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Kang PJ, Mullner R, Lian K, Park HO. Cdc42 couples septin recruitment to the axial landmark assembly via Axl2 in budding yeast. J Cell Sci 2024; 137:jcs261080. [PMID: 37712304 PMCID: PMC10617600 DOI: 10.1242/jcs.261080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Accepted: 09/11/2023] [Indexed: 09/16/2023] Open
Abstract
Cell polarization generally occurs along a single axis that is directed by a spatial cue. Cells of the budding yeast Saccharomyces cerevisiae undergo polarized growth and oriented cell division in a spatial pattern by selecting a specific bud site. Haploid a or α cells bud in the axial pattern in response to a transient landmark that includes Bud3, Bud4, Axl1 and Axl2. Septins, a family of filament-forming GTP-binding proteins, are also involved in axial budding and are recruited to an incipient bud site, but the mechanism of recruitment remains unclear. Here, we show that Axl2 interacts with Bud3 and the Cdc42 GTPase in its GTP-bound state. Axl2 also interacts with Cdc10, a septin subunit, promoting efficient recruitment of septins near the cell division site. Furthermore, a cdc42 mutant defective in the axial budding pattern at a semi-permissive temperature had a reduced interaction with Axl2 and compromised septin recruitment in the G1 phase. We thus propose that active Cdc42 brings Axl2 to the Bud3-Bud4 complex and that Axl2 then interacts with Cdc10, linking septin recruitment to the axial landmark.
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Affiliation(s)
- Pil Jung Kang
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | - Rachel Mullner
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | - Kendra Lian
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | - Hay-Oak Park
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
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2
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Brauns F, Iñigo de la Cruz L, Daalman WKG, de Bruin I, Halatek J, Laan L, Frey E. Redundancy and the role of protein copy numbers in the cell polarization machinery of budding yeast. Nat Commun 2023; 14:6504. [PMID: 37845215 PMCID: PMC10579396 DOI: 10.1038/s41467-023-42100-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Accepted: 09/26/2023] [Indexed: 10/18/2023] Open
Abstract
How can a self-organized cellular function evolve, adapt to perturbations, and acquire new sub-functions? To make progress in answering these basic questions of evolutionary cell biology, we analyze, as a concrete example, the cell polarity machinery of Saccharomyces cerevisiae. This cellular module exhibits an intriguing resilience: it remains operational under genetic perturbations and recovers quickly and reproducibly from the deletion of one of its key components. Using a combination of modeling, conceptual theory, and experiments, we propose that multiple, redundant self-organization mechanisms coexist within the protein network underlying cell polarization and are responsible for the module's resilience and adaptability. Based on our mechanistic understanding of polarity establishment, we hypothesize that scaffold proteins, by introducing new connections in the existing network, can increase the redundancy of mechanisms and thus increase the evolvability of other network components. Moreover, our work gives a perspective on how a complex, redundant cellular module might have evolved from a more rudimental ancestral form.
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Affiliation(s)
- Fridtjof Brauns
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Munich, Germany
- Kavli Institute for Theoretical Physics, University of California Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Leila Iñigo de la Cruz
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Werner K-G Daalman
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Ilse de Bruin
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Jacob Halatek
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Liedewij Laan
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands.
| | - Erwin Frey
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Munich, Germany.
- Max Planck School Matter to Life, Hofgartenstraße 8, D-80539, Munich, Germany.
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Kang PJ, Mullner R, Lian K, Park HO. Cdc42 couples septin recruitment to the axial landmark assembly via Axl2 in budding yeast. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.25.554823. [PMID: 37662239 PMCID: PMC10473694 DOI: 10.1101/2023.08.25.554823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Cell polarization generally occurs along a single axis that is directed by a spatial cue. Cells of the budding yeast Saccharomyces cerevisiae undergo polarized growth and oriented cell division in a spatial pattern by selecting a specific bud site. Haploid a or α cells bud in the axial pattern in response to a transient landmark that includes Bud3, Bud4, Axl1, and Axl2. Septins, a family of filament-forming GTP-binding proteins, are also involved in axial budding and recruited to an incipient bud site, but the mechanism of recruitment remains unclear. Here, we show that Axl2 interacts with Bud3 and the Cdc42 GTPase in its GTP-bound state. Axl2 also interacts with Cdc10, a septin subunit, promoting efficient recruitment of septins near the cell division site. Furthermore, a cdc42 mutant defective in the axial budding pattern at a semi-permissive temperature had a reduced interaction with Axl2 and compromised septin recruitment in the G1 phase. We thus propose that active Cdc42 brings Axl2 to the Bud3-Bud4 complex and that Axl2 then interacts with Cdc10, linking septin recruitment to the axial landmark.
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Kang PJ, Mullner R, Li H, Hansford D, Shen HW, Park HO. Upregulation of the Cdc42 GTPase limits the replicative lifespan of budding yeast. Mol Biol Cell 2022; 33:br5. [PMID: 35044837 PMCID: PMC9250358 DOI: 10.1091/mbc.e21-04-0208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cdc42, a conserved Rho GTPase, plays a central role in polarity establishment in yeast and animals. Cell polarity is critical for asymmetric cell division, and asymmetric cell division underlies replicative aging of budding yeast. Yet how Cdc42 and other polarity factors impact life span is largely unknown. Here we show by live-cell imaging that the active Cdc42 level is sporadically elevated in wild type during repeated cell divisions but rarely in the long-lived bud8 deletion cells. We find a novel Bud8 localization with cytokinesis remnants, which also recruit Rga1, a Cdc42 GTPase activating protein. Genetic analyses and live-cell imaging suggest that Rga1 and Bud8 oppositely impact life span likely by modulating active Cdc42 levels. An rga1 mutant, which has a shorter life span, dies at the unbudded state with a defect in polarity establishment. Remarkably, Cdc42 accumulates in old cells, and its mild overexpression accelerates aging with frequent symmetric cell divisions, despite no harmful effects on young cells. Our findings implicate that the interplay among these positive and negative polarity factors limits the life span of budding yeast.
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Affiliation(s)
- Pil Jung Kang
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | - Rachel Mullner
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | - Haoyu Li
- Department of Computer Science and Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Derek Hansford
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Han-Wei Shen
- Department of Computer Science and Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Hay-Oak Park
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
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Overexpression of the Aspergillus fumigatus Small GTPase, RsrA, Promotes Polarity Establishment during Germination. J Fungi (Basel) 2020; 6:jof6040285. [PMID: 33202962 PMCID: PMC7711769 DOI: 10.3390/jof6040285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 11/06/2020] [Accepted: 11/11/2020] [Indexed: 11/17/2022] Open
Abstract
Cell polarization comprises highly controlled processes and occurs in most eukaryotic organisms. In yeast, the processes of budding, mating and filamentation require coordinated mechanisms leading to polarized growth. Filamentous fungi, such as Aspergillus fumigatus, are an extreme example of cell polarization, essential for both vegetative and pathogenic growth. A major regulator of polarized growth in yeast is the small GTPase Rsr1, which is essential for bud-site selection. Here, we show that deletion of the putative A. fumigatus ortholog, rsrA, causes only a modest reduction of growth rate and delay in germ tube emergence. In contrast, overexpression of rsrA results in a morphogenesis defect, characterized by a significant delay in polarity establishment followed by the establishment of multiple growth axes. This aberrant phenotype is reversed when rsrA expression levels are decreased, suggesting that correct regulation of RsrA activity is crucial for accurate patterning of polarity establishment. Despite this finding, deletion or overexpression of rsrA resulted in no changes of A. fumigatus virulence attributes in a mouse model of invasive aspergillosis. Additional mutational analyses revealed that RsrA cooperates genetically with the small GTPase, RasA, to support A. fumigatus viability.
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Abstract
The Rho GTPase Cdc42 is a central regulator of cell polarity in diverse cell types. The activity of Cdc42 is dynamically controlled in time and space to enable distinct polarization events, which generally occur along a single axis in response to spatial cues. Our understanding of the mechanisms underlying Cdc42 polarization has benefited largely from studies of the budding yeast Saccharomyces cerevisiae, a genetically tractable model organism. In budding yeast, Cdc42 activation occurs in two temporal steps in the G1 phase of the cell cycle to establish a proper growth site. Here, we review findings in budding yeast that reveal an intricate crosstalk among polarity proteins for biphasic Cdc42 regulation. The first step of Cdc42 activation may determine the axis of cell polarity, while the second step ensures robust Cdc42 polarization for growth. Biphasic Cdc42 polarization is likely to ensure the proper timing of events including the assembly and recognition of spatial landmarks and stepwise assembly of a new ring of septins, cytoskeletal GTP-binding proteins, at the incipient bud site. Biphasic activation of GTPases has also been observed in mammalian cells, suggesting that biphasic activation could be a general mechanism for signal-responsive cell polarization. Cdc42 activity is necessary for polarity establishment during normal cell division and development, but its activity has also been implicated in the promotion of aging. We also discuss negative polarity signaling and emerging concepts of Cdc42 signaling in cellular aging.
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Affiliation(s)
- Kristi E Miller
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210.,Present address: Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Pil Jung Kang
- 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
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Prabhakar A, Chow J, Siegel AJ, Cullen PJ. Regulation of intrinsic polarity establishment by a differentiation-type MAPK pathway in S. cerevisiae. J Cell Sci 2020; 133:jcs241513. [PMID: 32079658 PMCID: PMC7174846 DOI: 10.1242/jcs.241513] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 02/12/2020] [Indexed: 01/15/2023] Open
Abstract
All cells establish and maintain an axis of polarity that is critical for cell shape and progression through the cell cycle. A well-studied example of polarity establishment is bud emergence in the yeast Saccharomyces cerevisiae, which is controlled by the Rho GTPase Cdc42p. The prevailing view of bud emergence does not account for regulation by extrinsic cues. Here, we show that the filamentous growth mitogen activated protein kinase (fMAPK) pathway regulates bud emergence under nutrient-limiting conditions. The fMAPK pathway regulated the expression of polarity targets including the gene encoding a direct effector of Cdc42p, Gic2p. The fMAPK pathway also stimulated GTP-Cdc42p levels, which is a critical determinant of polarity establishment. The fMAPK pathway activity was spatially restricted to bud sites and active during the period of the cell cycle leading up to bud emergence. Time-lapse fluorescence microscopy showed that the fMAPK pathway stimulated the rate of bud emergence during filamentous growth. Unregulated activation of the fMAPK pathway induced multiple rounds of symmetry breaking inside the growing bud. Collectively, our findings identify a new regulatory aspect of bud emergence that sensitizes this essential cellular process to external cues.
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Affiliation(s)
- Aditi Prabhakar
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260-1300, USA
| | - Jacky Chow
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260-1300, USA
| | - Alan J Siegel
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260-1300, USA
| | - Paul J Cullen
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260-1300, USA
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Miller KE, Lo WC, Chou CS, Park HO. Temporal regulation of cell polarity via the interaction of the Ras GTPase Rsr1 and the scaffold protein Bem1. Mol Biol Cell 2019; 30:2543-2557. [PMID: 31411940 PMCID: PMC6740199 DOI: 10.1091/mbc.e19-02-0106] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The Cdc42 guanosine triphosphatase (GTPase) plays a central role in polarity development in species ranging from yeast to humans. In budding yeast, a specific growth site is selected in the G1 phase. Rsr1, a Ras GTPase, interacts with Cdc42 and its associated proteins to promote polarized growth at the proper bud site. Yet how Rsr1 regulates cell polarization is not fully understood. Here, we show that Rsr1-GDP interacts with the scaffold protein Bem1 in early G1, likely hindering the role of Bem1 in Cdc42 polarization and polarized secretion. Consistent with these in vivo observations, mathematical modeling predicts that Bem1 is unable to promote Cdc42 polarization in early G1 in the presence of Rsr1-GDP. We find that a part of the Bem1 Phox homology domain, which overlaps with a region interacting with the exocyst component Exo70, is necessary for the association of Bem1 with Rsr1-GDP. Overexpression of the GDP-locked Rsr1 interferes with Bem1-dependent Exo70 polarization. We thus propose that Rsr1 functions in spatial and temporal regulation of polarity establishment by associating with distinct polarity factors in its GTP- and GDP-bound states.
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Affiliation(s)
- Kristi E Miller
- Molecular Cellular Developmental Biology Program, The Ohio State University, Columbus, OH 43210
| | - Wing-Cheong Lo
- Department of Mathematics, City University of Hong Kong, Kowloon, Hong Kong
| | - Ching-Shan Chou
- Department of Mathematics, The Ohio State University, Columbus, OH 43210
| | - Hay-Oak Park
- Molecular Cellular Developmental Biology Program, The Ohio State University, Columbus, OH 43210.,Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
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Daniels CN, Zyla TR, Lew DJ. A role for Gic1 and Gic2 in Cdc42 polarization at elevated temperature. PLoS One 2018; 13:e0200863. [PMID: 30566437 PMCID: PMC6300207 DOI: 10.1371/journal.pone.0200863] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 11/09/2018] [Indexed: 12/27/2022] Open
Abstract
The conserved Rho-family GTPase Cdc42 is a master regulator of polarity establishment in many cell types. Cdc42 becomes activated and concentrated in a region of the cell cortex, and recruits a variety of effector proteins to that site. In turn, many effectors participate in regulation of cytoskeletal elements in order to remodel the cytoskeleton in a polarized manner. The budding yeast Saccharomyces cerevisiae has served as a tractable model system for studies of cell polarity. In yeast cells, Cdc42 polarization involves a positive feedback loop in which effectors called p21-activated kinases (PAKs) act to recruit a Cdc42-directed guanine nucleotide exchange factor (GEF), generating more GTP-Cdc42 in areas that already have GTP-Cdc42. The GTPase-interacting components (GICs) Gic1 and Gic2 are also Cdc42 effectors, and have been implicated in regulation of the actin and septin cytoskeleton. However, we report that cells lacking GICs are primarily defective in polarizing Cdc42 itself, suggesting that they act upstream as well as downstream of Cdc42 in yeast. Our findings suggest that feedback pathways involving GTPase effectors may be more prevalent than had been appreciated.
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Affiliation(s)
- Christine N. Daniels
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, United States of America
| | - Trevin R. Zyla
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, United States of America
| | - Daniel J. Lew
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, United States of America
- * E-mail:
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Molecular mechanisms of contractile-ring constriction and membrane trafficking in cytokinesis. Biophys Rev 2018; 10:1649-1666. [PMID: 30448943 DOI: 10.1007/s12551-018-0479-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 11/06/2018] [Indexed: 12/14/2022] Open
Abstract
In this review, we discuss the molecular mechanisms of cytokinesis from plants to humans, with a focus on contribution of membrane trafficking to cytokinesis. Selection of the division site in fungi, metazoans, and plants is reviewed, as well as the assembly and constriction of a contractile ring in fungi and metazoans. We also provide an introduction to exocytosis and endocytosis, and discuss how they contribute to successful cytokinesis in eukaryotic cells. The conservation in the coordination of membrane deposition and cytoskeleton during cytokinesis in fungi, metazoans, and plants is highlighted.
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