scholarly journals Mating yeast cells use an intrinsic polarity site to assemble a pheromone-gradient tracking machine

2019 ◽  
Vol 218 (11) ◽  
pp. 3730-3752 ◽  
Author(s):  
Xin Wang ◽  
Wei Tian ◽  
Bryan T. Banh ◽  
Bethanie-Michelle Statler ◽  
Jie Liang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Plasma Membrane ◽  
G Protein ◽  
Yeast Cells ◽  
Mating Types ◽  
Gradient Sensing ◽  
Feedback Mechanisms ◽  
Growth Site ◽  
Endocytic Machinery ◽  
Mating Projection

The mating of budding yeast depends on chemotropism, a fundamental cellular process. The two yeast mating types secrete peptide pheromones that bind to GPCRs on cells of the opposite type. Cells find and contact a partner by determining the direction of the pheromone source and polarizing their growth toward it. Actin-directed secretion to the chemotropic growth site (CS) generates a mating projection. When pheromone-stimulated cells are unable to sense a gradient, they form mating projections where they would have budded in the next cell cycle, at a position called the default polarity site (DS). Numerous models have been proposed to explain yeast gradient sensing, but none address how cells reliably switch from the intrinsically determined DS to the gradient-aligned CS, despite a weak spatial signal. Here we demonstrate that, in mating cells, the initially uniform receptor and G protein first polarize to the DS, then redistribute along the plasma membrane until they reach the CS. Our data indicate that signaling, polarity, and trafficking proteins localize to the DS during assembly of what we call the gradient tracking machine (GTM). Differential activation of the receptor triggers feedback mechanisms that bias exocytosis upgradient and endocytosis downgradient, thus enabling redistribution of the GTM toward the pheromone source. The GTM stabilizes when the receptor peak centers at the CS and the endocytic machinery surrounds it. A computational model simulates GTM tracking and stabilization and correctly predicts that its assembly at a single site contributes to mating fidelity.

scholarly journals Polarization of the Yeast Pheromone Receptor Requires Its Internalization but Not Actin-dependent Secretion

2010 ◽  
Vol 21 (10) ◽  
pp. 1737-1752 ◽  
Author(s):  
Dmitry V. Suchkov ◽  
Reagan DeFlorio ◽  
Edward Draper ◽  
Amber Ismael ◽  
Madhushalini Sukumar ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Protein Localization ◽  
Receptor Internalization ◽  
Gradient Sensing ◽  
Pheromone Receptor ◽  
Surface Receptors ◽  
Chemical Gradients ◽  
Actin Cables ◽  
Mating Projection

In the best understood models of eukaryotic directional sensing, chemotactic cells maintain a uniform distribution of surface receptors even when responding to chemical gradients. The yeast pheromone receptor is also uniformly distributed on the plasma membrane of vegetative cells, but pheromone induces its polarization into “crescents” that cap the future mating projection. Here, we find that in pheromone-treated cells, receptor crescents are visible before detectable polarization of actin cables and that the receptor can polarize in the absence of actin-dependent directed secretion. Receptor internalization, in contrast, seems to be essential for the generation of receptor polarity, and mutations that deregulate this process confer dramatic defects in directional sensing. We also show that pheromone induces the internalization and subsequent polarization of the mating-specific Gα and Gβ proteins and that the changes in G protein localization depend on receptor internalization and receptor–Gα coupling. Our data suggest that the polarization of the receptor and its G protein precedes actin polarization and is important for gradient sensing. We propose that the establishment of receptor/G protein polarity depends on a novel mechanism involving differential internalization and that this serves to amplify the shallow gradient of activated receptor across the cell.

scholarly journals Mobility of the gradient tracking machine in mating yeast depends on Bud1 inactivation and actin-independent vesicle delivery

2021 ◽  
Author(s):  
Xin Wang ◽  
David Stone
Keyword(s):  
Cell Cycle ◽  
Mating Type ◽  
Positive Feedback ◽  
Yeast Cells ◽  
Polarized Growth ◽  
Opposite Mating Type ◽  
Gradient Sensing ◽  
Feedback Mechanisms ◽  
Ras Gtpase ◽  
Sensing Model

Abstract The mating of budding yeast depends on chemotropism, a fundamental cellular process. Haploid yeast cells of opposite mating type signal their positions to one another through the secretion of mating pheromones. We have proposed a deterministic gradient sensing model that explains how these cells orient toward their mating partners. Using the cell-cycle determined default polarity site (DS), cells assemble a gradient tracking machine (GTM) composed of signaling, polarity, and trafficking proteins. After assembly, the GTM redistributes up the gradient, aligns with the pheromone source, and triggers polarized growth toward the partner. Because strong positive feedback mechanisms drive polarized growth at the DS, it is unclear how the GTM is released for tracking after its assembly is complete. What prevents the GTM from triggering polarized growth at the DS? Here we describe two mechanisms that enable tracking. First, the Ras GTPase Bud1 must be inactivated to release the GTM. Second, actin-independent – but not actin-dependent – vesicle delivery must be targeted upgradient to effect GTM redistribution.

scholarly journals Phosphorylated Gβ is a directional cue during yeast gradient tracking

2021 ◽  
Vol 14 (682) ◽  
pp. eabf4710
Author(s):  
Rashida Abdul-Ganiyu ◽  
Leon A. Venegas ◽  
Xin Wang ◽  
Charles Puerner ◽  
Robert A. Arkowitz ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Yeast Cells ◽  
Mutant Form ◽  
Final Position ◽  
Opposite Mating Type ◽  
Gradient Sensing ◽  
Growth Site ◽  
Mating Efficiency ◽  
Sensing Model ◽  
Tracking Direction

Budding yeast cells interpret shallow pheromone gradients from cells of the opposite mating type, polarize their growth toward the pheromone source, and fuse at the chemotropic growth site. We previously proposed a deterministic, gradient-sensing model that explains how yeast cells switch from the intrinsically positioned default polarity site (DS) to the gradient-aligned chemotropic site (CS) at the plasma membrane. Because phosphorylation of the mating-specific Gβ subunit is thought to be important for this process, we developed a biosensor that bound to phosphorylated but not unphosphorylated Gβ and monitored its spatiotemporal dynamics to test key predictions of our gradient-sensing model. In mating cells, the biosensor colocalized with both Gβ and receptor reporters at the DS and then tracked with them to the CS. The biosensor concentrated on the leading side of the tracking Gβ and receptor peaks and was the first to arrive and stop tracking at the CS. Our data showed that the concentrated localization of phosphorylated Gβ correlated with the tracking direction and final position of the G protein and receptor, consistent with the idea that gradient-regulated phosphorylation and dephosphorylation of Gβ contributes to gradient sensing. Cells expressing a nonphosphorylatable mutant form of Gβ exhibited defects in gradient tracking, orientation toward mating partners, and mating efficiency.

scholarly journals Antagonistic regulation of Fus2p nuclear localization by pheromone signaling and the cell cycle

2009 ◽  
Vol 184 (3) ◽  
pp. 409-422 ◽  
Author(s):  
Casey A. Ydenberg ◽  
Mark D. Rose
Keyword(s):  
Cell Cycle ◽  
S Phase ◽  
Yeast Cells ◽  
Transcriptional Level ◽  
G1 Arrest ◽  
Cycle Arrest ◽  
Pheromone Signaling ◽  
Dependent Inhibition ◽  
Induced Proteins ◽  
Mating Projection

When yeast cells sense mating pheromone, they undergo a characteristic response involving changes in transcription, cell cycle arrest in early G1, and polarization along the pheromone gradient. Cells in G2/M respond to pheromone at the transcriptional level but do not polarize or mate until G1. Fus2p, a key regulator of cell fusion, localizes to the tip of the mating projection during pheromone-induced G1 arrest. Although Fus2p was expressed in G2/M cells after pheromone induction, it accumulated in the nucleus until after cell division. As cells arrested in G1, Fus2p was exported from the nucleus and localized to the nascent tip. Phosphorylation of Fus2p by Fus3p was required for Fus2p export; cyclin/Cdc28p-dependent inhibition of Fus3p during late G1 through S phase was sufficient to block exit. However, during G2/M, when Fus3p was activated by pheromone signaling, Cdc28p activity again blocked Fus2p export. Our results indicate a novel mechanism by which pheromone-induced proteins are regulated during the transition from mitosis to conjugation.

scholarly journals Yeast G-proteins mediate directional sensing and polarization behaviors in response to changes in pheromone gradient direction

2013 ◽  
Vol 24 (4) ◽  
pp. 521-534 ◽  
Author(s):  
Travis I. Moore ◽  
Hiromasa Tanaka ◽  
Hyung Joon Kim ◽  
Noo Li Jeon ◽  
Tau-Mu Yi
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Cell Polarity ◽  
Yeast Cells ◽  
Dependent Manner ◽  
Protein Activity ◽  
Gradient Sensing ◽  
Heterotrimeric G Protein ◽  
Low Concentrations ◽  
High Concentrations

Yeast cells polarize by projecting up mating pheromone gradients, a classic cell polarity behavior. However, these chemical gradients may shift direction. We examine how yeast cells sense and respond to a 180o switch in the direction of microfluidically generated pheromone gradients. We identify two behaviors: at low concentrations of α-factor, the initial projection grows by bending, whereas at high concentrations, cells form a second projection toward the new source. Mutations that increase heterotrimeric G-protein activity expand the bending-growth morphology to high concentrations; mutations that increase Cdc42 activity result in second projections at low concentrations. Gradient-sensing projection bending requires interaction between Gβγ and Cdc24, whereas gradient-nonsensing projection extension is stimulated by Bem1 and hyperactivated Cdc42. Of interest, a mutation in Gα affects both bending and extension. Finally, we find a genetic perturbation that exhibits both behaviors. Overexpression of the formin Bni1, a component of the polarisome, makes both bending-growth projections and second projections at low and high α-factor concentrations, suggesting a role for Bni1 downstream of the heterotrimeric G-protein and Cdc42 during gradient sensing and response. Thus we demonstrate that G-proteins modulate in a ligand-dependent manner two fundamental cell-polarity behaviors in response to gradient directional change.

Overexpression of the STE4 gene leads to mating response in haploid Saccharomyces cerevisiae

1990 ◽  
Vol 10 (1) ◽  
pp. 217-222
Author(s):  
M Whiteway ◽  
L Hougan ◽  
D Y Thomas
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
G Protein ◽  
Gene Product ◽  
Beta Subunit ◽  
Yeast Cells ◽  
Pheromone Response ◽  
Mating Pheromone ◽  
Cycle Arrest

The STE4 gene of Saccharomyces cerevisiae encodes the beta subunit of the yeast pheromone receptor-coupled G protein. Overexpression of the STE4 protein led to cell cycle arrest of haploid cells. This arrest was like the arrest mediated by mating pheromones in that it led to similar morphological changes in the arrested cells. The arrest occurred in haploid cells of either mating type but not in MATa/MAT alpha diploids, and it was suppressed by defects in genes such as STE12 that are needed for pheromone response. Overexpression of the STE4 gene product also suppressed the sterility of cells defective in the mating pheromone receptors encoded by the STE2 and STE3 genes. Cell cycle arrest mediated by STE4 overexpression was prevented in cells that either were overexpressing the SCG1 gene product (the alpha subunit of the G protein) or lacked the STE18 gene product (the gamma subunit of the G protein). This finding suggests that in yeast cells, the beta subunit is the limiting component of the active beta gamma element and that a proper balance in the levels of the G-protein subunits is critical to a normal mating pheromone response.

scholarly journals Localization and Signaling of GβSubunit Ste4p Are Controlled by a-Factor Receptor and thea-Specific Protein Asg7p

2000 ◽  
Vol 20 (23) ◽  
pp. 8826-8835 ◽  
Author(s):  
Jinah Kim ◽  
Eric Bortz ◽  
Hualin Zhong ◽  
Thomas Leeuw ◽  
Ekkehard Leberer ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Subcellular Location ◽  
Regulatory Process ◽  
Yeast Cells ◽  
Specific Gene ◽  
Β Subunit ◽  
Pheromone Signaling ◽  
Receptor Inhibition ◽  
In Cells

ABSTRACT Haploid yeast cells initiate pheromone signaling upon the binding of pheromone to its receptor and activation of the coupled G protein. A regulatory process termed receptor inhibition blocks pheromone signaling when the a-factor receptor is inappropriately expressed inMATa cells. Receptor inhibition blocks signaling by inhibiting the activity of the G protein β subunit, Ste4p. To investigate how Ste4p activity is inhibited, its subcellular location was examined. In wild-type cells, α-factor treatment resulted in localization of Ste4p to the plasma membrane of mating projections. In cells expressing the a-factor receptor, α-factor treatment resulted in localization of Ste4p away from the plasma membrane to an internal compartment. An altered version of Ste4p that is largely insensitive to receptor inhibition retained its association with the membrane in cells expressing the a-factor receptor. The inhibitory function of the a-factor receptor required ASG7, an a-specific gene of previously unknown function. ASG7 RNA was induced by pheromone, consistent with increased inhibition as the pheromone response progresses. The a-factor receptor inhibited signaling in its liganded state, demonstrating that the receptor can block the signal that it initiates. ASG7 was required for the altered localization of Ste4p that occurs during receptor inhibition, and the subcellular location of Asg7p was consistent with its having a direct effect on Ste4p localization. These results demonstrate that Asg7p mediates a regulatory process that blocks signaling from a G protein β subunit and causes its relocalization within the cell.

scholarly journals Overexpression of the STE4 gene leads to mating response in haploid Saccharomyces cerevisiae.

1990 ◽  
Vol 10 (1) ◽  
pp. 217-222 ◽  
Author(s):  
M Whiteway ◽  
L Hougan ◽  
D Y Thomas
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
G Protein ◽  
Gene Product ◽  
Beta Subunit ◽  
Yeast Cells ◽  
Pheromone Response ◽  
Mating Pheromone ◽  
Cycle Arrest

The STE4 gene of Saccharomyces cerevisiae encodes the beta subunit of the yeast pheromone receptor-coupled G protein. Overexpression of the STE4 protein led to cell cycle arrest of haploid cells. This arrest was like the arrest mediated by mating pheromones in that it led to similar morphological changes in the arrested cells. The arrest occurred in haploid cells of either mating type but not in MATa/MAT alpha diploids, and it was suppressed by defects in genes such as STE12 that are needed for pheromone response. Overexpression of the STE4 gene product also suppressed the sterility of cells defective in the mating pheromone receptors encoded by the STE2 and STE3 genes. Cell cycle arrest mediated by STE4 overexpression was prevented in cells that either were overexpressing the SCG1 gene product (the alpha subunit of the G protein) or lacked the STE18 gene product (the gamma subunit of the G protein). This finding suggests that in yeast cells, the beta subunit is the limiting component of the active beta gamma element and that a proper balance in the levels of the G-protein subunits is critical to a normal mating pheromone response.

scholarly journals Dual Lipid Modification Motifs in Gαand GγSubunits Are Required for Full Activity of the Pheromone Response Pathway inSaccharomyces cerevisiae

2000 ◽  
Vol 11 (3) ◽  
pp. 957-968 ◽  
Author(s):  
Carol L. Manahan ◽  
Madhavi Patnana ◽  
Kendall J. Blumer ◽  
Maurine E. Linder
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Yeast Cells ◽  
Pheromone Response ◽  
Guanine Nucleotide Binding Protein ◽  
Α Subunit ◽  
Protein Activation ◽  
Pheromone Response Pathway ◽  
G Protein Activation

To establish the biological function of thioacylation (palmitoylation), we have studied the heterotrimeric guanine nucleotide–binding protein (G protein) subunits of the pheromone response pathway of Saccharomyces cerevisiae. The yeast G protein γ subunit (Ste18p) is unusual among Gγsubunits because it is farnesylated at cysteine 107 and has the potential to be thioacylated at cysteine 106. Substitution of either cysteine results in a strong signaling defect. In this study, we found that Ste18p is thioacylated at cysteine 106, which depended on prenylation of cysteine 107. Ste18p was targeted to the plasma membrane even in the absence of prenylation or thioacylation. However, G protein activation released prenylation- or thioacylation-defective Ste18p into the cytoplasm. Hence, lipid modifications of the Gγsubunit are dispensable for G protein activation by receptor, but they are required to maintain the plasma membrane association of Gβγafter receptor-stimulated release from Gα. The G protein α subunit (Gpa1p) is tandemly modified at its N terminus with amide- and thioester-linked fatty acids. Here we show that Gpa1p was thioacylated in vivo with a mixture of radioactive myristate and palmitate. Mutation of the thioacylation site in Gpa1p resulted in yeast cells that displayed partial activation of the pathway in the absence of pheromone. Thus, dual lipidation motifs on Gpa1p and Ste18p are required for a fully functional pheromone response pathway.

scholarly journals Plasma membrane polarization during mating in yeast cells

2006 ◽  
Vol 173 (6) ◽  
pp. 861-866 ◽  
Author(s):  
Tomasz J. Proszynski ◽  
Robin Klemm ◽  
Michel Bagnat ◽  
Katharina Gaus ◽  
Kai Simons
Keyword(s):  
Plasma Membrane ◽  
Transmembrane Protein ◽  
Yeast Cells ◽  
Type I ◽  
Surface Polarity ◽  
Surface Distribution ◽  
Peripheral Proteins ◽  
Lipid Organization ◽  
Polarized Surface ◽  
Mating Projection

The yeast mating cell provides a simple paradigm for analyzing mechanisms underlying the generation of surface polarity. Endocytic recycling and slow diffusion on the plasma membrane were shown to facilitate polarized surface distribution of Snc1p (Valdez-Taubas, J., and H.R. Pelham. 2003. Curr. Biol. 13:1636–1640). Here, we found that polarization of Fus1p, a raft-associated type I transmembrane protein involved in cell fusion, does not depend on endocytosis. Instead, Fus1p localization to the tip of the mating projection was determined by its cytosolic domain, which binds to peripheral proteins involved in mating tip polarization. Furthermore, we provide evidence that the lipid bilayer at the mating projection is more condensed than the plasma membrane enclosing the cell body, and that sphingolipids are required for this lipid organization.

Sign in / Sign up

Export Citation Format

Share Document