1
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Halim DO, Krishnan G, Hass EP, Lee S, Verma M, Almeida S, Gu Y, Kwon DY, Fazzio TG, Gao FB. The exocyst subunit EXOC2 regulates the toxicity of expanded GGGGCC repeats in C9ORF72-ALS/FTD. Cell Rep 2024; 43:114375. [PMID: 38935506 DOI: 10.1016/j.celrep.2024.114375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 04/26/2024] [Accepted: 05/31/2024] [Indexed: 06/29/2024] Open
Abstract
GGGGCC (G4C2) repeat expansion in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). How this genetic mutation leads to neurodegeneration remains largely unknown. Using CRISPR-Cas9 technology, we deleted EXOC2, which encodes an essential exocyst subunit, in induced pluripotent stem cells (iPSCs) derived from C9ORF72-ALS/FTD patients. These cells are viable owing to the presence of truncated EXOC2, suggesting that exocyst function is partially maintained. Several disease-relevant cellular phenotypes in C9ORF72 iPSC-derived motor neurons are rescued due to, surprisingly, the decreased levels of dipeptide repeat (DPR) proteins and expanded G4C2 repeats-containing RNA. The treatment of fully differentiated C9ORF72 neurons with EXOC2 antisense oligonucleotides also decreases expanded G4C2 repeats-containing RNA and partially rescued disease phenotypes. These results indicate that EXOC2 directly or indirectly regulates the level of G4C2 repeats-containing RNA, making it a potential therapeutic target in C9ORF72-ALS/FTD.
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Affiliation(s)
- Dilara O Halim
- Frontotemporal Dementia Research Center, RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA; Graduate Program in Neuroscience, Morningside Graduate School of Biomedical Sciences, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Gopinath Krishnan
- Frontotemporal Dementia Research Center, RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Evan P Hass
- Department of Molecular, Cell, and Cancer Biology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Soojin Lee
- Frontotemporal Dementia Research Center, RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Mamta Verma
- Frontotemporal Dementia Research Center, RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Sandra Almeida
- Department of Neurology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Yuanzheng Gu
- Neuromuscular & Muscle Disorders, Biogen, Cambridge, MA 02142, USA
| | - Deborah Y Kwon
- Neuromuscular & Muscle Disorders, Biogen, Cambridge, MA 02142, USA
| | - Thomas G Fazzio
- Department of Molecular, Cell, and Cancer Biology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Fen-Biao Gao
- Frontotemporal Dementia Research Center, RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA; Graduate Program in Neuroscience, Morningside Graduate School of Biomedical Sciences, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA; Department of Neurology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA.
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2
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Mikami N, Nguyen CLK, Osawa Y, Kato K, Ishida M, Tanimoto Y, Morimoto K, Murata K, Kang W, Sugiyama F, Ema M, Takahashi S, Mizuno S. Deletion of Exoc7, but not Exoc3, in male germ cells causes severe spermatogenesis failure with spermatocyte aggregation in mice. Exp Anim 2024; 73:286-292. [PMID: 38325858 PMCID: PMC11254494 DOI: 10.1538/expanim.23-0171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 01/31/2024] [Indexed: 02/09/2024] Open
Abstract
Vesicular trafficking is essential for the transport of intracellularly produced functional molecules to the plasma membrane and extracellular space. The exocyst complex, composed of eight different proteins, is an important functional machinery for "tethering" in vesicular trafficking. Functional studies have been conducted in laboratory mice to identify the mechanisms by which the deletion of each exocyst factor affect various biological phenomena. Interestingly, each exocyst factor-deficient mutant exhibits a different phenotype. This discrepancy may be due to the function of the exocyst factor beyond its role as a component of the exocyst complex. Male germline-specific conditional knockout (cKO) mice of the Exoc1 gene, which encodes one of the exocyst factors EXOC1 (SEC3), exhibit severe spermatogenesis defects; however, whether this abnormality also occurs in mutants lacking other exocyst factors remains unknown. In this study, we found that exocyst factor EXOC3 (SEC6) was not required for spermatogenesis, but depletion of EXOC7 (EXO70) led to severe spermatogenesis defects. In addition to being a component of the exocyst complex, EXOC1 has other functions. Notably, male germ cell-specific Exoc7 cKO and Exoc1 cKO mice exhibited phenotypic similarities, suggesting the importance of the exocyst complex for spermatogenesis. The results of this study will contribute to further understanding of spermatogenesis from the aspect of vesicular trafficking.
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Affiliation(s)
- Natsuki Mikami
- Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Chi Lieu Kim Nguyen
- Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Yuki Osawa
- Master's Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Kanako Kato
- Laboratory Animal Resource Center and Trans-Border Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Miyuki Ishida
- Laboratory Animal Resource Center and Trans-Border Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Yoko Tanimoto
- Laboratory Animal Resource Center and Trans-Border Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Kento Morimoto
- Doctoral Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
- Research Fellow of the Japan Society for the Promotion of Science, Kojimachi Business Center Building, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083, Japan
| | - Kazuya Murata
- Laboratory Animal Resource Center and Trans-Border Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Woojin Kang
- Laboratory Animal Resource Center and Trans-Border Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Fumihiro Sugiyama
- Laboratory Animal Resource Center and Trans-Border Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Masatsugu Ema
- Department of Stem Cells and Human Disease Models, Research Center for Animal Life Science, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Satoru Takahashi
- Laboratory Animal Resource Center and Trans-Border Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | - Seiya Mizuno
- Laboratory Animal Resource Center and Trans-Border Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
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3
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Takashima S, Okamura E, Ichiyama Y, Nishi K, Shimizu A, Watanabe C, Muto M, Matsumoto S, Tsukiyama-Fujii S, Tsukiyama T, Ogita H, Nishi E, Ohji M, Sugiyama F, Takahashi S, Mizuno S, Mizutani KI, Ema M. Null mutation of exocyst complex component 3-like does not affect vascular development in mice. Exp Anim 2024; 73:93-100. [PMID: 37661429 PMCID: PMC10877151 DOI: 10.1538/expanim.23-0105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Accepted: 08/27/2023] [Indexed: 09/05/2023] Open
Abstract
Exocyst is an octameric protein complex implicated in exocytosis. The exocyst complex is highly conserved among mammalian species, but the physiological function of each subunit in exocyst remains unclear. Previously, we identified exocyst complex component 3-like (Exoc3l) as a gene abundantly expressed in embryonic endothelial cells and implicated in the process of angiogenesis in human umbilical cord endothelial cells. Here, to reveal the physiological roles of Exoc3l during development, we generated Exoc3l knockout (KO) mice by genome editing with CRISPR/Cas9. Exoc3l KO mice were viable and showed no significant phenotype in embryonic angiogenesis or postnatal retinal angiogenesis. Exoc3l KO mice also showed no significant alteration in cholesterol homeostasis or insulin secretion, although several reports suggest an association of Exoc3l with these processes. Despite the implied roles, Exoc3l KO mice exhibited no apparent phenotype in vascular development, cholesterol homeostasis, or insulin secretion.
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Affiliation(s)
- Satsuki Takashima
- Department of Stem Cells and Human Disease Models, Research Center for Animal Life Science, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Eiichi Okamura
- Department of Stem Cells and Human Disease Models, Research Center for Animal Life Science, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Yusuke Ichiyama
- Department of Ophthalmology, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Kiyoto Nishi
- Department of Pharmacology, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Akio Shimizu
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Chisato Watanabe
- Department of Stem Cells and Human Disease Models, Research Center for Animal Life Science, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Masanaga Muto
- Department of Stem Cells and Human Disease Models, Research Center for Animal Life Science, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Shoma Matsumoto
- Department of Stem Cells and Human Disease Models, Research Center for Animal Life Science, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Setsuko Tsukiyama-Fujii
- Department of Stem Cells and Human Disease Models, Research Center for Animal Life Science, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Tomoyuki Tsukiyama
- Department of Stem Cells and Human Disease Models, Research Center for Animal Life Science, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Hisakazu Ogita
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Eiichiro Nishi
- Department of Pharmacology, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Masahito Ohji
- Department of Ophthalmology, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Fumihiro Sugiyama
- Laboratory Animal Resource Center in Transborder Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
| | - Satoru Takahashi
- Laboratory Animal Resource Center in Transborder Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
- Department of Anatomy and Embryology, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
- International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
| | - Seiya Mizuno
- Laboratory Animal Resource Center in Transborder Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
| | - Ken-Ichi Mizutani
- Laboratory of Stem Cell Biology, Graduate School of Pharmaceutical Sciences, Kobe Gakuin University, 1-1-3 Minatojima, Chuo-ku, Kobe, Hyogo 650-8586, Japan
| | - Masatsugu Ema
- Department of Stem Cells and Human Disease Models, Research Center for Animal Life Science, Shiga University of Medical Science, Seta, Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
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4
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Ciampelli C, Galleri G, Puggioni S, Fais M, Iannotta L, Galioto M, Becciu M, Greggio E, Bernardoni R, Crosio C, Iaccarino C. Inhibition of the Exocyst Complex Attenuates the LRRK2 Pathological Effects. Int J Mol Sci 2023; 24:12656. [PMID: 37628835 PMCID: PMC10454163 DOI: 10.3390/ijms241612656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 08/03/2023] [Accepted: 08/06/2023] [Indexed: 08/27/2023] Open
Abstract
Pathological mutations in leucine-rich repeat kinase 2 (LRRK2) gene are the major genetic cause of Parkinson's disease (PD). Multiple lines of evidence link LRRK2 to the control of vesicle dynamics through phosphorylation of a subset of RAB proteins. However, the molecular mechanisms underlying these processes are not fully elucidated. We have previously demonstrated that LRRK2 increases the exocyst complex assembly by Sec8 interaction, one of the eight members of the exocyst complex, and that Sec8 over-expression mitigates the LRRK2 pathological effect in PC12 cells. Here, we extend this analysis using LRRK2 drosophila models and show that the LRRK2-dependent exocyst complex assembly increase is downstream of RAB phosphorylation. Moreover, exocyst complex inhibition rescues mutant LRRK2 pathogenic phenotype in cellular and drosophila models. Finally, prolonged exocyst inhibition leads to a significant reduction in the LRRK2 protein level, overall supporting the role of the exocyst complex in the LRRK2 pathway. Taken together, our study suggests that modulation of the exocyst complex may represent a novel therapeutic target for PD.
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Affiliation(s)
- Cristina Ciampelli
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.C.); (G.G.); (S.P.); (M.F.); (M.G.); (M.B.); (C.C.)
| | - Grazia Galleri
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.C.); (G.G.); (S.P.); (M.F.); (M.G.); (M.B.); (C.C.)
| | - Silvia Puggioni
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.C.); (G.G.); (S.P.); (M.F.); (M.G.); (M.B.); (C.C.)
| | - Milena Fais
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.C.); (G.G.); (S.P.); (M.F.); (M.G.); (M.B.); (C.C.)
| | - Lucia Iannotta
- Department of Biology, University of Padova, 35131 Padova, Italy; (L.I.); (E.G.)
| | - Manuela Galioto
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.C.); (G.G.); (S.P.); (M.F.); (M.G.); (M.B.); (C.C.)
| | - Marta Becciu
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.C.); (G.G.); (S.P.); (M.F.); (M.G.); (M.B.); (C.C.)
| | - Elisa Greggio
- Department of Biology, University of Padova, 35131 Padova, Italy; (L.I.); (E.G.)
| | - Roberto Bernardoni
- Department of Pharmacy and Biotechnology (FABIT), University of Bologna, 40126 Bologna, Italy;
| | - Claudia Crosio
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.C.); (G.G.); (S.P.); (M.F.); (M.G.); (M.B.); (C.C.)
| | - Ciro Iaccarino
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (C.C.); (G.G.); (S.P.); (M.F.); (M.G.); (M.B.); (C.C.)
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5
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Halim DO, Munson M, Gao FB. The exocyst complex in neurological disorders. Hum Genet 2023; 142:1263-1270. [PMID: 37085629 PMCID: PMC10449956 DOI: 10.1007/s00439-023-02558-w] [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] [Received: 02/25/2023] [Accepted: 04/11/2023] [Indexed: 04/23/2023]
Abstract
Exocytosis is the process by which secretory vesicles fuse with the plasma membrane to deliver materials to the cell surface or to release cargoes to the extracellular space. The exocyst-an evolutionarily conserved octameric protein complex-mediates spatiotemporal control of SNARE complex assembly for vesicle fusion and tethering the secretory vesicles to the plasma membrane. The exocyst participates in diverse cellular functions, including protein trafficking to the plasma membrane, membrane extension, cell polarity, neurite outgrowth, ciliogenesis, cytokinesis, cell migration, autophagy, host defense, and tumorigenesis. Exocyst subunits are essential for cell viability; and mutations or variants in several exocyst subunits have been implicated in human diseases, mostly neurodevelopmental disorders and ciliopathies. These conditions often share common features such as developmental delay, intellectual disability, and brain abnormalities. In this review, we summarize the mutations and variants in exocyst subunits that have been linked to disease and discuss the implications of exocyst dysfunction in other disorders.
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Affiliation(s)
- Dilara O Halim
- Department of Neurology, University of Massachusetts Chan Medical School, Worcester, MA, USA.
- Graduate Program in Neuroscience, Morningside Graduate School of Biomedical Sciences, University of Massachusetts Chan Medical School, Worcester, MA, USA.
| | - Mary Munson
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Fen-Biao Gao
- Department of Neurology, University of Massachusetts Chan Medical School, Worcester, MA, USA
- Graduate Program in Neuroscience, Morningside Graduate School of Biomedical Sciences, University of Massachusetts Chan Medical School, Worcester, MA, USA
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6
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Soriano P. My pearl anniversary with Genes & Development,30 years on…. Genes Dev 2023; 37:50-51. [PMID: 37062004 DOI: 10.1101/gad.350403.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
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7
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Swope RD, Hertzler JI, Stone MC, Kothe GO, Rolls MM. The exocyst complex is required for developmental and regenerative neurite growth in vivo. Dev Biol 2022; 492:1-13. [PMID: 36162553 PMCID: PMC10228574 DOI: 10.1016/j.ydbio.2022.09.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 09/13/2022] [Accepted: 09/19/2022] [Indexed: 11/30/2022]
Abstract
The exocyst complex is an important regulator of intracellular trafficking and tethers secretory vesicles to the plasma membrane. Understanding of its role in neuron outgrowth remains incomplete, and previous studies have come to different conclusions about its importance for axon and dendrite growth, particularly in vivo. To investigate exocyst function in vivo we used Drosophila sensory neurons as a model system. To bypass early developmental requirements in other cell types, we used neuron-specific RNAi to target seven exocyst subunits. Initial neuronal development proceeded normally in these backgrounds, however, we considered this could be due to residual exocyst function. To probe neuronal growth capacity at later times after RNAi initiation, we used laser microsurgery to remove axons or dendrites and prompt regrowth. Exocyst subunit RNAi reduced axon regeneration, although new axons could be specified. In control neurons, a vesicle trafficking marker often concentrated in the new axon, but this pattern was disrupted in Sec6 RNAi neurons. Dendrite regeneration was also severely reduced by exocyst RNAi, even though the trafficking marker did not accumulate in a strongly polarized manner during normal dendrite regeneration. The requirement for the exocyst was not limited to injury contexts as exocyst subunit RNAi eliminated dendrite regrowth after developmental pruning. We conclude that the exocyst is required for injury-induced and developmental neurite outgrowth, but that residual protein function can easily mask this requirement.
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Affiliation(s)
- Rachel D Swope
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, University Park, PA, 16802, USA
| | - J Ian Hertzler
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, University Park, PA, 16802, USA
| | - Michelle C Stone
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, University Park, PA, 16802, USA
| | - Gregory O Kothe
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, University Park, PA, 16802, USA
| | - Melissa M Rolls
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, University Park, PA, 16802, USA.
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8
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Simsek-Kiper PO, Jacob P, Upadhyai P, Taşkıran ZE, Guleria VS, Karaosmanoglu B, Imren G, Gocmen R, Bhavani GS, Kausthubham N, Shah H, Utine GE, Boduroglu K, Girisha KM. Biallelic loss-of-function variants in EXOC6B are associated with impaired primary ciliogenesis and cause spondylo-epi-metaphyseal dysplasia with joint laxity type 3. Hum Mutat 2022; 43:2116-2129. [PMID: 36150098 PMCID: PMC7615863 DOI: 10.1002/humu.24478] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 08/30/2022] [Accepted: 09/21/2022] [Indexed: 01/25/2023]
Abstract
Spondylo-epi-metaphyseal dysplasias with joint laxity, type 3 (SEMDJL3) is a genetic skeletal disorder characterized by multiple joint dislocations, caused by biallelic pathogenic variants in the EXOC6B gene. Only four individuals from two families have been reported to have this condition to date. The molecular pathogenesis related to primary ciliogenesis has not been enumerated in subjects with SEMDJL3. In this study, we report two additional affected individuals from unrelated families with biallelic pathogenic variants, c.2122+15447_2197-59588del and c.401T>G in EXOC6B identified by exome sequencing. One of the affected individuals had an intellectual disability and central nervous system anomalies, including hydrocephalus, hypoplastic mesencephalon, and thin corpus callosum. Using the fibroblast cell lines, we demonstrate the primary evidence for the abrogation of exocytosis in an individual with SEMDLJ3 leading to impaired primary ciliogenesis. Osteogenesis differentiation and pathways related to the extracellular matrix were also found to be reduced. Additionally, we provide a review of the clinical and molecular profile of all the mutation-proven patients reported hitherto, thereby further characterizing SEMDJL3. SEMDJL3 with biallelic pathogenic variants in EXOC6B might represent yet another ciliopathy with central nervous system involvement and joint dislocations.
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Affiliation(s)
| | - Prince Jacob
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Priyanka Upadhyai
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Zihni Ekim Taşkıran
- Department of Medical Genetics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Vishal S. Guleria
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Beren Karaosmanoglu
- Department of Medical Genetics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Gozde Imren
- Department of Medical Genetics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Rahsan Gocmen
- Department of Radiology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Gandham S. Bhavani
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Neethukrishna Kausthubham
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Hitesh Shah
- Department of Pediatric Orthopaedics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Gulen Eda Utine
- Department of Pediatric Genetics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Koray Boduroglu
- Department of Pediatric Genetics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Katta M. Girisha
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
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9
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Osawa Y, Murata K, Usui M, Kuba Y, Le HT, Mikami N, Nakagawa T, Daitoku Y, Kato K, Shawki HH, Ikeda Y, Kuno A, Morimoto K, Tanimoto Y, Dinh TTH, Yagami KI, Ema M, Yoshida S, Takahashi S, Mizuno S, Sugiyama F. EXOC1 plays an integral role in spermatogonia pseudopod elongation and spermatocyte stable syncytium formation in mice. eLife 2021; 10:59759. [PMID: 33973520 PMCID: PMC8112867 DOI: 10.7554/elife.59759] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 04/21/2021] [Indexed: 11/13/2022] Open
Abstract
The male germ cells must adopt the correct morphology at each differentiation stage for proper spermatogenesis. The spermatogonia regulates its differentiation state by its own migration. The male germ cells differentiate and mature with the formation of syncytia, failure of forming the appropriate syncytia results in the arrest at the spermatocyte stage. However, the detailed molecular mechanisms of male germ cell morphological regulation are unknown. Here, we found that EXOC1, a member of the Exocyst complex, is important for the pseudopod formation of spermatogonia and spermatocyte syncytia in mice. EXOC1 contributes to the pseudopod formation of spermatogonia by inactivating the Rho family small GTPase Rac1 and also functions in the spermatocyte syncytia with the SNARE proteins STX2 and SNAP23. Since EXOC1 is known to bind to several cell morphogenesis factors, this study is expected to be the starting point for the discovery of many morphological regulators of male germ cells.
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Affiliation(s)
- Yuki Osawa
- Master's Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan
| | - Kazuya Murata
- Laboratory Animal Resource Center, Trans-border Medical Research Center, University of Tsukuba, Tsukuba, Japan
| | - Miho Usui
- School of Medical Sciences, University of Tsukuba, Tsukuba, Japan
| | - Yumeno Kuba
- Master's Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan
| | - Hoai Thu Le
- Ph.D Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, Tsukuba, Japan
| | - Natsuki Mikami
- Ph.D Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, Tsukuba, Japan
| | - Toshinori Nakagawa
- Division of Germ Cell Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Basic Biology, School of Life Science, Graduate University for Advanced Studies (Sokendai), Okazaki, Japan
| | - Yoko Daitoku
- Laboratory Animal Resource Center, Trans-border Medical Research Center, University of Tsukuba, Tsukuba, Japan
| | - Kanako Kato
- Laboratory Animal Resource Center, Trans-border Medical Research Center, University of Tsukuba, Tsukuba, Japan
| | - Hossam Hassan Shawki
- Department of Comparative and Experimental Medicine, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Yoshihisa Ikeda
- Doctoral program in Biomedical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan
| | - Akihiro Kuno
- Laboratory Animal Resource Center, Trans-border Medical Research Center, University of Tsukuba, Tsukuba, Japan.,Ph.D Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, Tsukuba, Japan
| | - Kento Morimoto
- Doctoral program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan
| | - Yoko Tanimoto
- Laboratory Animal Resource Center, Trans-border Medical Research Center, University of Tsukuba, Tsukuba, Japan
| | - Tra Thi Huong Dinh
- Laboratory Animal Resource Center, Trans-border Medical Research Center, University of Tsukuba, Tsukuba, Japan
| | - Ken-Ichi Yagami
- Laboratory Animal Resource Center, Trans-border Medical Research Center, University of Tsukuba, Tsukuba, Japan
| | - Masatsugu Ema
- Department of Stem Cells and Human Disease Models, Research Center for Animal Life Science, Shiga University of Medical Science, Otsu, Japan
| | - Shosei Yoshida
- Division of Germ Cell Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Basic Biology, School of Life Science, Graduate University for Advanced Studies (Sokendai), Okazaki, Japan
| | - Satoru Takahashi
- Laboratory Animal Resource Center, Trans-border Medical Research Center, University of Tsukuba, Tsukuba, Japan
| | - Seiya Mizuno
- Laboratory Animal Resource Center, Trans-border Medical Research Center, University of Tsukuba, Tsukuba, Japan
| | - Fumihiro Sugiyama
- Laboratory Animal Resource Center, Trans-border Medical Research Center, University of Tsukuba, Tsukuba, Japan
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10
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Van Bergen NJ, Ahmed SM, Collins F, Cowley M, Vetro A, Dale RC, Hock DH, de Caestecker C, Menezes M, Massey S, Ho G, Pisano T, Glover S, Gusman J, Stroud DA, Dinger M, Guerrini R, Macara IG, Christodoulou J. Mutations in the exocyst component EXOC2 cause severe defects in human brain development. J Exp Med 2021; 217:151928. [PMID: 32639540 PMCID: PMC7537385 DOI: 10.1084/jem.20192040] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 02/03/2020] [Accepted: 04/03/2020] [Indexed: 12/30/2022] Open
Abstract
The exocyst, an octameric protein complex, is an essential component of the membrane transport machinery required for tethering and fusion of vesicles at the plasma membrane. We report pathogenic variants in an exocyst subunit, EXOC2 (Sec5). Affected individuals have severe developmental delay, dysmorphism, and brain abnormalities; variability associated with epilepsy; and poor motor skills. Family 1 had two offspring with a homozygous truncating variant in EXOC2 that leads to nonsense-mediated decay of EXOC2 transcript, a severe reduction in exocytosis and vesicle fusion, and undetectable levels of EXOC2 protein. The patient from Family 2 had a milder clinical phenotype and reduced exocytosis. Cells from both patients showed defective Arl13b localization to the primary cilium. The discovery of mutations that partially disable exocyst function provides valuable insight into this essential protein complex in neural development. Since EXOC2 and other exocyst complex subunits are critical to neuronal function, our findings suggest that EXOC2 variants are the cause of the patients’ neurological disorders.
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Affiliation(s)
- Nicole J Van Bergen
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
| | - Syed Mukhtar Ahmed
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN
| | - Felicity Collins
- Western Sydney Genetics Program, Children's Hospital at Westmead, Sydney, New South Wales, Australia.,Medical Genomics Department, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Mark Cowley
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, New South Wales, Australia.,St Vincent's Clinical School, University of New South Wales Sydney, Sydney, New South Wales, Australia.,Children's Cancer Institute, Kensington, New South Wales, Australia
| | - Annalisa Vetro
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Meyer Children's Hospital, University of Florence, Florence, Italy
| | - Russell C Dale
- Department of Paediatric Neurology, The Children's Hospital at Westmead, Sydney, New South Wales, Australia.,Kids Neuroscience Centre, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Daniella H Hock
- Department of Biochemistry and Molecular Biology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Christian de Caestecker
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN
| | - Minal Menezes
- Kids Research, The Children's Hospital at Westmead, Sydney, New South Wales, Australia
| | - Sean Massey
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Gladys Ho
- Western Sydney Genetics Program, Children's Hospital at Westmead, Sydney, New South Wales, Australia
| | - Tiziana Pisano
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Meyer Children's Hospital, University of Florence, Florence, Italy
| | - Seana Glover
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
| | - Jovanka Gusman
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
| | - David A Stroud
- Department of Biochemistry and Molecular Biology and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Marcel Dinger
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, New South Wales, Australia.,School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington Campus, Sydney, New South Wales, Australia
| | - Renzo Guerrini
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Meyer Children's Hospital, University of Florence, Florence, Italy
| | - Ian G Macara
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN
| | - John Christodoulou
- Brain and Mitochondrial Research Group, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia.,Victorian Clinical Genetics Services, Royal Children's Hospital, Parkville, Victoria, Australia
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11
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Fais M, Sanna G, Galioto M, Nguyen TTD, Trần MUT, Sini P, Carta F, Turrini F, Xiong Y, Dawson TM, Dawson VL, Crosio C, Iaccarino C. LRRK2 Modulates the Exocyst Complex Assembly by Interacting with Sec8. Cells 2021; 10:203. [PMID: 33498474 PMCID: PMC7909581 DOI: 10.3390/cells10020203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 01/12/2021] [Accepted: 01/18/2021] [Indexed: 11/17/2022] Open
Abstract
Mutations in LRRK2 play a critical role in both familial and sporadic Parkinson's disease (PD). Up to date, the role of LRRK2 in PD onset and progression remains largely unknown. However, experimental evidence highlights a critical role of LRRK2 in the control of vesicle trafficking, likely by Rab phosphorylation, that in turn may regulate different aspects of neuronal physiology. Here we show that LRRK2 interacts with Sec8, one of eight subunits of the exocyst complex. The exocyst complex is an evolutionarily conserved multisubunit protein complex mainly involved in tethering secretory vesicles to the plasma membrane and implicated in the regulation of multiple biological processes modulated by vesicle trafficking. Interestingly, Rabs and exocyst complex belong to the same protein network. Our experimental evidence indicates that LRRK2 kinase activity or the presence of the LRRK2 kinase domain regulate the assembly of exocyst subunits and that the over-expression of Sec8 significantly rescues the LRRK2 G2019S mutant pathological effect. Our findings strongly suggest an interesting molecular mechanism by which LRRK2 could modulate vesicle trafficking and may have important implications to decode the complex role that LRRK2 plays in neuronal physiology.
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Affiliation(s)
- Milena Fais
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Giovanna Sanna
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Manuela Galioto
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Thi Thanh Duyen Nguyen
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Mai Uyên Thi Trần
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Paola Sini
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | | | - Franco Turrini
- Nurex Srl, 07100 Sassari, Italy; (F.C.); (F.T.)
- Department of Oncology, University of Turin, 10126 Turin, Italy
| | - Yulan Xiong
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; (Y.X.); (T.M.D.); (V.L.D.)
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ted M. Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; (Y.X.); (T.M.D.); (V.L.D.)
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Valina L. Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; (Y.X.); (T.M.D.); (V.L.D.)
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Claudia Crosio
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Ciro Iaccarino
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
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12
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Glutamatergic Receptor Trafficking and Delivery: Role of the Exocyst Complex. Cells 2020; 9:cells9112402. [PMID: 33153008 PMCID: PMC7693776 DOI: 10.3390/cells9112402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 10/21/2020] [Accepted: 10/23/2020] [Indexed: 12/29/2022] Open
Abstract
Cells comprise several intracellular membrane compartments that allow them to function properly. One of these functions is cargo movement, typically proteins and membranes within cells. These cargoes ride microtubules through vesicles from Golgi and recycling endosomes to the plasma membrane in order to be delivered and exocytosed. In neurons, synaptic functions employ this cargo trafficking to maintain inter-neuronal communication optimally. One of the complexes that oversee vesicle trafficking and tethering is the exocyst. The exocyst is a protein complex containing eight subunits first identified in yeast and then characterized in multicellular organisms. This complex is related to several cellular processes, including cellular growth, division, migration, and morphogenesis, among others. It has been associated with glutamatergic receptor trafficking and tethering into the synapse, providing the molecular machinery to deliver receptor-containing vesicles into the plasma membrane in a constitutive manner. In this review, we discuss the evidence so far published regarding receptor trafficking and the exocyst complex in both basal and stimulated levels, comparing constitutive trafficking and long-term potentiation-related trafficking.
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13
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Coulter ME, Musaev D, DeGennaro EM, Zhang X, Henke K, James KN, Smith RS, Hill RS, Partlow JN, Muna Al-Saffar, Kamumbu AS, Hatem N, Barkovich AJ, Aziza J, Chassaing N, Zaki MS, Sultan T, Burglen L, Rajab A, Al-Gazali L, Mochida GH, Harris MP, Gleeson JG, Walsh CA. Regulation of human cerebral cortical development by EXOC7 and EXOC8, components of the exocyst complex, and roles in neural progenitor cell proliferation and survival. Genet Med 2020; 22:1040-1050. [PMID: 32103185 PMCID: PMC7272323 DOI: 10.1038/s41436-020-0758-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 01/16/2020] [Accepted: 01/27/2020] [Indexed: 01/31/2023] Open
Abstract
PURPOSE The exocyst complex is a conserved protein complex that mediates fusion of intracellular vesicles to the plasma membrane and is implicated in processes including cell polarity, cell migration, ciliogenesis, cytokinesis, autophagy, and fusion of secretory vesicles. The essential role of these genes in human genetic disorders, however, is unknown. METHODS We performed homozygosity mapping and exome sequencing of consanguineous families with recessively inherited brain development disorders. We modeled an EXOC7 splice variant in vitro and examined EXOC7 messenger RNA (mRNA) expression in developing mouse and human cortex. We modeled exoc7 loss-of-function in a zebrafish knockout. RESULTS We report variants in exocyst complex members, EXOC7 and EXOC8, in a novel disorder of cerebral cortex development. In EXOC7, we identified four independent partial loss-of-function (LOF) variants in a recessively inherited disorder characterized by brain atrophy, seizures, and developmental delay, and in severe cases, microcephaly and infantile death. In EXOC8, we found a homozygous truncating variant in a family with a similar clinical disorder. We modeled exoc7 deficiency in zebrafish and found the absence of exoc7 causes microcephaly. CONCLUSION Our results highlight the essential role of the exocyst pathway in normal cortical development and how its perturbation causes complex brain disorders.
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Affiliation(s)
- Michael E Coulter
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
- Program in Neuroscience and Harvard/MIT MD-PHD Program, Harvard Medical School, Boston, MA, USA
| | - Damir Musaev
- Department of Neurosciences and Howard Hughes Medical Institute, University of San Diego, La Jolla, CA, USA
| | - Ellen M DeGennaro
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Xiaochang Zhang
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
| | - Katrin Henke
- Division of Orthopedic Research, Boston Children's Hospital, Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Kiely N James
- Department of Neurosciences and Howard Hughes Medical Institute, University of San Diego, La Jolla, CA, USA
| | - Richard S Smith
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
| | - R Sean Hill
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
| | - Jennifer N Partlow
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
| | - Muna Al-Saffar
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
- Department of Paediatrics, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - A Stacy Kamumbu
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
| | - Nicole Hatem
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
| | - A James Barkovich
- Benioff Children's Hospital, Departments of Radiology, Pediatrics, Neurology, and Neurological Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Jacqueline Aziza
- Département de Pathologie, Institut Universitaire du Cancer de Toulouse-Oncopole-CHU Toulouse, Toulouse, France
| | - Nicolas Chassaing
- Service de Génétique Médicale, CHU Toulouse, Toulouse, France
- UDEAR; UMR 1056 Inserm-Université de Toulouse, Toulouse, France
| | - Maha S Zaki
- Clinical Genetics Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, Egypt
| | - Tipu Sultan
- Department of Pediatric Neurology, Institute of Child Health & The Children's Hospital, Lahore, Pakistan
| | - Lydie Burglen
- Centre de référence des malformations et maladies congénitales du cervelet, Département de génétique, AP-HP.Sorbonne Université, Paris, France
- Hôpital Trousseau and Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, Paris, France
| | - Anna Rajab
- National Genetics Center, Directorate General of Health Affairs, Ministry of Health, Muscat, Oman
| | - Lihadh Al-Gazali
- Department of Paediatrics, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Ganeshwaran H Mochida
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA
- Department of Neurology, Massachusetts General Hospital, Boston, MA, USA
| | - Matthew P Harris
- Division of Orthopedic Research, Boston Children's Hospital, Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Joseph G Gleeson
- Department of Neurosciences and Howard Hughes Medical Institute, University of San Diego, La Jolla, CA, USA.
| | - Christopher A Walsh
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Departments of Pediatrics and Neurology, Harvard Medical School, Boston, MA, USA.
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14
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Lipschutz JH. The role of the exocyst in renal ciliogenesis, cystogenesis, tubulogenesis, and development. Kidney Res Clin Pract 2019; 38:260-266. [PMID: 31284362 PMCID: PMC6727897 DOI: 10.23876/j.krcp.19.050] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 05/13/2019] [Accepted: 05/20/2019] [Indexed: 12/23/2022] Open
Abstract
The exocyst is a highly conserved eight-subunit protein complex (EXOC1–8) involved in the targeting and docking of exocytic vesicles translocating from the trans-Golgi network to various sites in renal cells. EXOC5 is a central exocyst component because it connects EXOC6, bound to the vesicles exiting the trans-Golgi network via the small GTPase RAB8, to the rest of the exocyst complex at the plasma membrane. In the kidney, the exocyst complex is involved in primary ciliognesis, cystogenesis, and tubulogenesis. The exocyst, and its regulators, have also been found in urinary extracellular vesicles, and may be centrally involved in urocrine signaling and repair following acute kidney injury. The exocyst is centrally involved in the development of other organs, including the eye, ear, and heart. The exocyst is regulated by many different small GTPases of the RHO, RAL, RAB, and ARF families. The small GTPases, and their guanine nucleotide exchange factors and GTPase-activating proteins, likely give the exocyst specificity of function. The recent development of a floxed Exoc5 mouse line will aid researchers in studying the role of the exocyst in multiple cells and organ types by allowing for tissue-specific knockout, in conjunction with Cre-driver mouse lines.
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Affiliation(s)
- Joshua H Lipschutz
- Department of Medicine, Medical University of South Carolina, Charleston, SC, USA.,Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC, USA
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15
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Nishida‐Fukuda H. The Exocyst: Dynamic Machine or Static Tethering Complex? Bioessays 2019; 41:e1900056. [DOI: 10.1002/bies.201900056] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 05/14/2019] [Indexed: 01/15/2023]
Affiliation(s)
- Hisayo Nishida‐Fukuda
- Department of Genome Editing, Institute of Biomedical ScienceKansai Medical University2‐5‐1 Shin‐machi, Hirakata Osaka 5731010 Japan
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16
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Ahmed SM, Nishida-Fukuda H, Li Y, McDonald WH, Gradinaru CC, Macara IG. Exocyst dynamics during vesicle tethering and fusion. Nat Commun 2018; 9:5140. [PMID: 30510181 PMCID: PMC6277416 DOI: 10.1038/s41467-018-07467-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 11/01/2018] [Indexed: 11/15/2022] Open
Abstract
The exocyst is a conserved octameric complex that tethers exocytic vesicles to the plasma membrane prior to fusion. Exocyst assembly and delivery mechanisms remain unclear, especially in mammalian cells. Here we tagged multiple endogenous exocyst subunits with sfGFP or Halo using Cas9 gene-editing, to create single and double knock-in lines of mammary epithelial cells, and interrogated exocyst dynamics by high-speed imaging and correlation spectroscopy. We discovered that mammalian exocyst is comprised of tetrameric subcomplexes that can associate independently with vesicles and plasma membrane and are in dynamic equilibrium with octamer and monomers. Membrane arrival times are similar for subunits and vesicles, but with a small delay (~80msec) between subcomplexes. Departure of SEC3 occurs prior to fusion, whereas other subunits depart just after fusion. About 9 exocyst complexes are associated per vesicle. These data reveal the mammalian exocyst as a remarkably dynamic two-part complex and provide important insights into assembly/disassembly mechanisms. Exocyst complex tethers vesicles to plasma membranes, but assembly mechanisms remain unclear. Here, the authors use Cas9 gene editing to tag exocyst components in epithelial cells, and find that exocyst subcomplexes are recruited to membranes independently, but are both needed for vesicle fusion.
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Affiliation(s)
- Syed Mukhtar Ahmed
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37240, USA.
| | - Hisayo Nishida-Fukuda
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37240, USA.,Department of Biochemistry and Molecular Genetics, Ehime University Graduate School of Medicine, Toon, Ehime, 7910295, Japan.,Department of Hepato-Biliary-Pancreatic and Breast Surgery, Ehime University Graduate School of Medicine, Toon, Ehime, 7910295, Japan.,Department of Genome Editing, Institute of Biomedical Sciences, Kansai Medical University, Hirakata, 5731010, Japan
| | - Yuchong Li
- Department of Physics, University of Toronto, Toronto, ON, M5S 1A7, Canada.,Department of Chemical & Physical Sciences, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada
| | - W Hayes McDonald
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, 37240, USA
| | - Claudiu C Gradinaru
- Department of Physics, University of Toronto, Toronto, ON, M5S 1A7, Canada.,Department of Chemical & Physical Sciences, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada
| | - Ian G Macara
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, 37240, USA.
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17
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CSI1, PATROL1, and exocyst complex cooperate in delivery of cellulose synthase complexes to the plasma membrane. Proc Natl Acad Sci U S A 2018; 115:E3578-E3587. [PMID: 29581258 PMCID: PMC5899483 DOI: 10.1073/pnas.1800182115] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Cellulose synthesis occurs exclusively at the plasma membrane by cellulose synthase complexes (CSCs). Therefore, delivery of CSCs to discrete sites at the plasma membrane is critical for cellulose synthesis. Despite their significance, the delivery of CSCs is poorly understood. Here we used proteomics approaches, functional genetics, and live cell imaging to show that the de novo secretion of CSCs is mediated by cooperation among cellulose synthase interactive 1 (CSI1), the plant-specific protein PATROL1, and exocyst complex in Arabidopsis thaliana We propose that CSI1 plays a role in marking the docking site, which allows CSCs-containing vesicles access to the plasma membrane through its interaction with microtubules. PATROL1 assists in exocytosis by its interaction with multiple components, including CSI1, CSCs, and exocyst subunits. Both PATROL1 and the exocyst complex determine the rate of delivery of CSCs to the plasma membrane. By monitoring the exocyst complex, PATROL1, CSI1, and CSCs dynamics in real time, we present a timeline of events for exocytosis of CSCs. Our findings provide unique insights into the evolution of exocytosis in eukaryotes.
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18
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Polgar N, Fogelgren B. Regulation of Cell Polarity by Exocyst-Mediated Trafficking. Cold Spring Harb Perspect Biol 2018; 10:cshperspect.a031401. [PMID: 28264817 DOI: 10.1101/cshperspect.a031401] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
One requirement for establishing polarity within a cell is the asymmetric trafficking of intracellular vesicles to the plasma membrane. This tightly regulated process creates spatial and temporal differences in both plasma membrane composition and the membrane-associated proteome. Asymmetric membrane trafficking is also a critical mechanism to regulate cell differentiation, signaling, and physiology. Many eukaryotic cell types use the eight-protein exocyst complex to orchestrate polarized vesicle trafficking to certain membrane locales. Members of the exocyst were originally discovered in yeast while screening for proteins required for the delivery of secretory vesicles to the budding daughter cell. The same eight exocyst genes are conserved in mammals, in which the specifics of exocyst-mediated trafficking are highly cell-type-dependent. Some exocyst members bind to certain Rab GTPases on intracellular vesicles, whereas others localize to the plasma membrane at the site of exocytosis. Assembly of the exocyst holocomplex is responsible for tethering these vesicles to the plasma membrane before their soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-mediated exocytosis. In this review, we will focus on the role and regulation of the exocyst complex in targeted vesicular trafficking as related to the establishment and maintenance of cellular polarity. We will contrast exocyst function in apicobasal epithelial polarity versus front-back mesenchymal polarity, and the dynamic regulation of exocyst-mediated trafficking during cell phenotype transitions.
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Affiliation(s)
- Noemi Polgar
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813
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19
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Shin SW, Vogt EJ, Jimenez-Movilla M, Baibakov B, Dean J. Cytoplasmic cleavage of DPPA3 is required for intracellular trafficking and cleavage-stage development in mice. Nat Commun 2017; 8:1643. [PMID: 29158485 PMCID: PMC5696369 DOI: 10.1038/s41467-017-01387-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 09/05/2017] [Indexed: 01/06/2023] Open
Abstract
Degradation of maternal proteins by the ubiquitin-proteasome system (UPS) accompanies the maternal-to-zygotic transition. DPPA3/Stella/PGC7, encoded by a maternal effect gene, is present in the nucleus and cytoplasm of zygotes and has been associated with protecting the female pronucleus from TET3-mediated demethylation. We now report that cytoplasmic DPPA3 is partially cleaved by the ubiquitin-proteasome system and an N-terminus fragment remains in the cytoplasm where it associates with early and re-cycling endosomes. If DPPA3 is absent or if cleavage is prevented, multiple vesicles coalesce/aggregate and markers of lysosomes are decreased. Fertilized eggs develop poorly into blastocysts, which results in significantly decreased fecundity of Dppa3 R60A transgenic mice. This phenocopies aspects of Lamp1/2 knockdowns and Dppa3 KO embryos can be partially rescued in vitro by DPPA31-60 and to a lesser extent by LAMP1/2. Thus, the N-terminus of DPPA3 has a significant role in cytoplasmic vesicular trafficking in addition to its previously reported nuclear function.
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Affiliation(s)
- Seung-Wook Shin
- Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Edgar John Vogt
- Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Maria Jimenez-Movilla
- Department of Cell Biology and Histology, Medical School, University of Murcia, IMIB, 30100, Murcia, Spain
| | - Boris Baibakov
- Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Jurrien Dean
- Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, MD, 20892, USA.
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20
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Miao Y, Wu J, Abraham SN. Ubiquitination of Innate Immune Regulator TRAF3 Orchestrates Expulsion of Intracellular Bacteria by Exocyst Complex. Immunity 2017; 45:94-105. [PMID: 27438768 DOI: 10.1016/j.immuni.2016.06.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 04/26/2016] [Accepted: 06/21/2016] [Indexed: 12/27/2022]
Abstract
Although the intracellular trafficking system is integral to most physiologic activities, its role in mediating immune responses to infection has remained elusive. Here, we report that infected bladder epithelial cells (BECs) mobilized the exocyst complex, a powerful exporter of subcellular vesicles, to rapidly expel intracellular bacteria back for clearance. Toll-like receptor (TLR) 4 signals emanating from bacteria-containing vesicles (BCVs) were found to trigger K33-linked polyubiquitination of TRAF3 at Lys168, which was then detected by RalGDS, a guanine nucleotide exchange factor (GEF) that precipitated the assembly of the exocyst complex. Although this distinct modification of TRAF3 served to connect innate immune signaling to the cellular trafficking apparatus, it crucially ensured temporal and spatial accuracy in determining which among the many subcellular vesicles was recognized and selected for expulsion in response to innate immune signaling.
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Affiliation(s)
- Yuxuan Miao
- Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
| | - Jianxuan Wu
- Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA
| | - Soman N Abraham
- Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, NC 27710, USA; Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA; Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA; Program in Emerging Infectious Diseases, Duke-National University of Singapore, Singapore 169857, Singapore
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21
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Tanaka T, Goto K, Iino M. Sec8 modulates TGF-β induced EMT by controlling N-cadherin via regulation of Smad3/4. Cell Signal 2017; 29:115-126. [DOI: 10.1016/j.cellsig.2016.10.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 10/13/2016] [Accepted: 10/16/2016] [Indexed: 10/20/2022]
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22
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Tanaka T, Goto K, Iino M. Diverse Functions and Signal Transduction of the Exocyst Complex in Tumor Cells. J Cell Physiol 2016; 232:939-957. [DOI: 10.1002/jcp.25619] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 09/23/2016] [Indexed: 12/11/2022]
Affiliation(s)
- Toshiaki Tanaka
- Department of Anatomy and Cell Biology; School of Medicine; Yamagata University; Yamagata Japan
- Department of Dentistry, Oral and Maxillofacial Surgery; Plastic and Reconstructive Surgery; School of Medicine; Yamagata University; Yamagata Japan
| | - Kaoru Goto
- Department of Anatomy and Cell Biology; School of Medicine; Yamagata University; Yamagata Japan
| | - Mitsuyoshi Iino
- Department of Dentistry, Oral and Maxillofacial Surgery; Plastic and Reconstructive Surgery; School of Medicine; Yamagata University; Yamagata Japan
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23
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Broholm C, Olsson AH, Perfilyev A, Gillberg L, Hansen NS, Ali A, Mortensen B, Ling C, Vaag A. Human adipogenesis is associated with genome-wide DNA methylation and gene-expression changes. Epigenomics 2016; 8:1601-1617. [PMID: 27854126 DOI: 10.2217/epi-2016-0077] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
AIM To define the genomic distribution and function of DNA methylation changes during human adipogenesis. METHODS We isolated adipocyte-derived stem cells from 13 individuals and analyzed genome-wide DNA methylation and gene expression in cultured adipocyte-derived stem cells and mature adipocytes. RESULTS We observed altered DNA methylation of 11,947 CpG sites and altered expression of 11,830 transcripts after differentiation. De novo methylation was observed across all genomic elements. Co-existence of genes with both altered expression and DNA methylation was found in genes important for cell cycle and adipokine signaling. CONCLUSION Human adipogenesis is associated with significant DNA methylation changes across the entire genome and may impact regulation of cell cycle and adipokine signaling.
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Affiliation(s)
- Christa Broholm
- Department of Endocrinology, Diabetes & Metabolism, Rigshospitalet, Copenhagen, Denmark
| | - Anders Henrik Olsson
- Department of Endocrinology, Diabetes & Metabolism, Rigshospitalet, Copenhagen, Denmark
| | - Alexander Perfilyev
- Department of Clinical Sciences, Epigenetics & Diabetes Unit, Lund University Diabetes Centre, CRC, Malmö, Sweden
| | - Linn Gillberg
- Department of Endocrinology, Diabetes & Metabolism, Rigshospitalet, Copenhagen, Denmark
| | - Ninna Schiøler Hansen
- Department of Endocrinology, Diabetes & Metabolism, Rigshospitalet, Copenhagen, Denmark.,Faculty of Health & Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ashfaq Ali
- Department of Clinical Sciences, GAME, Lund University Diabetes Centre, CRC, Malmö, Sweden
| | | | - Charlotte Ling
- Department of Clinical Sciences, Epigenetics & Diabetes Unit, Lund University Diabetes Centre, CRC, Malmö, Sweden
| | - Allan Vaag
- Department of Endocrinology, Diabetes & Metabolism, Rigshospitalet, Copenhagen, Denmark.,Faculty of Health & Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Steno Diabetes Centre A/S, Gentofte, Denmark
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24
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Martin-Urdiroz M, Deeks MJ, Horton CG, Dawe HR, Jourdain I. The Exocyst Complex in Health and Disease. Front Cell Dev Biol 2016; 4:24. [PMID: 27148529 PMCID: PMC4828438 DOI: 10.3389/fcell.2016.00024] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 03/11/2016] [Indexed: 01/23/2023] Open
Abstract
Exocytosis involves the fusion of intracellular secretory vesicles with the plasma membrane, thereby delivering integral membrane proteins to the cell surface and releasing material into the extracellular space. Importantly, exocytosis also provides a source of lipid moieties for membrane extension. The tethering of the secretory vesicle before docking and fusion with the plasma membrane is mediated by the exocyst complex, an evolutionary conserved octameric complex of proteins. Recent findings indicate that the exocyst complex also takes part in other intra-cellular processes besides secretion. These various functions seem to converge toward defining a direction of membrane growth in a range of systems from fungi to plants and from neurons to cilia. In this review we summarize the current knowledge of exocyst function in cell polarity, signaling and cell-cell communication and discuss implications for plant and animal health and disease.
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Affiliation(s)
| | - Michael J Deeks
- Biosciences, College of Life and Environmental Sciences, University of Exeter Exeter, UK
| | - Connor G Horton
- Biosciences, College of Life and Environmental Sciences, University of Exeter Exeter, UK
| | - Helen R Dawe
- Biosciences, College of Life and Environmental Sciences, University of Exeter Exeter, UK
| | - Isabelle Jourdain
- Biosciences, College of Life and Environmental Sciences, University of Exeter Exeter, UK
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25
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Toh WH, Gleeson PA. Emerging Insights into the Roles of Membrane Tethers from Analysis of Whole Organisms: The Tip of an Iceberg? Front Cell Dev Biol 2016; 4:12. [PMID: 26973835 PMCID: PMC4770024 DOI: 10.3389/fcell.2016.00012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 02/08/2016] [Indexed: 12/02/2022] Open
Abstract
Membrane tethers have been identified throughout different compartments of the endomembrane system. It is now well established that a number of membrane tethers mediate docking of membrane carriers in anterograde and retrograde transport and in regulating the organization of membrane compartments. Much of our information on membrane tethers have been obtained from the analysis of individual membrane tethers in cultured cells. In the future it will be important to better appreciate the network of interactions mediated by tethers and the potential co-ordination of their collective functions in vivo. There are now a number of studies which have analyzed membrane tethers in tissues and organisms which are providing new insights into the role of this class of membrane protein at the physiological level. Here we review recent advances in the understanding of the function of membrane tethers from knock outs (or knock downs) in whole organisms and from mutations in tethers associated with disease.
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Affiliation(s)
- Wei Hong Toh
- The Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne Melbourne, VIC, Australia
| | - Paul A Gleeson
- The Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne Melbourne, VIC, Australia
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26
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Seixas C, Choi SY, Polgar N, Umberger NL, East MP, Zuo X, Moreiras H, Ghossoub R, Benmerah A, Kahn RA, Fogelgren B, Caspary T, Lipschutz JH, Barral DC. Arl13b and the exocyst interact synergistically in ciliogenesis. Mol Biol Cell 2016; 27:308-20. [PMID: 26582389 PMCID: PMC4713133 DOI: 10.1091/mbc.e15-02-0061] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 10/29/2015] [Accepted: 11/12/2015] [Indexed: 12/22/2022] Open
Abstract
Arl13b belongs to the ADP-ribosylation factor family within the Ras superfamily of regulatory GTPases. Mutations in Arl13b cause Joubert syndrome, which is characterized by congenital cerebellar ataxia, hypotonia, oculomotor apraxia, and mental retardation. Arl13b is highly enriched in cilia and is required for ciliogenesis in multiple organs. Nevertheless, the precise role of Arl13b remains elusive. Here we report that the exocyst subunits Sec8, Exo70, and Sec5 bind preferentially to the GTP-bound form of Arl13b, consistent with the exocyst being an effector of Arl13b. Moreover, we show that Arl13b binds directly to Sec8 and Sec5. In zebrafish, depletion of arl13b or the exocyst subunit sec10 causes phenotypes characteristic of defective cilia, such as curly tail up, edema, and abnormal pronephric kidney development. We explored this further and found a synergistic genetic interaction between arl13b and sec10 morphants in cilia-dependent phenotypes. Through conditional deletion of Arl13b or Sec10 in mice, we found kidney cysts and decreased ciliogenesis in cells surrounding the cysts. Moreover, we observed a decrease in Arl13b expression in the kidneys from Sec10 conditional knockout mice. Taken together, our results indicate that Arl13b and the exocyst function together in the same pathway leading to functional cilia.
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Affiliation(s)
- Cecília Seixas
- CEDOC, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
| | - Soo Young Choi
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425
| | - Noemi Polgar
- Department of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI 96813
| | - Nicole L Umberger
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30022
| | - Michael P East
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30022
| | - Xiaofeng Zuo
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425
| | - Hugo Moreiras
- CEDOC, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
| | - Rania Ghossoub
- Centre de Recherche en Cancérologie de Marseille, INSERM, UMR7258, 13009 Marseille, France
| | - Alexandre Benmerah
- INSERM UMR 1163, Laboratory of Inherited Kidney Diseases, 75015 Paris, France Paris Descartes-Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
| | - Richard A Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30022
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI 96813
| | - Tamara Caspary
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30022
| | - Joshua H Lipschutz
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425 Department of Medicine, RHJ Veterans Affairs Medical Center, Charleston, SC 29425
| | - Duarte C Barral
- CEDOC, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
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27
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Heider MR, Gu M, Duffy CM, Mirza AM, Marcotte LL, Walls AC, Farrall N, Hakhverdyan Z, Field MC, Rout MP, Frost A, Munson M. Subunit connectivity, assembly determinants and architecture of the yeast exocyst complex. Nat Struct Mol Biol 2016; 23:59-66. [PMID: 26656853 PMCID: PMC4752824 DOI: 10.1038/nsmb.3146] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 11/19/2015] [Indexed: 01/12/2023]
Abstract
The exocyst is a hetero-octameric complex that has been proposed to serve as the tethering complex for exocytosis, although it remains poorly understood at the molecular level. Here, we purified endogenous exocyst complexes from Saccharomyces cerevisiae and showed that they are stable and consist of all eight subunits with equal stoichiometry. Using a combination of biochemical and auxin induced-degradation experiments in yeast, we mapped the subunit connectivity, identified two stable four-subunit modules within the octamer and demonstrated that several known exocyst-binding partners are not necessary for exocyst assembly and stability. Furthermore, we visualized the structure of the yeast complex by using negative-stain electron microscopy; our results indicate that the exocyst exists predominantly as a stable, octameric complex with an elongated architecture that suggests that the subunits are contiguous helical bundles packed together into a bundle of long rods.
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Affiliation(s)
- Margaret R. Heider
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Mingyu Gu
- Department of Biochemistry, University of Utah, Salt Lake City, UT, USA
| | - Caroline M. Duffy
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Anne M. Mirza
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Laura L. Marcotte
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Alexandra C. Walls
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Nicholas Farrall
- Department of Biochemistry, University of Utah, Salt Lake City, UT, USA
| | - Zhanna Hakhverdyan
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA
| | - Mark C. Field
- Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, UK
| | - Michael P. Rout
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA
| | - Adam Frost
- Department of Biochemistry, University of Utah, Salt Lake City, UT, USA
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Mary Munson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
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28
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Peri-implantation lethality in mice carrying megabase-scale deletion on 5qc3.3 is caused by Exoc1 null mutation. Sci Rep 2015; 5:13632. [PMID: 26346620 PMCID: PMC4562154 DOI: 10.1038/srep13632] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 08/03/2015] [Indexed: 01/28/2023] Open
Abstract
We found a novel spontaneous mouse mutant with depigmentation in the ventral body, which we called White Spotting (WS) mouse. Genetic investigation revealed deletion of a > 1.2-Mb genomic region containing nine genes (Kit, Kdr, Srd5a3, Tmeme165, Clock, Pdcl2, Nmu, Exoc1, and Cep135). We designated this mutant allele KitWS. Interestingly, homozygous mutants (KitWS/WS) showed a peri-implantation lethal phenotype. Expression analyses of these nine genes in blastocysts suggested that Exoc1 was a prime candidate for this phenotype. We produced Exoc1 knockout mice, and the same peri-implantation lethal phenotype was seen in Exoc1−/− embryos. In addition, the polygenic effect without Exoc1 was investigated in genome-edited KitWE mice carrying the Mb-scale deletion induced by the CRISPR/Cas9 system. As KitWE/WE embryos did not exhibit the abnormal phenotype, which was seen in KitWS/WS. We concluded that peri-implantation lethality in KitWS/WS was caused by a monogenic defect of Exoc1.
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29
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Urothelial Defects from Targeted Inactivation of Exocyst Sec10 in Mice Cause Ureteropelvic Junction Obstructions. PLoS One 2015; 10:e0129346. [PMID: 26046524 PMCID: PMC4457632 DOI: 10.1371/journal.pone.0129346] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 05/07/2015] [Indexed: 01/12/2023] Open
Abstract
Most cases of congenital obstructive nephropathy are the result of ureteropelvic junction obstructions, and despite their high prevalence, we have a poor understanding of their etiology and scarcity of genetic models. The eight-protein exocyst complex regulates polarized exocytosis of intracellular vesicles in a large variety of cell types. Here we report generation of a conditional knockout mouse for Sec10, a central component of the exocyst, which is the first conditional allele for any exocyst gene. Inactivation of Sec10 in ureteric bud-derived cells using Ksp1.3-Cre mice resulted in severe bilateral hydronephrosis and complete anuria in newborns, with death occurring 6-14 hours after birth. Sec10 FL/FL;Ksp-Cre embryos developed ureteropelvic junction obstructions between E17.5 and E18.5 as a result of degeneration of the urothelium and subsequent overgrowth by surrounding mesenchymal cells. The urothelial cell layer that lines the urinary tract must maintain a hydrophobic luminal barrier again urine while remaining highly stretchable. This barrier is largely established by production of uroplakin proteins that are transported to the apical surface to establish large plaques. By E16.5, Sec10 FL/FL;Ksp-Cre ureter and pelvic urothelium showed decreased uroplakin-3 protein at the luminal surface, and complete absence of uroplakin-3 by E17.5. Affected urothelium at the UPJ showed irregular barriers that exposed the smooth muscle layer to urine, suggesting this may trigger the surrounding mesenchymal cells to overgrow the lumen. Findings from this novel mouse model show Sec10 is critical for the development of the urothelium in ureters, and provides experimental evidence that failure of this urothelial barrier may contribute to human congenital urinary tract obstructions.
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30
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SEC-10 and RAB-10 coordinate basolateral recycling of clathrin-independent cargo through endosomal tubules in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2014; 111:15432-7. [PMID: 25301900 DOI: 10.1073/pnas.1408327111] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Despite the increasing number of regulatory proteins identified in clathrin-independent endocytic (CIE) pathways, our understanding of the exact functions of these proteins and the sequential manner in which they function remains limited. In this study, using the Caenorhabditis elegans intestine as a model, we observed a unique structure of interconnected endosomal tubules, which is required for the basolateral recycling of several CIE cargoes including hTAC, GLUT1, and DAF-4. SEC-10 is a subunit of the octameric protein complex exocyst. Depleting SEC-10 and several other exocyst components disrupted the endosomal tubules into various ring-like structures. An epistasis analysis further suggested that SEC-10 operates at the intermediate step between early endosomes and recycling endosomes. The endosomal tubules were also sensitive to inactivation of the Rab GTPase RAB-10 and disruption of microtubules. Taken together, our data suggest that SEC-10 coordinates with RAB-10 and microtubules to form the endosomal tubular network for efficient recycling of particular CIE cargoes.
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31
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Heider MR, Munson M. Exorcising the exocyst complex. Traffic 2012; 13:898-907. [PMID: 22420621 DOI: 10.1111/j.1600-0854.2012.01353.x] [Citation(s) in RCA: 248] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 03/12/2012] [Accepted: 03/15/2012] [Indexed: 11/26/2022]
Abstract
The exocyst complex is an evolutionarily conserved multisubunit protein complex implicated in tethering secretory vesicles to the plasma membrane. Originally identified two decades ago in budding yeast, investigations using several different eukaryotic systems have since made great progress toward determination of the overall structure and organization of the eight exocyst subunits. Studies point to a critical role for the complex as a spatiotemporal regulator through the numerous protein and lipid interactions of its subunits, although a molecular understanding of exocyst function has been challenging to elucidate. Recent progress demonstrates that the exocyst is also important for additional trafficking steps and cellular processes beyond exocytosis, with links to development and disease. In this review, we discuss current knowledge of exocyst architecture, assembly, regulation and its roles in a variety of cellular trafficking pathways.
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Affiliation(s)
- Margaret R Heider
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
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32
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Chen XW, Leto D, Xiao J, Goss J, Wang Q, Shavit JA, Xiong T, Yu G, Ginsburg D, Toomre D, Xu Z, Saltiel AR. Exocyst function is regulated by effector phosphorylation. Nat Cell Biol 2011; 13:580-8. [PMID: 21516108 PMCID: PMC3904505 DOI: 10.1038/ncb2226] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Accepted: 02/17/2011] [Indexed: 02/07/2023]
Abstract
The exocyst complex tethers vesicles at sites of fusion through interactions with small GTPases. The G-protein RalA resides on Glut4 vesicles, and binds to the exocyst after activation by insulin, but must then disengage to ensure continuous exocytosis. Here we report that after recognition of the exocyst by activated RalA, disengagement occurs through phosphorylation of its effector Sec5, rather than RalA inactivation. Sec5 undergoes phosphorylation in the G-protein binding domain, allosterically reducing RalA interaction. The phosphorylation event is catalyzed by protein kinase C and is reversed by an exocyst-associated phosphatase. Introduction of Sec5 bearing mutations of the phosphorylation site to either alanine or aspartate disrupts insulin-stimulated Glut4 exocytosis, as well as other trafficking processes in polarized epithelial cells and during development of zebrafish embryos. The exocyst thus serves as a “gatekeeper” for exocytic vesicles through a circuit of engagement, disengagement, and re-engagement with G proteins.
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Affiliation(s)
- Xiao-Wei Chen
- Life Sciences Institute, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA
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33
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Fogelgren B, Lin SY, Zuo X, Jaffe KM, Park KM, Reichert RJ, Bell PD, Burdine RD, Lipschutz JH. The exocyst protein Sec10 interacts with Polycystin-2 and knockdown causes PKD-phenotypes. PLoS Genet 2011; 7:e1001361. [PMID: 21490950 PMCID: PMC3072367 DOI: 10.1371/journal.pgen.1001361] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 03/02/2011] [Indexed: 01/26/2023] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is characterized by formation of renal cysts that destroy the kidney. Mutations in PKD1 and PKD2, encoding polycystins-1 and -2, cause ADPKD. Polycystins are thought to function in primary cilia, but it is not well understood how these and other proteins are targeted to cilia. Here, we provide the first genetic and biochemical link between polycystins and the exocyst, a highly-conserved eight-protein membrane trafficking complex. We show that knockdown of exocyst component Sec10 yields cellular phenotypes associated with ADPKD, including loss of flow-generated calcium increases, hyperproliferation, and abnormal activation of MAPK. Sec10 knockdown in zebrafish phenocopies many aspects of polycystin-2 knockdown-including curly tail up, left-right patterning defects, glomerular expansion, and MAPK activation-suggesting that the exocyst is required for pkd2 function in vivo. We observe a synergistic genetic interaction between zebrafish sec10 and pkd2 for many of these cilia-related phenotypes. Importantly, we demonstrate a biochemical interaction between Sec10 and the ciliary proteins polycystin-2, IFT88, and IFT20 and co-localization of the exocyst and polycystin-2 at the primary cilium. Our work supports a model in which the exocyst is required for the ciliary localization of polycystin-2, thus allowing for polycystin-2 function in cellular processes.
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Affiliation(s)
- Ben Fogelgren
- Department of Medicine, University of Pennsylvania, Philadelphia,
Pennsylvania, United States of America
| | - Shin-Yi Lin
- Department of Molecular Biology, Princeton University, Princeton, New
Jersey, United States of America
| | - Xiaofeng Zuo
- Department of Medicine, University of Pennsylvania, Philadelphia,
Pennsylvania, United States of America
| | - Kimberly M. Jaffe
- Department of Molecular Biology, Princeton University, Princeton, New
Jersey, United States of America
| | - Kwon Moo Park
- Department of Medicine, University of Pennsylvania, Philadelphia,
Pennsylvania, United States of America
- Department of Anatomy and BK 21 Project, Kyungpook National University,
Daegu, Republic of Korea
| | - Ryan J. Reichert
- Department of Medicine, Medical University of South Carolina, Charleston,
South Carolina, United States of America
| | - P. Darwin Bell
- Department of Medicine, Medical University of South Carolina, Charleston,
South Carolina, United States of America
| | - Rebecca D. Burdine
- Department of Molecular Biology, Princeton University, Princeton, New
Jersey, United States of America
| | - Joshua H. Lipschutz
- Department of Medicine, University of Pennsylvania, Philadelphia,
Pennsylvania, United States of America
- Department of Medicine, Philadelphia Veterans Affairs Medical Center,
Philadelphia, Pennsylvania, United States of America
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34
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Estey MP, Di Ciano-Oliveira C, Froese CD, Bejide MT, Trimble WS. Distinct roles of septins in cytokinesis: SEPT9 mediates midbody abscission. ACTA ACUST UNITED AC 2010; 191:741-9. [PMID: 21059847 PMCID: PMC2983063 DOI: 10.1083/jcb.201006031] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Septins are a family of GTP-binding proteins implicated in mammalian cell division. Most studies examining the role of septins in this process have treated the family as a whole, thus neglecting the possibility that individual members may have diverse functions. To address this, we individually depleted each septin family member expressed in HeLa cells by siRNA and assayed for defects in cell division by immunofluorescence and time-lapse microscopy. Depletion of SEPT2, SEPT7, and SEPT11 causes defects in the early stages of cytokinesis, ultimately resulting in binucleation. In sharp contrast, SEPT9 is dispensable for the early stages of cell division, but is critical for the final separation of daughter cells. Rescue experiments indicate that SEPT9 isoforms containing the N-terminal region are sufficient to drive cytokinesis. We demonstrate that SEPT9 mediates the localization of the vesicle-tethering exocyst complex to the midbody, providing mechanistic insight into the role of SEPT9 during abscission.
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Affiliation(s)
- Mathew P Estey
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
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35
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Schwenger DB, Kuner T. Acute genetic perturbation of exocyst function in the rat calyx of Held impedes structural maturation, but spares synaptic transmission. Eur J Neurosci 2010; 32:974-84. [DOI: 10.1111/j.1460-9568.2010.07391.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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36
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Takaya A, Kamio T, Masuda M, Mochizuki N, Sawa H, Sato M, Nagashima K, Mizutani A, Matsuno A, Kiyokawa E, Matsuda M. R-Ras regulates exocytosis by Rgl2/Rlf-mediated activation of RalA on endosomes. Mol Biol Cell 2007; 18:1850-60. [PMID: 17344481 PMCID: PMC1855010 DOI: 10.1091/mbc.e06-08-0765] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
R-Ras is a Ras-family small GTPase that regulates various cellular functions such as apoptosis and cell adhesion. Here, we demonstrate a role of R-Ras in exocytosis. By the use of specific anti-R-Ras antibody, we found that R-Ras was enriched on both early and recycling endosomes in a wide range of cell lines. Using a fluorescence resonance energy transfer-based probe for R-Ras activity, R-Ras activity was found to be higher on endosomes than on the plasma membrane. This high R-Ras activity on the endosomes correlated with the accumulation of an R-Ras effector, the Rgl2/Rlf guanine nucleotide exchange factor for RalA, and also with high RalA activity. The essential role played by R-Ras in inducing high levels of RalA activity on the endosomes was evidenced by the short hairpin RNA (shRNA)-mediated suppression of R-Ras and by the expression of R-Ras GAP. In agreement with the reported role of RalA in exocytosis, the shRNA of either R-Ras or RalA was found to suppress calcium-triggered exocytosis in PC12 pheochromocytoma cells. These data revealed that R-Ras activates RalA on endosomes and that it thereby positively regulates exocytosis.
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Affiliation(s)
- Akiyuki Takaya
- *Department of Signal Transduction, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Osaka 565-0871, Japan
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
| | - Takahiro Kamio
- *Department of Signal Transduction, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Osaka 565-0871, Japan
| | - Michitaka Masuda
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
| | - Naoki Mochizuki
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
| | - Hirofumi Sawa
- Laboratory of Molecular and Cellular Pathology, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
| | - Mami Sato
- Laboratory of Molecular and Cellular Pathology, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
| | - Kazuo Nagashima
- Laboratory of Molecular and Cellular Pathology, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
| | - Akiko Mizutani
- Basic Medical Science and Molecular Medicine, Tokai University School of Medicine, Kanagawa 259-1193, Japan; and
| | - Akira Matsuno
- Department of Neurosurgery, Teikyo University Ichihara Hospital, Chiba 299-0111, Japan
| | - Etsuko Kiyokawa
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
| | - Michiyuki Matsuda
- *Department of Signal Transduction, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Osaka 565-0871, Japan
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
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37
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Wang S, Hsu SC. The molecular mechanisms of the mammalian exocyst complex in exocytosis. Biochem Soc Trans 2007; 34:687-90. [PMID: 17052175 DOI: 10.1042/bst0340687] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Exocytosis is a highly ordered vesicle trafficking pathway that targets proteins to the plasma membrane for membrane addition or secretion. Research over the years has discovered many proteins that participate at various stages in the mammalian exocytotic pathway. At the early stage of exocytosis, co-atomer proteins and their respective adaptors and GTPases have been shown to play a role in the sorting and incorporation of proteins into secretory vesicles. At the final stage of exocytosis, SNAREs (soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor) and SNARE-associated proteins are believed to mediate the fusion of secretory vesicles at the plasma membrane. There are multiple events that may occur between the budding of secretory vesicles from the Golgi and the fusion of these vesicles at the plasma membrane. The most obvious and best-known event is the transport of secretory vesicles from Golgi to the vicinity of the plasma membrane via microtubules and their associated motors. At the vicinity of the plasma membrane, however, it is not clear how vesicles finally dock and fuse with the plasma membrane. Identification of proteins involved in these events should provide important insights into the mechanisms of this little known stage of the exocytotic pathway. Currently, a protein complex, known as the sec6/8 or the exocyst complex, has been implicated to play a role at this late stage of exocytosis.
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Affiliation(s)
- S Wang
- Department of Cell Biology and Neuroscience, Rutgers University, Nelson Biological Laboratories, 604 Allison Rd, D419, Piscataway, NJ 08854, USA
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38
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Schwarz TL. Transmitter release at the neuromuscular junction. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2006; 75:105-44. [PMID: 17137926 DOI: 10.1016/s0074-7742(06)75006-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Affiliation(s)
- Thomas L Schwarz
- Program in Neurobiology, Children's Hospital and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA
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39
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Anitei M, Ifrim M, Ewart MA, Cowan AE, Carson JH, Bansal R, Pfeiffer SE. A role for Sec8 in oligodendrocyte morphological differentiation. J Cell Sci 2006; 119:807-18. [PMID: 16478790 DOI: 10.1242/jcs.02785] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
In the central nervous system, oligodendrocytes synthesize vast amounts of myelin, a multilamellar membrane wrapped around axons that dramatically enhances nerve transmission. A complex apparatus appears to coordinate trafficking of proteins and lipids during myelin synthesis, but the molecular interactions involved are not well understood. We demonstrate that oligodendrocytes express several key molecules necessary for the targeting of transport vesicles to areas of rapid membrane growth, including the exocyst components Sec8 and Sec6 and the multidomain scaffolding proteins CASK and Mint1. Sec8 overexpression significantly promotes oligodendrocyte morphological differentiation and myelin-like membrane formation in vitro; conversely, siRNA-mediated interference with Sec8 expression inhibits this process, and anti-Sec8 antibody induces a reduction in oligodendrocyte areas. In addition, Sec8 colocalizes, coimmunoprecipitates and cofractionates with the major myelin protein OSP/Claudin11 and with CASK in oligodendrocytes. These results suggest that Sec8 plays a central role in oligodendrocyte membrane formation by regulating the recruitment of vesicles that transport myelin proteins such as OSP/Claudin11 to sites of membrane growth.
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Affiliation(s)
- Mihaela Anitei
- Program of Molecular Biology and Biochemistry, University of Connecticut Medical School, Farmington, CT 06030, USA
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40
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Logan MA, Steele MR, Vetter ML. Expression of synaptic vesicle two-related protein SVOP in the developing nervous system of Xenopus laevis. Dev Dyn 2006; 234:802-7. [PMID: 16217738 DOI: 10.1002/dvdy.20618] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Synaptic vesicle-associated proteins are important regulators of neurotransmitter release at synaptic terminals in mature animals. Some synaptic vesicle-associated proteins are also expressed during development, although their contribution to development is not as clear. Here, we describe the cloning and developmental expression pattern of the Xenopus laevis synaptic vesicle-associated protein SVOP, a gene first identified as an immediate target for proneural basic helix-loop-helix factors. Alignment analysis revealed a high level of identity between the SVOP protein sequences from Xenopus and other vertebrates. In developing Xenopus embryos, SVOP expression is restricted to the nervous system and is first detectable at the mid-neurula stage. As development progresses SVOP becomes broadly expressed throughout the central nervous system. Our observation that SVOP is expressed in the developing Xenopus nervous system suggests that it may be involved in neuron formation, maturation, or neuronal function.
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Affiliation(s)
- Mary A Logan
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA
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41
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Liebl FLW, Chen K, Karr J, Sheng Q, Featherstone DE. Increased synaptic microtubules and altered synapse development in Drosophila sec8 mutants. BMC Biol 2005; 3:27. [PMID: 16351720 PMCID: PMC1326216 DOI: 10.1186/1741-7007-3-27] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2005] [Accepted: 12/13/2005] [Indexed: 02/02/2023] Open
Abstract
Background Sec8 is highly expressed in mammalian nervous systems and has been proposed to play a role in several aspects of neural development and function, including neurite outgrowth, calcium-dependent neurotransmitter secretion, trafficking of ionotropic glutamate receptors and regulation of neuronal microtubule assembly. However, these models have never been tested in vivo. Nervous system development and function have not been described after mutation of sec8 in any organism. Results We identified lethal sec8 mutants in an unbiased forward genetic screen for mutations causing defects in development of glutamatergic Drosophila neuromuscular junctions (NMJs). The Drosophila NMJ is genetically malleable and accessible throughout development to electrophysiology and immunocytochemistry, making it ideal for examination of the sec8 mutant synaptic phenotype. We developed antibodies to Drosophila Sec8 and showed that Sec8 is abundant at the NMJ. In our sec8 null mutants, in which the sec8 gene is specifically deleted, Sec8 immunoreactivity at the NMJ is eliminated but immunoblots reveal substantial maternal contribution in the rest of the animal. Contrary to the hypothesis that Sec8 is required for neurite outgrowth or synaptic terminal growth, immunocytochemical examination revealed that sec8 mutant NMJs developed more branches and presynaptic terminals during larval development, compared to controls. Synaptic electrophysiology showed no evidence that Sec8 is required for basal neurotransmission, though glutamate receptor trafficking was mildly disrupted in sec8 mutants. The most dramatic NMJ phenotype in sec8 mutants was an increase in synaptic microtubule density, which was approximately doubled compared to controls. Conclusion Sec8 is abundant in the Drosophila NMJ. Sec8 is required in vivo for regulation of synaptic microtubule formation, and (probably secondarily) regulation of synaptic growth and glutamate receptor trafficking. We did not find any evidence that Sec8 is required for basal neurotransmission.
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Affiliation(s)
- Faith LW Liebl
- Department of Cell and Structural Biology, University of Illinois at Urbana-Champaign, 601 South Goodwin Avenue, C626, Urbana, IL 61801 USA
| | - Kaiyun Chen
- Department of Biological Sciences, University of Illinois at Chicago, 840 W. Taylor St. (M/C 067), Chicago, IL 60607 USA
| | - Julie Karr
- Department of Biological Sciences, University of Illinois at Chicago, 840 W. Taylor St. (M/C 067), Chicago, IL 60607 USA
| | - Qi Sheng
- Department of Biological Sciences, University of Illinois at Chicago, 840 W. Taylor St. (M/C 067), Chicago, IL 60607 USA
| | - David E Featherstone
- Department of Biological Sciences, University of Illinois at Chicago, 840 W. Taylor St. (M/C 067), Chicago, IL 60607 USA
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42
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Jafar-Nejad H, Andrews HK, Acar M, Bayat V, Wirtz-Peitz F, Mehta SQ, Knoblich JA, Bellen HJ. Sec15, a component of the exocyst, promotes notch signaling during the asymmetric division of Drosophila sensory organ precursors. Dev Cell 2005; 9:351-63. [PMID: 16137928 DOI: 10.1016/j.devcel.2005.06.010] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2005] [Revised: 06/13/2005] [Accepted: 06/30/2005] [Indexed: 01/05/2023]
Abstract
Asymmetric division of sensory organ precursors (SOPs) in Drosophila generates different cell types of the mature sensory organ. In a genetic screen designed to identify novel players in this process, we have isolated a mutation in Drosophila sec15, which encodes a component of the exocyst, an evolutionarily conserved complex implicated in intracellular vesicle transport. sec15(-) sensory organs contain extra neurons at the expense of support cells, a phenotype consistent with loss of Notch signaling. A vesicular compartment containing Notch, Sanpodo, and endocytosed Delta accumulates in basal areas of mutant SOPs. Based on the dynamic traffic of Sec15, its colocalization with the recycling endosomal marker Rab11, and the aberrant distribution of Rab11 in sec15 clones, we propose that a defect in Delta recycling causes cell fate transformation in sec15(-) sensory lineages. Our data indicate that Sec15 mediates a specific vesicle trafficking event to ensure proper neuronal fate specification in Drosophila.
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Affiliation(s)
- Hamed Jafar-Nejad
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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43
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Lim JE, Jin O, Bennett C, Morgan K, Wang F, Trenor CC, Fleming MD, Andrews NC. A mutation in Sec15l1 causes anemia in hemoglobin deficit (hbd) mice. Nat Genet 2005; 37:1270-3. [PMID: 16227995 DOI: 10.1038/ng1659] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2005] [Accepted: 08/09/2005] [Indexed: 11/09/2022]
Abstract
Hemoglobin deficit (hbd) mice carry a spontaneous mutation that impairs erythroid iron assimilation but does not cause other defects. Normal delivery of iron to developing erythroid precursors is highly dependent on the transferrin cycle. Through genetic mapping and complementation experiments, we show that the hbd mutation is an in-frame deletion of a conserved exon of the mouse gene Sec15l1, encoding one of two Sec15 proteins implicated in the mammalian exocyst complex. Sec15l1 is linked to the transferrin cycle through its interaction with Rab11, a GTPase involved in vesicular trafficking. We propose that inactivation of Sec15l1 alters recycling of transferrin cycle endosomes and increases the release of transferrin receptor exocytic vesicles. This in turn decreases erythroid iron uptake. Determining the molecular basis of the hbd phenotype provides new insight into the intricate mechanisms necessary for normal erythroid iron uptake and the function of a mammalian exocyst protein.
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Affiliation(s)
- Jackie E Lim
- Division of Hematology/Oncology, Children's Hospital Boston, Karp Family Research Laboratories RM 8-125, Boston, Massachusetts 02115-5737, USA
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44
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Forrai A, Robb L. The gene trap resource: a treasure trove for hemopoiesis research. Exp Hematol 2005; 33:845-56. [PMID: 16038776 DOI: 10.1016/j.exphem.2005.03.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2005] [Accepted: 03/23/2005] [Indexed: 11/16/2022]
Abstract
The laboratory mouse is an invaluable tool for functional gene discovery because of its genetic malleability and a biological similarity to human systems that facilitates identification of human models of disease. A number of mutagenic technologies are being used to elucidate gene function in the mouse. Gene trapping is an insertional mutagenesis strategy that is being undertaken by multiple research groups, both academic and private, in an effort to introduce mutations across the mouse genome. Large-scale, publicly funded gene trap programs have been initiated in several countries with the International Gene Trap Consortium coordinating certain efforts and resources. We outline the methodology of mammalian gene trapping and how it can be used to identify genes expressed in both primitive and definitive blood cells and to discover hemopoietic regulator genes. Mouse mutants with hematopoietic phenotypes derived using gene trapping are described. The efforts of the large-scale gene trapping consortia have now led to the availability of libraries of mutagenized ES cell clones. The identity of the trapped locus in each of these clones can be identified by sequence-based searching via the world wide web. This resource provides an extraordinary tool for all researchers wishing to use mouse genetics to understand gene function.
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Affiliation(s)
- Ariel Forrai
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
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45
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Wu S, Mehta SQ, Pichaud F, Bellen HJ, Quiocho FA. Sec15 interacts with Rab11 via a novel domain and affects Rab11 localization in vivo. Nat Struct Mol Biol 2005; 12:879-85. [PMID: 16155582 DOI: 10.1038/nsmb987] [Citation(s) in RCA: 203] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Accepted: 08/03/2005] [Indexed: 12/12/2022]
Abstract
Sec15, a component of the exocyst, recognizes vesicle-associated Rab GTPases, helps target transport vesicles to the budding sites in yeast and is thought to recruit other exocyst proteins. Here we report the characterization of a 35-kDa fragment that comprises most of the C-terminal half of Drosophila melanogaster Sec15. This C-terminal domain was found to bind a subset of Rab GTPases, especially Rab11, in a GTP-dependent manner. We also provide evidence that in fly photoreceptors Sec15 colocalizes with Rab11 and that loss of Sec15 affects rhabdomere morphology. Determination of the 2.5-A crystal structure of the C-terminal domain revealed a novel fold consisting of ten alpha-helices equally distributed between two subdomains (N and C subdomains). We show that the C subdomain, mainly via a single helix, is sufficient for Rab binding.
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Affiliation(s)
- Shuya Wu
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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46
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Mehta SQ, Hiesinger PR, Beronja S, Zhai RG, Schulze KL, Verstreken P, Cao Y, Zhou Y, Tepass U, Crair MC, Bellen HJ. Mutations in Drosophila sec15 reveal a function in neuronal targeting for a subset of exocyst components. Neuron 2005; 46:219-32. [PMID: 15848801 DOI: 10.1016/j.neuron.2005.02.029] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2004] [Revised: 10/26/2004] [Accepted: 02/25/2005] [Indexed: 11/23/2022]
Abstract
The exocyst is a complex of proteins originally identified in yeast that has been implicated in polarized secretion. Components of the exocyst have been implicated in neurite outgrowth, cell polarity, and cell viability. We have isolated an exocyst component, sec15, in a screen for genes required for synaptic specificity. Loss of sec15 causes a targeting defect of photoreceptors that coincides with mislocalization of specific cell adhesion and signaling molecules. Additionally, sec15 mutant neurons fail to localize other exocyst members like Sec5 and Sec8, but not Sec6, to neuronal terminals. However, loss of sec15 does not cause cell lethality in contrast to loss of sec5 or sec6. Our data suggest a role of Sec15 in an exocyst-like subcomplex for the targeting and subcellular distribution of specific proteins. The data also show that functions of other exocyst components persist in the absence of sec15, suggesting that different exocyst components have separable functions.
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Affiliation(s)
- Sunil Q Mehta
- Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
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47
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Murthy M, Ranjan R, Denef N, Higashi MEL, Schupbach T, Schwarz TL. Sec6 mutations and the Drosophila exocyst complex. J Cell Sci 2005; 118:1139-50. [PMID: 15728258 DOI: 10.1242/jcs.01644] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To allow a detailed analysis of exocyst function in multicellular organisms, we have generated sec6 mutants in Drosophila. We have used these mutations to compare the phenotypes of sec6 and sec5 in the ovary and nervous system, and we find them to be similar. We also find that Sec5 is mislocalized in sec6 mutants. Additionally, we have generated an epitope-tagged Sec8 that localized with Sec5 on oocyte membranes and was mislocalized in sec5 and sec6 germ-line clones. This construct further revealed a genetic interaction of sec8 and sec5. These data, taken together, provide new information about the organization of the exocyst complex and suggest that Sec5, Sec6 and Sec8 act as a complex, each member dependent on the others for proper localization and function.
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Affiliation(s)
- Mala Murthy
- Division of Neuroscience, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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48
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Strope S, Rivi R, Metzger T, Manova K, Lacy E. Mouse amnionless, which is required for primitive streak assembly,mediates cell-surface localization and endocytic function of cubilin on visceral endoderm and kidney proximal tubules. Development 2004; 131:4787-95. [PMID: 15342463 DOI: 10.1242/dev.01341] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Impaired primitive streak assembly in the mouse amnionless(amn) mutant results in the absence of non-axial trunk mesoderm, a derivative of the middle region of the primitive streak. In addition, the epiblast of amn mutants fails to increase significantly in size after E7.0, indicating that middle primitive streak assembly is mechanistically tied to the growth of the embryo during gastrulation. Amn, a novel transmembrane protein, is expressed exclusively in an extra-embryonic tissue, visceral endoderm (VE), during the early post-implantation stages. We show that Amn is also expressed in kidney proximal tubules (KPT) and intestinal epithelium,which, like the VE, are polarized epithelia specialized for resorption and secretion. To explore whether Amn participates in the development or function of KPT and intestinal epithelia and to gain insight into the function of Amn during gastrulation, we constructed Amn-/- ES cell↔+/+blastocyst chimeras. While chimeras form anatomically normal kidneys and intestine, they exhibit variable, selective proteinuria, a sign of KPT malfunction. In humans, AMN has been genetically connected to Cubilin(CUBN), a multi-ligand scavenger receptor expressed by KPT, intestine and yolk sac. Loss of CUBN, the intestinal intrinsic factor (IF)-vitamin B12 receptor, results in hereditary megaloblastic anemia (MGA1), owing to vitamin B12 malabsorption. The recent report of MGA1 families with mutations in AMN suggests that AMN functions in the same pathway as CUBN. We demonstrate that Cubn is not properly localized to the cell surface in Amn-/- tissues in the embryo and adult mouse, and that adult chimeras exhibit selective proteinuria of Cubn ligands. This study demonstrates that Amn is an essential component of the Cubn receptor complex in vivo and suggests that Amn/Cubn is required for endocytosis/transcytosis of one or more ligands in the VE during gastrulation to coordinate growth and patterning of the embryo. Furthermore, as AMN is apparently not required for gastrulation in humans, the developmental requirements for Amn/Cubn function may not be evolutionarily conserved, possibly reflecting differences between species in the role and organization of extra-embryonic tissues.
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Affiliation(s)
- Sharon Strope
- Molecular Biology Graduate Program, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10021, USA
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49
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Wang S, Liu Y, Adamson CL, Valdez G, Guo W, Hsu SC. The mammalian exocyst, a complex required for exocytosis, inhibits tubulin polymerization. J Biol Chem 2004; 279:35958-66. [PMID: 15205466 DOI: 10.1074/jbc.m313778200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The exocyst is a 734-kDa complex essential for development. Perturbation of its function results in early embryonic lethality. Extensive investigation has revealed that this complex participates in multiple biological processes, including protein synthesis and vesicle/protein targeting to the plasma membrane. In this article we report that the exocyst may also play a role in modulating microtubule dynamics. Using monoclonal antibodies, we observed that endogenous exocyst subunits co-localized with microtubules and mitotic spindles in normal rat kidney cells. To test for a functional relationship between the exocyst complex and microtubules, we established an in vitro exocyst reconstitution assay and studied exocyst effect on microtubule dynamics. We found that the exocyst complex reconstituted from eight recombinant exocyst subunits inhibited tubulin polymerization in vitro. Deletion of exocyst subunit sec5, sec6, sec15, or exo70 diminished its tubulin polymerization inhibition activity. Surprisingly, exocyst subunit exo70 itself was also capable of inhibiting tubulin polymerization, although exocyst complex with exo70 deletion did not lose its activity completely. Overexpression of exo70 in NRK cells resulted in microtubule network disruption and the formation of filopodia-like plasma membrane protrusions. The formation of these membrane protrusions was greatly hampered by stabilizing microtubules with taxol. Overexpression of exo84, an exocyst subunit that did not show tubulin polymerization inhibition activity, did not cause this phenotype. Results shown in this article, along with a previous report that localized microtubule instability induces plasma membrane addition, implicates a novel role for the exocyst in modulating microtubule dynamics underlying exocytosis.
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Affiliation(s)
- Sheng Wang
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey 08854, USA
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50
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Yeaman C, Grindstaff KK, Nelson WJ. Mechanism of recruiting Sec6/8 (exocyst) complex to the apical junctional complex during polarization of epithelial cells. J Cell Sci 2004; 117:559-70. [PMID: 14709721 PMCID: PMC3368615 DOI: 10.1242/jcs.00893] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Sec6/8 (exocyst) complex regulates vesicle delivery and polarized membrane growth in a variety of cells, but mechanisms regulating Sec6/8 localization are unknown. In epithelial cells, Sec6/8 complex is recruited to cell-cell contacts with a mixture of junctional proteins, but then sorts out to the apex of the lateral membrane with components of tight junction and nectin complexes. Sec6/8 complex fractionates in a high molecular mass complex with tight junction proteins and a portion of E-cadherin, and co-immunoprecipitates with cell surface-labeled E-cadherin and nectin-2alpha. Recruitment of Sec6/8 complex to cell-cell contacts can be achieved in fibroblasts when E-cadherin and nectin-2alpha are co-expressed. These results support a model in which localized recruitment of Sec6/8 complex to the plasma membrane by specific cell-cell adhesion complexes defines a site for vesicle delivery and polarized membrane growth during development of epithelial cell polarity.
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Affiliation(s)
- Charles Yeaman
- Department of Molecular and Cellular Physiology, Beckman Center for Molecular and Genetic Medicine, Stanford University School of Medicine, Stanford, CA 94305-5345, USA.
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