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Sci Rep 2020 09 14;10(1):15003. Epub 2020 Sep 14.

Department of Biological Sciences, Mississippi State University, Mississippi State, MS, 39762, USA.

Vesicle and target membrane fusion involves tethering, docking and fusion. The GTPase SECRETORY4 (SEC4) positions the exocyst complex during vesicle membrane tethering, facilitating docking and fusion. Glycine max (soybean) Sec4 functions in the root during its defense against the parasitic nematode Heterodera glycines as it attempts to develop a multinucleate nurse cell (syncytium) serving to nourish the nematode over its 30-day life cycle. Read More

Exp Cell Res 2019 08 7;381(1):94-104. Epub 2019 May 7.

Cytogenetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, 221 005, India.

Sec15, a component of an evolutionarily conserved octomeric exocyst complex, has been identified as an interactor of GTP-bound Rab11 in mammals and Drosophila which shows its role in secretion in yeast and intracellular vesicle transport. Here, we report the expression patterns of Drosophila Sec15 (DSec15) transcript and Sec15 protein during Drosophila development. At early embryonic stages, a profound level of maternally loaded DSec15 transcript and protein is found. Read More

Sci Rep 2017 01 18;7:40909. Epub 2017 Jan 18.

Structural Biology Laboratory, Structural Life Science Division, Synchrotron Radiation Research Organization and Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113-0032, Japan.

The exocyst complex is a heterooctameric protein complex composed of Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70 and Exo84. This complex plays an essential role in trafficking secretory vesicles to the plasma membrane through its interaction with phosphatidylinositol 4,5-bisphosphate and small GTPases. To date, the near-full-length structural information of each subunit has been limited to Exo70, although the C-terminal half structures of Sec6, Sec15 and Exo84 and the structures of the small GTPase-binding domains of Sec3, Sec5 and Exo84 have been reported. Read More

J Cell Biol 2016 09;214(6):691-703

Department of Molecular Medicine, Cornell University, Ithaca, NY 14853

Intracellular trafficking is an essential and conserved eukaryotic process. Rab GTPases are a family of proteins that regulate and provide specificity for discrete membrane trafficking steps by harnessing a nucleotide-bound cycle. Global proteomic screens have revealed many Rab GTPases as phosphoproteins, but the effects of this modification are not well understood. Read More

Sci Rep 2016 05 26;6:26464. Epub 2016 May 26.

Institute of Health Sciences, Anhui University, Hefei 230601, China.

The exocyst plays a crucial role in the targeting of secretory vesicles to the plasma membrane during exocytosis. It has been shown to be involved in diverse cellular processes including yeast budding. However, the mechanism of the exocyst regulating yeast budding has not been fully elucidated. Read More

Mol Biol Cell 2016 Feb 23;27(4):686-701. Epub 2015 Dec 23.

Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093

Sec2p is a guanine nucleotide exchange factor that activates Sec4p, the final Rab GTPase of the yeast secretory pathway. Sec2p is recruited to secretory vesicles by the upstream Rab Ypt32p acting in concert with phosphatidylinositol-4-phosphate (PI(4)P). Sec2p also binds to the Sec4p effector Sec15p, yet Ypt32p and Sec15p compete against each other for binding to Sec2p. Read More

J Cell Sci 2015 Jun 11;128(12):2351-62. Epub 2015 May 11.

Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan

In this study, we elucidated the architectures of two multisubunit complexes, the BBSome and exocyst, through a novel application of fluorescent fusion proteins. By processing lysates from cells co-expressing GFP and RFP fusion proteins for immunoprecipitation with anti-GFP nanobody, protein-protein interactions could be reproducibly visualized by directly observing the immunoprecipitates under a microscope, and evaluated using a microplate reader, without requiring immunoblotting. Using this 'visible' immunoprecipitation (VIP) assay, we mapped binary subunit interactions of the BBSome complex, and determined the hierarchies of up to four subunit interactions. Read More

Biochim Biophys Acta 2015 Jul 30;1848(7):1481-9. Epub 2015 Mar 30.

Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 165 02 Prague, Czech Republic. Electronic address:

The exocytosis is a process of fusion of secretory vesicles with plasma membrane, which plays a prominent role in many crucial cellular processes, e.g. secretion of neurotransmitters, cytokinesis or yeast budding. Read More

Methods Mol Biol 2015 ;1298:85-98

Department of Cellular and Molecular Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.

Rabs are activated by guanine nucleotide exchange proteins, which are in turn controlled by complex regulatory mechanisms. Here we describe several different assays that have been used to delineate the mechanisms by which Sec2p, the exchange factor for the Rab Sec4p, is regulated. These assays assess the interaction of Sec2p with the upstream Rab, Ypt32p, a downstream Sec4p effector, Sec15p, and the lipid, phosphatidylinositol-4-phosphate. Read More

J Cell Biol 2014 Oct;207(1):59-72

Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92130

The exocyst serves to tether secretory vesicles to cortical sites specified by polarity determinants, in preparation for fusion with the plasma membrane. Although most exocyst components are brought to these sites by riding on secretory vesicles as they are actively transported along actin cables, Exo70p displays actin-independent localization to these sites, implying an interaction with a polarity determinant. Here we show that Exo70p directly and specifically binds to the polarity determinant scaffold protein Bem1p. Read More

Mol Biol Cell 2014 Nov 27;25(21):3389-400. Epub 2014 Aug 27.

Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093

Phosphatidylinositol-4-phosphate (PI4P) is produced on both the Golgi and the plasma membrane. Despite extensive vesicular traffic between these compartments, genetic analysis suggests that the two pools of PI4P do not efficiently mix with one another. Several lines of evidence indicate that the PI4P produced on the Golgi is normally incorporated into secretory vesicles, but the fate of that pool has been unclear. Read More

Proc Natl Acad Sci U S A 2013 Dec 18;110(50):19995-20002. Epub 2013 Nov 18.

Department of Cellular and Molecular Medicine and Department of Chemistry and Biochemistry, Biomolecular and Proteomics Mass Spectrometry Facility, University of California, San Diego, La Jolla, CA 92093.

Sec2p is a guanine nucleotide exchange factor that promotes exocytosis by activating the Rab GTPase Sec4p. Sec2p is highly phosphorylated, and we have explored the role of phosphorylation in the regulation of its function. We have identified three phosphosites and demonstrate that phosphorylation regulates the interaction of Sec2p with its binding partners Ypt32p, Sec15p, and phosphatidyl-inositol-4-phosphate. Read More

Curr Biol 2012 Oct 13;22(20):1944-50. Epub 2012 Sep 13.

Program in Molecular Medicine, University of Massachusetts Medical School, Biotech 2, Suite 206, 373 Plantation Street, Worcester, MA 01605, USA.

The recycling endosome localizes to a pericentrosomal region via microtubule-dependent transport. We previously showed that Sec15, an effector of the recycling endosome component, Rab11-GTPase, interacts with the mother centriole appendage protein, centriolin, suggesting an interaction between endosomes and centrosomes. Here we show that the recycling endosome associates with the appendages of the mother (older) centriole. Read More

J Biol Chem 2012 May 19;287(19):15602-9. Epub 2012 Mar 19.

Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.

Primary cilia are microtubule-based solitary membrane projections on the cell surface that play important roles in signaling and development. Recent studies have demonstrated that polarized vesicular trafficking involving the small GTPase Rab8 and its guanine nucleotide exchange factor Rabin8 is essential for primary ciliogenesis. In this study, we show that a highly conserved region of Rabin8 is pivotal for its activation as a guanine nucleotide exchange factor for Rab8. Read More

Dev Cell 2011 Dec;21(6):1156-70

Life Sciences Institute, Department of Cell & Developmental Biology, University of Michigan, Ann Arbor, MI 48109-2216, USA.

Vesicle transport requires four steps: vesicle formation, movement, tethering, and fusion. In yeast, two Rab GTPases, Ypt31/32, are required for post-Golgi vesicle formation. A third Rab GTPase, Sec4, and the exocyst act in tethering and fusion of these vesicles. Read More

Eukaryot Cell 2011 Aug 3;10(8):1082-94. Epub 2011 Jun 3.

Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom.

The Ras-like GTPase Rab11 is implicated in multiple aspects of intracellular transport, including maintenance of plasma membrane composition and cytokinesis. In metazoans, these functions are mediated in part via coiled-coil Rab11-interacting proteins (FIPs) acting as Rab11 effectors. Additional interaction between Rab11 and the exocyst subunit Sec15 connects Rab11 with exocytosis. Read More

Mol Biol Cell 2011 Mar 19;22(6):842-57. Epub 2011 Jan 19.

Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7090, USA.

Lgl family members play an important role in the regulation of cell polarity in eukaryotic cells. The yeast homologues Sro7 and Sro77 are thought to act downstream of the Rab GTPase Sec4 to promote soluble N-ethylmaleimide-sensitive factor adaptor protein receptor (SNARE) function in post-Golgi transport. In this article, we characterize the interaction between Sro7 and the type V myosin Myo2 and show that this interaction is important for two distinct aspects of Sro7 function. Read More

J Cell Sci 2006 Mar 14;119(Pt 5):876-88. Epub 2006 Feb 14.

Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA.

Spatial regulation of the secretory machinery is essential for the formation of a new bud in Saccharomyces cerevisiae. Yet, the mechanisms underlying cross-talk between the secretory and the cell-polarity-establishment machineries have not been fully elucidated. Here, we report that Sec15p, a subunit of the exocyst complex, might provide one line of communication. Read More

Nat Genet 2005 Nov 16;37(11):1270-3. Epub 2005 Oct 16.

Division of Hematology/Oncology, Children's Hospital Boston, Karp Family Research Laboratories RM 8-125, Boston, Massachusetts 02115-5737, USA.

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. Read More

J Biol Chem 2004 Oct 29;279(41):43027-34. Epub 2004 Jul 29.

Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.

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. Read More

J Biol Chem 2003 Jun 28;278(23):20954-60. Epub 2003 Mar 28.

Department of Medicine and the Cell and Molecular Biology Graduate Group, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.

We previously showed that the exocyst complex specifically affected the synthesis and delivery of secretory and basolateral plasma membrane proteins. Significantly, the entire spectrum of secreted proteins was increased when the hSec10 (human Sec10) component of the exocyst complex was overexpressed, suggestive of post-transcriptional regulation (Lipschutz, J. H. Read More

J Biol Chem 2003 Jun 28;278(23):20946-53. Epub 2003 Mar 28.

VTT Biotechnology, P. O. Box 1500, FIN-02044 VTT, Finland.

The exocyst is a conserved protein complex proposed to mediate vesicle tethering at the plasma membrane. Previously, we identified SEB1/SBH1, encoding the beta subunit of the Sec61p ER translocation complex, as a multicopy suppressor of the sec15-1 mutant, defective for one subunit of the exocyst complex. Here we show the functional and physical interaction between components of endoplasmic reticulum translocon and the exocytosis machinery. Read More