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Wang Y, Yang H, Li N, Wang L, Guo C, Ma W, Liu S, Peng C, Chen J, Song H, Chen H, Ma X, Yi J, Lian J, Kong W, Dong J, Tu X, Shah M, Tian X, Huang Z. A Novel Ubiquitin Ligase Adaptor PTPRN Suppresses Seizure Susceptibility through Endocytosis of Na V1.2 Sodium Channels. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2400560. [PMID: 38874331 DOI: 10.1002/advs.202400560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 05/06/2024] [Indexed: 06/15/2024]
Abstract
Intrinsic plasticity, a fundamental process enabling neurons to modify their intrinsic properties, plays a crucial role in shaping neuronal input-output function and is implicated in various neurological and psychiatric disorders. Despite its importance, the underlying molecular mechanisms of intrinsic plasticity remain poorly understood. In this study, a new ubiquitin ligase adaptor, protein tyrosine phosphatase receptor type N (PTPRN), is identified as a regulator of intrinsic neuronal excitability in the context of temporal lobe epilepsy. PTPRN recruits the NEDD4 Like E3 Ubiquitin Protein Ligase (NEDD4L) to NaV1.2 sodium channels, facilitating NEDD4L-mediated ubiquitination, and endocytosis of NaV1.2. Knockout of PTPRN in hippocampal granule cells leads to augmented NaV1.2-mediated sodium currents and higher intrinsic excitability, resulting in increased seizure susceptibility in transgenic mice. Conversely, adeno-associated virus-mediated delivery of PTPRN in the dentate gyrus region decreases intrinsic excitability and reduces seizure susceptibility. Moreover, the present findings indicate that PTPRN exerts a selective modulation effect on voltage-gated sodium channels. Collectively, PTPRN plays a significant role in regulating intrinsic excitability and seizure susceptibility, suggesting a potential strategy for precise modulation of NaV1.2 channels' function.
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Affiliation(s)
- Yifan Wang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Hui Yang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Na Li
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Lili Wang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Chang Guo
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Weining Ma
- Department of Neurology, Shengjing Hospital Affiliated to China Medical University, Shenyang, 110022, China
| | - Shiqi Liu
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Chao Peng
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Jiexin Chen
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Huifang Song
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Hedan Chen
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Xinyue Ma
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Jingyun Yi
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Jingjing Lian
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Weikaixin Kong
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Jie Dong
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Xinyu Tu
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Mala Shah
- UCL School of Pharmacy, University College London, London, WC1N 1AX, UK
| | - Xin Tian
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing, 400016, China
| | - Zhuo Huang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
- IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
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2
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Huang J, Tiu AC, Jose PA, Yang J. Sorting nexins: role in the regulation of blood pressure. FEBS J 2023; 290:600-619. [PMID: 34847291 PMCID: PMC9149145 DOI: 10.1111/febs.16305] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 10/13/2021] [Accepted: 11/29/2021] [Indexed: 02/06/2023]
Abstract
Sorting nexins (SNXs) are a family of proteins that regulate cellular cargo sorting and trafficking, maintain intracellular protein homeostasis, and participate in intracellular signaling. SNXs are also important in the regulation of blood pressure via several mechanisms. Aberrant expression and dysfunction of SNXs participate in the dysregulation of blood pressure. Genetic studies show a correlation between SNX gene variants and the response to antihypertensive drugs. In this review, we summarize the progress in SNX-mediated regulation of blood pressure, discuss the potential role of SNXs in the pathophysiology and treatment of hypertension, and propose novel strategies for the medical therapy of hypertension.
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Affiliation(s)
- Juan Huang
- Department of Clinical Nutrition, The Third Affiliated Hospital of Chongqing Medical University, Chongqing 410020, P.R. China
| | - Andrew C. Tiu
- Department of Medicine, Einstein Medical Center Philadelphia, Philadelphia, PA 19141, USA
| | - Pedro A. Jose
- Division of Renal Diseases & Hypertension, Department of Medicine, and Department of Physiology and Pharmacology, The George Washington University School of Medicine & Health Sciences, Washington, DC 20052, USA
| | - Jian Yang
- Department of Clinical Nutrition, The Third Affiliated Hospital of Chongqing Medical University, Chongqing 410020, P.R. China
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3
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Ali MB, Dreger DL, Buckley RM, Mansoor S, Khan QM, Ostrander EA. Genetic Origins of the Two Canis lupus familiaris (Dog) Freight Dog Populations. J Hered 2022; 113:160-170. [PMID: 35575082 PMCID: PMC9113510 DOI: 10.1093/jhered/esac002] [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: 10/28/2021] [Accepted: 01/24/2022] [Indexed: 01/27/2023] Open
Abstract
Despite periodic drops in popularity, Arctic sled dogs continue to play a vital role in northern societies, providing both freight transit and recreational race activities. In this study, we selected the Mackenzie River Husky, a freight dog of complex history, and the Chinook, an American Kennel Club recognized freight dog breed whose heritage reportedly overlaps that of the MKRH, for detailed population analysis. We tested each to determine their component breeds and used admixture analysis to ascertain their population structure. We utilized haplotype analysis to identify genomic regions shared between each population and their founding breeds. Our data show that the Alaskan Malamutes and modern Greenland sled dog contributed to both populations, but there are also unexpected contributions from the German Shepherd dog and Collie. We used haplotype analysis to identify genomic regions nearing fixation in population type and identify provocative genes in each region. Finally, in response to recent reports regarding the importance of dietary lipid genes in Arctic dogs, we analyzed 8 such genes in a targeted analysis observing signatures of selection in both populations at the MLXIPL gene loci. These data highlight the genetic routes that breeds of similar function have taken toward their occupation as successful sled dogs.
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Affiliation(s)
- Muhammad Basil Ali
- National Institute for Biotechnology and Genetic Engineering College (NIBGE), Faisalabad, Pakistan
- Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Dayna L Dreger
- National Human Genome Research Institute, National Institutes of Health, 50 South Drive, Building 51, Room 5351, Bethesda, MD 20892, USA
| | - Reuben M Buckley
- National Human Genome Research Institute, National Institutes of Health, 50 South Drive, Building 51, Room 5351, Bethesda, MD 20892, USA
| | - Shahid Mansoor
- National Institute for Biotechnology and Genetic Engineering College (NIBGE), Faisalabad, Pakistan
- Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Qaiser M Khan
- National Institute for Biotechnology and Genetic Engineering College (NIBGE), Faisalabad, Pakistan
- Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Elaine A Ostrander
- National Human Genome Research Institute, National Institutes of Health, 50 South Drive, Building 51, Room 5351, Bethesda, MD 20892, USA
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4
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Weidle UH, Nopora A. MicroRNAs Involved in Small-cell Lung Cancer as Possible Agents for Treatment and Identification of New Targets. Cancer Genomics Proteomics 2021; 18:591-603. [PMID: 34479913 DOI: 10.21873/cgp.20283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 07/13/2021] [Accepted: 07/15/2021] [Indexed: 11/10/2022] Open
Abstract
Small-cell lung cancer, a neuro-endocrine type of lung cancers, responds very well to chemotherapy-based agents. However, a high frequency of relapse due to adaptive resistance is observed. Immunotherapy-based treatments with checkpoint inhibitors has resulted in improvement of treatment but the responses are not as impressive as in other types of tumor. Therefore, identification of new targets and treatment modalities is an important issue. After searching the literature, we identified eight down-regulated microRNAs involved in radiation- and chemotherapy-induced resistance, as well as three up-regulated and four down-regulated miRNAs with impacts on proliferation, invasion and apoptosis of small-cell lung cancer cells in vitro. Furthermore, one up-regulated and four down-regulated microRNAs with in vivo activity in SCLC cell xenografts were identified. The identified microRNAs are candidates for inhibition or reconstitution therapy. The corresponding targets are candidates for inhibition or functional reconstitution with antibody-based moieties or small molecules.
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Affiliation(s)
- Ulrich H Weidle
- Roche Pharma Research and Early Development, Roche Innovation Center Munich, Penzberg, Germany
| | - Adam Nopora
- Roche Pharma Research and Early Development, Roche Innovation Center Munich, Penzberg, Germany
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5
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Saric A, Freeman SA, Williamson CD, Jarnik M, Guardia CM, Fernandopulle MS, Gershlick DC, Bonifacino JS. SNX19 restricts endolysosome motility through contacts with the endoplasmic reticulum. Nat Commun 2021; 12:4552. [PMID: 34315878 PMCID: PMC8316374 DOI: 10.1038/s41467-021-24709-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 06/24/2021] [Indexed: 12/12/2022] Open
Abstract
The ability of endolysosomal organelles to move within the cytoplasm is essential for the performance of their functions. Long-range movement involves coupling of the endolysosomes to motor proteins that carry them along microtubule tracks. This movement is influenced by interactions with other organelles, but the mechanisms involved are incompletely understood. Herein we show that the sorting nexin SNX19 tethers endolysosomes to the endoplasmic reticulum (ER), decreasing their motility and contributing to their concentration in the perinuclear area of the cell. Tethering depends on two N-terminal transmembrane domains that anchor SNX19 to the ER, and a PX domain that binds to phosphatidylinositol 3-phosphate on the endolysosomal membrane. Two other domains named PXA and PXC negatively regulate the interaction of SNX19 with endolysosomes. These studies thus identify a mechanism for controlling the motility and positioning of endolysosomes that involves tethering to the ER by a sorting nexin.
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Affiliation(s)
- Amra Saric
- Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Spencer A Freeman
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Chad D Williamson
- Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Michal Jarnik
- Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Carlos M Guardia
- Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Michael S Fernandopulle
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - David C Gershlick
- Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Juan S Bonifacino
- Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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6
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Amatya B, Lee H, Asico LD, Konkalmatt P, Armando I, Felder RA, Jose PA. SNX-PXA-RGS-PXC Subfamily of SNXs in the Regulation of Receptor-Mediated Signaling and Membrane Trafficking. Int J Mol Sci 2021; 22:ijms22052319. [PMID: 33652569 PMCID: PMC7956473 DOI: 10.3390/ijms22052319] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 02/13/2021] [Accepted: 02/22/2021] [Indexed: 12/26/2022] Open
Abstract
The SNX-PXA-RGS-PXC subfamily of sorting nexins (SNXs) belongs to the superfamily of SNX proteins. SNXs are characterized by the presence of a common phox-homology (PX) domain, along with other functional domains that play versatile roles in cellular signaling and membrane trafficking. In addition to the PX domain, the SNX-PXA-RGS-PXC subfamily, except for SNX19, contains a unique RGS (regulators of G protein signaling) domain that serves as GTPase activating proteins (GAPs), which accelerates GTP hydrolysis on the G protein α subunit, resulting in termination of G protein-coupled receptor (GPCR) signaling. Moreover, the PX domain selectively interacts with phosphatidylinositol-3-phosphate and other phosphoinositides found in endosomal membranes, while also associating with various intracellular proteins. Although SNX19 lacks an RGS domain, all members of the SNX-PXA-RGS-PXC subfamily serve as dual regulators of receptor cargo signaling and endosomal trafficking. This review discusses the known and proposed functions of the SNX-PXA-RGS-PXC subfamily and how it participates in receptor signaling (both GPCR and non-GPCR) and endosomal-based membrane trafficking. Furthermore, we discuss the difference of this subfamily of SNXs from other subfamilies, such as SNX-BAR nexins (Bin-Amphiphysin-Rvs) that are associated with retromer or other retrieval complexes for the regulation of receptor signaling and membrane trafficking. Emerging evidence has shown that the dysregulation and malfunction of this subfamily of sorting nexins lead to various pathophysiological processes and disorders, including hypertension.
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Affiliation(s)
- Bibhas Amatya
- The George Washington University, Washington, DC 20052, USA;
| | - Hewang Lee
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC 20052, USA; (H.L.); (L.D.A.); (P.K.); (I.A.)
| | - Laureano D. Asico
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC 20052, USA; (H.L.); (L.D.A.); (P.K.); (I.A.)
| | - Prasad Konkalmatt
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC 20052, USA; (H.L.); (L.D.A.); (P.K.); (I.A.)
| | - Ines Armando
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC 20052, USA; (H.L.); (L.D.A.); (P.K.); (I.A.)
| | - Robin A. Felder
- Department of Pathology, University of Virginia Health Sciences Center, Charlottesville, VA 22908, USA;
| | - Pedro A. Jose
- Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC 20052, USA; (H.L.); (L.D.A.); (P.K.); (I.A.)
- Department of Pathology, University of Virginia Health Sciences Center, Charlottesville, VA 22908, USA;
- Department of Pharmacology/Physiology, The George Washington University School of Medicine & Health Sciences, Washington, DC 20052, USA
- Correspondence:
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7
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Harrison NJ, Connolly E, Gascón Gubieda A, Yang Z, Altenhein B, Losada Perez M, Moreira M, Sun J, Hidalgo A. Regenerative neurogenic response from glia requires insulin-driven neuron-glia communication. eLife 2021; 10:58756. [PMID: 33527895 PMCID: PMC7880684 DOI: 10.7554/elife.58756] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Accepted: 02/01/2021] [Indexed: 12/21/2022] Open
Abstract
Understanding how injury to the central nervous system induces de novo neurogenesis in animals would help promote regeneration in humans. Regenerative neurogenesis could originate from glia and glial neuron-glia antigen-2 (NG2) may sense injury-induced neuronal signals, but these are unknown. Here, we used Drosophila to search for genes functionally related to the NG2 homologue kon-tiki (kon), and identified Islet Antigen-2 (Ia-2), required in neurons for insulin secretion. Both loss and over-expression of ia-2 induced neural stem cell gene expression, injury increased ia-2 expression and induced ectopic neural stem cells. Using genetic analysis and lineage tracing, we demonstrate that Ia-2 and Kon regulate Drosophila insulin-like peptide 6 (Dilp-6) to induce glial proliferation and neural stem cells from glia. Ectopic neural stem cells can divide, and limited de novo neurogenesis could be traced back to glial cells. Altogether, Ia-2 and Dilp-6 drive a neuron-glia relay that restores glia and reprogrammes glia into neural stem cells for regeneration.
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Affiliation(s)
- Neale J Harrison
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Elizabeth Connolly
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Alicia Gascón Gubieda
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Zidan Yang
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | | | - Maria Losada Perez
- Instituto Cajal, Consejo Superior de Investigaciones Cientificas (CSIC), Madrid, Spain
| | - Marta Moreira
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Jun Sun
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Alicia Hidalgo
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
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8
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Ma L, Semick SA, Chen Q, Li C, Tao R, Price AJ, Shin JH, Jia Y, Brandon NJ, Cross AJ, Hyde TM, Kleinman JE, Jaffe AE, Weinberger DR, Straub RE. Schizophrenia risk variants influence multiple classes of transcripts of sorting nexin 19 (SNX19). Mol Psychiatry 2020; 25:831-843. [PMID: 30635639 DOI: 10.1038/s41380-018-0293-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 09/16/2018] [Accepted: 10/03/2018] [Indexed: 01/15/2023]
Abstract
Genome-wide association studies (GWAS) have identified many genomic loci associated with risk for schizophrenia, but unambiguous identification of the relationship between disease-associated variants and specific genes, and in particular their effect on risk conferring transcripts, has proven difficult. To better understand the specific molecular mechanism(s) at the schizophrenia locus in 11q25, we undertook cis expression quantitative trait loci (cis-eQTL) mapping for this 2 megabase genomic region using postmortem human brain samples. To comprehensively assess the effects of genetic risk upon local expression, we evaluated multiple transcript features: genes, exons, and exon-exon junctions in multiple brain regions-dorsolateral prefrontal cortex (DLPFC), hippocampus, and caudate. Genetic risk variants strongly associated with expression of SNX19 transcript features that tag multiple rare classes of SNX19 transcripts, whereas they only weakly affected expression of an exon-exon junction that tags the majority of abundant transcripts. The most prominent class of SNX19 risk-associated transcripts is predicted to be overexpressed, defined by an exon-exon splice junction between exons 8 and 10 (junc8.10) and that is predicted to encode proteins that lack the characteristic nexin C terminal domain. Risk alleles were also associated with either increased or decreased expression of multiple additional classes of transcripts. With RACE, molecular cloning, and long read sequencing, we found a number of novel SNX19 transcripts that further define the set of potential etiological transcripts. We explored epigenetic regulation of SNX19 expression and found that DNA methylation at CpG sites near the primary transcription start site and within exon 2 partially mediate the effects of risk variants on risk-associated expression. ATAC sequencing revealed that some of the most strongly risk-associated SNPs are located within a region of open chromatin, suggesting a nearby regulatory element is involved. These findings indicate a potentially complex molecular etiology, in which risk alleles for schizophrenia generate epigenetic alterations and dysregulation of multiple classes of SNX19 transcripts.
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Affiliation(s)
- Liang Ma
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA
| | - Stephen A Semick
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA
| | - Qiang Chen
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA
| | - Chao Li
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA
| | - Ran Tao
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA
| | - Amanda J Price
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA.,McKusick-Nathans Institute of Genetic Medicine, Baltimore, MD, 21205, USA
| | - Joo Heon Shin
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA
| | - Yankai Jia
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA
| | | | - Nicholas J Brandon
- AstraZeneca Neuroscience, IMED Biotech Unit, AstraZeneca R&D, Boston, MA, 02451, USA
| | - Alan J Cross
- AstraZeneca Neuroscience, IMED Biotech Unit, AstraZeneca R&D, Boston, MA, 02451, USA
| | - Thomas M Hyde
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA.,Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Joel E Kleinman
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA.,Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Andrew E Jaffe
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA.,Department of Mental Health, Johns Hopkins School of Public Health, Baltimore, MD, 21205, USA.,Department of Biostatistics, Johns Hopkins School of Public Health, Baltimore, MD, 21205, USA
| | - Daniel R Weinberger
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA.,McKusick-Nathans Institute of Genetic Medicine, Baltimore, MD, 21205, USA.,Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.,Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Richard E Straub
- Lieber Institute for Brain Development, Baltimore, MD, 21205, USA.
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9
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Mziaut H, Mulligan B, Hoboth P, Otto O, Ivanova A, Herbig M, Schumann D, Hildebrandt T, Dehghany J, Sönmez A, Münster C, Meyer-Hermann M, Guck J, Kalaidzidis Y, Solimena M. The F-actin modifier villin regulates insulin granule dynamics and exocytosis downstream of islet cell autoantigen 512. Mol Metab 2016; 5:656-668. [PMID: 27656403 PMCID: PMC5021679 DOI: 10.1016/j.molmet.2016.05.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 05/20/2016] [Accepted: 05/24/2016] [Indexed: 01/02/2023] Open
Abstract
Objective Insulin release from pancreatic islet β cells should be tightly controlled to avoid hypoglycemia and insulin resistance. The cortical actin cytoskeleton is a gate for regulated exocytosis of insulin secretory granules (SGs) by restricting their mobility and access to the plasma membrane. Prior studies suggest that SGs interact with F-actin through their transmembrane cargo islet cell autoantigen 512 (Ica512) (also known as islet antigen 2/Ptprn). Here we investigated how Ica512 modulates SG trafficking and exocytosis. Methods Transcriptomic changes in Ica512−/− mouse islets were analyzed. Imaging as well as biophysical and biochemical methods were used to validate if and how the Ica512-regulated gene villin modulates insulin secretion in mouse islets and insulinoma cells. Results The F-actin modifier villin was consistently downregulated in Ica512−/− mouse islets and in Ica512-depleted insulinoma cells. Villin was enriched at the cell cortex of β cells and dispersed villin−/− islet cells were less round and less deformable. Basal mobility of SGs in villin-depleted cells was enhanced. Moreover, in cells depleted either of villin or Ica512 F-actin cages restraining cortical SGs were enlarged, basal secretion was increased while glucose-stimulated insulin release was blunted. The latter changes were reverted by overexpressing villin in Ica512-depleted cells, but not vice versa. Conclusion Our findings show that villin controls the size of the F-actin cages restricting SGs and, thus, regulates their dynamics and availability for exocytosis. Evidence that villin acts downstream of Ica512 also indicates that SGs directly influence the remodeling properties of the cortical actin cytoskeleton for tight control of insulin secretion. Ica512-depletion reduces the genetic expression of the F-actin modifier villin. Villin-depletion enhances basal insulin granule mobility and exocytosis. Villin regulates the size of actin cages restraining insulin granules. Villin acts downstream of insulin granule cargo Ica512. The Ica512-villin genetic link enables granules to control cytoskeleton plasticity.
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Key Words
- D, diffusion coefficient
- EGFP, enhanced green fluorescent protein
- F-actin
- Granules
- IPGTT, intraperitoneal glucose tolerance test
- IVGTT, intravenous glucose tolerance test
- Ica512
- Ica512, islet cell autoantigen
- Insulin
- OGTT, oral glucose tolerance test
- RT-DC, real-time deformability cytometry
- SE, standard error
- SG, secretory granules
- Secretion
- TIRFM, total internal reflection fluorescence microscopy
- Villin
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Affiliation(s)
- Hassan Mziaut
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Bernard Mulligan
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Peter Hoboth
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Oliver Otto
- Biotechnology Center Dresden, 01307 Dresden, Germany
| | - Anna Ivanova
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Maik Herbig
- Biotechnology Center Dresden, 01307 Dresden, Germany
| | - Desiree Schumann
- Boehringer Ingelheim Pharma GmbH & Co. KG. Cardiometabolic Research, 88397 Biberach, Germany
| | - Tobias Hildebrandt
- Boehringer Ingelheim Pharma GmbH & Co. KG. Cardiometabolic Research, 88397 Biberach, Germany
| | - Jaber Dehghany
- Helmholtz Centre for Infection Research (HZI), Braunschweig Integrated Centre for Systems Biology (BRICS), 38124 Braunschweig, Germany
| | - Anke Sönmez
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Carla Münster
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Michael Meyer-Hermann
- Helmholtz Centre for Infection Research (HZI), Braunschweig Integrated Centre for Systems Biology (BRICS), 38124 Braunschweig, Germany
| | - Jochen Guck
- Biotechnology Center Dresden, 01307 Dresden, Germany
| | - Yannis Kalaidzidis
- Max Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Michele Solimena
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany; Max Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
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10
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Abstract
Islet autoantibodies are the main markers of pancreatic autoimmunity in type 1 diabetes (T1D). Islet autoantibodies recognize insulin (IAA), glutamic acid decarboxylase (GADA), protein phosphatase-like IA-2 (IA-2A), and ZnT8 (ZnT8A), all antigens that are found on secretory granules within pancreatic beta cells. Islet antibodies, measured by sensitive and specific liquid phase assays, are the key parameters of the autoimmune response monitored for diagnostics or prognostics in patients with T1D or for disease prediction in at-risk individuals before T1D onset. Islet autoantibodies have been the main tool used to explore the natural history of T1D; this review summarizes the current knowledge about the autoantigens and the phenotype of islets autoantibodies acquired in large prospective studies from birth in children at risk of developing T1D.
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Affiliation(s)
- Vito Lampasona
- Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milano, Italy.
- Diabetes Research Institute, IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milano, Italy.
| | - Daniela Liberati
- Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milano, Italy
- Diabetes Research Institute, IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milano, Italy
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11
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Biochemical, biophysical, and functional properties of ICA512/IA-2 RESP18 homology domain. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:511-22. [DOI: 10.1016/j.bbapap.2016.01.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 01/04/2016] [Accepted: 01/29/2016] [Indexed: 02/04/2023]
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12
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Harashima SI, Horiuchi T, Wang Y, Notkins AL, Seino Y, Inagaki N. Sorting nexin 19 regulates the number of dense core vesicles in pancreatic β-cells. J Diabetes Investig 2014; 3:52-61. [PMID: 24843546 PMCID: PMC4014933 DOI: 10.1111/j.2040-1124.2011.00138.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Aims/Introduction: Insulinoma‐associated protein 2 (IA‐2) regulates insulin secretion and the number of dense core vesicles (DCV). However, the mechanism of regulation of DCV number by IA‐2 is unknown. We examined the effect of sorting nexin 19 (SNX19), an IA‐2 interacting protein, on insulin secretion and the number of dense core vesicles (DCV). Materials and Methods: Stable SNX19 knockdown (SNX19KD) MIN6, a mouse pancreatic β‐cell line, and stable SNX19‐reintroduced SNX19KD MIN6 were established. Quantification of DCV, and lysosomes was carried out using electron micrographs. The half‐life of DCV was detected by pulse‐chase experiment. Results: Insulin secretion and content were decreased in stable SNX19KD MIN6 cells compared with those in control MIN6 cells. Electron micrographs showed that DCV number in SNX19KD cells was decreased by approximately 75% and that DCV size was decreased by approximately 40% compared with those in control cells, respectively. Furthermore, when SNX19 was reintroduced in SNX19KD cells, insulin content, insulin secretion and DCV number were increased. The half‐life of DCV was decreased in SNX19KD cells, but was increased in SNX19KD cells in which SNX19 was reintroduced. The number of lysosomes and the activity of lysosome enzyme cathepsin D were increased by approximately threefold in SNX19KD cells compared with those in control cells. In contrast, they were decreased to approximately half to one‐third in SNX19‐reintroduced SNX19KD cells. Conclusions: SNX19 regulates the number of DCV and insulin content by stabilizing DCV in β‐cells. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00138.x, 2012)
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Affiliation(s)
- Shin-Ichi Harashima
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto
| | - Takahiko Horiuchi
- Department of Medicine and Biosystemic Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yu Wang
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto
| | - Abner Louis Notkins
- Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research (NIDCR), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Yutaka Seino
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto
| | - Nobuya Inagaki
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto
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13
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Massa O, Alessio M, Russo L, Nardo G, Bonetto V, Bertuzzi F, Paladini A, Iafusco D, Patera P, Federici G, Not T, Tiberti C, Bonfanti R, Barbetti F. Serological Proteome Analysis (SERPA) as a tool for the identification of new candidate autoantigens in type 1 diabetes. J Proteomics 2013; 82:263-73. [PMID: 23500132 DOI: 10.1016/j.jprot.2013.02.030] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Revised: 02/26/2013] [Accepted: 02/27/2013] [Indexed: 01/28/2023]
Abstract
UNLABELLED Type 1 diabetes (T1D) is an autoimmune disease characterized by the presence of circulating autoantibodies directed against proteins of islet beta-cell. Autoantibody testing is used for diagnostic purposes; however, up to 2-5% of patients who are clinically diagnosed with T1D are found negative for known antibodies, suggesting that the T1D autoantigen panel is incomplete. With the aim of identifying new T1D autoantigen(s), we used sera from subjects clinically diagnosed with T1D, but who tested negative for the four T1D autoantibodies currently used in clinical practice and for genes responsible for sporadic cases of diabetes. Sera from these patients were challenged by Western blot against the proteome from human pancreatic beta-cells resolved by 2DE. Eleven proteins were identified by MS. A radiobinding assay (RBA) was developed to test the reactivity to Rab GDP dissociation inhibitor beta (GDIβ) of T1D sera using an independent method. Depending on the construct used (open reading frame or COOH-terminus) 22% to 32% of fifty T1D sera showed increased binding to GDIβ by RBA. In addition, 15% of patients with celiac disease had raised binding to the COOH-terminus GDIβ. These results indicate that immunoproteomics is a feasible strategy for the identification of candidate T1D autoantigens. BIOLOGICAL SIGNIFICANCE Several approaches have been previously used to look for new type 1 diabetes autoantigens. With the present work we show that carefully selected sera from rare patients with diabetes both negative for the 5 autoantibodies currently used in clinical practice and for genes responsible for sporadic cases of diabetes, may be exploited in experiments utilizing human pancreatic islets extracts as a target for SERPA to identify novel candidate T1D autoantigens.
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Affiliation(s)
- Ornella Massa
- Laboratory of Mendelian Diabetes, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
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14
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Receptor type protein tyrosine phosphatases (RPTPs) - roles in signal transduction and human disease. J Cell Commun Signal 2012; 6:125-38. [PMID: 22851429 DOI: 10.1007/s12079-012-0171-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 07/12/2012] [Indexed: 01/06/2023] Open
Abstract
Protein tyrosine phosphorylation is a fundamental regulatory mechanism controlling cell proliferation, differentiation, communication, and adhesion. Disruption of this key regulatory mechanism contributes to a variety of human diseases including cancer, diabetes, and auto-immune diseases. Net protein tyrosine phosphorylation is determined by the dynamic balance of the activity of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Mammals express many distinct PTKs and PTPs. Both of these families can be sub-divided into non-receptor and receptor subtypes. Receptor protein tyrosine kinases (RPTKs) comprise a large family of cell surface proteins that initiate intracellular tyrosine phosphorylation-dependent signal transduction in response to binding of extracellular ligands, such as growth factors and cytokines. Receptor-type protein tyrosine phosphatases (RPTPs) are enzymatic and functional counterparts of RPTKs. RPTPs are a family of integral cell surface proteins that possess intracellular PTP activity, and extracellular domains that have sequence homology to cell adhesion molecules. In comparison to extensively studied RPTKs, much less is known about RPTPs, especially regarding their substrate specificities, regulatory mechanisms, biological functions, and their roles in human diseases. Based on the structure of their extracellular domains, the RPTP family can be grouped into eight sub-families. This article will review one representative member from each RPTP sub-family.
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15
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Abstract
The DENN domain is a common, evolutionarily ancient, and conserved protein module, yet it has gone largely unstudied; until recently, little was known regarding its functional roles. New studies reveal that various DENN domains interact directly with members of the Rab family of small GTPases and that DENN domains function enzymatically as Rab-specific guanine nucleotide exchange factors. Thus, DENN domain proteins appear to be generalized regulators of Rab function. Study of these proteins will provide new insights into Rab-mediated membrane trafficking pathways.
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Affiliation(s)
- Andrea L. Marat
- From the Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Hatem Dokainish
- From the Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Peter S. McPherson
- From the Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
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16
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Abstract
MK-STYX [MAPK (mitogen-activated protein kinase) phospho-serine/threonine/tyrosine-binding protein] is a pseudophosphatase member of the dual-specificity phosphatase subfamily of the PTPs (protein tyrosine phosphatases). MK-STYX is catalytically inactive due to the absence of two amino acids from the signature motif that are essential for phosphatase activity. The nucleophilic cysteine residue and the adjacent histidine residue, which are conserved in all active dual-specificity phosphatases, are replaced by serine and phenylalanine residues respectively in MK-STYX. Mutations to introduce histidine and cysteine residues into the active site of MK-STYX generated an active phosphatase. Using MS, we identified G3BP1 [Ras-GAP (GTPase-activating protein) SH3 (Src homology 3) domain-binding protein-1], a regulator of Ras signalling, as a binding partner of MK-STYX. We observed that G3BP1 bound to native MK-STYX; however, binding to the mutant catalytically active form of MK-STYX was dramatically reduced. G3BP1 is also an RNA-binding protein with endoribonuclease activity that is recruited to 'stress granules' after stress stimuli. Stress granules are large subcellular structures that serve as sites of mRNA sorting, in which untranslated mRNAs accumulate. We have shown that expression of MK-STYX inhibited stress granule formation induced either by aresenite or expression of G3BP itself; however, the catalytically active mutant MK-STYX was impaired in its ability to inhibit G3BP-induced stress granule assembly. These results reveal a novel facet of the function of a member of the PTP family, illustrating a role for MK-STYX in regulating the ability of G3BP1 to integrate changes in growth-factor stimulation and environmental stress with the regulation of protein synthesis.
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17
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Nishimura T, Harashima SI, Yafang H, Notkins AL. IA-2 modulates dopamine secretion in PC12 cells. Mol Cell Endocrinol 2010; 315:81-6. [PMID: 19799965 PMCID: PMC3495171 DOI: 10.1016/j.mce.2009.09.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Revised: 09/16/2009] [Accepted: 09/22/2009] [Indexed: 11/28/2022]
Abstract
The secretion of the hormone insulin from beta cells is modulated by the expression of the dense core vesicle transmembrane protein IA-2. Since IA-2 is found in neuroendocrine cells throughout the body, the present experiments were initiated to determine whether the expression of IA-2 also modulates the secretion of neurotransmitters. Using the dopamine-secreting pheochromocytoma cell line PC12, we found that the overexpressions of IA-2 increased the cellular content and secretion of dopamine, whereas the knockdown of IA-2 by siRNA decreased the cellular content and secretion of dopamine. Neither the overexpression nor knockdown of IA-2 influenced the uptake of [H(3)]dopamine by PC12 cells, but did influence the amount of [H(3)]dopamine secreted. Overexpression of IA-2 also increased the level of the dense core vesicle-associated proteins Rab3A, IA-2beta and secretogranin II, whereas the knockdown of IA-2 decreased the level of these proteins. We conclude that the expression of IA-2 profoundly influences the function of dense core vesicles and has a broad modulating effect on the cellular content and secretion of both hormones and neurotransmitters.
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Affiliation(s)
- Takuya Nishimura
- Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Shin-ichi Harashima
- Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
- Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Hu Yafang
- Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
- Center for Cancer and Immunology Research, Children’s National Medical Center, Washington, DC, USA
| | - Abner Louis Notkins
- Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
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18
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Caromile LA, Oganesian A, Coats SA, Seifert RA, Bowen-Pope DF. The neurosecretory vesicle protein phogrin functions as a phosphatidylinositol phosphatase to regulate insulin secretion. J Biol Chem 2010; 285:10487-96. [PMID: 20097759 DOI: 10.1074/jbc.m109.066563] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phogrin is a transmembrane protein expressed in cells with stimulus-coupled peptide hormone secretion, including pancreatic beta cells, in which it is localized to the membrane of insulin-containing dense-core vesicles. By sequence, phogrin is a member of the family of receptor-like protein-tyrosine phosphatases, but it contains substitutions in conserved catalytic sequences, and no significant enzymatic activity for phogrin has ever been reported. We report here that phogrin is able to dephosphorylate specific inositol phospholipids, including phosphatidylinositol (PI) 3-phosphate and PI 4,5-diphosphate but not PI 3,4,5-trisphosphate. The phosphatidylinositol phosphatase (PIPase) activity of phogrin was measurable but low when evaluated by the ability of a catalytic domain fusion protein to hydrolyze soluble short-chain phosphatidylinositol phospholipids. Unlike most PIPases, which are cytoplasmic proteins that associate with membranes, mature phogrin is a transmembrane protein. When the transmembrane form of phogrin was overexpressed in mammalian cells, it reduced plasma membrane phosphatidylinositol 4,5-disphosphate levels in a dose-dependent manner. When purified and assayed in vitro, the transmembrane form had a specific activity of 142 mol/min/mol, 75-fold more active than the catalytic domain fusion protein and comparable with the specific activities of the other PIPases. The PIPase activity of phogrin depended on the catalytic site cysteine and correlated with effects on glucose-stimulated insulin secretion. We propose that phogrin functions as a phosphatidylinositol phosphatase that contributes to maintaining subcellular differences in levels of PIP that are important for regulating stimulus-coupled exocytosis of insulin.
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Affiliation(s)
- Leslie A Caromile
- Department of Pathology, University ofWashington, Seattle, Washington 98109, USA
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19
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Harashima SI, Harashima C, Nishimura T, Hu Y, Notkins AL. Overexpression of the autoantigen IA-2 puts beta cells into a pre-apoptotic state: autoantigen-induced, but non-autoimmune-mediated, tissue destruction. Clin Exp Immunol 2007; 150:49-60. [PMID: 17725654 PMCID: PMC2219291 DOI: 10.1111/j.1365-2249.2007.03455.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
IA-2 is a major autoantigen in type 1 diabetes and autoantibodies to it have become important diagnostic and predictive markers. IA-2 also is an intrinsic transmembrane component of dense core secretory vesicles and knock-out studies showed that IA-2 is a regulator of insulin secretion. Here we show that overexpression of IA-2 puts mouse insulinoma MIN-6 beta cells into a pre-apoptotic state and that exposure to high glucose results in G2/M arrest and apoptosis. Molecular study revealed a decrease in phosphoinositide-dependent kinase (PDK)-1 and Akt/protein kinase B (PKB) phosphorylation. Treatment of IA-2-transfected cells with IA-2 siRNA prevented both G2/M arrest and apoptosis and increased Akt/PKB phosphorylation. A search for IA-2 interacting proteins revealed that IA-2 interacts with sorting nexin (SNX)19 and that SNX19, but not IA-2, inhibits the conversion of PtdIns(4,5)P2 to PtdIns(3,4,5)P3 and thereby suppresses the phosphorylation of proteins in the Akt signalling pathway resulting in apoptosis. We conclude that IA-2 acts through SNX19 to initiate the pre-apoptotic state. Our findings point to the possibility that in autoimmune diseases, tissue destruction may be autoantigen-induced, but not necessarily immunologically mediated.
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Affiliation(s)
- S-I Harashima
- Experimental Medicine Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892, USA
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