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Schmiege P, Donnelly L, Elghobashi-Meinhardt N, Lee CH, Li X. Structure and inhibition of the human lysosomal transporter Sialin. Nat Commun 2024; 15:4386. [PMID: 38782953 PMCID: PMC11116495 DOI: 10.1038/s41467-024-48535-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 05/03/2024] [Indexed: 05/25/2024] Open
Abstract
Sialin, a member of the solute carrier 17 (SLC17) transporter family, is unique in its ability to transport not only sialic acid using a pH-driven mechanism, but also transport mono and diacidic neurotransmitters, such as glutamate and N-acetylaspartylglutamate (NAAG), into synaptic vesicles via a membrane potential-driven mechanism. While most transporters utilize one of these mechanisms, the structural basis of how Sialin transports substrates using both remains unclear. Here, we present the cryogenic electron-microscopy structures of human Sialin: apo cytosol-open, apo lumen-open, NAAG-bound, and inhibitor-bound. Our structures show that a positively charged cytosol-open vestibule accommodates either NAAG or the Sialin inhibitor Fmoc-Leu-OH, while its luminal cavity potentially binds sialic acid. Moreover, functional analyses along with molecular dynamics simulations identify key residues in binding sialic acid and NAAG. Thus, our findings uncover the essential conformational states in NAAG and sialic acid transport, demonstrating a working model of SLC17 transporters.
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Affiliation(s)
- Philip Schmiege
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Linda Donnelly
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | | | - Chia-Hsueh Lee
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Xiaochun Li
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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van Onselen R, Downing TG. Uptake of β-N-methylamino-L-alanine (BMAA) into glutamate-specific synaptic vesicles: Exploring the validity of the excitotoxicity mechanism of BMAA. Neurosci Lett 2024; 821:137593. [PMID: 38103629 DOI: 10.1016/j.neulet.2023.137593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 12/01/2023] [Accepted: 12/07/2023] [Indexed: 12/19/2023]
Abstract
The first mechanism of toxicity proposed for the cyanobacterial neurotoxin β-N-methylamino-L-alanine (BMAA) was excitotoxicity, and this was supported by numerous in vitro studies in which overactivation of both ionotropic and metabotropic glutamate receptors was reported. However, the excitotoxicity of BMAA is weak in comparison with other known excitotoxins and on par with that of glutamate, implying that to achieve sufficient synaptic concentrations of BMAA to cause classical in vivo excitotoxicity, BMAA must either accumulate in synapses to allow persistent glutamate receptor activation or it must be released in sufficiently high concentrations into synapses to cause the overexcitation. Since it has been shown that BMAA can be readily removed from synapses, release of high concentrations of BMAA into synapses must be shown to confirm its role as an excitotoxin in in vivo systems. This study therefore sought to evaluate the uptake of BMAA into synaptic vesicles and to determine if BMAA affects the uptake of glutamate into synaptic vesicles. There was no evidence to support uptake of BMAA into glutamate-specific synaptic vesicles but there was some indication that BMAA may affect the uptake of glutamate into synaptic vesicles. The uptake of BMAA into synaptic vesicles isolated from areas other than the cerebral cortex should be investigated before definite conclusions can be drawn about the role of BMAA as an excitotoxin.
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Affiliation(s)
- Rianita van Onselen
- Biomedical Research and Innovation Platform, South African Medical Research Council, Cape Town, South Africa; Department of Biochemistry and Microbiology, Nelson Mandela University, Gqeberha, South Africa
| | - Tim G Downing
- Department of Biochemistry and Microbiology, Nelson Mandela University, Gqeberha, South Africa.
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Altered sialin mRNA gene expression in type 2 diabetic male Wistar rats: implications for nitric oxide deficiency. Sci Rep 2023; 13:4013. [PMID: 36899088 PMCID: PMC10006425 DOI: 10.1038/s41598-023-31240-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 03/08/2023] [Indexed: 03/12/2023] Open
Abstract
Nitrate therapy has been suggested to boost nitric oxide (NO) levels in type 2 diabetes (T2D); however, little is known about nitrate transport across the membranes. This study aimed to assess changes in the mRNA expression of sialin, as a nitrate transporter, in the main tissues of rats with T2D. Rats were divided into two groups (n = 6/group): Control and T2D. A high-fat diet combined with a low dose of streptozotocin (STZ, 30 mg/kg) was used to induce T2D. At month 6, samples from the main tissues of rats were used to measure the mRNA expression of sialin and levels of NO metabolites. Rats with T2D had lower nitrate levels in the soleus muscle (66%), lung (48%), kidney (43%), aorta (30%), adrenal gland (58%), epididymal adipose tissue (eAT) (61%), and heart (37%) and had lower nitrite levels in the pancreas (47%), kidney (42%), aorta (33%), liver (28%), eAT (34%), and heart (32%). The order of sialin gene expression in control rats was: soleus muscle > kidney > pancreas > lung > liver > adrenal gland > brain > eAT > intestine > stomach > aorta > heart. Compared to controls, rats with T2D had higher sialin mRNA expressions in the stomach (2.1), eAT (2.0), adrenal gland (1.7), liver (8.9), and soleus muscle (3.4), and lower sialin expression in the intestine (0.56), pancreas (0.42), and kidney (0.44), all P values < 0.05. These findings indicate altered sialin mRNA expression in the main tissues of male T2D rats and may have implications for future NO-based treatment of T2D.
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Park DB, Kim L, Hwang JH, Kim KT, Park JE, Choi JS, An HJ. Temporal quantitative profiling of sialyllactoses and sialic acids after oral administration of sialyllactose to mini-pigs with osteoarthritis. RSC Adv 2023; 13:1115-1124. [PMID: 36686942 PMCID: PMC9811936 DOI: 10.1039/d2ra05912f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 12/21/2022] [Indexed: 01/06/2023] Open
Abstract
Sialyllactose (SL) is the most abundant acidic oligosaccharide in human breast milk and plays a primary role in various biological processes. Recently, SL has attracted attention as an excellent dietary supplement for arthritis because it is effective in cartilage protection and treatment. Despite the superior function of SL, there are few pharmacological studies of SL according to blood concentrations in arthritis models. In this study, we investigated quantitative changes in SL and sialic acids in the plasma obtained from mini-pigs with osteoarthritis throughout exogenous administration of SL using liquid chromatography-multiple reaction monitoring mass spectrometry. Plasma concentrations of SL and sialic acids in the SL-fed group showed a significant difference compared to the control group. Mini pigs were fed only Neu5Ac bound to SL, but the concentration patterns of the two types of sialic acid, Neu5Ac and Neu5Gc, were similar. In addition, the relative mRNA expression level of matrix metalloproteinases (MMPs), which is known as a critical factor in cartilage matrix degradation, was remarkably decreased in the synovial membrane of the SL-fed group. Consequently, the temporal quantitative profiling suggests that dietary SL can be metabolized and utilized in the body and may protect against cartilage degradation by suppressing MMP expression during osteoarthritis progression.
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Affiliation(s)
- Dan Bi Park
- GeneChem Inc.Yuseong-guDaejeon 34025Republic of Korea,Graduate School of Analytical Science and Technology, Chungnam National UniversityDaejeon 34134Republic of Korea
| | - Lila Kim
- GeneChem Inc.Yuseong-guDaejeon 34025Republic of Korea
| | - Jeong Ho Hwang
- Animal Model Research Group, Jeonbuk Branch Institute, Korea Institute of ToxicologyJeollabukdo56212Republic of Korea
| | - Kyung-Tai Kim
- Animal Model Research Group, Jeonbuk Branch Institute, Korea Institute of ToxicologyJeollabukdo56212Republic of Korea
| | - Ji Eun Park
- Graduate School of Analytical Science and Technology, Chungnam National UniversityDaejeon 34134Republic of Korea,Asia Glycomics Reference SiteDaejeon 34134Republic of Korea
| | - Jong-Soon Choi
- Graduate School of Analytical Science and Technology, Chungnam National UniversityDaejeon 34134Republic of Korea,Research Center for Materials Analysis, Korea Basic Science InstituteDaejeon34133Republic of Korea
| | - Hyun Joo An
- Graduate School of Analytical Science and Technology, Chungnam National UniversityDaejeon 34134Republic of Korea,Asia Glycomics Reference SiteDaejeon 34134Republic of Korea
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Abstract
The prevalence of cardiovascular and metabolic disease coupled with kidney dysfunction is increasing worldwide. This triad of disorders is associated with considerable morbidity and mortality as well as a substantial economic burden. Further understanding of the underlying pathophysiological mechanisms is important to develop novel preventive or therapeutic approaches. Among the proposed mechanisms, compromised nitric oxide (NO) bioactivity associated with oxidative stress is considered to be important. NO is a short-lived diatomic signalling molecule that exerts numerous effects on the kidneys, heart and vasculature as well as on peripheral metabolically active organs. The enzymatic L-arginine-dependent NO synthase (NOS) pathway is classically viewed as the main source of endogenous NO formation. However, the function of the NOS system is often compromised in various pathologies including kidney, cardiovascular and metabolic diseases. An alternative pathway, the nitrate-nitrite-NO pathway, enables endogenous or dietary-derived inorganic nitrate and nitrite to be recycled via serial reduction to form bioactive nitrogen species, including NO, independent of the NOS system. Signalling via these nitrogen species is linked with cGMP-dependent and independent mechanisms. Novel approaches to restoring NO homeostasis during NOS deficiency and oxidative stress have potential therapeutic applications in kidney, cardiovascular and metabolic disorders.
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A systemic study of indoxacarb resistance in Spodoptera litura revealed complex expression profiles and regulatory mechanism. Sci Rep 2019; 9:14997. [PMID: 31628365 PMCID: PMC6802196 DOI: 10.1038/s41598-019-51234-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 09/24/2019] [Indexed: 11/09/2022] Open
Abstract
The tobacco cutworm, Spodoptera litura, is an important pest of crop and vegetable plants worldwide, and its resistance to insecticides have quickly developed. However, the resistance mechanisms of this pest are still unclear. In this study, the change in mRNA and miRNA profiles in the susceptible, indoxacarb-resistant and field indoxacarb-resistant strains of S. litura were characterized. Nine hundred and ten co-up-regulated and 737 co-down-regulated genes were identified in the resistant strains. Further analysis showed that 126 co-differentially expressed genes (co-DEGs) (cytochrome P450, carboxy/cholinesterase, glutathione S-transferase, ATP-binding cassette transporter, UDP-glucuronosyl transferase, aminopeptidase N, sialin, serine protease and cuticle protein) may play important roles in indoxacarb resistance in S. litura. In addition, a total of 91 known and 52 novel miRNAs were identified, and 10 miRNAs were co-differentially expressed in the resistant strains of S. litura. Furthermore, 10 co-differentially expressed miRNAs (co-DEmiRNAs) had predicted co-DEGs according to the expected miRNA-mRNA negative regulation pattern and 37 indoxacarb resistance-related co-DEGs were predicted to be the target genes. These results not only broadened our understanding of molecular mechanisms of insecticide resistance by revealing complicated profiles, but also provide important clues for further study on the mechanisms of miRNAs involved in indoxacarb resistance in S. litura.
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Röhrig CH, Choi SSH, Baldwin N. The nutritional role of free sialic acid, a human milk monosaccharide, and its application as a functional food ingredient. Crit Rev Food Sci Nutr 2016; 57:1017-1038. [DOI: 10.1080/10408398.2015.1040113] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
| | - Sharon S. H. Choi
- Intertek Scientific & Regulatory Consultancy, Mississauga, Ontario, Canada
| | - Nigel Baldwin
- Intertek Scientific & Regulatory Consultancy, Hampshire, United Kingdom
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Villar-Cerviño V, Fernández-López B, Celina Rodicio M, Anadón R. Aspartate-containing neurons of the brainstem and rostral spinal cord of the sea lampreyPetromyzon marinus: Distribution and comparison with γ-aminobutyric acid. J Comp Neurol 2014; 522:1209-31. [DOI: 10.1002/cne.23493] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 10/29/2013] [Accepted: 10/29/2013] [Indexed: 12/26/2022]
Affiliation(s)
- Verona Villar-Cerviño
- Departamento de Biología Celular y Ecología; Facultad de Biología, Universidad de Santiago de Compostela; Santiago de Compostela 15782 Spain
| | - Blanca Fernández-López
- Departamento de Biología Celular y Ecología; Facultad de Biología, Universidad de Santiago de Compostela; Santiago de Compostela 15782 Spain
| | - María Celina Rodicio
- Departamento de Biología Celular y Ecología; Facultad de Biología, Universidad de Santiago de Compostela; Santiago de Compostela 15782 Spain
| | - Ramón Anadón
- Departamento de Biología Celular y Ecología; Facultad de Biología, Universidad de Santiago de Compostela; Santiago de Compostela 15782 Spain
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Van Liefferinge J, Massie A, Portelli J, Di Giovanni G, Smolders I. Are vesicular neurotransmitter transporters potential treatment targets for temporal lobe epilepsy? Front Cell Neurosci 2013; 7:139. [PMID: 24009559 PMCID: PMC3757300 DOI: 10.3389/fncel.2013.00139] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 08/11/2013] [Indexed: 12/18/2022] Open
Abstract
The vesicular neurotransmitter transporters (VNTs) are small proteins responsible for packing synaptic vesicles with neurotransmitters thereby determining the amount of neurotransmitter released per vesicle through fusion in both neurons and glial cells. Each transporter subtype was classically seen as a specific neuronal marker of the respective nerve cells containing that particular neurotransmitter or structurally related neurotransmitters. More recently, however, it has become apparent that common neurotransmitters can also act as co-transmitters, adding complexity to neurotransmitter release and suggesting intriguing roles for VNTs therein. We will first describe the current knowledge on vesicular glutamate transporters (VGLUT1/2/3), the vesicular excitatory amino acid transporter (VEAT), the vesicular nucleotide transporter (VNUT), vesicular monoamine transporters (VMAT1/2), the vesicular acetylcholine transporter (VAChT) and the vesicular γ-aminobutyric acid (GABA) transporter (VGAT) in the brain. We will focus on evidence regarding transgenic mice with disruptions in VNTs in different models of seizures and epilepsy. We will also describe the known alterations and reorganizations in the expression levels of these VNTs in rodent models for temporal lobe epilepsy (TLE) and in human tissue resected for epilepsy surgery. Finally, we will discuss perspectives on opportunities and challenges for VNTs as targets for possible future epilepsy therapies.
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Lines MA, Rupar CA, Rip JW, Baskin B, Ray PN, Hegele RA, Grynspan D, Michaud J, Geraghty MT. Infantile Sialic Acid Storage Disease: Two Unrelated Inuit Cases Homozygous for a Common Novel SLC17A5 Mutation. JIMD Rep 2013; 12:79-84. [PMID: 23900835 DOI: 10.1007/8904_2013_247] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 06/05/2013] [Accepted: 06/10/2013] [Indexed: 12/13/2022] Open
Abstract
Infantile sialic acid storage disease (ISSD) is a lysosomal storage disease characterized by accumulation of covalently unlinked (free) sialic acid in multiple tissues. ISSD and Salla disease (a predominantly neurological disorder) are allelic disorders caused by recessive mutations of a lysosomal anionic monosaccharide transporter, SLC17A5. While Salla disease is common in Finland due to a founder-effect mutation (p.Arg39Cys), ISSD is comparatively rare in all populations studied.Here, we describe the clinical and molecular features of two unrelated Canadian Inuit neonates with a virtually identical presentation of ISSD. Both individuals presented antenatally with fetal hydrops, dying shortly following delivery. Urinary free sialic acid excretion was markedly increased in the one case in which urine could be obtained for testing; postmortem examination showed a picture of widespread lysosomal storage in both. Both children were homozygous for a novel splice site mutation (NM_012434:c.526-2A>G) resulting in skipping of exon 4 and an ensuing frameshift. Analysis of a further 129 pan-Arctic Inuit controls demonstrated a heterozygous carrier rate of 1/129 (~0.4 %) in our sample. Interestingly, lysosomal enzyme studies showed an unexplained ninefold increase in neuraminidase activity, with lesser elevations in the activities of several other lysosomal enzymes. Our results raise the possibility of a common founder mutation presenting as hydrops in this population. Furthermore, if confirmed in subsequent cases, the marked induction of neuraminidase activity seen here may prove useful in the clinical diagnosis of ISSD.
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Affiliation(s)
- Matthew A Lines
- Division of Metabolics and Newborn Screening, University of Ottawa, Children's Hospital of Eastern Ontario, 401 Smyth Road, K1H 8L1, Ottawa, ON, Canada
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11
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Morland C, Nordengen K, Larsson M, Prolo LM, Farzampour Z, Reimer RJ, Gundersen V. Vesicular uptake and exocytosis of L-aspartate is independent of sialin. FASEB J 2012; 27:1264-74. [PMID: 23221336 DOI: 10.1096/fj.12-206300] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The mechanism of release and the role of l-aspartate as a central neurotransmitter are controversial. A vesicular release mechanism for l-aspartate has been difficult to prove, as no vesicular l-aspartate transporter was identified until it was found that sialin could transport l-aspartate and l-glutamate when reconstituted into liposomes. We sought to clarify the release mechanism of l-aspartate and the role of sialin in this process by combining l-aspartate uptake studies in isolated synaptic vesicles with immunocyotchemical investigations of hippocampal slices. We found that radiolabeled l-aspartate was taken up into synaptic vesicles. The vesicular l-aspartate uptake, relative to the l-glutamate uptake, was twice as high in the hippocampus as in the whole brain, the striatum, and the entorhinal and frontal cortices and was not inhibited by l-glutamate. We further show that sialin is not essential for exocytosis of l-aspartate, as there was no difference in ATP-dependent l-aspartate uptake in synaptic vesicles from sialin-knockout and wild-type mice. In addition, expression of sialin in PC12 cells did not result in significant vesicle uptake of l-aspartate, and depolarization-induced depletion of l-aspartate from hippocampal nerve terminals was similar in hippocampal slices from sialin-knockout and wild-type mice. Further, there was no evidence for nonvesicular release of l-aspartate via volume-regulated anion channels or plasma membrane excitatory amino acid transporters. This suggests that l-aspartate is exocytotically released from nerve terminals after vesicular accumulation by a transporter other than sialin.
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Affiliation(s)
- Cecilie Morland
- Department of Anatomy, University of Oslo, POB 1105 Blindern, 0317 Oslo, Norway
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Sialin (SLC17A5) functions as a nitrate transporter in the plasma membrane. Proc Natl Acad Sci U S A 2012; 109:13434-9. [PMID: 22778404 DOI: 10.1073/pnas.1116633109] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
In vivo recycling of nitrate (NO(3)(-)) and nitrite (NO(2)(-)) is an important alternative pathway for the generation of nitric oxide (NO) and maintenance of systemic nitrate-nitrite-NO balance. More than 25% of the circulating NO(3)(-) is actively removed and secreted by salivary glands. Oral commensal bacteria convert salivary NO(3)(-) to NO(2)(-), which enters circulation and leads to NO generation. The transporters for NO(3)(-) in salivary glands have not yet been identified. Here we report that sialin (SLC17A5), mutations in which cause Salla disease and infantile sialic acid storage disorder (ISSD), functions as an electrogenic 2NO(3)(-)/H(+) cotransporter in the plasma membrane of salivary gland acinar cells. We have identified an extracellular pH-dependent anion current that is carried by NO(3)(-) or sialic acid (SA), but not by Br(-), and is accompanied by intracellular acidification. Both responses were reduced by knockdown of sialin expression and increased by the plasma membrane-targeted sialin mutant (L22A-L23A). Fibroblasts from patients with ISSD displayed reduced SA- and NO(3)(-)-induced currents compared with healthy controls. Furthermore, expression of disease-associated sialin mutants in fibroblasts and salivary gland cells suppressed the H(+)-dependent NO(3)(-) conductance. Importantly, adenovirus-dependent expression of the sialinH183R mutant in vivo in pig salivary glands decreased NO(3)(-) secretion in saliva after intake of a NO(3)(-)-rich diet. Taken together, these data demonstrate that sialin mediates nitrate influx into salivary gland and other cell types. We suggest that the 2NO(3)(-)/H(+) transport function of sialin in salivary glands can contribute significantly to clearance of serum nitrate, as well as nitrate recycling and physiological nitrite-NO homeostasis.
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Kim E, Shino S, Yoon J, Leung HT. In search of proteins that are important for synaptic functions in Drosophila visual system. J Neurogenet 2012; 26:151-7. [PMID: 22283835 DOI: 10.3109/01677063.2011.648290] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This is the second of two reviews that include some of the studies we, members of the Pak laboratory and collaborators, did from 2000 to 2010 on the mutants that affect synaptic transmission in the Drosophila visual system. Of the five mutants we discuss, two turned out to also play roles in the larval neuromuscular junction. This review complements the one on phototransduction to give a fairly complete account of what we focused on during the 10-year period, although we also did some studies on photoreceptor degeneration in the early part of the decade. Besides showing the power of using a genetic approach to the study of synaptic transmission, the review contains some unexpected results that illustrate the serendipitous nature of research.
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Affiliation(s)
- Eunju Kim
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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Broadie K, Baumgartner S, Prokop A. Extracellular matrix and its receptors in Drosophila neural development. Dev Neurobiol 2011; 71:1102-30. [PMID: 21688401 PMCID: PMC3192297 DOI: 10.1002/dneu.20935] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Extracellular matrix (ECM) and matrix receptors are intimately involved in most biological processes. The ECM plays fundamental developmental and physiological roles in health and disease, including processes underlying the development, maintenance, and regeneration of the nervous system. To understand the principles of ECM-mediated functions in the nervous system, genetic model organisms like Drosophila provide simple, malleable, and powerful experimental platforms. This article provides an overview of ECM proteins and receptors in Drosophila. It then focuses on their roles during three progressive phases of neural development: (1) neural progenitor proliferation, (2) axonal growth and pathfinding, and (3) synapse formation and function. Each section highlights known ECM and ECM-receptor components and recent studies done in mutant conditions to reveal their in vivo functions, all illustrating the enormous opportunities provided when merging work on the nervous system with systematic research into ECM-related gene functions.
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Affiliation(s)
- Kendal Broadie
- Departments of Biological Sciences and Cell and Developmental Biology, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37232 USA
| | - Stefan Baumgartner
- Department of Experimental Medical Sciences, Lund University, BMC B12, 22184 Lund, Sweden
| | - Andreas Prokop
- Faculty of Life Sciences, Wellcome Trust Centre for Cell-Matrix Research, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
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Wickramasinghe S, Medrano JF. Primer on genes encoding enzymes in sialic acid metabolism in mammals. Biochimie 2011; 93:1641-6. [PMID: 21689720 DOI: 10.1016/j.biochi.2011.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Accepted: 06/03/2011] [Indexed: 11/18/2022]
Abstract
Sialic acid, a nine-carbon sugar acid usually is present in the non-reducing terminal position of free oligosaccharides and glycoconjugates. Sialylated conjugates in mammals perform important roles in cellular recognition, signaling, host-pathogen interaction and neuronal development. Metabolism of sialylated conjugates involves a complex pathway consisting of enzymes distributed among the different compartments in the cell. These enzymes are encoded by 32 genes diversely distributed throughout the mammalian genome. Genetic variants in some of these genes are associated with embryonic lethality and abnormal phenotypes in mice and neuromuscular diseases, carcinomas and immune-mediated diseases in humans. In humans, the CMP-NeuAc-hydroxylase (CMAH) enzyme is inactivated due to a deletion mutation in the encoded enzyme. This lack of Neu5Gc phenotype makes humans unique among mammals. This review focuses on genes encoding enzymes in sialic acid metabolism pathways in mammalian cells with special emphasis on the human, mouse and cow.
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Affiliation(s)
- Saumya Wickramasinghe
- Department of Animal Science, University of California-Davis, One Shields Ave., Davis, CA 95616-8521, USA
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He M, Lin F, Qin L, Zhou J, Yang G, Yang X, Wang S. Postnatal expression of sialin in the mouse submandibular gland. Arch Oral Biol 2011; 56:1333-8. [PMID: 21620373 DOI: 10.1016/j.archoralbio.2011.04.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 03/31/2011] [Accepted: 04/29/2011] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Sialin has been identified as a sialic acid and aspartate/glutamate transporter. Both cytoplasmic localization and the plasma membrane labelling pattern suggested that sialin may possess multiple transport functions in different cell types. In mouse embryos, sialin expression was primarily detected in the central nervous system. However, sialin shows widespread and high-level expression in adult tissues. Despite its ubiquitous expression and important functions, the postnatal expression profile and subcellular localization of sialin in the salivary gland remains elusive. The aim of the present study was to investigate the expression and subcellular distribution of sialin during postnatal development in the mouse submandibular gland (SMG). DESIGN Six SMGs from both female and male C57BL/6 mice were collected at P10, P30 and P90, and the material from each littermate of either sex was pooled to extract total RNA and tissue protein. The remaining tissues were immediately fixed in 10% neutral buffered formalin for histological analysis. The mRNA and protein expression levels of sialin were examined by quantitative real-time RT-PCR and Western blot analysis. The subcellular distribution of sialin was analysed by immunohistochemistry and immunofluorescence. RESULTS The postnatal expression level of sialin in the mouse SMG was comparable with that in brain at each time point tested. The temporal expression of sialin in the SMG gradually increased during postnatal maturation. Immunohistochemical and immunofluorescence analysis demonstrated that sialin was predominantly expressed on the basal cytoplasmic membrane of acini and ducts, as well as in some myoepithelial cells in the SMG. CONCLUSIONS The high-level expression and subcellular distribution pattern of sialin in the SMG suggest that sialin may play an important role in the transport and secretion of saliva.
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Affiliation(s)
- Miao He
- Salivary Gland Disease Center and Molecular Laboratory for Gene Therapy & Tooth Regeneration, Capital Medical University School of Stomatology, Tian Tan Xi Li No.4, Beijing 100050, China
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Moss J, Ungless MA, Bolam JP. Dopaminergic axons in different divisions of the adult rat striatal complex do not express vesicular glutamate transporters. Eur J Neurosci 2011; 33:1205-11. [PMID: 21375596 DOI: 10.1111/j.1460-9568.2011.07594.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Midbrain dopamine neurons signal rapid information about rewards and reward-related events. It has been suggested that this fast signal may, in fact, be conveyed by co-released glutamate. Evidence that dopamine neurons co-release glutamate comes largely from studies involving cultured neurons or tissue from young animals. Recently, however, it has been shown that this dual glutamatergic/dopaminergic phenotype declines with age, and can be induced by injury, suggesting that it is not a key feature of adult dopamine neurons. Here, we provide further support for this view by showing that dopaminergic axons and terminals in subregions of the adult striatum do not express vesicular glutamate transporters (VGluT1, VGluT2 or VGluT3). Striatal tissue from the adult rat was immunolabelled to reveal tyrosine hydroxylase (TH; biosynthetic enzyme of dopamine) and one of the three known VGluTs. Importantly, we compared the immunogold labelling for each of the VGluTs associated with TH-positive structures with background labelling at the electron microscopic level. In addition, we carried out a subregional analysis of the core and shell of the nucleus accumbens. We found that dopaminergic axons and terminals in the dorsolateral striatum and ventral striatum (nucleus accumbens core and shell) do not express VGluT1, VGluT2 or VGluT3. We conclude, therefore, that in the normal, adult rat striatum, dopaminergic axons do not co-release glutamate.
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Affiliation(s)
- Jonathan Moss
- Medical Research Council Anatomical Neuropharmacology Unit, Department of Pharmacology, University of Oxford, Oxford, UK.
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Abstract
The Ca(2+)-dependent release of aspartate from hippocampal preparations was first reported 35 years ago, but the functional significance of this process remains uncertain. Aspartate satisfies all the criteria normally required for identification of a CNS transmitter. It is synthesized in nerve terminals, is accumulated and stored in synaptic vesicles, is released by exocytosis upon nerve terminal depolarization, and activates postsynaptic NMDA receptors. Aspartate may be employed as a neuropeptide-like co-transmitter by pathways that release either glutamate or GABA as their principal transmitter. Aspartate mechanisms include vesicular transport by sialin, vesicular content sensitive to glucose concentration, release mainly outside the presynaptic active zones, and selective activation of extrasynaptic NR1-NR2B NMDA receptors. Possible neurobiological functions of aspartate in immature neurons include activation of cAMP-dependent gene transcription and in mature neurons inhibition of CREB function, reduced BDNF expression, and induction of excitotoxic neuronal death. Recent findings suggest new experimental approaches toward resolving the functional significance of aspartate release.
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Affiliation(s)
- J Victor Nadler
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
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Synaptic and vesicular coexistence of VGLUT and VGAT in selected excitatory and inhibitory synapses. J Neurosci 2010; 30:7634-45. [PMID: 20519538 DOI: 10.1523/jneurosci.0141-10.2010] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The segregation between vesicular glutamate and GABA storage and release forms the molecular foundation between excitatory and inhibitory neurons and guarantees the precise function of neuronal networks. Using immunoisolation of synaptic vesicles, we now show that VGLUT2 and VGAT, and also VGLUT1 and VGLUT2, coexist in a sizeable pool of vesicles. VGAT immunoisolates transport glutamate in addition to GABA. Furthermore, VGLUT activity enhances uptake of GABA and monoamines. Postembedding immunogold double labeling revealed that VGLUT1, VGLUT2, and VGAT coexist in mossy fiber terminals of the hippocampal CA3 area. Similarly, cerebellar mossy fiber terminals harbor VGLUT1, VGLUT2, and VGAT, while parallel and climbing fiber terminals exclusively contain VGLUT1 or VGLUT2, respectively. VGLUT2 was also observed in cerebellar GABAergic basket cells terminals. We conclude that the synaptic coexistence of vesicular glutamate and GABA transporters allows for corelease of both glutamate and GABA from selected nerve terminals, which may prevent systemic overexcitability by downregulating synaptic activity. Furthermore, our data suggest that VGLUT enhances transmitter storage in nonglutamatergic neurons. Thus, synaptic and vesicular coexistence of VGLUT and VGAT is more widespread than previously anticipated, putatively influencing fine-tuning and control of synaptic plasticity.
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Sreedharan S, Shaik JHA, Olszewski PK, Levine AS, Schiöth HB, Fredriksson R. Glutamate, aspartate and nucleotide transporters in the SLC17 family form four main phylogenetic clusters: evolution and tissue expression. BMC Genomics 2010; 11:17. [PMID: 20059771 PMCID: PMC2824716 DOI: 10.1186/1471-2164-11-17] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 01/08/2010] [Indexed: 11/12/2022] Open
Abstract
Background The SLC17 family of transporters transports the amino acids: glutamate and aspartate, and, as shown recently, also nucleotides. Vesicular glutamate transporters are found in distinct species, such as C. elegans, but the evolutionary origin of most of the genes in this family has been obscure. Results Our phylogenetic analysis shows that the SLC17 family consists of four main phylogenetic clades which were all present before the divergence of the insect lineage. One of these clades has not been previously described and it is not found in vertebrates. The clade containing Slc17a9 had the most restricted evolutionary history with only one member in most species. We detected expression of Slc17a1-17a4 only in the peripheral tissues but not in the CNS, while Slc17a5- Slc17a9 are highly expressed in both the CNS and periphery. Conclusions The in situ hybridization studies on vesicular nucleotide transporter revealed high expression throughout the cerebral cortex, certain areas in the hippocampus and in specific nuclei of the hypothalamus and thalamus. Some of the regions with high expression, such as the medial habenula and the dentate gyrus of the hippocampus, are important sites for purinergic neurotransmission. Noteworthy, other areas relying on purine-mediated signaling, such as the molecular layer of the dentate gyrus and the periaqueductal gray, lack or have a very low expression of Slc17a9, suggesting that there could be another nucleotide transporter in these regions.
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Affiliation(s)
- Smitha Sreedharan
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
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Duncan PI, Raymond F, Fuerholz A, Sprenger N. Sialic acid utilisation and synthesis in the neonatal rat revisited. PLoS One 2009; 4:e8241. [PMID: 20011510 PMCID: PMC2785881 DOI: 10.1371/journal.pone.0008241] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Accepted: 11/19/2009] [Indexed: 12/27/2022] Open
Abstract
Background Milk is the sole source of nutrients for neonatal mammals and is generally considered to have co-evolved with the developmental needs of the suckling newborn. One evolutionary conserved constituent of milk and present on many glycoconjugates is sialic acid. The brain and colon are major sites of sialic acid display and together with the liver also of synthesis. Methodology/Principal Findings In this study we examined in rats the relationship between the sialic acid content of milk and the uptake, utilization and synthesis of sialic acid in suckling pups. In rat milk sialic acid was found primarily as 3′sialyllactose and at highest levels between 3 and 10 days postpartum and that decreased towards weaning. In the liver of suckling pups sialic acid synthesis paralleled the increase in milk sialic acid reaching and keeping maximum activity from postnatal day 5 onwards. In the colon, gene expression profiles suggested that a switch from sialic acid uptake and catabolism towards sialic acid synthesis and utilization occurred that mirrored the change of sialic acid in milk from high to low expression. In brain sialic acid related gene expression profiles did not change to any great extent during the suckling period. Conclusions/Significance Our results support the views that (i) when milk sialic acid levels are high, in the colon this sialic acid is catabolized to GlcNAc that in turn may be used as such or used as substrate for sialic acid synthesis and (ii) when milk sialic acid levels are low the endogenous sialic acid synthetic machinery in colon is activated.
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Affiliation(s)
- Peter I. Duncan
- Nestlé Research Center, Vers-chez-les-Blanc, Lausanne, Switzerland
- * E-mail: (PID); (NS)
| | - Frédéric Raymond
- Nestlé Research Center, Vers-chez-les-Blanc, Lausanne, Switzerland
| | - Andreas Fuerholz
- Nestlé Research Center, Vers-chez-les-Blanc, Lausanne, Switzerland
| | - Norbert Sprenger
- Nestlé Research Center, Vers-chez-les-Blanc, Lausanne, Switzerland
- * E-mail: (PID); (NS)
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Postsynaptic response to stimulation of the Schaffer collaterals with properties similar to those of synaptosomal aspartate release. Brain Res 2009; 1295:13-20. [PMID: 19664606 DOI: 10.1016/j.brainres.2009.07.104] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Revised: 07/17/2009] [Accepted: 07/30/2009] [Indexed: 11/23/2022]
Abstract
Aspartate satisfies all the criteria normally required for identification of a CNS neurotransmitter. Nevertheless, little electrophysiological evidence supports the existence of aspartate transmission. In studies with rat hippocampal synaptosomes, chemically evoked aspartate release differed from glutamate release in its relative sensitivity to increased Ca(2+) concentration outside the presynaptic active zones, inefficient coupling to P/Q-type Ca(2+) channels, sensitivity to KB-R7943, and resistance to native Clostridial toxins. We took advantage of these differences to search for a potential aspartate-mediated response at Schaffer collateral synapses in organotypic hippocampal slice cultures. The slice cultures were pretreated with botulinum neurotoxin C (BoNT/C) to eliminate most of the glutamate release so that an expectedly smaller aspartate-like component of the compound EPSC could be detected by whole cell patch clamp recording. In control cultures, NMDA receptor activation accounted for only 18% of the evoked EPSC and an NR2B-selective antagonist reduced the NMDA receptor-mediated component by only 20%. Block of P/Q-type Ca(2+) channels essentially eliminated the response and 0.1 muM KB-R7943 had no significant effect. In BoNT/C-pretreated cultures, however, NMDA receptor activation accounted for 77% of the evoked EPSC and an NR2B-selective antagonist reduced the NMDA receptor-mediated component by 57%. Block of P/Q-type Ca(2+) channels reduced the response by only 28%, but 0.1 muM KB-R7943 reduced it by 45%. These results suggest that part of the Schaffer collateral synaptic response has pharmacological properties similar to those of synaptosomal aspartate release and may therefore be mediated at least partly by released aspartate.
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Ruivo R, Anne C, Sagné C, Gasnier B. Molecular and cellular basis of lysosomal transmembrane protein dysfunction. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:636-49. [DOI: 10.1016/j.bbamcr.2008.12.008] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 12/10/2008] [Accepted: 12/11/2008] [Indexed: 02/04/2023]
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Abstract
Aspartate is an excitatory amino acid that is costored with glutamate in synaptic vesicles of hippocampal neurons and synaptic-like microvesicles (SLMVs) of pinealocytes and is exocytosed and stimulates neighboring cells by binding to specific cell receptors. Although evidence increasingly supports the occurrence of aspartergic neurotransmission, this process is still debated because the mechanism for the vesicular storage of aspartate is unknown. Here, we show that sialin, a lysosomal H(+)/sialic acid cotransporter, is present in hippocampal synaptic vesicles and pineal SLMVs. RNA interference of sialin expression decreased exocytosis of aspartate and glutamate in pinealocytes. Proteoliposomes containing purified sialin actively accumulated aspartate and glutamate to a similar extent when inside positive membrane potential is imposed as the driving force. Sialin carrying a mutation found in people suffering from Salla disease (R39C) was completely devoid of aspartate and glutamate transport activity, although it retained appreciable H(+)/sialic acid cotransport activity. These results strongly suggest that sialin possesses dual physiological functions and acts as a vesicular aspartate/glutamate transporter. It is possible that people with Salla disease lose aspartergic (and also the associated glutamatergic) neurotransmission, and this could provide an explanation for why Salla disease causes severe neurological defects.
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Li H, Gilbert ER, Zhang Y, Crasta O, Emmerson D, Webb KE, Wong EA. Expression profiling of the solute carrier gene family in chicken intestine from the late embryonic to early post-hatch stages. Anim Genet 2008; 39:407-24. [PMID: 18544075 DOI: 10.1111/j.1365-2052.2008.01744.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Intestinal development during late embryogenesis and early post-hatch has a long-term influence on digestive and absorptive capacity in chickens. The objective of this research was to obtain a global view of intestinal solute carrier (SLC) gene family member expression from late embryogenesis until 2 weeks post-hatch with a focus on SLC genes involved in uptake of sugars and amino acids. Small intestine samples from male chicks were collected on embryonic days 18 (E18) and 20 (E20), day of hatch and days 1, 3, 7 and 14 post-hatch. The expression profiles of 162 SLC genes belonging to 41 SLC families were determined using Affymetrix chicken genome microarrays. The majority of SLC genes showed little or no difference in level of expression during E18-D14. A number of well-known intestinal transporters were upregulated between E18 and D14 including the amino acid transporters rBAT, y(+)LAT-2 and EAAT3, the peptide transporter PepT1 and the sugar transporters SGLT1, GLUT2 and GLUT5. The amino acid transporters CAT-1 and CAT-2 were downregulated. In addition, several glucose and amino acid transporters that are novel to our understanding of nutrient absorption in the chicken intestine were discovered through the arrays (SGLT6, SNAT1, SNAT2 and AST). These results represent a comprehensive characterization of the expression profiles of the SLC family of genes at different stages of development in the chicken intestine and lay the ground work for future nutritional studies.
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Affiliation(s)
- H Li
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061-0306, USA
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Presynaptic calcium channel localization and calcium-dependent synaptic vesicle exocytosis regulated by the Fuseless protein. J Neurosci 2008; 28:3668-82. [PMID: 18385325 DOI: 10.1523/jneurosci.5553-07.2008] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A systematic forward genetic Drosophila screen for electroretinogram mutants lacking synaptic transients identified the fuseless (fusl) gene, which encodes a predicted eight-pass transmembrane protein in the presynaptic membrane. Null fusl mutants display >75% reduction in evoked synaptic transmission but, conversely, an approximately threefold increase in the frequency and amplitude of spontaneous synaptic vesicle fusion events. These neurotransmission defects are rescued by a wild-type fusl transgene targeted only to the presynaptic cell, demonstrating a strictly presynaptic requirement for Fusl function. Defects in FM dye turnover at the synapse show a severely impaired exo-endo synaptic vesicle cycling pool. Consistently, ultrastructural analyses reveal accumulated vesicles arrested in clustered and docked pools at presynaptic active zones. In the absence of Fusl, calcium-dependent neurotransmitter release is dramatically compromised and there is little enhancement of synaptic efficacy with elevated external Ca(2+) concentrations. These defects are causally linked with severe loss of the Cacophony voltage-gated Ca(2+) channels, which fail to localize normally at presynaptic active zone domains in the absence of Fusl. These data indicate that Fusl regulates assembly of the presynaptic active zone Ca(2+) channel domains required for efficient coupling of the Ca(2+) influx and synaptic vesicle exocytosis during neurotransmission.
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Wessel J, Zapala MA, Schork NJ. Accommodating pathway information in expression quantitative trait locus analysis. Genomics 2007; 90:132-42. [PMID: 17493783 DOI: 10.1016/j.ygeno.2007.03.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Revised: 03/01/2007] [Accepted: 03/14/2007] [Indexed: 11/30/2022]
Abstract
The availability of high-throughput genotyping technologies and microarray assays has allowed researchers to consider pursuing investigations whose ultimate goal is the identification of genetic variations that influence levels of gene expression, e.g., "expression quantitative trait locus" or "eQTL" mapping studies. However, the large number of genes whose expression levels can be tested for association with genetic variations in such studies can create both statistical and biological interpretive problems. We consider the integrated analysis of eQTL mapping data that incorporates pathway, function, and disease process information. The goal of this analysis is to determine if compelling patterns emerge from the data that are consistent with the notion that perturbations in the molecular physiologic environment induced by genetic variations implicate the expression patterns of multiple genes via genetic network relationships or feedback mechanisms. We apply available genetic network and pathway analysis software, as well as a novel regression analysis technique, to carry out the proposed studies. We also consider extensions of the proposed strategies and areas of future research.
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Affiliation(s)
- Jennifer Wessel
- Polymorphism Research Laboratory, Department of Psychiatry, University of California at San Diego, La Jolla, CA 92093, USA
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