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Bonab MKF, Guo Z, Li Q. Glycosphingolipids: from metabolism to chemoenzymatic total synthesis. Org Biomol Chem 2024; 22:6665-6683. [PMID: 39120686 PMCID: PMC11341264 DOI: 10.1039/d4ob00695j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2024]
Abstract
GSLs are the major glycolipids in vertebrates and mediate many key biological processes from intercellular recognition to cis regulation of signal transduction. The fast-expanding field of glycobiology has led to a growing demand for diverse and structurally defined GSLs, and enzymatic GSL synthesis is developing rapidly in accordance. This article provides an overview of natural GSL biosynthetic pathways and surveys the bacterial enzymes applied to GSL synthesis and recent progress in synthesis strategies. By correlating these three areas, this article aims to define the gaps between GSL biosynthesis and chemoenzymatic synthesis and evaluate the opportunities for harnessing natural forces to access GSLs efficiently.
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Affiliation(s)
- Mitra K F Bonab
- Department of Chemistry, University of Massachusetts Boston, Boston, Massachusetts 02125, USA.
| | - Zhongwu Guo
- Department of Chemistry, University of Florida, Gainesville, Florida 32611, USA.
| | - Qingjiang Li
- Department of Chemistry, University of Massachusetts Boston, Boston, Massachusetts 02125, USA.
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2
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Kadirvelraj R, Yang JY, Kim HW, Sanders JH, Moremen KW, Wood ZA. Comparison of human poly-N-acetyl-lactosamine synthase structure with GT-A fold glycosyltransferases supports a modular assembly of catalytic subsites. J Biol Chem 2021; 296:100110. [PMID: 33229435 PMCID: PMC7948508 DOI: 10.1074/jbc.ra120.015305] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 11/19/2020] [Accepted: 11/23/2020] [Indexed: 01/05/2023] Open
Abstract
Poly-N-acetyl-lactosamine (poly-LacNAc) structures are composed of repeating [-Galβ(1,4)-GlcNAcβ(1,3)-]n glycan extensions. They are found on both N- and O-glycoproteins and glycolipids and play an important role in development, immune function, and human disease. The majority of mammalian poly-LacNAc is synthesized by the alternating iterative action of β1,3-N-acetylglucosaminyltransferase 2 (B3GNT2) and β1,4-galactosyltransferases. B3GNT2 is in the largest mammalian glycosyltransferase family, GT31, but little is known about the structure, substrate recognition, or catalysis by family members. Here we report the structures of human B3GNT2 in complex with UDP:Mg2+ and in complex with both UDP:Mg2+ and a glycan acceptor, lacto-N-neotetraose. The B3GNT2 structure conserves the GT-A fold and the DxD motif that coordinates a Mg2+ ion for binding the UDP-GlcNAc sugar donor. The acceptor complex shows interactions with only the terminal Galβ(1,4)-GlcNAcβ(1,3)- disaccharide unit, which likely explains the specificity for both N- and O-glycan acceptors. Modeling of the UDP-GlcNAc donor supports a direct displacement inverting catalytic mechanism. Comparative structural analysis indicates that nucleotide sugar donors for GT-A fold glycosyltransferases bind in similar positions and conformations without conserving interacting residues, even for enzymes that use the same donor substrate. In contrast, the B3GNT2 acceptor binding site is consistent with prior models suggesting that the evolution of acceptor specificity involves loops inserted into the stable GT-A fold. These observations support the hypothesis that GT-A fold glycosyltransferases employ coevolving donor, acceptor, and catalytic subsite modules as templates to achieve the complex diversity of glycan linkages in biological systems.
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Affiliation(s)
- Renuka Kadirvelraj
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Jeong-Yeh Yang
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Hyun W Kim
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Justin H Sanders
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Kelley W Moremen
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, Georgia, USA; Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA.
| | - Zachary A Wood
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, Georgia, USA.
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3
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Sudhakar JN, Lu HH, Chiang HY, Suen CS, Hwang MJ, Wu SY, Shen CN, Chang YM, Li FA, Liu FT, Shui JW. Lumenal Galectin-9-Lamp2 interaction regulates lysosome and autophagy to prevent pathogenesis in the intestine and pancreas. Nat Commun 2020; 11:4286. [PMID: 32855403 PMCID: PMC7453023 DOI: 10.1038/s41467-020-18102-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 08/05/2020] [Indexed: 12/14/2022] Open
Abstract
Intracellular galectins are carbohydrate-binding proteins capable of sensing and repairing damaged lysosomes. As in the physiological conditions glycosylated moieties are mostly in the lysosomal lumen but not cytosol, it is unclear whether galectins reside in lysosomes, bind to glycosylated proteins, and regulate lysosome functions. Here, we show in gut epithelial cells, galectin-9 is enriched in lysosomes and predominantly binds to lysosome-associated membrane protein 2 (Lamp2) in a Asn(N)-glycan dependent manner. At the steady state, galectin-9 binding to glycosylated Asn175 of Lamp2 is essential for functionality of lysosomes and autophagy. Loss of N-glycan-binding capability of galectin-9 causes its complete depletion from lysosomes and defective autophagy, leading to increased endoplasmic reticulum (ER) stress preferentially in autophagy-active Paneth cells and acinar cells. Unresolved ER stress consequently causes cell degeneration or apoptosis that associates with colitis and pancreatic disorders in mice. Therefore, lysosomal galectins maintain homeostatic function of lysosomes to prevent organ pathogenesis.
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Affiliation(s)
| | - Hsueh-Han Lu
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Hung-Yu Chiang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Ching-Shu Suen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Ming-Jing Hwang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Sung-Yu Wu
- Genomics Research Center, Academia Sinica, Taipei, Taiwan
| | - Chia-Ning Shen
- Genomics Research Center, Academia Sinica, Taipei, Taiwan
| | - Yao-Ming Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Fu-An Li
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Fu-Tong Liu
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Jr-Wen Shui
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
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4
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Boström AE, Chatzittofis A, Ciuculete DM, Flanagan JN, Krattinger R, Bandstein M, Mwinyi J, Kullak-Ublick GA, Öberg KG, Arver S, Schiöth HB, Jokinen J. Hypermethylation-associated downregulation of microRNA-4456 in hypersexual disorder with putative influence on oxytocin signalling: A DNA methylation analysis of miRNA genes. Epigenetics 2019; 15:145-160. [PMID: 31542994 PMCID: PMC6961682 DOI: 10.1080/15592294.2019.1656157] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Hypersexual disorder (HD) was proposed as a diagnosis in the DSM-5 and the classification ‘Compulsive Sexual Behavior Disorder’ is now presented as an impulse-control disorder in ICD-11. HD incorporates several pathophysiological mechanisms; including impulsivity, compulsivity, sexual desire dysregulation and sexual addiction. No previous study investigated HD in a methylation analysis limited to microRNA (miRNA) associated CpG-sites. The genome wide methylation pattern was measured in whole blood from 60 subjects with HD and 33 healthy volunteers using the Illumina EPIC BeadChip. 8,852 miRNA associated CpG-sites were investigated in multiple linear regression analyses of methylation M-values to a binary independent variable of disease state (HD or healthy volunteer), adjusting for optimally determined covariates. Expression levels of candidate miRNAs were investigated in the same individuals for differential expression analysis. Candidate methylation loci were further studied for an association with alcohol dependence in an independent cohort of 107 subjects. Two CpG-sites were borderline significant in HD – cg18222192 (MIR708)(p < 10E-05,pFDR = 5.81E-02) and cg01299774 (MIR4456)(p < 10E-06, pFDR = 5.81E-02). MIR4456 was significantly lower expressed in HD in both univariate (p < 0.0001) and multivariate (p < 0.05) analyses. Cg01299774 methylation levels were inversely correlated with expression levels of MIR4456 (p < 0.01) and were also differentially methylated in alcohol dependence (p = 0.026). Gene target prediction and pathway analysis revealed that MIR4456 putatively targets genes preferentially expressed in brain and that are involved in major neuronal molecular mechanisms thought to be relevant for HD, e.g., the oxytocin signalling pathway. In summary, our study implicates a potential contribution of MIR4456 in the pathophysiology of HD by putatively influencing oxytocin signalling.
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Affiliation(s)
- Adrian E Boström
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | | | - Diana-Maria Ciuculete
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - John N Flanagan
- Andrology/Sexual Medicine Group (ANOVA), Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Regina Krattinger
- Department of Clinical Pharmacology and Toxicology, University Hospital Zurich, University of Zurich, Zürich, Switzerland
| | - Marcus Bandstein
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Jessica Mwinyi
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Gerd A Kullak-Ublick
- Department of Clinical Pharmacology and Toxicology, University Hospital Zurich, University of Zurich, Zürich, Switzerland
| | - Katarina Görts Öberg
- Andrology/Sexual Medicine Group (ANOVA), Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Stefan Arver
- Andrology/Sexual Medicine Group (ANOVA), Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Helgi B Schiöth
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden.,Institute for Translational Medicine and Biotechnology, Sechenov First Moscow State Medical University, Moscow, Russia
| | - Jussi Jokinen
- Department of Clinical Sciences/Psychiatry, Umeå University, Umeå, Sweden.,Department of Clinical Neuroscience/Psychiatry, Karolinska Institutet, Stockholm, Sweden
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5
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Pandolfi EC, Hoffmann HM, Schoeller EL, Gorman MR, Mellon PL. Haploinsufficiency of SIX3 Abolishes Male Reproductive Behavior Through Disrupted Olfactory Development, and Impairs Female Fertility Through Disrupted GnRH Neuron Migration. Mol Neurobiol 2018; 55:8709-8727. [PMID: 29589282 PMCID: PMC6156938 DOI: 10.1007/s12035-018-1013-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 03/16/2018] [Indexed: 12/17/2022]
Abstract
Mating behavior in males and females is dependent on olfactory cues processed through both the main olfactory epithelium (MOE) and the vomeronasal organ (VNO). Signaling through the MOE is critical for the initiation of male mating behavior, and the loss of MOE signaling severely compromises this comportment. Here, we demonstrate that dosage of the homeodomain gene Six3 affects the degree of development of MOE but not the VNO. Anomalous MOE development in Six3 heterozygote mice leads to hyposmia, specifically disrupting male mounting behavior by impairing detection of volatile female estrus pheromones. Six3 is highly expressed in the MOE, main olfactory bulb (MOB), and hypothalamus; all regions essential in the proper migration of the gonadotropin-releasing hormone (GnRH) neurons, a key reproductive neuronal population that migrates along olfactory axons from the developing nose into the brain. Interestingly, we find that the reduction in Six3 expression in Six3 heterozygote mice compromises development of the MOE and MOB, resulting in mis-migration of GnRH neurons due to improper olfactory axon targeting. This reduction in the hypothalamic GnRH neuron population, by 45% in adulthood, leads to female subfertility, but does not impact male hormone levels, suggesting that male infertility is not related to GnRH neuron numbers, but exclusively linked to abnormal olfaction. We here determine that Six3 is haploinsufficient for MOE development, GnRH neuron migration, and fertility, and represents a novel candidate gene for Kallmann syndrome, a form of inherited infertility.
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Affiliation(s)
- Erica C Pandolfi
- Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0674, USA
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Hanne M Hoffmann
- Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0674, USA
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Erica L Schoeller
- Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0674, USA
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Michael R Gorman
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, 92093, USA
- Department of Psychology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Pamela L Mellon
- Department of Reproductive Medicine, Center for Reproductive Science and Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0674, USA.
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, 92093, USA.
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Timbers TA, Garland SJ, Mohan S, Flibotte S, Edgley M, Muncaster Q, Au V, Li-Leger E, Rosell FI, Cai J, Rademakers S, Jansen G, Moerman DG, Leroux MR. Accelerating Gene Discovery by Phenotyping Whole-Genome Sequenced Multi-mutation Strains and Using the Sequence Kernel Association Test (SKAT). PLoS Genet 2016; 12:e1006235. [PMID: 27508411 PMCID: PMC4980031 DOI: 10.1371/journal.pgen.1006235] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 07/11/2016] [Indexed: 11/25/2022] Open
Abstract
Forward genetic screens represent powerful, unbiased approaches to uncover novel components in any biological process. Such screens suffer from a major bottleneck, however, namely the cloning of corresponding genes causing the phenotypic variation. Reverse genetic screens have been employed as a way to circumvent this issue, but can often be limited in scope. Here we demonstrate an innovative approach to gene discovery. Using C. elegans as a model system, we used a whole-genome sequenced multi-mutation library, from the Million Mutation Project, together with the Sequence Kernel Association Test (SKAT), to rapidly screen for and identify genes associated with a phenotype of interest, namely defects in dye-filling of ciliated sensory neurons. Such anomalies in dye-filling are often associated with the disruption of cilia, organelles which in humans are implicated in sensory physiology (including vision, smell and hearing), development and disease. Beyond identifying several well characterised dye-filling genes, our approach uncovered three genes not previously linked to ciliated sensory neuron development or function. From these putative novel dye-filling genes, we confirmed the involvement of BGNT-1.1 in ciliated sensory neuron function and morphogenesis. BGNT-1.1 functions at the trans-Golgi network of sheath cells (glia) to influence dye-filling and cilium length, in a cell non-autonomous manner. Notably, BGNT-1.1 is the orthologue of human B3GNT1/B4GAT1, a glycosyltransferase associated with Walker-Warburg syndrome (WWS). WWS is a multigenic disorder characterised by muscular dystrophy as well as brain and eye anomalies. Together, our work unveils an effective and innovative approach to gene discovery, and provides the first evidence that B3GNT1-associated Walker-Warburg syndrome may be considered a ciliopathy. Model organisms are useful tools for uncovering new genes involved in a biological process via genetic screens. Such an approach is powerful, but suffers from drawbacks that can slow down gene discovery. In forward genetics screens, difficult-to-map phenotypes present daunting challenges, and whole-genome coverage can be equally challenging for reverse genetic screens where typically only a single gene’s function is assayed per strain. Here, we show a different approach which includes positive aspects of forward (high-coverage, randomly-induced mutations) and reverse genetics (prior knowledge of gene disruption) to accelerate gene discovery. We paired a whole-genome sequenced multi-mutation C. elegans library with a rare-variant associated test to rapidly identify genes associated with a phenotype of interest: defects in sensory neurons bearing sensory organelles called cilia, via a simple dye-filling assay to probe the form and function of these cells. We found two well characterised dye-filling genes and three genes, not previously linked to ciliated sensory neuron development or function, that were associated with dye-filling defects. We reveal that disruption of one of these (BGNT-1.1), whose human orthologue is associated with Walker-Warburg syndrome, results in abrogated uptake of dye and cilia length defects. We believe that our novel approach is useful for any organism with a small genome that can be quickly sequenced and where many mutant strains can be easily isolated and phenotyped, such as Drosophila and Arabidopsis.
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Affiliation(s)
- Tiffany A. Timbers
- Department of Molecular Biology and Biochemistry and Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Stephanie J. Garland
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Swetha Mohan
- Department of Molecular Biology and Biochemistry and Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Stephane Flibotte
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mark Edgley
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Quintin Muncaster
- Department of Molecular Biology and Biochemistry and Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Vinci Au
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Erica Li-Leger
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Federico I. Rosell
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jerry Cai
- Department of Molecular Biology and Biochemistry and Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada
| | | | - Gert Jansen
- Department of Cell Biology, Erasmus MC, Rotterdam, The Netherlands
| | - Donald G. Moerman
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michel R. Leroux
- Department of Molecular Biology and Biochemistry and Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada
- * E-mail:
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7
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Praissman JL, Live DH, Wang S, Ramiah A, Chinoy ZS, Boons GJ, Moremen KW, Wells L. B4GAT1 is the priming enzyme for the LARGE-dependent functional glycosylation of α-dystroglycan. eLife 2014; 3:e03943. [PMID: 25279697 PMCID: PMC4227051 DOI: 10.7554/elife.03943] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 10/01/2014] [Indexed: 12/16/2022] Open
Abstract
Recent studies demonstrated that mutations in B3GNT1, an enzyme proposed to be involved in poly-N-acetyllactosamine synthesis, were causal for congenital muscular dystrophy with hypoglycosylation of α-dystroglycan (secondary dystroglycanopathies). Since defects in the O-mannosylation protein glycosylation pathway are primarily responsible for dystroglycanopathies and with no established O-mannose initiated structures containing a β3 linked GlcNAc known, we biochemically interrogated this human enzyme. Here we report this enzyme is not a β-1,3-N-acetylglucosaminyltransferase with catalytic activity towards β-galactose but rather a β-1,4-glucuronyltransferase, designated B4GAT1, towards both α- and β-anomers of xylose. The dual-activity LARGE enzyme is capable of extending products of B4GAT1 and we provide experimental evidence that B4GAT1 is the priming enzyme for LARGE. Our results further define the functional O-mannosylated glycan structure and indicate that B4GAT1 is involved in the initiation of the LARGE-dependent repeating disaccharide that is necessary for extracellular matrix protein binding to O-mannosylated α-dystroglycan that is lacking in secondary dystroglycanopathies.
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Affiliation(s)
- Jeremy L Praissman
- Complex Carbohydrate Research Center, University of Georgia, Athens, United States
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, United States
| | - David H Live
- Complex Carbohydrate Research Center, University of Georgia, Athens, United States
| | - Shuo Wang
- Complex Carbohydrate Research Center, University of Georgia, Athens, United States
| | - Annapoorani Ramiah
- Complex Carbohydrate Research Center, University of Georgia, Athens, United States
| | - Zoeisha S Chinoy
- Complex Carbohydrate Research Center, University of Georgia, Athens, United States
| | - Geert-Jan Boons
- Complex Carbohydrate Research Center, University of Georgia, Athens, United States
| | - Kelley W Moremen
- Complex Carbohydrate Research Center, University of Georgia, Athens, United States
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, United States
| | - Lance Wells
- Complex Carbohydrate Research Center, University of Georgia, Athens, United States
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, United States
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8
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Nam Y, Shin EJ, Yang BK, Bach JH, Jeong JH, Chung YH, Park ES, Li Z, Kim KW, Kwon YB, Nabeshima T, Kim HC. Dextromethorphan-induced psychotoxic behaviors cause sexual dysfunction in male mice via stimulation of σ-1 receptors. Neurochem Int 2012; 61:913-22. [PMID: 22326744 DOI: 10.1016/j.neuint.2012.01.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 01/15/2012] [Accepted: 01/23/2012] [Indexed: 11/15/2022]
Abstract
Dextromethorphan (DM) is a well-known antitussive dextrorotatory morphinan. We and others have demonstrated that sigma (σ) receptors may be important for DM-mediated neuromodulation. Because an earlier report suggested that DM might affect sexual function and that σ receptor ligands affect signaling pathways in the periphery, we examined whether DM-induced psychotoxic burden affected male reproductive function. We observed that DM had a high affinity at σ-1 receptors in the brain and testis but relatively low affinity at σ-2 receptors. Prolonged treatment with DM resulted in conditioned place preference and hyperlocomotion, followed by an increase in Fos-related antigen expression in the nucleus accumbens in male mice. Simultaneously, DM induced significant reductions in gonadotropin-releasing-hormone immunoreactivity in the hypothalamus. Moreover, we observed that DM induced increased sperm abnormalities and decreased sperm viability and sexual behavior. These phenomena were significantly attenuated by combined treatment with BD1047, a σ-1 receptor antagonist, but not by SM-21, a σ-2 receptor antagonist. Thus, these results suggest that DM psychotoxicity might lead to reproductive stress in male mice by activating σ-1 receptors.
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Affiliation(s)
- Yunsung Nam
- Department of Pharmacology, College of Medicine, Chung-Ang University, Seoul 156-756, Republic of Korea
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9
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β3GnT2 null mice exhibit defective accessory olfactory bulb innervation. Mol Cell Neurosci 2012; 52:73-86. [PMID: 23006775 DOI: 10.1016/j.mcn.2012.09.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 08/14/2012] [Accepted: 09/14/2012] [Indexed: 01/19/2023] Open
Abstract
Vomeronasal sensory neurons (VSNs) extend axons to the accessory olfactory bulb (AOB) where they form synaptic connections that relay pheromone signals to the brain. The projections of apical and basal VSNs segregate in the AOB into anterior (aAOB) and posterior (pAOB) compartments. Although some aspects of this organization exhibit fundamental similarities with the main olfactory system, the mechanisms that regulate mammalian vomeronasal targeting are not as well understood. In the olfactory epithelium (OE), the glycosyltransferase β3GnT2 maintains expression of axon guidance cues required for proper glomerular positioning and neuronal survival. We show here that β3GnT2 also regulates guidance and adhesion molecule expression in the vomeronasal system in ways that are partially distinct from the OE. In wildtype mice, ephrinA5(+) axons project to stereotypic subdomains in both the aAOB and pAOB compartments. This pattern is dramatically altered in β3GnT2(-/-) mice, where ephrinA5 is upregulated exclusively on aAOB axons. Despite this, apical and basal VSN projections remain strictly segregated in the null AOB, although some V2r1b axons that normally project to the pAOB inappropriately innervate the anterior compartment. These fibers appear to arise from ectopic expression of V2r1b receptors in a subset of apical VSNs. The homotypic adhesion molecules Kirrel2 and OCAM that facilitate axon segregation and glomerular compartmentalization in the main olfactory bulb are ablated in the β3GnT2(-/-) aAOB. This loss is accompanied by a two-fold increase in the total number of V2r1b glomeruli and a failure to form morphologically distinct glomeruli in the anterior compartment. These results identify a novel function for β3GnT2 glycosylation in maintaining expression of layer-specific vomeronasal receptors, as well as adhesion molecules required for proper AOB glomerular formation.
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10
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β3GnT2 maintains adenylyl cyclase-3 signaling and axon guidance molecule expression in the olfactory epithelium. J Neurosci 2011; 31:6576-86. [PMID: 21525298 DOI: 10.1523/jneurosci.0224-11.2011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
In the olfactory epithelium (OE), odorant receptor stimulation generates cAMP signals that function in both odor detection and the regulation of axon guidance molecule expression. The enzyme that synthesizes cAMP, adenylyl cyclase 3 (AC3), is coexpressed in olfactory sensory neurons (OSNs) with poly-N-acetyllactosamine (PLN) oligosaccharides determined by the glycosyltransferase β3GnT2. The loss of either enzyme results in similar defects in olfactory bulb (OB) innervation and OSN survival, suggesting that glycosylation may be important for AC3 function. We show here that AC3 is extensively modified with N-linked PLN, which is essential for AC3 activity and localization. On Western blots, AC3 from the wild-type OE migrates diffusely as a heavily glycosylated 200 kDa band that interacts with the PLN-binding lectin LEA. AC3 from the β3GnT2(-/-) OE loses these PLN modifications, migrating instead as a 140 kDa glycoprotein. Furthermore, basal and forskolin-stimulated cAMP production is reduced 80-90% in the β3GnT2(-/-) OE. Although AC3 traffics normally to null OSN cilia, it is absent from axon projections that aberrantly target the OB. The cAMP-dependent guidance receptor neuropilin-1 is also lost from β3GnT2(-/-) OSNs and axons, while semaphorin-3A ligand expression is upregulated. In addition, kirrel2, a mosaically expressed adhesion molecule that functions in axon sorting, is absent from β3GnT2(-/-) OB projections. These results demonstrate that PLN glycans are essential in OSNs for proper AC3 localization and function. We propose that the loss of cAMP-dependent guidance cues is also a critical factor in the severe axon guidance defects observed in β3GnT2(-/-) mice.
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