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Andersen JV, Skotte NH, Christensen SK, Polli FS, Shabani M, Markussen KH, Haukedal H, Westi EW, Diaz-delCastillo M, Sun RC, Kohlmeier KA, Schousboe A, Gentry MS, Tanila H, Freude KK, Aldana BI, Mann M, Waagepetersen HS. Hippocampal disruptions of synaptic and astrocyte metabolism are primary events of early amyloid pathology in the 5xFAD mouse model of Alzheimer's disease. Cell Death Dis 2021; 12:954. [PMID: 34657143 PMCID: PMC8520528 DOI: 10.1038/s41419-021-04237-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 09/14/2021] [Accepted: 09/24/2021] [Indexed: 12/23/2022]
Abstract
Alzheimer’s disease (AD) is an unremitting neurodegenerative disorder characterized by cerebral amyloid-β (Aβ) accumulation and gradual decline in cognitive function. Changes in brain energy metabolism arise in the preclinical phase of AD, suggesting an important metabolic component of early AD pathology. Neurons and astrocytes function in close metabolic collaboration, which is essential for the recycling of neurotransmitters in the synapse. However, this crucial metabolic interplay during the early stages of AD development has not been sufficiently investigated. Here, we provide an integrative analysis of cellular metabolism during the early stages of Aβ accumulation in the cerebral cortex and hippocampus of the 5xFAD mouse model of AD. Our electrophysiological examination revealed an increase in spontaneous excitatory signaling in the 5xFAD hippocampus. This hyperactive neuronal phenotype coincided with decreased hippocampal tricarboxylic acid (TCA) cycle metabolism mapped by stable 13C isotope tracing. Particularly, reduced astrocyte TCA cycle activity and decreased glutamine synthesis led to hampered neuronal GABA synthesis in the 5xFAD hippocampus. In contrast, the cerebral cortex of 5xFAD mice displayed an elevated capacity for oxidative glucose metabolism, which may suggest a metabolic compensation in this brain region. We found limited changes when we explored the brain proteome and metabolome of the 5xFAD mice, supporting that the functional metabolic disturbances between neurons and astrocytes are early primary events in AD pathology. In addition, synaptic mitochondrial and glycolytic function was selectively impaired in the 5xFAD hippocampus, whereas non-synaptic mitochondrial function was maintained. These findings were supported by ultrastructural analyses demonstrating disruptions in mitochondrial morphology, particularly in the 5xFAD hippocampus. Collectively, our study reveals complex regional and cell-specific metabolic adaptations in the early stages of amyloid pathology, which may be fundamental for the progressing synaptic dysfunctions in AD.
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Affiliation(s)
- Jens V Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Niels H Skotte
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sofie K Christensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Filip S Polli
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA, USA
| | - Mohammad Shabani
- Neuroscience Research Center, Neuropharmacology Institute, Kerman University of Medical Sciences, Kerman, Iran
| | - Kia H Markussen
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, KY, USA
| | - Henriette Haukedal
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Emil W Westi
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Marta Diaz-delCastillo
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ramon C Sun
- Markey Cancer Center, Lexington, KY, USA.,Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, KY, USA
| | - Kristi A Kohlmeier
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Matthew S Gentry
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, KY, USA.,Markey Cancer Center, Lexington, KY, USA
| | - Heikki Tanila
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Kristine K Freude
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Blanca I Aldana
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Matthias Mann
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Helle S Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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Jakobsen E, Andersen JV, Christensen SK, Siamka O, Larsen MR, Waagepetersen HS, Aldana BI, Bak LK. Pharmacological inhibition of mitochondrial soluble adenylyl cyclase in astrocytes causes activation of AMP-activated protein kinase and induces breakdown of glycogen. Glia 2021; 69:2828-2844. [PMID: 34378239 DOI: 10.1002/glia.24072] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 06/28/2021] [Accepted: 07/30/2021] [Indexed: 12/17/2022]
Abstract
Mobilization of astrocyte glycogen is key for processes such as synaptic plasticity and memory formation but the link between neuronal activity and glycogen breakdown is not fully known. Activation of cytosolic soluble adenylyl cyclase (sAC) in astrocytes has been suggested to link neuronal depolarization and glycogen breakdown partly based on experiments employing pharmacological inhibition of sAC. However, several studies have revealed that sAC located within mitochondria is a central regulator of respiration and oxidative phosphorylation. Thus, pharmacological sAC inhibition is likely to affect both cytosolic and mitochondrial sAC and if bioenergetic readouts are studied, the observed effects are likely to stem from inhibition of mitochondrial rather than cytosolic sAC. Here, we report that a pharmacologically induced inhibition of sAC activity lowers mitochondrial respiration, induces phosphorylation of the metabolic master switch AMP-activated protein kinase (AMPK), and decreases glycogen stores in cultured primary murine astrocytes. From these data and our discussion of the literature, mitochondrial sAC emerges as a key regulator of astrocyte bioenergetics. Lastly, we discuss the challenges of investigating the functional and metabolic roles of cytosolic versus mitochondrial sAC in astrocytes employing the currently available pharmacological tool compounds.
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Affiliation(s)
- Emil Jakobsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jens V Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sofie K Christensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Olga Siamka
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Martin R Larsen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Denmark
| | - Helle S Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Blanca I Aldana
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lasse K Bak
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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3
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Andersen JV, Christensen SK, Westi EW, Diaz-delCastillo M, Tanila H, Schousboe A, Aldana BI, Waagepetersen HS. Deficient astrocyte metabolism impairs glutamine synthesis and neurotransmitter homeostasis in a mouse model of Alzheimer's disease. Neurobiol Dis 2020; 148:105198. [PMID: 33242587 DOI: 10.1016/j.nbd.2020.105198] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 11/16/2020] [Accepted: 11/20/2020] [Indexed: 12/11/2022] Open
Abstract
Alzheimer's disease (AD) leads to cerebral accumulation of insoluble amyloid-β plaques causing synaptic dysfunction and neuronal death. Neurons rely on astrocyte-derived glutamine for replenishment of the amino acid neurotransmitter pools. Perturbations of astrocyte glutamine synthesis have been described in AD, but whether this functionally affects neuronal neurotransmitter synthesis is not known. Since the synthesis and recycling of neurotransmitter glutamate and GABA are intimately coupled to cellular metabolism, the aim of this study was to provide a functional investigation of neuronal and astrocytic energy and neurotransmitter metabolism in AD. To achieve this, we incubated acutely isolated cerebral cortical and hippocampal slices from 8-month-old female 5xFAD mice, in the presence of 13C isotopically enriched substrates, with subsequent gas chromatography-mass spectrometry (GC-MS) analysis. A prominent neuronal hypometabolism of [U-13C]glucose was observed in the hippocampal slices of the 5xFAD mice. Investigating astrocyte metabolism, using [1,2-13C]acetate, revealed a marked reduction in glutamine synthesis, which directly hampered neuronal synthesis of GABA. This was supported by an increased metabolism of exogenously supplied [U-13C]glutamine, suggesting a neuronal metabolic compensation of the reduced astrocytic glutamine supply. In contrast, astrocytic metabolism of [U-13C]GABA was reduced, whereas [U-13C]glutamate metabolism was unaffected. Finally, astrocyte de novo synthesis of glutamate and glutamine was hampered, whereas the enzymatic capacity of glutamine synthetase for ammonia fixation was maintained. Collectively, we demonstrate that deficient astrocyte metabolism leads to reduced glutamine synthesis, directly impairing neuronal GABA synthesis in the 5xFAD brain. These findings suggest that astrocyte metabolic dysfunction may be fundamental for the imbalances of synaptic excitation and inhibition in the AD brain.
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Affiliation(s)
- Jens V Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
| | - Sofie K Christensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Emil W Westi
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Marta Diaz-delCastillo
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Heikki Tanila
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Blanca I Aldana
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Helle S Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
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Hohnholt MC, Andersen VH, Andersen JV, Christensen SK, Karaca M, Maechler P, Waagepetersen HS. Glutamate dehydrogenase is essential to sustain neuronal oxidative energy metabolism during stimulation. J Cereb Blood Flow Metab 2018; 38. [PMID: 28621566 PMCID: PMC6168903 DOI: 10.1177/0271678x17714680] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The enzyme glutamate dehydrogenase (GDH; Glud1) catalyzes the (reversible) oxidative deamination of glutamate to α-ketoglutarate accompanied by a reduction of NAD+ to NADH. GDH connects amino acid, carbohydrate, neurotransmitter and oxidative energy metabolism. Glutamine is a neurotransmitter precursor used by neurons to sustain the pool of glutamate, but glutamine is also vividly oxidized for support of energy metabolism. This study investigates the role of GDH in neuronal metabolism by employing the Cns- Glud1-/- mouse, lacking GDH in the brain (GDH KO) and metabolic mapping using 13C-labelled glutamine and glucose. We observed a severely reduced oxidative glutamine metabolism during glucose deprivation in synaptosomes and cultured neurons not expressing GDH. In contrast, in the presence of glucose, glutamine metabolism was not affected by the lack of GDH expression. Respiration fuelled by glutamate was significantly lower in brain mitochondria from GDH KO mice and synaptosomes were not able to increase their respiration upon an elevated energy demand. The role of GDH for metabolism of glutamine and the respiratory capacity underscore the importance of GDH for neurons particularly during an elevated energy demand, and it may reflect the large allosteric activation of GDH by ADP.
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Affiliation(s)
- Michaela C Hohnholt
- 1 Department of Drug Design and Pharmacology, Faculty of Health and Medical Science, University of Copenhagen, Copenhagen, Denmark
| | - Vibe H Andersen
- 1 Department of Drug Design and Pharmacology, Faculty of Health and Medical Science, University of Copenhagen, Copenhagen, Denmark
| | - Jens V Andersen
- 1 Department of Drug Design and Pharmacology, Faculty of Health and Medical Science, University of Copenhagen, Copenhagen, Denmark
| | - Sofie K Christensen
- 1 Department of Drug Design and Pharmacology, Faculty of Health and Medical Science, University of Copenhagen, Copenhagen, Denmark
| | - Melis Karaca
- 2 Department of Cell Physiology and Metabolism, CMU, University of Geneva, Geneva, Switzerland
| | - Pierre Maechler
- 2 Department of Cell Physiology and Metabolism, CMU, University of Geneva, Geneva, Switzerland
| | - Helle S Waagepetersen
- 1 Department of Drug Design and Pharmacology, Faculty of Health and Medical Science, University of Copenhagen, Copenhagen, Denmark
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5
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Kousted TM, Kalliokoski O, Christensen SK, Winther JR, Hau J. Exploring the antigenic response to multiplexed immunizations in a chicken model of antibody production. Heliyon 2017; 3:e00267. [PMID: 28367512 PMCID: PMC5362046 DOI: 10.1016/j.heliyon.2017.e00267] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Revised: 02/22/2017] [Accepted: 03/09/2017] [Indexed: 11/28/2022] Open
Abstract
Hens have a tremendous capacity for producing polyclonal antibodies that can subsequently be isolated in high concentrations from their eggs. An approach for further maximizing their potential is to produce multiple antisera in the same individual through multiplexed (multiple simultaneous) immunizations. An unknown with this approach is how many immunogens a single bird is capable of mounting a sizeable antigenic response toward. At what point does it become counter-productive to add more immunogens to the same immunization regimen? In the present study we were able to demonstrate that the competing effects of co-administering multiple immunogens effectively limit the antibody specificities that can be raised in a single individual to a fairly low number. Two potent model immunogens, KLH and CRM197, were administered together with competing antigens in various concentrations and complexities. With an upper limit of 1 mg protein material recommended for chicken immunizations, we found that the maximum number of immunogens that can be reliably used is most likely in the low double digits. The limiting factor for a response to an immunogen could not be related to the number of splenic plasma cells producing antibodies against it. When administering KLH alone, up to 70% of the IgY-producing splenic plasma cells were occupied with producing anti-KLH antibodies; but when simultaneously being exposed to a plethora of other antigens, a response of a comparable magnitude could be mounted with a splenic plasma cell involvement of less than 5%. Two breeds of egg-layers were compared with respect to antibody production in an initial experiment, but differences in antibody productivity were negligible. Although our findings support the use of multiplexed immunizations in the hen, we find that the number of immunogens cannot be stretched much higher than the handful that has been used in mammalian models to date.
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Affiliation(s)
- Tina M. Kousted
- Department of Experimental Medicine, University of Copenhagen, Denmark
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Denmark
| | - Otto Kalliokoski
- Department of Experimental Medicine, University of Copenhagen, Denmark
- Corresponding author at: Blegdamsvej 3B, 2200 Copenhagen N, Denmark.
| | | | - Jakob R. Winther
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Denmark
| | - Jann Hau
- Department of Experimental Medicine, University of Copenhagen, Denmark
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6
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Abstract
It is becoming evident that type 2 diabetes mellitus is affecting brain energy metabolism. The importance of alternative substrates for the brain in type 2 diabetes mellitus is poorly understood. The aim of this study was to investigate whether ketone bodies are relevant candidates to compensate for cerebral glucose hypometabolism and unravel the functionality of cerebral mitochondria in type 2 diabetes mellitus. Acutely isolated cerebral cortical and hippocampal slices of db/db mice were incubated in media containing [U-13C]glucose, [1,2-13C]acetate or [U-13C]β-hydroxybutyrate and tissue extracts were analysed by mass spectrometry. Oxygen consumption and ATP synthesis of brain mitochondria of db/db mice were assessed by Seahorse XFe96 and luciferin-luciferase assay, respectively. Glucose hypometabolism was observed for both cerebral cortical and hippocampal slices of db/db mice. Significant increased metabolism of [1,2-13C]acetate and [U-13C]β-hydroxybutyrate was observed for hippocampal slices of db/db mice. Furthermore, brain mitochondria of db/db mice exhibited elevated oxygen consumption and ATP synthesis rate. This study provides evidence of several changes in brain energy metabolism in type 2 diabetes mellitus. The increased hippocampal ketone body utilization and improved mitochondrial function in db/db mice, may act as adaptive mechanisms in order to maintain cerebral energetics during hampered glucose metabolism.
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Affiliation(s)
- Jens V Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sofie K Christensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jakob D Nissen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Helle S Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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7
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Andersen JV, Christensen SK, Aldana BI, Nissen JD, Tanila H, Waagepetersen HS. Alterations in Cerebral Cortical Glucose and Glutamine Metabolism Precedes Amyloid Plaques in the APPswe/PSEN1dE9 Mouse Model of Alzheimer's Disease. Neurochem Res 2016; 42:1589-1598. [PMID: 27686658 DOI: 10.1007/s11064-016-2070-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 09/21/2016] [Accepted: 09/22/2016] [Indexed: 12/30/2022]
Abstract
Alterations in brain energy metabolism have been suggested to be of fundamental importance for the development of Alzheimer's disease (AD). However, specific changes in brain energetics in the early stages of AD are poorly known. The aim of this study was to investigate cerebral energy metabolism in the APPswe/PSEN1dE9 mouse prior to amyloid plaque formation. Acutely isolated cerebral cortical and hippocampal slices of 3-month-old APPswe/PSEN1dE9 and wild-type control mice were incubated in media containing [U-13C]glucose, [1,2-13C]acetate or [U-13C]glutamine, and tissue extracts were analyzed by mass spectrometry. The ATP synthesis rate of isolated whole-brain mitochondria was assessed by an on-line luciferin-luciferase assay. Significantly increased 13C labeling of intracellular lactate and alanine and decreased tricarboxylic acid (TCA) cycle activity were observed from cerebral cortical slices of APPswe/PSEN1dE9 mice incubated in media containing [U-13C]glucose. No changes in glial [1,2-13C]acetate metabolism were observed. Cerebral cortical slices from APPswe/PSEN1dE9 mice exhibited a reduced capacity for uptake and oxidative metabolism of glutamine. Furthermore, the ATP synthesis rate tended to be decreased in isolated whole-brain mitochondria of APPswe/PSEN1dE9 mice. Thus, several cerebral metabolic changes are evident in the APPswe/PSEN1dE9 mouse prior to amyloid plaque deposition, including altered glucose metabolism, hampered glutamine processing and mitochondrial dysfunctions.
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Affiliation(s)
- Jens V Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sofie K Christensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Blanca I Aldana
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jakob D Nissen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Heikki Tanila
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Helle S Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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8
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Mehmedbasic A, Christensen SK, Nilsson J, Rüetschi U, Gustafsen C, Poulsen ASA, Rasmussen RW, Fjorback AN, Larson G, Andersen OM. SorLA complement-type repeat domains protect the amyloid precursor protein against processing. J Biol Chem 2014; 290:3359-76. [PMID: 25525276 DOI: 10.1074/jbc.m114.619940] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SorLA is a neuronal sorting receptor that is genetically associated with Alzheimer disease. SorLA interacts directly with the amyloid precursor protein (APP) and affects the processing of the precursor, leading to a decreased generation of the amyloid-β peptide. The SorLA complement-type repeat (CR) domains associate in vitro with APP, but the precise molecular determinants of SorLA·APP complex formation and the mechanisms responsible for the effect of binding on APP processing have not yet been elucidated. Here, we have generated protein expression constructs for SorLA devoid of the 11 CR-domains and for two SorLA mutants harboring substitutions of the fingerprint residues in the central CR-domains. We generated SH-SY5Y cell lines that stably express these SorLA variants to study the binding and processing of APP using co-immunoprecipitation and Western blotting/ELISAs, respectively. We found that the SorLA CR-cluster is essential for interaction with APP and that deletion of the CR-cluster abolishes the protection against APP processing. Mutation of identified fingerprint residues in the SorLA CR-domains leads to changes in the O-linked glycosylation of APP when expressed in SH-SY5Y cells. Our results provide novel information on the mechanisms behind the influence of SorLA activity on APP metabolism by controlling post-translational glycosylation in the Golgi, suggesting new strategies against amyloidogenesis in Alzheimer disease.
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Affiliation(s)
- Arnela Mehmedbasic
- From the Lundbeck Foundation Research Center MIND, Danish Research Institute of Translational Neuroscience Nordic-EMBL Partnership (DANDRITE), Department of Biomedicine, Aarhus University, Ole Worms Allé 3, DK-8000 AarhusC, Denmark and
| | - Sofie K Christensen
- From the Lundbeck Foundation Research Center MIND, Danish Research Institute of Translational Neuroscience Nordic-EMBL Partnership (DANDRITE), Department of Biomedicine, Aarhus University, Ole Worms Allé 3, DK-8000 AarhusC, Denmark and
| | - Jonas Nilsson
- the Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, University of Gothenburg, SE-413 45 Gothenburg, Sweden
| | - Ulla Rüetschi
- the Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, University of Gothenburg, SE-413 45 Gothenburg, Sweden
| | - Camilla Gustafsen
- From the Lundbeck Foundation Research Center MIND, Danish Research Institute of Translational Neuroscience Nordic-EMBL Partnership (DANDRITE), Department of Biomedicine, Aarhus University, Ole Worms Allé 3, DK-8000 AarhusC, Denmark and
| | - Annemarie Svane Aavild Poulsen
- From the Lundbeck Foundation Research Center MIND, Danish Research Institute of Translational Neuroscience Nordic-EMBL Partnership (DANDRITE), Department of Biomedicine, Aarhus University, Ole Worms Allé 3, DK-8000 AarhusC, Denmark and
| | - Rikke W Rasmussen
- From the Lundbeck Foundation Research Center MIND, Danish Research Institute of Translational Neuroscience Nordic-EMBL Partnership (DANDRITE), Department of Biomedicine, Aarhus University, Ole Worms Allé 3, DK-8000 AarhusC, Denmark and
| | - Anja N Fjorback
- From the Lundbeck Foundation Research Center MIND, Danish Research Institute of Translational Neuroscience Nordic-EMBL Partnership (DANDRITE), Department of Biomedicine, Aarhus University, Ole Worms Allé 3, DK-8000 AarhusC, Denmark and
| | - Göran Larson
- the Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, University of Gothenburg, SE-413 45 Gothenburg, Sweden
| | - Olav M Andersen
- From the Lundbeck Foundation Research Center MIND, Danish Research Institute of Translational Neuroscience Nordic-EMBL Partnership (DANDRITE), Department of Biomedicine, Aarhus University, Ole Worms Allé 3, DK-8000 AarhusC, Denmark and
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9
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Mehmedbasic A, Christensen SK, Gustafsen C, Rasmussen RW, Fjorback AW, Andersen OM. O2‐04‐05: THE INFLUENCE OF SORLA CR‐DOMAINS ON BINDING TO AND PROCESSING OF APP. Alzheimers Dement 2014. [DOI: 10.1016/j.jalz.2014.04.177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
| | | | - Camilla Gustafsen
- MIND Centre, Department of BiomedicineAarhus UniversityAarhusDenmark
| | | | - Anja W. Fjorback
- MIND Centre, Department of BiomedicineAarhus UniversityAarhusDenmark
| | - Olav M. Andersen
- MIND Centre, Department of BiomedicineAarhus UniversityAarhusDenmark
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10
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Abstract
The stringent response is defined as the physiological changes elicited by amino acid starvation. Many of these changes depend on the regulatory nucleotide ppGpp (guanosine tetraphosphate) synthesized by RelA (ppGpp synthetase I), the relA-encoded protein. The second rel locus of Escherichia coli is called relBE and encodes RelE cytotoxin and RelB antitoxin. RelB counteracts the toxic effect of RelE. In addition, RelB is an autorepressor of relBE transcription. Here we reveal a ppGpp-independent mechanism that reduces the level of translation during amino acid starvation. Artificial overexpression of RelE severely inhibited translation. During amino acid starvation, the presence of relBE caused a significant reduction in the poststarvation level of translation. Concomitantly, relBE transcription was rapidly and strongly induced. Induction of transcription occurred independently of relA and spoT (encoding ppGpp synthetase II), but instead depended on Lon protease. Consistently, Lon was required for degradation of RelB. Replacement of the relBE promoter with a LacI-regulated promoter indicated that strong and ongoing transcription of relBE is required to maintain a proper RelB:RelE ratio during starvation. Thus relBE may be regarded as a previously uncharacterized type of stress-response element that reduces the global level of translation during nutritional stress.
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Affiliation(s)
- S K Christensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, OU, Campusvej 55, DK-5230 Odense M, Denmark
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11
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Abstract
Although auxin is known to regulate many processes in plant development and has been studied for over a century, the mechanisms whereby plants produce it have remained elusive. Here we report the characterization of a dominant Arabidopsis mutant, yucca, which contains elevated levels of free auxin. YUCCA encodes a flavin monooxygenase-like enzyme and belongs to a family that includes at least nine other homologous Arabidopsis genes, a subset of which appears to have redundant functions. Results from tryptophan analog feeding experiments and biochemical assays indicate that YUCCA catalyzes hydroxylation of the amino group of tryptamine, a rate-limiting step in tryptophan-dependent auxin biosynthesis.
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Affiliation(s)
- Y Zhao
- Howard Hughes Medical Institute, Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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12
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Weigel D, Ahn JH, Blázquez MA, Borevitz JO, Christensen SK, Fankhauser C, Ferrándiz C, Kardailsky I, Malancharuvil EJ, Neff MM, Nguyen JT, Sato S, Wang ZY, Xia Y, Dixon RA, Harrison MJ, Lamb CJ, Yanofsky MF, Chory J. Activation tagging in Arabidopsis. Plant Physiol 2000; 122:1003-13. [PMID: 10759496 PMCID: PMC1539247 DOI: 10.1104/pp.122.4.1003] [Citation(s) in RCA: 656] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Activation tagging using T-DNA vectors that contain multimerized transcriptional enhancers from the cauliflower mosaic virus (CaMV) 35S gene has been applied to Arabidopsis plants. New activation-tagging vectors that confer resistance to the antibiotic kanamycin or the herbicide glufosinate have been used to generate several tens of thousands of transformed plants. From these, over 30 dominant mutants with various phenotypes have been isolated. Analysis of a subset of mutants has shown that overexpressed genes are almost always found immediately adjacent to the inserted CaMV 35S enhancers, at distances ranging from 380 bp to 3.6 kb. In at least one case, the CaMV 35S enhancers led primarily to an enhancement of the endogenous expression pattern rather than to constitutive ectopic expression, suggesting that the CaMV 35S enhancers used here act differently than the complete CaMV 35S promoter. This has important implications for the spectrum of genes that will be discovered by this method.
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Affiliation(s)
- D Weigel
- Plant Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, USA.
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Abstract
Arabidopsis plants carrying mutations in the PINOID (PID) gene have a pleiotropic shoot phenotype that mimics that of plants grown on auxin transport inhibitors or of plants mutant for the auxin efflux carrier PINFORMED (PIN), with defects in the formation of cotyledons, flowers, and floral organs. We have cloned PID and find that it is transiently expressed in the embryo and in initiating floral anlagen, demonstrating a specific role for PID in promoting primordium development. Constitutive expression of PID causes a phenotype in both shoots and roots that is similar to that of auxin-insensitive plants, implying that PID, which encodes a serine-threonine protein kinase, negatively regulates auxin signaling.
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Affiliation(s)
- S K Christensen
- The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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14
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Abstract
FLOWERING LOCUS T (FT), which acts in parallel with the meristem-identity gene LEAFY (LFY) to induce flowering of Arabidopsis, was isolated by activation tagging. Like LFY, FT acts partially downstream of CONSTANS (CO), which promotes flowering in response to long days. Unlike many other floral regulators, the deduced sequence of the FT protein does not suggest that it directly controls transcription or transcript processing. Instead, it is similar to the sequence of TERMINAL FLOWER 1 (TFL1), an inhibitor of flowering that also shares sequence similarity with membrane-associated mammalian proteins.
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Affiliation(s)
- I Kardailsky
- Plant Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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Kardailsky I, Shukla VK, Ahn JH, Dagenais N, Christensen SK, Nguyen JT, Chory J, Harrison MJ, Weigel D. Activation tagging of the floral inducer FT. Science 1999. [PMID: 10583961 DOI: 10.1126/science.286.54461962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
FLOWERING LOCUS T (FT), which acts in parallel with the meristem-identity gene LEAFY (LFY) to induce flowering of Arabidopsis, was isolated by activation tagging. Like LFY, FT acts partially downstream of CONSTANS (CO), which promotes flowering in response to long days. Unlike many other floral regulators, the deduced sequence of the FT protein does not suggest that it directly controls transcription or transcript processing. Instead, it is similar to the sequence of TERMINAL FLOWER 1 (TFL1), an inhibitor of flowering that also shares sequence similarity with membrane-associated mammalian proteins.
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Affiliation(s)
- I Kardailsky
- Plant Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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Jensen KA, Christensen SK, Nielsen EM, Bünemann LK, Therkelsen K, Knudsen F. [Cerebral blood flow and indomethacin. The effect of different doses administered as continuous intravenous infusions or as suppositories in healthy adults]. Ugeskr Laeger 1997; 159:4257-60. [PMID: 9229881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Administration of indomethacin may aid treatment of intracranial hypertension, and the present study was conducted to determine the optimal dose. In healthy volunteers, cerebral blood flow (CBF) has been shown to decrease considerably after a bolus dose of indomethacin, 0.4 mg/kg, followed by continuous infusion, 0.4 mg/kg/h. This decrease was sustained for 6 h without any evidence of adaptation. In a randomized study in healthy volunteers, indomethacin, 0.1, 0.2 and 0.3 mg/kg, was given as bolus, followed by continuous infusion of 0.1, 0.2 and 0.3 mg/kg/h. CBF decreased from normal levels (52-74 ml/100 mg/min) to 38-51 ml/100 g/min. There were no differences among the three groups in CBF reduction, and the reduction was sustained during the 6-h infusion period. Rectal application of 100 mg indomethacin was found to reduce CBF from normal levels (54-74 ml/100 mg/min) to 33-48 ml/100 mg/min. These low levels were only sustained for 2 h, and values returned to normal over the next 6 h. We observed no rebound phenomenon 2 h after stopping the infusion and no rebound after 100 mg of rectally applied indomethacin. Since a dose as low as 0.1 mg/kg/h is effective, it is possible to treat most patient in a 24-h schedule without going over maximum recommended doses.
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Gregersen N, Wintzensen H, Christensen SK, Christensen MF, Brandt NJ, Rasmussen K. C6-C10-dicarboxylic aciduria: investigations of a patient with riboflavin responsive multiple acyl-CoA dehydrogenation defects. Pediatr Res 1982; 16:861-8. [PMID: 7145508 DOI: 10.1203/00006450-198210000-00012] [Citation(s) in RCA: 97] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The abnormal metabolites-adipic, suberic, and sebacic acids-were detected in large amounts in the urine of a boy during a Reye's syndrome-like crisis. Substantial amounts of 5-OH-caproic acid, caproylglycine, glutaric acid, and 3-OH-butyric acid and moderately elevated amounts of ethylmalonic acid, methylsuccinic acid, 3-OH-isovaleric acid, and isovalerylglycine were also found. These metabolites were consistently present in urine samples collected in the boy's habitual condition after the attack. 1-[14C]-Palmitic acid was oxidized at a normal rate, whereas U-[14C]-Palmitic acid was oxidized at a reduced rate in cultured skin fibroblasts from the patient, thus indicating a defect at the level of medium- and/or short-chain fatty acid oxidation. Riboflavin medication (100 mg three times a day) significantly reduced the excreted amounts of pathologic metabolites, suggesting a flavineadeninedinucleotide-related acyl-CoA dehydrogenation defect as the cause of the disease. Carnitine in plasma was low in the patient (6 mumole/liter, controls 26-74 mumole/liter), suggesting carnitine deficiency as a secondary effect of the acyl-CoA dehydrogenation deficiency. The present patient, who presented with a Reye's syndrome-like attack, suffers from impaired dehydrogenation of acyl-CoA resulting in accumulation of acyl-CoA in the cells. Attacks with similar symptoms are seen in other acyl-CoA dehydrogenation deficiencies, such as glutaric aciduria types I and II, other types of C6-C10-dicarboxylic acidurias and isovaleric acidemia. Reduced flow through the acyl-CoA dehydrogenation steps may therefore be an ethiologic factor in Reye's syndrome. Several of the accumulated acyl-CoA's are toxic and may be responsible for some of the symptoms. The low carnitine level in plasma and the elevated esterified carnitine excretion in the present patient indicate that acyl-CoA accumulation may cause a functional carnitine deficiency by sequestration of carnitine as acyl-carnitines. As the inborn defect, systemic carnitine deficiency may exhibit symptoms like those of Reye's syndrome, it may be speculated whether functional carnitine deficiency in patients with accumulated acyl-CoA is another causal factor in the development of the symptoms during attacks.
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