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Li H, Aboudhiaf S, Parrot S, Scote-Blachon C, Benetollo C, Lin JS, Seugnet L. Pallidin function in Drosophila surface glia regulates sleep and is dependent on amino acid availability. Cell Rep 2023; 42:113025. [PMID: 37682712 DOI: 10.1016/j.celrep.2023.113025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 06/16/2023] [Accepted: 08/09/2023] [Indexed: 09/10/2023] Open
Abstract
The Pallidin protein is a central subunit of a multimeric complex called biogenesis of lysosome-related organelles complex 1 (BLOC1) that regulates specific endosomal functions and has been linked to schizophrenia. We show here that downregulation of Pallidin and other members of BLOC1 in the surface glia, the Drosophila equivalent of the blood-brain barrier, reduces and delays nighttime sleep in a circadian-clock-dependent manner. In agreement with BLOC1 involvement in amino acid transport, downregulation of the large neutral amino acid transporter 1 (LAT1)-like transporters JhI-21 and mnd, as well as of TOR (target of rapamycin) amino acid signaling, phenocopy Pallidin knockdown. Furthermore, supplementing food with leucine normalizes the sleep/wake phenotypes of Pallidin downregulation, and we identify a role for Pallidin in the subcellular trafficking of JhI-21. Finally, we provide evidence that Pallidin in surface glia is required for GABAergic neuronal activity. These data identify a BLOC1 function linking essential amino acid availability and GABAergic sleep/wake regulation.
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Affiliation(s)
- Hui Li
- Centre de Recherche en Neurosciences de Lyon, Team WAKING, Université Claude Bernard Lyon 1, INSERM U1028, CNRS UMR 5292, 69675 Bron, France
| | - Sami Aboudhiaf
- Centre de Recherche en Neurosciences de Lyon, Team WAKING, Université Claude Bernard Lyon 1, INSERM U1028, CNRS UMR 5292, 69675 Bron, France
| | - Sandrine Parrot
- Centre de Recherche en Neurosciences de Lyon, NeuroDialyTics Facility, Université Claude Bernard Lyon 1, INSERM U1028, CNRS UMR 5292, 69675 Bron, France
| | - Céline Scote-Blachon
- Centre de Recherche en Neurosciences de Lyon, GenCyTi Facility, Université Claude Bernard Lyon 1, INSERM U1028, CNRS UMR 5292, 69675 Bron, France
| | - Claire Benetollo
- Centre de Recherche en Neurosciences de Lyon, GenCyTi Facility, Université Claude Bernard Lyon 1, INSERM U1028, CNRS UMR 5292, 69675 Bron, France
| | - Jian-Sheng Lin
- Centre de Recherche en Neurosciences de Lyon, Team WAKING, Université Claude Bernard Lyon 1, INSERM U1028, CNRS UMR 5292, 69675 Bron, France
| | - Laurent Seugnet
- Centre de Recherche en Neurosciences de Lyon, Team WAKING, Université Claude Bernard Lyon 1, INSERM U1028, CNRS UMR 5292, 69675 Bron, France.
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2
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Hartwig C, Monis WJ, Chen X, Dickman DK, Pazour GJ, Faundez V. Neurodevelopmental disease mechanisms, primary cilia, and endosomes converge on the BLOC-1 and BORC complexes. Dev Neurobiol 2017; 78:311-330. [PMID: 28986965 DOI: 10.1002/dneu.22542] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 09/08/2017] [Accepted: 09/15/2017] [Indexed: 12/12/2022]
Abstract
The biogenesis of lysosome-related organelles complex-1 (BLOC-1) and the bloc-one-related complex (BORC) are the cytosolic protein complexes required for specialized membrane protein traffic along the endocytic route and the spatial distribution of endosome-derived compartments, respectively. BLOC-1 and BORC complex subunits and components of their interactomes have been associated with the risk and/or pathomechanisms of neurodevelopmental disorders. Thus, cellular processes requiring BLOC-1 and BORC interactomes have the potential to offer novel insight into mechanisms underlying behavioral defects. We focus on interactions between BLOC-1 or BORC subunits with the actin and microtubule cytoskeleton, membrane tethers, and SNAREs. These interactions highlight requirements for BLOC-1 and BORC in membrane movement by motors, control of actin polymerization, and targeting of membrane proteins to specialized cellular domains such as the nerve terminal and the primary cilium. We propose that the endosome-primary cilia pathway is an underappreciated hub in the genesis and mechanisms of neurodevelopmental disorders. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 311-330, 2018.
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Affiliation(s)
- Cortnie Hartwig
- Department of Cell Biology, Emory University, Atlanta, Georgia, 30322
| | - William J Monis
- Program in Molecular Medicine, University of Massachusetts Medical School, Biotech II, Worcester, Massachusetts, 01605
| | - Xun Chen
- Department of Biology, Neurobiology Section, University of Southern California, Los Angeles, California, 90089
| | - Dion K Dickman
- Department of Biology, Neurobiology Section, University of Southern California, Los Angeles, California, 90089
| | - Gregory J Pazour
- Program in Molecular Medicine, University of Massachusetts Medical School, Biotech II, Worcester, Massachusetts, 01605
| | - Victor Faundez
- Department of Cell Biology, Emory University, Atlanta, Georgia, 30322
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3
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Larimore J, Ryder PV, Kim KY, Ambrose LA, Chapleau C, Calfa G, Gross C, Bassell GJ, Pozzo-Miller L, Smith Y, Talbot K, Park IH, Faundez V. MeCP2 regulates the synaptic expression of a Dysbindin-BLOC-1 network component in mouse brain and human induced pluripotent stem cell-derived neurons. PLoS One 2013; 8:e65069. [PMID: 23750231 PMCID: PMC3672180 DOI: 10.1371/journal.pone.0065069] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 04/22/2013] [Indexed: 02/06/2023] Open
Abstract
Clinical, epidemiological, and genetic evidence suggest overlapping pathogenic mechanisms between autism spectrum disorder (ASD) and schizophrenia. We tested this hypothesis by asking if mutations in the ASD gene MECP2 which cause Rett syndrome affect the expression of genes encoding the schizophrenia risk factor dysbindin, a subunit of the biogenesis of lysosome-related organelles complex-1 (BLOC-1), and associated interacting proteins. We measured mRNA and protein levels of key components of a dysbindin interaction network by, quantitative real time PCR and quantitative immunohistochemistry in hippocampal samples of wild-type and Mecp2 mutant mice. In addition, we confirmed results by performing immunohistochemistry of normal human hippocampus and quantitative qRT-PCR of human inducible pluripotent stem cells (iPSCs)-derived human neurons from Rett syndrome patients. We defined the distribution of the BLOC-1 subunit pallidin in human and mouse hippocampus and contrasted this distribution with that of symptomatic Mecp2 mutant mice. Neurons from mutant mice and Rett syndrome patients displayed selectively reduced levels of pallidin transcript. Pallidin immunoreactivity decreased in the hippocampus of symptomatic Mecp2 mutant mice, a feature most prominent at asymmetric synapses as determined by immunoelectron microcopy. Pallidin immunoreactivity decreased concomitantly with reduced BDNF content in the hippocampus of Mecp2 mice. Similarly, BDNF content was reduced in the hippocampus of BLOC-1 deficient mice suggesting that genetic defects in BLOC-1 are upstream of the BDNF phenotype in Mecp2 deficient mice. Our results demonstrate that the ASD-related gene Mecp2 regulates the expression of components belonging to the dysbindin interactome and these molecular differences may contribute to synaptic phenotypes that characterize Mecp2 deficiencies and ASD.
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Affiliation(s)
- Jennifer Larimore
- Department of Biology, Agnes Scott College, Decatur, Georgia, United States of America
| | - Pearl V. Ryder
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
| | - Kun-Yong Kim
- Department of Genetics, Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, United States of America
| | - L. Alex Ambrose
- Department of Biology, Agnes Scott College, Decatur, Georgia, United States of America
| | - Christopher Chapleau
- Department of Neurobiology, The University of Alabama, Birmingham, Alabama, United States of America
| | - Gaston Calfa
- Department of Neurobiology, The University of Alabama, Birmingham, Alabama, United States of America
| | - Christina Gross
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
| | - Gary J. Bassell
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
| | - Lucas Pozzo-Miller
- Department of Neurobiology, The University of Alabama, Birmingham, Alabama, United States of America
| | - Yoland Smith
- Department of Neurology, Emory University, Atlanta, Georgia, United States of America
- Yerkes National Primate Center, Emory University, Atlanta, Georgia, United States of America
| | - Konrad Talbot
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - In-Hyun Park
- Department of Genetics, Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, United States of America
| | - Victor Faundez
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
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4
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John Peter AT, Lachmann J, Rana M, Bunge M, Cabrera M, Ungermann C. The BLOC-1 complex promotes endosomal maturation by recruiting the Rab5 GTPase-activating protein Msb3. ACTA ACUST UNITED AC 2013; 201:97-111. [PMID: 23547030 PMCID: PMC3613695 DOI: 10.1083/jcb.201210038] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Yeast BLOC-1 acts as both a Rab5–Vps21 effector and an adapter for the Rab-GAP Msb3 to promote endosomal maturation. Membrane microcompartments of the early endosomes serve as a sorting and signaling platform, where receptors are either recycled back to the plasma membrane or forwarded to the lysosome for destruction. In metazoan cells, three complexes, termed BLOC-1 to -3, mediate protein sorting from the early endosome to lysosomes and lysosome-related organelles. We now demonstrate that BLOC-1 is an endosomal Rab-GAP (GTPase-activating protein) adapter complex in yeast. The yeast BLOC-1 consisted of six subunits, which localized interdependently to the endosomes in a Rab5/Vps21-dependent manner. In the absence of BLOC-1 subunits, the balance between recycling and degradation of selected cargoes was impaired. Additionally, our data show that BLOC-1 is both a Vps21 effector and an adapter for its GAP Msb3. BLOC-1 and Msb3 interacted in vivo, and both mutants resulted in a redistribution of active Vps21 to the vacuole surface. We thus conclude that BLOC-1 controls the lifetime of active Rab5/Vps21 and thus endosomal maturation along the endocytic pathway.
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Affiliation(s)
- Arun T John Peter
- Department of Biology/Chemistry, Biochemistry Section, University of Osnabrück, 49076 Osnabrück, Germany
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5
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Sitaram A, Marks MS. Mechanisms of protein delivery to melanosomes in pigment cells. Physiology (Bethesda) 2012; 27:85-99. [PMID: 22505665 DOI: 10.1152/physiol.00043.2011] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vertebrate pigment cells in the eye and skin are useful models for cell types that use specialized endosomal trafficking pathways to partition cargo proteins to unique lysosome-related organelles such as melanosomes. This review describes current models of protein trafficking required for melanosome biogenesis in mammalian melanocytes.
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Affiliation(s)
- Anand Sitaram
- Cell and Molecular Biology Graduate Group, Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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6
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Modeling disease mutations by gene targeting in one-cell mouse embryos. Proc Natl Acad Sci U S A 2012; 109:9354-9. [PMID: 22660928 DOI: 10.1073/pnas.1121203109] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Gene targeting by zinc-finger nucleases in one-cell embryos provides an expedite mutagenesis approach in mice, rats, and rabbits. This technology has been recently used to create knockout and knockin mutants through the deletion or insertion of nucleotides. Here we apply zinc-finger nucleases in one-cell mouse embryos to generate disease-related mutants harboring single nucleotide or codon replacements. Using a gene-targeting vector or a synthetic oligodesoxynucleotide as template for homologous recombination, we introduced missense and silent mutations into the Rab38 gene, encoding a small GTPase that regulates intracellular vesicle trafficking. These results demonstrate the feasibility of seamless gene editing in one-cell embryos to create genetic disease models and establish synthetic oligodesoxynucleotides as a simplified mutagenesis tool.
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7
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Yang Q, He X, Yang L, Zhou Z, Cullinane AR, Wei A, Zhang Z, Hao Z, Zhang A, He M, Feng Y, Gao X, Gahl WA, Huizing M, Li W. The BLOS1-interacting protein KXD1 is involved in the biogenesis of lysosome-related organelles. Traffic 2012; 13:1160-9. [PMID: 22554196 DOI: 10.1111/j.1600-0854.2012.01375.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 04/30/2012] [Accepted: 05/03/2012] [Indexed: 12/24/2022]
Abstract
Biogenesis of lysosome-related organelles (LROs) complex-1 (BLOC-1) is an eight-subunit complex involved in lysosomal trafficking. Interacting proteins of these subunits expand the understanding of its biological functions. With the implementation of the naïve Bayesian analysis, we found that a human uncharacterized 20 kDa coiled-coil KxDL protein, KXD1, is a BLOS1-interacting protein. In vitro binding assays confirmed the interaction between BLOS1 and KXD1. The mouse KXD1 homolog was widely expressed and absent in Kxd1 knockout (KO) mice. BLOS1 was apparently reduced in Kxd1-KO mice. Mild defects in the melanosomes of the retinal pigment epithelia and in the platelet dense granules of the Kxd1-KO mouse were observed, mimicking a mouse model of mild Hermansky-Pudlak syndrome that affects the biogenesis of LROs.
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Affiliation(s)
- Qing Yang
- State Key Laboratory of Molecular and Developmental Biology, Institute of Genetics & Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
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8
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Lee HH, Nemecek D, Schindler C, Smith WJ, Ghirlando R, Steven AC, Bonifacino JS, Hurley JH. Assembly and architecture of biogenesis of lysosome-related organelles complex-1 (BLOC-1). J Biol Chem 2011; 287:5882-90. [PMID: 22203680 DOI: 10.1074/jbc.m111.325746] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BLOC-1 (biogenesis of lysosome-related organelles complex-1) is critical for melanosome biogenesis and has also been implicated in neurological function and disease. We show that BLOC-1 is an elongated complex that contains one copy each of the eight subunits pallidin, Cappuccino, dysbindin, Snapin, Muted, BLOS1, BLOS2, and BLOS3. The complex appears as a linear chain of eight globular domains, ∼300 Å long and ∼30 Å in diameter. The individual domains are flexibly connected such that the linear chain undergoes bending by as much as 45°. Two stable subcomplexes were defined, pallidin-Cappuccino-BLOS1 and dysbindin-Snapin-BLOS2. Both subcomplexes are 1:1:1 heterotrimers that form extended structures as indicated by their hydrodynamic properties. The two subcomplexes appear to constitute flexible units within the larger BLOC-1 chain, an arrangement conducive to simultaneous interactions with multiple BLOC-1 partners in the course of tubular endosome biogenesis and sorting.
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Affiliation(s)
- Hyung Ho Lee
- Department of Bio and Nano Chemistry, Kookmin University, Seoul 136-702, Korea
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9
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Mullin AP, Gokhale A, Larimore J, Faundez V. Cell biology of the BLOC-1 complex subunit dysbindin, a schizophrenia susceptibility gene. Mol Neurobiol 2011; 44:53-64. [PMID: 21520000 PMCID: PMC3321231 DOI: 10.1007/s12035-011-8183-3] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Accepted: 04/12/2011] [Indexed: 11/28/2022]
Abstract
There is growing interest in the biology of dysbindin and its genetic locus (DTNBP1) due to genetic variants associated with an increased risk of schizophrenia. Reduced levels of dysbindin mRNA and protein in the hippocampal formation of schizophrenia patients further support involvement of this locus in disease risk. Here, we discuss phylogenetically conserved dysbindin molecular interactions that define its contribution to the assembly of the biogenesis of lysosome-related organelles complex-1 (BLOC-1). We explore fundamental cellular processes where dysbindin and the dysbindin-containing BLOC-1 complex are implicated. We propose that cellular, tissue, and system neurological phenotypes from dysbindin deficiencies in model genetic organisms, and likely individuals affected with schizophrenia, emerge from abnormalities in few core cellular mechanisms controlled by BLOC-1-dysbindin-containing complex rather than from defects in dysbindin itself.
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Affiliation(s)
- Ariana P Mullin
- Graduate Program in Neuroscience, Emory University, Atlanta, GA, USA
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10
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Hayes MJ, Bryon K, Satkurunathan J, Levine TP. Yeast homologues of three BLOC-1 subunits highlight KxDL proteins as conserved interactors of BLOC-1. Traffic 2011; 12:260-8. [PMID: 21159114 DOI: 10.1111/j.1600-0854.2010.01151.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Biogenesis of lysosome-related organelle complex-1 (BLOC-1) is one of the four multi-subunit complexes implicated in sorting cargo to lysosome-related organelles, as loss of function of any of these complexes causes Hermansky-Pudlak syndrome. Eight subunits of BLOC-1 interact with each other and with many other proteins. Identifying new interactors of BLOC-1 will increase understanding of its mechanism of action, and studies in model organisms are useful for finding such interactors. PSI-BLAST searches identify homologues in diverse model organisms, but there are significant gaps for BLOC-1, with none of its eight subunits found in Saccharomyces cerevisiae. Here we use more sensitive searches to identify distant homologues for three BLOC-1 subunits in S. cerevisiae: Blos1, snapin and cappuccino (cno). Published data on protein interactions show that in yeast these are likely to form a complex with three other proteins. One of these is the yeast homologue of the previously uncharacterized KxDL protein, which also interacts with Blos1 and cno in higher eukaryotes, suggesting that KxDL proteins are key interactors with BLOC-1.
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Affiliation(s)
- Matthew J Hayes
- Department of Cell Biology, UCL Institute of Ophthalmology, Bath Street, London EC1V9EL, UK
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11
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Ghiani CA, Dell'Angelica EC. Dysbindin-containing complexes and their proposed functions in brain: from zero to (too) many in a decade. ASN Neuro 2011; 3:e00058. [PMID: 21504412 PMCID: PMC3155195 DOI: 10.1042/an20110010] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 04/18/2011] [Accepted: 04/20/2011] [Indexed: 02/07/2023] Open
Abstract
Dysbindin (also known as dysbindin-1 or dystrobrevin-binding protein 1) was identified 10 years ago as a ubiquitously expressed protein of unknown function. In the following years, the protein and its encoding gene, DTNBP1, have become the focus of intensive research owing to genetic and histopathological evidence suggesting a potential role in the pathogenesis of schizophrenia. In this review, we discuss published results demonstrating that dysbindin function is required for normal physiology of the mammalian central nervous system. In tissues other than brain and in non-neuronal cell types, the protein has been characterized as a stable component of a multi-subunit complex, named BLOC-1 (biogenesis of lysosome-related organelles complex-1), which has been implicated in intracellular protein trafficking and the biogenesis of specialized organelles of the endosomal-lysosomal system. In the brain, however, dysbindin has been proposed to associate into multiple complexes with alternative binding partners, and to play a surprisingly wide variety of functions including transcriptional regulation, neurite and dendritic spine formation, synaptic vesicle biogenesis and exocytosis, and trafficking of glutamate and dopamine receptors. This puzzling array of molecular and functional properties ascribed to the dysbindin protein from brain underscores the need of further research aimed at ascertaining its biological significance in health and disease.
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Key Words
- biogenesis of lysosome-related organelles complex-1 (bloc-1)
- dtnbp1
- dysbindin
- dystrobrevin-binding protein
- schizophrenia
- ap-3, adaptor protein-3
- bloc, biogenesis of lysosome-related organelles complex
- coip, co-immunoprecipitation
- hek-293 cells, human embryonic kidney cells
- hps, hermansky–pudlak syndrome
- jnk, c-jun n-terminal kinase
- ms/ms, tandem mass spectrometry
- rnai, rna interference
- shrna, short-hairpin rna
- sirna, small-interfering rna
- wash, wiskott–aldrich syndrome protein and scar homologue
- vamp-7, vesicle-associated membrane protein 7
- wave, wasp (wiskott–aldrich syndrome protein) verprolin homologous
- y2h, yeast two-hybrid
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Affiliation(s)
- Cristina A Ghiani
- *Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, U.S.A
- †Department of Psychiatry, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, U.S.A
| | - Esteban C Dell'Angelica
- *Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, U.S.A
- ‡Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, U.S.A
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12
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Hou L, Wang JX, Zhao XF. Rab32 and the remodeling of the imaginal midgut in Helicoverpa armigera. Amino Acids 2010; 40:953-61. [DOI: 10.1007/s00726-010-0720-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Accepted: 08/04/2010] [Indexed: 12/13/2022]
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The dysbindin-containing complex (BLOC-1) in brain: developmental regulation, interaction with SNARE proteins and role in neurite outgrowth. Mol Psychiatry 2010; 15:115, 204-15. [PMID: 19546860 PMCID: PMC2811213 DOI: 10.1038/mp.2009.58] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Previous studies have implicated DTNBP1 as a schizophrenia susceptibility gene and its encoded protein, dysbindin, as a potential regulator of synaptic vesicle physiology. In this study, we found that endogenous levels of the dysbindin protein in the mouse brain are developmentally regulated, with higher levels observed during embryonic and early postnatal ages than in young adulthood. We obtained biochemical evidence indicating that the bulk of dysbindin from brain exists as a stable component of biogenesis of lysosome-related organelles complex-1 (BLOC-1), a multi-subunit protein complex involved in intracellular membrane trafficking and organelle biogenesis. Selective biochemical interaction between brain BLOC-1 and a few members of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) superfamily of proteins that control membrane fusion, including SNAP-25 and syntaxin 13, was demonstrated. Furthermore, primary hippocampal neurons deficient in BLOC-1 displayed neurite outgrowth defects. Taken together, these observations suggest a novel role for the dysbindin-containing complex, BLOC-1, in neurodevelopment, and provide a framework for considering potential effects of allelic variants in DTNBP1--or in other genes encoding BLOC-1 subunits--in the context of the developmental model of schizophrenia pathogenesis.
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14
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Cheli VT, Daniels RW, Godoy R, Hoyle DJ, Kandachar V, Starcevic M, Martinez-Agosto JA, Poole S, DiAntonio A, Lloyd VK, Chang HC, Krantz DE, Dell'Angelica EC. Genetic modifiers of abnormal organelle biogenesis in a Drosophila model of BLOC-1 deficiency. Hum Mol Genet 2009; 19:861-78. [PMID: 20015953 DOI: 10.1093/hmg/ddp555] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Biogenesis of lysosome-related organelles complex 1 (BLOC-1) is a protein complex formed by the products of eight distinct genes. Loss-of-function mutations in two of these genes, DTNBP1 and BLOC1S3, cause Hermansky-Pudlak syndrome, a human disorder characterized by defective biogenesis of lysosome-related organelles. In addition, haplotype variants within the same two genes have been postulated to increase the risk of developing schizophrenia. However, the molecular function of BLOC-1 remains unknown. Here, we have generated a fly model of BLOC-1 deficiency. Mutant flies lacking the conserved Blos1 subunit displayed eye pigmentation defects due to abnormal pigment granules, which are lysosome-related organelles, as well as abnormal glutamatergic transmission and behavior. Epistatic analyses revealed that BLOC-1 function in pigment granule biogenesis requires the activities of BLOC-2 and a putative Rab guanine-nucleotide-exchange factor named Claret. The eye pigmentation phenotype was modified by misexpression of proteins involved in intracellular protein trafficking; in particular, the phenotype was partially ameliorated by Rab11 and strongly enhanced by the clathrin-disassembly factor, Auxilin. These observations validate Drosophila melanogaster as a powerful model for the study of BLOC-1 function and its interactions with modifier genes.
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Affiliation(s)
- Verónica T Cheli
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
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15
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Hikita T, Taya S, Fujino Y, Taneichi-Kuroda S, Ohta K, Tsuboi D, Shinoda T, Kuroda K, Funahashi Y, Uraguchi-Asaki J, Hashimoto R, Kaibuchi K. Proteomic analysis reveals novel binding partners of dysbindin, a schizophrenia-related protein. J Neurochem 2009; 110:1567-74. [PMID: 19573021 DOI: 10.1111/j.1471-4159.2009.06257.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Schizophrenia is a complex mental disorder with fairly high level of heritability. Dystrobrevin binding protein 1, a gene encoding dysbindin protein, is a susceptibility gene for schizophrenia that was identified by family-based association analysis. Recent studies revealed that dysbindin is involved in the exocytosis and/or formation of synaptic vesicles. However, the molecular function of dysbindin in synaptic transmission is largely unknown. To investigate the signaling pathway in which dysbindin is involved, we isolated dysbindin-interacting molecules from rat brain lysate by combining ammonium sulfate precipitation and dysbindin-affinity column chromatography, and identified dysbindin-interacting proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and liquid chromatography-tandem mass spectrometry. Proteins involved in protein localization process, including Munc18-1, were identified as dysbindin-interacting proteins. Munc18-1 was co-immunoprecipitated with dysbindin from rat brain lysate, and directly interacted with dysbindin in vitro. In primary cultured rat hippocampal neurons, a part of dysbindin was co-localized with Munc18-1 at pre-synaptic terminals. Our result suggests a role for dysbindin in synaptic vesicle exocytosis via interaction with Munc18-1.
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Affiliation(s)
- Takao Hikita
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Nagoya, Aichi 466-8550, Japan
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