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Sarver DC, Xu C, Velez LM, Aja S, Jaffe AE, Seldin MM, Reeves RH, Wong GW. Dysregulated systemic metabolism in a Down syndrome mouse model. Mol Metab 2023; 68:101666. [PMID: 36587842 PMCID: PMC9841171 DOI: 10.1016/j.molmet.2022.101666] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 12/14/2022] [Accepted: 12/26/2022] [Indexed: 12/30/2022] Open
Abstract
OBJECTIVE Trisomy 21 is one of the most complex genetic perturbations compatible with postnatal survival. Dosage imbalance arising from the triplication of genes on human chromosome 21 (Hsa21) affects multiple organ systems. Much of Down syndrome (DS) research, however, has focused on addressing how aneuploidy dysregulates CNS function leading to cognitive deficit. Although obesity, diabetes, and associated sequelae such as fatty liver and dyslipidemia are well documented in the DS population, only limited studies have been conducted to determine how gene dosage imbalance affects whole-body metabolism. Here, we conduct a comprehensive and systematic analysis of key metabolic parameters across different physiological states in the Ts65Dn trisomic mouse model of DS. METHODS Ts65Dn mice and euploid littermates were subjected to comprehensive metabolic phenotyping under basal (chow-fed) state and the pathophysiological state of obesity induced by a high-fat diet (HFD). RNA sequencing of liver, skeletal muscle, and two major fat depots were conducted to determine the impact of aneuploidy on tissue transcriptome. Pathway enrichments, gene-centrality, and key driver estimates were performed to provide insights into tissue autonomous and non-autonomous mechanisms contributing to the dysregulation of systemic metabolism. RESULTS Under the basal state, chow-fed Ts65Dn mice of both sexes had elevated locomotor activity and energy expenditure, reduced fasting serum cholesterol levels, and mild glucose intolerance. Sexually dimorphic deterioration in metabolic homeostasis became apparent when mice were challenged with a high-fat diet. While obese Ts65Dn mice of both sexes exhibited dyslipidemia, male mice also showed impaired systemic insulin sensitivity, reduced mitochondrial activity, and elevated fibrotic and inflammatory gene signatures in the liver and adipose tissue. Systems-level analysis highlighted conserved pathways and potential endocrine drivers of adipose-liver crosstalk that contribute to dysregulated glucose and lipid metabolism. CONCLUSIONS A combined alteration in the expression of trisomic and disomic genes in peripheral tissues contribute to metabolic dysregulations in Ts65Dn mice. These data lay the groundwork for understanding the impact of aneuploidy on in vivo metabolism.
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Affiliation(s)
- Dylan C Sarver
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Cheng Xu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Leandro M Velez
- Department of Biological Chemistry, University of California, Irvine, Irvine, USA; Center for Epigenetics and Metabolism, University of California Irvine, Irvine, USA
| | - Susan Aja
- Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Andrew E Jaffe
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; The Lieber Institute for Brain Development, Baltimore, MD, USA; Center for Computational Biology, Johns Hopkins University, Baltimore, MD, USA; Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Marcus M Seldin
- Department of Biological Chemistry, University of California, Irvine, Irvine, USA; Center for Epigenetics and Metabolism, University of California Irvine, Irvine, USA
| | - Roger H Reeves
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - G William Wong
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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2
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Wong H, Buck JM, Borski C, Pafford JT, Keller BN, Milstead RA, Hanson JL, Stitzel JA, Hoeffer CA. RCAN1 knockout and overexpression recapitulate an ensemble of rest-activity and circadian disruptions characteristic of Down syndrome, Alzheimer's disease, and normative aging. J Neurodev Disord 2022; 14:33. [PMID: 35610565 PMCID: PMC9128232 DOI: 10.1186/s11689-022-09444-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 05/12/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Regulator of calcineurin 1 (RCAN1) is overexpressed in Down syndrome (DS), but RCAN1 levels are also increased in Alzheimer's disease (AD) and normal aging. AD is highly comorbid among individuals with DS and is characterized in part by progressive neurodegeneration that resembles accelerated aging. Importantly, abnormal RCAN1 levels have been demonstrated to promote memory deficits and pathophysiology that appear symptomatic of DS, AD, and aging. Anomalous diurnal rest-activity patterns and circadian rhythm disruptions are also common in DS, AD, and aging and have been implicated in facilitating age-related cognitive decline and AD progression. However, no prior studies have assessed whether RCAN1 dysregulation may also promote the age-associated alteration of rest-activity profiles and circadian rhythms, which could in turn contribute to neurodegeneration in DS, AD, and aging. METHODS The present study examined the impacts of RCAN1 deficiency and overexpression on the photic entrainment, circadian periodicity, intensity and distribution, diurnal patterning, and circadian rhythmicity of wheel running in young (3-6 months old) and aged (9-14 months old) mice of both sexes. RESULTS We found that daily RCAN1 levels in the hippocampus and suprachiasmatic nucleus (SCN) of light-entrained young mice are generally constant and that balanced RCAN1 expression is necessary for normal circadian locomotor activity rhythms. While the light-entrained diurnal period was unaltered, RCAN1-null and RCAN1-overexpressing mice displayed lengthened endogenous (free-running) circadian periods like mouse models of AD and aging. In light-entrained young mice, RCAN1 deficiency and overexpression also recapitulated the general hypoactivity, diurnal rest-wake pattern fragmentation, and attenuated amplitudes of circadian activity rhythms reported in DS, preclinical and clinical AD, healthily aging individuals, and rodent models thereof. Under constant darkness, RCAN1-null and RCAN1-overexpressing mice displayed altered locomotor behavior indicating circadian clock dysfunction. Using the Dp(16)1Yey/+ (Dp16) mouse model for DS, which expresses three copies of Rcan1, we found reduced wheel running activity and rhythmicity in both light-entrained and free-running young Dp16 mice like young RCAN1-overexpressing mice. Critically, these diurnal and circadian deficits were rescued in part or entirely by restoring Rcan1 to two copies in Dp16 mice. We also found that RCAN1 deficiency but not RCAN1 overexpression altered protein levels of the clock gene Bmal1 in the SCN. CONCLUSIONS Collectively, this study's findings suggest that both loss and aberrant gain of RCAN1 precipitate anomalous light-entrained diurnal and circadian activity patterns emblematic of DS, AD, and possibly aging.
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Affiliation(s)
- Helen Wong
- Institute for Behavioral Genetics, University of Colorado Boulder, 1480 30th Street, Boulder, CO, 80309-0447, USA
- Department of Integrative Physiology, University of Colorado, Boulder, CO, 80303, USA
| | - Jordan M Buck
- Institute for Behavioral Genetics, University of Colorado Boulder, 1480 30th Street, Boulder, CO, 80309-0447, USA
- Department of Integrative Physiology, University of Colorado, Boulder, CO, 80303, USA
| | - Curtis Borski
- Institute for Behavioral Genetics, University of Colorado Boulder, 1480 30th Street, Boulder, CO, 80309-0447, USA
- Department of Integrative Physiology, University of Colorado, Boulder, CO, 80303, USA
| | - Jessica T Pafford
- Department of Integrative Physiology, University of Colorado, Boulder, CO, 80303, USA
| | - Bailey N Keller
- Institute for Behavioral Genetics, University of Colorado Boulder, 1480 30th Street, Boulder, CO, 80309-0447, USA
| | - Ryan A Milstead
- Institute for Behavioral Genetics, University of Colorado Boulder, 1480 30th Street, Boulder, CO, 80309-0447, USA
- Department of Integrative Physiology, University of Colorado, Boulder, CO, 80303, USA
| | - Jessica L Hanson
- Institute for Behavioral Genetics, University of Colorado Boulder, 1480 30th Street, Boulder, CO, 80309-0447, USA
- Department of Integrative Physiology, University of Colorado, Boulder, CO, 80303, USA
| | - Jerry A Stitzel
- Institute for Behavioral Genetics, University of Colorado Boulder, 1480 30th Street, Boulder, CO, 80309-0447, USA
- Department of Integrative Physiology, University of Colorado, Boulder, CO, 80303, USA
| | - Charles A Hoeffer
- Institute for Behavioral Genetics, University of Colorado Boulder, 1480 30th Street, Boulder, CO, 80309-0447, USA.
- Department of Integrative Physiology, University of Colorado, Boulder, CO, 80303, USA.
- Linda Crnic Institute, Anschutz Medical Campus, Aurora, CO, 80045, USA.
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Kim SS, Lee EH, Shin JH, Seo SR. MAP kinase/ERK kinase 1 (MEK1) phosphorylates regulator of calcineurin 1 (RCAN1) to regulate neuronal differentiation. J Cell Physiol 2021; 237:1406-1417. [PMID: 34647615 DOI: 10.1002/jcp.30609] [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: 05/25/2021] [Revised: 09/27/2021] [Accepted: 10/04/2021] [Indexed: 11/08/2022]
Abstract
Regulator of calcineurin 1 (RCAN1) is located close to the Down syndrome critical region (DSCR) on human chromosome 21 and is related to the Down syndrome (DS) phenotype. To identify a novel binding partner of RCAN1, we performed yeast two-hybrid screening and identified mitogen-activated protein (MAP) kinase/extracellular signal-regulated kinase (ERK) kinase 1 (MEK1) as a partner. MEK1 was able to bind and phosphorylate RCAN1 in vitro and in vivo. MEK1-dependent RCAN1 phosphorylation caused an increase in RCAN1 expression by increasing the protein half-life. Nerve growth factor (NGF)-dependent activation of the MEK1 pathway consistently induced RCAN1 expression. Moreover, we found that RCAN1 overexpression inhibited NGF-induced neurite outgrowth and expression of neuronal marker genes, such as growth cone-associated protein 43 (GAP43) and synapsin I, via inhibition of MEK1-ERK1/2 pathways. Our findings provide evidence that MEK1-dependent RCAN1 phosphorylation acts as an important molecular mechanism in the control of neuronal differentiation.
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Affiliation(s)
- Seon Sook Kim
- Department of Molecular Bioscience, Kangwon National University, Chuncheon, Republic of Korea
| | - Eun Hye Lee
- Department of Molecular Bioscience, Kangwon National University, Chuncheon, Republic of Korea
| | - Jin Hak Shin
- Department of Molecular Bioscience, Kangwon National University, Chuncheon, Republic of Korea
| | - Su Ryeon Seo
- Department of Molecular Bioscience, Kangwon National University, Chuncheon, Republic of Korea
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Wang Y, Wang Q, Chen J, Yao LH, Tang N, Jiang ZX, Luo Y. Protective Effect of Hydroxysafflor Yellow A against Chronic Mild Stress-induced Memory Impairments by Suppressing Tau Phosphorylation in Mice. Curr Med Sci 2021; 41:555-564. [PMID: 34129201 DOI: 10.1007/s11596-021-2369-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Accepted: 09/10/2020] [Indexed: 12/19/2022]
Abstract
Chronic stress plays a critical role in the etiology of sporadic Alzheimer's disease (AD). However, there are currently no effective drugs that can target chronic stress to prevent AD. In this study, we explored the neuroprotective effect of hydroxysafflor yellow A (HSYA) against chronic mild stress (CMS)-induced memory impairments in mice and the underlying mechanism. The Morris water maze test showed that HSYA significantly reduced CMS-induced learning and memory impairments in mice. HSYA increased the expression of brain-derived neurotrophic factor (BDNF) and activated downstream tropomyosin-related kinase B (TrkB) and phosphatidylinositol 3-kinase (PI3K)/protein kinase B(Akt)/mammalian target of rapamycin (mTOR) signaling. HSYA decreased the expression of regulator of calcineurin 1-1L (RCAN1-1L) that could promote the activity of glycogen synthase kinase-3β (GSK-3β). HSYA also attenuated tau phosphorylation by inhibiting the activity of GSK-3β and cyclin-dependent kinase-5 (Cdk5). Our data indicated that HSYA has protective effects against CMS-induced BDNF downregulation, tau phosphorylation and memory impairments. HSYA may be a promising therapeutic candidate for AD by targeting chronic stress.
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Affiliation(s)
- Ying Wang
- Department of Neurology, The First Hospital of Lanzhou University, Lanzhou, 730000, China
| | - Qiang Wang
- Department of Neurology, The First Hospital of Lanzhou University, Lanzhou, 730000, China
| | - Jun Chen
- Department of Neurology, The First Hospital of Lanzhou University, Lanzhou, 730000, China
| | - Li-He Yao
- Department of Neurology, The First Hospital of Lanzhou University, Lanzhou, 730000, China
| | - Ni Tang
- Department of Neurology, The First Hospital of Lanzhou University, Lanzhou, 730000, China
| | - Zhen-Xiu Jiang
- Department of Neurology, The First Hospital of Lanzhou University, Lanzhou, 730000, China
| | - Yu Luo
- Institute of Pathophysiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, 730000, China.
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Abstract
The release from cells of signaling molecules through the controlled process of exocytosis involves multiple coordinated steps and is essential for the proper control of a multitude of biological pathways across the endocrine and nervous systems. However, these events are minute both temporally and in terms of the minute amounts of neurotransmitters, hormones, growth factors, and peptides released from single vesicles during exocytosis. It is therefore difficult to measure the kinetics of single exocytosis events in real time. One noninvasive method of measuring the release of molecules from cells is carbon-fiber amperometry. In this chapter, we will describe how we undertake such measurements from both single cells and in live tissue, how the subsequent data are analyzed, and how we interpret these results in terms of their relevant physiology.
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Martínez-Cué C, Rueda N. Signalling Pathways Implicated in Alzheimer's Disease Neurodegeneration in Individuals with and without Down Syndrome. Int J Mol Sci 2020; 21:E6906. [PMID: 32962300 PMCID: PMC7555886 DOI: 10.3390/ijms21186906] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 09/17/2020] [Accepted: 09/18/2020] [Indexed: 02/07/2023] Open
Abstract
Down syndrome (DS), the most common cause of intellectual disability of genetic origin, is characterized by alterations in central nervous system morphology and function that appear from early prenatal stages. However, by the fourth decade of life, all individuals with DS develop neuropathology identical to that found in sporadic Alzheimer's disease (AD), including the development of amyloid plaques and neurofibrillary tangles due to hyperphosphorylation of tau protein, loss of neurons and synapses, reduced neurogenesis, enhanced oxidative stress, and mitochondrial dysfunction and neuroinflammation. It has been proposed that DS could be a useful model for studying the etiopathology of AD and to search for therapeutic targets. There is increasing evidence that the neuropathological events associated with AD are interrelated and that many of them not only are implicated in the onset of this pathology but are also a consequence of other alterations. Thus, a feedback mechanism exists between them. In this review, we summarize the signalling pathways implicated in each of the main neuropathological aspects of AD in individuals with and without DS as well as the interrelation of these pathways.
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Affiliation(s)
- Carmen Martínez-Cué
- Department of Physiology and Pharmacology, Faculty of Medicine, University of Cantabria, 39011 Santander, Spain;
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7
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Lloret A, Monllor P, Fuchsberger T, Giraldo E, Perluigi M, Vina J. Increased basal antioxidant levels in RCAN1 - deficient mice lowers oxidative injury after acute paraquat insult. Free Radic Res 2020; 54:442-454. [PMID: 32686528 DOI: 10.1080/10715762.2020.1798002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
RCAN1 is an inhibitor of the phosphatase calcineurin, which is involved in the regulation of oxidative stress and apoptosis, among other important cell processes. Here we have used RCAN1 deficient mice (RCAN1-/-) to elucidate its role after an acute oxidative insult such as paraquat injection. We have observed that RCAN1-/- mice show less oxidative damage than wildtype (WT) mice after treatment. Under basal conditions, RCAN1-/- animals express more calcineurin, heme oxygenase-1, Nrf2, and catalase compared to WT mice (controls). This may explain the less severe effect of paraquat treatment on RCAN1-/- mice compared to WT. We showed that oxidative stress is involved in the early stages of apoptosis, thus we determined the apoptotic effector BAD and found that decreases in RCAN1-/- mice after treatment with paraquat compared with WT in similar experimental conditions. Our results suggest that RCAN1 may be involved in the balance between oxidant and antioxidant species production in vivo.
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Affiliation(s)
- Ana Lloret
- Freshage Research Group, Department of Physiology, University of Valencia, CIBERFES-ISCIII, INCLIVA, Valencia, Spain
| | - Paloma Monllor
- Freshage Research Group, Department of Physiology, University of Valencia, CIBERFES-ISCIII, INCLIVA, Valencia, Spain
| | - Tanja Fuchsberger
- Freshage Research Group, Department of Physiology, University of Valencia, CIBERFES-ISCIII, INCLIVA, Valencia, Spain
| | - Esther Giraldo
- Freshage Research Group, Department of Physiology, University of Valencia, CIBERFES-ISCIII, INCLIVA, Valencia, Spain.,Department of Biotechnology, Universitat Politècnica de València, Valencia, Spain.,The Principe Felipe Research Center, Valencia, Spain
| | - Marzia Perluigi
- Department of Biochemical Sciences, Sapienza University of Rome, Rome, Italy
| | - Jose Vina
- Freshage Research Group, Department of Physiology, University of Valencia, CIBERFES-ISCIII, INCLIVA, Valencia, Spain
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8
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Huang M, Rathore SS, Lindau M. Drug testing complementary metal-oxide-semiconductor chip reveals drug modulation of transmitter release for potential therapeutic applications. J Neurochem 2019; 151:38-49. [PMID: 31274190 PMCID: PMC6837173 DOI: 10.1111/jnc.14815] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 06/05/2019] [Accepted: 07/02/2019] [Indexed: 01/01/2023]
Abstract
Neurodegenerative diseases, such as Parkinson’s disease, Alzheimer’s disease, and Huntington’s disease, are considered incurable and significantly reduce the quality of life of the patients. A variety of drugs that modulate neurotransmitter levels have been used for the treatment of the neurodegenerative diseases but with limited efficacy. In this work, an amperometric complementary metal‐oxide‐semiconductor (CMOS) chip is used for high‐throughput drug testing with respect to the modulation of transmitter release from single vesicles using chromaffin cells prepared from bovine adrenal glands as a model system. Single chromaffin cell amperometry was performed with high efficiency on the surface‐modified CMOS chip and follow‐up whole‐cell patch‐clamp experiments were performed to determine the readily releasable pool sizes. We show that the antidepressant drug bupropion significantly increases the amount of neurotransmitter released in individual quantal release events. The antidepressant drug citalopram accelerates rapid neurotransmitter release following stimulation and follow‐up patch‐clamp experiments reveal that this is because of the increase in the pool of readily releasable vesicles. These results shed light on the mechanisms by which bupropion and citalopram may be potentially effective in the treatment of neurodegenerative diseases. These results demonstrate that the CMOS amperometry chip technology is an excellent tool for drug testing to determine the specific mechanisms by which they modulate neurotransmitter release. ![]()
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Affiliation(s)
- Meng Huang
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York, USA.,School of Applied and Engineering Physics, Cornell University, Ithaca, New York, USA
| | - Shailendra S Rathore
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York, USA
| | - Manfred Lindau
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York, USA
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9
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N M, C F, I V, Ca M, Rc K, Ai B, A R, Ma P, DI F, Pa A. The Down Syndrome-Associated Protein, Regulator of Calcineurin-1, is Altered in Alzheimer's Disease and Dementia with Lewy Bodies. JOURNAL OF ALZHEIMER'S DISEASE & PARKINSONISM 2019; 9. [PMID: 31263630 PMCID: PMC6602587 DOI: 10.4172/2161-0460.1000462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
There is a known relationship between Alzheimer’s disease (AD) and Down syndrome (DS), with the latter typically developing AD-like neuropathology in mid-life. In order to further understand this relationship we examined intersectin-1 (ITSN1) and the regulator of calcineurin-1 (RCAN1), proteins involved in endosomal and lysosomal trafficking that are over-expressed in DS. We examined RCAN1 and ITSN1 levels (both long (-L) and short (-S) isoforms) and the level of endogenous metals in White Blood Cells (WBCs) collected from AD patients who were enrolled in the Australian Imaging, Biomarker and Lifestyle Study on Ageing (AIBL). We also examined RCAN1 and ITSN1-S and -L in post-mortem brain tissue in a separate cohort of patients with AD or other types of dementia including Dementia with Lewy Bodies (DLB) and non-Alzheimer’s disease dementia. We found that RCAN1 was significantly elevated in AD and DLB brain compared with controls, but there was no difference in the level of RCAN1 in WBCs of AD patients. There were no differences in the levels of ITSN1-L and −S between AD and the control, nor between other types of dementia and the control. We found that there were no differences in the levels of metals between AD and the control WBCs. In conclusion, our data demonstrate that RCAN1 is differentially regulated between the peripheral and central compartments in AD and should be further investigated to understand its potential role in dementia of AD and DLB.
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Affiliation(s)
- Malakooti N
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, 3010, Victoria, Australia
| | | | - Fowler C
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Volitakis I
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - McLean Ca
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Kim Rc
- Department of Pathology and Laboratory Medicine, University of California, Irvine, USA
| | - Bush Ai
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Rembach A
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Pritchard Ma
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, 3168, Victoria, Australia
| | - Finkelstein DI
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Adlard Pa
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, 3010, Victoria, Australia
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Rotter D, Peiris H, Grinsfelder DB, Martin AM, Burchfield J, Parra V, Hull C, Morales CR, Jessup CF, Matusica D, Parks BW, Lusis AJ, Nguyen NUN, Oh M, Iyoke I, Jakkampudi T, McMillan DR, Sadek HA, Watt MJ, Gupta RK, Pritchard MA, Keating DJ, Rothermel BA. Regulator of Calcineurin 1 helps coordinate whole-body metabolism and thermogenesis. EMBO Rep 2018; 19:embr.201744706. [PMID: 30389725 DOI: 10.15252/embr.201744706] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 09/12/2018] [Accepted: 10/05/2018] [Indexed: 12/12/2022] Open
Abstract
Increasing non-shivering thermogenesis (NST), which expends calories as heat rather than storing them as fat, is championed as an effective way to combat obesity and metabolic disease. Innate mechanisms constraining the capacity for NST present a fundamental limitation to this approach, yet are not well understood. Here, we provide evidence that Regulator of Calcineurin 1 (RCAN1), a feedback inhibitor of the calcium-activated protein phosphatase calcineurin (CN), acts to suppress two distinctly different mechanisms of non-shivering thermogenesis (NST): one involving the activation of UCP1 expression in white adipose tissue, the other mediated by sarcolipin (SLN) in skeletal muscle. UCP1 generates heat at the expense of reducing ATP production, whereas SLN increases ATP consumption to generate heat. Gene expression profiles demonstrate a high correlation between Rcan1 expression and metabolic syndrome. On an evolutionary timescale, in the context of limited food resources, systemic suppression of prolonged NST by RCAN1 might have been beneficial; however, in the face of caloric abundance, RCAN1-mediated suppression of these adaptive avenues of energy expenditure may now contribute to the growing epidemic of obesity.
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Affiliation(s)
- David Rotter
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Heshan Peiris
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - D Bennett Grinsfelder
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Alyce M Martin
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - Jana Burchfield
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Valentina Parra
- Faculty of Chemical and Pharmaceutical Sciences & Faculty of Medicine, Advanced Center for Chronic Diseases (ACCDiS) and Center for Exercise Metabolism and Cancer (CEMC), University of Chile, Santiago, Chile
| | - Christi Hull
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Cyndi R Morales
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Claire F Jessup
- Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - Dusan Matusica
- Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - Brian W Parks
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, USA
| | - Aldons J Lusis
- Division of Cardiology, Department of Medicine, University of California at Los Angeles, Los Angeles, CA, USA
| | - Ngoc Uyen Nhi Nguyen
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Misook Oh
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Chemistry, Pohang University of Science and Technology, Pohang, South Korea
| | - Israel Iyoke
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Tanvi Jakkampudi
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - D Randy McMillan
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Children's Medical Centre, Dallas, TX, USA
| | - Hesham A Sadek
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Matthew J Watt
- The Department of Physiology and Monash Biomedicine Discovery Institute, Metabolic Disease and Obesity Program, Monash University, Clayton, Vic., Australia
| | - Rana K Gupta
- Touchstone Diabetes Center and Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Melanie A Pritchard
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Vic., Australia
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia .,South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, Australia
| | - Beverly A Rothermel
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA .,Department of Molecular Biology, University of Texas Southwestern Medical Centre, Dallas, TX, USA
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Vásquez-Navarrete J, Martínez AD, Ory S, Baéz-Matus X, González-Jamett AM, Brauchi S, Caviedes P, Cárdenas AM. RCAN1 Knockdown Reverts Defects in the Number of Calcium-Induced Exocytotic Events in a Cellular Model of Down Syndrome. Front Cell Neurosci 2018; 12:189. [PMID: 30034324 PMCID: PMC6043644 DOI: 10.3389/fncel.2018.00189] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 06/12/2018] [Indexed: 12/15/2022] Open
Abstract
In humans, Down Syndrome (DS) is a condition caused by partial or full trisomy of chromosome 21. Genes present in the DS critical region can result in excess gene dosage, which at least partially can account for DS phenotype. Although regulator of calcineurin 1 (RCAN1) belongs to this region and its ectopic overexpression in neurons impairs transmitter release, synaptic plasticity, learning and memory, the relative contribution of RCAN1 in a context of DS has yet to be clarified. In the present work, we utilized an in vitro model of DS, the CTb neuronal cell line derived from the brain cortex of a trisomy 16 (Ts16) fetal mouse, which reportedly exhibits acetylcholine release impairments compared to CNh cells (a neuronal cell line established from a normal littermate). We analyzed single exocytotic events by using total internal reflection fluorescence microscopy (TIRFM) and the vesicular acetylcholine transporter fused to the pH-sensitive green fluorescent protein (VAChT-pHluorin) as a reporter. Our analyses showed that, compared with control CNh cells, the trisomic CTb cells overexpress RCAN1, and they display a reduced number of Ca2+-induced exocytotic events. Remarkably, RCAN1 knockdown increases the extent of exocytosis at levels comparable to those of CNh cells. These results support a critical contribution of RCAN1 to the exocytosis process in the trisomic condition.
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Affiliation(s)
- Jacqueline Vásquez-Navarrete
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Stéphane Ory
- Centre National de la Recherche Scientifique (CNRS UPR 3212), Institut des Neurosciences Cellulaires et Intégratives (INCI), Strasbourg, France
| | - Ximena Baéz-Matus
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Arlek M González-Jamett
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Sebastián Brauchi
- Department of Physiology, Faculty of Medicine, Universidad Austral de Chile, Valdivia, Chile
| | - Pablo Caviedes
- Programa de Farmacología Molecular y Clínica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Centro de Biotecnología y Bioingeniería (CeBiB), Departamento de Ingeniería Química, Biotecnología y Materiales, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile
| | - Ana M Cárdenas
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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12
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Peiris H, Keating DJ. The neuronal and endocrine roles of RCAN1 in health and disease. Clin Exp Pharmacol Physiol 2017; 45:377-383. [PMID: 29094385 DOI: 10.1111/1440-1681.12884] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 10/18/2017] [Accepted: 10/24/2017] [Indexed: 01/15/2023]
Abstract
The regulator of calcineurin 1 (RCAN1) was first discovered as a gene located on human chromosome 21, expressed in neurons and overexpressed in the brains of Down syndrome individuals. Increased expression of RCAN1 has been linked with not only Down syndrome-associated pathology but also an associated neurological disorder, Alzheimer's Disease, in which neuronal RCAN1 expression is also increased. RCAN1 has additionally been demonstrated to affect other cell types including endocrine cells, with links to the pathogenesis of β-cell dysfunction in type 2 diabetes. The primary functions of RCAN1 relate to the inhibition of the phosphatase calcineurin, and to the regulation of mitochondrial function. Various forms of cellular stress such as reactive oxygen species and hyperglycaemia cause transient increases in RCAN1 expression. The short term (hours to days) induction of RCAN1 expression is generally thought to have a protective effect by regulating the expression of pro-survival genes in multiple cell types, many of which are mediated via the calcineurin/NFAT transcriptional pathway. However, strong evidence also supports the notion that chronic (weeks-years) overexpression of RCAN1 has a detrimental effect on cells and that this may drive pathophysiological changes in neurons and endocrine cells linked to Down syndrome, Alzheimer's Disease and type 2 diabetes. Here we review the evidence related to these roles of RCAN1 in neurons and endocrine cells and their relationship to these human health disorders.
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Affiliation(s)
- Heshan Peiris
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - Damien J Keating
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
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13
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Huntingtin-associated protein-1 (HAP1) regulates endocytosis and interacts with multiple trafficking-related proteins. Cell Signal 2017; 35:176-187. [DOI: 10.1016/j.cellsig.2017.02.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 02/16/2017] [Accepted: 02/28/2017] [Indexed: 12/24/2022]
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14
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Martin AM, Lumsden AL, Young RL, Jessup CF, Spencer NJ, Keating DJ. The nutrient-sensing repertoires of mouse enterochromaffin cells differ between duodenum and colon. Neurogastroenterol Motil 2017; 29. [PMID: 28251760 DOI: 10.1111/nmo.13046] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 01/11/2017] [Accepted: 01/12/2017] [Indexed: 01/30/2023]
Abstract
BACKGROUND Enterochromaffin (EC) cells within the gastrointestinal (GI) tract provide almost all body serotonin (5-hydroxytryptamine [5-HT]). Peripheral 5-HT, released from EC cells lining the gut wall, serves diverse physiological roles. These include modulating GI motility, bone formation, hepatic gluconeogenesis, thermogenesis, insulin resistance, and regulation of fat mass. Enterochromaffin cells are nutrient sensors, but which nutrients they are responsive to and how this changes in different parts of the GI tract are poorly understood. METHODS To accurately undertake such an examination, we undertook the first isolation and purification of primary mouse EC cells from both the duodenum and colon in the same animal. This allowed us to compare, in an internally controlled manner, regional differences in the expression of nutrient sensors in EC cells using real-time PCR. KEY RESULTS Both colonic and duodenal EC cells expressed G protein-coupled receptors and facilitative transporters for sugars, free fatty acids, amino acids, and lipid amides. We find differential expression of nutrient receptor and transporters in EC cells obtained from duodenal and colonic EC cells. Duodenal EC cells have higher expression of tryptophan hydroxylase-1, sugar transporters GLUT2, GLUT5, and free fatty acid receptors 1 and 3 (FFAR1 and FFAR3). Colonic EC cells express higher levels of GLUT1, FFAR2, and FFAR4. CONCLUSIONS & INFERENCES We highlight the diversity of EC cell physiology and identify differences in the regional sensing repertoire of EC cells to an assortment of nutrients. These data indicate that not all EC cells are similar and that differences in their physiological responses are likely dependent on their location within the GI tract.
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Affiliation(s)
- A M Martin
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - A L Lumsden
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - R L Young
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, Australia.,Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - C F Jessup
- Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia.,Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - N J Spencer
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia
| | - D J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia.,South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, Australia
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15
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Martin AM, Young RL, Leong L, Rogers GB, Spencer NJ, Jessup CF, Keating DJ. The Diverse Metabolic Roles of Peripheral Serotonin. Endocrinology 2017; 158:1049-1063. [PMID: 28323941 DOI: 10.1210/en.2016-1839] [Citation(s) in RCA: 149] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Accepted: 02/23/2017] [Indexed: 02/07/2023]
Abstract
Serotonin (5-hydroxytryptamine or 5-HT) is a multifunctional bioamine with important signaling roles in a range of physiological pathways. Almost all of the 5-HT in our bodies is synthesized in specialized enteroendocrine cells within the gastrointestinal (GI) mucosa called enterochromaffin (EC) cells. These cells provide all of our circulating 5-HT. We have long appreciated the important contributions of 5-HT within the gut, including its role in modulating GI motility. However, evidence of the physiological and clinical significance of gut-derived 5-HT outside of the gut has recently emerged, implicating 5-HT in regulation of glucose homeostasis, lipid metabolism, bone density, and diseases associated with metabolic syndrome, such as obesity and type 2 diabetes. Although a new picture has developed in the last decade regarding the various metabolic roles of peripheral serotonin, so too has our understanding of the physiology of EC cells. Given that they are scattered throughout the lining of the GI tract within the epithelial cell layer, these cells are typically difficult to study. Advances in isolation procedures now allow the study of pure EC-cell cultures and single cells, enabling studies of EC-cell physiology to occur. EC cells are sensory cells that are capable of integrating cues from ingested nutrients, the enteric nervous system, and the gut microbiome. Thus, levels of peripheral 5-HT can be modulated by a multitude of factors, resulting in both local and systemic effects for the regulation of a raft of physiological pathways related to metabolism and obesity.
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Affiliation(s)
- Alyce M Martin
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide 5042, Australia
| | - Richard L Young
- Nutrition and Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide 5001, Australia
- Adelaide Medical School, University of Adelaide, Adelaide 5005, Australia
| | - Lex Leong
- Infection and Immunity, SAHMRI, Adelaide 5001, Australia
- SAHMRI Microbiome Research Laboratory, School of Medicine, Flinders University of South Australia, Adelaide 5042, Australia
| | - Geraint B Rogers
- Infection and Immunity, SAHMRI, Adelaide 5001, Australia
- SAHMRI Microbiome Research Laboratory, School of Medicine, Flinders University of South Australia, Adelaide 5042, Australia
| | - Nick J Spencer
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide 5042, Australia
| | - Claire F Jessup
- Adelaide Medical School, University of Adelaide, Adelaide 5005, Australia
- Discipline of Anatomy and Histology, Flinders University of South Australia, Adelaide 5042, Australia
| | - Damien J Keating
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide 5042, Australia
- Nutrition and Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide 5001, Australia
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16
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Zoltowska KM, Maesako M, Lushnikova I, Takeda S, Keller LJ, Skibo G, Hyman BT, Berezovska O. Dynamic presenilin 1 and synaptotagmin 1 interaction modulates exocytosis and amyloid β production. Mol Neurodegener 2017; 12:15. [PMID: 28193235 PMCID: PMC5307796 DOI: 10.1186/s13024-017-0159-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 02/09/2017] [Indexed: 01/09/2023] Open
Abstract
Background Alzheimer’s disease (AD)-linked protein, presenilin 1 (PS1), is present at the synapse, and the knock-out of presenilin in mice leads to synaptic dysfunction. On the other hand, synaptic activity was shown to influence PS1-dependent generation of distinct amyloid β (Aβ) species. However, the precise nature of these regulations remains unclear. The current study reveals novel role of PS1 at the synapse, and deciphers how PS1 and synaptic vesicle-associated protein, synaptotagmin 1 (Syt1) modulate each other functions in neurons via direct activity-triggered interaction. Additionally, the therapeutic potential of fostering PS1-Syt1 binding is investigated as a synapse-specific strategy for AD prevention. Methods PS1-based cell-permeable peptide targeting PS1-Syt1 binding site was designed to inhibit PS1-Syt1 interaction in neurons. PS1 conformation, synaptic vesicle exocytosis and trafficking were assayed by fluorescence lifetime imaging microscopy (FLIM), glutamate release/synaptopHluorin assay, and fluorescence recovery after photobleaching, respectively. Syt1 level and interaction with PS1 in control and sporadic AD brains were determined by immunohistochemistry and FLIM. AAV-mediated delivery of Syt1 into mouse hippocampi was used to investigate the therapeutic potential of strengthening PS1-Syt1 binding in vivo. Statistical significance was determined using two-tailed unpaired Student’s t-test, Mann-Whitney’s U-test or two-way ANOVA followed by a Bonferroni’s post-test. Results We demonstrate that targeted inhibition of the PS1-Syt1 binding in neurons, without changing the proteins’ expression level, triggers “pathogenic” conformational shift of PS1, and consequent increase in the Aβ42/40 ratio. Moreover, our data indicate that PS1, by binding directly to Syt1, regulates synaptic vesicle trafficking and facilitates exocytosis and neurotransmitter release. Analysis of human brain tissue revealed that not only Syt1 levels but also interactions between remaining Syt1 and PS1 are diminished in sporadic AD. On the other hand, overexpression of Syt1 in mouse hippocampi was found to potentiate PS1-Syt1 binding and promote “protective” PS1 conformation. Conclusions The study reports novel functions of PS1 and Syt1 at the synapse, and demonstrates the importance of PS1-Syt1 binding for exocytosis and safeguarding PS1 conformation. It suggests that reduction in the Syt1 level and PS1-Syt1 interactions in AD brain may present molecular underpinning of the pathogenic PS1 conformation, increased Aβ42/40 ratio, and impaired exocytosis. Electronic supplementary material The online version of this article (doi:10.1186/s13024-017-0159-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Katarzyna Marta Zoltowska
- Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA
| | - Masato Maesako
- Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA
| | - Iryna Lushnikova
- Department of Cytology, Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Street, 01024, Kyiv, Ukraine
| | - Shuko Takeda
- Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA
| | - Laura J Keller
- Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA
| | - Galina Skibo
- Department of Cytology, Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Street, 01024, Kyiv, Ukraine
| | - Bradley T Hyman
- Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA
| | - Oksana Berezovska
- Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA.
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17
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Li W, Choi TW, Ahnn J, Lee SK. Allele-Specific Phenotype Suggests a Possible Stimulatory Activity of RCAN-1 on Calcineurin in Caenorhabditis elegans. Mol Cells 2016; 39:827-833. [PMID: 27871170 PMCID: PMC5125939 DOI: 10.14348/molcells.2016.0222] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 10/27/2016] [Accepted: 10/31/2016] [Indexed: 11/27/2022] Open
Abstract
Regulator of calcineurin 1 (RCAN1) binds to calcineurin through the PxIxIT motif, which is evolutionarily conserved. SP repeat phosphorylation in RCAN1 is required for its complete function. The specific interaction between RCAN1 and calcineurin is critical for calcium/calmodulin-dependent regulation of calcineurin serine/threonine phosphatase activity. In this study, we investigated two available deletion rcan-1 mutants in Caenorhabditis elegans, which proceed differently for transcription and translation. We found that rcan-1 may be required for calcineurin activity and possess calcineurin-independent function in body growth and egg-laying behavior. In the genetic background of enhanced calcineurin activity, the rcan-1 mutant expressing a truncated RCAN-1 which retains the calcineurin-binding PxIxIT motif but misses SP repeats stimulated growth, while rcan-1 lack mutant resulted in hyperactive egg-laying suppression. These data suggest rcan-1 has unknown functions independent of calcineurin, and may be a stimulatory calcineurin regulator under certain circumstances.
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Affiliation(s)
- Weixun Li
- Department of Life Science, Hanyang University, Seoul 04763,
Korea
- BK21 PLUS Life Science for BDR Team, Hanyang University, Seoul 04763,
Korea
- Research Institute for Natural Sciences, Hanyang University, Seoul 04763,
Korea
| | - Tae-Woo Choi
- Department of Life Science, Hanyang University, Seoul 04763,
Korea
- BK21 PLUS Life Science for BDR Team, Hanyang University, Seoul 04763,
Korea
- Research Institute for Natural Sciences, Hanyang University, Seoul 04763,
Korea
| | - Joohong Ahnn
- Department of Life Science, Hanyang University, Seoul 04763,
Korea
- BK21 PLUS Life Science for BDR Team, Hanyang University, Seoul 04763,
Korea
- Research Institute for Natural Sciences, Hanyang University, Seoul 04763,
Korea
| | - Sun-Kyung Lee
- Department of Life Science, Hanyang University, Seoul 04763,
Korea
- BK21 PLUS Life Science for BDR Team, Hanyang University, Seoul 04763,
Korea
- Research Institute for Natural Sciences, Hanyang University, Seoul 04763,
Korea
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18
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Brettle M, Patel S, Fath T. Tropomyosins in the healthy and diseased nervous system. Brain Res Bull 2016; 126:311-323. [PMID: 27298153 DOI: 10.1016/j.brainresbull.2016.06.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 06/09/2016] [Accepted: 06/10/2016] [Indexed: 12/25/2022]
Abstract
Regulation of the actin cytoskeleton is dependent on a plethora of actin-associated proteins in all eukaryotic cells. The family of tropomyosins plays a key role in controlling the function of several of these actin-associated proteins and their access to actin filaments. In order to understand the regulation of the actin cytoskeleton in highly dynamic subcellular compartments of neurons such as growth cones of developing neurons and the synaptic compartment of mature neurons, it is pivotal to decipher the functional role of tropomyosins in the nervous system. In this review, we will discuss the current understanding and recent findings on the regulation of the actin cytoskeleton by tropomyosins and potential implication that this has for the dysregulation of the actin cytoskeleton in neurological diseases.
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Affiliation(s)
- Merryn Brettle
- Neurodegeneration and Repair Unit, School of Medical Sciences, University of New South Wales, 2052 Sydney, New South Wales, Australia
| | - Shrujna Patel
- Neurodegeneration and Repair Unit, School of Medical Sciences, University of New South Wales, 2052 Sydney, New South Wales, Australia
| | - Thomas Fath
- Neurodegeneration and Repair Unit, School of Medical Sciences, University of New South Wales, 2052 Sydney, New South Wales, Australia.
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19
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Thorn P, Zorec R, Rettig J, Keating DJ. Exocytosis in non-neuronal cells. J Neurochem 2016; 137:849-59. [PMID: 26938142 DOI: 10.1111/jnc.13602] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 02/02/2016] [Accepted: 03/01/2016] [Indexed: 12/18/2022]
Abstract
Exocytosis is the process by which stored neurotransmitters and hormones are released via the fusion of secretory vesicles with the plasma membrane. It is a dynamic, rapid and spatially restricted process involving multiple steps including vesicle trafficking, tethering, docking, priming and fusion. For many years great steps have been undertaken in our understanding of how exocytosis occurs in different cell types, with significant focus being placed on synaptic release and neurotransmission. However, this process of exocytosis is an essential component of cell signalling throughout the body and underpins a diverse array of essential physiological pathways. Many similarities exist between different cell types with regard to key aspects of the exocytosis pathway, such as the need for Ca(2+) to trigger it or the involvement of members of the N-ethyl maleimide-sensitive fusion protein attachment protein receptor protein families. However, it is also equally clear that non-neuronal cells have acquired highly specialized mechanisms to control the release of their own unique chemical messengers. This review will focus on several important non-neuronal cell types and discuss what we know about the mechanisms they use to control exocytosis and how their specialized output is relevant to the physiological role of each individual cell type. These include enteroendocrine cells, pancreatic β cells, astrocytes, lactotrophs and cytotoxic T lymphocytes. Non-neuronal cells have acquired highly specialized mechanisms to control the release of unique chemical messengers, such as polarised fusion of insulin granules in pancreatic β cells targeted towards the vasculature (top). This review discusses mechanisms used in several important non-neuronal cell types to control exocytosis, and the relevance of intermediate vesicle fusion pore states (bottom) and their specialized output to the physiological role of each cell type. These include enteroendocrine cells, pancreatic β cells, astrocytes, lactotrophs and cytotoxic T lymphocytes. This article is part of a mini review series on Chromaffin cells (ISCCB Meeting, 2015).
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Affiliation(s)
- Peter Thorn
- Charles Perkins Centre, John Hopkins Drive, The University of Sydney, Camperdown, NSW, Australia
| | - Robert Zorec
- Laboratory of Neuroendocrinology and Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
| | - Jens Rettig
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, SA, Australia.,South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia
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20
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Peiris H, Duffield MD, Fadista J, Jessup CF, Kashmir V, Genders AJ, McGee SL, Martin AM, Saiedi M, Morton N, Carter R, Cousin MA, Kokotos AC, Oskolkov N, Volkov P, Hough TA, Fisher EMC, Tybulewicz VLJ, Busciglio J, Coskun PE, Becker A, Belichenko PV, Mobley WC, Ryan MT, Chan JY, Laybutt DR, Coates PT, Yang S, Ling C, Groop L, Pritchard MA, Keating DJ. A Syntenic Cross Species Aneuploidy Genetic Screen Links RCAN1 Expression to β-Cell Mitochondrial Dysfunction in Type 2 Diabetes. PLoS Genet 2016; 12:e1006033. [PMID: 27195491 PMCID: PMC4873152 DOI: 10.1371/journal.pgen.1006033] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 04/18/2016] [Indexed: 12/20/2022] Open
Abstract
Type 2 diabetes (T2D) is a complex metabolic disease associated with obesity, insulin resistance and hypoinsulinemia due to pancreatic β-cell dysfunction. Reduced mitochondrial function is thought to be central to β-cell dysfunction. Mitochondrial dysfunction and reduced insulin secretion are also observed in β-cells of humans with the most common human genetic disorder, Down syndrome (DS, Trisomy 21). To identify regions of chromosome 21 that may be associated with perturbed glucose homeostasis we profiled the glycaemic status of different DS mouse models. The Ts65Dn and Dp16 DS mouse lines were hyperglycemic, while Tc1 and Ts1Rhr mice were not, providing us with a region of chromosome 21 containing genes that cause hyperglycemia. We then examined whether any of these genes were upregulated in a set of ~5,000 gene expression changes we had identified in a large gene expression analysis of human T2D β-cells. This approach produced a single gene, RCAN1, as a candidate gene linking hyperglycemia and functional changes in T2D β-cells. Further investigations demonstrated that RCAN1 methylation is reduced in human T2D islets at multiple sites, correlating with increased expression. RCAN1 protein expression was also increased in db/db mouse islets and in human and mouse islets exposed to high glucose. Mice overexpressing RCAN1 had reduced in vivo glucose-stimulated insulin secretion and their β-cells displayed mitochondrial dysfunction including hyperpolarised membrane potential, reduced oxidative phosphorylation and low ATP production. This lack of β-cell ATP had functional consequences by negatively affecting both glucose-stimulated membrane depolarisation and ATP-dependent insulin granule exocytosis. Thus, from amongst the myriad of gene expression changes occurring in T2D β-cells where we had little knowledge of which changes cause β-cell dysfunction, we applied a trisomy 21 screening approach which linked RCAN1 to β-cell mitochondrial dysfunction in T2D.
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Affiliation(s)
- Heshan Peiris
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
| | - Michael D. Duffield
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
| | | | - Claire F. Jessup
- Islet Biology Laboratory, Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
- Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Vinder Kashmir
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
| | - Amanda J. Genders
- Metabolic Remodelling Laboratory, Metabolic Research Unit, School of Medicine, Deakin University, Geelong, Australia
| | - Sean L. McGee
- Metabolic Remodelling Laboratory, Metabolic Research Unit, School of Medicine, Deakin University, Geelong, Australia
- Metabolism and Inflammation Program, Baker IDI Heart and Diabetes Institute, Melbourne, Australia
| | - Alyce M. Martin
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
| | - Madiha Saiedi
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
| | - Nicholas Morton
- Queen's Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Roderick Carter
- Queen's Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Michael A. Cousin
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom
| | - Alexandros C. Kokotos
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Petr Volkov
- Lund University Diabetes Centre, Malmö, Sweden
| | - Tertius A. Hough
- Mary Lyon Centre Pathology, MRC Harwell, Harwell Oxford Science Park, Oxford, United Kingdom
| | - Elizabeth M. C. Fisher
- Department of Neurodegenerative Disease, UCL Institute of Neurology, London, United Kingdom
| | - Victor L. J. Tybulewicz
- Francis Crick Institute, Mill Hill, London, United Kingdom
- Department of Medicine, Imperial College London, London, United Kingdom
| | - Jorge Busciglio
- Department of Neurobiology and Behaviour, University of California, Irvine, Irvine, California, United States of America
| | - Pinar E. Coskun
- Department of Neurobiology and Behaviour, University of California, Irvine, Irvine, California, United States of America
| | - Ann Becker
- Department of Neurosciences School of Medicine, University of California, San Diego, San Diego, California, United States of America
| | - Pavel V. Belichenko
- Department of Neurosciences School of Medicine, University of California, San Diego, San Diego, California, United States of America
| | - William C. Mobley
- Department of Neurosciences School of Medicine, University of California, San Diego, San Diego, California, United States of America
| | - Michael T. Ryan
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia
| | - Jeng Yie Chan
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales, Australia
| | - D. Ross Laybutt
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales, Australia
| | - P. Toby Coates
- Clinical and Experimental Transplantation Group, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia, Australia
| | - Sijun Yang
- Animal Experiment Center, Animal Biosafety Level-III Laboratory, Wuhan University, Wuhan, China
| | | | - Leif Groop
- Lund University Diabetes Centre, Malmö, Sweden
| | - Melanie A. Pritchard
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia
| | - Damien J. Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
- South Australian Health and Medical Research Institute, Adelaide, Australia
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21
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Marland JRK, Smillie KJ, Cousin MA. Synaptic Vesicle Recycling Is Unaffected in the Ts65Dn Mouse Model of Down Syndrome. PLoS One 2016; 11:e0147974. [PMID: 26808141 PMCID: PMC4726538 DOI: 10.1371/journal.pone.0147974] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Accepted: 01/11/2016] [Indexed: 01/08/2023] Open
Abstract
Down syndrome (DS) is the most common genetic cause of intellectual disability, and arises from trisomy of human chromosome 21. Accumulating evidence from studies of both DS patient tissue and mouse models has suggested that synaptic dysfunction is a key factor in the disorder. The presence of several genes within the DS trisomy that are either directly or indirectly linked to synaptic vesicle (SV) endocytosis suggested that presynaptic dysfunction could underlie some of these synaptic defects. Therefore we determined whether SV recycling was altered in neurons from the Ts65Dn mouse, the best characterised model of DS to date. We found that SV exocytosis, the size of the SV recycling pool, clathrin-mediated endocytosis, activity-dependent bulk endocytosis and SV generation from bulk endosomes were all unaffected by the presence of the Ts65Dn trisomy. These results were obtained using battery of complementary assays employing genetically-encoded fluorescent reporters of SV cargo trafficking, and fluorescent and morphological assays of fluid-phase uptake in primary neuronal culture. The absence of presynaptic dysfunction in central nerve terminals of the Ts65Dn mouse suggests that future research should focus on the established alterations in excitatory / inhibitory balance as a potential route for future pharmacotherapy.
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Affiliation(s)
- Jamie R. K. Marland
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, 15 George Square, Edinburgh, EH8 9XD, United Kingdom
| | - Karen J. Smillie
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, 15 George Square, Edinburgh, EH8 9XD, United Kingdom
| | - Michael A. Cousin
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, 15 George Square, Edinburgh, EH8 9XD, United Kingdom
- * E-mail:
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22
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Jarukanont D, Bonifas Arredondo I, Femat R, Garcia ME. Vesicle Motion during Sustained Exocytosis in Chromaffin Cells: Numerical Model Based on Amperometric Measurements. PLoS One 2015; 10:e0144045. [PMID: 26675312 PMCID: PMC4699451 DOI: 10.1371/journal.pone.0144045] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 11/12/2015] [Indexed: 01/26/2023] Open
Abstract
Chromaffin cells release catecholamines by exocytosis, a process that includes vesicle docking, priming and fusion. Although all these steps have been intensively studied, some aspects of their mechanisms, particularly those regarding vesicle transport to the active sites situated at the membrane, are still unclear. In this work, we show that it is possible to extract information on vesicle motion in Chromaffin cells from the combination of Langevin simulations and amperometric measurements. We developed a numerical model based on Langevin simulations of vesicle motion towards the cell membrane and on the statistical analysis of vesicle arrival times. We also performed amperometric experiments in bovine-adrenal Chromaffin cells under Ba2+ stimulation to capture neurotransmitter releases during sustained exocytosis. In the sustained phase, each amperometric peak can be related to a single release from a new vesicle arriving at the active site. The amperometric signal can then be mapped into a spike-series of release events. We normalized the spike-series resulting from the current peaks using a time-rescaling transformation, thus making signals coming from different cells comparable. We discuss why the obtained spike-series may contain information about the motion of all vesicles leading to release of catecholamines. We show that the release statistics in our experiments considerably deviate from Poisson processes. Moreover, the interspike-time probability is reasonably well described by two-parameter gamma distributions. In order to interpret this result we computed the vesicles’ arrival statistics from our Langevin simulations. As expected, assuming purely diffusive vesicle motion we obtain Poisson statistics. However, if we assume that all vesicles are guided toward the membrane by an attractive harmonic potential, simulations also lead to gamma distributions of the interspike-time probability, in remarkably good agreement with experiment. We also show that including the fusion-time statistics in our model does not produce any significant changes on the results. These findings indicate that the motion of the whole ensemble of vesicles towards the membrane is directed and reflected in the amperometric signals. Our results confirm the conclusions of previous imaging studies performed on single vesicles that vesicles’ motion underneath plasma membranes is not purely random, but biased towards the membrane.
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Affiliation(s)
- Daungruthai Jarukanont
- Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), Universität Kassel, Kassel, Germany
| | - Imelda Bonifas Arredondo
- División de Matemáticas Aplicadas, IPICYT, Camino a la Presa San José 2055, Lomas 4 Sección., San Luis Potosí, México
| | - Ricardo Femat
- División de Matemáticas Aplicadas, IPICYT, Camino a la Presa San José 2055, Lomas 4 Sección., San Luis Potosí, México
- * E-mail: (RF); (MEG)
| | - Martin E. Garcia
- Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), Universität Kassel, Kassel, Germany
- * E-mail: (RF); (MEG)
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Zelkas L, Raghupathi R, Lumsden AL, Martin AM, Sun E, Spencer NJ, Young RL, Keating DJ. Serotonin-secreting enteroendocrine cells respond via diverse mechanisms to acute and chronic changes in glucose availability. Nutr Metab (Lond) 2015; 12:55. [PMID: 26673561 PMCID: PMC4678665 DOI: 10.1186/s12986-015-0051-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 12/09/2015] [Indexed: 01/11/2023] Open
Abstract
Background Enteroendocrine cells collectively constitute our largest endocrine tissue, with serotonin (5-HT) secreting enterochromaffin (EC) cells being the largest component (~50 %). This gut-derived 5-HT has multiple paracrine and endocrine roles. EC cells are thought to act as nutrient sensors and luminal glucose is the major absorbed form of carbohydrate in the gut and activates secretion in an array of cell types. It is unknown whether EC cells release 5-HT in response to glucose in primary EC cells. Furthermore, fasting augments 5-HT synthesis and release into the circulation. However, which nutrients cause fasting-induced synthesis of EC cell 5-HT is unknown. Here we examine the effects of acute and chronic changes in glucose availability on 5-HT release from intact tissue and single EC cells. Methods We utilised established approaches in our laboratories measuring 5-HT release in intact mouse colon with amperometry. We then examined single EC cells function using our published protocol in guinea-pig colon. Single cell Ca2+ imaging and amperometry were used with these cells. Real-time PCR was used along with amperometry, on primary EC cells cultured for 24 h in 5 or 25 mM glucose. Results We demonstrate that acute increases in glucose, at levels found in the gut lumen rather than in plasma, trigger 5-HT release from intact colon, and cause Ca2+ entry and 5-HT release in primary EC cells. Single cell amperometry demonstrates that high glucose increases the amount of 5-HT released from individual vesicles as they undergo exocytosis. Finally, 24 h incubation of EC cells in low glucose causes an increase in the transcription of the 5-HT synthesising enzyme Tph1 as well as increasing in 5-HT secretion in EC cells. Conclusions We demonstrate that primary EC cells respond to acute changes in glucose availability through increases in intracellular Ca2+ the activation of 5-HT secretion, but respond to chronic changes in glucose levels through the transcriptional regulation of Tph1 to alter 5-HT synthesis.
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Affiliation(s)
- Leah Zelkas
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia
| | - Ravi Raghupathi
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia ; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia
| | - Amanda L Lumsden
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia ; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia
| | - Alyce M Martin
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia ; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia
| | - Emily Sun
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia ; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia
| | - Nick J Spencer
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia
| | - Richard L Young
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia ; Discipline of Medicine, University of Adelaide, Adelaide, SA 5001 Australia
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Rd, Adelaide, SA 5042 Australia ; South Australian Health and Medical Research Institute (SAHMRI), Adelaide, 5001 Australia
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24
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Raghupathi R, Jessup CF, Lumsden AL, Keating DJ. Fusion Pore Size Limits 5-HT Release From Single Enterochromaffin Cell Vesicles. J Cell Physiol 2015; 231:1593-600. [PMID: 26574734 DOI: 10.1002/jcp.25256] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 11/13/2015] [Indexed: 12/15/2022]
Abstract
Enterochromaffin cells are the major site of serotonin (5-HT) synthesis and secretion providing ∼95% of the body's total 5-HT. 5-HT can act as a neurotransmitter or hormone and has several important endocrine and paracrine roles. We have previously demonstrated that EC cells release small amounts of 5-HT per exocytosis event compared to other endocrine cells. We utilized a recently developed method to purify EC cells to demonstrate the mechanisms underlying 5-HT packaging and release. Using the fluorescent probe FFN511, we demonstrate that EC cells express VMAT and that VMAT plays a functional role in 5-HT loading into vesicles. Carbon fiber amperometry studies illustrate that the amount of 5-HT released per exocytosis event from EC cells is dependent on both VMAT and the H(+)-ATPase pump, as demonstrated with reserpine or bafilomycin, respectively. We also demonstrate that increasing the amount of 5-HT loaded into EC cell vesicles does not result in an increase in quantal release. As this indicates that fusion pore size may be a limiting factor involved, we compared pore diameter in EC and chromaffin cells by assessing the vesicle capture of different-sized fluorescent probes to measure the extent of fusion pore dilation. This identified that EC cells have a reduced fusion pore expansion that does not exceed 9 nm in diameter. These results demonstrate that the small amounts of 5-HT released per fusion event in EC cells can be explained by a smaller fusion pore that limits 5-HT release capacity from individual vesicles.
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Affiliation(s)
- Ravinarayan Raghupathi
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Claire F Jessup
- Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, Australia.,Discipline of Medicine, University of Adelaide, Adelaide, Australia
| | - Amanda L Lumsden
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia.,South Australian Health and Medical Research Institute, Adelaide, Australia
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25
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Lee S, Bang SM, Hong YK, Lee JH, Jeong H, Park SH, Liu QF, Lee IS, Cho KS. The calcineurin inhibitor Sarah (Nebula) exacerbates Aβ42 phenotypes in a Drosophila model of Alzheimer's disease. Dis Model Mech 2015; 9:295-306. [PMID: 26659252 PMCID: PMC4826976 DOI: 10.1242/dmm.018069] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 11/28/2015] [Indexed: 11/20/2022] Open
Abstract
Expression of the Down syndrome critical region 1 (DSCR1) protein, an inhibitor of the Ca2+-dependent phosphatase calcineurin, is elevated in the brains of individuals with Down syndrome (DS) or Alzheimer's disease (AD). Although increased levels of DSCR1 were often observed to be deleterious to neuronal health, its beneficial effects against AD neuropathology have also been reported, and the roles of DSCR1 on the pathogenesis of AD remain controversial. Here, we investigated the role of sarah (sra; also known as nebula), a Drosophila DSCR1 ortholog, in amyloid-β42 (Aβ42)-induced neurological phenotypes in Drosophila. We detected sra expression in the mushroom bodies of the fly brain, which are a center for learning and memory in flies. Moreover, similar to humans with AD, Aβ42-expressing flies showed increased Sra levels in the brain, demonstrating that the expression pattern of DSCR1 with regard to AD pathogenesis is conserved in Drosophila. Interestingly, overexpression of sra using the UAS-GAL4 system exacerbated the rough-eye phenotype, decreased survival rates and increased neuronal cell death in Aβ42-expressing flies, without modulating Aβ42 expression. Moreover, neuronal overexpression of sra in combination with Aβ42 dramatically reduced both locomotor activity and the adult lifespan of flies, whereas flies with overexpression of sra alone showed normal climbing ability, albeit with a slightly reduced lifespan. Similarly, treatment with chemical inhibitors of calcineurin, such as FK506 and cyclosporin A, or knockdown of calcineurin expression by RNA interference (RNAi), exacerbated the Aβ42-induced rough-eye phenotype. Furthermore, sra-overexpressing flies displayed significantly decreased mitochondrial DNA and ATP levels, as well as increased susceptibility to oxidative stress compared to that of control flies. Taken together, our results demonstrating that sra overexpression augments Aβ42 cytotoxicity in Drosophila suggest that DSCR1 upregulation or calcineurin downregulation in the brain might exacerbate Aβ42-associated neuropathogenesis in AD or DS. Drosophila Collection: Chronically increased levels of Sarah (Nebula), a calcineurin inhibitor, cause mitochondria dysfunction and subsequently increased Aβ42-induced cytotoxicity in Drosophila.
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Affiliation(s)
- Soojin Lee
- Department of Biological Sciences, Konkuk University, Seoul 05029, Republic of Korea
| | - Se Min Bang
- Department of Biological Sciences, Konkuk University, Seoul 05029, Republic of Korea
| | - Yoon Ki Hong
- Department of Biological Sciences, Konkuk University, Seoul 05029, Republic of Korea
| | - Jang Ho Lee
- Department of Biological Sciences, Konkuk University, Seoul 05029, Republic of Korea
| | - Haemin Jeong
- Department of Biological Sciences, Konkuk University, Seoul 05029, Republic of Korea
| | - Seung Hwan Park
- Department of Biological Sciences, Konkuk University, Seoul 05029, Republic of Korea
| | - Quan Feng Liu
- Department of Oriental Medicine, Dongguk University, Gyeogju 38066, Republic of Korea Department of Oriental Neuropsychiatry, Graduate School of Oriental Medicine, Dongguk University, Gyeonggi 10326, Republic of Korea
| | - Im-Soon Lee
- Department of Biological Sciences, Konkuk University, Seoul 05029, Republic of Korea
| | - Kyoung Sang Cho
- Department of Biological Sciences, Konkuk University, Seoul 05029, Republic of Korea
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26
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Jackson J, Papadopulos A, Meunier FA, McCluskey A, Robinson PJ, Keating DJ. Small molecules demonstrate the role of dynamin as a bi-directional regulator of the exocytosis fusion pore and vesicle release. Mol Psychiatry 2015; 20:810-9. [PMID: 25939402 DOI: 10.1038/mp.2015.56] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 03/14/2015] [Accepted: 03/24/2015] [Indexed: 12/18/2022]
Abstract
Hormones and neurotransmitters are stored in specialised vesicles and released from excitable cells through exocytosis. During vesicle fusion with the plasma membrane, a transient fusion pore is created that enables transmitter release. The protein dynamin is known to regulate fusion pore expansion (FPE). The mechanism is unknown, but requires its oligomerisation-stimulated GTPase activity. We used a palette of small molecule dynamin modulators to reveal bi-directional regulation of FPE by dynamin and vesicle release in chromaffin cells. The dynamin inhibitors Dynole 34-2 and Dyngo 4a and the dynamin activator Ryngo 1-23 reduced or increased catecholamine released from single vesicles, respectively. Total internal reflection fluorescence (TIRF) microscopy demonstrated that dynamin stimulation with Ryngo 1-23 reduced the number of neuropeptide Y (NPY) kiss-and-run events, but not full fusion events, and slowed full fusion release kinetics. Amperometric stand-alone foot signals, representing transient kiss-and-run events, were less frequent but were of longer duration, similarly to full amperometric spikes and pre-spike foot signals. These effects are not due to alterations in vesicle size. Ryngo 1-23 action was blocked by inhibitors of actin polymerisation or myosin II. Therefore, we demonstrate using a novel pharmacological approach that dynamin not only controls FPE during exocytosis, but is a bi-directional modulator of the fusion pore that increases or decreases the amount released from a vesicle during exocytosis if it is activated or inhibited, respectively. As such, dynamin has the ability to exquisitely fine-tune transmitter release.
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Affiliation(s)
- J Jackson
- Discipline of Human Physiology, Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - A Papadopulos
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - F A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - A McCluskey
- Centre for Chemical Biology and Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales, Australia
| | - P J Robinson
- Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, Australia
| | - D J Keating
- 1] Discipline of Human Physiology, Centre for Neuroscience, Flinders University, Adelaide, Australia [2] South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia
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27
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Zmijewski PA, Gao LY, Saxena AR, Chavannes NK, Hushmendy SF, Bhoiwala DL, Crawford DR. Fish oil improves gene targets of Down syndrome in C57BL and BALB/c mice. Nutr Res 2015; 35:440-8. [DOI: 10.1016/j.nutres.2015.02.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 02/23/2015] [Accepted: 02/24/2015] [Indexed: 01/26/2023]
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28
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Abstract
Periventricular heterotopia (PH) is a cortical malformation characterized by aggregation of neurons lining the lateral ventricles due to abnormal neuronal migration. The molecular mechanism underlying the pathogenesis of PH is unclear. Here we show that Regulators of calcineurin 1 (Rcan1), a Down syndrome-related gene, plays an important role in radial migration of rat cortical neurons. Downregulation of Rcan1 by expressing shRNA impaired neural progenitor proliferation and led to defects in radial migration and PH. Two isoforms of Rcan1 (Rcan1-1 and Rcan1-4) are expressed in the rat brain. Migration defects due to downregulation of Rcan1 could be prevented by shRNA-resistant expression of Rcan1-1 but not Rcan1-4. Furthermore, we found that Rcan1 knockdown significantly decreased the expression level of Flna, an F-actin cross-linking protein essential for cytoskeleton rearrangement and cell migration, mutation of which causes the most common form of bilateral PH in humans. Finally, overexpression of FLNA in Rcan1 knockdown neurons prevented migration abnormalities. Together, these findings demonstrate that Rcan1 acts upstream from Flna in regulating radial migration and suggest that impairment of Rcan1-Flna pathway may underlie PH pathogenesis.
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29
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Regulator of Calcineurin 1-1L Protects Cardiomyocytes Against Hypoxia-induced Apoptosis via Mitophagy. J Cardiovasc Pharmacol 2014; 64:310-7. [DOI: 10.1097/fjc.0000000000000121] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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30
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RCAN1 regulates mitochondrial function and increases susceptibility to oxidative stress in mammalian cells. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2014; 2014:520316. [PMID: 25009690 PMCID: PMC4070399 DOI: 10.1155/2014/520316] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 05/06/2014] [Indexed: 12/02/2022]
Abstract
Mitochondria are the primary site of cellular energy generation and reactive oxygen species (ROS) accumulation. Elevated ROS levels are detrimental to normal cell function and have been linked to the pathogenesis of neurodegenerative disorders such as Down's syndrome (DS) and Alzheimer's disease (AD). RCAN1 is abundantly expressed in the brain and overexpressed in brain of DS and AD patients. Data from nonmammalian species indicates that increased RCAN1 expression results in altered mitochondrial function and that RCAN1 may itself regulate neuronal ROS production. In this study, we have utilized mice overexpressing RCAN1 (RCAN1ox) and demonstrate an increased susceptibility of neurons from these mice to oxidative stress. Mitochondria from these mice are more numerous and smaller, indicative of mitochondrial dysfunction, and mitochondrial membrane potential is altered under conditions of oxidative stress. We also generated a PC12 cell line overexpressing RCAN1 (PC12RCAN1). Similar to RCAN1ox neurons, PC12RCAN1 cells have an increased susceptibility to oxidative stress and produce more mitochondrial ROS. This study demonstrates that increasing RCAN1 expression alters mitochondrial function and increases the susceptibility of neurons to oxidative stress in mammalian cells. These findings further contribute to our understanding of RCAN1 and its potential role in the pathogenesis of neurodegenerative disorders such as AD and DS.
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31
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Wu Y, Ly PTT, Song W. Aberrant expression of RCAN1 in Alzheimer's pathogenesis: a new molecular mechanism and a novel drug target. Mol Neurobiol 2014; 50:1085-97. [PMID: 24752590 DOI: 10.1007/s12035-014-8704-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 03/31/2014] [Indexed: 01/08/2023]
Abstract
AD, a devastating neurodegenerative disorder, is the most common cause of dementia in the elderly. Patients with AD are characterized by three hallmarks of neuropathology including neuritic plaque deposition, neurofibrillary tangle formation, and neuronal loss. Growing evidences indicate that dysregulation of regulator of calcineurin 1 (RCAN1) plays an important role in the pathogenesis of AD. Aberrant RCAN1 expression facilitates neuronal apoptosis and Tau hyperphosphorylation, leading to neuronal loss and neurofibrillary tangle formation. This review aims to describe the recent advances of the regulation of RCAN1 expression and its physiological functions. Moreover, the AD risk factors-induced RCAN1 dysregulation and its role in promoting neuronal loss, synaptic impairments and neurofibrillary tangle formation are summarized. Furthermore, we provide an outlook into the effects of RCAN1 dysregulation on APP processing, Aβ generation and neuritic plaque formation, and the possible underlying mechanisms, as well as the potential of targeting RCAN1 as a new therapeutic approach.
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Affiliation(s)
- Yili Wu
- Townsend Family Laboratories, Department of Psychiatry, Brain Research Center, Graduate Program in Neuroscience, The University of British Columbia, 2255 Wesbrook Mall, Vancouver, BC, Canada, V6T 1Z3
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32
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Sun X, Wu Y, Herculano B, Song W. RCAN1 overexpression exacerbates calcium overloading-induced neuronal apoptosis. PLoS One 2014; 9:e95471. [PMID: 24751678 PMCID: PMC3994074 DOI: 10.1371/journal.pone.0095471] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 03/26/2014] [Indexed: 01/23/2023] Open
Abstract
Down Syndrome (DS) patients develop characteristic Alzheimer's Disease (AD) neuropathology after their middle age. Prominent neuronal loss has been observed in the cortical regions of AD brains. However, the underlying mechanism leading to this neuronal loss in both DS and AD remains to be elucidated. Calcium overloading and oxidative stress have been implicated in AD pathogenesis. Two major isoforms of regulator of calcineurin 1 (RCAN1), RCAN1.1 and RCAN1.4, are detected in human brains. In this report we defined the transcriptional regulation of RCAN1.1 and RCAN1.4 by two alternative promoters. Calcium overloading upregulated RCAN1.4 expression by activating RCAN1.4 promoter through calcineurin-NFAT signaling pathway, thus forming a negative feedback loop in isoform 4 regulation. Furthermore, RCAN1.4 overexpression exacerbated calcium overloading-induced neuronal apoptosis, which was mediated by caspase-3 apoptotic pathway. Our results suggest that downregulating RCAN1.4 expression in neurons could be beneficial to AD patients.
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Affiliation(s)
- Xiulian Sun
- Qilu Hospital of Shandong University, Jinan, China
- Townsend Family Laboratories, Department of Psychiatry, Brain Research Center, Graduate Program in Neuroscience, The University of British Columbia, Vancouver, Canada
| | - Yili Wu
- Chongqing City Key Lab of Translational Medical Research in Cognitive Development and Learning and Memory Disorders, and Ministry of Education Key Laboratory of Child Development and Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China
- Townsend Family Laboratories, Department of Psychiatry, Brain Research Center, Graduate Program in Neuroscience, The University of British Columbia, Vancouver, Canada
| | - Bruno Herculano
- Townsend Family Laboratories, Department of Psychiatry, Brain Research Center, Graduate Program in Neuroscience, The University of British Columbia, Vancouver, Canada
| | - Weihong Song
- Chongqing City Key Lab of Translational Medical Research in Cognitive Development and Learning and Memory Disorders, and Ministry of Education Key Laboratory of Child Development and Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China
- Townsend Family Laboratories, Department of Psychiatry, Brain Research Center, Graduate Program in Neuroscience, The University of British Columbia, Vancouver, Canada
- * E-mail:
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33
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Perluigi M, Pupo G, Tramutola A, Cini C, Coccia R, Barone E, Head E, Butterfield DA, Di Domenico F. Neuropathological role of PI3K/Akt/mTOR axis in Down syndrome brain. Biochim Biophys Acta Mol Basis Dis 2014; 1842:1144-53. [PMID: 24735980 DOI: 10.1016/j.bbadis.2014.04.007] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 03/19/2014] [Accepted: 04/07/2014] [Indexed: 01/11/2023]
Abstract
Down syndrome (DS) is the most frequent genetic cause of intellectual disability characterized by the presence of three copies of chromosome 21 (Chr21). Individuals with DS have sufficient neuropathology for a diagnosis of Alzheimer's disease (AD) after the age of 40years. The aim of our study is to gain new insights in the molecular mechanisms impaired in DS subjects that eventually lead to the development of dementia. We evaluate the PI3K/Akt/mTOR axis in the frontal cortex from DS cases (under the age of 40years) and DS with AD neuropathology compared with age-matched controls (Young and Old). The PI3K/Akt/mTOR axis may control several key pathways involved in AD that, if aberrantly regulated, affect amyloid beta (Aβ) deposition and tau phosphorylation. Our results show a hyperactivation of PI3K/Akt/mTOR axis in individuals with DS, with and without AD pathology, in comparison with respective controls. The PI3K/Akt/mTOR deregulation results in decreased autophagy, inhibition of IRS1 and GSK3β activity. Moreover, our data suggest that aberrant activation of the PI3K/Akt/mTOR axis acts in parallel to RCAN1 in phosphorylating tau, in DS and DS/AD. In conclusion, this study provides insights into the neuropathological mechanisms that may be engaged during the development of AD in DS. We suggest that deregulation of this signaling cascade is already evident in young DS cases and persist in the presence of AD pathology. The impairment of the PI3K/Akt/mTOR axis in DS population might represent a key-contributing factor to the neurodegenerative process that culminates in Alzheimer-like dementia.
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Affiliation(s)
- Marzia Perluigi
- Department of Biochemical Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Gilda Pupo
- Department of Biochemical Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Antonella Tramutola
- Department of Biochemical Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Chiara Cini
- Department of Biochemical Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Raffaella Coccia
- Department of Biochemical Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Eugenio Barone
- Department of Biochemical Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Elizabeth Head
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY 40506-0055, USA
| | - D Allan Butterfield
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY 40506-0055, USA; Department of Chemistry and Center of Membrane Sciences, University of Kentucky, Lexington, KY 40506-0055, USA
| | - Fabio Di Domenico
- Department of Biochemical Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy.
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Gimeno A, García-Giménez JL, Audí L, Toran N, Andaluz P, Dasí F, Viña J, Pallardó FV. Decreased cell proliferation and higher oxidative stress in fibroblasts from Down Syndrome fetuses. Preliminary study. Biochim Biophys Acta Mol Basis Dis 2014; 1842:116-25. [DOI: 10.1016/j.bbadis.2013.10.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 10/25/2013] [Accepted: 10/27/2013] [Indexed: 01/03/2023]
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Raghupathi R, Duffield MD, Zelkas L, Meedeniya A, Brookes SJH, Sia TC, Wattchow DA, Spencer NJ, Keating DJ. Identification of unique release kinetics of serotonin from guinea-pig and human enterochromaffin cells. J Physiol 2013; 591:5959-75. [PMID: 24099799 PMCID: PMC3872764 DOI: 10.1113/jphysiol.2013.259796] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 10/02/2013] [Indexed: 12/21/2022] Open
Abstract
The major source of serotonin (5-HT) in the body is the enterochromaffin (EC) cells lining the intestinal mucosa of the gastrointestinal tract. Despite the fact that EC cells synthesise ∼95% of total body 5-HT, and that this 5-HT has important paracrine and endocrine roles, no studies have investigated the mechanisms of 5-HT release from single primary EC cells. We have developed a rapid primary culture of guinea-pig and human EC cells, allowing analysis of single EC cell function using electrophysiology, electrochemistry, Ca(2+) imaging, immunocytochemistry and 3D modelling. Ca(2+) enters EC cells upon stimulation and triggers quantal 5-HT release via L-type Ca(2+) channels. Real time amperometric techniques reveal that EC cells release 5-HT at rest and this release increases upon stimulation. Surprisingly for an endocrine cell storing 5-HT in large dense core vesicles (LDCVs), EC cells release 70 times less 5-HT per fusion event than catecholamine released from similarly sized LDCVs in endocrine chromaffin cells, and the vesicle release kinetics instead resembles that observed in mammalian synapses. Furthermore, we measured EC cell density along the gastrointestinal tract to create three-dimensional (3D) simulations of 5-HT diffusion using the minimal number of variables required to understand the physiological relevance of single cell 5-HT release in the whole-tissue milieu. These models indicate that local 5-HT levels are likely to be maintained around the activation threshold for mucosal 5-HT receptors and that this is dependent upon stimulation and location within the gastrointestinal tract. This is the first study demonstrating single cell 5-HT release in primary EC cells. The mode of 5-HT release may represent a unique mode of exocytosis amongst endocrine cells and is functionally relevant to gastrointestinal sensory and motor function.
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Affiliation(s)
- Ravinarayan Raghupathi
- D. Keating: Department of Human Physiology and Centre for Neuroscience, Flinders University, Sturt Road, Adelaide, 5001, Australia.
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Ermak G, Davies KJA. Chronic high levels of the RCAN1-1 protein may promote neurodegeneration and Alzheimer disease. Free Radic Biol Med 2013; 62:47-51. [PMID: 23369757 PMCID: PMC4720382 DOI: 10.1016/j.freeradbiomed.2013.01.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Revised: 12/28/2012] [Accepted: 01/17/2013] [Indexed: 02/07/2023]
Abstract
The RCAN1 gene encodes three different protein isoforms: RCAN1-4, RCAN1-1L, and RCAN1-1S. RCAN1-1L is the RCAN1 isoform predominantly expressed in human brains. RCAN1 proteins have been shown to regulate various other proteins and cellular functions, including calcineurin, glycogen synthase kinase-3β (GSK-3β), the mitochondrial adenine nucleotide transporter (ANT), stress adaptation, ADP/ATP exchange in mitochondria, and the mitochondrial permeability transition pore (mtPTP). The effects of increased RCAN1 gene expression seem to depend both on the specific RCAN1 protein isoform(s) synthesized and on the length of time the level of each isoform is elevated. Transiently elevated RCAN1-4 and RCAN1-1L protein levels, lasting just a few hours, can be neuroprotective under acute stress conditions, including acute oxidative stress. We propose that, by transiently inhibiting the phosphatase calcineurin, RCAN1-4 and RCAN1-1L may reinforce and extend protective stress-adaptive cell responses. In contrast, prolonged elevation of RCAN1-1L levels is associated with the types of neurodegeneration observed in several diseases, including Alzheimer disease and Down syndrome. RCAN1-1L levels can also be increased by multiple chronic stresses and by glucocorticoids, both of which can cause neurodegeneration. Although increasing levels of RCAN1-1L for just a few months has no overtly obvious neurodegenerative effect, it does suppress neurogenesis. Longer term elevation of RCAN1-1L levels (for at least 16 months), however, can lead to the first signs of neurodegeneration. Such neurodegeneration may be precipitated by (RCAN1-1L-mediated) prolonged calcineurin inhibition and GSK-3β induction/activation, both of which promote tau hyperphosphorylation, and/or by (RCAN1-1L-mediated) effects on the mitochondrial ANT, diminished ATP/ADP ratio, opening of the mtPTP, and mitochondrial autophagy. We propose that RCAN1-1L operates through various molecular mechanisms, primarily dependent upon the length of time protein levels are elevated. We also suggest that models analyzing long-term RCAN1 gene overexpression may help us to understand the molecular mechanisms of neurodegeneration in diseases such as Alzheimer disease, Down syndrome, and possibly others.
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Affiliation(s)
- Gennady Ermak
- Ethel Percy Andrus Gerontology Center, Davis School of Gerontology, and Division of Molecular & Computational Biology, Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA 90089-0191, USA
| | - Kelvin J A Davies
- Ethel Percy Andrus Gerontology Center, Davis School of Gerontology, and Division of Molecular & Computational Biology, Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA 90089-0191, USA.
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Ghosh J, Liu X, Gillis KD. Electroporation followed by electrochemical measurement of quantal transmitter release from single cells using a patterned microelectrode. LAB ON A CHIP 2013; 13:2083-2090. [PMID: 23598689 PMCID: PMC3698871 DOI: 10.1039/c3lc41324a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
An electrochemical microelectrode located immediately adjacent to a single neuroendocrine cell can record spikes of amperometric current that result from exocytosis of oxidizable transmitter from individual vesicles, i.e., quantal exocytosis. Here, we report the development of an efficient method where the same electrochemical microelectrode is used to electropermeabilize an adjacent chromaffin cell and then measure the consequent quantal catecholamine release using amperometry. Trains of voltage pulses, 5-7 V in amplitude and 0.1-0.2 ms in duration, were used to reliably trigger release from cells using gold electrodes. Amperometric spikes induced by electropermeabilization had similar areas, peak heights and durations as amperometric spikes elicited by depolarizing high K(+) solutions, therefore release occurs from individual secretory granules. Uptake of trypan blue stain into cells demonstrated that the plasma membrane is permeabilized by the voltage stimulus. Voltage pulses did not degrade the electrochemical sensitivity of the electrodes assayed using a test analyte. Surprisingly, robust quantal release was elicited upon electroporation in the absence of Ca(2+) in the bath solution (0 Ca(2+)/5 mM EGTA). In contrast, electropermeabilization-induced transmitter release required Cl(-) in the bath solution in that bracketed experiments demonstrated a steep dependence of the rate of electropermeabilization-induced transmitter release on [Cl(-)] between 2 and 32 mM. Using the same electrochemical electrode to electroporate and record quantal release of catecholamines from an individual chromaffin cell allows precise timing of the stimulus, stimulation of a single cell at a time, and can be used to load membrane-impermeant substances into a cell.
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Martin KR, Layton D, Seach N, Corlett A, Barallobre MJ, Arbonés ML, Boyd RL, Scott B, Pritchard MA. Upregulation of RCAN1 causes Down syndrome-like immune dysfunction. J Med Genet 2013; 50:444-54. [PMID: 23644448 DOI: 10.1136/jmedgenet-2013-101522] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND People with Down syndrome (DS) are more susceptible to infections and autoimmune disease, but the molecular genetic basis for these immune defects remains undetermined. In this study, we tested whether increased expression of the chromosome 21 gene RCAN1 contributes to immune dysregulation. METHODS We investigated the immune phenotype of a mouse model that overexpresses RCAN1. RCAN1 transgenic (TG) mice exhibit T cell abnormalities that bear a striking similarity to the abnormalities described in individuals with DS. RESULTS RCAN1-TG mice display T cell developmental defects in the thymus and peripheral immune tissues. Thymic cellularity is reduced by substantial losses of mature CD4 and CD8 thymocytes and medullary epithelium. In peripheral immune organs T lymphocytes are reduced in number and exhibit reduced proliferative capacity and aberrant cytokine production. These T cell defects are stem cell intrinsic in that transfer of wild type bone marrow into RCAN1-TG recipients restored medullary thymic epithelium and T cell numbers in the thymus, spleen and lymph nodes. However, bone marrow transplantation failed to improve T cell function, suggesting an additional role for RCAN1 in the non-haemopoietic compartment. CONCLUSIONS RCAN1 therefore facilitates T cell development and function, and when overexpressed, may contribute to immune dysfunction in DS.
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Affiliation(s)
- Katherine R Martin
- Department Biochemistry and Molecular Biology, Monash University, Wellington Rd, Clayton, VIC 3800, Australia
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Emerging roles for intersectin (ITSN) in regulating signaling and disease pathways. Int J Mol Sci 2013; 14:7829-52. [PMID: 23574942 PMCID: PMC3645719 DOI: 10.3390/ijms14047829] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 04/02/2013] [Accepted: 04/03/2013] [Indexed: 01/10/2023] Open
Abstract
Intersectins (ITSNs) represent a family of multi-domain adaptor proteins that regulate endocytosis and cell signaling. ITSN genes are highly conserved and present in all metazoan genomes examined thus far. Lower eukaryotes have only one ITSN gene, whereas higher eukaryotes have two ITSN genes. ITSN was first identified as an endocytic scaffold protein, and numerous studies reveal a conserved role for ITSN in endocytosis. Subsequently, ITSNs were found to regulate multiple signaling pathways including receptor tyrosine kinases (RTKs), GTPases, and phosphatidylinositol 3-kinase Class 2beta (PI3KC2β). ITSN has also been implicated in diseases such as Down Syndrome (DS), Alzheimer Disease (AD), and other neurodegenerative disorders. This review summarizes the evolutionary conservation of ITSN, the latest research on the role of ITSN in endocytosis, the emerging roles of ITSN in regulating cell signaling pathways, and the involvement of ITSN in human diseases such as DS, AD, and cancer.
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Zanin MP, Mackenzie KD, Peiris H, Pritchard MA, Keating DJ. RCAN1 regulates vesicle recycling and quantal release kinetics via effects on calcineurin activity. J Neurochem 2013; 124:290-9. [PMID: 23134420 DOI: 10.1111/jnc.12086] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 10/11/2012] [Accepted: 11/06/2012] [Indexed: 11/29/2022]
Abstract
We have previously shown that Regulator of Calcineurin 1 (RCAN1) regulates multiple stages of vesicle exocytosis. However, the mechanisms by which RCAN1 affects secretory vesicle exocytosis and quantal release kinetics remain unknown. Here, we use carbon fibre amperometry to detect exocytosis from chromaffin cells and identify these underlying mechanisms. We observe reduced exocytosis with repeated stimulations in chromaffin cells over-expressing RCAN1 (RCAN1(ox)), but not in wild-type (WT) cells, indicating a negative effect of RCAN1 on vesicle recycling and endocytosis. Acute exposure to calcineurin inhibitors, cyclosporine A and FK-506, replicates this effect in WT cells but has no additional effect in RCAN1(ox) cells. When we chronically expose WT cells to cyclosporine A and FK-506 we find that catecholamine release per vesicle and pre-spike foot (PSF) signal parameters are decreased, similar to that in RCAN1(ox) cells. Inhibiting calcineurin activity in RCAN1(ox) cells has no additional effect on the amount of catecholamine release per vesicle but further reduces PSF signal parameters. Although electron microscopy studies indicate these changes are not because of altered vesicle number or distribution in RCAN1(ox) cells, the smaller vesicle and dense core size we observe in RCAN1(ox) cells may underlie the reduced quantal release in these cells. Thus, our results indicate that RCAN1 most likely affects vesicle recycling and quantal release kinetics via the inhibition of calcineurin activity.
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Affiliation(s)
- Mark P Zanin
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia
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Liu H, Tu L, Wang Q, Sun Y, Ma Y, Cen J, Wei Q, Luo J. Modulation of calcineurin activity in mouse brain by chronic oral administration of cyclosporine A. IUBMB Life 2013; 65:445-53. [DOI: 10.1002/iub.1139] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 01/07/2013] [Indexed: 12/11/2022]
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Duncan C, Bica L, Crouch PJ, Caragounis A, Lidgerwood GE, Parker SJ, Meyerowitz J, Volitakis I, Liddell JR, Raghupathi R, Paterson BM, Duffield MD, Cappai R, Donnelly PS, Grubman A, Camakaris J, Keating DJ, White AR. Copper modulates the large dense core vesicle secretory pathway in PC12 cells. Metallomics 2013; 5:700-14. [DOI: 10.1039/c3mt20231c] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Peiris H, Raghupathi R, Jessup CF, Zanin MP, Mohanasundaram D, Mackenzie KD, Chataway T, Clarke JN, Brealey J, Coates PT, Pritchard MA, Keating DJ. Increased expression of the glucose-responsive gene, RCAN1, causes hypoinsulinemia, β-cell dysfunction, and diabetes. Endocrinology 2012; 153:5212-21. [PMID: 23011918 DOI: 10.1210/en.2011-2149] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
RCAN1 is a chromosome 21 gene that controls secretion in endocrine cells, regulates mitochondrial function, and is sensitive to oxidative stress. Regulator of calcineurin 1 (RCAN1) is also an endogenous inhibitor of the protein phosphatase calcineurin, the inhibition of which leads to hypoinsulinemia and diabetes in humans and mice. However, the presence or the role of RCAN1 in insulin-secreting β-cells and its potential role in the pathogenesis of diabetes is unknown. Hence, the aim of this study is to investigate the presence of RCAN1 in β-cells and identify its role in β-cell function. RCAN1 is expressed in mouse islets and in the cytosol of pancreatic β-cells. We find RCAN1 is a glucose-responsive gene with a 1.5-fold increase in expression observed in pancreatic islets in response to chronic hyperglycemia. The overexpression of the human RCAN1.1 isoform in mice under the regulation of its endogenous promoter causes diabetes, age-associated hyperglycemia, reduced glucose tolerance, hypoinsulinemia, loss of β-cells, reduced β-cell insulin secretion, aberrant mitochondrial reactive oxygen species production, and the down-regulation of key β-cell genes. Our data therefore identifies a novel molecular link between the overexpression of RCAN1 and β-cell dysfunction. The glucose-responsive nature of RCAN1 provides a potential mechanism of action associated with the β-cell dysfunction observed in diabetes.
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Affiliation(s)
- Heshan Peiris
- Flinders Medical Science and Technology and Centre for Neuroscience, Flinders University, Adelaide, Australia
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Brait VH, Martin KR, Corlett A, Broughton BRS, Kim HA, Thundyil J, Drummond GR, Arumugam TV, Pritchard MA, Sobey CG. Over-expression of DSCR1 protects against post-ischemic neuronal injury. PLoS One 2012; 7:e47841. [PMID: 23144708 PMCID: PMC3483156 DOI: 10.1371/journal.pone.0047841] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 09/21/2012] [Indexed: 01/27/2023] Open
Abstract
Background and Purpose The Down syndrome candidate region 1 (DSCR1) gene is located on human chromosome 21 and its protein is over-expressed in brains of Down syndrome individuals. DSCR1 can modulate the activity of calcineurin, a phosphatase abundant in the brain, but its influence on stroke outcome is not clear. We compared stroke outcome in wildtype (WT) and transgenic (DSCR1-TG) mice which over-express isoform 1 of human DSCR1. Methods Transient cerebral ischemia was produced by occlusion of the middle cerebral artery for 0.5 h. After 23.5 h reperfusion, we assessed neurological impairment, brain infarct and edema volume, leukocyte infiltration and markers of inflammation. Intrinsic resistance to apoptosis following glucose deprivation was also assessed in primary cultures of WT and DSCR1-TG neurons. Results In contrast to WT, DSCR1-TG mice had an improved neurological deficit score, greater grip strength, attenuated infarct volume and brain swelling, and lacked hippocampal lesions after stroke. Expression of mouse DSCR1-1, but not DSCR1-4, mRNA and protein was increased by ischemia in both WT and DSCR1-TG. Brain calcineurin activity was increased to a similar degree after ischemia in each genotype. DSCR1-TG mice had fewer infiltrating neutrophils and activated microglia compared with WT, in association with an attenuated upregulation of several pro-inflammatory genes. Neurons from DSCR1-TG mice were more resistant than WT neurons to apoptotic cell death following 24 h of glucose deprivation. Conclusions Over-expression of DSCR1 in mice improves outcome following stroke. Mechanisms underlying this protection may involve calcineurin-independent, anti-inflammatory and anti-apoptotic effects mediated by DSCR1 in neurons.
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Affiliation(s)
- Vanessa H. Brait
- Vascular Biology and Immunopharmacology Group, Department of Pharmacology, Monash University, Clayton, Victoria, Australia
| | - Katherine R. Martin
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Alicia Corlett
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Brad R. S. Broughton
- Vascular Biology and Immunopharmacology Group, Department of Pharmacology, Monash University, Clayton, Victoria, Australia
| | - Hyun Ah Kim
- Vascular Biology and Immunopharmacology Group, Department of Pharmacology, Monash University, Clayton, Victoria, Australia
| | - John Thundyil
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Grant R. Drummond
- Vascular Biology and Immunopharmacology Group, Department of Pharmacology, Monash University, Clayton, Victoria, Australia
| | - Thiruma V. Arumugam
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Melanie A. Pritchard
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
- * E-mail:
| | - Christopher G. Sobey
- Vascular Biology and Immunopharmacology Group, Department of Pharmacology, Monash University, Clayton, Victoria, Australia
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Wu Y, Song W. Regulation of RCAN1 translation and its role in oxidative stress-induced apoptosis. FASEB J 2012; 27:208-21. [PMID: 23038757 DOI: 10.1096/fj.12-213124] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Abnormal expression of regulator of calcineurin 1 (RCAN1) has been implicated in Alzheimer's disease (AD) and Down's syndrome (DS). There are two major isoforms of RCAN1, isoforms 1 and 4. RCAN1 isoform 1 is predominantly expressed in the brain, particularly in neurons. In this report, we showed that there are two translation start codons in RCAN1 exon 1 serving as a functional translation initiation site to generate a longer 41-kDa isoform 1 (RCAN1.1L) and a shorter 31-kDa isoform 1 (RCAN1.1S). The first translation initiation site has higher translation efficiency than the downstream second one, and the translation initiation of two AUG sites is by a Cap-dependent mechanism. Short-term expression of RCAN1.1L protected SH-SY5Y cells from oxidative stress-induced apoptosis by inhibiting caspase-3 activation. However, long-term accumulation of RCAN1.1L in SH-SY5Y cells promoted oxidative stress-induced apoptosis via caspase-3 activation, and terminal deoxynucleotidyl transferase dUTP nick end labeling assay showed that the apoptosis ratio was increased to 499.03 ± 47.56% in SH-1.1L cells compared with 283.93 ± 28.66% in control cells. Furthermore, we found that RCAN1.1L is significantly elevated in the AD brains and patients with DS. RCAN1.1S is expressed at a low level in both human cells and brain tissues. Our results defined the regulatory mechanism underlying RCAN1 expression and the roles of RCAN1.1 in oxidative stress-induced neurodegeneration in AD and DS pathogenesis.
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Affiliation(s)
- Yili Wu
- Chongqing City Key Lab of Translational Medical Research in Cognitive Development and Learning and Memory Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China
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Exocytosis is impaired in mucopolysaccharidosis IIIA mouse chromaffin cells. Neuroscience 2012; 227:110-8. [PMID: 23022219 DOI: 10.1016/j.neuroscience.2012.09.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 08/28/2012] [Accepted: 09/13/2012] [Indexed: 11/22/2022]
Abstract
Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disorder caused by a deficiency in the activity of the lysosomal hydrolase, sulphamidase, an enzyme involved in the degradation of heparan sulphate. MPS IIIA patients exhibit progressive mental retardation and behavioural disturbance. While neuropathology is the major clinical problem in MPS IIIA patients, there is little understanding of how lysosomal storage generates this phenotype. As reduced neuronal communication can underlie cognitive deficiencies, we investigated whether the secretion of neurotransmitters is altered in MPS IIIA mice; utilising adrenal chromaffin cells, a classical model for studying secretion via exocytosis. MPS IIIA chromaffin cells displayed heparan sulphate storage and electron microscopy revealed large electron-lucent storage compartments. There were also increased numbers of large/elongated chromaffin granules, with a morphology that was similar to immature secretory granules. Carbon fibre amperometry illustrated a significant decrease in the number of exocytotic events for MPS IIIA, when compared to control chromaffin cells. However, there were no changes in the kinetics of release, the amount of catecholamine released per exocytotic event, or the amount of Ca(2+) entry upon stimulation. The increased number of large/elongated granules and reduced number of exocytotic events suggests that either the biogenesis and/or the cell surface docking and fusion potential of these vesicles is impaired in MPS IIIA. If this also occurs in central nervous system neurons, the reduction in neurotransmitter release could help to explain the development of neuropathology in MPS IIIA.
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Herault Y, Duchon A, Velot E, Maréchal D, Brault V. The in vivo Down syndrome genomic library in mouse. PROGRESS IN BRAIN RESEARCH 2012; 197:169-97. [PMID: 22541293 DOI: 10.1016/b978-0-444-54299-1.00009-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Mouse models are key elements to better understand the genotype-phenotype relationship and the physiopathology of Down syndrome (DS). Even though the mouse will never recapitulate the whole spectrum of intellectual disabilities observed in the DS, mouse models have been developed over the recent decades and have been used extensively to identify homologous genes or entire regions homologous to the human chromosome 21 (Hsa21) that are necessary or sufficient to induce DS cognitive features. In this chapter, we review the principal mouse DS models which have been selected and engineered over the years either for large genomic regions or for a few or a single gene of interest. Their analyses highlight the complexity of the genetic interactions that are involved in DS cognitive phenotypes and also strengthen the hypothesis on the multigenic nature of DS. This review also addresses future research challenges relative to the making of new models and their combination to go further in the characterization of candidates and modifier of the DS features.
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Affiliation(s)
- Yann Herault
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Translational medicine and Neurogenetics program, IGBMC, CNRS, INSERM, Université de Strasbourg, UMR7104, UMR964, Illkirch, Strasbourg, France.
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Martin KR, Corlett A, Dubach D, Mustafa T, Coleman HA, Parkington HC, Merson TD, Bourne JA, Porta S, Arbonés ML, Finkelstein DI, Pritchard MA. Over-expression of RCAN1 causes Down syndrome-like hippocampal deficits that alter learning and memory. Hum Mol Genet 2012; 21:3025-41. [PMID: 22511596 DOI: 10.1093/hmg/dds134] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
People with Down syndrome (DS) exhibit abnormal brain structure. Alterations affecting neurotransmission and signalling pathways that govern brain function are also evident. A large number of genes are simultaneously expressed at abnormal levels in DS; therefore, it is a challenge to determine which gene(s) contribute to specific abnormalities, and then identify the key molecular pathways involved. We generated RCAN1-TG mice to study the consequences of RCAN1 over-expression and investigate the contribution of RCAN1 to the brain phenotype of DS. RCAN1-TG mice exhibit structural brain abnormalities in those areas affected in DS. The volume and number of neurons within the hippocampus is reduced and this correlates with a defect in adult neurogenesis. The density of dendritic spines on RCAN1-TG hippocampal pyramidal neurons is also reduced. Deficits in hippocampal-dependent learning and short- and long-term memory are accompanied by a failure to maintain long-term potentiation (LTP) in hippocampal slices. In response to LTP induction, we observed diminished calcium transients and decreased phosphorylation of CaMKII and ERK1/2-proteins that are essential for the maintenance of LTP and formation of memory. Our data strongly suggest that RCAN1 plays an important role in normal brain development and function and its up-regulation likely contributes to the neural deficits associated with DS.
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Affiliation(s)
- Katherine R Martin
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, 3168 Victoria, Australia
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The use of mouse models for understanding the biology of down syndrome and aging. Curr Gerontol Geriatr Res 2012; 2012:717315. [PMID: 22461792 PMCID: PMC3296169 DOI: 10.1155/2012/717315] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2011] [Accepted: 12/06/2011] [Indexed: 12/16/2022] Open
Abstract
Down syndrome is a complex condition caused by trisomy of human chromosome 21. The biology of aging may be different in individuals with Down syndrome; this is not well understood in any organism. Because of its complexity, many aspects of Down syndrome must be studied either in humans or in animal models. Studies in humans are essential but are limited for ethical and practical reasons. Fortunately, genetically altered mice can serve as extremely useful models of Down syndrome, and progress in their production and analysis has been remarkable. Here, we describe various mouse models that have been used to study Down syndrome. We focus on segmental trisomies of mouse chromosome regions syntenic to human chromosome 21, mice in which individual genes have been introduced, or mice in which genes have been silenced by targeted mutagenesis. We selected a limited number of genes for which considerable evidence links them to aspects of Down syndrome, and about which much is known regarding their function. We focused on genes important for brain and cognitive function, and for the altered cancer spectrum seen in individuals with Down syndrome. We conclude with observations on the usefulness of mouse models and speculation on future directions.
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Garner CC, Wetmore DZ. Synaptic Pathology of Down Syndrome. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 970:451-68. [DOI: 10.1007/978-3-7091-0932-8_20] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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