The β Subunit of the Sec61p Endoplasmic Reticulum Translocon Interacts with the Exocyst Complex in Saccharomyces cerevisiae

Toikkanen, Jaana; Miller, Karl Juha; Söderlund, Hans; Jäntti, Jussi; Keränen, Sirkka

doi:10.1074/jbc.m213111200

Cited by 80 publications

(97 citation statements)

References 67 publications

(84 reference statements)

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“…8), and at the plasma membrane, Fig. S2A), similar to mammalian and yeast exocysts (Lipschutz et al, 2003;Toikkanen et al, 2003). These findings support the idea of involvement of these protein complexes in a positive-feedback loop for exocytosis.…”

Section: Iqgap1 Links the Exocyst-septin Complex With Cdc42 Signalingsupporting

confidence: 79%

“…The recent discovery that the vesicle-tethering exocyst has a conserved role in communicating with the ER-translocon complex (Lipschutz et al, 2003;Toikkanen et al, 2003) lends credence to such an idea. Furthermore, upon an ExPASy proteomic server (http://br.expasy.org/) search for motifs on IQGAP1, we identified an ER membrane-retention signal (KFYG) on the extreme Cterminus.…”

Section: Iqgap1 Localizes and Associates With Sites Of Protein Synthementioning

confidence: 99%

“…Recently, genetic and biochemical evidence have shown that both yeast and mammalian exocysts communicate with the ER-translocon via an interaction with the Sec61␤ subunit (Lipschutz et al, 2003;Toikkanen et al, 2003), suggesting a role in protein synthesis/translocation events.…”

Section: Introductionmentioning

confidence: 99%

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A dual role for IQGAP1 in regulating exocytosis

Rittmeyer

Daniel

Hsu

et al. 2008

Journal of Cell Science

173

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Polarized secretion is a tightly regulated event generated by conserved, asymmetrically localized multiprotein complexes, and the mechanism(s) underlying its temporal and spatial regulation are only beginning to emerge. Although yeast Iqg1p has been identified as a positional marker linking polarity and exocytosis cues, studies on its mammalian counterpart, IQGAP1, have focused on its role in organizing cytoskeletal architecture, for which the underlying mechanism is unclear. Here, we report that IQGAP1 associates and co-localizes with the exocyst-septin complex, and influences the localization of the exocyst and the organization of septin. We further show that activation of CDC42 GTPase abolishes this association and inhibits secretion in pancreatic β-cells. Whereas the N-terminus of IQGAP1 binds the exocyst-septin complex, enhances secretion and abrogates the inhibition caused by CDC42 or the depletion of IQGAP1, the C-terminus, which binds CDC42, inhibits secretion. Pulse-chase experiments indicate that IQGAP1 influences protein-synthesis rates, thus regulating exocytosis. We propose and discuss a model in which IQGAP1 serves as a conformational switch to regulate exocytosis.

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Section: Iqgap1 Links the Exocyst-septin Complex With Cdc42 Signalingsupporting

confidence: 79%

Section: Iqgap1 Localizes and Associates With Sites Of Protein Synthementioning

confidence: 99%

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A dual role for IQGAP1 in regulating exocytosis

Rittmeyer

Daniel

Hsu

et al. 2008

Journal of Cell Science

173

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“…Anti-Sec9p-CT antibodies have been described previously (Brennwald et al, 1994). AntiSec4p (R232), Sec15p (R233), Sso1/2p (K8), Sso1p (K6916), Sso2p (K6906), Mso1p (R285), tubulin, and Ady3p antibodies have been described previously (Aalto et al, 1997;Moreno-Borchart et al, 2001;Jantti et al, 2002;Toikkanen et al, 2003). Anti-Sec8p antibody was obtained from Wei Guo (University of Pennsylvania, Philadelphia, PA).…”

mentioning

confidence: 99%

Molecular Interactions Position Mso1p, a Novel PTB Domain Homologue, in the Interface of the Exocyst Complex and the Exocytic SNARE Machinery in Yeast

Knop

Miller

Mazza

et al. 2005

MBoC

Self Cite

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In this study, we have analyzed the association of the Sec1p interacting protein Mso1p with the membrane fusion machinery in yeast. We show that Mso1p is essential for vesicle fusion during prospore membrane formation. Green fluorescent protein-tagged Mso1p localizes to the sites of exocytosis and at the site of prospore membrane formation. In vivo and in vitro experiments identified a short amino-terminal sequence in Mso1p that mediates its interaction with Sec1p and is needed for vesicle fusion. A point mutation, T47A, within the Sec1p-binding domain abolishes Mso1p functionality in vivo, and mso1T47A mutant cells display specific genetic interactions with sec1 mutants. Mso1p coimmunoprecipitates with Sec1p, Sso1/2p, Snc1/2p, Sec9p, and the exocyst complex subunit Sec15p. In sec4-8 and SEC4I133 mutant cells, association of Mso1p with Sso1/2p, Snc1/2p, and Sec9p is affected, whereas interaction with Sec1p persists. Furthermore, in SEC4I133 cells the dominant negative Sec4I133p coimmunoprecipitates with Mso1p-Sec1p complex. Finally, we identify Mso1p as a homologue of the PTB binding domain of the mammalian Sec1p binding Mint proteins.These results position Mso1p in the interface of the exocyst complex, Sec4p, and the SNARE machinery, and reveal a novel layer of molecular conservation in the exocytosis machinery. INTRODUCTIONEvolutionarily conserved molecular machinery regulates transport vesicle targeting, tethering, and fusion in eukaryotic cells. In yeast Saccharomyces cerevisiae this machinery involves the activity of the eight-subunit (Sec3p, Sec5p, Sec6p, Sec8p, Sec10p, Sec15p, Exo70p, and Exo84p) tethering complex, the exocyst, a rab family small GTPase Sec4p, and the exocytic SNARE complex (Snc1/2p, Sec9p, and Sso1/2p) thought to drive the actual lipid bilayer fusion . The exocyst subunit Sec15p has been shown to act as an effector for Sec4p (Guo et al., 1999). In addition, sec4-8 mutant cells are defective in Snc1/2p-Sec9p-Sso1/2p SNARE complex assembly (Carr et al., 1999). Despite these and numerous other studies, the regulatory mechanisms for SNARE complex formation are still poorly understood. The Sec1/Munc18 (SM) protein family members represent central regulators of SNARE complex function. These proteins perform an essential, albeit currently poorly understood function in SNARE complex regulation (Gallwitz and Jahn, 2003;Toonen and Verhage, 2003;Kauppi et al., 2004).Yeast S. cerevisiae possesses four Sec1p-family proteins: Sec1p mediates vesicle fusion at the plasma membrane (Novick et al., 1981;Carr et al., 1999), Sly1p mediates vesicle fusion at the endoplasmic reticulum-Golgi interface (Ossig et al., 1991), Vps33p is required for endosome to vacuole transport and vacuole maintenance (Banta et al., 1990), and Vps45p mediates Golgi-to-vacuole transport (Piper et al., 1994;Cowles et al., 1994). Sec1p is the closest homologue of the mammalian Munc18-1 that has been shown to associate with syntaxin 1 and to regulate the syntaxin 1-synaptobrevin-SNAP-25 SNARE complex assembly (Misura et al., 2000;Kaup...

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“…23) The resulting Sec61β/exocyst complexes upregulate post-transcriptional synthesis and delivery of secretory and basolateral membrane proteins. [24][25][26] Given that claudins are basolateral membrane proteins, they may also be subjected to Sec61β-mediated upregulation.…”

mentioning

confidence: 99%

Sec61β Regulates Barrier Functions of Tight Junction through Expression of Claudin-4 in Madin–Darby Canine Kidney Cells

Washiyama

Koizumi

Fujii

et al. 2014

Biological & Pharmaceutical Bulletin

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Sec61β is the β subunit of the Sec61 translocon and is responsible for expression and delivery of basolateral membrane proteins, including claudins, major constituents of tight junction (TJ). In the present study, the effect of Sec61β overexpression on TJ barrier functions in Madin-Darby canine kidney (MDCK) cells were investigated by monitoring transepithelial electrical resistance (TER) and the expression and distribution of claudins. We adopted the time required by TER to reach 50% (T 1/2 ) as a measure of TJ modulation rate. Sec61β overexpression increased TER by post-transcriptionally upregulating claudin-4 expression and resulted in increased TER. Sec61β overexpression increased TJ modulation rates (lower T 1/2 ), in conjunction with enhanced delivery of claudin-4 from and to plasma membranes. Marked co-distribution and indirect association of claudin-4 with Sec61β were observed, contributing to the enhanced delivery of claudin-4. Thus, Sec61β may be a novel TJ modulation target, including barrier function and modulation rates for drug delivery systems.

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The β Subunit of the Sec61p Endoplasmic Reticulum Translocon Interacts with the Exocyst Complex in Saccharomyces cerevisiae

Cited by 80 publications

References 67 publications

A dual role for IQGAP1 in regulating exocytosis

A dual role for IQGAP1 in regulating exocytosis

Molecular Interactions Position Mso1p, a Novel PTB Domain Homologue, in the Interface of the Exocyst Complex and the Exocytic SNARE Machinery in Yeast

Sec61β Regulates Barrier Functions of Tight Junction through Expression of Claudin-4 in Madin–Darby Canine Kidney Cells

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