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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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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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Inamdar SM, Hsu SC, Yeaman C. Probing Functional Changes in Exocyst Configuration with Monoclonal Antibodies. Front Cell Dev Biol 2016; 4:51. [PMID: 27376061 PMCID: PMC4891948 DOI: 10.3389/fcell.2016.00051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 05/10/2016] [Indexed: 01/19/2023] Open
Abstract
Spatial regulation of exocytosis relies on the exocyst, a hetero-octameric protein complex that tethers vesicles to fusion sites at the plasma membrane. Nevertheless, our understanding of mechanisms regulating exocyst assembly/disassembly, localization, and function are incomplete. Here, we have exploited a panel of anti-Sec6 monoclonal antibodies (mAbs) to probe possible configurational changes accompanying transitions in exocyst function in epithelial MDCK cells. Sec6 is quantitatively associated with Sec8 in high molecular weight complexes, as shown by gel filtration and co-immunoprecipitation studies. We mapped epitopes recognized by more than 20 distinct mAbs to one of six Sec6 segments. Surprisingly, mAbs that bound epitopes in each segment labeled distinct subcellular structures. In general, antibodies to epitopes in N-terminal domains labeled Sec6 in either cytosolic or nuclear pools, whereas those that bound epitopes in C-terminal domains labeled membrane-associated Sec6. In this latter group, we identified antibodies that labeled distinct Sec6 populations at the apical junctional complex, desmosomes, endoplasmic reticulum and vimentin-type intermediate filaments. That each antibody was specific was verified by both Sec6 RNAi and competition with fusion proteins containing each domain. Comparison of non-polarized and polarized cells revealed that many Sec6 epitopes either redistribute or become concealed during epithelial polarization. Transitions in exocyst configurations may be regulated in part by the actions of Ral GTPases, because the exposure of Sec6 C-terminal domain epitopes at the plasma membrane is significantly reduced upon RalA RNAi. To determine whether spatio-temporal changes in epitope accessibility was correlated with differential stability of interactions between Sec6 and other exocyst subunits, we quantified relative amounts of each subunit that co-immunoprecipitated with Sec6 when antibodies to N-terminal or C-terminal epitopes were used. Antibodies to Sec6NT co-precipitated substantially more Sec5, -10, -15, Exo70 and -84 than did those to Sec6CT. In contrast, antibodies to Sec6CT co-precipitated more Sec3 and Sec8 than did those to Sec6NT. These results are consistent with a model in which exocyst activation during periods of rapid membrane expansion is accompanied by molecular rearrangements within the holocomplex or association with accessory proteins, which expose the Sec6 C-terminal domain when the complex is membrane-bound and conceal it when the complex is cytoplasmic.
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Affiliation(s)
- Shivangi M Inamdar
- Molecular and Cellular Biology Program, University of IowaIowa City, IA, USA; Department of Anatomy and Cell Biology, University of IowaIowa City, IA, USA
| | - Shu-Chan Hsu
- Department of Cell Biology and Neuroscience, Rutgers University Piscataway, NJ, USA
| | - Charles Yeaman
- Molecular and Cellular Biology Program, University of IowaIowa City, IA, USA; Department of Anatomy and Cell Biology, University of IowaIowa City, IA, USA
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Mao MG, Li X, Perálvarez-Marín A, Jiang JL, Jiang ZQ, Wen SH, Lü HQ. Transcriptomic analysis and biomarkers (Rag1 and Igμ) for probing the immune system development in Pacific cod, Gadus macrocephalus. FISH & SHELLFISH IMMUNOLOGY 2015; 44:622-632. [PMID: 25842179 DOI: 10.1016/j.fsi.2015.03.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Revised: 03/21/2015] [Accepted: 03/24/2015] [Indexed: 06/04/2023]
Abstract
Mortality (>90%) is a big concern in larval rearing facilities of Pacific cod, Gadus macrocephalus, limiting its culture presently still in the experimental stages. Understanding the immune system development of G. macrocephalus is crucial to optimize the aquaculture of this species, to improve the use of economic resources and to avoid abuse of antibiotics. For the transcriptome analysis, using an Illumina sequencing platform, 61,775,698 raw reads were acquired. After a de novo assembly, 77,561 unigenes were obtained. We have classified functionally these transcripts by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). 27 genes mainly related to hematopoietic or lymphoid organ development and somatic diversification of immune receptors have been reported for the first time in Pacific cod, and 14 Ig heavy chain (μ chain) locuses were assembled using Trinity. Based on our previous achievement, we have chosen Rag1 and Igμ as immune system development biomarkers. Full length cDNA of Rag1 and Igμ as biomarkers were obtained respectively using RACE PCR. Concerning Rag1, the deduced amino acid of Rag1 and protein immunodetection revealed a Rag1 isoform of 69 kDa, significantly different from other fish orthologs, such as Oncorhynchus mykiss (121 kDa). Phylogenetic analysis reveals a unique immune system for the Gadus genre, not exclusive for Atlantic cod, among vertebrates. Meanwhile, full length cDNA of Igμ included an ORF of 1710 bp and the deduced amino acid was composed of a leader peptide, a variable domain, CH1, CH2, Hinge, CH3, CH4 and C-terminus, which was in accordance with most teleost. Absolute quantification PCR revealed that significant expression of Rag1 appeared earlier than Igμ, 61 and 95 dph compared to 95 dph, respectively. Here we report the first transcriptomic analysis of G. macrocephalus as the starting point for genetic research on immune system development towards improving the Pacific cod aquaculture.
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Affiliation(s)
- Ming-Guang Mao
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China
| | - Xing Li
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China
| | - Alejandro Perálvarez-Marín
- Centre d'Estudis en Biofísica, Unitat de Biofísica, Departament de Bioquímica i de Biologia Molecular, Universitat Autònoma de Barcelona, Cerdanyola del Vallés 08193, Spain
| | - Jie-Lan Jiang
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China
| | - Zhi-Qiang Jiang
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China.
| | - Shi-Hui Wen
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China
| | - Hui-Qian Lü
- Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China
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Takahashi S, Kubo K, Waguri S, Yabashi A, Shin HW, Katoh Y, Nakayama K. Rab11 regulates exocytosis of recycling vesicles at the plasma membrane. J Cell Sci 2012; 125:4049-57. [PMID: 22685325 DOI: 10.1242/jcs.102913] [Citation(s) in RCA: 196] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Rab11 is known to associate primarily with perinuclear recycling endosomes and regulate recycling of endocytosed proteins. However, the recycling step in which Rab11 participates remains unknown. We show here that, in addition to causing tubulation of recycling endosomes, Rab11 depletion gives rise to accumulation of recycling carriers containing endocytosed transferrin and transferrin receptor beneath the plasma membrane. We also show that the carriers are transported from perinuclear recycling endosomes to the cell periphery along microtubules. Total internal reflection fluorescence microscopy of cells expressing EGFP-tagged transferrin receptor revealed that Rab11 depletion inhibits tethering and fusion of recycling carriers to the plasma membrane. Depletion of Sec15, which interacts with Rab11, or Exo70, both components of the exocyst tethering complex, leads to essentially the same phenotypes as those of Rab11 depletion. Thus, in addition to its role in recycling processes at perinuclear recycling endosomes, Rab11 is transported along microtubules to the cell periphery through association with recycling carriers, and directly regulates vesicle exocytosis at the plasma membrane in concert with the exocyst.
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Affiliation(s)
- Senye Takahashi
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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Chong YT, Gidda SK, Sanford C, Parkinson J, Mullen RT, Goring DR. Characterization of the Arabidopsis thaliana exocyst complex gene families by phylogenetic, expression profiling, and subcellular localization studies. THE NEW PHYTOLOGIST 2010; 185:401-19. [PMID: 19895414 DOI: 10.1111/j.1469-8137.2009.03070.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
*The exocyst is a complex of eight proteins (Sec3p, Sec5p, Sec6p, Sec8p, Sec10p, Sec15p, Exo70p and Exo84p) involved in tethering vesicles to the plasma membrane during regulated or polarized secretion. Here, the plant exocyst complex was explored in phylogenetic, expression, and subcellular localization studies. *Evolutionary relationships of predicted exocyst subunits were examined in the complete genomes of Arabidopsis thaliana, Oryza sativa, Populus trichocarpa and Physcomitrella patens. Furthermore, detailed expression profiling of the A. thaliana microarray databases was performed and subcellular localization patterns were studied. *Several plant exocyst subunit genes appear to have undergone gene expansion in a common ancestor and subsequent duplication events in independent plant lineages. Expression profiling revealed that the A. thaliana Exo70 gene family exhibits dynamic expression patterns, while the remaining exocyst subunit genes displayed more static profiles. Subcellular localization patterns for A. thaliana exocyst subunits ranged from cytosolic to endosomal compartments (with enrichment in the early endosomes and the trans-Golgi network). Interestingly, two endosomal-localized AtExo70 proteins also recruited other exocyst subunits to these compartments. *Overall subcellular localization patterns were observed that were also found in yeast and animal cells, and this, coupled with the evolutionary relationships, suggests that the exocyst may perform similar conserved functions in plants.
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Affiliation(s)
- Yolanda T Chong
- Department of Cell & Systems Biology and the Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada M5S 3B2
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Zhang XM, Ellis S, Sriratana A, Mitchell CA, Rowe T. Sec15 Is an Effector for the Rab11 GTPase in Mammalian Cells. J Biol Chem 2004; 279:43027-34. [PMID: 15292201 DOI: 10.1074/jbc.m402264200] [Citation(s) in RCA: 207] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rab/Ypt GTPases play key roles in the regulation of vesicular trafficking. They perform most of their functions in a GTP-bound form by interacting with specific downstream effectors. The exocyst is a complex of eight polypeptides involved in constitutive secretion and functions as an effector for multiple Ras-related small GTPases, including the Rab protein Sec4p in yeast. In this study, we have examined the localization and function of the Sec15 exocyst subunit in mammalian cells. Overexpressed Sec15 associated with clusters of tubular/vesicular elements that were concentrated in the perinuclear region. The tubular/vesicular clusters were dispersed throughout the cytoplasm upon treatment with the microtubule-depolymerizing agent nocodazole and were accessible to endocytosed transferrin, but not exocytic cargo (vesicular stomatitis virus glycoprotein). Consistent with these observations, Sec15 colocalized selectively with the recycling endosome marker Rab11 and exhibited a GTP-dependent interaction with the Rab11 GTPase, but not with Rab4, Rab6, or Rab7. These findings provide the first evidence that the exocyst functions as a Rab effector complex in mammalian cells.
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Affiliation(s)
- Xiang-Ming Zhang
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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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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Hsu SC, TerBush D, Abraham M, Guo W. The exocyst complex in polarized exocytosis. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 233:243-65. [PMID: 15037366 DOI: 10.1016/s0074-7696(04)33006-8] [Citation(s) in RCA: 193] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Exocytosis is an essential membrane traffic event mediating the secretion of intracellular protein contents such as hormones and neurotransmitters as well as the incorporation of membrane proteins and lipids to specific domains of the plasma membrane. As a fundamental cell biological process, exocytosis is crucial for cell growth, cell-cell communication, and cell polarity establishment. For most eukaryotic cells exocytosis is polarized. A multiprotein complex, named the exocyst, is required for polarized exocytosis from yeast to mammals. The exocyst consists of eight components: Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84. They are localized to sites of active exocytosis, where they mediate the targeting and tethering of post-Golgi secretory vesicles for subsequent membrane fusion. Here we review the progress made in the understanding of the exocyst and its role in polarized exocytosis.
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Affiliation(s)
- Shu-Chan Hsu
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey 08854, USA
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