusion pores, and modes of exocytosis. In glucose-stimulated pancreatic islets, exocytic events were observed to be synchronized with an increase in cytosolic Ca(2+) concentrations. Full fusion of a single secretory granule is the typical mode of exocytosis and compound exocytosis is inhibited. Because two-photon excitation enables simultaneous multicolor imaging due to the broadened excitation spectra, the distributions and conformational changes in fluorescent-labeled molecules can be simultaneously visualized with exocytic events. Therefore, we can analyze the dynamics of the molecules involved in membrane fusion and their association with exocytosis in living tissues.
Collapse
Affiliation(s)
- Noriko Takahashi
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo
| |
Collapse
|
39
|
Functional Analysis of Novel Candidate Regulators of Insulin Secretion in the MIN6 Mouse Pancreatic β Cell Line. PLoS One 2016; 11:e0151927. [PMID: 26986842 PMCID: PMC4795703 DOI: 10.1371/journal.pone.0151927] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 03/07/2016] [Indexed: 01/11/2023] Open
Abstract
Elucidating the regulation of glucose-stimulated insulin secretion (GSIS) in pancreatic β cells is important for understanding and treating diabetes. The pancreatic β cell line, MIN6, retains GSIS but gradually loses it in long-term culture. The MIN6 subclone, MIN6c4, exhibits well-regulated GSIS even after prolonged culture. We previously used DNA microarray analysis to compare gene expression in the parental MIN6 cells and MIN6c4 cells and identified several differentially regulated genes that may be involved in maintaining GSIS. Here we investigated the potential roles of six of these genes in GSIS: Tmem59l (Transmembrane protein 59 like), Scgn (Secretagogin), Gucy2c (Guanylate cyclase 2c), Slc29a4 (Solute carrier family 29, member 4), Cdhr1 (Cadherin-related family member 1), and Celsr2 (Cadherin EGF LAG seven-pass G-type receptor 2). These genes were knocked down in MIN6c4 cells using lentivirus vectors expressing gene-specific short hairpin RNAs (shRNAs), and the effects of the knockdown on insulin expression and secretion were analyzed. Suppression of Tmem59l, Scgn, and Gucy2c expression resulted in significantly decreased glucose- and/or KCl-stimulated insulin secretion from MIN6c4 cells, while the suppression of Slc29a4 expression resulted in increased insulin secretion. Tmem59l overexpression rescued the phenotype of the Tmem59l knockdown MIN6c4 cells, and immunostaining analysis indicated that the TMEM59L protein colocalized with insulin and GM130, a Golgi complex marker, in MIN6 cells. Collectively, our findings suggested that the proteins encoded by Tmem59l, Scgn, Gucy2c, and Slc29a4 play important roles in regulating GSIS. Detailed studies of these proteins and their functions are expected to provide new insights into the molecular mechanisms involved in insulin secretion.
Collapse
|
40
|
Schulze T, Morsi M, Brüning D, Schumacher K, Rustenbeck I. Different responses of mouse islets and MIN6 pseudo-islets to metabolic stimulation: a note of caution. Endocrine 2016; 51:440-7. [PMID: 26227244 DOI: 10.1007/s12020-015-0701-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Accepted: 07/20/2015] [Indexed: 11/25/2022]
Abstract
MIN6 cells and MIN6 pseudo-islets are popular surrogates for the use of primary beta cells and islets. Even though it is generally agreed that the stimulus-secretion coupling may deviate from that of beta cells or islets, direct comparisons are rare. The present side-by-side comparison of insulin secretion, cytosolic Ca(2+) concentration ([Ca(2+)] i ) and oxygen consumption rate (OCR) points out where similarities and differences exist between MIN6 cells and normal mouse beta cells. In mouse islets and MIN6 pseudo-islets depolarization by 40 mM KCl was a more robust insulinotropic stimulus than 30 mM glucose. In MIN6 pseudo-islets, but not in mouse islets, the response to 30 mM glucose was much lower than to 40 mM KCl and could be suppressed by a preceding stimulation with 40 mM KCl. In MIN6 pseudo-islets, glucose was less effective to raise [Ca(2+)] i than in primary islets. In marked contrast to islets, the OCR response of MIN6 pseudo-islets to 30 mM glucose was smaller than to 40 mM KCl and was further diminished by a preceding stimulation with 40 mM KCl. The same pattern was observed when MIN6 pseudo-islets were cultured in 5 mM glucose. As with insulin secretion memory effects on the OCR remained after wash-out of a stimulus. The differences between MIN6 cells and primary beta cells were generally larger in the responses to glucose than to depolarization by KCl. Thus, the use of MIN6 cells in investigations on metabolic signalling requires particular caution.
Collapse
Affiliation(s)
- Torben Schulze
- Institute of Pharmacology and Toxicology and Center of Pharmaceutical Engineering, University of Braunschweig, Mendelssohnstr. 1, 38106, Brunswick, Germany
| | - Mai Morsi
- Institute of Pharmacology and Toxicology and Center of Pharmaceutical Engineering, University of Braunschweig, Mendelssohnstr. 1, 38106, Brunswick, Germany
| | - Dennis Brüning
- Institute of Pharmacology and Toxicology and Center of Pharmaceutical Engineering, University of Braunschweig, Mendelssohnstr. 1, 38106, Brunswick, Germany
| | - Kirstin Schumacher
- Institute of Pharmacology and Toxicology and Center of Pharmaceutical Engineering, University of Braunschweig, Mendelssohnstr. 1, 38106, Brunswick, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology and Toxicology and Center of Pharmaceutical Engineering, University of Braunschweig, Mendelssohnstr. 1, 38106, Brunswick, Germany.
| |
Collapse
|
41
|
De Bock M, Van Haver V, Vandenbroucke RE, Decrock E, Wang N, Leybaert L. Into rather unexplored terrain-transcellular transport across the blood-brain barrier. Glia 2016; 64:1097-123. [DOI: 10.1002/glia.22960] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 11/16/2015] [Accepted: 12/03/2015] [Indexed: 01/22/2023]
Affiliation(s)
- Marijke De Bock
- Physiology Group, Department of Basic Medical Sciences; Ghent University; Ghent Belgium
| | - Valérie Van Haver
- Physiology Group, Department of Basic Medical Sciences; Ghent University; Ghent Belgium
| | - Roosmarijn E. Vandenbroucke
- Inflammation Research Center, VIB; Ghent Belgium
- Department of Biomedical Molecular Biology; Ghent University; Ghent Belgium
| | - Elke Decrock
- Physiology Group, Department of Basic Medical Sciences; Ghent University; Ghent Belgium
| | - Nan Wang
- Physiology Group, Department of Basic Medical Sciences; Ghent University; Ghent Belgium
| | - Luc Leybaert
- Physiology Group, Department of Basic Medical Sciences; Ghent University; Ghent Belgium
| |
Collapse
|
42
|
Di Cairano ES, Moretti S, Marciani P, Sacchi VF, Castagna M, Davalli A, Folli F, Perego C. Neurotransmitters and Neuropeptides: New Players in the Control of Islet of Langerhans' Cell Mass and Function. J Cell Physiol 2015; 231:756-67. [PMID: 26332080 DOI: 10.1002/jcp.25176] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 08/27/2015] [Indexed: 12/19/2022]
Abstract
Islets of Langerhans control whole body glucose homeostasis, as they respond, releasing hormones, to changes in nutrient concentrations in the blood stream. The regulation of hormone secretion has been the focus of attention for a long time because it is related to many metabolic disorders, including diabetes mellitus. Endocrine cells of the islet use a sophisticate system of endocrine, paracrine and autocrine signals to synchronize their activities. These signals provide a fast and accurate control not only for hormone release but also for cell differentiation and survival, key aspects in islet physiology and pathology. Among the different categories of paracrine/autocrine signals, this review highlights the role of neurotransmitters and neuropeptides. In a manner similar to neurons, endocrine cells synthesize, accumulate, release neurotransmitters in the islet milieu, and possess receptors able to decode these signals. In this review, we provide a comprehensive description of neurotransmitter/neuropetide signaling pathways present within the islet. Then, we focus on evidence supporting the concept that neurotransmitters/neuropeptides and their receptors are interesting new targets to preserve β-cell function and mass. A greater understanding of how this network of signals works in physiological and pathological conditions would advance our knowledge of islet biology and physiology and uncover potentially new areas of pharmacological intervention. J. Cell. Physiol. 231: 756-767, 2016. © 2015 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Eliana S Di Cairano
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| | - Stefania Moretti
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| | - Paola Marciani
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| | - Vellea Franca Sacchi
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| | - Michela Castagna
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| | - Alberto Davalli
- Department of Internal Medicine, Diabetes and Endocrinology Unit, San Raffaele Scientific Institute, Milan, Italy
| | - Franco Folli
- Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, Texas.,Department of Internal Medicine, Obesity and Comorbidities Research Center (OCRC), University of Campinas, UNICAMP, Campinas, Sao Paulo State, Brazil
| | - Carla Perego
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| |
Collapse
|
43
|
Conant K, Allen M, Lim ST. Activity dependent CAM cleavage and neurotransmission. Front Cell Neurosci 2015; 9:305. [PMID: 26321910 PMCID: PMC4531370 DOI: 10.3389/fncel.2015.00305] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 07/27/2015] [Indexed: 12/13/2022] Open
Abstract
Spatially localized proteolysis represents an elegant means by which neuronal activity dependent changes in synaptic structure, and thus experience dependent learning and memory, can be achieved. In vitro and in vivo studies suggest that matrix metalloproteinase and adamalysin activity is concentrated at the cell surface, and emerging evidence suggests that increased peri-synaptic expression, release and/or activation of these proteinases occurs with enhanced excitatory neurotransmission. Synaptically expressed cell adhesion molecules (CAMs) could therefore represent important targets for neuronal activity-dependent proteolysis. Several CAM subtypes are expressed at the synapse, and their cleavage can influence the efficacy of synaptic transmission through a variety of non-mutually exclusive mechanisms. In the following review, we discuss mechanisms that regulate neuronal activity-dependent synaptic CAM shedding, including those that may be calcium dependent. We also highlight CAM targets of activity-dependent proteolysis including neuroligin and intercellular adhesion molecule-5 (ICAM-5). We include discussion focused on potential consequences of synaptic CAM shedding, with an emphasis on interactions between soluble CAM cleavage products and specific pre- and post-synaptic receptors.
Collapse
Affiliation(s)
- Katherine Conant
- Department of Neuroscience and Interdisciplinary Program in Neuroscience, Georgetown University Medical Center Washington, DC, USA
| | - Megan Allen
- Department of Neuroscience and Interdisciplinary Program in Neuroscience, Georgetown University Medical Center Washington, DC, USA
| | - Seung T Lim
- Department of Neuroscience and Interdisciplinary Program in Neuroscience, Georgetown University Medical Center Washington, DC, USA
| |
Collapse
|
44
|
Synaptotagmin-7 phosphorylation mediates GLP-1-dependent potentiation of insulin secretion from β-cells. Proc Natl Acad Sci U S A 2015. [PMID: 26216970 DOI: 10.1073/pnas.1513004112] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Glucose stimulates insulin secretion from β-cells by increasing intracellular Ca(2+). Ca(2+) then binds to synaptotagmin-7 as a major Ca(2+) sensor for exocytosis, triggering secretory granule fusion and insulin secretion. In type-2 diabetes, insulin secretion is impaired; this impairment is ameliorated by glucagon-like peptide-1 (GLP-1) or by GLP-1 receptor agonists, which improve glucose homeostasis. However, the mechanism by which GLP-1 receptor agonists boost insulin secretion remains unclear. Here, we report that GLP-1 stimulates protein kinase A (PKA)-dependent phosphorylation of synaptotagmin-7 at serine-103, which enhances glucose- and Ca(2+)-stimulated insulin secretion and accounts for the improvement of glucose homeostasis by GLP-1. A phospho-mimetic synaptotagmin-7 mutant enhances Ca(2+)-triggered exocytosis, whereas a phospho-inactive synaptotagmin-7 mutant disrupts GLP-1 potentiation of insulin secretion. Our findings thus suggest that synaptotagmin-7 is directly activated by GLP-1 signaling and may serve as a drug target for boosting insulin secretion. Moreover, our data reveal, to our knowledge, the first physiological modulation of Ca(2+)-triggered exocytosis by direct phosphorylation of a synaptotagmin.
Collapse
|
45
|
Calcium sensitive ring-like oligomers formed by synaptotagmin. Proc Natl Acad Sci U S A 2014; 111:13966-71. [PMID: 25201968 DOI: 10.1073/pnas.1415849111] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The synaptic vesicle protein synaptotagmin-1 (SYT) is required to couple calcium influx to the membrane fusion machinery. However, the structural mechanism underlying this process is unclear. Here we report an unexpected circular arrangement (ring) of SYT's cytosolic domain (C2AB) formed on lipid monolayers in the absence of free calcium ions as revealed by electron microscopy. Rings vary in diameter from 18-43 nm, corresponding to 11-26 molecules of SYT. Continuous stacking of the SYT rings occasionally converts both lipid monolayers and bilayers into protein-coated tubes. Helical reconstruction of the SYT tubes shows that one of the C2 domains (most likely C2B, based on its biochemical properties) interacts with the membrane and is involved in ring formation, and the other C2 domain points radially outward. SYT rings are disrupted rapidly by physiological concentrations of free calcium but not by magnesium. Assuming that calcium-free SYT rings are physiologically relevant, these results suggest a simple and novel mechanism by which SYT regulates neurotransmitter release: The ring acts as a spacer to prevent the completion of the soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) complex assembly, thereby clamping fusion in the absence of calcium. When the ring disassembles in the presence of calcium, fusion proceeds unimpeded.
Collapse
|
46
|
The complement inhibitor CD59 regulates insulin secretion by modulating exocytotic events. Cell Metab 2014; 19:883-90. [PMID: 24726385 DOI: 10.1016/j.cmet.2014.03.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 12/22/2013] [Accepted: 02/11/2014] [Indexed: 12/21/2022]
Abstract
Type 2 diabetes is triggered by reduced insulin production, caused by genetic and environmental factors such as inflammation originating from the innate immune system. Complement proteins are a component of innate immunity and kill non-self cells by perforating the plasma membrane, a reaction prevented by CD59. Human pancreatic islets express CD59 at very high levels. CD59 is primarily known as a plasma membrane protein in membrane rafts, but most CD59 protein in pancreatic β cells is intracellular. Removing extracellular CD59 disrupts membrane rafts and moderately stimulates insulin secretion, whereas silencing intracellular CD59 markedly suppresses regulated secretion by exocytosis, as demonstrated by TIRF imaging. CD59 interacts with the exocytotic proteins VAMP2 and Syntaxin-1. CD59 expression is reduced by glucose and in rodent diabetes models but upregulated in human diabetic islets, potentially reflecting compensatory reactions. This unconventional action of CD59 broadens the established view of innate immunity in type 2 diabetes.
Collapse
|
47
|
Matz M, Schumacher K, Hatlapatka K, Lorenz D, Baumann K, Rustenbeck I. Observer-independent quantification of insulin granule exocytosis and pre-exocytotic mobility by TIRF microscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2014; 20:206-218. [PMID: 24230985 DOI: 10.1017/s1431927613013767] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Total internal reflection fluorescence microscopy of fluorescently labeled secretory granules permits monitoring of exocytosis and the preceding granule behavior in one experiment. While observer-dependent evaluation may be sufficient to quantify exocytosis, most of the other information contained in the video files cannot be accessed this way. The present program performs observer-independent detection of exocytosis and tracking of the entire submembrane population of insulin granules. A precondition is the exact localization of the peak of the granule fluorescence. Tracking is based on the peak base radius, peak intensity, and the precrossing itineraries. Robustness of the tracking was shown by simulated tracks of original granule patterns. Mobility in the X-Y dimension is described by the caging diameter which in contrast to the widely used mean square displacement has an inherent time resolution. Observer-independent detection of exocytosis in MIN6 cells labeled with insulin-EGFP is based on the maximal decrease in fluorescence intensity and position of the centroid of the dissipating cloud of released material. Combining the quantification of KCl-induced insulin exocytosis with the analysis of prefusion mobility showed that during the last 3 s pre-exocytotic granules had a smaller caging diameter than control granules and that it increased significantly immediately before fusion.
Collapse
Affiliation(s)
- Magnus Matz
- Institute of Medicinal and Pharmaceutical Chemistry, University of Braunschweig, Braunschweig D38106, Germany
| | - Kirstin Schumacher
- Institute of Pharmacology and Toxicology, University of Braunschweig, Braunschweig D38106, Germany
| | - Kathrin Hatlapatka
- Institute of Pharmacology and Toxicology, University of Braunschweig, Braunschweig D38106, Germany
| | - Dirk Lorenz
- Institute of Analysis and Algebra, University of Braunschweig, Braunschweig D38106, Germany
| | - Knut Baumann
- Institute of Medicinal and Pharmaceutical Chemistry, University of Braunschweig, Braunschweig D38106, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology and Toxicology, University of Braunschweig, Braunschweig D38106, Germany
| |
Collapse
|
48
|
Gutierrez-Aguilar R, Kim DH, Casimir M, Dai XQ, Pfluger PT, Park J, Haller A, Donelan E, Park J, D’Alessio D, Woods SC, MacDonald PE, Seeley RJ. The role of the transcription factor ETV5 in insulin exocytosis. Diabetologia 2014; 57:383-91. [PMID: 24190582 PMCID: PMC3947344 DOI: 10.1007/s00125-013-3096-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 10/09/2013] [Indexed: 12/15/2022]
Abstract
AIMS/HYPOTHESIS Genome-wide association studies have revealed an association of the transcription factor ETS variant gene 5 (ETV5) with human obesity. However, its role in glucose homeostasis and energy balance is unknown. METHODS Etv5 knockout (KO) mice were monitored weekly for body weight (BW) and food intake. Body composition was measured at 8 and 16 weeks of age. Glucose metabolism was studied, and glucose-stimulated insulin secretion was measured in vivo and in vitro. RESULTS Etv5 KO mice are smaller and leaner, and have a reduced BW and lower fat mass than their wild-type controls on a chow diet. When exposed to a high-fat diet, KO mice are resistant to diet-induced BW gain. Despite a greater insulin sensitivity, KO mice have profoundly impaired glucose tolerance associated with impaired insulin secretion. Morphometric analysis revealed smaller islets and a reduced beta cell size in the pancreatic islets of Etv5 KO mice. Knockdown of ETV5 in an insulin-secreting cell line or beta cells from human donors revealed intact mitochondrial and Ca(2+) channel activity, but reduced insulin exocytosis. CONCLUSION/INTERPRETATION This work reveals a critical role for ETV5 in specifically regulating insulin secretion both in vitro and in vivo.
Collapse
Affiliation(s)
- Ruth Gutierrez-Aguilar
- Department of Internal Medicine, University of Cincinnati, 2170 East Galbraith Road, Cincinnati, OH 45237, USA
| | - Dong-Hoon Kim
- Department of Pharmacology, Korea University College of Medicine, Seoul, South Korea
| | - Marina Casimir
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Xiao-Qing Dai
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Paul T. Pfluger
- Institute for Diabetes and Obesity, Helmholtz Centre Munich, Neuherberg, Germany
| | - Jongsun Park
- Department of Pharmacology, College of Medicine, Chungnam National University, Daejeon, South Korea
| | - April Haller
- Department of Internal Medicine, University of Cincinnati, 2170 East Galbraith Road, Cincinnati, OH 45237, USA
| | - Elizabeth Donelan
- Department of Internal Medicine, University of Cincinnati, 2170 East Galbraith Road, Cincinnati, OH 45237, USA
| | - Jisoo Park
- Department of Pharmacology, College of Medicine, Chungnam National University, Daejeon, South Korea
| | - David D’Alessio
- Department of Internal Medicine, University of Cincinnati, 2170 East Galbraith Road, Cincinnati, OH 45237, USA
| | - Stephen C. Woods
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH, USA
| | - Patrick E. MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Randy J. Seeley
- Department of Internal Medicine, University of Cincinnati, 2170 East Galbraith Road, Cincinnati, OH 45237, USA
| |
Collapse
|
49
|
Morvan J, Gehart H, Ricci R. [Arfaptine-1 controls secretory granule biogenesis]. Med Sci (Paris) 2013; 29:247-9. [PMID: 23544374 DOI: 10.1051/medsci/2013293006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
50
|
Andersson SA, Olsson AH, Esguerra JLS, Heimann E, Ladenvall C, Edlund A, Salehi A, Taneera J, Degerman E, Groop L, Ling C, Eliasson L. Reduced insulin secretion correlates with decreased expression of exocytotic genes in pancreatic islets from patients with type 2 diabetes. Mol Cell Endocrinol 2012; 364:36-45. [PMID: 22939844 DOI: 10.1016/j.mce.2012.08.009] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 08/07/2012] [Accepted: 08/13/2012] [Indexed: 02/06/2023]
Abstract
Reduced insulin release has been linked to defect exocytosis in β-cells. However, whether expression of genes suggested to be involved in the exocytotic process (exocytotic genes) is altered in pancreatic islets from patients with type 2 diabetes (T2D), and correlate to insulin secretion, needs to be further investigated. Analysing expression levels of 23 exocytotic genes using microarray revealed reduced expression of five genes in human T2D islets (χ(2)=13.25; p<0.001). Gene expression of STX1A, SYT4, SYT7, SYT11, SYT13, SNAP25 and STXBP1 correlated negatively to in vivo measurements of HbA1c levels and positively to glucose stimulated insulin secretion (GSIS) in vitro in human islets. STX1A, SYT4 and SYT11 protein levels correspondingly decreased in human T2D islets. Moreover, silencing of SYT4 and SYT13 reduced GSIS in INS1-832/13 cells. Our data support that reduced expression of exocytotic genes contributes to impaired insulin secretion, and suggest decreased expression of these genes as part of T2D pathogenesis.
Collapse
Affiliation(s)
- Sofia A Andersson
- Islet Cell Exocytosis, Lund University Diabetes Centre, Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|