Exo-endocytic trafficking and the septin-based diffusion barrier are required for the maintenance of Cdc42p polarization during budding yeast asymmetric growth

Orlando, Kelly; Sun, Xiaoli; Zhang, Jian; Lu, Tu; Yokomizo, Lauren K.; Wang, Puyue; Guo, Wei

doi:10.1091/mbc.e10-06-0484

Cited by 45 publications

(59 citation statements)

References 58 publications

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“…4B). Bem3 association with secretory vesicles was further investigated by using 20-55% Percoll density gradients (Orlando et al, 2011) to resolve the P100 fraction (secretory vesicles, endosomal membranes, Golgi components and portions of plasma membrane) of lysates from the temperature-sensitive strain sec10-2 (accumulates secretory vesicles at restrictive temperatures). Bem3 co-fractionated with the known secretory vesicle marker Bgl2 (Harsay and Bretscher, 1995;He et al, 2007) (Fig.…”

Section: The Bem3 Compartment Contains Both Endocytic and Secretory Mmentioning

confidence: 99%

“…Vesicle trafficking has also been proposed to participate in Cdc42 regulation (Marco et al, 2007;Orlando et al, 2011;Slaughter et al, 2009). Specifically, endocytosis contributes to the polarized distribution of Cdc42 by internalizing molecules that diffuse away from the polar cap (Marco et al, 2007), whereas the recycling and secretory pathway redirects the internalized Cdc42 back to sites of polarized growth, ensuring tight and restricted localization to regions undergoing rapid growth (Orlando et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, endocytosis contributes to the polarized distribution of Cdc42 by internalizing molecules that diffuse away from the polar cap (Marco et al, 2007), whereas the recycling and secretory pathway redirects the internalized Cdc42 back to sites of polarized growth, ensuring tight and restricted localization to regions undergoing rapid growth (Orlando et al, 2011). Although GAPs and GEFs are crucial for Cdc42 signaling control, if and how these proteins are subjected to regulation by vesicle trafficking is unclear.…”

Section: Introductionmentioning

confidence: 99%

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Bem3, a Cdc42 GTPase-Activating Protein, traffics to an intracellular compartment and recruits the secretory Rab GTPase Sec4 to endomembranes

Mukherjee

Sen

Boettner

et al. 2013

Journal of Cell Science

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SummaryCell polarity is essential for many cellular functions including division and cell-fate determination. Although RhoGTPase signaling and vesicle trafficking are both required for the establishment of cell polarity, the mechanisms by which they are coordinated are unclear. Here, we demonstrate that the yeast RhoGAP (GTPase activating protein), Bem3, is targeted to sites of polarized growth by the endocytic and recycling pathways. Specifically, deletion of SLA2 or RCY1 led to mislocalization of Bem3 to depolarized puncta and accumulation in intracellular compartments, respectively. Bem3 partitioned between the plasma membrane and an intracellular membrane-bound compartment. These Bem3-positive structures were polarized towards sites of bud emergence and were mostly observed during the pre-mitotic phase of apical growth. Cell biological and biochemical approaches demonstrated that this intracellular Bem3 compartment contained markers for both the endocytic and secretory pathways, which were reminiscent of the Spitzenkörper present in the hyphal tips of growing fungi. Importantly, Bem3 was not a passive cargo, but recruited the secretory Rab protein, Sec4, to the Bem3-containing compartments. Moreover, Bem3 deletion resulted in less efficient localization of Sec4 to bud tips during early stages of bud emergence. Surprisingly, these effects of Bem3 on Sec4 were independent of its GAP activity, but depended on its ability to efficiently bind endomembranes. This work unveils unsuspected and important details of the relationship between vesicle traffic and elements of the cell polarity machinery: (1) Bem3, a cell polarity and peripherally associated membrane protein, relies on vesicle trafficking to maintain its proper localization; and (2) in turn, Bem3 influences secretory vesicle trafficking.

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Section: The Bem3 Compartment Contains Both Endocytic and Secretory Mmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bem3, a Cdc42 GTPase-Activating Protein, traffics to an intracellular compartment and recruits the secretory Rab GTPase Sec4 to endomembranes

Mukherjee

Sen

Boettner

et al. 2013

Journal of Cell Science

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“…However, it has been found in several cases to act as a barrier to the movement of proteins in the plasma membrane (Caudron and Barral, 2009;Orlando et al, 2011). This seems a probable way in which it would act here, preventing proteins needed for cell wall synthesis from reaching the neck.…”

Section: Introductionmentioning

confidence: 99%

Crosslinks in the cell wall of budding yeast control morphogenesis at the mother–bud neck

Blánco

Reidy

Arroyo

et al. 2012

Journal of Cell Science

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SummaryPrevious work has shown that, in cla4D cells of budding yeast, where septin ring organization is compromised, the chitin ring at the mother-daughter neck becomes essential for prevention of neck widening and for cytokinesis. Here, we show that it is not the chitin ring per se, but its linkage to b(1-3)glucan that is required for control of neck growth. When in a cla4D background, crh1D crh2D mutants, in which the chitin ring is not connected to b(1-3)glucan, grew very slowly and showed wide and growing necks, elongated buds and swollen cells with large vacuoles. A similar behavior was elicited by inhibition of the Crh proteins. This aberrant morphology matched that of cla4D chs3D cells, which have no chitin at the neck. Thus, this is a clear case in which a specific chemical bond between two substances, chitin and glucan, is essential for the control of morphogenesis. This defines a new paradigm, in which chemistry regulates growth.

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“…At cytokinesis, the hourglass structure converts into two rings. Septins at the neck form diffusion barriers that keep the cellular machinery necessary for growth and cytokinesis properly localized (16,18,22,49,50,60). In addition, septins are part of the morphogenesis checkpoint that coordinates nuclear division with bud formation (37).…”

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confidence: 99%

The Septin AspB in Aspergillus nidulans Forms Bars and Filaments and Plays Roles in Growth Emergence and Conidiation

2012

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In yeast, septins form rings at the mother-bud neck and function as diffusion barriers. In animals, septins form filaments that can colocalize with other cytoskeletal elements. In the filamentous fungus Aspergillus nidulans there are five septin genes, aspA (an ortholog of Saccharomyces cerevisiae CDC11), aspB (an ortholog of S. cerevisiae CDC3), aspC (an ortholog of S. cerevisiae CDC12), aspD (an ortholog of S. cerevisiae CDC10), and aspE (found only in filamentous fungi). The aspB gene was previously reported to be the most highly expressed Aspergillus nidulans septin and to be essential. Using improved gene targeting techniques, we found that deletion of aspB is not lethal but results in delayed septation, increased emergence of germ tubes and branches, and greatly reduced conidiation. We also found that AspB-green fluorescent protein (GFP) localizes as rings and collars at septa, branches, and emerging layers of the conidiophore and as bars and filaments in conidia and hyphae. Bars are found in dormant and isotropically expanding conidia and in subapical nongrowing regions of hyphae and display fast movements. Filaments form as the germ tube emerges, localize to hyphal and branch tips, and display slower movements. All visible AspB-GFP structures are retained in ⌬aspD and lost in ⌬aspA and ⌬aspC strains. Interestingly, in the ⌬aspE mutant, AspB-GFP rings, bars, and filaments are visible in early growth, but AspB-GFP rods and filaments disappear after septum formation. AspE orthologs are only found in filamentous fungi, suggesting that this class of septins might be required for stability of septin bars and filaments in highly polar cells. Septins are evolutionarily conserved GTP binding proteins that form complexes and are increasingly viewed as cytoskeletal elements (62). Septins are found in all eukaryotes except higher plants (20,52) and are involved in a variety of cellular processes including cytokinesis, vesicle trafficking, cytoskeleton organization, polarity, and formation of diffusion barriers (35,39,44,53,62). Perhaps, not surprisingly given their roles in such critical processes, septin defects have been associated with many human diseases (29).The septins were first discovered in the budding yeast Saccharomyces cerevisiae as temperature-sensitive cell cycle mutants defective in cytokinesis (31, 41). Early in the yeast cell cycle, septins localize as a cap at the future site of bud emergence. As the bud emerges, septins localize first as a ring at the mother/bud neck and later as an hourglass structure as the bud develops (25,26,37). At cytokinesis, the hourglass structure converts into two rings. Septins at the neck form diffusion barriers that keep the cellular machinery necessary for growth and cytokinesis properly localized (16,18,22,49,50,60). In addition, septins are part of the morphogenesis checkpoint that coordinates nuclear division with bud formation (37).In S. cerevisiae septins organize into hetero-oligomeric octamers that associate end to end to form nonpolar filaments (6). Electron ...

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Exo-endocytic trafficking and the septin-based diffusion barrier are required for the maintenance of Cdc42p polarization during budding yeast asymmetric growth

Abstract: The small GTPase Cdc42p is a master regulator of cell polarity. We analyzed Cdc42p localization using yeast mutants and found that endo-exocytic trafficking and septin-based diffusion barrier synergistically control Cdc42p polarization during asymmetric cell growth.

Cited by 45 publications

References 58 publications

Bem3, a Cdc42 GTPase-Activating Protein, traffics to an intracellular compartment and recruits the secretory Rab GTPase Sec4 to endomembranes

Bem3, a Cdc42 GTPase-Activating Protein, traffics to an intracellular compartment and recruits the secretory Rab GTPase Sec4 to endomembranes

Crosslinks in the cell wall of budding yeast control morphogenesis at the mother–bud neck

The Septin AspB in Aspergillus nidulans Forms Bars and Filaments and Plays Roles in Growth Emergence and Conidiation

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