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Reich N, Hölscher C. Cholecystokinin (CCK): a neuromodulator with therapeutic potential in Alzheimer's and Parkinson's disease. Front Neuroendocrinol 2024; 73:101122. [PMID: 38346453 DOI: 10.1016/j.yfrne.2024.101122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 01/04/2024] [Accepted: 01/25/2024] [Indexed: 02/16/2024]
Abstract
Cholecystokinin (CCK) is a neuropeptide modulating digestion, glucose levels, neurotransmitters and memory. Recent studies suggest that CCK exhibits neuroprotective effects in Alzheimer's disease (AD) and Parkinson's disease (PD). Thus, we review the physiological function and therapeutic potential of CCK. The neuropeptide facilitates hippocampal glutamate release and gates GABAergic basket cell activity, which improves declarative memory acquisition, but inhibits consolidation. Cortical CCK alters recognition memory and enhances audio-visual processing. By stimulating CCK-1 receptors (CCK-1Rs), sulphated CCK-8 elicits dopamine release in the substantia nigra and striatum. In the mesolimbic pathway, CCK release is triggered by dopamine and terminates reward responses via CCK-2Rs. Importantly, activation of hippocampal and nigral CCK-2Rs is neuroprotective by evoking AMPK activation, expression of mitochondrial fusion modulators and autophagy. Other benefits include vagus nerve/CCK-1R-mediated expression of brain-derived neurotrophic factor, intestinal protection and suppression of inflammation. We also discuss caveats and the therapeutic combination of CCK with other peptide hormones.
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Affiliation(s)
- Niklas Reich
- The ALBORADA Drug Discovery Institute, University of Cambridge, Island Research Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0AH, UK; Faculty of Health and Medicine, Biomedical & Life Sciences Division, Lancaster University, Lancaster LA1 4YQ, UK.
| | - Christian Hölscher
- Second associated Hospital, Neurology Department, Shanxi Medical University, Taiyuan, Shanxi, China; Henan Academy of Innovations in Medical Science, Neurodegeneration research group, Xinzhen, Henan province, China
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2
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Uehara M, Fukumoto A, Omote H, Hiasa M. Polyamine release and vesicular polyamine transporter expression in megakaryoblastic cells and platelets. Biochim Biophys Acta Gen Subj 2024:130610. [PMID: 38527572 DOI: 10.1016/j.bbagen.2024.130610] [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: 01/21/2024] [Revised: 03/08/2024] [Accepted: 03/20/2024] [Indexed: 03/27/2024]
Abstract
Polyamines not only play essential roles in cell growth and function of living organisms but are also released into the extracellular space and function as regulators of chemical transduction, although the cells from which they are released and their mode of release are not well understood. The vesicular polyamine transporter (VPAT), encoded by the SLC18B1 is responsible for the vesicular storage of spermine and spermidine, followed by their vesicular release from secretory cells. Focusing on VPAT will help identify polyamine-secreting cells and new polyamine functions. In this study, we investigated the possible involvement of VPAT in vesicular release of polyamines in MEG-01 clonal megakaryoblastic cells and platelets. RT-PCR, western blotting, and immunohistochemistry revealed VPAT expression in MEG-01 cells. MEG-01 cells secreted polyamines upon A23187 stimulation in the presence of Ca2+, which is temperature-dependent and sensitive to bafilomycin A1. A23187-induced polyamine secretion from MEG-01 cells was reduced by treatment with reserpine, VPAT inhibitors, or VPAT RNA interference. Platelets also expressed VPAT, displaying a punctate distribution, and released spermidine upon A23187 and thrombin stimulation. These findings have demonstrated VPAT-mediated vesicular polyamine release from MEG-01 cells, suggesting the presence of similar vesicular polyamine release mechanisms in platelets.
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Affiliation(s)
- Mizuki Uehara
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1-1-1, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
| | - Ayaka Fukumoto
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1-1-1, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
| | - Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1-1-1, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.
| | - Miki Hiasa
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1-1-1, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.
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3
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Li S, Yuan H, Yang K, Li Q, Xiang M. Pancreatic sympathetic innervation disturbance in type 1 diabetes. Clin Immunol 2023; 250:109319. [PMID: 37024024 DOI: 10.1016/j.clim.2023.109319] [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: 01/04/2023] [Revised: 02/15/2023] [Accepted: 03/06/2023] [Indexed: 04/08/2023]
Abstract
Pancreatic sympathetic innervation can directly affect the function of islet. The disorder of sympathetic innervation in islets during the occurrence of type 1 diabetes (T1D) has been reported to be controversial with the inducing factor unclarified. Several studies have uncovered the critical role that sympathetic signals play in controlling the local immune system. The survival and operation of endocrine cells can be regulated by immune cell infiltration in islets. In the current review, we focused on the impact of sympathetic signals working on islets cell regulation, and discussed the potential factors that can induce the sympathetic innervation disorder in the islets. We also summarized the effect of interference with the islet sympathetic signals on the T1D occurrence. Overall, complete understanding of the regulatory effect of sympathetic signals on islet cells and local immune system could facilitate to design better strategies to control inflammation and protect β cells in T1D therapy.
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Affiliation(s)
- Senlin Li
- Department of Pharmacology, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Huimin Yuan
- Department of Pharmacology, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Keshan Yang
- Department of Pharmacology, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Qing Li
- Department of Pharmacology, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Ming Xiang
- Department of Pharmacology, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
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Lopez Quiñones AJ, Vieira LS, Wang J. Clinical Applications and the Roles of Transporters in Disposition, Tumor Targeting, and Tissue Toxicity of meta-Iodobenzylguanidine (mIBG). Drug Metab Dispos 2022; 50:DMD-MR-2021-000707. [PMID: 35197314 PMCID: PMC9488973 DOI: 10.1124/dmd.121.000707] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 02/01/2022] [Accepted: 02/17/2022] [Indexed: 11/22/2022] Open
Abstract
Transporters on the plasma membrane of tumor cells are promising molecular "Trojan horses" to deliver drugs and imaging agents into cancer cells. Radioiodine-labeled meta-iodobenzylguanidine (mIBG) is used as a diagnostic agent (123I-mIBG) and a targeted radiotherapy (131I-mIBG) for neuroendocrine cancers. mIBG enters cancer cells through the norepinephrine transporter (NET) where the radioactive decay of 131I causes DNA damage, cell death, and tumor necrosis. mIBG is predominantly eliminated unchanged by the kidney. Despite its selective uptake by neuroendocrine tumors, mIBG accumulates in several normal tissues and leads to tissue-specific radiation toxicities. Emerging evidences suggest that the polyspecific organic cation transporters play important roles in systemic disposition and tissue-specific uptake of mIBG. In particular, human organic cation transporter 2 (hOCT2) and toxin extrusion proteins 1 and 2-K (hMATE1/2-K) likely mediate renal secretion of mIBG whereas hOCT1 and hOCT3 may contribute to mIBG uptake into normal tissues such as the liver, salivary glands, and heart. This mini-review focuses on the clinical applications of mIBG in neuroendocrine cancers and the differential roles of NET, OCT and MATE transporters in mIBG disposition, response and toxicity. Understanding the molecular mechanisms governing mIBG transport in cancer and normal cells is a critical step for developing strategies to optimize the efficacy of 131I-mIBG while minimizing toxicity in normal tissues. Significance Statement Radiolabeled mIBG has been used as a diagnostic tool and as radiotherapy for neuroendocrine cancers and other diseases. NET, OCT and MATE transporters play differential roles in mIBG tumor targeting, systemic elimination, and accumulation in normal tissues. The clinical use of mIBG as a radiopharmaceutical in cancer diagnosis and treatment can be further improved by taking a holistic approach considering mIBG transporters in both cancer and normal tissues.
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Affiliation(s)
| | | | - Joanne Wang
- Dept. of Pharmaceutics, University of Washington, United States
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Haase J, Jones AKC, Mc Veigh CJ, Brown E, Clarke G, Ahnert-Hilger G. Sex and brain region-specific regulation of serotonin transporter activity in synaptosomes in guanine nucleotide-binding protein G(q) alpha knockout mice. J Neurochem 2021; 159:156-171. [PMID: 34309872 DOI: 10.1111/jnc.15482] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 07/15/2021] [Accepted: 07/21/2021] [Indexed: 10/20/2022]
Abstract
The regulation of the serotonin transporter (SERT) by guanine nucleotide-binding protein alpha (Gα) q was investigated using Gαq knockout mice. In the absence of Gαq, SERT-mediated uptake of 5-hydroxytryptamine (5HT) was enhanced in midbrain and frontal cortex synaptosomes, but only in female mice. The mechanisms underlying this sexual dimorphism were investigated using quantitative western blot analysis revealing brain region-specific differences. In the frontal cortex, SERT protein expression was decreased in male knockout mice, seemingly explaining the sex-dependent variation in SERT activity. The differential expression of Gαi1 in female mice contributes to the sex differences in the midbrain. In fact, Gαi1 levels inversely correlate with 5HT uptake rates across both sexes and genotypes. Likely due to differential SERT regulation as well as sex differences in the expression of tryptophan hydroxylase 2, Gαq knockout mice also displayed sex- and genotype-dependent alterations in total 5HT tissue levels as determined by high-performance liquid chromatography. Gαq inhibitors, YM-254890 and BIM-46187, differentially affected SERT activity in both, synaptosomes and cultured cells. YM-254890 treatment mimicked the effect of Gαq knockout in the frontal cortex. BIM-46187, which promotes the nucleotide-free form of Gα proteins, substantially inhibited 5HT uptake, prompting us to hypothesise that Gαq interacts with SERT similarly as with G-protein-coupled receptors and inhibits SERT activity by modulating transport-associated conformational changes. Taken together, our findings reveal a novel mechanism of SERT regulation and impact our understanding of sex differences in diseases associated with dysregulation of serotonin transmission, such as depression and anxiety.
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Affiliation(s)
- Jana Haase
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Aimée K C Jones
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Conor J Mc Veigh
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Eric Brown
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Gerard Clarke
- APC Microbiome Ireland and Department of Psychiatry and Neurobehavioural Science, University College Cork, Cork, Ireland
| | - Gudrun Ahnert-Hilger
- Institute of Integrative Neuroanatomy, Charité University Medicine Berlin and Max-Planck-Institute for Biophysical Chemistry Göttingen, Göttingen, Germany
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Beyond Haemostasis and Thrombosis: Platelets in Depression and Its Co-Morbidities. Int J Mol Sci 2020; 21:ijms21228817. [PMID: 33233416 PMCID: PMC7700239 DOI: 10.3390/ijms21228817] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 11/18/2020] [Accepted: 11/19/2020] [Indexed: 12/11/2022] Open
Abstract
Alongside their function in primary haemostasis and thrombo-inflammation, platelets are increasingly considered a bridge between mental, immunological and coagulation-related disorders. This review focuses on the link between platelets and the pathophysiology of major depressive disorder (MDD) and its most frequent comorbidities. Platelet- and neuron-shared proteins involved in MDD are functionally described. Platelet-related studies performed in the context of MDD, cardiovascular disease, and major neurodegenerative, neuropsychiatric and neurodevelopmental disorders are transversally presented from an epidemiological, genetic and functional point of view. To provide a complete scenario, we report the analysis of original data on the epidemiological link between platelets and depression symptoms suggesting moderating and interactive effects of sex on this association. Epidemiological and genetic studies discussed suggest that blood platelets might also be relevant biomarkers of MDD prediction and occurrence in the context of MDD comorbidities. Finally, this review has the ambition to formulate some directives and perspectives for future research on this topic.
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Mu L, Krämer SD, Warnock GI, Haider A, Bengs S, Cartolano G, Bräm DS, Keller C, Schibli R, Ametamey SM, Kaufmann PA, Gebhard C. [ 11C]mHED PET follows a two-tissue compartment model in mouse myocardium with norepinephrine transporter (NET)-dependent uptake, while [ 18F]LMI1195 uptake is NET-independent. EJNMMI Res 2020; 10:114. [PMID: 32990788 PMCID: PMC7524946 DOI: 10.1186/s13550-020-00700-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 09/14/2020] [Indexed: 12/28/2022] Open
Abstract
PURPOSE Clinical positron emission tomography (PET) imaging of the presynaptic norepinephrine transporter (NET) function provides valuable diagnostic information on sympathetic outflow and neuronal status. As data on the NET-targeting PET tracers [11C]meta-hydroxyephedrine ([11C]mHED) and [18F]LMI1195 ([18F]flubrobenguane) in murine experimental models are scarce or lacking, we performed a detailed characterization of their myocardial uptake pattern and investigated [11C]mHED uptake by kinetic modelling. METHODS [11C]mHED and [18F]LMI1195 accumulation in the heart was studied by PET/CT in FVB/N mice. To test for specific uptake by NET, desipramine, a selective NET inhibitor, was administered by intraperitoneal injection. [11C]mHED kinetic modelling with input function from an arteriovenous shunt was performed in three mice. RESULTS Both tracers accumulated in the mouse myocardium; however, only [11C]mHED uptake was significantly reduced by excess amount of desipramine. Myocardial [11C]mHED uptake was half-saturated at 88.3 nmol/kg of combined mHED and metaraminol residual. After [11C]mHED injection, a radiometabolite was detected in plasma and urine, but not in the myocardium. [11C]mHED kinetics followed serial two-tissue compartment models with desipramine-sensitive K1. CONCLUSION PET with [11C]mHED but not [18F]LMI1195 provides information on NET function in the mouse heart. [11C]mHED PET is dose-independent in the mouse myocardium at < 10 nmol/kg of combined mHED and metaraminol. [11C]mHED kinetics followed serial two-tissue compartment models with K1 representing NET transport. Myocardial [11C]mHED uptake obtained from PET images may be used to assess cardiac sympathetic integrity in mouse models of cardiovascular disease.
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Affiliation(s)
- Linjing Mu
- Department of Nuclear Medicine, University Hospital Zurich, Raemistrasse 100, 8091, Zurich, Switzerland.,Department of Chemistry and Applied Biosciences, Radiopharmaceutical Sciences, Institute of Pharmaceutical Sciences, ETH Zurich, 8093, Zurich, Switzerland
| | - Stefanie D Krämer
- Department of Chemistry and Applied Biosciences, Radiopharmaceutical Sciences, Institute of Pharmaceutical Sciences, ETH Zurich, 8093, Zurich, Switzerland
| | - Geoffrey I Warnock
- Department of Nuclear Medicine, University Hospital Zurich, Raemistrasse 100, 8091, Zurich, Switzerland.,Center for Molecular Cardiology, University of Zurich, 8952, Schlieren, Switzerland
| | - Ahmed Haider
- Department of Nuclear Medicine, University Hospital Zurich, Raemistrasse 100, 8091, Zurich, Switzerland.,Center for Molecular Cardiology, University of Zurich, 8952, Schlieren, Switzerland
| | - Susan Bengs
- Department of Nuclear Medicine, University Hospital Zurich, Raemistrasse 100, 8091, Zurich, Switzerland.,Center for Molecular Cardiology, University of Zurich, 8952, Schlieren, Switzerland
| | - Giovanni Cartolano
- Department of Chemistry and Applied Biosciences, Radiopharmaceutical Sciences, Institute of Pharmaceutical Sciences, ETH Zurich, 8093, Zurich, Switzerland
| | - Dominic S Bräm
- Department of Chemistry and Applied Biosciences, Radiopharmaceutical Sciences, Institute of Pharmaceutical Sciences, ETH Zurich, 8093, Zurich, Switzerland
| | - Claudia Keller
- Department of Chemistry and Applied Biosciences, Radiopharmaceutical Sciences, Institute of Pharmaceutical Sciences, ETH Zurich, 8093, Zurich, Switzerland
| | - Roger Schibli
- Department of Chemistry and Applied Biosciences, Radiopharmaceutical Sciences, Institute of Pharmaceutical Sciences, ETH Zurich, 8093, Zurich, Switzerland
| | - Simon M Ametamey
- Department of Chemistry and Applied Biosciences, Radiopharmaceutical Sciences, Institute of Pharmaceutical Sciences, ETH Zurich, 8093, Zurich, Switzerland
| | - Philipp A Kaufmann
- Department of Nuclear Medicine, University Hospital Zurich, Raemistrasse 100, 8091, Zurich, Switzerland
| | - Catherine Gebhard
- Department of Nuclear Medicine, University Hospital Zurich, Raemistrasse 100, 8091, Zurich, Switzerland. .,Center for Molecular Cardiology, University of Zurich, 8952, Schlieren, Switzerland.
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Koch J, Shi WX, Dashtipour K. VMAT2 inhibitors for the treatment of hyperkinetic movement disorders. Pharmacol Ther 2020; 212:107580. [PMID: 32454050 DOI: 10.1016/j.pharmthera.2020.107580] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 05/14/2020] [Indexed: 11/24/2022]
Abstract
Hyperkinetic movement disorders comprise a variety of conditions characterized by involuntary movements, which include but are not limited to tardive dyskinesia, chorea associated with Huntington's Disease, and tic disorders. The class of medications that have been used to treat these conditions includes Vesicular Monoamine Transporter-2 (VMAT2) inhibitors. In 2008, the FDA approved tetrabenazine as a treatment for chorea associated with Huntington's Disease. Optimization of the pharmacology of tetrabenazine has since led to the approval of two new VMAT2 inhibitors, deutetrabenazine and valbenazine. The objective of this review is to provide background on the role of VMAT in monoamine neurotransmission, the mechanism of VMAT2 inhibition on the treatment of hyperkinetic disorders (specifically tardive dyskinesia and chorea associated with Huntington's Disease), the pharmacology and pharmacokinetics of the commercially available VMAT2 inhibitors, and a summary of the clinical data to support application of these medications.
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Affiliation(s)
- Jessa Koch
- Pharmacy Practice, Loma Linda University School of Pharmacy, Shryock Hall, 24745 Stewart St, Loma Linda, CA 92350, United States of America; Department of Neurology, Loma Linda University School of Medicine, Faculty Medical Offices, 11370 Anderson, Suite B-100, Loma Linda, CA 92350, United States of America.
| | - Wei-Xing Shi
- Pharmaceutical, Administrative and Basic Sciences, Loma Linda University Schools of Pharmacy and Medicine, 11175 Campus St, CSP21020, Loma Linda, CA 92350, United States of America.
| | - Khashayar Dashtipour
- Pharmacy Practice, Loma Linda University School of Pharmacy, Shryock Hall, 24745 Stewart St, Loma Linda, CA 92350, United States of America; Department of Neurology, Loma Linda University School of Medicine, Faculty Medical Offices, 11370 Anderson, Suite B-100, Loma Linda, CA 92350, United States of America.
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Padmakumar M, Van Raes E, Van Geet C, Freson K. Blood platelet research in autism spectrum disorders: In search of biomarkers. Res Pract Thromb Haemost 2019; 3:566-577. [PMID: 31624776 PMCID: PMC6781926 DOI: 10.1002/rth2.12239] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 06/03/2019] [Indexed: 12/15/2022] Open
Abstract
Autism spectrum disorder (ASD) is a clinically heterogeneous neurodevelopmental disorder that is caused by gene-environment interactions. To improve its diagnosis and treatment, numerous efforts have been undertaken to identify reliable biomarkers for autism. None of them have delivered the holy grail that represents a reproducible, quantifiable, and sensitive biomarker. Though blood platelets are mainly known to prevent bleeding, they also play pivotal roles in cancer, inflammation, and neurological disorders. Platelets could serve as a peripheral biomarker or cellular model for autism as they share common biological and molecular characteristics with neurons. In particular, platelet-dense granules contain neurotransmitters such as serotonin and gamma-aminobutyric acid. Molecular players controlling granule formation and secretion are similarly regulated in platelets and neurons. The major platelet integrin receptor αIIbβ3 has recently been linked to ASD as a regulator of serotonin transport. Though many studies revealed associations between platelet markers and ASD, there is an important knowledge gap in linking these markers with autism and explaining the altered platelet phenotypes detected in autism patients. The present review enumerates studies of different biomarkers detected in ASD using platelets and highlights the future needs to bring this research to the next level and advance our understanding of this complex disorder.
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Affiliation(s)
- Manisha Padmakumar
- Department of Cardiovascular SciencesCenter for Molecular and Vascular BiologyKU LeuvenLeuvenBelgium
| | - Eveline Van Raes
- Department of Cardiovascular SciencesCenter for Molecular and Vascular BiologyKU LeuvenLeuvenBelgium
| | - Chris Van Geet
- Department of Cardiovascular SciencesCenter for Molecular and Vascular BiologyKU LeuvenLeuvenBelgium
| | - Kathleen Freson
- Department of Cardiovascular SciencesCenter for Molecular and Vascular BiologyKU LeuvenLeuvenBelgium
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Padmakumar M, Jaeken J, Ramaekers V, Lagae L, Greene D, Thys C, Van Geet C, BioResource NIHR, Stirrups K, Downes K, Turro E, Freson K. A novel missense variant in SLC18A2 causes recessive brain monoamine vesicular transport disease and absent serotonin in platelets. JIMD Rep 2019; 47:9-16. [PMID: 31240161 PMCID: PMC6498820 DOI: 10.1002/jmd2.12030] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Accepted: 01/24/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Brain monoamine vesicular transport disease is an infantile onset neurodevelopmental disorder caused by variants in SLC18A2, which codes for the vesicular monoamine transporter 2 (VMAT2) protein, involved in the transport of monoamines into synaptic vesicles and of serotonin into platelet dense granules. CASE PRESENTATION The presented case is of a child, born of healthy consanguineous parents, who exhibited hypotonia, mental disability, epilepsy, uncontrolled movements, and gastrointestinal problems. A trial treatment with L-DOPA proved unsuccessful and the exact neurological involvement could not be discerned due to normal metabolic and brain magnetic resonance imaging results.Platelet studies and whole genome sequencing were performed. At age 4, the child's platelets showed a mild aggregation and adenosine triphosphate secretion defect that could be explained by dysmorphic dense granules observed by electron microscopy. Interestingly, the dense granules were almost completely depleted of serotonin. A novel homozygous p.P316A missense variant in VMAT2 was detected in the patient and the consanguineous parents were found to be heterozygous for this variant. Although the presence of VMAT2 on platelet dense granules has been demonstrated before, this is the first report of defective platelet dense granule function related to absent serotonin storage in a patient with VMAT2 deficiency but without obvious clinical bleeding problems. CONCLUSIONS This study illustrates the homology between serotonin metabolism in brain and platelets, suggesting that these blood cells can be model cells for some pathways relevant for neurological diseases. The literature on VMAT2 deficiency is reviewed.
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Affiliation(s)
- Manisha Padmakumar
- Department of Cardiovascular SciencesCentre for Molecular and Vascular Biology, KU LeuvenLeuvenBelgium
| | - Jaak Jaeken
- Department of Development and Regeneration, PediatricsKU LeuvenLeuvenBelgium
| | - Vincent Ramaekers
- Department of NeuropediatricsCentre Hospitalier Universitaire Notre‐Dame des BruyèresLiégeBelgium
| | - Lieven Lagae
- Department of Development and Regeneration, PediatricsKU LeuvenLeuvenBelgium
| | - Daniel Greene
- NIHR BioResource – Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical CampusCambridgeUK
- Department of HematologyUniversity of Cambridge, Cambridge Biomedical CampusCambridgeUK
- Department of Haematology, Medical Research Council Biostatistics Unit, Cambridge Institute of Public Health, Cambridge Biomedical CampusCambridgeUK
| | - Chantal Thys
- Department of Cardiovascular SciencesCentre for Molecular and Vascular Biology, KU LeuvenLeuvenBelgium
| | - Chris Van Geet
- Department of Cardiovascular SciencesCentre for Molecular and Vascular Biology, KU LeuvenLeuvenBelgium
| | - NIHR BioResource
- NIHR BioResource – Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical CampusCambridgeUK
| | - Kathleen Stirrups
- NIHR BioResource – Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical CampusCambridgeUK
- Department of HematologyUniversity of Cambridge, Cambridge Biomedical CampusCambridgeUK
| | - Kate Downes
- Department of Haematology, NHS Blood and Transplant, Cambridge Biomedical CampusCambridgeUK
- NIHR BioResource – Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical CampusCambridgeUK
- Department of HematologyUniversity of Cambridge, Cambridge Biomedical CampusCambridgeUK
| | - Ernest Turro
- Department of Haematology, NHS Blood and Transplant, Cambridge Biomedical CampusCambridgeUK
- NIHR BioResource – Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical CampusCambridgeUK
- Department of HematologyUniversity of Cambridge, Cambridge Biomedical CampusCambridgeUK
- Department of Haematology, Medical Research Council Biostatistics Unit, Cambridge Institute of Public Health, Cambridge Biomedical CampusCambridgeUK
| | - Kathleen Freson
- Department of Cardiovascular SciencesCentre for Molecular and Vascular Biology, KU LeuvenLeuvenBelgium
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11
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Nyarko JNK, Quartey MO, Heistad RM, Pennington PR, Poon LJ, Knudsen KJ, Allonby O, El Zawily AM, Freywald A, Rauw G, Baker GB, Mousseau DD. Glycosylation States of Pre- and Post-synaptic Markers of 5-HT Neurons Differ With Sex and 5-HTTLPR Genotype in Cortical Autopsy Samples. Front Neurosci 2018; 12:545. [PMID: 30147642 PMCID: PMC6096231 DOI: 10.3389/fnins.2018.00545] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 07/19/2018] [Indexed: 11/13/2022] Open
Abstract
The serotonin (5-hydroxytryptamine, 5-HT) transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR) is thought to alter 5-HT signaling and contribute to behavioral and cognitive phenotypes in depression as well as Alzheimer disease (AD). We explored how well the short (S) and long (L) alleles of the 5-HTTLPR align with serotoninergic indices in 60 autopsied cortical samples from early-onset AD/EOAD and late-onset AD/LOAD donors, and age- and sex-matched controls. Stratifying data by either diagnosis-by-genotype or by sex-by-genotype revealed that the donor's 5-HTTLPR genotype, i.e., L/L, S/L, or S/S, did not affect 5-HTT mRNA or protein expression. However, the glycosylation of 5-HTT was significantly higher in control female (vs. male) samples and tended to decrease in female EOAD/LOAD samples, but remained unaltered in male LOAD samples. Glycosylated forms of the vesicular monoamine transporter (VMAT2) were lower in both male and female AD samples, while a sex-by-genotype stratification revealed a loss of VMAT2 glycosylation specifically in females with an L/L genotype. VMAT2 and 5-HTT glycosylation were correlated in male samples and inversely correlated in female samples in both stratification models. The S/S genotype aligned with lower levels of 5-HT turnover in females (but not males) and with an increased glycosylation of the post-synaptic 5-HT2C receptor. Interestingly, the changes in presynaptic glycosylation were evident primarily in female carriers of the APOE ε4 risk factor for AD. Our data do not support an association between 5-HTTLPR genotype and 5-HTT expression, but they do reveal a non-canonical association of 5-HTTLPR genotype with sex-dependent glycosylation changes in pre- and post-synaptic markers of serotoninergic neurons. These patterns of change suggest adaptive responses in 5-HT signaling and could certainly be contributing to the female prevalence in risk for either depression or AD.
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Affiliation(s)
- Jennifer N K Nyarko
- Cell Signalling Laboratory, Department of Psychiatry, University of Saskatchewan, Saskatoon, SK, Canada
| | - Maa O Quartey
- Cell Signalling Laboratory, Department of Psychiatry, University of Saskatchewan, Saskatoon, SK, Canada
| | - Ryan M Heistad
- Cell Signalling Laboratory, Department of Psychiatry, University of Saskatchewan, Saskatoon, SK, Canada
| | - Paul R Pennington
- Cell Signalling Laboratory, Department of Psychiatry, University of Saskatchewan, Saskatoon, SK, Canada
| | - Lisa J Poon
- Cell Signalling Laboratory, Department of Psychiatry, University of Saskatchewan, Saskatoon, SK, Canada
| | - Kaeli J Knudsen
- Cell Signalling Laboratory, Department of Psychiatry, University of Saskatchewan, Saskatoon, SK, Canada
| | - Odette Allonby
- Cell Signalling Laboratory, Department of Psychiatry, University of Saskatchewan, Saskatoon, SK, Canada
| | - Amr M El Zawily
- Department of Pathology and Laboratory Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Andrew Freywald
- Department of Pathology and Laboratory Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Gail Rauw
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, Canada
| | - Glen B Baker
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, Canada
| | - Darrell D Mousseau
- Cell Signalling Laboratory, Department of Psychiatry, University of Saskatchewan, Saskatoon, SK, Canada
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12
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Abstract
Platelet dense granules (DGs) are storage organelles for calcium ions, small organic molecules such as ADP and serotonin, and larger polyphosphates that are secreted upon platelet stimulation to enhance platelet activation, adhesion, and stabilization at sites of vascular damage. DGs are thought to fully mature within megakaryocytes (MKs) prior to platelet formation. Here we challenge this notion by exploiting vital fluorescent dyes to distinguish mildly acidic DGs from highly acidic compartments by microscopy in platelets and MKs. In isolated primary mouse platelets, compartments labeled by mepacrine - a fluorescent weak base that accumulates in DGs - are readily distinguishable from highly acidic compartments, likely lysosomes, that are labeled by the acidic pH indicator, LysoTracker, and from endolysosomes and alpha granules labeled by internalized and partially digested DQ™ BSA. By contrast, in murine fetal liver- and human CD34+ cell-derived MKs and the megakaryocytoid cell lines, MEG-01 and differentiated G1ME2, labeling by mepacrine overlapped nearly completely with labeling by LysoTracker and partially with labeling by DQ™ BSA. Mepacrine labeling in G1ME2-derived MKs was fully sensitive to proton ATPase inhibitors, but was only partially sensitive in platelets. These data indicate that mepacrine in MKs accumulates as a weak base in endolysosomes but is likely pumped into or retained in separate DGs in platelets. Fluorescent puncta that labeled uniquely for mepacrine were first evident in G1ME2-derived proplatelets, suggesting that DGs undergo a maturation step that initiates in the final stages of MK differentiation.
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13
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Abstract
Platelet dense granules (DGs) are membrane bound compartments that store polyphosphate and small molecules such as ADP, ATP, Ca2+, and serotonin. The release of DG contents plays a central role in platelet aggregation to form a hemostatic plug. Accordingly, congenital deficiencies in the biogenesis of platelet DGs underlie human genetic disorders that cause storage pool disease and manifest with prolonged bleeding. DGs belong to a family of lysosome-related organelles, which also includes melanosomes, the compartments where the melanin pigments are synthesized. These organelles share several characteristics including an acidic lumen and, at least in part, the molecular machinery involved in their biogenesis. As a result, many genes affect both DG and melanosome biogenesis and the corresponding patients present not only with bleeding but also with oculocutaneous albinism. The identification and characterization of such genes has been instrumental in dissecting the pathways responsible for organelle biogenesis. Because the study of melanosome biogenesis has advanced more rapidly, this knowledge has been extrapolated to explain how DGs are produced. However, some progress has recently been made in studying platelet DG biogenesis directly in megakaryocytes and megakaryocytoid cells. DGs originate from an endosomal intermediate compartment, the multivesicular body. Maturation and differentiation into a DG begins when newly synthesized DG-specific proteins are delivered from early/recycling endosomal compartments. The machinery that orchestrates this vesicular trafficking is composed of a combination of both ubiquitous and cell type-specific proteins. Here, we review the current knowledge on DG biogenesis. In particular, we focus on the individual human and murine genes encoding the molecular machinery involved in this process and how their deficiencies result in disease.
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Affiliation(s)
- Andrea L Ambrosio
- a Department of Biochemistry and Molecular Biology , Colorado State University , Fort Collins , Colorado , USA
| | - Santiago M Di Pietro
- a Department of Biochemistry and Molecular Biology , Colorado State University , Fort Collins , Colorado , USA
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14
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Sulzer D, Cragg SJ, Rice ME. Striatal dopamine neurotransmission: regulation of release and uptake. ACTA ACUST UNITED AC 2016; 6:123-148. [PMID: 27141430 DOI: 10.1016/j.baga.2016.02.001] [Citation(s) in RCA: 236] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Dopamine (DA) transmission is governed by processes that regulate release from axonal boutons in the forebrain and the somatodendritic compartment in midbrain, and by clearance by the DA transporter, diffusion, and extracellular metabolism. We review how axonal DA release is regulated by neuronal activity and by autoreceptors and heteroreceptors, and address how quantal release events are regulated in size and frequency. In brain regions densely innervated by DA axons, DA clearance is due predominantly to uptake by the DA transporter, whereas in cortex, midbrain, and other regions with relatively sparse DA inputs, the norepinephrine transporter and diffusion are involved. We discuss the role of DA uptake in restricting the sphere of influence of DA and in temporal accumulation of extracellular DA levels upon successive action potentials. The tonic discharge activity of DA neurons may be translated into a tonic extracellular DA level, whereas their bursting activity can generate discrete extracellular DA transients.
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Affiliation(s)
- David Sulzer
- Depts of Psychiatry, Neurology, & Pharmacology, NY State Psychiatric Institute, Columbia University, New York, NY, USA
| | - Stephanie J Cragg
- Dept Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Margaret E Rice
- Depts of Neurosurgery & Neuroscience and Physiology, New York University School of Medicine, New York, NY, USA
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15
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Takamori S. Presynaptic Molecular Determinants of Quantal Size. Front Synaptic Neurosci 2016; 8:2. [PMID: 26903855 PMCID: PMC4744840 DOI: 10.3389/fnsyn.2016.00002] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 01/25/2016] [Indexed: 01/22/2023] Open
Abstract
The quantal hypothesis for the release of neurotransmitters at the chemical synapse has gained wide acceptance since it was first worked out at the motor endplate in frog skeletal muscle in the 1950’s. Considering the morphological identification of synaptic vesicles (SVs) at the nerve terminals that appeared to be homogeneous in size, the hypothesis proposed that signal transduction at synapses is mediated by the release of neurotransmitters packed in SVs that are individually uniform in size; the amount of transmitter in a synaptic vesicle is called a quantum. Although quantal size—the amplitude of the postsynaptic response elicited by the release of neurotransmitters from a single vesicle—clearly depends on the number and sensitivity of the postsynaptic receptors, accumulating evidence has also indicated that the amount of neurotransmitters stored in SVs can be altered by various presynaptic factors. Here, I provide an overview of the concepts and underlying presynaptic molecular underpinnings that may regulate quantal size.
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Affiliation(s)
- Shigeo Takamori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University Kyoto, Japan
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16
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Laporta J, Peñagaricano F, Hernandez LL. Transcriptomic Analysis of the Mouse Mammary Gland Reveals New Insights for the Role of Serotonin in Lactation. PLoS One 2015; 10:e0140425. [PMID: 26470019 PMCID: PMC4607441 DOI: 10.1371/journal.pone.0140425] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 09/17/2015] [Indexed: 11/18/2022] Open
Abstract
Serotonin regulates numerous processes in the mammary gland. Our objective was to discover novel genes, pathways and functions which serotonin modulates during lactation. The rate limiting enzyme in the synthesis of non-neuronal serotonin is tryptophan-hydroxylase (TPH1). Therefore, we used TPH1 deficient dams (KO; serotonin deficient, n = 4) and compared them to wild-type (WT; n = 4) and rescue (RC; KO + 100 mg/kg 5-hydroxytryptophan injected daily, n = 4) dams. Mammary tissues were collected on day 10 of lactation. Total RNA extraction, amplification, library preparation and sequencing were performed following the Illumina mRNA-Seq. Overall, 97 and 204 genes (false discovery rate, FDR ≤ 0.01) exhibited a minimum of a 2-fold expression difference between WT vs. KO and WT vs. RC dams, respectively. Most differentially expressed genes were related to calcium homeostasis, apoptosis regulation, cell cycle, cell differentiation and proliferation, and the immune response. Additionally, gene set enrichment analysis using Gene Ontology and Medical Subject Headings databases revealed the alteration of several biological processes (FDR ≤ 0.01) including fat cell differentiation and lipid metabolism, regulation of extracellular signal-related kinase and mitogen-activated kinase cascades, insulin resistance, nuclear transport, membrane potential regulation, and calcium release from the endoplasmic reticulum into the cytosol. The majority of the biological processes and pathways altered in the KO dams are central for mammary gland homeostasis. Increasing peripheral serotonin in the RC dams affects specific pathways that favor lactation. Our data confirms the importance of serotonin during lactation in the mammary gland.
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Affiliation(s)
- Jimena Laporta
- Department of Animal Sciences, University of Florida, Gainesville, Florida, United States of America
| | - Francisco Peñagaricano
- Department of Animal Sciences, University of Florida, Gainesville, Florida, United States of America
- University of Florida Genetics Institute, University of Florida, Gainesville, Florida, United States of America
| | - Laura L. Hernandez
- Department of Dairy Science, University of Wisconsin, Madison, Wisconsin, United States of America
- * E-mail:
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17
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Chen Y, Leon-Ponte M, Pingle SC, O'Connell PJ, Ahern GP. T lymphocytes possess the machinery for 5-HT synthesis, storage, degradation and release. Acta Physiol (Oxf) 2015; 213:860-7. [PMID: 25683571 DOI: 10.1111/apha.12470] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 11/11/2014] [Accepted: 02/09/2015] [Indexed: 02/02/2023]
Abstract
AIM Although activated T lymphocytes express tryptophan hydroxylase 1 and produce 5-HT, the metabolic fate and cellular handling of this 5-HT is unclear. Here, we investigated key proteins in T cells linked to 5-HT metabolism and storage and compare differences in 5-HT synthesis and metabolism between T-cell subsets. METHODS We cultured human Jurkat T cells and mouse splenic CD3(+) , CD4(+) and CD8(+) T cells with or without T-cell activators (phorbol ester/ionomycin, concavalin A or plate-bound anti-CD3 antibody). Subsequently, we measured mRNA and/or protein for monoamine oxidase A and B, vesicular monoamine transporter 1 and 2, N-acetyl transferase and tryptophan hydroxylase 1. In addition, we measured the release of exogenously loaded [(3) H]5-HT and endogenously synthesized 5-HT from CD4(+) and CD8(+) T-cell subsets. RESULTS Human and mouse T cells selectively express monoamine oxidase A. Following T-cell activation, mRNA levels of MAO-A increase robustly in parallel with tryptophan hydroxylase 1. Concomitant with these changes, T cells increase the expression of the type 1 vesicular monoamine transporter. Raised intracellular [Ca(2+) ] rapidly releases preloaded [(3) H]5-HT from CD4(+) and CD8(+) T cells indicating that these cells have the capacity for the storage and regulated secretion of 5-HT. Notably, both the expression of tryptophan hydroxylase 1 and monoamine oxidase A, and 5-HT production are significantly greater in CD8(+) compared with CD4(+) T cells. CONCLUSION These data reveal coordinated changes in 5-HT production, metabolism and storage that may optimize 5-HT secretion from the CD8(+) T cell subset in response to activation stimuli.
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Affiliation(s)
- Y. Chen
- Department of Pharmacology and Physiology; Georgetown University; Washington DC USA
| | - M. Leon-Ponte
- Stiller Center for Technology Commercialization; Western University; London ON Canada
| | - S. C. Pingle
- Department of Pharmacology and Physiology; Georgetown University; Washington DC USA
| | - P. J. O'Connell
- School of Surgery; University of Western Australia; Perth WA Australia
| | - G. P. Ahern
- Department of Pharmacology and Physiology; Georgetown University; Washington DC USA
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18
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Kamato D, Thach L, Bernard R, Chan V, Zheng W, Kaur H, Brimble M, Osman N, Little PJ. Structure, Function, Pharmacology, and Therapeutic Potential of the G Protein, Gα/q,11. Front Cardiovasc Med 2015; 2:14. [PMID: 26664886 PMCID: PMC4671355 DOI: 10.3389/fcvm.2015.00014] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 03/11/2015] [Indexed: 11/19/2022] Open
Abstract
G protein coupled receptors (GPCRs) are one of the major classes of cell surface receptors and are associated with a group of G proteins consisting of three subunits termed alpha, beta, and gamma. G proteins are classified into four families according to their α subunit; Gαi, Gαs, Gα12/13, and Gαq. There are several downstream pathways of Gαq of which the best known is upon activation via guanosine triphosphate (GTP), Gαq activates phospholipase Cβ, hydrolyzing phosphatidylinositol 4,5-biphosphate into diacylglycerol and inositol triphosphate and activating protein kinase C and increasing calcium efflux from the endoplasmic reticulum. Although G proteins, in particular, the Gαq/11 are central elements in GPCR signaling, their actual roles have not yet been thoroughly investigated. The lack of research of the role on Gαq/11 in cell biology is partially due to the obscure nature of the available pharmacological agents. YM-254890 is the most useful Gαq-selective inhibitor with antiplatelet, antithrombotic, and thrombolytic effects. YM-254890 inhibits Gαq signaling pathways by preventing the exchange of guanosine diphosphate for GTP. UBO-QIC is a structurally similar compound to YM-254890, which can inhibit platelet aggregation and cause vasorelaxation in rats. Many agents are available for the study of signaling downstream of Gαq/11. The role of G proteins could potentially represent a novel therapeutic target. This review will explore the range of pharmacological and molecular tools available for the study of the role of Gαq/11 in GPCR signaling.
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Affiliation(s)
- Danielle Kamato
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| | - Lyna Thach
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| | - Rebekah Bernard
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| | - Vincent Chan
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| | - Wenhua Zheng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Centre , Guangzhou , China ; Faculty of Health Sciences, University of Macau , Macau , China
| | - Harveen Kaur
- Department of Chemistry, University of Auckland , Auckland , New Zealand
| | - Margaret Brimble
- Department of Chemistry, University of Auckland , Auckland , New Zealand
| | - Narin Osman
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| | - Peter J Little
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
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19
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Laporta J, Keil KP, Weaver SR, Cronick CM, Prichard AP, Crenshaw TD, Heyne GW, Vezina CM, Lipinski RJ, Hernandez LL. Serotonin regulates calcium homeostasis in lactation by epigenetic activation of hedgehog signaling. Mol Endocrinol 2014; 28:1866-74. [PMID: 25192038 DOI: 10.1210/me.2014-1204] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Calcium homeostasis during lactation is critical for maternal and neonatal health. We previously showed that nonneuronal/peripheral serotonin [5-hydroxytryptamine (5-HT)] causes the lactating mammary gland to synthesize and secrete PTHrP in an acute fashion. Here, using a mouse model, we found that genetic inactivation of tryptophan hydroxylase 1 (Tph1), which catalyzes the rate-limiting step in peripheral 5-HT synthesis, reduced circulating and mammary PTHrP expression, osteoclast activity, and maternal circulating calcium concentrations during the transition from pregnancy to lactation. Tph1 inactivation also reduced sonic hedgehog signaling in the mammary gland during lactation. Each of these deficiencies was rescued by daily injections of 5-hydroxy-L-tryptophan (an immediate precursor of 5-HT) to Tph1-deficient dams. We used immortalized mouse embryonic fibroblasts to demonstrate that 5-HT induces PTHrP through a sonic hedgehog-dependent signal transduction mechanism. We also found that 5-HT altered DNA methylation of the Shh gene locus, leading to transcriptional initiation at an alternate start site and formation of a variant transcript in mouse embryonic fibroblasts in vitro and in mammary tissue in vivo. These results support a new paradigm of 5-HT-mediated Shh regulation involving DNA methylation remodeling and promoter switching. In addition to having immediate implications for lactation biology, identification and characterization of a novel functional regulatory relationship between nonneuronal 5-HT, hedgehog signaling, and PTHrP offers new avenues for the study of these important factors in development and disease.
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Affiliation(s)
- Jimena Laporta
- Departments of Dairy Science (J.L., S.R.W., C.M.C., A.P.P., L.L.H.), Comparative Biosciences (K.P.K., G.W.H., C.M.V., R.J.L.), and Animal Science (T.D.C.), University of Wisconsin-Madison, Madison, Wisconsin 53706
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20
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Mosienko V, Matthes S, Hirth N, Beis D, Flinders M, Bader M, Hansson AC, Alenina N. Adaptive changes in serotonin metabolism preserve normal behavior in mice with reduced TPH2 activity. Neuropharmacology 2014; 85:73-80. [PMID: 24863038 DOI: 10.1016/j.neuropharm.2014.05.015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Revised: 05/02/2014] [Accepted: 05/10/2014] [Indexed: 01/29/2023]
Abstract
Polymorphisms in the TPH2 gene coding for the serotonin synthesizing enzyme in the brain are considered as risk factors associated with depression and anxiety in humans. However, whether a certain variation in the TPH2 gene leads to decreased brain serotonin production and development of psychological abnormalities remains unresolved. We generated a new mouse model, carrying one Tph2-null allele and one Tph21473G-allele, coding for a hypoactive form of the enzyme. We tested these mice along with C57BL/6 mice (Tph2C/C), congenic C57BL/6 mice homozygous for the Tph21473G-allele (Tph2G/G), and heterozygous Tph2-deficient mice (Tph2C/-) for anxiety- and depression-like behavior, and evaluated brain serotonin metabolism and 5-HT1AR signaling by high-performance liquid chromatography and quantitative autoradiography, respectively. Progressive reduction in TPH2 activity had no effect on emotional behavior, and only slightly affected brain serotonin levels. However, serotonin degradation rate was drastically decreased in mice with reduced TPH2 activity, thereby compensating for the lowered rate of serotonin production in these mice. In addition, the hypothermic response to the 5-HT1AR agonist, 8-OH-DPAT, was attenuated in mice with reduced serotonin production. In contrast, 5-HT1A autoreceptor density and G-protein coupling were not changed in mice with gradual decrease in central serotonin. Taken together, these data suggest that in conditions of reduced serotonin production lowered serotonin degradation rate contributes to the maintenance of brain serotonin at levels sufficient for adequate behavior responses. These findings reveal that decreased TPH2 activity cannot be considered a reliable predisposition factor for impaired emotional behavior.
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Affiliation(s)
| | - Susann Matthes
- Max-Delbrueck-Center for Molecular Medicine, Berlin-Buch, Germany; Humboldt-Universität Berlin, Berlin, Germany
| | - Natalie Hirth
- Institute of Psychopharmacology at the Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Daniel Beis
- Max-Delbrueck-Center for Molecular Medicine, Berlin-Buch, Germany; Humboldt-Universität Berlin, Berlin, Germany
| | - Michael Flinders
- Max-Delbrueck-Center for Molecular Medicine, Berlin-Buch, Germany
| | - Michael Bader
- Max-Delbrueck-Center for Molecular Medicine, Berlin-Buch, Germany
| | - Anita C Hansson
- Institute of Psychopharmacology at the Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Natalia Alenina
- Max-Delbrueck-Center for Molecular Medicine, Berlin-Buch, Germany.
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21
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Bernstein AI, Stout KA, Miller GW. The vesicular monoamine transporter 2: an underexplored pharmacological target. Neurochem Int 2014; 73:89-97. [PMID: 24398404 DOI: 10.1016/j.neuint.2013.12.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 12/06/2013] [Accepted: 12/09/2013] [Indexed: 12/21/2022]
Abstract
Active transport of neurotransmitters into synaptic vesicles is required for their subsequent exocytotic release. In the monoamine system, this process is carried out by the vesicular monoamine transporters (VMAT1 and VMAT2). These proteins are responsible for vesicular packaging of dopamine, norepinephrine, serotonin, and histamine. These proteins are essential for proper neuronal function; however, compared to their plasma membrane counterparts, there are few drugs available that target these vesicular proteins. This is partly due to the added complexity of crossing the plasma membrane, but also to the technical difficulty of assaying for vesicular uptake in high throughput. Until recently, reagents to enable high throughput screening for function of these vesicular neurotransmitter transporters have not been available. Fortunately, novel compounds and methods are now making such screening possible; thus, a renewed focus on these transporters as potential targets is timely and necessary.
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Affiliation(s)
- Alison I Bernstein
- Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA 30322, USA
| | - Kristen A Stout
- Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA 30322, USA
| | - Gary W Miller
- Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA 30322, USA; Center for Neurodegenerative Diseases, Emory University, Atlanta, GA 30322, USA; Department of Pharmacology, Emory University, Atlanta, GA 30322, USA; Department of Neurology, Emory University, Atlanta, GA 30322, USA.
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22
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Ambrosio AL, Boyle JA, Di Pietro SM. Mechanism of platelet dense granule biogenesis: study of cargo transport and function of Rab32 and Rab38 in a model system. Blood 2012; 120:4072-81. [PMID: 22927249 PMCID: PMC3496959 DOI: 10.1182/blood-2012-04-420745] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 08/12/2012] [Indexed: 12/21/2022] Open
Abstract
Dense granules are important in platelet aggregation to form a hemostatic plug as evidenced by the increased bleeding time in mice and humans with dense granule deficiency. Dense granules also are targeted by antiplatelet agents because of their role in thrombus formation. Therefore, the molecular understanding of the dense granule and its biogenesis is of vital importance. In this work, we establish a human megakaryocytic cell line (MEG-01) as a model system for the study of dense granule biogenesis using a variety of cell biology and biochemical approaches. Using this model system, we determine the late endocytic origin of these organelles by colocalization of the internalized fluid phase marker dextran with both mepacrine and transmembrane dense granule proteins. By mistargeting of mutant dense granule proteins, we demonstrate that sorting signals recognized by adaptor protein-3 are necessary for normal transport to dense granules. Furthermore, we show that tissue-specific Rab32 and Rab38 are crucial for the fusion of vesicles containing dense granule cargo with the maturing organelle. This work sheds light on the biogenesis of dense granules at the molecular level and opens the possibility of using this powerful model system for the investigation of new components of the biogenesis machinery.
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Affiliation(s)
- Andrea L Ambrosio
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870, USA
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23
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Vowinckel J, Stahlberg S, Paulmann N, Bluemlein K, Grohmann M, Ralser M, Walther DJ. Histaminylation of glutamine residues is a novel posttranslational modification implicated in G-protein signaling. FEBS Lett 2012; 586:3819-24. [PMID: 23022564 PMCID: PMC3743044 DOI: 10.1016/j.febslet.2012.09.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 09/11/2012] [Accepted: 09/16/2012] [Indexed: 01/14/2023]
Abstract
Posttranslational modifications (PTM) have been shown to be essential for protein function and signaling. Here we report the identification of a novel modification, protein transfer of histamine, and provide evidence for its function in G protein signaling. Histamine, known as neurotransmitter and mediator of the inflammatory response, was found incorporated into mastocytoma proteins. Histaminylation was dependent on transglutaminase II. Mass spectrometry confirmed histamine modification of the small and heterotrimeric G proteins Cdc42, Gαo1 and Gαq. The modification was specific for glutamine residues in the catalytic core, and triggered their constitutive activation. TGM2-mediated histaminylation is thus a novel PTM that functions in G protein signaling. Protein αmonoaminylations, thus including histaminylation, serotonylation, dopaminylation and norepinephrinylation, hence emerge as a novel class of regulatory PTMs.
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Affiliation(s)
- Jakob Vowinckel
- Max Planck Institute for Molecular Genetics, Berlin, Germany.
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24
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Bernstein AI, Stout KA, Miller GW. A fluorescent-based assay for live cell, spatially resolved assessment of vesicular monoamine transporter 2-mediated neurotransmitter transport. J Neurosci Methods 2012; 209:357-66. [PMID: 22698664 PMCID: PMC3429701 DOI: 10.1016/j.jneumeth.2012.06.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 06/01/2012] [Accepted: 06/04/2012] [Indexed: 10/28/2022]
Abstract
The vesicular monoamine transporter 2 (VMAT2; Slc18a2) packages monoamines into synaptic vesicles. Monoamine homeostasis is highly regulated and dysfunction may play a role in Parkinson's disease, Huntington's disease, drug addiction, and neuropsychiatric disorders. The primary function of VMAT2 is to sequester monoamine neurotransmitters into vesicles for subsequent release; it also sequesters toxicants away from cytosolic sites of action. Identification of compounds that modify the action of VMAT2 may be useful as therapeutic agents for preventing or reversing monoamine-related toxicity. Current methods for measuring VMAT2 function are unable to assess uptake in intact cells. Here, we adapted the Neurotransmitter Uptake Assay (Molecular Devices) to develop a measure of VMAT2 function in live whole cells. This assay contains a fluorescent compound, which is transported into cells by the plasma membrane monoamine transporters and has been marketed as a rapid, high-throughput, plate reader based assay for function of these plasma membrane transporters. We demonstrate a modified version of this assay that can be used to visualize and measure transport into vesicles by VMAT2. HEK293 cell lines stably expressing the dopamine transporter and a mCherry-VMAT2 fusion protein were generated. Confocal microscopy confirmed that the fluorescent compound is transported into mCherry-positive compartments. Furthermore, the VMAT2-specific inhibitor tetrabenazine (TBZ) blocks uptake into the mCherry-positive compartment. Confocal images can be analyzed to generate a measure of VMAT2 activity. In summary, we demonstrate a method for spatially resolved analysis of VMAT2-mediated uptake in live intact cells.
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Affiliation(s)
- Alison I. Bernstein
- Center for Neurodegenerative Disease, Emory University, Atlanta, GA 30322, United States
- Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA 30322, United States
| | - Kristen A. Stout
- Center for Neurodegenerative Disease, Emory University, Atlanta, GA 30322, United States
- Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA 30322, United States
| | - Gary W. Miller
- Center for Neurodegenerative Disease, Emory University, Atlanta, GA 30322, United States
- Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA 30322, United States
- Department of Neurology, Emory University, 1518 Clifton Road, Atlanta, GA 30322, United States
- Department of Pharmacology, Emory University, 1518 Clifton Road, Atlanta, GA 30322, United States
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25
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Blakely RD, Edwards RH. Vesicular and plasma membrane transporters for neurotransmitters. Cold Spring Harb Perspect Biol 2012; 4:a005595. [PMID: 22199021 PMCID: PMC3281572 DOI: 10.1101/cshperspect.a005595] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The regulated exocytosis that mediates chemical signaling at synapses requires mechanisms to coordinate the immediate response to stimulation with the recycling needed to sustain release. Two general classes of transporter contribute to release, one located on synaptic vesicles that loads them with transmitter, and a second at the plasma membrane that both terminates signaling and serves to recycle transmitter for subsequent rounds of release. Originally identified as the target of psychoactive drugs, these transport systems have important roles in transmitter release, but we are only beginning to understand their contribution to synaptic transmission, plasticity, behavior, and disease. Recent work has started to provide a structural basis for their activity, to characterize their trafficking and potential for regulation. The results indicate that far from the passive target of psychoactive drugs, neurotransmitter transporters undergo regulation that contributes to synaptic plasticity.
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Affiliation(s)
- Randy D Blakely
- Department of Pharmacology and Psychiatry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8548, USA
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26
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Walther DJ, Stahlberg S, Vowinckel J. Novel roles for biogenic monoamines: from monoamines in transglutaminase-mediated post-translational protein modification to monoaminylation deregulation diseases. FEBS J 2011; 278:4740-55. [DOI: 10.1111/j.1742-4658.2011.08347.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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27
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Narboux-Nême N, Sagné C, Doly S, Diaz SL, Martin CBP, Angenard G, Martres MP, Giros B, Hamon M, Lanfumey L, Gaspar P, Mongeau R. Severe serotonin depletion after conditional deletion of the vesicular monoamine transporter 2 gene in serotonin neurons: neural and behavioral consequences. Neuropsychopharmacology 2011; 36:2538-50. [PMID: 21814181 PMCID: PMC3194080 DOI: 10.1038/npp.2011.142] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The vesicular monoamine transporter type 2 gene (VMAT2) has a crucial role in the storage and synaptic release of all monoamines, including serotonin (5-HT). To evaluate the specific role of VMAT2 in 5-HT neurons, we produced a conditional ablation of VMAT2 under control of the serotonin transporter (slc6a4) promoter. VMAT2(sert-cre) mice showed a major (-95%) depletion of 5-HT levels in the brain with no major alterations in other monoamines. Raphe neurons contained no 5-HT immunoreactivity in VMAT2(sert-cre) mice but developed normal innervations, as assessed by both tryptophan hydroxylase 2 and 5-HT transporter labeling. Increased 5-HT(1A) autoreceptor coupling to G protein, as assessed with agonist-stimulated [(35)S]GTP-γ-S binding, was observed in the raphe area, indicating an adaptive change to reduced 5-HT transmission. Behavioral evaluation in adult VMAT2(sert-cre) mice showed an increase in escape-like reactions in response to tail suspension and anxiolytic-like response in the novelty-suppressed feeding test. In an aversive ultrasound-induced defense paradigm, VMAT2(sert-cre) mice displayed a major increase in escape-like behaviors. Wild-type-like defense phenotype could be rescued by replenishing intracellular 5-HT stores with chronic pargyline (a monoamine oxidase inhibitor) treatment. Pargyline also allowed some form of 5-HT release, although in reduced amounts, in synaptosomes from VMAT2(sert-cre) mouse brain. These findings are coherent with the notion that 5-HT has an important role in anxiety, and provide new insights into the role of endogenous 5-HT in defense behaviors.
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Affiliation(s)
- Nicolas Narboux-Nême
- INSERM, UMR-S 839, Institut du Fer à Moulin, Paris, France,Université Pierre and Marie Curie, Paris, France
| | - Corinne Sagné
- CNRS UMR8192-Université Paris Descartes, Paris, France
| | - Stephane Doly
- INSERM, UMR-S 839, Institut du Fer à Moulin, Paris, France,Université Pierre and Marie Curie, Paris, France
| | - Silvina L Diaz
- INSERM, UMR-S 839, Institut du Fer à Moulin, Paris, France,Université Pierre and Marie Curie, Paris, France
| | - Cédric B P Martin
- Université Pierre and Marie Curie, Paris, France,INSERM, U894, Paris, France
| | - Gaelle Angenard
- INSERM, UMR-S 839, Institut du Fer à Moulin, Paris, France,Université Pierre and Marie Curie, Paris, France
| | - Marie-Pascale Martres
- Université Pierre and Marie Curie, Paris, France,INSERM, U952, Paris, France,CNRS UMR7224, Paris, France
| | - Bruno Giros
- Université Pierre and Marie Curie, Paris, France,INSERM, U952, Paris, France,CNRS UMR7224, Paris, France,Department of Psychiatry, Douglas Hospital, McGill University, Montreal, Canada
| | - Michel Hamon
- Université Pierre and Marie Curie, Paris, France,INSERM, U894, Paris, France
| | - Laurence Lanfumey
- Université Pierre and Marie Curie, Paris, France,INSERM, U894, Paris, France
| | - Patricia Gaspar
- INSERM, UMR-S 839, Institut du Fer à Moulin, Paris, France,Université Pierre and Marie Curie, Paris, France,INSERM UMR-S 839, Institut du Fer à Moulin, 17 Rue du Fer à Moulin, 75005, Paris, France, Tel: +331 45 87 61 11, Fax: +331 45 87 61 30, E-mail :
| | - Raymond Mongeau
- Université Pierre and Marie Curie, Paris, France,INSERM, U894, Paris, France
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Distribution of vesicular monoamine transporter 2 protein in human brain: implications for brain imaging studies. J Cereb Blood Flow Metab 2011; 31:2065-75. [PMID: 21522164 PMCID: PMC3208151 DOI: 10.1038/jcbfm.2011.63] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The choice of reference region in positron emission tomography (PET) human brain imaging of the vesicular monoamine transporter 2 (VMAT2), a marker of striatal dopamine innervation, has been arbitrary, with cerebellar, whole cerebral, frontal, or occipital cortices used. To establish whether levels of VMAT2 are in fact low in these cortical areas, we measured VMAT2 protein distribution by quantitative immunoblotting in autopsied normal human brain (n=6). Four or five species of VMAT2 immunoreactivity (75, 55, 52, 45, 35 kDa) were detected, which were all markedly reduced in intensity in nigrostriatal regions of patients with parkinsonian conditions versus matched controls (n=9 to 10 each). Using the intact VMAT2 immunoreactivity, cerebellar and cerebral neocortices had levels of the transporter >100-fold lower than the VMAT2-rich striatum and with no significant differences among the cortical regions. We conclude that human cerebellar and cerebral cortices contain negligible VMAT2 protein versus the striatum and, in this respect, all satisfy a criterion for a useful reference region for VMAT2 imaging. The slightly lower PET signal for VMAT2 binding in occipital (the currently preferred reference region) versus cerebellar cortex might not therefore be explained by differences in VMAT2 protein itself but possibly by other imaging variables, for example, partial volume effects.
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29
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Sager JJ, Torres GE. Proteins interacting with monoamine transporters: current state and future challenges. Biochemistry 2011; 50:7295-310. [PMID: 21797260 DOI: 10.1021/bi200405c] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Plasma membrane and vesicular transporters for the biogenic amines, dopamine, norepinephrine, and serotonin, represent a group of proteins that play a crucial role in the regulation of neurotransmission. Clinically, mono amine transporters are the primary targets for the actions of many therapeutic agents used to treat mood disorders, as well as the site of action for highly addictive psychostimulants such as cocaine, amphetamine, methamphetamine, and 3,4-methylenedioxymethamphetamine. Over the past decade, the use of approaches such as yeast two-hybrid and proteomics has identified a multitude of transporter interacting proteins, suggesting that the function and regulation of these transporters are more complex than previously anticipated. With the increasing number of interacting proteins, the rules dictating transporter synthesis, assembly, targeting, trafficking, and function are beginning to be deciphered. Although many of these protein interactions have yet to be fully characterized, current knowledge is beginning to shed light on novel transporter mechanisms involved in monoamine homeostasis, the molecular actions of psychostimulants, and potential disease mechanisms. While future studies resolving the spatial and temporal resolution of these, and yet unknown, interactions will be needed, the realization that monoamine transporters do not work alone opens the path to a plethora of possible pharmacological interventions.
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Affiliation(s)
- Jonathan J Sager
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
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30
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Ge S, Woo E, White JG, Haynes CL. Electrochemical measurement of endogenous serotonin release from human blood platelets. Anal Chem 2011; 83:2598-604. [PMID: 21384903 DOI: 10.1021/ac102929y] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Platelet aggregation in the bloodstream is tightly associated with the secretory function of platelets based on several types of cytoplasmic secretory granules, each sequestering distinct chemical messenger species. Dense-body granules are one prominent type of secretory granule responsible for storing small molecule chemical messengers. Upon platelet activation, the timely and rapid release of these small molecules is critical in facilitating platelet aggregation. Therefore, techniques capable of measuring real-time granule content release are needed to understand the fundamental properties of platelet secretion and aggregation. Existing techniques lack adequate time resolution or require potentially toxic exogenous reagents for real-time measurement of granule content release. Herein, we demonstrate a label-free electrochemical method based on the endogenous electroactive chemical messenger serotonin (5-hydroxytryptamine or 5-HT) for the real-time measurement of dense-body granule secretion from platelet suspensions; fast-scan cyclic voltammetry (FSCV) using carbon-fiber microelectrodes was chosen on the basis of its excellent temporal resolution, high sensitivity, and the ability to provide the electrochemical signature cyclic voltammograms for molecular identification. Real-time serotonin release from thrombin-stimulated human platelet suspensions was successfully measured, and the amount and time course of the bulk serotonin release were found to agree well with data obtained from single platelet measurements, thus confirming accurate characterization of granular secretion. Furthermore, this electrochemical method was applied to study the stimulation-secretion coupling in platelets, serotonin storage and release dynamics with applied pharmacological agents, and chemical messenger storage deficiency in Hermansky-Pudlak Syndrome (HPS) platelets, and the potential of this method to reveal secretion behavior in both normal and diseased platelets has clearly been demonstrated.
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Affiliation(s)
- Shencheng Ge
- Department of Chemistry, College of Science and Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
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31
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Scheuch K, Höltje M, Budde H, Lautenschlager M, Heinz A, Ahnert-Hilger G, Priller J. Lithium modulates tryptophan hydroxylase 2 gene expression and serotonin release in primary cultures of serotonergic raphe neurons. Brain Res 2010; 1307:14-21. [DOI: 10.1016/j.brainres.2009.10.027] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Revised: 10/06/2009] [Accepted: 10/12/2009] [Indexed: 12/13/2022]
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32
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Requena DF, Parra LA, Baust TB, Quiroz M, Leak RK, Garcia-Olivares J, Torres GE. The molecular chaperone Hsc70 interacts with the vesicular monoamine transporter-2. J Neurochem 2009; 110:581-94. [DOI: 10.1111/j.1471-4159.2009.06135.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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33
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Matondo RB, Punt C, Homberg J, Toussaint MJM, Kisjes R, Korporaal SJA, Akkerman JWN, Cuppen E, de Bruin A. Deletion of the serotonin transporter in rats disturbs serotonin homeostasis without impairing liver regeneration. Am J Physiol Gastrointest Liver Physiol 2009; 296:G963-8. [PMID: 19246633 DOI: 10.1152/ajpgi.90709.2008] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The serotonin transporter is implicated in the uptake of the vasoconstrictor serotonin from the circulation into the platelets, where 95% of all blood serotonin is stored and released in response to vascular injury. In vivo studies indicated that platelet-derived serotonin mediates liver regeneration after partial hepatectomy. We have recently generated serotonin transporter knockout rats and demonstrated that their platelets were almost completely depleted of serotonin. Here we show that these rats exhibit impaired hemostasis and contain about 1-6% of wild-type serotonin levels in the blood. Despite the marked reduction of serotonin levels in blood and platelets, efficient liver regeneration and collagen-induced platelet aggregation occur in rats lacking the serotonin transporter. These results provide evidence that liver regeneration is not dependent on the release of serotonin from platelets. Our findings indicate that very low levels of serotonin in blood are sufficient for liver regeneration.
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Affiliation(s)
- Ramadhan B Matondo
- Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3508 TD Utrecht, The Netherlands
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34
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Neels OC, Koopmans KP, Jager PL, Vercauteren L, van Waarde A, Doorduin J, Timmer-Bosscha H, Brouwers AH, de Vries EG, Dierckx RA, Kema IP, Elsinga PH. Manipulation of [11C]-5-Hydroxytryptophan and 6-[18F]Fluoro-3,4-Dihydroxy-l-Phenylalanine Accumulation in Neuroendocrine Tumor Cells. Cancer Res 2008; 68:7183-90. [DOI: 10.1158/0008-5472.can-08-0095] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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35
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Geiger BM, Behr GG, Frank LE, Caldera-Siu AD, Beinfeld MC, Kokkotou EG, Pothos EN. Evidence for defective mesolimbic dopamine exocytosis in obesity-prone rats. FASEB J 2008; 22:2740-6. [PMID: 18477764 DOI: 10.1096/fj.08-110759] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The association between dietary obesity and mesolimbic systems that regulate hedonic aspects of feeding is currently unresolved. In the present study, we examined differences in baseline and stimulated central dopamine levels in obesity-prone (OP) and obesity-resistant (OR) rats. OP rats were hyperphagic and showed a 20% weight gain over OR rats at wk 15 of age, when fed a standard chow diet. This phenotype was associated with a 50% reduction in basal extracellular dopamine, as measured by a microdialysis probe in the nucleus accumbens, a projection site of the mesolimbic dopamine system that has been implicated in food reward. Similar defects were also observed in younger animals (4 wk old). In electrophysiology studies, electrically evoked dopamine release in slice preparations was significantly attenuated in OP rats, not only in the nucleus accumbens but also in additional terminal sites of dopamine neurons such as the accumbens shell, dorsal striatum, and medial prefrontal cortex, suggesting that there may be a widespread dysfunction in mechanisms regulating dopamine release in this obesity model. Moreover, dopamine impairment in OP rats was apparent at birth and associated with changes in expression of several factors regulating dopamine synthesis and release: vesicular monoamine transporter-2, tyrosine hydroxylase, dopamine transporter, and dopamine receptor-2 short-form. Taken together, these results suggest that an attenuated central dopamine system would reduce the hedonic response associated with feeding and induce compensatory hyperphagia, leading to obesity.
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Affiliation(s)
- Brenda M Geiger
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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36
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Vesicular monoamine transporter 2 regulates the sensitivity of rat dopaminergic neurons to disturbed cytosolic dopamine levels. Brain Res 2007; 1185:18-32. [PMID: 18028884 DOI: 10.1016/j.brainres.2007.09.028] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 09/04/2007] [Accepted: 09/13/2007] [Indexed: 11/22/2022]
Abstract
An abnormal accumulation of cytosolic dopamine resulting in reactive oxygen species and dopamine-quinone products may play an important role in the rather selective degeneration of substantia nigra pars compacta (SNc) dopaminergic neurons in Parkinson's disease. The neuronal-specific vesicular monoamine transporter (VMAT2), responsible for uptake of dopamine into vesicles, has been shown to play a central role both in intracellular dopamine homeostasis and sequestration of dopaminergic neurotoxins. Direct or indirect enhancement of VMAT2 activity could therefore have neuroprotective effects by decreasing cytosolic dopamine levels. Here, we demonstrate that transfection of VMAT2 in the dopaminergic cell line, PC12, increases intracellular dopamine content, augments potassium-induced dopamine release and attenuates cell death induced by the cytosolic dopamine enhancer, methamphetamine, suggesting an enhancement in vesicular dopamine storage. In rat ventral mesencephalic cultures highly enriched for dopaminergic neurons, lentiviral delivery of recombinant VMAT2 using a neuronal-specific promoter also resulted in elevated intracellular dopamine content and neurotransmitter release after depolarization. The opposite was seen after downregulation of VMAT2 using virally delivered shRNAs. Furthermore, using this VMAT2 knockdown model, we are the first to report a direct link between enhanced cytoplasmic dopamine levels, measured following mild permeabilization of the plasma membrane using digitonin, and neurite degeneration in primary dopaminergic neurons. In conclusion, our data support the hypothesis that an increase in vesicular sequestration of dopamine by modulation of VMAT2 activity could restore neuronal function and enhance dopaminergic cell survival in conditions of dysregulated dopamine homeostasis such as Parkinson's disease.
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Abstract
Changes in the response to release of a single synaptic vesicle have generally been attributed to postsynaptic modification of receptor sensitivity, but considerable evidence now demonstrates that alterations in vesicle filling also contribute to changes in quantal size. Receptors are not saturated at many synapses, and changes in the amount of transmitter per vesicle contribute to the physiological regulation of release. On the other hand, the presynaptic factors that determine quantal size remain poorly understood. Aside from regulation of the fusion pore, these mechanisms fall into two general categories: those that affect the accumulation of transmitter inside a vesicle and those that affect vesicle size. This review will summarize current understanding of the neurotransmitter cycle and indicate basic, unanswered questions about the presynaptic regulation of quantal size.
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Affiliation(s)
- Robert H Edwards
- Department of Neurology and Physiology, UCSF School of Medicine, San Francisco, CA 94158-2517, USA.
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38
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Brunk I, Höltje M, von Jagow B, Winter S, Sternberg J, Blex C, Pahner I, Ahnert-Hilger G. Regulation of vesicular monoamine and glutamate transporters by vesicle-associated trimeric G proteins: new jobs for long-known signal transduction molecules. Handb Exp Pharmacol 2007:305-25. [PMID: 16722242 DOI: 10.1007/3-540-29784-7_15] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neurotransmitters of neurons and neuroendocrine cells are concentrated first in the cytosol and then in either small synaptic vesicles ofpresynaptic terminals or in secretory vesicles by the activity of specific transporters of the plasma and the vesicular membrane, respectively. In the central nervous system the postsynaptic response depends--amongst other parameters-on the amount of neurotransmitter stored in a given vesicle. Neurotransmitter packets (quanta) vary over a wide range which may be also due to a regulation of vesicular neurotransmitter filling. Vesicular filling is regulated by the availability of transmitter molecules in the cytoplasm, the amount of transporter molecules and an electrochemical proton-mediated gradient over the vesicular membrane. In addition, it is modulated by vesicle-associated heterotrimeric G proteins, Galphao2 and Galphaq. Galphao2 and Galphaq regulate vesicular monoamine transporter (VMAT) activities in brain and platelets, respectively. Galphao2 also regulates vesicular glutamate transporter (VGLUT) activity by changing its chloride dependence. It appears that the vesicular content activates the G protein, suggesting a signal transduction from the luminal site which might be mediated by a vesicular G protein-coupled receptor or as an alternative possibility by the transporter itself. Thus, G proteins control transmitter storage and thereby probablylink the regulation of the vesicular content to intracellular signal cascades.
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Affiliation(s)
- I Brunk
- AG Funktionelle Zellbiologie, Institut für Integrative Neuroanatomie, Centrum für Anatomie, Charité, Universitätsmedizin Berlin, Berlin, Germany
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39
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Bohnen NI, Albin RL, Koeppe RA, Wernette KA, Kilbourn MR, Minoshima S, Frey KA. Positron emission tomography of monoaminergic vesicular binding in aging and Parkinson disease. J Cereb Blood Flow Metab 2006; 26:1198-212. [PMID: 16421508 DOI: 10.1038/sj.jcbfm.9600276] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The type-2 vesicular monoamine transporter (VMAT2) might serve as an objective biomarker of Parkinson disease (PD) severity. Thirty-one subjects with early-stage PD and 75 normal subjects underwent continuous intravenous infusion of (+)-[(11)C]dihydrotetrabenazine (DTBZ) and positron emission tomography (PET) imaging to estimate the striatal VMAT2 binding site density with equilibrium tracer modeling. Parkinson disease patients were evaluated clinically in the practically defined 'off' state with the Unified Parkinson Disease Rating Scale (UPDRS), the Hoehn and Yahr Scale (HY), and the Schwab and England Activities of Daily Living Scale (SE). In normal subjects there was age-related decline in striatal DTBZ binding, approximating 0.5% per year. In PD subjects, specific DTBZ binding was reduced in the caudate nucleus (CD; -44%), anterior putamen (-68%), and posterior putamen (PP; -77%). The PP-to-CD ratio of binding was reduced significantly in PD subjects. Dihydrotetrabenazine binding was also reduced by approximately 50% in the PD substantia nigra. Striatal binding reductions correlated significantly with PD duration and SE scores, but not with HY stage or with UPDRS motor subscale (UPDRS(III)) scores. Striatal and midbrain DTBZ binding was asymmetric in PD subjects, with greatest reductions contralateral to the most clinically affected limbs. There was significant correlation between asymmetry of DTBZ binding and clinical asymmetry measured with the UPDRS(III). In HY stage 1 and 1.5 subjects (n=16), PP DTBZ binding contralateral to the clinically unaffected body side was reduced by 73%, indicating substantial preclinical nigrostriatal pathology in PD. We conclude that (+)-[(11)C]DTBZ-PET imaging displays many properties necessary of a PD biomarker.
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Affiliation(s)
- Nicolaas I Bohnen
- Department of Radiology, Division of Nuclear Medicine, The University of Michigan Medical School, Ann Arbor, 48109-0028, USA
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40
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Brunk I, Blex C, Rachakonda S, Höltje M, Winter S, Pahner I, Walther DJ, Ahnert-Hilger G. The first luminal domain of vesicular monoamine transporters mediates G-protein-dependent regulation of transmitter uptake. J Biol Chem 2006; 281:33373-85. [PMID: 16926160 DOI: 10.1074/jbc.m603204200] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activity of vesicular monoamine transporters (VMATs) is down-regulated by the G-protein alpha-subunits of G(o2) and G(q), but the signaling pathways are not known. We show here that no such regulation is observed when VMAT1 or VMAT2 are expressed in Chinese hamster ovary (CHO) cells. However, when the intracellular compartments of VMAT-expressing CHO cells are preloaded with different monoamines, transport becomes susceptible to G-protein-dependent regulation, with differences between the two transporter isoforms. Epinephrine induces G-protein-mediated inhibition of transmitter uptake in CHOVMAT1 cells but prevents inhibition induced by dopamine in CHOVMAT2 cells. Epinephrine also antagonizes G-protein-mediated inhibition of monoamine uptake by VMAT2 expressing platelets or synaptic vesicles. In CHOVMAT2 cells G-protein-mediated inhibition of monoamine uptake can be induced by 5-hydroxytryptamine (serotonin) 1B receptor agonists, whereas alpha1 receptor agonists modulate uptake into CHOVMAT1 cells. Accordingly, 5-hydroxytryptamine 1B receptor antagonists prevent G-protein-mediated inhibition of uptake in partially filled platelets and synaptic vesicles expressing VMAT2. CHO cells expressing VMAT mutants with a shortened first vesicular loop transport monoamines. However, no or a reduced G-protein regulation of uptake can be initiated. In conclusion, vesicular content is involved in the activation of vesicle associated G-proteins via a structure sensing the luminal monoamine content. The first luminal loop of VMATs may represent a G-protein-coupled receptor that adapts vesicular filling.
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Affiliation(s)
- Irene Brunk
- Functional Cell Biology, Centre for Anatomy, Charité-Universitätsmedizin Berlin, Philippstrasse 12, D-10115 Berlin, Germany
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41
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Peter JU, Alenina N, Bader M, Walther DJ. Development of antithrombotic miniribozymes that target peripheral tryptophan hydroxylase. Mol Cell Biochem 2006; 295:205-15. [PMID: 16924415 DOI: 10.1007/s11010-006-9290-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2006] [Accepted: 07/24/2006] [Indexed: 01/01/2023]
Abstract
Serotonin is not only a neurotransmitter in the central nervous system, but also a ubiquitous hormone in the periphery involved in vasoconstriction and platelet function. Tryptophan hydroxylase is the rate-limiting enzyme in serotonin biosynthesis. By gene targeting, we have shown that serotonin is synthesized independently by two different tryptophan hydroxylase isoenzymes in peripheral tissues and neurons and identified a neuronal tryptophan hydroxylase isoform. Mice deficient in peripheral tryptophan hydroxylase (TPH1) and serotonin exhibit a reduced risk of thrombosis and thromboembolism. Therefore, we designed several antitph1 hammerhead miniribozymes and tested their cleavage activity against short synthetic Tph1 RNA substrates. In vitro cleavage studies demonstrated site-specific cleavage of Tph1 mRNA that was dependent on substrate/miniribozyme ratio and duration of exposure to miniribozyme. Interestingly, we detected different in vitro cleavage rates after we had cloned the miniribozymes into tRNA expression constructs, and found one with a high cleavage rate. We also demonstrated that this active tRNA-miniribozyme chimera is capable of selectively cleaving native Tph1 mRNA in vivo, with concomitant downregulation of the serotonin biosynthesis. Therefore, this Tph1-specific miniribozyme may provide a novel and effective form of gene therapy that may be applicable to a variety of thrombotic diseases.
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Affiliation(s)
- Jens-Uwe Peter
- Max-Planck-Institute for Molecular Genetics, Ihnestrasse 73, D-14195, Berlin, Germany
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42
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Schwartz K, Herman I, Peer G, Weizman A, Rehavi M. Elevated platelet vesicular monoamine transporter 2 in former heroin addicts maintained on methadone. J Neural Transm (Vienna) 2006; 114:281-4. [PMID: 16855915 DOI: 10.1007/s00702-006-0527-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2006] [Accepted: 05/08/2006] [Indexed: 11/25/2022]
Abstract
The brain vesicular monoamine transporter (VMAT2) is essential for neuronal monoamine storage and regulation of monoaminergic neurotransmission. We demonstrated previously a high degree of similarity between the pharmacodynamic characteristics of platelet and brain VMAT2. Opioids induce increase of dopamine release in limbic structures. In the present study we assessed the VMAT2 pharmacodynamic characteristics using high affinity [(3)H]dihydrotetrabenazine (TBZOH) binding to platelets of former male heroin addicts maintained on methadone (n = 12) compared to age-matched healthy controls (n = 13). A significant increase (19%, p < 0.05) in platelet VMAT2 density (Bmax) was observed in the methadone treated patients compared to controls. There was no significant difference in the affinity of [(3)H]TBZOH to its platelet binding site. The increased VMAT2 density may reflect a compensatory attempt to prevent vesicular depletion due to chronic methadone exposure.
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Affiliation(s)
- K Schwartz
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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Winter S, Brunk I, Walther DJ, Höltje M, Jiang M, Peter JU, Takamori S, Jahn R, Birnbaumer L, Ahnert-Hilger G. Galphao2 regulates vesicular glutamate transporter activity by changing its chloride dependence. J Neurosci 2006; 25:4672-80. [PMID: 15872115 PMCID: PMC6725018 DOI: 10.1523/jneurosci.0549-05.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Classical neurotransmitters, including monoamines, acetylcholine, glutamate, GABA, and glycine, are loaded into synaptic vesicles by means of specific transporters. Vesicular monoamine transporters are under negative regulation by alpha subunits of trimeric G-proteins, including Galpha(o2) and Galpha(q). Furthermore, glutamate uptake, mediated by vesicular glutamate transporters (VGLUTs), is decreased by the nonhydrolysable GTP-analog guanylylimidodiphosphate. Using mutant mice lacking various Galpha subunits, including Galpha(o1), Galpha(o2), Galpha(q), and Galpha11, and a Galpha(o2)-specific monoclonal antibody, we now show that VGLUTs are exclusively regulated by Galpha(o2). G-protein activation does not affect the electrochemical proton gradient serving as driving force for neurotransmitter uptake; rather, Galpha(o2) exerts its action by specifically affecting the chloride dependence of VGLUTs. All VGLUTs show maximal activity at approximately 5 mm chloride. Activated Galpha(o2) shifts this maximum to lower chloride concentrations. In contrast, glutamate uptake by vesicles isolated from Galpha(o2-/-) mice have completely lost chloride activation. Thus, Galpha(o2) acts on a putative regulatory chloride binding domain that appears to modulate transport activity of vesicular glutamate transporters.
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Affiliation(s)
- Sandra Winter
- AG Funktionelle Zellbiologie, Centrum für Anatomie, Charité Universitätsmedizin Berlin, D-10115 Berlin, Germany
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44
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Chang HY, Grygoruk A, Brooks ES, Ackerson LC, Maidment NT, Bainton RJ, Krantz DE. Overexpression of the Drosophila vesicular monoamine transporter increases motor activity and courtship but decreases the behavioral response to cocaine. Mol Psychiatry 2006; 11:99-113. [PMID: 16189511 DOI: 10.1038/sj.mp.4001742] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Aminergic signaling pathways have been implicated in a variety of neuropsychiatric illnesses, but the mechanisms by which these pathways influence complex behavior remain obscure. Vesicular monoamine transporters (VMATs) have been shown to regulate the amount of monoamine neurotransmitter that is stored and released from synaptic vesicles in mammalian systems, and an increase in their expression has been observed in bipolar patients. The model organism Drosophila melanogaster provides a powerful, but underutilized genetic system for studying how dopamine (DA) and serotonin (5HT) may influence behavior. We show that a Drosophila isoform of VMAT (DVMAT-A) is expressed in both dopaminergic and serotonergic neurons in the adult Drosophila brain. Overexpression of DVMAT-A in these cells potentiates stereotypic grooming behaviors and locomotion and can be reversed by reserpine, which blocks DVMAT activity, and haloperidol, a DA receptor antagonist. We also observe a prolongation of courtship behavior, a decrease in successful mating and a decrease in fertility, suggesting a role for aminergic circuits in the modulation of sexual behaviors. Finally, we find that DMVAT-A overexpression decreases the fly's sensitivity to cocaine, suggesting that the synaptic machinery responsible for this behavior may be downregulated. DVMAT transgenes may be targeted to additional neuronal pathways using standard Drosophila techniques, and our results provide a novel paradigm to study the mechanisms by which monoamines regulate complex behaviors relevant to neuropsychiatric illness.
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Affiliation(s)
- H-Y Chang
- Department of Psychiatry and Biobehavioral Sciences, Gonda (Goldschmied) Center for Genetic and Neuroscience Research, Geffen School of Medicine-UCLA, University of California at Los Angeles, 695 Charles Young Drive, Los Angeles, CA 90095-1761, USA
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45
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Greer CL, Grygoruk A, Patton DE, Ley B, Romero-Calderon R, Chang HY, Houshyar R, Bainton RJ, Diantonio A, Krantz DE. A splice variant of the Drosophila vesicular monoamine transporter contains a conserved trafficking domain and functions in the storage of dopamine, serotonin, and octopamine. ACTA ACUST UNITED AC 2005; 64:239-58. [PMID: 15849736 DOI: 10.1002/neu.20146] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Vesicular monoamine transporters (VMATs) mediate the transport of dopamine (DA), serotonin (5HT), and other monoamines into secretory vesicles. The regulation of mammalian VMAT and the related vesicular acetylcholine transporter (VAChT) has been proposed to involve membrane trafficking, but the mechanisms remain unclear. To facilitate a genetic analysis of vesicular transporter function and regulation, we have cloned the Drosophila homolog of the vesicular monoamine transporter (dVMAT). We identify two mRNA splice variants (DVMAT-A and B) that differ at their C-terminus, the domain responsible for endocytosis of mammalian VMAT and VAChT. DVMAT-A contains trafficking motifs conserved in mammals but not C. elegans, and internalization assays indicate that the DVMAT-A C-terminus is involved in endocytosis. DVMAT-B contains a divergent C-terminal domain and is less efficiently internalized from the cell surface. Using in vitro transport assays, we show that DVMAT-A recognizes DA, 5HT, octopamine, tyramine, and histamine as substrates, and similar to mammalian VMAT homologs, is inhibited by the drug reserpine and the environmental toxins 2,2,4,5,6-pentachlorobiphenyl and heptachlor. We have developed a specific antiserum to DVMAT-A, and find that it localizes to dopaminergic and serotonergic neurons as well as octopaminergic, type II terminals at the neuromuscular junction. Surprisingly, DVMAT-A is co-expressed at type II terminals with the Drosophila vesicular glutamate transporter. Our data suggest that DVMAT-A functions as a vesicular transporter for DA, 5HT, and octopamine in vivo, and will provide a powerful invertebrate model for the study of transporter trafficking and regulation.
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Affiliation(s)
- Christina L Greer
- Department of Psychiatry and Biobehavioral Sciences, The David Geffen School of Medicine at UCLA, Gonda (Goldschmied) Center for Genetic and Neuroscience Research, 695 Charles Young Drive, Los Angeles, California 90095-1761, USA
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46
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Anlauf M, Schäfer MKH, Schwark T, von Wurmb-Schwark N, Brand V, Sipos B, Horny HP, Parwaresch R, Hartschuh W, Eiden LE, Klöppel G, Weihe E. Vesicular monoamine transporter 2 (VMAT2) expression in hematopoietic cells and in patients with systemic mastocytosis. J Histochem Cytochem 2005; 54:201-13. [PMID: 16116033 DOI: 10.1369/jhc.5a6739.2005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Uptake of monoamines into secretory granules is mediated by the vesicular monoamine transporters VMAT1 and VMAT2. In this study, we analyzed their expression in inflammatory and hematopoietic cells and in patients suffering from systemic mastocytosis (SM) and chronic myelogenous leukemia (CML). Normal human and monkey tissue specimens and tissues from patients suffering from SM and CML were analyzed by means of immunohistochemistry, radioactive in situ hybridization, real time RT-PCR, double fluorescence confocal laser scanning microscopy, and immunoelectron microscopy. In normal tissue specimens, VMAT2, but not VMAT1, was expressed in mast cells, megakaryocytes, thrombocytes, basophil granulocytes, and cutaneous Langerhans cells. Further hematopoietic and lymphoid cells showed no expression of VMATs. VMAT2 was expressed in all types of SM, as indicated by coexpression with the mast cell marker tryptase. In CML, VMAT2 expression was retained in neoplastic megakaryocytes and basophil granulocytes. In conclusion, the identification of VMAT2 in mast cells, megakaryocytes, thrombocytes, basophil granulocytes, and cutaneous Langerhans cells provides evidence that these cells possess molecular mechanisms for monoamine storage and handling. VMAT2 identifies normal and neoplastic mast cells, megakaryocytes, and basophil granulocytes and may therefore become a valuable tool for the diagnosis of mastocytosis and malignant systemic diseases involving megakaryocytes and basophil granulocytes.
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MESH Headings
- Animals
- Basophils/metabolism
- Biomarkers, Tumor/biosynthesis
- Blood Platelets/metabolism
- Bone Marrow Cells/metabolism
- Hematopoiesis
- Humans
- Immunohistochemistry
- In Situ Hybridization
- Langerhans Cells/metabolism
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/blood
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/metabolism
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology
- Macaca mulatta
- Mast Cells/metabolism
- Mastocytosis, Systemic/blood
- Mastocytosis, Systemic/metabolism
- Mastocytosis, Systemic/pathology
- Megakaryocytes/metabolism
- Microscopy, Confocal
- Microscopy, Immunoelectron
- Organ Specificity
- RNA, Messenger/biosynthesis
- Reverse Transcriptase Polymerase Chain Reaction
- Vesicular Monoamine Transport Proteins/biosynthesis
- Vesicular Monoamine Transport Proteins/genetics
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Affiliation(s)
- Martin Anlauf
- Department of Pathology, University of Kiel, Michaelisstr. 11, 24105 Kiel, Germany.
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Ahnert-Hilger G, Höltje M, Pahner I, Winter S, Brunk I. Regulation of vesicular neurotransmitter transporters. Rev Physiol Biochem Pharmacol 2004; 150:140-60. [PMID: 14517724 DOI: 10.1007/s10254-003-0020-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neurotransmitters are key molecules of neurotransmission. They are concentrated first in the cytosol and then in small synaptic vesicles of presynaptic terminals by the activity of specific neurotransmitter transporters of the plasma and the vesicular membrane, respectively. It has been shown that postsynaptic responses to single neurotransmitter packets vary over a wide range, which may be due to a regulation of vesicular neurotransmitter filling. Vesicular filling depends on the availability of transmitter molecules in the cytoplasm and the active transport into secretory vesicles relying on a proton gradient. In addition, it is modulated by vesicle-associated heterotrimeric G proteins, Galphao2 and Galphaq, which regulate VMAT activities in brain and platelets, respectively, and may also be involved in the regulation of VGLUTs. It appears that the vesicular content activates the G protein, suggesting a signal transduction form the luminal site which might be mediated by a vesicular G-protein coupled receptor or, as an alternative, possibly by the transporter itself. These novel functions of G proteins in the control of transmitter storage may link regulation of the vesicular content to intracellular signal cascades.
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Affiliation(s)
- G Ahnert-Hilger
- Institut für Anatomie und Neurowissenschaftliches Zentrum der Charité, Humboldt-Universität zu Berlin, Philippstr. 12, 10115 Berlin, Germany.
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48
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Walther DJ, Peter JU, Winter S, Höltje M, Paulmann N, Grohmann M, Vowinckel J, Alamo-Bethencourt V, Wilhelm CS, Ahnert-Hilger G, Bader M. Serotonylation of small GTPases is a signal transduction pathway that triggers platelet alpha-granule release. Cell 2004; 115:851-62. [PMID: 14697203 DOI: 10.1016/s0092-8674(03)01014-6] [Citation(s) in RCA: 348] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Serotonin is a neurotransmitter in the central nervous system. In the periphery, serotonin functions as a ubiquitous hormone involved in vasoconstriction and platelet function. Serotonin is synthesized independently in peripheral tissues and neurons by two different rate-limiting tryptophan hydroxylase (TPH) isoenzymes. Here, we show that mice selectively deficient in peripheral TPH and serotonin exhibit impaired hemostasis, resulting in a reduced risk of thrombosis and thromboembolism, although the ultrastructure of the platelets is not affected. While the aggregation of serotonin-deficient platelets in vitro is apparently normal, their adhesion in vivo is reduced due to a blunted secretion of adhesive alpha-granular proteins. In elucidating the mechanism further, we demonstrate that serotonin is transamidated to small GTPases by transglutaminases during activation and aggregation of platelets, rendering these GTPases constitutively active. Our data provides evidence for a receptor-independent signaling mechanism, termed herein as "serotonylation," which leads to alpha-granule exocytosis from platelets.
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Affiliation(s)
- Diego J Walther
- Max-Planck-Institute for Molecular Genetics, Ihnestrasse 73, D-14195 Berlin, Germany.
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