Ral GTPases Regulate Exocyst Assembly through Dual Subunit Interactions

Moskalenko, Serge A.; Tong, Chao; Rossé, Carine; Mirey, Gladys; Formstecher, Étienne; Daviet, Laurent; Camonis, Jacques; White, Michael A.

doi:10.1074/jbc.m308702200

Cited by 218 publications

(283 citation statements)

References 27 publications

(50 reference statements)

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“…Similarly the exocyst has been implicated in tethering and fusion of Glut4-containing vesicles in 3T3-L1 adipocytes (Inoue et al, 2003;Ewart et al, 2005;Tsuboi et al, 2005). It is possible that other exocyst components also interact with phospholipids (Moskalenko et al, 2003). However, specific disruption of Exo70-PM interaction is sufficient to block exocytosis in mammalian cells.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, Exo70 primarily functions at the early stages of the yeast cell cycle, suggesting a temporal control of Exo70 function (He et al, 2007). In mammalian cells, growth factor signaling involving small GTPases may mediate the subunits assembly, translocation of the exocyst from intracellular compartments to, or activation of the exocyst at, the PM (Sugihara et al, 2002;Moskalenko et al, 2002Moskalenko et al, , 2003Inoue et al, 2003;Takaya et al, 2004;Zuo et al, 2006). Future work will be focused on the identification and characterization of proteins that temporally and/or spatially regulate Exo70 and other exocyst components using different eukaryotic systems.…”

Section: Discussionmentioning

confidence: 99%

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Phosphatidylinositol 4,5-Bisphosphate Mediates the Targeting of the Exocyst to the Plasma Membrane for Exocytosis in Mammalian Cells

Liu

Zuo

Peng

et al. 2007

MBoC

193

248

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The exocyst is an evolutionarily conserved octameric protein complex that tethers post-Golgi secretory vesicles at the plasma membrane for exocytosis. To elucidate the mechanism of vesicle tethering, it is important to understand how the exocyst physically associates with the plasma membrane (PM). In this study, we report that the mammalian exocyst subunit Exo70 associates with the PM through its direct interaction with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ). Furthermore, we have identified key conserved residues at the C-terminus of Exo70 that are crucial for the interaction of Exo70 with PI(4,5)P 2 . Disrupting Exo70-PI(4,5)P 2 interaction abolished the membrane association of Exo70. We have also found that wild-type Exo70 but not the PI(4,5)P 2 -binding-deficient Exo70 mutant is capable of recruiting other exocyst components to the PM. Using the ts045 vesicular stomatitis virus glycoprotein trafficking assay, we demonstrate that Exo70-PI(4,5)P 2 interaction is critical for the docking and fusion of post-Golgi secretory vesicles, but not for their transport to the PM. INTRODUCTIONExocytosis is important for a variety of cellular functions, ranging from the release of hormones to the incorporation of membrane proteins for cell growth and morphogenesis. The late stage of exocytosis is a multistep process that includes directional transport, tethering, docking, and fusion of postGolgi secretory vesicles with the plasma membrane (PM). The tethering step, defined as the initial contact of secretory vesicles with the PM before SNARE-mediated docking and fusion (Pfeffer, 1999;Guo et al., 2000;Waters and Hughson, 2000;Whyte and Munro, 2002), is mediated by the exocyst, an evolutionarily conserved octameric complex composed of Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84 (for review, see Guo et al., 2000;Hsu et al., 2004;Munson and Novick, 2006;Wang and Hsu, 2006). In budding yeast, the exocyst components localize to the growing end of the daughter cell ("bud"), where active exocytosis and membrane addition take place (TerBush and Novick, 1995;Finger et al., 1998, Guo et al., 1999. This localization pattern contrasts that of the membrane fusion machine, the t-SNAREs, which are evenly distributed along both the mother and daughter cell membrane (Brennwald et al., 1994). In mammalian cells, the exocyst components were found in the cytosol, recycling endosomes and trans-Golgi network Fö lsch et al., 2003;Ang et al., 2004;Langevin et al., 2005). However, they are recruited to the PM during a number of cellular processes. For example, in epithelial cells, the exocyst is recruited to the adherens junction region upon cell-cell contact, where it mediates protein and membrane addition at the basolateral domain (Grindstaff et al., 1998;Yeaman et al., 2001); in developing neurons, the exocyst is localized to the growing neurites, where it mediates membrane expansion (Hazuka et al., 1999;Vega and Hsu, 2001); during cell migration, the exocyst is recruited to the leading edges of the PM (Rosse et al., 2006;...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Phosphatidylinositol 4,5-Bisphosphate Mediates the Targeting of the Exocyst to the Plasma Membrane for Exocytosis in Mammalian Cells

Liu

Zuo

Peng

et al. 2007

MBoC

193

248

View full text Add to dashboard Cite

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“…Knockdown of the exocyst components Sec5 and Sec6 inhibited this effect. In polarized cells, Ral GTPases regulate basolateral targeting through an interaction with the exocyst complex (Moskalenko et al, 2003). Interestingly, exocyst recruitment to focal complexes and exocystmediated migration and invasion requires Ral GTPases, as restoring small interfering RNA knockdown cells with a Sec5 construct impaired for interaction with RalA did not restore these effects.…”

Section: Hijacking Of the Domain-identity Machinerymentioning

confidence: 99%

The epithelial polarity program: machineries involved and their hijacking by cancer

2008

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The Epithelial Polarity Program (EPP) adapts and integrates three ancient cellular machineries to construct an epithelial cell. The polarized trafficking machinery adapts the cytoskeleton and ancestral secretory and endocytic machineries to the task of sorting and delivering different plasma membrane (PM) proteins to apical and basolateral surface domains. The domain-identity machinery builds a tight junctional fence (TJ) between apical and basolateral PM domains and adapts ancient polarity proteins and polarity lipids on the cytoplasmic side of the PM, which have evolved to perform a diversity of polarity tasks across cells and species, to provide 'identity' to each epithelial PM domain. The 3D organization machinery utilizes adhesion molecules as positional sensors of other epithelial cells and the basement membrane and small GTPases as integrators of positional information with the activities of the domain-identity and polarized trafficking machineries. Cancer is a disease mainly of epithelial cells (90% of human cancers are carcinomas that derive from epithelial cells) that hijacks the EPP machineries, resulting in loss of epithelial polarity, which often correlates in extent with the aggressiveness of the tumor. Here, we review how the EPP integrates its three machineries and the strategies used by cancer to hijack them.

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“…The latter promotes exchange of GTP for GDP on two Ras-related GTPases, RalA and RalB. The Ral GTPases have been implicated in many of the downstream effects of Ras, including cell transformation, activation of transcription factors, and intracellular trafficking [43][44][45].…”

Section: Ras-induced Vacuolation Is Not Blocked By Coexpression With mentioning

confidence: 99%

Activated Ras induces cytoplasmic vacuolation and non-apoptotic death in glioblastoma cells via novel effector pathways

Kaul

Overmeyer

Maltese

2007

Cellular Signalling

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Expression of activated H-Ras induces a unique form of non-apoptotic cell death in human glioblastoma cells and other specific tumor cell lines. The major cytopathological features of this form of death are the accumulation of large phase-lucent, LAMP1-positive, cytoplasmic vacuoles and increased autophagic activity. In this study we sought to determine if induction of cytoplasmic vacuolation a) depends on Ras farnesylation, b) is specific to H-Ras, and c) is mediated by signaling through the major known Ras effector pathways. We find that the unusual effects of activated H-Ras depend on farnesylation and membrane association of the GTPase. Both H-Ras(G12V) and K-Ras4B (G12V) stimulate vacuolation, but activated forms of Cdc42 and RhoA do not. Amino acid substitutions in the Ras effector domain, which are known to selectively impair its interactions with Raf kinase, class-I phosphatidylinositide 3-kinase (PI3K), or Ral nucleotide exchange factors, initially pointed to Raf as a possible mediator of cell vacuolation. However, the MEK inhibitor, PD98059, did not block the induction of vacuoles, and constitutively active Raf-Caax did not mimic the effects of Ras(G12V). Introduction of normal PTEN together with H-Ras(G12V) into U251 glioblastoma cells reduced the PI3K-dependent activation of Akt, but had no effect on vacuolation. Finally, co-expression of H-Ras(G12V) with a dominant-negative form of RalA did not suppress vacuolation. Taken together, the observations indicate that Ras activates non-conventional and perhaps unique effector pathways to induce cytoplasmic vacuolation in glioblastoma cells. Identification of the relevant signaling pathways may uncover specific molecular targets that can be manipulated to activate non-apoptotic cell death in this type of cancer.

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Ral GTPases Regulate Exocyst Assembly through Dual Subunit Interactions

Cited by 218 publications

References 27 publications

Phosphatidylinositol 4,5-Bisphosphate Mediates the Targeting of the Exocyst to the Plasma Membrane for Exocytosis in Mammalian Cells

Phosphatidylinositol 4,5-Bisphosphate Mediates the Targeting of the Exocyst to the Plasma Membrane for Exocytosis in Mammalian Cells

The epithelial polarity program: machineries involved and their hijacking by cancer

Activated Ras induces cytoplasmic vacuolation and non-apoptotic death in glioblastoma cells via novel effector pathways

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