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Journal articles on the topic "Vesicle tethering complex exocyst"
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Wiederkehr, Andreas, Johan-Owen De Craene, Susan Ferro-Novick, and Peter Novick. "Functional specialization within a vesicle tethering complex." Journal of Cell Biology 167, no. 5 (December 6, 2004): 875–87. http://dx.doi.org/10.1083/jcb.200408001.
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The exocyst is an octameric protein complex required to tether secretory vesicles to exocytic sites and to retain ER tubules at the apical tip of budded cells. Unlike the other five exocyst genes, SEC3, SEC5, and EXO70 are not essential for growth or secretion when either the upstream activator rab, Sec4p, or the downstream SNARE-binding component, Sec1p, are overproduced. Analysis of the suppressed sec3Δ, sec5Δ, and exo70Δ strains demonstrates that the corresponding proteins confer differential effects on vesicle targeting and ER inheritance. Sec3p and Sec5p are more critical than Exo70p for ER inheritance. Although nonessential under these conditions, Sec3p, Sec5p, and Exo70p are still important for tethering, as in their absence the exocyst is only partially assembled. Sec1p overproduction results in increased SNARE complex levels, indicating a role in assembly or stabilization of SNARE complexes. Furthermore, a fraction of Sec1p can be coprecipitated with the exoycst. Our results suggest that Sec1p couples exocyst-mediated vesicle tethering with SNARE-mediated docking and fusion.
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Luo, Guangzuo, Jian Zhang, and Wei Guo. "The role of Sec3p in secretory vesicle targeting and exocyst complex assembly." Molecular Biology of the Cell 25, no. 23 (November 15, 2014): 3813–22. http://dx.doi.org/10.1091/mbc.e14-04-0907.
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During membrane trafficking, vesicular carriers are transported and tethered to their cognate acceptor compartments before soluble N-ethylmaleimide–sensitive factor attachment protein (SNARE)-mediated membrane fusion. The exocyst complex was believed to target and tether post-Golgi secretory vesicles to the plasma membrane during exocytosis. However, no definitive experimental evidence is available to support this notion. We developed an ectopic targeting assay in yeast in which each of the eight exocyst subunits was expressed on the surface of mitochondria. We find that most of the exocyst subunits were able to recruit the other members of the complex there, and mistargeting of the exocyst led to secretion defects in cells. On the other hand, only the ectopically located Sec3p subunit is capable of recruiting secretory vesicles to mitochondria. Our assay also suggests that both cytosolic diffusion and cytoskeleton-based transport mediate the recruitment of exocyst subunits and secretory vesicles during exocytosis. In addition, the Rab GTPase Sec4p and its guanine nucleotide exchange factor Sec2p regulate the assembly of the exocyst complex. Our study helps to establish the role of the exocyst subunits in tethering and allows the investigation of the mechanisms that regulate vesicle tethering during exocytosis.
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Eckardt, Nancy A. "An Exocyst Vesicle Tethering Complex in Plants." Plant Cell 20, no. 5 (May 2008): 1188. http://dx.doi.org/10.1105/tpc.108.200511.
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Zhang, Weiwei, Lei Huang, Chunhua Zhang, and Christopher J. Staiger. "Arabidopsis myosin XIK interacts with the exocyst complex to facilitate vesicle tethering during exocytosis." Plant Cell 33, no. 7 (April 19, 2021): 2454–78. http://dx.doi.org/10.1093/plcell/koab116.
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Abstract Myosin motors are essential players in secretory vesicle trafficking and exocytosis in yeast and mammalian cells; however, similar roles in plants remain a matter for debate, at least for diffusely growing cells. Here, we demonstrate that Arabidopsis (Arabidopsis thaliana) myosin XIK, via its globular tail domain (GTD), participates in the vesicle tethering step of exocytosis through direct interactions with the exocyst complex. Specifically, myosin XIK GTD bound directly to several exocyst subunits in vitro and functional fluorescently tagged XIK colocalized with multiple exocyst subunits at plasma membrane (PM)-associated stationary foci. Moreover, genetic and pharmacological inhibition of myosin XI activity reduced the rate of appearance and lifetime of stationary exocyst complexes at the PM. By tracking single exocytosis events of cellulose synthase (CESA) complexes with high spatiotemporal resolution imaging and pair-wise colocalization of myosin XIK, exocyst subunits, and CESA6, we demonstrated that XIK associates with secretory vesicles earlier than exocyst and is required for the efficient localization and normal dynamic behavior of exocyst complex at the PM tethering site. This study reveals an important functional role for myosin XI in secretion and provides insights about the dynamic regulation of exocytosis in plants.
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Fendrych, Matyáš, Lukáš Synek, Tamara Pečenková, Edita Janková Drdová, Juraj Sekereš, Riet de Rycke, Moritz K. Nowack, and Viktor Žárský. "Visualization of the exocyst complex dynamics at the plasma membrane of Arabidopsis thaliana." Molecular Biology of the Cell 24, no. 4 (February 15, 2013): 510–20. http://dx.doi.org/10.1091/mbc.e12-06-0492.
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The exocyst complex, an effector of Rho and Rab GTPases, is believed to function as an exocytotic vesicle tether at the plasma membrane before soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) complex formation. Exocyst subunits localize to secretory-active regions of the plasma membrane, exemplified by the outer domain of Arabidopsis root epidermal cells. Using variable-angle epifluorescence microscopy, we visualized the dynamics of exocyst subunits at this domain. The subunits colocalized in defined foci at the plasma membrane, distinct from endocytic sites. Exocyst foci were independent of cytoskeleton, although prolonged actin disruption led to changes in exocyst localization. Exocyst foci partially overlapped with vesicles visualized by VAMP721 v-SNARE, but the majority of the foci represent sites without vesicles, as indicated by electron microscopy and drug treatments, supporting the concept of the exocyst functioning as a dynamic particle. We observed a decrease of SEC6–green fluorescent protein foci in an exo70A1 exocyst mutant. Finally, we documented decreased VAMP721 trafficking to the plasma membrane in exo70A1 and exo84b mutants. Our data support the concept that the exocyst-complex subunits dynamically dock and undock at the plasma membrane to create sites primed for vesicle tethering.
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Morgera, Francesca, Margaret R. Sallah, Michelle L. Dubuke, Pallavi Gandhi, Daniel N. Brewer, Chavela M. Carr, and Mary Munson. "Regulation of exocytosis by the exocyst subunit Sec6 and the SM protein Sec1." Molecular Biology of the Cell 23, no. 2 (January 15, 2012): 337–46. http://dx.doi.org/10.1091/mbc.e11-08-0670.
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Trafficking of protein and lipid cargo through the secretory pathway in eukaryotic cells is mediated by membrane-bound vesicles. Secretory vesicle targeting and fusion require a conserved multisubunit protein complex termed the exocyst, which has been implicated in specific tethering of vesicles to sites of polarized exocytosis. The exocyst is directly involved in regulating soluble N-ethylmaleimide–sensitive factor (NSF) attachment protein receptor (SNARE) complexes and membrane fusion through interactions between the Sec6 subunit and the plasma membrane SNARE protein Sec9. Here we show another facet of Sec6 function—it directly binds Sec1, another SNARE regulator, but of the Sec1/Munc18 family. The Sec6–Sec1 interaction is exclusive of Sec6–Sec9 but compatible with Sec6–exocyst assembly. In contrast, the Sec6–exocyst interaction is incompatible with Sec6–Sec9. Therefore, upon vesicle arrival, Sec6 is proposed to release Sec9 in favor of Sec6–exocyst assembly and to simultaneously recruit Sec1 to sites of secretion for coordinated SNARE complex formation and membrane fusion.
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Riquelme, Meritxell, Erin L. Bredeweg, Olga Callejas-Negrete, Robert W. Roberson, Sarah Ludwig, Alejandro Beltrán-Aguilar, Stephan Seiler, Peter Novick, and Michael Freitag. "The Neurospora crassa exocyst complex tethers Spitzenkörper vesicles to the apical plasma membrane during polarized growth." Molecular Biology of the Cell 25, no. 8 (April 15, 2014): 1312–26. http://dx.doi.org/10.1091/mbc.e13-06-0299.
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Fungal hyphae are among the most highly polarized cells. Hyphal polarized growth is supported by tip-directed transport of secretory vesicles, which accumulate temporarily in a stratified manner in an apical vesicle cluster, the Spitzenkörper. The exocyst complex is required for tethering of secretory vesicles to the apical plasma membrane. We determined that the presence of an octameric exocyst complex is required for the formation of a functional Spitzenkörper and maintenance of regular hyphal growth in Neurospora crassa. Two distinct localization patterns of exocyst subunits at the hyphal tip suggest the dynamic formation of two assemblies. The EXO-70/EXO-84 subunits are found at the peripheral part of the Spitzenkörper, which partially coincides with the outer macrovesicular layer, whereas exocyst components SEC-5, -6, -8, and -15 form a delimited crescent at the apical plasma membrane. Localization of SEC-6 and EXO-70 to the plasma membrane and the Spitzenkörper, respectively, depends on actin and microtubule cytoskeletons. The apical region of exocyst-mediated vesicle fusion, elucidated by the plasma membrane–associated exocyst subunits, indicates the presence of an exocytotic gradient with a tip-high maximum that dissipates gradually toward the subapex, confirming the earlier predictions of the vesicle supply center model for hyphal morphogenesis.
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Medkova, Martina, Y. Ellen France, Jeff Coleman, and Peter Novick. "The rab Exchange Factor Sec2p Reversibly Associates with the Exocyst." Molecular Biology of the Cell 17, no. 6 (June 2006): 2757–69. http://dx.doi.org/10.1091/mbc.e05-10-0917.
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Activation of the rab GTPase, Sec4p, by its exchange factor, Sec2p, is needed for polarized transport of secretory vesicles to exocytic sites and for exocytosis. A small region in the C-terminal half of Sec2p regulates its localization. Loss of this region results in temperature-sensitive growth and the depolarized accumulation of secretory vesicles. Here, we show that Sec2p associates with the exocyst, an octameric effector of Sec4p involved in tethering secretory vesicles to the plasma membrane. Specifically, the exocyst subunit Sec15p directly interacts with Sec2p. This interaction normally occurs on secretory vesicles and serves to couple nucleotide exchange on Sec4p to the recruitment of the Sec4p effector. The mislocalization of Sec2p mutants correlates with dramatically enhanced binding to the exocyst complex. We propose that Sec2p is normally released from the exocyst after vesicle tethering so that it can recycle onto a new round of vesicles. The mislocalization of Sec2p mutants results from a failure to be released from Sec15p, blocking this recycling pathway.
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Lira, Matías, Rodrigo G. Mira, Francisco J. Carvajal, Pedro Zamorano, Nibaldo C. Inestrosa, and Waldo Cerpa. "Glutamatergic Receptor Trafficking and Delivery: Role of the Exocyst Complex." Cells 9, no. 11 (November 3, 2020): 2402. http://dx.doi.org/10.3390/cells9112402.
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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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Fais, Milena, Giovanna Sanna, Manuela Galioto, Thi Thanh Duyen Nguyen, Mai Uyên Thi Trần, Paola Sini, Franco Carta, et al. "LRRK2 Modulates the Exocyst Complex Assembly by Interacting with Sec8." Cells 10, no. 2 (January 20, 2021): 203. http://dx.doi.org/10.3390/cells10020203.
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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.
Dissertations / Theses on the topic "Vesicle tethering complex exocyst"
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Heider, Margaret R. "Investigating the Architecture and Vesicle Tethering Function of the Yeast Exocyst Complex: A Dissertation." eScholarship@UMMS, 2016. https://escholarship.umassmed.edu/gsbs_diss/832.
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The exocyst is an evolutionarily conserved, hetero-octameric protein complex proposed to serve as a multi-subunit tethering complex for exocytosis, although it remains poorly understood at the molecular level. The classification of the exocyst as a multisubunit tethering complex (MTC) stems from its known interacting partners, polarized localization at the plasma membrane, and structural homology to other putative MTCs. The presence of 8 subunits begs the questions: why are so many subunits required for vesicle tethering and what are the contributions of each of these subunits to the overall structure of the complex? Additionally, are subunit or subcomplex dynamics a required feature of exocyst function? We purified endogenous exocyst complexes from Saccharomyces cerevisiae, and showed that the purified complexes are stable and consist of all eight subunits with equal stoichiometry. This conclusion contrasts starkly with current models suggesting that the yeast exocyst tethers vesicles by transient assembly of subcomplexes at sites of exocytosis. Using a combination of biochemical and auxininduced 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 using negative stain electron microscopy; our results indicate that exocyst exists predominantly as an octameric complex in yeast with a stably assembled, elongated structure. This is the first complete structure of a CATCHR family MTC and it differs greatly from the EM structures available for the partial COG and Dsl1 complexes. Future work will be necessary to determine whether exocyst conformational changes are a required feature of vesicle tethering and how such changes are regulated.
These architectural insights are now informing the design of the first in vitro functional assay for the exocyst complex. We developed methodology for attaching fluorescently-labeled exocyst complexes to glass slides and monitoring the capture of purified, endogenous secretory vesicles by single molecule TIRF microscopy. By this approach, we can monitor tethering events in real time and determine the required factors and kinetics of exocytic vesicle tethering.
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Heider, Margaret R. "Investigating the Architecture and Vesicle Tethering Function of the Yeast Exocyst Complex: A Dissertation." eScholarship@UMMS, 2001. http://escholarship.umassmed.edu/gsbs_diss/832.
Full textAbstract:
The exocyst is an evolutionarily conserved, hetero-octameric protein complex proposed to serve as a multi-subunit tethering complex for exocytosis, although it remains poorly understood at the molecular level. The classification of the exocyst as a multisubunit tethering complex (MTC) stems from its known interacting partners, polarized localization at the plasma membrane, and structural homology to other putative MTCs. The presence of 8 subunits begs the questions: why are so many subunits required for vesicle tethering and what are the contributions of each of these subunits to the overall structure of the complex? Additionally, are subunit or subcomplex dynamics a required feature of exocyst function? We purified endogenous exocyst complexes from Saccharomyces cerevisiae, and showed that the purified complexes are stable and consist of all eight subunits with equal stoichiometry. This conclusion contrasts starkly with current models suggesting that the yeast exocyst tethers vesicles by transient assembly of subcomplexes at sites of exocytosis. Using a combination of biochemical and auxininduced 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 using negative stain electron microscopy; our results indicate that exocyst exists predominantly as an octameric complex in yeast with a stably assembled, elongated structure. This is the first complete structure of a CATCHR family MTC and it differs greatly from the EM structures available for the partial COG and Dsl1 complexes. Future work will be necessary to determine whether exocyst conformational changes are a required feature of vesicle tethering and how such changes are regulated.
These architectural insights are now informing the design of the first in vitro functional assay for the exocyst complex. We developed methodology for attaching fluorescently-labeled exocyst complexes to glass slides and monitoring the capture of purified, endogenous secretory vesicles by single molecule TIRF microscopy. By this approach, we can monitor tethering events in real time and determine the required factors and kinetics of exocytic vesicle tethering.
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Ashrafzadeh, Parham. "Exploring Cellular Dynamics : From Vesicle Tethering to Cell Migration." Doctoral thesis, Uppsala universitet, Institutionen för medicinsk cellbiologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-306174.
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Cells in the body communicate with each other in order to cooperate efficiently. This communication is in part achieved by regulated secretion of signaling molecules, which when released from a cell may activate receptors present at the plasma membrane of an adjacent cell. Such signals affect both cell fate and behavior. Dysregulated signaling may lead to disease, including cancer. This thesis is focused on how exocytosis and subsequent activation and trafficking of receptors can be regulated, and what the consequences of this regulation may be for cell migration. Actin filaments are important transport structures for secretory vesicle trafficking. In Paper 1, actin polymerization was shown to induce formation of ordered lipid domains in the plasma membrane. Accordingly, actin filaments may thus create and stabilize specific membrane domains that enable docking of vesicles containing secretory cargo. The RhoGEF FGD5 regulates Cdc42 which can result in cytoskeletal rearrangements. In Paper II, FGD5 was shown to be selectively expressed in blood vessels and required for normal VEGFR2 signaling. FGD5 protected VEGFR2 from proteasome-mediated degradation and was essential for endothelial cells to efficiently respond to chemotactic gradients of VEGFA. The exocyst component EXOC7 is essential for tethering secretory vesicles to the plasma membrane prior to SNARE-mediated fusion. In Paper III, EXOC7 was required for trafficking of VEGFR2-containing vesicles to the inner plasma membrane and VEGFR2 presentation at the cell surface. The ability of tumor cells to escape the primary tumor and establish metastasis is in part dependent on their capacity to migrate. In Paper IV, a method based on time-lapse microscopy and fluorescent dyes was created to analyze single cancer cell migration in mixed cancer cell cultures, and in particular the influence of different types on neighboring cells was assessed. In conclusion, these studies have enhanced our understanding of the mechanisms behind cellular trafficking, and may be applied in the future to develop more specific therapeutics to treat cancer and other diseases associated with abnormal angiogenesis and cellular migration.
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Srivastava, Sweta. "Structural and functional characterisation of the exocyst complex." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275775.
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Masgrau, Fortuny Aina 1986. "The Cytokinetic inhibitors Boi1 and Boi2 are required for activation of the exocyst complex by Rho GTPases." Doctoral thesis, Universitat Pompeu Fabra, 2014. http://hdl.handle.net/10803/318168.
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Cell growth and division requires delivery of new membrane and remodelling factors to
the cell surface. In budding yeast, this involves actin-dependent transport of secretory
vesicles to sites of growth, followed by vesicle fusion to the plasma membrane. Rho-type
GTPases regulate actin polarization and vesicle fusion, but how they signal to diverse
effectors controlling these separate processes is not well understood. Here, we show that
the cortical proteins Boi1 and Boi2 work together with Rho GTPase signalling to
regulate the exocyst, a complex that mediates the tethering of secretory vesicles to the
plasma membrane. Cells lacking both Boi proteins show normal actin polarity but are
defective in bud emergence, bud growth, and fusion of Bgl2-containing vesicles to the
plasma membrane. A gain-of-function version of Exo70, a component of the exocyst
and effector of Cdc42 and Rho3, restores growth of boi1 boi2 mutant cells. Furthermore,
hyperactivation of Rho-GTPase signalling rescues boi defects, suggesting that the
essential function of Boi proteins is to mediate Rho-dependent activation of the exocyst
during cell growth. Finally, we find that Boi1 and Boi2-dependent inhibition of
abscission in cells with chromatin bridges, via their function in the NoCut checkpoint, is
bypassed by expression of gain-of-function EXO70, suggesting the NoCut pathway also
involves regulation of the exocyst.Tant el creixement com la divisió cel·lular requereix el transport de membrana i altres factors a la superfície cel·lular. En cèl·lules de S. cerevisiae, aquests processos necessiten el transport de vesícules de secreció a través dels cables d’actina fins a les zones de creixement actiu, on es fusionen. Les Rho GTPases regulen la polarització de l’actina i la fusió de vesícules, però es desconeix com les GTPases senyalitzen els diversos efectors i com regulen els dos tipus de funcions. En aquest estudi, demostrem que les proteines Boi1 i Boi2 treballen conjuntament amb la senyalització de les Rho GTPases, per tal de regular la funció del complexe “exocyst” que media els contactes inicials entre vesícules de secreció i la membrana plasmàtica. Cèl·lules sense Boi1/2 tenen el citoesquelet d’actina polaritzat, però la cèl·lula filla no pot emergir ni créixer. Un al·lel d’Exo70, una subunitat de l’”exocyst”, que és efector de les GTPases Rho3 i Cdc42, restaura el creixement de cel·lules defectuoses en la funció de Boi1/2. A més a més, l’hiperactivació de GTPases rescata defectes dels mutants de Boi1/2, suggerint que la funció essencial de Boi1 i Boi2 és promoure l’activació de l’”exocyst”, depenent de Rho, durant el creixement cel·lular. Finalment, hem demostrat que la inibició de la divisió cel·lular que controlen via NoCut els efectors Boi1/2 en cèl·lules amb defectes en la segregació de cromosomes, es rescata amb l’al·lel d’Exo70 descrit anteriorment. Aquestes observacions suggereixen que NoCut podria funcionar també a través de la regulació de l’”exocyst”.
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Sabol, Peter. "Úloha vybraných podjednotek komplexu exocyst v odpovědi rostlin na patogena." Doctoral thesis, 2018. http://www.nusl.cz/ntk/nusl-383787.
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In the recent years, there has been a growing number of publications indicating at the involvement of plant secretory pathway in defense against phytopathogens. Specifically, roles of plant exocyst complex have been explored in deeper detail in current research. Yet, exactly how exocyst- mediated exocytosis contributes to secretion of antimicrobials and cell wall-based defense remains unclear. In the presented Dissertation, I provide both experimental evidence and devise further hypotheses on selected exocyst's subunits in plant immune reactions. Particularly, I show that EXO70B1 exocyst subunit interacts with immunity-related RIN4 protein. Cleavage of RIN4 by AvrRpt2 Pseudomonas syringae effector protease releases both RIN4 fragments and EXO70B1 from the plasma membrane when transiently expressed in Nicotiana benthamiana leaves. I speculate on how this might have an implication in regulation of polarized callose deposition. In a co-authored opinion paper, we also hypothesize that EXO70B1-mediated autophagic degradation of TN2 resistance protein prevents its hyperactivation and lesion mimic phenotype development. In addition, in collaboration with my colleagues, I present data on EXO70H4's engagement in PMR4 callose synthase secretion, required for silica deposition. Representing a possible...
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Rawat, Anamika Ashok. "Role komplexu exocyst v růstu a vývoji mechu Physcomitrella patens." Doctoral thesis, 2017. http://www.nusl.cz/ntk/nusl-368882.
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During the course of evolution the early land plants gained extensive innovations that can be seen in modern day plants. The polar growth is an ancient feature of eukaryotic cells and is one of preadaptations that helped plants in successful colonization of land. The polar growth in plants regulates not only the direction of cell expansion and structural properties of cell wall but especially also the orientation of cell division, and is governed by various factors, including the exocyst complex. The exocyst is a well conserved vesicle tethering multi-subunit complex involved in tethering of secretory vesicles to the target membrane. The essential role of the exocyst complex in regulation of various cellular processes in Angiosperms is now well documented. Here I present results of a doctoral project that contributed to phylogenetic analyses of the land plant exocyst complex and especially to uncovering functions of three moss exocyst subunits, namely EXO70 (isoform PpEXO70.3d), SEC6 and SEC3 (isoforms PpSEC3A and PpSEC3B) in the model organism Physcomitrella patens. Various knock-out (KO) mutants in several moss exocyst subunits (Ppexo70.3d, Ppsec6, Ppsec3a and Ppsec3b) show pleiotropic defects directly or indirectly linked to the cell polarity regulation. Cell elongation and differentiation,...
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Ulrychová, Lenka. "Subcelulární lokalizace a úloha komplexu exocyst v savčích buňkách během cytokineze." Master's thesis, 2011. http://www.nusl.cz/ntk/nusl-297605.
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Cytokinesis is the last step of cell cycle when two individual daughter cells separate in process called abscission. This process involves various cellular membrane structures such as endoplasmic reticulum or trans-Golgi network. Moreover, recent investigation has also highlighted an important role of recycling endosomes. The membrane dynamics appear to be important during cell division especially for the formation of new plasma membrane between two daughter cells. Numerous studies suggest that cytokinesis is tightly linked with highly sophisticated transmembrane shuttle that is controlled by Ras-superfamily members such as Rab and Ral proteins. Moreover, during last years has also been revealed the involvement of tethering factors which mediate the fusion of intracellular vesicles with the target plasma membrane. The best known tethering factor is the evolutionary conserved exocyst complex found in all eukaryotic cells. This protein complex is composed of eight subunits (Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70 and Exo84) and was found to interact with members of Ras- superfamily suggesting its involvement in the regulation of cytokinesis. Although the exact mechanism remains shrouded in fog this work suppose the possible interactions among Ras- like proteins and exocyst members which may...
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Jiang, Tiandan T. J. "Roles of Sec5 in the Regulation of Dense-Core Vesicle Secretion in PC12 Cells." Thesis, 2009. http://hdl.handle.net/1807/25705.
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The exocyst is thought to tether secretory vesicles to specific sites on the plasma membrane. As a member of the exocyst, Sec5 is implicated in cell survival and membrane growth in Drosophila. Little is known of the exocyst function in mammals, with previous work suggesting involvement of exocyst in GTP-dependent exocytosis. Using RNA interference, we stably down-regulated Sec5 in PC12 cells. We found that these knockdown cells exhibit decreased GTP- and Ca2+-dependent exocytosis of dense-core vesicles (DCVs), and contain less proportion of docked vesicles. Expression of Sec6/8 is also slightly reduced in Sec5 knockdown cells. Our results suggest that Sec5 is involved in both GTP- and Ca2+-dependent exocytosis, possibly through the regulation of DCV docking. We also established doxycycline-inducible knockdown system for Sec5 in PC12 cells which may be more appropriate to study development-related proteins. Efforts were also made to re-introduce Sec5 into the Sec5 knockdown cells for rescue purposes.
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Kubátová, Zdeňka. "FUNKČNÍ ANALÝZA VYBRANÝCH PODJEDNOTEK EXOCYSTU EXO70 U ROSTLIN." Doctoral thesis, 2020. http://www.nusl.cz/ntk/nusl-434262.
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Arabidopsis thaliana trichomes are large unicellular epidermal outgrowths with a specific development and intriguing shape, which makes them an excellent cell type for our research of cell polarization mecha- nisms. Cell polarity is essential for plant development and the exocyst complex is one of its key regulators. It is an octameric protein complex that mediates polarized exocytosis and growth by targeted tethering of secretory vesicles to the plasma membrane. Its EXO70 subunit functions as a landmark for exocytosis site and physically binds the target membrane through interaction with phospholipids. A remarkable multipli- cation of EXO70 subunit paralogs in land plant genomes is well documented, but the functional diversity of these paralogs remains to be described. In trichomes we revealed the specific role of the EXO70H4 paralog in secondary cell wall deposi- tion, especially in callose synthase delivery. We documented formation of a thick secondary cell wall during the maturation phase of wild type trichome development and a lack of it in the exo70H4 mutant. Moreover, we showed evidence for silica deposition dependency on callose synthesis. Further, we unveiled the formation of apical and basal plasma membrane domains, which differ in their phospholipid compo- sition and ability to bind...