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Panda A, Brown C, Gupta K. Studying Membrane Protein-Lipid Specificity through Direct Native Mass Spectrometric Analysis from Tunable Proteoliposomes. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:1917-1927. [PMID: 37432128 PMCID: PMC10932607 DOI: 10.1021/jasms.3c00110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/12/2023]
Abstract
Native mass spectrometry (nMS) has emerged as a key analytical tool to study the organizational states of proteins and their complexes with both endogenous and exogenous ligands. Specifically, for membrane proteins, it provides a key analytical dimension to determine the identity of bound lipids and to decipher their effects on the observed structural assembly. We recently developed an approach to study membrane proteins directly from intact and tunable lipid membranes where both the biophysical properties of the membrane and its lipid compositions can be customized. Extending this, we use our liposome-nMS platform to decipher the lipid specificity of membrane proteins through their multiorganelle trafficking pathways. To demonstrate this, we used VAMP2 and reconstituted it in the endoplasmic reticulum (ER), Golgi, synaptic vesicle (SV), and plasma membrane (PM) mimicking liposomes. By directly studying VAMP2 from these customized liposomes, we show how the same transmembrane protein can bind to different sets of lipids in different organellar-mimicking membranes. Considering that the cellular trafficking pathway of most eukaryotic integral membrane proteins involves residence in multiple organellar membranes, this study highlights how the lipid-specificity of the same integral membrane protein may change depending on the membrane context. Further, leveraging the capability of the platform to study membrane proteins from liposomes with curated biophysical properties, we show how we can disentangle chemical versus biophysical properties, of individual lipids in regulating membrane protein assembly.
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Affiliation(s)
- Aniruddha Panda
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, United States
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520, United States
| | - Caroline Brown
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, United States
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520, United States
| | - Kallol Gupta
- Nanobiology Institute, Yale University, West Haven, Connecticut 06516, United States
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520, United States
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Role of SNAREs in Neurodegenerative Diseases. Cells 2021; 10:cells10050991. [PMID: 33922505 PMCID: PMC8146804 DOI: 10.3390/cells10050991] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 04/18/2021] [Accepted: 04/20/2021] [Indexed: 02/06/2023] Open
Abstract
Neurodegenerative diseases are pathologies of the central and peripheral nervous systems characterized by loss of brain functions and problems in movement which occur due to the slow and progressive degeneration of cellular elements. Several neurodegenerative diseases are known such as Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis and many studies on the molecular mechanisms underlying these pathologies have been conducted. Altered functions of some key proteins and the presence of intraneuronal aggregates have been identified as responsible for the development of the diseases. Interestingly, the formation of the SNARE complex has been discovered to be fundamental for vesicle fusion, vesicle recycling and neurotransmitter release. Indeed, inhibition of the formation of the SNARE complex, defects in the SNARE-dependent exocytosis and altered regulation of SNARE-mediated vesicle fusion have been associated with neurodegeneration. In this review, the biological aspects of neurodegenerative diseases and the role of SNARE proteins in relation to the onset of these pathologies are described.
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Melland H, Carr EM, Gordon SL. Disorders of synaptic vesicle fusion machinery. J Neurochem 2020; 157:130-164. [PMID: 32916768 DOI: 10.1111/jnc.15181] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/20/2020] [Accepted: 08/26/2020] [Indexed: 12/11/2022]
Abstract
The revolution in genetic technology has ushered in a new age for our understanding of the underlying causes of neurodevelopmental, neuromuscular and neurodegenerative disorders, revealing that the presynaptic machinery governing synaptic vesicle fusion is compromised in many of these neurological disorders. This builds upon decades of research showing that disturbance to neurotransmitter release via toxins can cause acute neurological dysfunction. In this review, we focus on disorders of synaptic vesicle fusion caused either by toxic insult to the presynapse or alterations to genes encoding the key proteins that control and regulate fusion: the SNARE proteins (synaptobrevin, syntaxin-1 and SNAP-25), Munc18, Munc13, synaptotagmin, complexin, CSPα, α-synuclein, PRRT2 and tomosyn. We discuss the roles of these proteins and the cellular and molecular mechanisms underpinning neurological deficits in these disorders.
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Affiliation(s)
- Holly Melland
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
| | - Elysa M Carr
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
| | - Sarah L Gordon
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
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Bonnycastle K, Davenport EC, Cousin MA. Presynaptic dysfunction in neurodevelopmental disorders: Insights from the synaptic vesicle life cycle. J Neurochem 2020; 157:179-207. [PMID: 32378740 DOI: 10.1111/jnc.15035] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/14/2020] [Accepted: 04/22/2020] [Indexed: 12/11/2022]
Abstract
The activity-dependent fusion, retrieval and recycling of synaptic vesicles is essential for the maintenance of neurotransmission. Until relatively recently it was believed that most mutations in genes that were essential for this process would be incompatible with life, because of this fundamental role. However, an ever-expanding number of mutations in this very cohort of genes are being identified in individuals with neurodevelopmental disorders, including autism, intellectual disability and epilepsy. This article will summarize the current state of knowledge linking mutations in presynaptic genes to neurodevelopmental disorders by sequentially covering the various stages of the synaptic vesicle life cycle. It will also discuss how perturbations of specific stages within this recycling process could translate into human disease. Finally, it will also provide perspectives on the potential for future therapy that are targeted to presynaptic function.
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Affiliation(s)
- Katherine Bonnycastle
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Elizabeth C Davenport
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
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5
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SNAP-25 isoforms differentially regulate synaptic transmission and long-term synaptic plasticity at central synapses. Sci Rep 2019; 9:6403. [PMID: 31024034 PMCID: PMC6484009 DOI: 10.1038/s41598-019-42833-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 04/09/2019] [Indexed: 01/08/2023] Open
Abstract
SNAP-25 exists as two developmentally regulated alternatively spliced isoforms, SNAP-25a and SNAP-25b. We explored the function of SNAP-25a and SNAP-25b at Schaffer collateral-CA1 synapses in hippocampus using 4-week-old wild-type (WT) and SNAP-25b-deficient (MT) mice. Characterizing the protein expression of individual SNAP-25 isoforms revealed that WT females had higher levels of SNAP-25a than WT males, suggesting a sex-dependent delay of the alternative splicing switch from SNAP-25a to SNAP-25b. MT mice expressed normal levels of total SNAP-25, Syntaxin 1A and SNAP-47 in the hippocampus, but females expressed lower levels of VAMP2. Electrophysiological recordings in in vitro hippocampal slices revealed significantly reduced magnitude of LTP in MT mice. We also found reduction in paired-pulse facilitation after induction of LTP in WT males, but not in WT females, possibly related to the difference in SNAP-25a/SNAP-25b ratios, suggesting that the splicing switch may play a sex-specific role in LTP-associated increases in presynaptic release probability. Basal synaptic transmission measured in input-output relations revealed that the ability to discriminate between the intensity of presynaptic stimuli was affected in SNAP-25b-deficient mice. Learning in a behavioural paradigm of active-avoidance was impaired in MT mice, strengthening the conclusion that SNAP-25b is important for cognitive performance by altering activity-dependent synaptic plasticity.
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Sassen WA, Lehne F, Russo G, Wargenau S, Dübel S, Köster RW. Embryonic zebrafish primary cell culture for transfection and live cellular and subcellular imaging. Dev Biol 2017; 430:18-31. [DOI: 10.1016/j.ydbio.2017.07.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 07/24/2017] [Accepted: 07/24/2017] [Indexed: 10/19/2022]
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Rodepeter FR, Wiegand S, Lüers HG, Bonaterra GA, Lowe AW, Bette M, Jacob R, Mandic R. Indication for differential sorting of the rat v-SNARE splice isoforms VAMP-1a and -1b. Biochem Cell Biol 2017; 95:500-509. [PMID: 28314111 DOI: 10.1139/bcb-2016-0184] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins are essential constituents of the intracellular trafficking machinery. The variable C-terminus in the 2 rat VAMP-1 splice isoforms VAMP-1a and -1b potentially acts as a sorting signal, because similar changes at the C-terminal end of a human VAMP-1 splice isoform resulted in its sorting to mitochondria. To evaluate the differences in the subcellular localization of these two v-SNARE proteins, VAMP-1a and -1b proteins tagged with green fluorescent protein (GFP) and red fluorescent protein (RFP) were expressed in HeLa, COS-7, and MDCK cells and evaluated by conventional confocal as well as total internal reflection fluorescence microscopy. Regions consistent with the endoplasmic reticulum and Golgi apparatus demonstrated a major overlap of both signals. In the periphery, vesicular structures were observed that mainly expressed one of the 2 isoforms. Within our experimental settings, we could not observe sorting of any of the 2 isoforms to mitochondria or peroxisomes, whereas both isoforms were found expressed in a minor subset of singular vesicles, which sporadically appeared to co-localize with the exocyst marker EXOC3/Sec6. Because vesicular structures were seen that expressed only one of the two splice variants, it is possible that VAMP-1a and VAMP-1b are sorted to distinct cellular compartments that require further characterization.
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Affiliation(s)
- Fiona R Rodepeter
- a Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Giessen and Marburg, Campus Marburg, 3.BA, Room +3/08070, Baldingerstrasse, D-35033 Marburg, Germany
| | - Susanne Wiegand
- a Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Giessen and Marburg, Campus Marburg, 3.BA, Room +3/08070, Baldingerstrasse, D-35033 Marburg, Germany
| | - Hans-Georg Lüers
- b Department of Cell Biology, Institute of Anatomy and Cell Biology, Philipps-Universität, Marburg, Germany
| | - Gabriel A Bonaterra
- c Department of Medical Cell Biology, Philipps-Universität, Marburg, Germany
| | - Anson W Lowe
- d Department of Medicine, Stanford University, Stanford, CA, USA
| | - Michael Bette
- e Department of Molecular Neuroscience, Institute of Anatomy and Cell Biology, Philipps-Universität, Marburg, Germany
| | - Ralf Jacob
- f Institute of Cell Biology and Cell Pathology, Philipps-Universität, Marburg, Germany
| | - Robert Mandic
- a Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Giessen and Marburg, Campus Marburg, 3.BA, Room +3/08070, Baldingerstrasse, D-35033 Marburg, Germany
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Shen XM, Scola RH, Lorenzoni PJ, Kay CSK, Werneck LC, Brengman J, Selcen D, Engel AG. Novel synaptobrevin-1 mutation causes fatal congenital myasthenic syndrome. Ann Clin Transl Neurol 2017; 4:130-138. [PMID: 28168212 PMCID: PMC5288468 DOI: 10.1002/acn3.387] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 12/14/2016] [Accepted: 12/15/2016] [Indexed: 12/01/2022] Open
Abstract
Objective To identify the molecular basis and elucidate the pathogenesis of a fatal congenital myasthenic syndrome. Methods We performed clinical electrophysiology studies, exome and Sanger sequencing, and analyzed functional consequences of the identified mutation. Results Clinical electrophysiology studies of the patient revealed several‐fold potentiation of the evoked muscle action potential by high frequency nerve stimulation pointing to a presynaptic defect. Exome sequencing identified a homozygous c.340delA frameshift mutation in synaptobrevin 1 (SYB1), one of the three SNARE proteins essential for synaptic vesicle exocytosis. Analysis of both human spinal cord gray matter and normal human muscle revealed expression of the SYB1A and SYB1D isoforms, predicting expression of one or both isoforms in the motor nerve terminal. The identified mutation elongates the intravesicular C‐terminus of the A isoform from 5 to 71, and of the D isoform from 4 to 31 residues. Transfection of either mutant isoform into bovine chromaffin cells markedly reduces depolarization‐evoked exocytosis, and transfection of either mutant isoform into HEK cells significantly decreases expression of either mutant compared to wild type. Interpretation The mutation is pathogenic because elongation of the intravesicular C‐terminus of the A and D isoforms increases the energy required to move their C‐terminus into the synaptic vesicle membrane, a key step for fusion of the synaptic vesicle with the presynaptic membrane, and because it is predicted to reduce expression of either isoform in the nerve terminal.
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Affiliation(s)
- Xin-Ming Shen
- Department of Neurology and Muscle Research Laboratory Mayo Clinic Rochester Minnesota 55905
| | - Rosana H Scola
- Service of Neuromuscular Disorders Division of Neurology of Hospital de Clínicas (UFPR) Curitiba 80060-900 Brazil
| | - Paulo J Lorenzoni
- Service of Neuromuscular Disorders Division of Neurology of Hospital de Clínicas (UFPR) Curitiba 80060-900 Brazil
| | - Cláudia S K Kay
- Service of Neuromuscular Disorders Division of Neurology of Hospital de Clínicas (UFPR) Curitiba 80060-900 Brazil
| | - Lineu C Werneck
- Service of Neuromuscular Disorders Division of Neurology of Hospital de Clínicas (UFPR) Curitiba 80060-900 Brazil
| | - Joan Brengman
- Department of Neurology and Muscle Research Laboratory Mayo Clinic Rochester Minnesota 55905
| | - Duygu Selcen
- Department of Neurology and Muscle Research Laboratory Mayo Clinic Rochester Minnesota 55905
| | - Andrew G Engel
- Department of Neurology and Muscle Research Laboratory Mayo Clinic Rochester Minnesota 55905
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Kubo K, Kobayashi M, Nozaki S, Yagi C, Hatsuzawa K, Katoh Y, Shin HW, Takahashi S, Nakayama K. SNAP23/25 and VAMP2 mediate exocytic event of transferrin receptor-containing recycling vesicles. Biol Open 2015; 4:910-20. [PMID: 26092867 PMCID: PMC4571095 DOI: 10.1242/bio.012146] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
We recently showed that Rab11 is involved not only in formation of recycling vesicles containing the transferrin (Tfn)–transferrin receptor (TfnR) complex at perinuclear recycling endosomes but also in tethering of recycling vesicles to the plasma membrane (PM) in concert with the exocyst tethering complex. We here aimed at identifying SNARE proteins responsible for fusion of Tfn–TfnR-containing recycling vesicles with the PM, downstream of the exocyst. We showed that exocyst subunits, Sec6 and Sec8, can interact with SNAP23 and SNAP25, both of which are PM-localizing Qbc-SNAREs, and that depletion of SNAP23 and/or SNAP25 in HeLa cells suppresses fusion of Tfn–TfnR-containing vesicles with the PM, leading to accumulation of the vesicles at the cell periphery. We also found that VAMP2, an R-SNARE, is colocalized with endocytosed Tfn on punctate endosomal structures, and that its depletion in HeLa cells suppresses recycling vesicle exocytosis. These observations indicate that fusion of recycling vesicles with the PM downstream of the exocyst is mediated by SNAP23/25 and VAMP2, and provide novel insight into non-neuronal roles of VAMP2 and SNAP25.
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Affiliation(s)
- Keiji Kubo
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Minako Kobayashi
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Shohei Nozaki
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Chikako Yagi
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Kiyotaka Hatsuzawa
- Division of Molecular Biology, Tottori University School of Life Science, Yonago, Tottori 683-8503, Japan
| | - Yohei Katoh
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hye-Won Shin
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Senye Takahashi
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Kazuhisa Nakayama
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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Al-Abdul-Wahid MS, Demill CM, Serwin MB, Prosser RS, Stewart BA. Effect of juxtamembrane tryptophans on the immersion depth of Synaptobrevin, an integral vesicle membrane protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2994-9. [PMID: 22846509 DOI: 10.1016/j.bbamem.2012.07.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 07/20/2012] [Accepted: 07/23/2012] [Indexed: 01/25/2023]
Abstract
Proper positioning of membrane proteins in the host membrane is often critical to successful protein function. While hydrophobic considerations play a dominant role in determining the topology of a protein in the membrane, amphiphilic residues, such as tryptophan, may 'anchor' the protein near the water-membrane interface. The SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) family of membrane proteins mediates intracellular membrane fusion. Correct positioning of the SNAREs is necessary if fusion is to occur. Synaptobrevins are integral vesicle membrane proteins that are well conserved across species. Interestingly, mammalian Synaptobrevins typically contain two adjacent tryptophans near the water-membrane interface whereas the Drosophila, neuronal-Synaptobrevin (n-Syb), contains a single tryptophan in this same region. To explore the role of these tryptophan residues in membrane positioning, we prepared a peptide containing residues 75-121 of D. melanogaster n-Syb in DPC micelles, biosynthetically labeled with 4-fluorophenylalanine and 5-fluorotryptophan for the examination by ¹⁹F NMR spectroscopy. Mutations of this construct containing zero and two tryptophan residues near the water-membrane interface resulted in changes in the positioning of n-Syb in the micelle. Moreover, the addition of a second tryptophan appears to slow dynamic motions of n-Syb near the micelle-water interface. These data therefore indicate that juxtamembrane tryptophan residues are important determinants of the position of Synaptobrevin in the membrane.
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Kennedy MJ, Ehlers MD. Mechanisms and function of dendritic exocytosis. Neuron 2011; 69:856-75. [PMID: 21382547 DOI: 10.1016/j.neuron.2011.02.032] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/18/2011] [Indexed: 12/30/2022]
Abstract
Dendritic exocytosis is required for a broad array of neuronal functions including retrograde signaling, neurotransmitter release, synaptic plasticity, and establishment of neuronal morphology. While the details of synaptic vesicle exocytosis from presynaptic terminals have been intensely studied for decades, the mechanisms of dendritic exocytosis are only now emerging. Here we review the molecules and mechanisms of dendritic exocytosis and discuss how exocytosis from dendrites influences neuronal function and circuit plasticity.
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Affiliation(s)
- Matthew J Kennedy
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA.
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12
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Li N, Yu ZL, Wang L, Zheng YT, Jia JX, Wang Q, Zhu MJ, Liu XH, Xia X, Li WJ. Early-life lead exposure affects the activity of TNF-alpha and expression of SNARE complex in hippocampus of mouse pups. Biol Trace Elem Res 2009; 132:227-38. [PMID: 19888558 DOI: 10.1007/s12011-009-8551-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Accepted: 10/12/2009] [Indexed: 10/20/2022]
Abstract
This study aims to investigate the effects of maternal lead exposure on learning and memory ability and the protein expression of TNF-alpha and SNARE complex (SNAP-25, VAMP-2, and Syntaxin 1A) in hippocampus of mice offspring. Pb exposure was initiated from beginning of gestation to weaning. Pb acetate administered in drinking solutions was dissolved in distilled deionized water at 0.1%, 0.5%, and 1% groups, respectively. On the PND21, the learning and memory ability of mouse pups was tested by water maze test, and the Pb levels in their blood and hippocampus were also determined. The protein expression of TNF-alpha and SNARE complex in hippocampus was measured by immunohistochemistry and Western blotting. The Pb levels in blood and hippocampus of all exposure groups were significantly higher than control group (P < 0.05). In the water maze test, the performances of 0.5% and 1% groups were worse than that of control group (P < 0.05). The expression of TNF-alpha, Syntaxin 1A, and VAMP-2 was increased in Pb-exposed groups comparing control group (P < 0.05), but the expression of SNAP-25 was decreased (P < 0.05). Up-regulation of TNF-alpha and disturbance of SNARE expression in the hippocampus of pups may contribute to impairment of learning and memory ability associated with maternal Pb exposure.
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Affiliation(s)
- N Li
- College of Public Health, Zhengzhou University, Zhengzhou 450001, China
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Heterogeneity of glutamatergic and GABAergic release machinery in cerebral cortex: analysis of synaptogyrin, vesicle-associated membrane protein, and syntaxin. Neuroscience 2009; 165:934-43. [PMID: 19909789 DOI: 10.1016/j.neuroscience.2009.11.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Revised: 10/16/2009] [Accepted: 11/04/2009] [Indexed: 11/21/2022]
Abstract
To define whether cortical glutamatergic and GABAergic release machineries can be differentiated on the basis of the nature and amount of proteins they express, we studied the degree of co-localization of synaptogyrin (SGYR) 1 and 3, vesicle-associated membrane protein (VAMP) 1 and 2, syntaxin (STX) 1A and 1B in vesicular glutamate transporter (VGLUT)1-, VGLUT2- and vesicular GABA transporter (VGAT)-positive (+) puncta and synaptic vesicles in the rat cerebral cortex. Co-localization studies showed that SGYR1 and 3 were expressed in about 90% of VGLUT1+, 70% of VGLUT2+ and 80% of VGAT+ puncta; VAMP1 was expressed in approximately 45% of VGLUT1+, 55% of VGLUT2+, and 80% of VGAT+ puncta; VAMP2 in about 95% of VGLUT1+, 75% of VGLUT2+, and 80% of VGAT+ puncta; STX1A in about 65% of VGLUT1+, 30% of VGLUT2+, and 3% of VGAT+ puncta, and STX1B in approximately 45% of VGLUT1+, 35% of VGLUT2+, and 70% of VGAT+ puncta. Immunoisolation studies showed that while STX1A was completely segregated and virtually absent from VGAT synaptic vesicles, STX1B, VAMP1/VAMP2, SGYR1/SGYR3 showed a similar pattern with the highest expression in VGLUT1 immunoisolated vesicles and the lowest in VGAT immunoisolated vesicles. Moreover, we studied the localization of STX1B at the electron microscope and found that a population of axon terminals forming symmetric synapses were STX1B-positive.These results extend our previous observations on the differential expression of presynaptic proteins involved in neurotransmitter release in GABAergic and glutamatergic terminals and indicate that heterogeneity of glutamatergic and GABAergic release machinery can be contributed by both the presence or absence of a given protein in a nerve terminal and the amount of protein expressed by synaptic vesicles.
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14
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De Steno DA, Schmauss C. A role for dopamine D2 receptors in reversal learning. Neuroscience 2009; 162:118-27. [PMID: 19401217 DOI: 10.1016/j.neuroscience.2009.04.052] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 04/08/2009] [Accepted: 04/20/2009] [Indexed: 11/15/2022]
Abstract
Reversal learning has been shown to require intact serotonergic innervation of the forebrain neocortex. Whether dopamine acting through D2 receptors plays a complementary role in this anatomic area is still unclear. Here we show that mice lacking dopamine D2 receptors exhibited significantly impaired performance in the reversal learning phase of an attention-set-shifting task (ASST) and that wild type mice treated chronically with the D2-like receptor antagonist haloperidol exhibited the same cognitive deficit. The test-phase-specific deficits of D2 mutants and haloperidol-treated mice were also accompanied by deficits in the induction of expression of early growth response gene 2 (egr-2), a regulatory transcription factor previously shown to be selectively induced in the ventrolateral orbital frontal cortex and the pre- and infralimbic medial prefrontal cortex of ASST-tested mice. D2-receptor knockout mice and haloperidol-treated wild type, however, exhibited lower egr-2 expression in these anatomic regions after completion of an ASST-test phase that required reversal learning but not after completion of set-shifting phases without rule reversals. In contrast, mice treated chronically with clozapine, an atypical neuroleptic drug with lower D2-receptor affinity and broader pharmacological effects, had deficits in compound discrimination phases of the ASST, but also these deficits were accompanied by lower egr-2 expression in the same anatomic subregions. Thus, the findings indicate that egr-2 expression is a sensitive indicator of test-phase-specific performance in the ASST and that normal function of D2 receptors in subregions of the orbital frontal and the medial prefrontal cortex is required for cognitive flexibility in tests involving rule reversals.
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Affiliation(s)
- D A De Steno
- Department of Pharmacology, Columbia University, New York, NY 10032, USA
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15
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Johansson JU, Ericsson J, Janson J, Beraki S, Stanić D, Mandic SA, Wikström MA, Hökfelt T, Ögren SO, Rozell B, Berggren PO, Bark C. An ancient duplication of exon 5 in the Snap25 gene is required for complex neuronal development/function. PLoS Genet 2008; 4:e1000278. [PMID: 19043548 PMCID: PMC2581893 DOI: 10.1371/journal.pgen.1000278] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Accepted: 10/27/2008] [Indexed: 01/05/2023] Open
Abstract
Alternative splicing is an evolutionary innovation to create functionally diverse proteins from a limited number of genes. SNAP-25 plays a central role in neuroexocytosis by bridging synaptic vesicles to the plasma membrane during regulated exocytosis. The SNAP-25 polypeptide is encoded by a single copy gene, but in higher vertebrates a duplication of exon 5 has resulted in two mutually exclusive splice variants, SNAP-25a and SNAP-25b. To address a potential physiological difference between the two SNAP-25 proteins, we generated gene targeted SNAP-25b deficient mouse mutants by replacing the SNAP-25b specific exon with a second SNAP-25a equivalent. Elimination of SNAP-25b expression resulted in developmental defects, spontaneous seizures, and impaired short-term synaptic plasticity. In adult mutants, morphological changes in hippocampus and drastically altered neuropeptide expression were accompanied by severe impairment of spatial learning. We conclude that the ancient exon duplication in the Snap25 gene provides additional SNAP-25-function required for complex neuronal processes in higher eukaryotes. In evolution, duplication of genes or gene segments appears to be an efficient way to add diverse functions in more complex organisms. The SNAP-25 protein plays an important role in mediating the release of neurotransmitters and hormones. SNAP-25 exists as two variants: SNAP-25a, which is present in early development, and SNAP-25b, which is most abundant from early adulthood and onwards. We have developed mouse mutants that only express SNAP-25a, but retain normal SNAP-25 levels by replacing the SNAP-25b segment in the Snap25 gene with an additional SNAP-25a copy. We show that SNAP-25b is required for early postnatal development and that a balanced expression of the two proteins is a prerequisite for maintaining an operational neuronal network during adulthood. Mice that only have SNAP-25a develop seizures, and show learning deficits and anxiety. Synaptic plasticity is impaired, and structural changes are observed in areas that are connected to such behavioral functions. In man, SNAP-25 function has been linked to behavioral and neuropsychiatric disorders, including attention deficit hyperactivity disorder, ADHD. Our present findings using genetic elimination of SNAP-25b suggest that even small alterations in the regulation of the Snap25 gene, resulting in a disturbed balance between SNAP-25a and SNAP-25b, lead to nervous system dysfunction.
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Affiliation(s)
- Jenny U. Johansson
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Jesper Ericsson
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Juliette Janson
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Simret Beraki
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Davor Stanić
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Slavena A. Mandic
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | | | - Tomas Hökfelt
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Sven Ove Ögren
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Björn Rozell
- Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Per-Olof Berggren
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Christina Bark
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
- * E-mail:
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16
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DeSteno DA, Schmauss C. Induction of early growth response gene 2 expression in the forebrain of mice performing an attention-set-shifting task. Neuroscience 2008; 152:417-28. [PMID: 18280047 DOI: 10.1016/j.neuroscience.2008.01.012] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Revised: 10/17/2007] [Accepted: 01/10/2008] [Indexed: 11/30/2022]
Abstract
Early growth response (egr) genes encode transcription factors that are induced by stimuli that cause synaptic plasticity. Here we show that the expression of one member of this family, egr-2, is induced in the orbital frontal cortex (OFC) and medial prefrontal cortex (mPFC) of mice performing an attention-set-shifting task (ASST). The ASST is a series of two-choice perceptual discriminations between different odors and textures. Within the OFC and mPFC, different subregions exhibited egr-2 induction in response to different test-related features. In the medial OFC and the anterior cingulate subregion of the mPFC, egr-2 induction occurred in response to exposure to the novel odor stimulus. In the ventrolateral OFC and the pre- and infralimbic mPFC, additional egr-2 induction occurred during the associative learning phase of the ASST. In the infralimbic mPFC, further egr-2 induction occurred when mice performed set-shifting and reversal learning phases of the ASST. Mice with enhanced set-shifting performance exhibited decreased egr-2 induction in the mPFC indicating that the magnitude of egr-2 induction correlates with the magnitude of attentional demand. This decrease was largest in the infralimbic mPFC suggesting further that egr-2 induction in this region plays a role in the attentional control during set-shifting. In contrast to egr-2, neither egr-1 nor egr-3 expression was altered in ASST-tested mice, and no egr-2 induction occurred in mice that performed a spatial working memory task. These findings suggest a specific role of egr-2-mediated transcriptional activation in cognitive functions associated with attention.
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Affiliation(s)
- D A DeSteno
- Department of Pharmacology, Columbia University, NY, NY 10032, USA
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17
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Ward B, McGuinness L, Akerman CJ, Fine A, Bliss TVP, Emptage NJ. State-dependent mechanisms of LTP expression revealed by optical quantal analysis. Neuron 2007; 52:649-61. [PMID: 17114049 DOI: 10.1016/j.neuron.2006.10.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Revised: 07/07/2006] [Accepted: 10/09/2006] [Indexed: 10/23/2022]
Abstract
The expression mechanism of long-term potentiation (LTP) remains controversial. Here we combine electrophysiology and Ca(2+) imaging to examine the role of silent synapses in LTP expression. Induction of LTP fails to change p(r) at these synapses but instead mediates an unmasking process that is sensitive to the inhibition of postsynaptic membrane fusion. Once unmasked, however, further potentiation of formerly silent synapses leads to an increase in p(r). The state of the synapse thus determines how LTP is expressed.
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Affiliation(s)
- Bonnie Ward
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom
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18
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Camacho M, Machado JD, Montesinos MS, Criado M, Borges R. Intragranular pH rapidly modulates exocytosis in adrenal chromaffin cells. J Neurochem 2005; 96:324-34. [PMID: 16336635 DOI: 10.1111/j.1471-4159.2005.03526.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several drugs produce rapid changes in the kinetics of exocytosis of catecholamines, as measured at the single event level with amperometry. This study is intended to unveil whether the mechanism(s) responsible for these effects involve changes in the intravesicular pH. Cell incubation with bafilomycin A1, a blocker of the vesicular proton pump, caused both a deceleration in the kinetics of exocytosis and a reduction in the catecholamine content of vesicle. These effects were also observed upon reduction of proton gradient by nigericin or NH4Cl. pH measurements using fluorescent probes (acridine orange, quinacrine or enhanced green fluorescent protein-synaptobrevin) showed a strong correlation between vesicular pH and the kinetics of exocytosis. Hence, all maneuvers tested that decelerated exocytosis also alkalinized secretory vesicles and vice versa. On the other hand, calcium entry caused a transient acidification of granules. We therefore propose that the regulation of vesicular pH is, at least partially, a necessary step in the modulation of the kinetics of exocytosis and quantal size operated by some cell signals.
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Affiliation(s)
- Marcial Camacho
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, Tenerife, Spain
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19
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Nagy G, Milosevic I, Fasshauer D, Müller EM, de Groot BL, Lang T, Wilson MC, Sørensen JB. Alternative splicing of SNAP-25 regulates secretion through nonconservative substitutions in the SNARE domain. Mol Biol Cell 2005; 16:5675-85. [PMID: 16195346 PMCID: PMC1289412 DOI: 10.1091/mbc.e05-07-0595] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The essential membrane fusion apparatus in mammalian cells, the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, consists of four alpha-helices formed by three proteins: SNAP-25, syntaxin 1, and synaptobrevin 2. SNAP-25 contributes two helices to the complex and is targeted to the plasma membrane by palmitoylation of four cysteines in the linker region. It is alternatively spliced into two forms, SNAP-25a and SNAP-25b, differing by nine amino acids substitutions. When expressed in chromaffin cells from SNAP-25 null mice, the isoforms support different levels of secretion. Here, we investigated the basis of that different secretory phenotype. We found that two nonconservative substitutions in the N-terminal SNARE domain and not the different localization of one palmitoylated cysteine cause the functional difference between the isoforms. Biochemical and molecular dynamic simulation experiments revealed that the two substitutions do not regulate secretion by affecting the property of SNARE complex itself, but rather make the SNAP-25b-containing SNARE complex more available for the interaction with accessory factor(s).
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Affiliation(s)
- Gábor Nagy
- Department of Membrane Biophysics, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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20
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Belizaire R, Komanduri C, Wooten K, Chen M, Thaller C, Janz R. Characterization of synaptogyrin 3 as a new synaptic vesicle protein. J Comp Neurol 2004; 470:266-81. [PMID: 14755516 DOI: 10.1002/cne.20008] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Synaptogyrins comprise a family of tyrosine-phosphorylated proteins with two neuronal (synaptogyrins 1 and 3) and one ubiquitous (cellugyrin) isoform. Previous studies have indicated that synaptogyrins are involved in the regulation of neurotransmitter release. Synaptogyrin 1 is a synaptic vesicle protein; cellugyrin, by contrast, is absent from synaptic vesicles. In an effort to further characterize the synaptogyrin family, we studied the distribution of the synaptogyrin 3 protein in the nervous system. Subcellular fractionation and immunoprecipitation of synaptic vesicles from mouse brain showed that synaptogyrin 3 is associated with synaptic vesicles and that synaptogyrins 1 and 3 can reside on the same synaptic vesicle. Immunofluorescent staining of cultured hippocampal neurons confirmed the synaptic localization of synaptogyrin 3. Analysis of the relative distributions of synaptogyrins 1 and 3 in mouse brain revealed a more restricted expression pattern for synaptogyrin 3 compared to the ubiquitous distribution of synaptogyrin 1. Strong synaptogyrin 3 labeling was observed in the mossy fiber region of the hippocampus, substantia nigra pars reticulata, pallidum, and deep cerebellar nuclei. By comparison, the striatum and reticular and ventral posterolateral thalamic nuclei, which all showed synaptogyrin 1 labeling, contained significantly less synaptogyrin 3. Finally, we used in situ hybridization experiments to correlate synaptogyrin 3 mRNA in cell bodies with synaptogyrin 3 protein at synapses. Altogether, our data indicate that neuronal synaptogyrins are differentially expressed protein isoforms that may represent functionally distinct populations of synapses and/or synaptic vesicles.
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Affiliation(s)
- Roger Belizaire
- W.M. Keck Center for Learning and Memory, Department of Neurobiology and Anatomy, University of Texas-Houston Medical School, Houston, Texas, 77030, USA.
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21
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Yang R, Stoick CL, Kinnamon JC. Synaptobrevin-2-like immunoreactivity is associated with vesicles at synapses in rat circumvallate taste buds. J Comp Neurol 2004; 471:59-71. [PMID: 14983476 DOI: 10.1002/cne.20021] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Synaptobrevin is a vesicle-associated membrane protein (VAMP) that is believed to play a critical role with presynaptic membrane proteins (SNAP-25 and syntaxin) during regulated synaptic vesicle docking and exocytosis of neurotransmitter at the central nervous system. Synaptic contacts between taste cells and nerve processes have been found to exist, but little is known about synaptic vesicle docking and neurotransmitter release at taste cell synapses. Previously we demonstrated that immunoreactivity to SNAP-25 is present in taste cells with synapses. Our present results show that synaptobrevin-2-like immunoreactivity (-LIR) is present in approximately 35% of the taste cells in rat circumvallate taste buds. Synaptobrevin-2-LIR colocalizes with SNAP-25-, serotonin-, and protein gene product 9.5-LIR. Synaptobrevin-2-LIR also colocalizes with immunoreactivity for type III inositol 1,4,5-triphosphate receptor (IP3R3), a taste-signaling molecule in taste cells. All IP3R3-LIR taste cells express synaptobrevin-2-LIR. However, approximately 27% of the synaptobrevin-2-LIR taste cells do not display IP3R3-LIR. We believe, based on ultrastructural and biochemical features, that both type II and type III taste cells display synaptobrevin-2-LIR. All of the synapses that we observed from taste cells onto nerve processes express synaptobrevin-2-LIR, as well as some taste cells without synapses. By using colloidal gold immunoelectron microscopy, we found that synaptobrevin-2-LIR is associated with synaptic vesicles at rat taste cell synapses. The results of this study suggest that soluble NSF attachment receptor (SNARE) machinery may control synaptic vesicle fusion and exocytosis at taste cell synapses.
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Affiliation(s)
- Ruibiao Yang
- Department of Biological Sciences, University of Denver, and Rocky Mountain Taste and Smell Center, Denver, Colorado 80208, USA
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22
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Mollinedo F, Martín-Martín B, Calafat J, Nabokina SM, Lazo PA. Role of vesicle-associated membrane protein-2, through Q-soluble N-ethylmaleimide-sensitive factor attachment protein receptor/R-soluble N-ethylmaleimide-sensitive factor attachment protein receptor interaction, in the exocytosis of specific and tertiary granules of human neutrophils. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2003; 170:1034-42. [PMID: 12517971 DOI: 10.4049/jimmunol.170.2.1034] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have examined the role of the R-soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) synaptobrevin-2/vesicle-associated membrane protein (VAMP)-2 in neutrophil exocytosis. VAMP-2, localized in the membranes of specific and gelatinase-containing tertiary granules in resting human neutrophils, resulted translocated to the cell surface following neutrophil activation under experimental conditions that induced exocytosis of specific and tertiary granules. VAMP-2 was also found on the external membrane region of granules docking to the plasma membrane in activated neutrophils. Specific Abs against VAMP-2 inhibited Ca(2+) and GTP-gamma-S-induced exocytosis of CD66b-enriched specific and tertiary granules, but did not affect exocytosis of CD63-enriched azurophilic granules, in electropermeabilized neutrophils. Tetanus toxin disrupted VAMP-2 and inhibited exocytosis of tertiary and specific granules. Activation of neutrophils led to the interaction of VAMP-2 with the plasma membrane Q-SNARE syntaxin 4, and anti-syntaxin 4 Abs inhibited exocytosis of specific and tertiary granules in electropermeabilized neutrophils. Immunoelectron microscopy showed syntaxin 4 on the plasma membrane contacting with docked granules in activated neutrophils. These data indicate that VAMP-2 mediates exocytosis of specific and tertiary granules, and that Q-SNARE/R-SNARE complexes containing VAMP-2 and syntaxin 4 are involved in neutrophil exocytosis.
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Affiliation(s)
- Faustino Mollinedo
- Centro de Investigación del Cáncer, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Cientificas-Universidad de Salamanca, Spain.
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23
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Martin JR, Keller A, Sweeney ST. Targeted expression of tetanus toxin: a new tool to study the neurobiology of behavior. ADVANCES IN GENETICS 2002; 47:1-47. [PMID: 12000095 DOI: 10.1016/s0065-2660(02)47001-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Over the past few decades, the explosion of molecular genetic knowledge, particularly in the fruit fly Drosophila melanogaster, has led to the identification of a large number of genes, which, when mutated, directly or indirectly affect fly behavior. Beyond the genetic and molecular characterization of genes and their associated molecular pathways, recent advances in molecular genetics also have allowed the development of new tools dedicated more directly to the dissection of the neural bases for various behaviors. In particular, the conjunction of the development of two techniques--the enhancer-trap detection system and the targeted gene expression system, based on the yeast GAL4 transcription factor--has led to the development of the binary enhancer-trap P[GAL4] expression system, which allows the selective activation of any cloned gene in a wide variety of tissue- and cell-specific patterns. Thus, this development, in addition to allowing the anatomical characterization of neuronal circuitry, also allows, via the expression of tetanus toxin light chain (known to specifically block synaptic transmission), an investigation of the role of specific neurons in certain behaviors. Using this system of "toxigenetics," several forms of behavior--from those mediated by sensory systems, such as olfaction, mechanoreception, and vision, to those mediated by higher brain function, such as learning, memory and locomotion--have been studied. These studies aim to map neuronal circuitry underlying specific behaviors and thereby unravel relevant neurophysiological mechanisms. The advantage of this approach is that it is noninvasive and permits the investigation of behavior in the free moving animal. We review a number of behavioral studies that have successfully employed this toxigenetic approach, and we hope to persuade the reader that transgenic tetanus toxin light chain is a useful and appropriate tool for the armory of neuroethologists.
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Affiliation(s)
- Jean-René Martin
- NAMC, CNRS, UMR-8620, Université Paris-Sud, Centre Scientifique d'Orsay, France
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24
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Falbo V, Floridia G, Gaudi S, Zoraqi G, Taruscio D. A new polymorphism in the flanking region of human VAMP2 and hPer1 genes. Mol Cell Probes 2002; 16:391-2. [PMID: 12477444 DOI: 10.1006/mcpr.2002.0430] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- V Falbo
- National Center for Rare Diseases, Laboratory of Ultrastructure, Istituto Superiore di Sanità, Viale Regina Elena, 299 Rome, Italy
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25
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Yoshida S, Narita T, Taga T, Ohta S, Takeuchi Y. Malignant rhabdoid tumor shows incomplete neural characteristics as revealed by expression of SNARE complex. J Neurosci Res 2002; 69:642-52. [PMID: 12210830 DOI: 10.1002/jnr.10330] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
To elucidate the biological differences in neural phenotype between malignant rhabdoid tumor (MRT) and neuroblastoma cell lines, we examined the expression of solube N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) complex proteins in MRT cell lines under differentiation induction with 12-O-tetradecanoylphorbol-13-acetate (TPA). Six MRT cell lines (TM87-16, STM91-01, TTC642, TTC549, YAM-RTK1, and TTC1240) and six neuroblastoma cell lines (IMR-32, NH12, SCCH26, TGW, NB-1, and NB-NR) were used in this study. Expression of SNAREs: the vesicle SNARE (synaptotagmin, synaptophysin, and synaptobrevin-2) and the target SNARE (syntaxin 1A, SNAP-25A/B) was examined. Our results showed that in MRT cells, only two cell lines (TM87-16, TTC642) expressed the vesicle SNARE and the target SNARE with the exception of SNAP-25B, while all neuroblastoma cells expressed the entire SNARE complex. During differentiation, synaptotagmin was upregulated in these two MRT cell lines. Interestingly, synaptophysin was downregulated in these MRT cell lines in contrast with the neuroblastoma cell lines. SNAP-25B was not expressed in MRT cells after differentiation with TPA. MRT cells having a neural phenotype morphologically looked like neuroblastoma cells after treatment with TPA. However, the expression of SNARE complex was incomplete in MRT cells. Our results suggest that the biological characteristics of MRT cells with neural phenotype are distinct from those of neuroblastoma cells.
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Affiliation(s)
- Shinobu Yoshida
- Department of Pediatrics, Shiga University of Medical Science, Seta, Tsukinowa-cho, Ohtsu, Japan
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26
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Ujike H, Takaki M, Kodama M, Kuroda S. Gene expression related to synaptogenesis, neuritogenesis, and MAP kinase in behavioral sensitization to psychostimulants. Ann N Y Acad Sci 2002; 965:55-67. [PMID: 12105085 DOI: 10.1111/j.1749-6632.2002.tb04151.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The most important characteristic of behavioral sensitization to psychostimulants, such as amphetamine and cocaine, is the very long-lasting hypersensitivity to the drug after cessation of exposure. Rearrangement and structural modification of neural networks in CNS must be involved in behavioral sensitization. Previous microscopic studies have shown that the length of dendrites and density of dendritic spines increased in the nucleus accumbens and frontal cortex after repeated exposure to amphetamine and cocaine, but the molecular mechanisms responsible are not well understood. We investigated a set of genes related to synaptogenesis, neuritogenesis, and mitogen-activated protein (MAP) kinase after exposure to methamphetamine. Synaptophysin mRNA, but not VAMP2 (synaptobrevin 2) mRNA, which are considered as synaptogenesis markers, increased in the accumbens, striatum, hippocampus, and several cortices, including the medial frontal cortex, after a single dose of 4 mg/kg methamphetamine. Stathmin mRNA, but not neuritin or narp mRNA, which are markers for neuritic sprouting, increased in the striatum, hippocampus, and cortices after a single dose of methamphetamine. The mRNA of arc, an activity-regulated protein associated with cytoskeleton, but not of alpha-tubulin, as markers for neuritic elongation, showed robust increases in the striatum, hippocampus, and cortices after a single dose of methamphetamine. The mRNAs of MAP kinase phosphatase-1 (MKP-1), MKP-3, and rheb, a ras homologue abundant in brain, were investigated to assess the MAP kinase cascades. MKP-1 and MKP-3 mRNAs, but not rheb mRNA, increased in the striatum, thalamus, and cortices, and in the striatum, hippocampus, and cortices, respectively, after a single methamphetamine. Synaptophysin and stathmin mRNAs did not increase again after chronic methamphetamine administration, whereas the increases in arc, MKP-1, and MKP-3 mRNAs persisted in the brain regions after chronic methamphetamine administration. These findings indicate that the earlier induction process in behavioral sensitization may require various plastic modifications, such as synaptogenesis, neuritic sprouting, neuritic elongation, and activation of MAP kinase cascades, throughout almost the entire brain. In contrast, later maintenance process of sensitization may require only limited plastic modification in restricted regions.
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Affiliation(s)
- Hiroshi Ujike
- Department of Neuropsychiatry, Okayama University Medical School and Graduate School of Medicine and Dentistry, Okayama, Japan.
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27
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Gil A, Gutiérrez LM, Carrasco-Serrano C, Alonso MT, Viniegra S, Criado M. Modifications in the C terminus of the synaptosome-associated protein of 25 kDa (SNAP-25) and in the complementary region of synaptobrevin affect the final steps of exocytosis. J Biol Chem 2002; 277:9904-10. [PMID: 11786540 DOI: 10.1074/jbc.m110182200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fusion proteins made of green fluorescent protein coupled to SNAP-25 or synaptobrevin were overexpressed in bovine chromaffin cells in order to study the role of critical protein domains in exocytosis. Point mutations in the C-terminal domain of SNAP-25 (K201E and L203E) produced a marked inhibition of secretion, whereas single (Q174K, Q53K) and double mutants (Q174K/Q53K) of amino acids from the so-called zero layer only produced a moderate alteration in secretion. The importance of the SNAP-25 C-terminal domain in exocytosis was also confirmed by the similar effect on secretion of mutations in analogous residues of synaptobrevin (A82D, L84E). The effects on the initial rate and magnitude of secretion correlated with the alteration of single vesicle fusion kinetics since the amperometric spikes from cells expressing SNAP-25 L203E and K201E and synaptobrevin A82D and L84E mutants had lower amplitudes and larger half-width values than the ones from controls, suggesting slower neurotransmitter release kinetics than that found in cells expressing the wild-type proteins or zero layer mutants of SNAP-25. We conclude that a small domain of the SNAP-25 C terminus and its counterpart in synaptobrevin play an essential role in the final membrane fusion step of exocytosis.
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Affiliation(s)
- Anabel Gil
- Department of Biochemistry and Molecular Biology and the Instituto de Neurociencias, Universidad Miguel Hernández-Consejo Superior de Investigaciones Cientificas, 03550 San Juan, Alicante, Spain
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28
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Meijer IA, Hand CK, Grewal KK, Stefanelli MG, Ives EJ, Rouleau GA. A locus for autosomal dominant hereditary spastic ataxia, SAX1, maps to chromosome 12p13. Am J Hum Genet 2002; 70:763-9. [PMID: 11774073 PMCID: PMC384953 DOI: 10.1086/338933] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2001] [Accepted: 11/29/2001] [Indexed: 11/03/2022] Open
Abstract
The hereditary spastic ataxias (HSA) are a group of clinically heterogeneous neurodegenerative disorders characterized by lower-limb spasticity and generalized ataxia. HSA was diagnosed in three unrelated autosomal dominant families from Newfoundland, who presented mainly with severe leg spasticity, dysarthria, dysphagia, and ocular-movement abnormalities. A genomewide scan was performed on one family, and linkage to a novel locus for HSA on chromosome 12p13, which contains the as-yet-unidentified gene locus SAX1, was identified. Fine mapping confirmed linkage in the two large families, and the third, smaller family showed LOD scores suggestive of linkage. Haplotype construction by use of 13 polymorphic markers revealed that all three families share a disease haplotype, which key recombinants and overlapping haplotypes refine to about 5 cM, flanked by markers D12S93 and GATA151H05. SAX1 is the first locus mapped for autosomal dominant HSA.
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Affiliation(s)
- I. A. Meijer
- Centre for Research in Neuroscience, McGill University and the McGill University Health Centre Research Institute, Montreal; and Discipline of Medical Genetics and Division of Neurology, Faculty of Medicine, Health Sciences Centre, Memorial University, Saint John’s, Newfoundland
| | - C. K. Hand
- Centre for Research in Neuroscience, McGill University and the McGill University Health Centre Research Institute, Montreal; and Discipline of Medical Genetics and Division of Neurology, Faculty of Medicine, Health Sciences Centre, Memorial University, Saint John’s, Newfoundland
| | - K. K. Grewal
- Centre for Research in Neuroscience, McGill University and the McGill University Health Centre Research Institute, Montreal; and Discipline of Medical Genetics and Division of Neurology, Faculty of Medicine, Health Sciences Centre, Memorial University, Saint John’s, Newfoundland
| | - M. G. Stefanelli
- Centre for Research in Neuroscience, McGill University and the McGill University Health Centre Research Institute, Montreal; and Discipline of Medical Genetics and Division of Neurology, Faculty of Medicine, Health Sciences Centre, Memorial University, Saint John’s, Newfoundland
| | - E. J. Ives
- Centre for Research in Neuroscience, McGill University and the McGill University Health Centre Research Institute, Montreal; and Discipline of Medical Genetics and Division of Neurology, Faculty of Medicine, Health Sciences Centre, Memorial University, Saint John’s, Newfoundland
| | - G. A. Rouleau
- Centre for Research in Neuroscience, McGill University and the McGill University Health Centre Research Institute, Montreal; and Discipline of Medical Genetics and Division of Neurology, Faculty of Medicine, Health Sciences Centre, Memorial University, Saint John’s, Newfoundland
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29
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Abstract
Vesicle associated membrane protein (VAMP; also known as synaptobrevin) is a key component of the core complex needed for docking and fusion of synaptic vesicles with the presynaptic plasma membrane. Recent work indicates that the precise complement of presynaptic proteins associated with transmitter release and their isoforms vary among synapses, presumably conferring specific functional release properties. The retina contains two types of vesicular synapses with distinct morphologic, functional, and biochemical characteristics: ribbon and conventional synapses. Although the precise complement of presynaptic proteins is known to differ between conventional and ribbon synapses and among conventional synapses, the distribution of VAMP isoforms among retinal synapses has not been determined. The expression and localization of VAMP isoforms in the salamander retina, a major model system for studies of retinal circuitry, was examined by using immunocytochemical and immunoblotting methods. Both methods indicated that at least two VAMP isoforms were expressed in salamander retina. One isoform, recognized by an immunoglobulin M antibody that recognizes both mammalian VAMP-1 and VAMP-2, was associated with photoreceptor and bipolar cell terminals as well as many conventional synapses, and probably corresponds to mammalian VAMP-2. A different VAMP isoform associated with a subset of amacrine cells, was recognized only by antibodies directed against the N-terminus of mammalian VAMP-2. An antiserum directed against the N-terminus of mammalian VAMP-1 did not specifically recognize any salamander VAMPs in either immunocytochemical or immunoblotting experiments. Heterogeneous distribution of VAMP isoforms among conventional retinal synapses was confirmed by double labeling for synapsin I, a marker for conventional synapses. These studies indicate that VAMP isoforms are expressed heterogeneously among retinal synapses but cannot account for the differences in transmitter release characteristics at ribbon and conventional synapses. These results also corroborate previous studies in Xenopus indicating that the N-terminus of nonmammalian VAMP isoforms differs from their mammalian counterparts.
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Affiliation(s)
- D M Sherry
- College of Optometry, University of Houston, Houston, Texas 77004, USA.
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30
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Sokolov BP, Tcherepanov AA, Haroutunian V, Davis KL. Levels of mRNAs encoding synaptic vesicle and synaptic plasma membrane proteins in the temporal cortex of elderly schizophrenic patients. Biol Psychiatry 2000; 48:184-96. [PMID: 10924661 DOI: 10.1016/s0006-3223(00)00875-1] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Electron microscopy and biochemical studies indicate that developmental abnormalities in synaptic organization may be present in brains of schizophrenic patients. This study determined whether these synaptic abnormalities are reflected in differential or uniform alterations in the expression of various synaptic protein genes in the left superior temporal gyrus of schizophrenic patients. METHODS Levels of mRNAs encoding four synaptic vesicle proteins (synaptotagmin I [p65], rab3a, synaptobrevin 1, and synaptobrevin 2) and two synaptic plasma membrane proteins (syntaxin 1A and SNAP-25) were measured postmortem in the left superior temporal gyrus from elderly (58-95 years) schizophrenic patients (n = 14) and age-matched control subjects (n = 9). RESULTS There were significant negative correlations between age and levels of synaptotagmin I (p65), rab3a, synaptobrevin 1, SNAP-25, and syntaxin 1A mRNAs in schizophrenic patients (-.692 < r < -.517,.003 < p <.030) but not in control subjects. Levels of all six synaptic mRNAs studied were increased in the younger (58-79 years) subgroup of schizophrenic patients compared to control subjects and older (80-95 years) subgroup of schizophrenic patients. CONCLUSIONS That similar abnormalities were found for mRNAs encoding different synaptic vesicle and synaptic plasma membrane proteins suggests that they reflect overall neurodevelopmental abnormalities in synaptic connectivity in the temporal cortex of schizophrenic patients rather than changes in the number of synaptic vesicles per synapse or abnormalities in a specific synaptic function.
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Affiliation(s)
- B P Sokolov
- Molecular Neurobiology Branch, National Institute on Drug Abuse, National Institutes of Health, (BPS), Baltimore, MD 21224, USA
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31
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Sachetto-Martins G, Franco LO, de Oliveira DE. Plant glycine-rich proteins: a family or just proteins with a common motif? BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1492:1-14. [PMID: 10858526 DOI: 10.1016/s0167-4781(00)00064-6] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Twelve years ago a set of glycine-rich proteins (GRP) of plants were characterized and since then a wealth of new GRPs have been identified. The highly specific but diverse expression pattern of grp genes, taken together with the distinct sub-cellular localisation of some GRP groups, clearly indicate that these proteins are implicated in several independent physiological processes. Notwithstanding the absence of a clear definition of the role of GRPs in plant cells, studies conducted with these proteins have provided new and interesting insights on the molecular and cell biology of plants. Complex regulated promoters and distinct mechanisms of gene expression regulation have been demonstrated. New protein targeting pathways, as well as the exportation of GRPs from different cell types have been discovered. These data show that GRPs can be useful as markers and/or models to understand distinct aspects of plant biology. In this review, the structural and functional features of this family of plant proteins will be summarised. Special emphasis will be given to the gene expression regulation of GRPs isolated from different plant species, as it can help to unravel their possible biological functions.
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Affiliation(s)
- G Sachetto-Martins
- Laboratório de Genética Molecular Vegetal, Departamento de Genética, Universidade Federal do Rio de Janeiro, C.P. 68011, Rio de Janeiro 21941-970, Brazil.
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32
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Abstract
Genetic lesions in the p53 tumor suppressor gene are the most frequently observed alterations in human cancers. Typically in tumors, one allele of the p53 gene is initially mutated, followed by deletion of the remaining wildtype allele. In human colon cancer, for example, approximately 70% of late stage tumors are hemizygous mutant p53. Since the precise gene environment surrounding the p53 gene is not known, the neighboring genes concomitantly lost with wildtype p53 deletion remain undetermined. A restriction enzyme map and clone array of 1.1 Mb surrounding the p53 gene were constructed using a combination of YAC, BAC, NotI linking, and NotI jumping clones. The resulting physical map and clone array include approximately 400 kb telomeric and 700 kb centromeric to the p53 gene. Sequence determination and analysis adjacent to NotI and AscI sites, indicative of CpG islands, allowed the rapid identification of numerous genes within the cloned region. Twenty-seven transcription units were identified, including 18 characterized genes. Limited analysis of primary human colon tumors, hemizygous for the p53 gene, indicates loss of the entire 1.1-Mb region upon deletion of wildtype p53.
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Affiliation(s)
- P Cousin
- Institute of Pathology, CHUV, Lausanne, Switzerland
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33
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Gasparian M, Pusterla M, Baldan B, Downey PM, Rossetto O, de Laureto PP, Filippini F, Terzi M, Lo Schiavo F. Identification and characterization of an 18-kilodalton, VAMP-like protein in suspension-cultured carrot cells. PLANT PHYSIOLOGY 2000; 122:25-34. [PMID: 10631246 PMCID: PMC58841 DOI: 10.1104/pp.122.1.25] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/1999] [Accepted: 09/17/1999] [Indexed: 05/23/2023]
Abstract
Polyclonal antibodies raised against rat vesicle associated membrane protein-2 (VAMP-2) recognized, in carrot (Daucus carota) microsomes, two major polypeptides of 18 and 30 kD, respectively. A biochemical separation of intracellular membranes by a sucrose density gradient co-localized the two polypeptides as resident in light, dense microsomes, corresponding to the endoplasmic reticulum-enriched fractions. Purification of coated vesicles allowed us to distinguish the subcellular location of the 18-kD polypeptide from that of 30 kD. The 18-kD polypeptide is present in the non-clathrin-coated vesicle peak. Like other VAMPs, the carrot 18-kD polypeptide is proteolyzed by tetanus toxin after separation of coatomers. Amino acid sequence analysis of peptides obtained by digestion of the 18-kD carrot polypeptide with the endoproteinase Asp-N confirms it to be a member of the VAMP family, as is suggested by its molecular weight, vesicular localization, and toxin-induced cleavage.
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Affiliation(s)
- M Gasparian
- Dipartimento di Biologia, Universit¿a di Padova, Viale Giuseppe Colombo 3, 35131 Padova, Italy
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34
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Berglund L, Hoffmann HJ, Dahl R, Petersen TE. VAMP-1 has a highly variable C-terminus generated by alternative splicing. Biochem Biophys Res Commun 1999; 264:777-80. [PMID: 10544008 DOI: 10.1006/bbrc.1999.1588] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
VAMP-1 (synaptobrevin1) is one of the key proteins in the SNARE complex which is involved in regulated exocytosis. Recently, Isenmann et al. (1998, Mol. Biol. Cell 9, 1649-1660) showed the extreme C-terminal region of VAMP-1A and 1B to be involved in subcellular targeting of the isoforms. Four new splice variants (VAMP-1C to F) were identified in addition to the previously published variants VAMP-1A and VAMP-1B. Interestingly, the four new isoforms also have variable sequences only at the extreme C-terminus. This suggests that the C-terminal region has an important function for VAMP-1 and vesicle targeting. All six variants were a result of alternative splicing that linked exons 1-4 which encode the conserved region of VAMP-1 with one of the exons 5A to 5F that encodes the highly variable extreme C-terminus. Exon (5A-E) encode C-termini of two to five amino acid residues, whereas exon 5F encoded a long C-terminal amino acid extension. The splice variants were differentially expressed in human brain, kidney, and inflammatory cells.
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Affiliation(s)
- L Berglund
- Protein Chemistry Laboratory, Department of Molecular and Structural Biology, University of Aarhus, Gustav Wieds Vej 10 C, Aarhus C, DK-8000, Denmark.
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35
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Mandic R, Lowe AW. Characterization of an alternatively spliced isoform of rat vesicle associated membrane protein-2 (VAMP-2). FEBS Lett 1999; 451:209-13. [PMID: 10371166 DOI: 10.1016/s0014-5793(99)00551-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
VAMPs are vesicle associated membrane proteins that are essential for secretion. A spliced isoform of rat VAMP-2, called VAMP-2B, is characterized in this study. The VAMP-2B transcript is the result of alternative RNA splicing in which an intron is retained. The predicted amino acid sequence of VAMP-2B differs from VAMP-2 at its carboxy-terminal end. Because recent studies have shown that VAMP's carboxy-terminal end influences the protein's sorting, the location of myc-epitope tagged VAMP-2B in PC12 cells was determined. Subcellular fractionation showed colocalization of myc-VAMP-2B and endogenous VAMP-2. Thus alternative RNA splicing does not affect VAMP-2 sorting in PC12 cells.
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Affiliation(s)
- R Mandic
- Department of Medicine and the Digestive Disease Center, Stanford University, CA 94305-5487, USA
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36
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Cánaves JM, Montal M. Assembly of a ternary complex by the predicted minimal coiled-coil-forming domains of syntaxin, SNAP-25, and synaptobrevin. A circular dichroism study. J Biol Chem 1998; 273:34214-21. [PMID: 9852083 DOI: 10.1074/jbc.273.51.34214] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The assembly of target (t-SNARE) and vesicle-associated SNAP receptor (v-SNARE) proteins is a critical step for the docking of synaptic vesicles to the plasma membrane. Syntaxin-1A, SNAP-25, and synaptobrevin-2 (also known as vesicle-associated membrane protein, or VAMP-2) bind to each other with high affinity, and their binding regions are predicted to form a trimeric coiled-coil. Here, we have designed three peptides, which correspond to sequences located in the syntaxin-1A H3 domain, the C-terminal domain of SNAP-25, and a conserved central domain of synaptobrevin-2, that exhibit a high propensity to form a minimal trimeric coiled-coil. The peptides were synthesized by solid phase methods, and their interactions were studied by CD spectroscopy. In aqueous solution, the peptides were unstructured and showed no interactions with each other. In contrast, upon the addition of moderate amounts of trifluoroethanol (30%), the peptides adopted an alpha-helical structure and displayed both homomeric and heteromeric interactions. The interactions observed in ternary mixtures induce a stabilization of peptide structure that is greater than that predicted from individual binary interactions, suggesting the formation of a higher order structure compatible with the assembly of a trimeric coiled-coil.
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Affiliation(s)
- J M Cánaves
- Department of Biology, University of California San Diego, La Jolla, California 92093-0366, USA
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37
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Bui TD, Wong SH, Lu L, Hong W. Endobrevin maps to chromosome 2 in human and chromosome 6 in mouse. Genomics 1998; 54:579-80. [PMID: 9878266 DOI: 10.1006/geno.1998.5596] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- T D Bui
- Membrane Biology Laboratory, Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore, 117609, Singapore
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38
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Honsho M, Mitoma JY, Ito A. Retention of cytochrome b5 in the endoplasmic reticulum is transmembrane and luminal domain-dependent. J Biol Chem 1998; 273:20860-6. [PMID: 9694832 DOI: 10.1074/jbc.273.33.20860] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cytochrome b5 (b5), a typical tail-anchored protein of the endoplasmic reticulum (ER) membrane, is composed of three functionally different domains: amino-terminal heme-containing catalytic, central hydrophobic membrane-anchoring, and carboxyl-terminal ER-targeting domains (Mitoma, J., and Ito, A. (1992) EMBO J. 11, 4197-4203). To analyze the potential retention signal of b5, mutant proteins were prepared to replace each domain with natural or artificial sequences, and subcellular localizations were examined using immunofluorescence microscopy and cell fractionation. The transmembrane domain functioned to retain the cytochrome in the ER, and the mutation of all or part of the transmembrane domain with an artificial hydrophobic sequence had practically no effect on intracellular distribution of the cytochrome. However, when the transmembrane domain was extended systematically, a substantial portion of the protein with the domain of over 22 amino acid residues leaked from the organelle. Thus, the transmembrane length functions as the retention signal. When cytochromes with mutations at the carboxyl-terminal end were overexpressed in cells, a substantial portion of the protein was transported to the plasma membrane, indicating that the carboxyl-terminal luminal domain also has a role in retention of b5 in the ER. Carbohydrate moiety of the glycosylatably-mutated b5 was sensitive to endoglycosidase H but resistant to endoglycosidase D. Therefore, both transmembrane and carboxyl-terminal portions seems to function as the static retention signal.
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Affiliation(s)
- M Honsho
- Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka 812-8581, Japan
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39
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Isenmann S, Khew-Goodall Y, Gamble J, Vadas M, Wattenberg BW. A splice-isoform of vesicle-associated membrane protein-1 (VAMP-1) contains a mitochondrial targeting signal. Mol Biol Cell 1998; 9:1649-60. [PMID: 9658161 PMCID: PMC25402 DOI: 10.1091/mbc.9.7.1649] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Screening of a library derived from primary human endothelial cells revealed a novel human isoform of vesicle-associated membrane protein-1 (VAMP-1), a protein involved in the targeting and/or fusion of transport vesicles to their target membrane. We have termed this novel isoform VAMP-1B and designated the previously described isoform VAMP-1A. VAMP-1B appears to be an alternatively spliced form of VAMP-1. A similar rat splice variant of VAMP-1 (also termed VAMP-1B) has recently been reported. Five different cultured cell lines, from different lineages, all contained VAMP-1B but little or no detectable VAMP-1A mRNA, as assessed by PCR. In contrast, brain mRNA contained VAMP-1A but no VAMP-1B. The VAMP-1B sequence encodes a protein identical to VAMP-1A except for the carboxy-terminal five amino acids. VAMP-1 is anchored in the vesicle membrane by a carboxy-terminal hydrophobic sequence. In VAMP-1A the hydrophobic anchor is followed by a single threonine, which is the carboxy-terminal amino acid. In VAMP-1B the predicted hydrophobic membrane anchor is shortened by four amino acids, and the hydrophobic sequence is immediately followed by three charged amino acids, arginine-arginine-aspartic acid. Transfection of human endothelial cells with epitope-tagged VAMP-1B demonstrated that VAMP-1B was targeted to mitochondria whereas VAMP-1A was localized to the plasma membrane and endosome-like structures. Analysis of C-terminal mutations of VAMP-1B demonstrated that mitochondrial targeting depends both on the addition of positive charge at the C terminus and a shortened hydrophobic membrane anchor. These data suggest that mitochondria may be integrated, at least at a mechanistic level, to the vesicular trafficking pathways that govern protein movement between other organelles of the cell.
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Affiliation(s)
- S Isenmann
- Division of Human Immunology, Hanson Centre for Cancer Research, Adelaide 5000, South Australia, Australia
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40
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Saifee O, Wei L, Nonet ML. The Caenorhabditis elegans unc-64 locus encodes a syntaxin that interacts genetically with synaptobrevin. Mol Biol Cell 1998; 9:1235-52. [PMID: 9614171 PMCID: PMC25346 DOI: 10.1091/mbc.9.6.1235] [Citation(s) in RCA: 183] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/1998] [Accepted: 03/05/1998] [Indexed: 11/11/2022] Open
Abstract
We describe the molecular cloning and characterization of the unc-64 locus of Caenorhabditis elegans. unc-64 expresses three transcripts, each encoding a molecule with 63-64% identity to human syntaxin 1A, a membrane- anchored protein involved in synaptic vesicle fusion. Interestingly, the alternative forms of syntaxin differ only in their C-terminal hydrophobic membrane anchors. The forms are differentially expressed in neuronal and secretory tissues; genetic evidence suggests that these forms are not functionally equivalent. A complete loss-of-function mutation in unc-64 results in a worm that completes embryogenesis, but arrests development shortly thereafter as a paralyzed L1 larva, presumably as a consequence of neuronal dysfunction. The severity of the neuronal phenotypes of C. elegans syntaxin mutants appears comparable to those of Drosophila syntaxin mutants. However, nematode syntaxin appears not to be required for embryonic development, for secretion of cuticle from the hypodermis, or for the function of muscle, in contrast to Drosophila syntaxin, which appears to be required in all cells. Less severe viable unc-64 mutants exhibit a variety of behavioral defects and show strong resistance to the acetylcholinesterase inhibitor aldicarb. Extracellular physiological recordings from pharyngeal muscle of hypomorphic mutants show alterations in the kinetics of transmitter release. The lesions in the hypomorphic alleles map to the hydrophobic face of the H3 coiled-coil domain of syntaxin, a domain that in vitro mediates physical interactions with similar coiled-coil domains in SNAP-25 and synaptobrevin. Furthermore, the unc-64 syntaxin mutants exhibit allele-specific genetic interactions with mutants carrying lesions in the coiled-coil domain of synaptobrevin, providing in vivo evidence for the significance of these domains in regulating synaptic vesicle fusion.
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Affiliation(s)
- O Saifee
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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41
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Middleton LT, Christodoulou K, Deymeer F, Serdaroglu P, Ozdemir C, al-Qudah AK, al-Shehab A, Mavromatis I, Mylonas I, Evoli A, Tsingis M, Zamba E, Kyriallis K. Congenital myasthenic syndrome. (CMS) type Ia. Clinical and genetic diversity. Ann N Y Acad Sci 1998; 841:157-66. [PMID: 9668234 DOI: 10.1111/j.1749-6632.1998.tb10922.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- L T Middleton
- Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
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42
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Fleming JC, Berger G, Guichard J, Cramer EM, Wagner DD. The transmembrane domain enhances granular targeting of P-selectin. Eur J Cell Biol 1998; 75:331-43. [PMID: 9628319 DOI: 10.1016/s0171-9335(98)80066-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
P-selectin is an integral membrane glycoprotein that is stored in granules of endothelial cells and platelets. The cytoplasmic domain of P-selectin is known to contain at least part of the signal that directs the protein to storage granules. In order to more fully understand how P-selectin is targeted to the regulated secretory pathway, we have expressed chimeric constructs between P- and E-selectin, a protein which is expressed on the cell surface, in a rat insulinoma cell line. Immunofluorescence studies indicated that replacing the cytoplasmic domain of E-selectin with that of P-selectin resulted in low-level granular expression. In contrast, when both the transmembrane and cytoplasmic domains of E-selectin were replaced with the analogous domains of P-selectin, the granular localization appeared greatly increased. This was confirmed by immunoelectron microscopy which demonstrated a three- to fourfold improvement in granular targeting, i.e. similar to wild-type P-selectin. The transmembrane domain had to be in the context of the P-selectin cytoplasmic domain as this membrane-spanning region could not induce granular targeting on its own. These results describe a novel function for the transmembrane domain of P-selectin in enhancing the efficiency of granular targeting and further implicate protein transmembrane domains in intracellular trafficking.
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Affiliation(s)
- J C Fleming
- Program in Cell, Molecular and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, USA
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43
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Fischer von Mollard G, Stevens TH. A human homolog can functionally replace the yeast vesicle-associated SNARE Vti1p in two vesicle transport pathways. J Biol Chem 1998; 273:2624-30. [PMID: 9446565 DOI: 10.1074/jbc.273.5.2624] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Membrane traffic in eukaryotic cells requires the interaction of a vesicle-associated soluble NSF attachment protein receptor (v-SNARE) on transport vesicles with a SNARE on the target membrane (t-SNARE). Recently, we identified the yeast protein Vti1p as a v-SNARE that is involved in two transport reactions. Vti1p interacts with the prevacuolar t-SNARE Pep12p in Golgi to prevacuolar transport and with the cis-Golgi t-SNARE Sed5p in traffic to the cis-Golgi. Here we describe a human Vti1p homolog, hVti1. Whereas vti1Delta cells are inviable, expression of hVti1 allows vti1Delta cells to grow at nearly the wild-type growth rate. When expressed in yeast hVti1 can replace Vti1p in both Golgi to prevacuolar transport and in traffic to the cis-Golgi. Sequence comparisons with a Schizosaccharomyces pombe and two different mouse Vti1 homologs led to the identification of a very conserved predicted alpha-helix. Amino acid exchanges in vti1 mutant alleles defective either in one or both trafficking steps cluster in this domain, suggesting that this structure is probably the binding site for effector proteins.
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Affiliation(s)
- G Fischer von Mollard
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403-1229, USA
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44
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Jacobsson G, Piehl F, Meister B. VAMP-1 and VAMP-2 gene expression in rat spinal motoneurones: differential regulation after neuronal injury. Eur J Neurosci 1998; 10:301-16. [PMID: 9753139 DOI: 10.1046/j.1460-9568.1998.00050.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Vesicle-associated membrane protein (VAMP; synaptobrevin) is involved in the molecular regulation of transmitter release at the presynaptic plasma membrane. VAMP exists in two isoforms, VAMP-1 and VAMP-2, which are transcribed from two separate genes and differentially expressed in the nervous system. In situ hybridization was used to examine whether VAMP isoform mRNA expression may be altered by experimental manipulations. The effect of nerve injury on VAMP-1 and VAMP-2 mRNA levels in motoneurones of the rat lumbar spinal cord was compared with lesion-induced changes in the expression of choline acetyl transferase (ChAT) and alpha-calcitonin gene-related peptide (alpha-CGRP) mRNA. After unilateral sciatic nerve transection (axotomy), VAMP-1 mRNA expression decreased significantly in parallel with a downregulation of ChAT mRNA in axotomized motoneurones compared with the corresponding motoneurones on the contralateral unlesioned side. There was a rapid decrease in VAMP-1 and ChAT mRNA levels at 2 days after axotomy, and at 7 days there was a 65% decrease in VAMP-1 mRNA and a 48% decrease in ChAT mRNA. VAMP-1 mRNA levels continued to decrease at 14 and 21 days, while ChAT mRNA levels had returned to normal at this time. In contrast, VAMP-2 and alpha-CGRP mRNA levels were upregulated in axotomized motoneurones. A significant increase for both VAMP-2 and alpha-CGRP mRNA levels was present 2 days after axotomy, and a maximum was reached after 7 days for alpha-CGRP mRNA (163%) and after 14 days for VAMP-2 mRNA (587%). Immunohistochemical analysis did not reveal any detectable changes in VAMP-1- or VAMP-2-like immunoreactivity in the motoneurone cell soma after axotomy. In the proximal end of the transected sciatic nerve, there was an increase in VAMP-1- and VAMP-2-LI, which was most prominent at 2 days after lesion. The results show that, in axotomized spinal motoneurones, VAMP-1 mRNA is downregulated and VAMP-2 mRNA is upregulated, indicating differential regulation of the two separate VAMP genes and differential roles for the two VAMP isoforms in the regulation of exocytosis after nerve injury.
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Affiliation(s)
- G Jacobsson
- Department of Neuroscience, Karolinska Institute, Stockholm, Sweden
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45
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Mandic R, Trimble WS, Lowe AW. Tissue-specific alternative RNA splicing of rat vesicle-associated membrane protein-1 (VAMP-1). Gene 1997; 199:173-9. [PMID: 9358054 DOI: 10.1016/s0378-1119(97)00244-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The vesicle-associated membrane protein (VAMP) family is essential to vesicle-mediated protein transport. Three mammalian isoforms, VAMP-1, VAMP-2, and cellubrevin, play a role in protein transport to the plasma membrane. In this study, we describe a new rat VAMP-1 isoform produced by alternative pre-mRNA splicing. Only one VAMP-1 isoform dominates in each tissue. Analysis of the nucleotide sequence for the newly discovered isoform, VAMP-1b, reveals that its expression is determined by whether an intron is retained or removed. The predicted amino acid sequences for the VAMP-1 isoforms differ at the carboxy-terminal end of the protein. A similar process has been described for VAMPs in Drosophila melanogaster and suggests a conserved function for the carboxy-terminal domain that can be modulated.
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Affiliation(s)
- R Mandic
- Department of Medicine and the Digestive Disease Center, Stanford University School of Medicine, CA 94305-5487, USA
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Hicks A, Davis S, Rodger J, Helme-Guizon A, Laroche S, Mallet J. Synapsin I and syntaxin 1B: key elements in the control of neurotransmitter release are regulated by neuronal activation and long-term potentiation in vivo. Neuroscience 1997; 79:329-40. [PMID: 9200718 DOI: 10.1016/s0306-4522(96)00700-2] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The messenger RNAs encoding proteins of the exocytotic machinery were measured at different times following the induction of long-term potentiation or increasing neuronal activity in the dentate gyrus of the rat in vivo. In situ hybridization revealed that from the many messenger RNAs that encode proteins involved in regulated exocytosis, only those encoding synapsin I and syntaxin 1B were specifically increased. The levels of messenger RNA encoding both synapsin I and syntaxin 1B were increased on the ipsilateral side of the dorsal dentate gyrus 2 and 5 h following the induction of long-term potentiation. Syntaxin 1B was also increased in the ventral dentate gyrus at the same time-points. On the contralateral side of the dentate gyrus there was an increase in both synapsin I and syntaxin 1B at 5 h only. All of these long-term potentiation-induced changes were prevented when the tetanus was delivered in the presence of the N-methyl-D-aspartate receptor antagonist. (D(-)-2-amino-5-phosphonopentanoic acid. Immunocytochemical staining revealed that protein levels for both synapsin I and syntaxin 1B were elevated in the mossy fibre terminal zone of CA3 5 h after the induction of long-term potentiation. In addition to these plasticity-induced changes, a transient increase in the messenger RNA encoding syntaxin 1B was observed at 2 h in conditions of high intensity stimulation of the perforant path to increase the level of cellular activation, but this change was not maintained even when high intensity stimulation was sustained for 5 h. No changes in either of the messenger RNAs were observed under low frequency stimulation and pseudotetanus at either time-points. These results show that an overall increase in neuronal excitation within a neuronal network can be differentiated from a change in synaptic strength at a specific subset of the synapses, where only synaptic plasticity leads to long-term changes in the expression of selective members of the exocytotic machinery. Altered concentrations of key vesicle proteins may thus provide the means for modulation of neurotransmitter release over long time-periods. The persistent long-term potentiation-induced postsynaptic increase in messenger RNAs encoding these presynaptic proteins has important implications for the propagation of signals downstream from the site of long-term potentiation induction in hippocampal neural networks, and highlights a candidate molecular mechanism for mediating the propagation of synaptic plasticity in such networks.
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Affiliation(s)
- A Hicks
- Laboratoire de Génétique Moléculaire de la Neurotransmission et des Processus Neurodégénératifs, CNRS UMR C9923, Hôpital de la Pitié Salpêtrière, Paris, France
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Pellizzari R, Mason S, Shone CC, Montecucco C. The interaction of synaptic vesicle-associated membrane protein/synaptobrevin with botulinum neurotoxins D and F. FEBS Lett 1997; 409:339-42. [PMID: 9224685 DOI: 10.1016/s0014-5793(97)00482-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Botulinum neurotoxins type D and F are zinc-endopeptidases with a unique specificity for VAMP/synaptobrevin, an essential component of the exocytosis apparatus. VAMP contains two copies of a nine residue motif, termed V1 and V2, which are determinants of the interaction with tetanus and botulinum B and G neurotoxins. Here, we show that V1 plays a major role in VAMP recognition by botulinum neurotoxins D and F and that V2 is also involved in F binding. Site-directed mutagenesis of V1 and V2 indicates that different residues are the determinants of the VAMP interaction with the two endopeptidases. The study of the VAMP-neurotoxins interaction suggest a pairing of the V1 and V2 segments.
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Affiliation(s)
- R Pellizzari
- Centro CNR Biomembrane, Dipartimento di Scienze Biomediche, Università di Padova, Italy
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Mosevitsky MI, Capony JP, Novitskaya VA, Zakharov VV. The BASP1 family of myristoylated proteins abundant in axonal termini. Primary structure analysis and physico-chemical properties. Biochimie 1997; 79:373-84. [PMID: 9310187 DOI: 10.1016/s0300-9084(97)80032-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Proteins BASP1 and GAP-43/B-50, which are abundant in nerve endings, show a number of similar physico-chemical properties. Nevertheless, they belong to different protein families. In this work, complete amino acid sequences of bovine BASP1 and human BASP1 were established. They proved to be very similar to the sequences of rat brain protein NAP-22 and chicken brain protein CAP-23. Relatively to human BASP1 its bovine, rat and chicken analogues show 80%, 70% and 45% sequence identity respectively, confirming their membership of a definite protein family (BASP1 family). All members of BASP1 family contain several 'good' PEST sequences characteristic for short-living proteins. Conservation of PEST sequences in BASP1 of different species points to their significance for BASP1 functions. In contrast to GAP-43/B-50 showing high immunological cross-reactivity between the proteins belonging to different species of mammals, immunological properties of BASP1 are species specific. BASP1 shows both high hydrophilicity and some properties characteristic for hydrophobic proteins. These properties are caused by N-terminal myristoylation of BASP1 molecules. Unlike GAP-43/B-50, BASP1 is present in high amounts also in some non-nervous tissues: testis, kidney and lymphoid organs (spleen, thymus). So far examined characteristics, including myristoylation, peptide maps and detected by isoelectrofocusing microheterogeneity, proved to be the same for BASP1 samples isolated from both brain and non-nervous tissues. Therefore, in spite of different physiological consequences, biochemical functions of BASP1 must also be similar in different tissues.
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Affiliation(s)
- M I Mosevitsky
- Division of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute, Russia Academy of Sciences, Leningrad District
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Storms RK, Wang Y, Fortin N, Hall J, Vo DH, Zhong WW, Downing T, Barton AB, Kaback DB, Su Y, Bussey H. Analysis of a 103 kbp cluster homology region from the left end of Saccharomyces cerevisiae chromosome I. Genome 1997; 40:151-64. [PMID: 9061922 DOI: 10.1139/g97-022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The DNA sequence and preliminary functional analysis of a 103-kbp section of the left arm of yeast chromosome I is presented. This region, from the left telomere to the LTE1 gene, can be divided into two distinct portions. One portion, the telomeric 29 kbp, has a very low gene density (only five potential genes and 21 kbp of noncoding sequence), does not encode any "functionally important" genes, and is rich in sequences repeated several times within the yeast genome. The other portion, with 37 genes and only 14.5 kbp of noncoding sequence, is gene rich and codes for at least 16 "functionally important" genes. The entire gene-rich portion is apparently duplicated on chromosome XV as an extensive region of partial gene synteney called a cluster homology region. A function can be assigned with varying degrees of precision to 23 of the 42 potential genes in this region; however, the precise function is know for only eight genes. Nineteen genes encode products presently novel to yeast, although five of these have homologs elsewhere in the yeast genome.
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Affiliation(s)
- R K Storms
- Department of Biology, Concordia University, Montreal, Canada.
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50
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Abstract
1. It now appears that when water crosses an endothelium which is not fenestrated, or an epithelium with tight junctions, it does so rapidly, and with low energy cost, only if the cell membrane contains an adequate number of specific water channels, encoded by one of at least six different genes. 2. The water channel genes so far cloned encode a series of integral membrane proteins called aquaporins, all of approximately 30 kDa (265-282 amino acids), in the unglycosylated state. All but one (AQP3) are specific water channels and all but one (AQP4) are inactivated by mercurial compounds. 3. Aquaporin 0 is the major (60%) intrinsic protein (MIP) of lens fibre cells of the eye. Mutations in this gene are associated with cataract formation in mice. 4. Aquaporin 1, also called CHIP-28, exists in the membrane as a homotetramer, and is present in red blood cells, the choroid plexus, the proximal tubule and descending limb of the loop of Henle in the kidney as well as in many other sites. Surprisingly, no pathological consequence is known in patients lacking a functional AQP1 gene. 5. Aquaporin 2, also called WCH-CD, is the water channel of the principal cell of the cortical and medullary collecting duct, and is located in cytoplasmic vesicles unless arginine vasopressin is acting, when it is translocated to the apical membrane by synaptobrevins or vesicle associated membrane protein 2 (VAMP2). Lack of a functional AQP2 gene leads to a rare form of nephrogenic diabetes insipidus. 6. Aquaporins 3, 4, and 5 are located in many tissues-AQP3 and AQP4 being in the basolateral membrane of the renal cortical and medullary principal cell, as well as in the gastrointestinal tract (AQP3) and the brain (AQP4). 7. Four sequences are known for urea transporters HUT11-the urea transporter of the human red cell membrane, and HUT2, rUT2, rbUT2-the arginine vasopressin inducible urea transporters of the human, rat and rabbit kidney. They are specifically permeable to urea, not to water, and are claimed to be inhibited by phloretin. 8. The water channel proteins contain six membrane-spanning regions, whilst the urea transporters are thought to contain at least 10 membrane spanning segments. 9. Very little work has examined the ontogeny of these proteins, except in the rat, and virtually nothing is known of the expression of these genes in pregnancy or in any disorder of fluid balance in the mother or foetus.
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Affiliation(s)
- E M Wintour
- Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria, Australia
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