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Kang PJ, Miller KE, Guegueniat J, Beven L, Park HO. The shared role of the Rsr1 GTPase and Gic1/Gic2 in Cdc42 polarization. Mol Biol Cell 2018; 29:2359-2369. [PMID: 30091649 PMCID: PMC6233053 DOI: 10.1091/mbc.e18-02-0145] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The Cdc42 GTPase plays a central role in polarity development in many species. In budding yeast, Cdc42 is essential for polarized growth at the proper site and also for spontaneous cell polarization in the absence of spatial cues. Cdc42 polarization is critical for multiple events in the G1 phase prior to bud emergence, including bud-site assembly, polarization of the actin cytoskeleton, and septin filament assembly to form a ring at the new bud site. Yet the mechanism by which Cdc42 polarizes is not fully understood. Here we report that biphasic Cdc42 polarization in the G1 phase is coupled to stepwise assembly of the septin ring for bud emergence. We show that the Rsr1 GTPase shares a partially redundant role with Gic1 and Gic2, two related Cdc42 effectors, in the first phase of Cdc42 polarization in haploid cells. We propose that the first phase of Cdc42 polarization is mediated by positive feedback loops that function in parallel-one involving Rsr1 via local activation of Cdc42 in response to spatial cues and another involving Gic1 or Gic2 via reduction of diffusion of active Cdc42.
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Affiliation(s)
- Pil Jung Kang
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Kristi E Miller
- Molecular Cellular Developmental Biology Program, The Ohio State University, Columbus, OH 43210
| | - Julia Guegueniat
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Laure Beven
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Hay-Oak Park
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210.,Molecular Cellular Developmental Biology Program, The Ohio State University, Columbus, OH 43210
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Geymonat M, Spanos A, Jensen S, Sedgwick SG. Phosphorylation of Lte1 by Cdk prevents polarized growth during mitotic arrest in S. cerevisiae. J Cell Biol 2010; 191:1097-112. [PMID: 21149565 PMCID: PMC3002025 DOI: 10.1083/jcb.201005070] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 11/09/2010] [Indexed: 01/19/2023] Open
Abstract
Lte1 is known as a regulator of mitotic progression in budding yeast. Here we demonstrate phosphorylation-dependent inhibition of polarized bud growth during G2/M by Lte1. Cla4 activity first localizes Lte1 to the polarity cap and thus specifically to the bud. This localization is a prerequisite for subsequent Clb-Cdk-dependent phosphorylation of Lte1 and its relocalization to the entire bud cortex. There, Lte1 interferes with activation of the small GTPases, Ras and Bud1. The inhibition of Bud1 prevents untimely polarization until mitosis is completed and Cdc14 phosphatase is released. Inhibition of Bud1 and Ras depends on Lte1's GEF-like domain, which unexpectedly inhibits these small G proteins. Thus, Lte1 has dual functions for regulation of mitotic progression: it both induces mitotic exit and prevents polarized growth during mitotic arrest, thereby coupling cell cycle progression and morphological development.
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Affiliation(s)
- Marco Geymonat
- Division of Stem Cell Biology and Developmental Genetics, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, England, UK.
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3
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Abstract
Eukaryotic cells display a wide range of morphologies important for cellular function and development. A particular cell shape is made via the generation of asymmetry in the organization of cytoskeletal elements, usually leading to actin localization at sites of growth. The Rho family of GTPases is present in all eukaryotic cells, from yeast to mammals, and their role as key regulators in the signalling pathways that control actin organization and morphogenetic processes is well known. In the present review we will discuss the role of Rho GTPases as regulators of yeasts' polarized growth, their mechanism of activation and signalling pathways in Saccharomyces cerevisiae and Schizosaccharomyces pombe. These two model yeasts have been very useful in the study of the molecular mechanisms responsible for cell polarity. As in other organisms with cell walls, yeast's polarized growth is closely related to cell-wall biosynthesis, and Rho GTPases are critical modulators of this process. They provide the co-ordinated regulation of cell-wall biosynthetic enzymes and actin organization required to maintain cell integrity during vegetative growth.
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Yakir-Tamang L, Gerst JE. Phosphoinositides, exocytosis and polarity in yeast: all about actin? Trends Cell Biol 2009; 19:677-84. [PMID: 19818626 DOI: 10.1016/j.tcb.2009.09.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Revised: 07/21/2009] [Accepted: 09/16/2009] [Indexed: 10/20/2022]
Abstract
Cell polarity is necessary for cell division, morphogenesis and motility in eukaryotes, and is determined by dynamic control of the cytoskeleton and secretory pathway to promote directional growth. In yeast, three essential and tightly-regulated processes orchestrate polarization and facilitate bud growth. These processes include phosphoinositide (PI) signaling, Rho GTPase regulation of the actin cytoskeleton, and exocytosis. As yet, the interplay between these different processes is unclear, and two main models (Spatial Landmark and Allosteric Local Activation) have been proposed for Rho GTPase control of polarization in yeast. Here, we summarize the inter-relationship between these growth processes and present a more unified model, the Exocytic Signal model, which proposes that exocytosis and actin regulation are fully integrated events mediated by PI signaling.
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Affiliation(s)
- Liat Yakir-Tamang
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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Motizuki M, Xu Z. Importance of Polarisome Proteins in Reorganization of Actin Cytoskeleton at Low pH in Saccharomyces cerevisiae. ACTA ACUST UNITED AC 2009; 146:705-12. [DOI: 10.1093/jb/mvp116] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Yakir-Tamang L, Gerst JE. A phosphatidylinositol-transfer protein and phosphatidylinositol-4-phosphate 5-kinase control Cdc42 to regulate the actin cytoskeleton and secretory pathway in yeast. Mol Biol Cell 2009; 20:3583-97. [PMID: 19477927 DOI: 10.1091/mbc.e08-10-1073] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The actin cytoskeleton rapidly depolarizes in yeast secretory (sec) mutants at restrictive temperatures. Thus, an unknown signal conferred upon secretion is necessary for actin polarity and exocytosis. Here, we show that a phosphatidylinositol (PI) transfer protein, Sfh5, and a phosphatidylinositol-4-phosphate 5-kinase, Mss4, facilitate Cdc42 activation to concomitantly regulate both actin and protein trafficking. Defects in Mss4 function led to actin depolarization, an inhibition of secretion, reduced levels of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)] in membranes, mislocalization of a pleckstrin homology domain fused to green fluorescent protein, and the mislocalization of Cdc42. Similar defects were observed in sec, myo2-66, and cdc42-6 mutants at elevated temperatures and were rescued by the overexpression of MSS4. Likewise, the overexpression of SFH5 or CDC42 could ameliorate these defects in many sec mutants, most notably in sec3Delta cells, indicating that Cdc42-mediated effects upon actin and secretion do not necessitate Sec3 function. Moreover, mutation of the residues involved in PI binding in Sfh5 led to the mislocalization and loss of function of both Sfh5 and Cdc42. Based upon these findings, we propose that the exocytic signal involves PI delivery to the PI kinases (i.e., Mss4) by Sfh5, generation of PI(4,5)P(2), and PI(4,5)P(2)-dependent regulation of Cdc42 and the actin cytoskeleton.
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Affiliation(s)
- Liat Yakir-Tamang
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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7
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Carbó N, Pérez-Martín J. Spa2 is required for morphogenesis but it is dispensable for pathogenicity in the phytopathogenic fungus Ustilago maydis. Fungal Genet Biol 2008; 45:1315-27. [PMID: 18674629 DOI: 10.1016/j.fgb.2008.06.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Revised: 06/23/2008] [Accepted: 06/29/2008] [Indexed: 01/05/2023]
Abstract
The increasing evidence linking regulation of polar growth and pathogenicity in fungi has elicited a significant effort devoted to produce a better understanding of mechanisms determining polarization in pathogenic fungi. Here we characterize in the phytopathogenic basidiomycete Ustilago maydis, the Spa2 protein, a well-known component of polarisome, firstly described in Saccharomyces cerevisiae. U. maydis display a dimorphic switch between budding growth of hapoid cells and filamentous growth of the dikaryon. During yeast growth, a GFP-tagged Spa2 protein localized to distinct growth sites in a cell cycle-specific manner, while during hyphal growth is persistently located to hyphal tips. Deletion of spa2 gene produces rounder budding cells and thicker filaments than wild-type cells, suggesting a role of Spa2 for the determination of the growth area in U. maydis. We also address the connections between Spa2 and the actin- and microtubule-cytoskeleton. We found that the absence of Spa2 does not affect cytoskeleton organization and strikingly, interference with actin filament or microtubule formation does not affect the polar localization of Spa2. In contrast, defects in the small GTPase Rac1 seems to affect the ability of Spa2 to locate to precise sites at the tip cell. Finally, to our surprise, we found that cells defectives in Spa2 function were as pathogenic as wild-type cells.
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Affiliation(s)
- Natalia Carbó
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología CSIC, Madrid, Spain
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Meyer V, Arentshorst M, van den Hondel CAMJJ, Ram AFJ. The polarisome component SpaA localises to hyphal tips of Aspergillus niger and is important for polar growth. Fungal Genet Biol 2008; 45:152-64. [PMID: 17826199 DOI: 10.1016/j.fgb.2007.07.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2007] [Revised: 07/09/2007] [Accepted: 07/11/2007] [Indexed: 11/23/2022]
Abstract
Hyphal tip growth is a key feature of filamentous fungi, however, the molecular mechanism(s) that regulate cell polarity are poorly understood. On the other hand, much more is known about polarised growth in the yeast Saccharomyces cerevisiae. Here, the proteins Spa2p, Bni1p, Bud6p and Pea2p form a protein complex named the polarisome known to be important for the assurance of polar growth. We searched the genome of Aspergillus niger and identified homologues for Spa2p, Bni1p, Bud6p but not for Pea2p. We characterised the function of the Spa2p homologue SpaA by determining its cellular localisation and by constructing deletion and overexpressing mutant strains. SpaA was found to be localised exclusively at the hyphal tip, suggesting that SpaA can be used as marker for polarisation. Deletion and overexpression of spaA resulted in reduced growth rate, increased hyphal diameter and polarity defects, indicating that one of the functions of SpaA is to ensure polarity maintenance. In addition, we could show that SpaA is able to complement the defective haploid invasive growth phenotype of a S. cerevisiae SPA2 null mutant. We suggest that the function of SpaA is to ensure maximal polar growth rate in A. niger.
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Affiliation(s)
- Vera Meyer
- Department of Microbiology and Genetics, Institute of Biotechnology, Berlin University of Technology, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany.
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Virag A, Lee MP, Si H, Harris SD. Regulation of hyphal morphogenesis by cdc42 and rac1 homologues in Aspergillus nidulans. Mol Microbiol 2007; 66:1579-96. [PMID: 18005099 DOI: 10.1111/j.1365-2958.2007.06021.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The ability of filamentous fungi to form hyphae requires the establishment and maintenance of a stable polarity axis. Based on studies in yeasts and animals, the GTPases Cdc42 and Rac1 are presumed to play a central role in organizing the morphogenetic machinery to enable axis formation and stabilization. Here, we report that Cdc42 (ModA) and Rac1 (RacA) share an overlapping function required for polarity establishment in Aspergillus nidulans. Nevertheless, Cdc42 appears to have a more important role in hyphal morphogenesis in that it alone is required for the timely formation of lateral branches. In addition, we provide genetic evidence suggesting that the polarisome components SepA and SpaA function downstream of Cdc42 in a pathway that may regulate microfilament formation. Finally, we show that microtubules become essential for the establishment of hyphal polarity when the function of either Cdc42 or SepA is compromised. Our results are consistent with the action of parallel Cdc42 and microtubule-based pathways in regulating the formation of a stable axis of hyphal polarity in A. nidulans.
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Affiliation(s)
- Aleksandra Virag
- Plant Science Initiative and Department of Plant Pathology, University of Nebraska, Lincoln, NE 68588-0660, USA
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Park HO, Bi E. Central roles of small GTPases in the development of cell polarity in yeast and beyond. Microbiol Mol Biol Rev 2007; 71:48-96. [PMID: 17347519 PMCID: PMC1847380 DOI: 10.1128/mmbr.00028-06] [Citation(s) in RCA: 323] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
SUMMARY The establishment of cell polarity is critical for the development of many organisms and for the function of many cell types. A large number of studies of diverse organisms from yeast to humans indicate that the conserved, small-molecular-weight GTPases function as key signaling proteins involved in cell polarization. The budding yeast Saccharomyces cerevisiae is a particularly attractive model because it displays pronounced cell polarity in response to intracellular and extracellular cues. Cells of S. cerevisiae undergo polarized growth during various phases of their life cycle, such as during vegetative growth, mating between haploid cells of opposite mating types, and filamentous growth upon deprivation of nutrition such as nitrogen. Substantial progress has been made in deciphering the molecular basis of cell polarity in budding yeast. In particular, it becomes increasingly clear how small GTPases regulate polarized cytoskeletal organization, cell wall assembly, and exocytosis at the molecular level and how these GTPases are regulated. In this review, we discuss the key signaling pathways that regulate cell polarization during the mitotic cell cycle and during mating.
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Affiliation(s)
- Hay-Oak Park
- Department of Molecular Genetics, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210-1292, USA.
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Hehnly H, Stamnes M. Regulating cytoskeleton-based vesicle motility. FEBS Lett 2007; 581:2112-8. [PMID: 17335816 PMCID: PMC1974873 DOI: 10.1016/j.febslet.2007.01.094] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Accepted: 01/18/2007] [Indexed: 11/17/2022]
Abstract
During vesicular transport, the assembly of the coat complexes and the selection of cargo proteins must be coordinated with the subsequent translocation of vesicles from the donor to an acceptor compartment. Here, we review recent progress toward uncovering the molecular mechanisms that connect transport vesicles to the protein machinery responsible for cytoskeleton-mediated motility. An emerging theme is that vesicle cargo proteins, either directly or through binding interactions with coat proteins, are able to influence cytoskeletal dynamics and motor protein function. Hence, a vesicle's cargo composition may help direct its intracellular motility and targeting.
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Affiliation(s)
- Heidi Hehnly
- Department of Molecular Physiology and Biophysics, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, IA 52242, USA
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Current awareness on yeast. Yeast 2006. [DOI: 10.1002/yea.1317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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