scholarly journals A Cytoplasmic GOLD Protein Controls Cell Polarity

2018 ◽  
Author(s):  
Deike J. Omnus ◽  
Angela Cadou ◽  
Gary H.C. Chung ◽  
Jakob M. Bader ◽  
Christopher J. Stefan
Keyword(s):  
Plasma Membrane ◽  
Phase Transitions ◽  
Cell Polarity ◽  
General Mechanism ◽  
Kinase Activation ◽  
Polarized Secretion ◽  
Phosphoinositide Phosphatase ◽  
Mother Cells ◽  
Intracellular Aggregates ◽  
Phosphatidylinositol 4

AbstractPhosphoinositide lipids provide spatial landmarks during polarized secretion. Here, we elucidate a role for phosphatidylinositol 4-phosphate (PI4P) metabolism in the control of cell polarity. In budding yeast, PI4P is enriched at the plasma membrane of growing daughter cells. Upon heat shock however, PI4P rapidly increases at the plasma membrane in mother cells resulting in a more uniform PI4P distribution. Rather than phosphoinositide kinase activation, PI4P hydrolysis is impaired to generate the heat-induced PI4P signal in mother cells. This fine tune control of PI4P metabolism is mediated through attenuation of the Osh3 protein that binds and presents PI4P to a phosphoinositide phosphatase. Importantly, Osh3 undergoes phase transitions upon environmental stress conditions, resulting in intracellular aggregates and reduced cortical localization. The chaperone Hsp104 co-assembles with intracellular Osh3 granules, but is not required for their formation. Interestingly, the Osh3 GOLD domain, also present in the ER-localized p24 cargo adaptor family, is sufficient to form stress granules. Accordingly, GOLD-mediated phase transitions may provide a general mechanism to modulate secretion and growth upon transient changes in physiological and environmental conditions.

Coupled sterol synthesis and transport machineries at ER–endocytic contact sites

2021 ◽  
Vol 220 (10) ◽  
Author(s):  
Javier Encinar del Dedo ◽  
Isabel María Fernández-Golbano ◽  
Laura Pastor ◽  
Paula Meler ◽  
Cristina Ferrer-Orta ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Actin Polymerization ◽  
Sterol Synthesis ◽  
Biosynthetic Enzymes ◽  
Cellular Membranes ◽  
Contact Sites ◽  
Endocytic Machinery ◽  
Mother Cells

Sterols are unevenly distributed within cellular membranes. How their biosynthetic and transport machineries are organized to generate heterogeneity is largely unknown. We previously showed that the yeast sterol transporter Osh2 is recruited to endoplasmic reticulum (ER)–endocytic contacts to facilitate actin polymerization. We now find that a subset of sterol biosynthetic enzymes also localizes at these contacts and interacts with Osh2 and the endocytic machinery. Following the sterol dynamics, we show that Osh2 extracts sterols from these subdomains, which we name ERSESs (ER sterol exit sites). Further, we demonstrate that coupling of the sterol synthesis and transport machineries is required for endocytosis in mother cells, but not in daughters, where plasma membrane loading with accessible sterols and endocytosis are linked to secretion.

scholarly journals The a-factor transporter (STE6 gene product) and cell polarity in the yeast Saccharomyces cerevisiae.

1993 ◽  
Vol 120 (5) ◽  
pp. 1203-1215 ◽  
Author(s):  
K Kuchler ◽  
H G Dohlman ◽  
J Thorner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Gene Product ◽  
Cell Polarity ◽  
Polyclonal Antibodies ◽  
Apparent Molecular Weight ◽  
Subcellular Fractionation ◽  
Mating Pheromone ◽  
Yeast Saccharomyces Cerevisiae ◽  
Factor Secretion

STE6 gene product is required for secretion of the lipopeptide mating pheromone a-factor by Saccharomyces cerevisiae MATa cells. Radiolabeling and immunoprecipitation, either with specific polyclonal antibodies raised against a TrpE-Ste6 fusion protein or with mAbs that recognize c-myc epitopes in fully functional epitope-tagged Ste6 derivatives, demonstrated that Ste6 is a 145-kD phosphoprotein. Subcellular fractionation, various extraction procedures, and immunoblotting showed that Ste6 is an intrinsic plasma membrane-associated protein. The apparent molecular weight of Ste6 was unaffected by tunicamycin treatment, and the radiolabeled protein did not bind to concanavalin A, indicating that Ste6 is not glycosylated and that glycosylation is not required either for its membrane delivery or its function. The amino acid sequence of Ste6 predicts two ATP-binding folds; correspondingly, Ste6 was photoaffinity-labeled specifically with 8-azido-[alpha-32P]ATP. Indirect immunofluorescence revealed that in exponentially growing MATa cells, the majority of Ste6 showed a patchy distribution within the plasma membrane, but a significant fraction was found concentrated in a number of vesicle-like bodies subtending the plasma membrane. In contrast, in MATa cells exposed to the mating pheromone alpha-factor, which markedly induced Ste6 production, the majority of Ste6 was incorporated into the plasma membrane within the growing tip of the elongating cells. The highly localized insertion of this transporter may establish pronounced anisotropy in a-factor secretion from the MATa cell, and thereby may contribute to the establishment of the cell polarity which restricts partner selection and cell fusion during mating to one MAT alpha cell.

scholarly journals ORP2 Delivers Cholesterol to the Plasma Membrane in Exchange for Phosphatidylinositol 4, 5-Bisphosphate (PI(4,5)P2)

2019 ◽  
Vol 73 (3) ◽  
pp. 458-473.e7 ◽  
Author(s):  
Huan Wang ◽  
Qianli Ma ◽  
Yanfei Qi ◽  
Jiangqing Dong ◽  
Ximing Du ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Phosphatidylinositol 4

scholarly journals Electrostatic plasma membrane targeting contributes to Dlg function in cell polarity and tumorigenesis

Development ◽  
2021 ◽  
pp. dev.196956
Author(s):  
Juan Lu ◽  
Wei Dong ◽  
Yan Tao ◽  
Yang Hong
Keyword(s):  
Plasma Membrane ◽  
Tumor Suppressor ◽  
Epithelial Cells ◽  
Cell Polarity ◽  
Significant Role ◽  
Discs Large ◽  
Cortical Localization ◽  
Polarity Proteins ◽  
Positively Charged

Discs large (Dlg) is an essential polarity protein and a tumor suppressor originally characterized in Drosophila but is also well conserved in vertebrates. Like the majority of polarity proteins, plasma membrane (PM)/cortical localization of Dlg is required for its function in polarity and tumorigenesis, but the exact mechanisms targeting Dlg to PM remain to be fully elucidated. Here we show that, similar to the recently discovered polybasic polarity proteins such as Lgl and aPKC, Dlg also contains a positively charged polybasic domain that electrostatically binds the PM phosphoinositides PI4P and PI(4,5)P2. Electrostatic targeting by the polybasic domain contributes significantly to the PM localization of Dlg in follicular and early embryonic epithelial cells, and is crucial for Dlg to regulate both polarity and tumorigenesis. The electrostatic PM targeting of Dlg is controlled by a potential phosphorylation-dependent allosteric regulation of its polybasic domain, and is specifically enhanced by the interactions between Dlg and another basolateral polarity protein and tumor suppressor Scrib. Our studies highlight an increasingly significant role of electrostatic PM targeting of polarity proteins in regulating cell polarity.

scholarly journals Functions for Cdc42p BEM Adaptors in Regulating a Differentiation-Type MAP Kinase Pathway

2019 ◽  
Author(s):  
Sukanya Basu ◽  
Beatriz González ◽  
Boyang Li ◽  
Garrett Kimble ◽  
Keith G. Kozminski ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Polarity ◽  
Rho Gtpase ◽  
Mapk Pathway ◽  
Mitogen Activated Protein Kinase ◽  
List Type ◽  
Activation Kinetics ◽  
Closed Conformation ◽  
Mapk Pathways ◽  
Effector Pathways

ABSTRACTRho GTPases regulate cell polarity and signal transduction pathways to control morphogenetic responses in different settings. In yeast, the Rho GTPase Cdc42p regulates cell polarity, and through the p21-activated kinase Ste20p, Cdc42p also regulates mitogen-activated protein kinase (MAPK) pathways (mating, filamentous growth or fMAPK, and HOG). Although much is known about how Cdc42p regulates cell polarity and the mating pathway, how Cdc42p regulates the fMAPK pathway is not clear. To address this question, Cdc42p-dependent MAPK pathways were compared in the filamentous (∑1278b) strain background. Each MAPK pathway showed a unique activation profile, with the fMAPK pathway exhibiting slow activation kinetics compared to the mating and HOG pathways. A previously characterized version of Cdc42p, Cdc42pE100A, that is specifically defective for fMAPK pathway signaling, was defective for interaction with Bem4p, the pathway-specific adaptor for the fMAPK pathway. Corresponding residues in Bem4p were identified that were required for interaction with Cdc42p and fMAPK pathway signaling. The polarity adaptor Bem1p also regulated the fMAPK pathway. In the fMAPK pathway, Bem1p recruited Ste20p to the plasma membrane, cycled between an open and closed conformation, and interacted with the GEF for Cdc42, Cdc24p. Bem1p also regulated effector pathways in different ways, behaving as a multi-functional adaptor in some pathways and an inert scaffold in others. Genetic suppression tests showed that Bem4p and Bem1p regulate the fMAPK pathway in an ordered sequence. Collectively, the study demonstrates unique and sequential functions for Rho GTPase adaptors in regulating MAPK pathways.HIGHLIGHTSComparing Cdc42p-dependent MAPK pathways showed that the fMAPK pathway had slow activation kinetics compared to the mating and HOG pathways.A collection of cdc42 alleles was tested for MAPK pathway functions. § Cdc42pE100A, previously characterized as being specifically defective for fMAPK signaling, showed reduced interaction with the fMAPK pathway adaptor Bem4p.§ Corresponding residues in Bem4p were identified that were required for interaction with Cdc42p and fMAPK signaling.The polarity adaptor Bem1p regulated the fMAPK pathway. § Bem1p regulated the fMAPK pathway by recruiting Ste20p to the plasma membrane, cycling between an open and closed conformation, and interacting with the Cdc42p GEF, Cdc24p.Different domains of Bem1p had different roles in regulating effector pathways. § Bem1p may function as a multi-functional adaptor in some pathways and an inert scaffold in others.Bem4p and Bem1p regulated the fMAPK pathway in an ordered sequence. § The data support a model where Bem4p recruits Cdc24p to GDP-Cdc42p, and Bem1p directs GTP-Cdc42p to Ste20p at the plasma membrane.§ The bud-site GTPase Rsr1p regulates Cdc24p in the fMAPK pathway but does not initiate signaling.

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