Subunit Composition, Protein Interactions, and Structures of the Mammalian Brain sec6/8 Complex and Septin Filaments

Hsu, Shu-Chan; Hazuka, Christopher D.; Roth, Robyn; Foletti, Davide; Heuser, John E.; Scheller, Richard H.

doi:10.1016/s0896-6273(00)80493-6

Cited by 323 publications

(332 citation statements)

References 56 publications

(25 reference statements)

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“…These observations indicate that septins might contribute to the process of cell division through a more general role in either directing or enhancing the efficiency and specificity of membrane remodeling [21]. In agreement with a role in membrane synthesis, septins in animal cells associate with components of the secretory apparatus, such as the exocyst complex and a SNARE protein (syntaxin) [22,23]. Moreover, although in many higher cell types septins localize to the site of cytokinesis [2,3] and the metaphase plate [24], a subset of septins is expressed highly in post-mitotic tissues such as brain [25], which indicates that the contribution of septins to cell function is not confined to either cytokinesis or chromosome dynamics.…”

Section: Septin Functionsmentioning

confidence: 85%

Some assembly required: yeast septins provide the instruction manual

Versele

Thorner

2005

Trends in Cell Biology

200

199

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Septins are a family of conserved proteins that form hetero-oligomeric complexes that assemble into filaments. The filaments can be organized into linear arrays, coils, rings and gauzes. They serve as membrane-associated scaffolds and as barriers to demarcate local compartments, especially for the establishment of the septation site for cytokinesis. Studies in budding and fission yeast have revealed many of the protein-protein interactions that govern the formation of multi-septin complexes. GTP binding and phosphorylation direct the polymerization of filaments that is required for septin-collar assembly in budding yeast, whereas a homolog of anillin instructs timely formation of the ring of septin filaments at the medial cortex in fission yeast. These insights should aid understanding of the organization and function of the diverse septin structures in animal cells.

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Section: Septin Functionsmentioning

confidence: 85%

Some assembly required: yeast septins provide the instruction manual

Versele

Thorner

2005

Trends in Cell Biology

200

199

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“…Although there is no known mammalian homolog for Bud4p, a counterpart exists for each septin and exocyst subunit. The mammalian exocyst [Sec6-Sec8 (EXOC3-EXOC4) complex] has been co-purified and immunoprecipitated with septins (Hsu et al, 1996;Hsu et al, 1998;Hsu et al, 1999); like its yeast counterpart, it was found to influence polarized vesicle delivery (Hsu et al, 1999). Mammalian septins were individually identified and implicated in cytokinesis, exocytosis, vesicle-targeting and membrane dynamics (Spiliotis and Nelson, 2006;Beites et al, 1999;Trimble, 1999).…”

Section: Introductionmentioning

confidence: 99%

A dual role for IQGAP1 in regulating exocytosis

Rittmeyer

Daniel

Hsu

et al. 2008

Journal of Cell Science

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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: Introductionmentioning

confidence: 99%

“…For example, considerable evidence suggests that the septins are involved in one or more steps of vesicle trafficking in mammalian cells (Hsu et al, 1998;Beites et al, 1999;Kartmann and Roth, 2001;Dent et al, 2002). In yeast, the septins play roles in bud-site selection, the spatial organization of cell-wall deposition, and the "morphogenesis checkpoint" that couples cell-cycle progression to progress in bud formation Sanders and Herskowitz, 1996;DeMarini et al, 1997;Barral et al, 1999;Shulewitz et al, 1999;Longtine et al, 2000;Schenkman et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

“…In each species examined to date, there are two or more septins that form heterooligomeric complexes to perform their specific functions. Purified septins from yeast, Drosophila, Xenopus, and mammalian cells form filaments of 7-9 nm diameter and of variable length (Field et al, 1996;Frazier et al, 1998;Hsu et al, 1998;Kinoshita et al, 2002;Mendoza et al, 2002).In Saccharomyces cerevisiae, there are seven septin genes, of which five (CDC3, CDC10, CDC11, CDC12, and SHS1/SEP7) are expressed in vegetative cells (Longtine et al, 1996;Carroll et al, 1998;Mino et al, 1998) and two (SPR3 and SPR28) only during sporulation (DeVirgilio et al, 1996;Fares et al, 1996). The five vegetatively expressed septins have identical localization patterns throughout the cell cycle.…”

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confidence: 99%

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The Role of Cdc42p GTPase-activating Proteins in Assembly of the Septin Ring in Yeast

Caviston

Longtine

Pringle

et al. 2003

MBoC

227

281

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The septins are a conserved family of GTP-binding, filament-forming proteins. In the yeast Saccharomyces cerevisiae, the septins form a ring at the mother-bud neck that appears to function primarily by serving as a scaffold for the recruitment of other proteins to the neck, where they participate in cytokinesis and a variety of other processes. Formation of the septin ring depends on the Rho-type GTPase Cdc42p but appears to be independent of the actin cytoskeleton. In this study, we investigated further the mechanisms of septin-ring formation. Fluorescence-recovery-after-photobleaching (FRAP) experiments indicated that the initial septin structure at the presumptive bud site is labile (exchanges subunits freely) but that it is converted into a stable ring as the bud emerges. Mutants carrying the cdc42 V36G allele or lacking two or all three of the known Cdc42p GTPase-activating proteins (GAPs: Bem3p, Rga1p, and Rga2p) could recruit the septins to the cell cortex but were blocked or delayed in forming a normal septin ring and had accompanying morphogenetic defects. These phenotypes were dramatically enhanced in mutants that were also defective in Cla4p or Gin4p, two protein kinases previously shown to be important for normal septin-ring formation. The Cdc42p GAPs colocalized with the septins both early and late in the cell cycle, and overexpression of the GAPs could suppress the septin-organization and morphogenetic defects of temperature-sensitive septin mutants. Taken together, the data suggest that formation of the mature septin ring is a process that consists of at least two distinguishable steps, recruitment of the septin proteins to the presumptive bud site and their assembly into the stable septin ring. Both steps appear to depend on Cdc42p, whereas the Cdc42p GAPs and the other proteins known to promote normal septin-ring formation appear to function in a partially redundant manner in the assembly step. In addition, because the eventual formation of a normal septin ring in a cdc42 V36G or GAP mutant was invariably accompanied by a switch from an abnormally elongated to a more normal bud morphology distal to the ring, it appears that the septin ring plays a direct role in determining the pattern of bud growth. INTRODUCTIONThe septin family of proteins was first recognized in yeast and now appears to be ubiquitous in fungi and animals, although not in plants (Longtine et al., 1996;Field and Kellogg, 1999;Trimble, 1999;Nguyen et al., 2000;Momany et al., 2001;Macara et al., 2002). Typical septins have a variable N-terminal region, a conserved core that includes the elements of a GTP-binding site, and a variable C-terminal region that (in all but a few cases) includes a predicted coiled-coil domain. In each species examined to date, there are two or more septins that form heterooligomeric complexes to perform their specific functions. Purified septins from yeast, Drosophila, Xenopus, and mammalian cells form filaments of 7-9 nm diameter and of variable length (Field et al., 1996;Frazier et al., 1998;Hsu et al...

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Subunit Composition, Protein Interactions, and Structures of the Mammalian Brain sec6/8 Complex and Septin Filaments

Cited by 323 publications

References 56 publications

Some assembly required: yeast septins provide the instruction manual

Some assembly required: yeast septins provide the instruction manual

A dual role for IQGAP1 in regulating exocytosis

The Role of Cdc42p GTPase-activating Proteins in Assembly of the Septin Ring in Yeast

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