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Academic literature on the topic 'Exocyst Subunit Sec6'
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Journal articles on the topic "Exocyst Subunit Sec6"
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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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Chavez-Dozal, Alba A., Stella M. Bernardo, Hallie S. Rane, and Samuel A. Lee. "Functional Analysis of the Exocyst Subunit Sec15 in Candida albicans." Eukaryotic Cell 14, no. 12 (October 9, 2015): 1228–39. http://dx.doi.org/10.1128/ec.00147-15.
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ABSTRACTIn prior studies of exocyst-mediated late secretion inCandida albicans, we have determined that Sec6 contributes to cell wall integrity, secretion, and filamentation. A conditional mutant lackingSEC6expression exhibits markedly reduced lateral hyphal branching. In addition, lack of the related t-SNAREs Sso2 and Sec9 also leads to defects in secretion and filamentation. To further understand the role of the exocyst in the fundamental processes of polarized secretion and filamentation inC. albicans, we studied the exocyst subunit Sec15. SinceSaccharomyces cerevisiae SEC15is essential for viability, we generated aC. albicansconditional mutant strain in whichSEC15was placed under the control of a tetracycline-regulated promoter. In the repressed state, cell death occurred after 5 h in the tetR-SEC15 strain. Prior to this time point, the tetR-SEC15 mutant was markedly defective in Sap and lipase secretion and demonstrated increased sensitivity to Zymolyase and chitinase. Notably, tetR-SEC15 mutant hyphae were characterized by a hyperbranching phenotype, in direct contrast to strain tetR-SEC6, which had minimal lateral branching. We further studied the localization of the Spitzenkörper, polarisomes, and exocysts in the tetR-SEC15 and tetR-SEC6 mutants during filamentation. Mlc1-GFP (marking the Spitzenkörper), Spa2-GFP (the polarisome), and Exo70-GFP (exocyst) localizations were normal in the tetR-SEC6 mutant, whereas these structures were mislocalized in the tetR-SEC15 mutant. Following alleviation of gene repression by removing doxycycline, first Spitzenkörper, then polarisome, and finally exocyst localizations were recovered sequentially. These results indicate that the exocyst subunits Sec15 and Sec6 have distinct roles in mediating polarized secretion and filamentation inC. albicans.
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Synek, Lukáš, Roman Pleskot, Juraj Sekereš, Natalia Serrano, Nemanja Vukašinović, Jitka Ortmannová, Martina Klejchová, et al. "Plasma membrane phospholipid signature recruits the plant exocyst complex via the EXO70A1 subunit." Proceedings of the National Academy of Sciences 118, no. 36 (September 1, 2021): e2105287118. http://dx.doi.org/10.1073/pnas.2105287118.
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Polarized exocytosis is essential for many vital processes in eukaryotic cells, where secretory vesicles are targeted to distinct plasma membrane domains characterized by their specific lipid–protein composition. Heterooctameric protein complex exocyst facilitates the vesicle tethering to a target membrane and is a principal cell polarity regulator in eukaryotes. The architecture and molecular details of plant exocyst and its membrane recruitment have remained elusive. Here, we show that the plant exocyst consists of two modules formed by SEC3–SEC5–SEC6–SEC8 and SEC10–SEC15–EXO70–EXO84 subunits, respectively, documenting the evolutionarily conserved architecture within eukaryotes. In contrast to yeast and mammals, the two modules are linked by a plant-specific SEC3–EXO70 interaction, and plant EXO70 functionally dominates over SEC3 in the exocyst recruitment to the plasma membrane. Using an interdisciplinary approach, we found that the C-terminal part of EXO70A1, the canonical EXO70 isoform in Arabidopsis, is critical for this process. In contrast to yeast and animal cells, the EXO70A1 interaction with the plasma membrane is mediated by multiple anionic phospholipids uniquely contributing to the plant plasma membrane identity. We identified several evolutionary conserved EXO70 lysine residues and experimentally proved their importance for the EXO70A1–phospholipid interactions. Collectively, our work has uncovered plant-specific features of the exocyst complex and emphasized the importance of the specific protein–lipid code for the recruitment of peripheral membrane proteins.
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Songer, Jennifer A., and Mary Munson. "Sec6p Anchors the Assembled Exocyst Complex at Sites of Secretion." Molecular Biology of the Cell 20, no. 3 (February 2009): 973–82. http://dx.doi.org/10.1091/mbc.e08-09-0968.
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The exocyst is an essential protein complex required for targeting and fusion of secretory vesicles to sites of exocytosis at the plasma membrane. To study the function of the exocyst complex, we performed a structure-based mutational analysis of the Saccharomyces cerevisiae exocyst subunit Sec6p. Two “patches” of highly conserved residues are present on the surface of Sec6p; mutation of either patch does not compromise protein stability. Nevertheless, replacement of SEC6 with the patch mutants results in severe temperature-sensitive growth and secretion defects. At nonpermissive conditions, although trafficking of secretory vesicles to the plasma membrane is unimpaired, none of the exocyst subunits are polarized. This is consistent with data from other exocyst temperature-sensitive mutants, which disrupt the integrity of the complex. Surprisingly, however, these patch mutations result in mislocalized exocyst complexes that remain intact. Our results indicate that assembly and polarization of the exocyst are functionally separable events, and that Sec6p is required to anchor exocyst complexes at sites of secretion.
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Dubuke, Michelle L., Stephanie Maniatis, Scott A. Shaffer, and Mary Munson. "The Exocyst Subunit Sec6 Interacts with Assembled Exocytic SNARE Complexes." Journal of Biological Chemistry 290, no. 47 (October 7, 2015): 28245–56. http://dx.doi.org/10.1074/jbc.m115.673806.
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Chavez-Dozal, Alba A., Stella M. Bernardo, Hallie S. Rane, Gloria Herrera, Vibhati Kulkarny, Jeanette Wagener, Iain Cunningham, Alexandra C. Brand, Neil A. R. Gow, and Samuel A. Lee. "The Candida albicans Exocyst Subunit Sec6 Contributes to Cell Wall Integrity and Is a Determinant of Hyphal Branching." Eukaryotic Cell 14, no. 7 (May 22, 2015): 684–97. http://dx.doi.org/10.1128/ec.00028-15.
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ABSTRACTThe yeast exocyst is a multiprotein complex comprised of eight subunits (Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84) which orchestrates trafficking of exocytic vesicles to specific docking sites on the plasma membrane during polarized secretion. To studySEC6function inCandida albicans, we generated a conditional mutant strain in whichSEC6was placed under the control of a tetracycline-regulated promoter. In the repressed state, the tetR-SEC6mutant strain (denoted tSEC6) was viable for up to 27 h; thus, all phenotypic analyses were performed at 24 h or earlier. Strain tSEC6 under repressing conditions had readily apparent defects in cytokinesis and endocytosis and accumulated both post-Golgi apparatus secretory vesicles and structures suggestive of late endosomes. Strain tSEC6 was markedly defective in secretion of aspartyl proteases and lipases as well as filamentation under repressing conditions. Lack ofSEC6expression resulted in markedly reduced lateral hyphal branching, which requires the establishment of a new axis of polarized secretion. Aberrant localization of chitin at the septum and increased resistance to zymolyase activity were observed, suggesting thatC. albicansSec6 plays an important role in mediating trafficking and delivery of cell wall components. The tSEC6 mutant was also markedly defective in macrophage killing, indicating a role ofSEC6inC. albicansvirulence. Taken together, these studies indicate that the late secretory protein Sec6 is required for polarized secretion, hyphal morphogenesis, and the pathogenesis ofC. albicans.
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Shin, Dong Min, Xiao-Song Zhao, Weizhong Zeng, Marina Mozhayeva, and Shmuel Muallem. "The Mammalian Sec6/8 Complex Interacts with Ca2+ Signaling Complexes and Regulates Their Activity." Journal of Cell Biology 150, no. 5 (September 4, 2000): 1101–12. http://dx.doi.org/10.1083/jcb.150.5.1101.
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The localization of various Ca2+ transport and signaling proteins in secretory cells is highly restricted, resulting in polarized agonist-stimulated Ca2+ waves. In the present work, we examined the possible roles of the Sec6/8 complex or the exocyst in polarized Ca2+ signaling in pancreatic acinar cells. Immunolocalization by confocal microscopy showed that the Sec6/8 complex is excluded from tight junctions and secretory granules in these cells. The Sec6/8 complex was found in at least two cellular compartments, part of the complex showed similar, but not identical, localization with the Golgi apparatus and part of the complex associated with Ca2+ signaling proteins next to the plasma membrane at the apical pole. Accordingly, immunoprecipitation (IP) of Sec8 did not coimmunoprecipitate βCOP, Golgi 58K protein, or mannosidase II, all Golgi-resident proteins. By contrast, IP of Sec8 coimmunoprecipitates Sec6, type 3 inositol 1,4,5-trisphosphate receptors (IP3R3), and the Gβγ subunit of G proteins from pancreatic acinar cell extracts. Furthermore, the anti-Sec8 antibodies coimmunoprecipitate actin, Sec6, the plasma membrane Ca2+ pump, the G protein subunits Gαq and Gβγ, the β1 isoform of phospholipase C, and the ER resident IP3R1 from brain microsomal extracts. Antibodies against the various signaling and Ca2+ transport proteins coimmunoprecipitate Sec8 and the other signaling proteins. Dissociation of actin filaments in the immunoprecipitate had no effect on the interaction between Sec6 and Sec8, but released the actin and dissociated the interaction between the Sec6/8 complex and Ca2+ signaling proteins. Hence, the interaction between the Sec6/8 and Ca2+ signaling complexes is likely mediated by the actin cytoskeleton. The anti-Sec6 and anti-Sec8 antibodies inhibited Ca2+ signaling at a step upstream of Ca2+ release by IP3. Disruption of the actin cytoskeleton with latrunculin B in intact cells resulted in partial translocation of Sec6 and Sec8 from membranes to the cytosol and interfered with propagation of agonist-evoked Ca2+ waves. Our results suggest that the Sec6/8 complex has multiple roles in secretory cells including governing the polarized expression of Ca2+ signaling complexes and regulation of their activity.
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van Gisbergen, Peter A. C., Shu-Zon Wu, Mingqin Chang, Kelli A. Pattavina, Madelaine E. Bartlett, and Magdalena Bezanilla. "An ancient Sec10–formin fusion provides insights into actin-mediated regulation of exocytosis." Journal of Cell Biology 217, no. 3 (January 26, 2018): 945–57. http://dx.doi.org/10.1083/jcb.201705084.
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Exocytosis, facilitated by the exocyst, is fundamentally important for remodeling cell walls and membranes. Here, we analyzed For1F, a novel gene that encodes a fusion of an exocyst subunit (Sec10) and an actin nucleation factor (formin). We showed that the fusion occurred early in moss evolution and has been retained for more than 170 million years. In Physcomitrella patens, For1F is essential, and the expressed protein is a fusion of Sec10 and formin. Reduction of For1F or actin filaments inhibits exocytosis, and For1F dynamically associates with Sec6, another exocyst subunit, in an actin-dependent manner. Complementation experiments demonstrate that constitutive expression of either half of the gene or the paralogous Sec10b rescues loss of For1F, suggesting that fusion of the two domains is not essential, consistent with findings in yeast, where formin and the exocyst are linked noncovalently. Although not essential, the fusion may have had selective advantages and provides a unique opportunity to probe actin regulation of exocytosis.
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Wu, Jiandong, Xiaoyun Tan, Chengyun Wu, Kun Cao, Yan Li, and Yiqun Bao. "Regulation of Cytokinesis by Exocyst Subunit SEC6 and KEULE in Arabidopsis thaliana." Molecular Plant 6, no. 6 (November 2013): 1863–76. http://dx.doi.org/10.1093/mp/sst082.
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Ding, Yu, Juan Wang, John Ho Chun Lai, Vivian Hoi Ling Chan, Xiangfeng Wang, Yi Cai, Xiaoyun Tan, et al. "Exo70E2 is essential for exocyst subunit recruitment and EXPO formation in both plants and animals." Molecular Biology of the Cell 25, no. 3 (February 2014): 412–26. http://dx.doi.org/10.1091/mbc.e13-10-0586.
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In contrast to a single copy of Exo70 in yeast and mammals, the Arabidopsis genome contains 23 paralogues of Exo70 (AtExo70). Using AtExo70E2 and its GFP fusion as probes, we recently identified a novel double-membrane organelle termed exocyst-positive organelle (EXPO) that mediates an unconventional protein secretion in plant cells. Here we further demonstrate that AtExo70E2 is essential for exocyst subunit recruitment and for EXPO formation in both plants and animals. By performing transient expression in Arabidopsis protoplasts, we established that a number of exocyst subunits (especially the members of the Sec family) are unable to be recruited to EXPO in the absence of AtExo70E2. The paralogue AtExo70A1 is unable to substitute for AtExo70E2 in this regard. Fluorescence resonance energy transfer assay and bimolecular fluorescence complementation analyses confirm the interaction between AtExo70E2 and Sec6 and Sec10. AtExo70E2, but not its yeast counterpart, is also capable of inducing EXPO formation in an animal cell line (HEK293A cells). Electron microscopy confirms the presence of double-membraned, EXPO-like structures in HEK293A cells expressing AtExo70E2. Inversely, neither human nor yeast Exo70 homologues cause the formation of EXPO in Arabidopsis protoplasts. These results point to a specific and crucial role for AtExo70E2 in EXPO formation.
Dissertations / Theses on the topic "Exocyst Subunit Sec6"
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Dubuke, Michelle L. "The Exocyst Subunit Sec6 Interacts with Assembled Exocytic Snare Complexes: A Dissertation." eScholarship@UMMS, 2015. https://escholarship.umassmed.edu/gsbs_diss/868.
Full textAbstract:
In eukaryotic cells, membrane-bound vesicles carry cargo between intracellular compartments, to and from the cell surface, and to the extracellular environment. Many conserved families of proteins are required for properly localized vesicle fusion, including the multi-subunit tethering complexes and the SNARE complexes. These protein complexes work together to promote proper vesicle fusion in other trafficking pathways. Contrary to these other pathways, our lab previously suggested that the exocyst subunit Sec6, a component of the exocytosis-specific tethering complex, inhibited Sec9:Sso1 SNARE complex assembly due to interactions in vitro with the SNARE protein Sec9 (Sivaram et al., 2005).
My goal for this project was to test the hypothesis that Sec6 inhibited SNARE complex assembly in vivo. I therefore chose to generate Sec6:Sec9 loss-of-binding mutants, and study their effect both in vitro and in vivo. I identified a patch of residues on Sec9 that, when mutated, are sufficient to disrupt the novel Sec6-SNARE interaction. Additionally, I found that the previous inhibitory role for Sec6 in SNARE assembly was due to a data mis-interpretation; my re-interpretation of the data shows that Sec6 has a mild, if any, inhibitory effect on SNARE assembly. My results suggest a potential positive role for Sec6 in SNARE complex assembly, similar to the role observed for other tether-SNARE interactions.
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Dubuke, Michelle L. "The Exocyst Subunit Sec6 Interacts with Assembled Exocytic Snare Complexes: A Dissertation." eScholarship@UMMS, 2012. http://escholarship.umassmed.edu/gsbs_diss/868.
Full textAbstract:
In eukaryotic cells, membrane-bound vesicles carry cargo between intracellular compartments, to and from the cell surface, and to the extracellular environment. Many conserved families of proteins are required for properly localized vesicle fusion, including the multi-subunit tethering complexes and the SNARE complexes. These protein complexes work together to promote proper vesicle fusion in other trafficking pathways. Contrary to these other pathways, our lab previously suggested that the exocyst subunit Sec6, a component of the exocytosis-specific tethering complex, inhibited Sec9:Sso1 SNARE complex assembly due to interactions in vitro with the SNARE protein Sec9 (Sivaram et al., 2005).
My goal for this project was to test the hypothesis that Sec6 inhibited SNARE complex assembly in vivo. I therefore chose to generate Sec6:Sec9 loss-of-binding mutants, and study their effect both in vitro and in vivo. I identified a patch of residues on Sec9 that, when mutated, are sufficient to disrupt the novel Sec6-SNARE interaction. Additionally, I found that the previous inhibitory role for Sec6 in SNARE assembly was due to a data mis-interpretation; my re-interpretation of the data shows that Sec6 has a mild, if any, inhibitory effect on SNARE assembly. My results suggest a potential positive role for Sec6 in SNARE complex assembly, similar to the role observed for other tether-SNARE interactions.
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Andersen, Nicholas John Yeaman Charles A. "Characterization of mammalian exocyst subunit Sec3." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/327.
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Andersen, Nicholas John. "Characterization of mammalian exocyst subunit Sec3." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/327.
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The Exocyst is a hetero-octameric complex involved in tethering of post-Golgi vesicle transport to sites of membrane expansion. In budding yeast, the Exocyst targets vesicles to bud site resulting in bud emergence and abscission of the daughter cell. Mammalian Exocyst is recruited to developing lateral membranes after cadherin mediated adhesion and then is segregated to adherens junctional complexes (AJC). In polarized epithelia, the Exocyst is required for basal-lateral transport of LDL receptor. Additional Exocyst subunit localizations and functions have been identified. It is not known whether these supplementary roles can be attributed to the Exocyst or other unidentified Exocyst subcomplexes. Sec3, an Exocyst subunit, is hypothesized to be a landmark of polarization in yeast. In polarized epithelia, GFP tagged Sec3 remained cytosolic in polarized epithelia unlike Sec6/8. Sec3-GFP was recruited to lateral membranes only after dual over expression of heterologous GLYT1. Little is known about endogenous mammalian Sec3. Our work suggests Sec3 defines an Exocyst subcomplex that is required for desmosome integrity. Sec3 and additional subunits (Sec6, Sec8, Sec15, Exo70, and Exo84) were present at desmosomes, but Sec3 failed to localize to AJC. Only antibodies to Sec6 and Sec8 labeled AJC. Reduction of Sec3 protein expression resulted in the impairment of desmosome morphology and function with no detrimental effect on adherens junctions. These data suggest the existence of functionally different Exocyst subcomplexes. Sec3-exocyst recruited minus-end directed microtubule motor KifC3 to desmosomes. KifC3 was previously shown to be recruited with a microtubule anchoring complex to basal-lateral membrane. This suggests Sec3 may recruit KifC3 to organize microtubules at desmosomes. This would establish a pathway to efficiently transport newly synthesized basal-lateral cargo. These results suggest a novel mechanism of the Exocyst to regulate post-Golgi vesicular transport and intercellular adhesion.
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Brewer, Daniel Niron. "Elucidation of the Role of the Exocyst Subunit Sec6p in Exocytosis: A Dissertation." eScholarship@UMMS, 2009. https://escholarship.umassmed.edu/gsbs_diss/446.
Full textAbstract:
Trafficking of protein and lipid cargo through the secretory pathway in eukaryotic cells is mediated by membrane-bound vesicles. Secretory vesicles are targeted to sites of exocytosis on the plasma membrane in part by a conserved multi-subunit protein complex termed the exocyst. In addition to tethering vesicles to the plasma membrane, the exocyst complex and components therein may also add a layer of regulation by directly controlling assembly of the SNARE complex, which is required for membrane fusion, as well as other regulatory factors such as Sec1p. In the past, we have shown that Sec6p interacts with Sec9p in vivo and that that interaction retards binary SNARE complex formation in a SNARE assembly assay. Though many interactions have been mapped using in vitro methods, confirming them in vivoand placing them into the context of a complete model that accounts for all observed interactions (and lack of interactions) has proven difficult.
In order to address these problems, I have studied the interactions between Sec6p and other factors involved in exocytosis at the plasma membrane via in vivo methods. My hypothesis was that Sec6p interaction with Sec9p and subsequent inhibition of SNARE complex assembly in vitro was an intermediate state and Sec6p was part of a set of cofactors that accelerated SNARE complex assembly in vivo. To test this hypothesis I showed that the interaction between the plasma membrane t-SNARE Sec9p and the yeast exocyst subunit Sec6p can be observed in vivoand designed point mutations to disrupt that interaction. Interestingly, I also showed that Sec6p:Sec9p interaction involves the free pool of Sec6p rather than the exocyst bound fraction of Sec6p.
Point mutations in the N-terminal domain of Sec6p result in temperature sensitive growth and secretion defects, without loss of Sec6p-Sec9p interaction. However, at the non-permissive temperature, the exocyst subunits Sec5p, Sec10p and Sec15p are mislocalized and are absent from the exocyst complex. The resulting subcomplex, containing Sec3p, Sec8p, Exo70p and Exo84p, remains stably assembled and localized at sites of polarized secretion. This subcomplex is likely due to disruption of interaction between Sec6p and Sec5p, and may be similar to that observed at restrictive temperatures in the sec6-54temperature sensitive mutant.
Additionally, one of the sec6 temperature sensitive mutants displays a loss of binding to the yeast regulatory protein Sec1p. In vitro binding studies indicate a direct interaction between Sec1p and the free pool of the wild-type Sec6p protein, suggesting close interplay between Sec6p and Sec1p in the regulation of SNARE complexes. A coherent model which incorporates all these interactions has continued to be elusive. However, the results I have found do suggest several hypotheses which should prove testable in the future.