Integration Of Transport Pathways In Saccharomyces Cerevisiae
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Integration Of Transport Pathways In Saccharomyces Cerevisiae
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Author : Jesper Johansen
language : en
Publisher:
Release Date : 2017
Integration Of Transport Pathways In Saccharomyces Cerevisiae written by Jesper Johansen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Plasma membrane (PM) homeostasis is essential for viability and depends on maintaining a constant balance between the amount of membrane material arriving at the cell cortex and the amount recycled. This membrane transport is mediated by two distinct mechanisms: (i) vesicular transport, utilizing membrane-enclosed vesicles for bulk transport of membrane proteins and lipids; and (ii) non-vesicular lipid transport. While the molecular mechanisms of these processes are well defined, they are generally considered independent events but how they are integrated is poorly understood. To gain insight into how these transport pathways are coordinated at the PM, three avenues of research were conducted using a combination of genetic, biochemical and live-cell microscopy assays. First, I showed that the Oxysterol-binding protein-related protein (ORP) Osh4p, implicated in non-vesicular sterol transfer, was found to associate with exocytic vesicles and formed complexes with regulators of polarized exocytosis, including the small GTPases Sec4p, Cdc42p, and Rho1p. Second, I tested the function of the evolutionarily conserved endoplasmic reticulum (ER)-associated protein Arv1p, also suggested to be involved in non-vesicular sterol transfer. Ultimately Arv1p was found to be dispensable for sterol exchange between the ER and PM but instead it was shown to play an important role in maintaining ER ultrastructure; Arv1p might be involved in regulating insertion of tail-anchored proteins into membranes. Finally, the essential yeast Rab GTPase Sec4p, principally known to be a key regulator of exocytosis, was shown to mechanistically couple polarized exocytosis with cortical actin polymerization, which activates Las17p (the yeast Wiskott-Aldrich syndrome [WASp])-dependent endocytosis. Las17p activation results in actin filament nucleation, which pulls the PM inward for endocytic vesicle biogenesis. Sec4p thereby represents the first direct regulatory link that couples exocytosis and endocytosis, which we termed \"yeast compensatory endocytosis.\" By identifying novel mechanisms that coordinate intracellular transport pathways, these studies provided important new insights into how PM homeostasis is regulated and maintained.
Integration Of Transport Pathways In Yeast
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Author : Gabriel Alfaro
language : en
Publisher:
Release Date : 2012
Integration Of Transport Pathways In Yeast written by Gabriel Alfaro and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Carrier proteins categories.
Cell polarity is maintained via a balance of exocytosis and endocytosis; the protein machinery that mediates these transport processes must be co-ordinated with membrane lipid signals. This lipid signalling is, in part, dependent on the establishment of membrane domains through lipid transport. Cholesterol is transported via a poorly defined route that is independent of vesicle-mediated secretory protein transport. This "non-vesicular" sterol transport is postulated to involve the conserved family of Oxysterol binding protein (OSBP) Related Proteins (ORPs), which are proposed to be sterol lipid transport proteins (LTPs). To test if ORPs primarily act as sterol LTPs or alternatively as sterol-responsive signalling proteins, the function of Saccharomyces cerevisiae OSBP Homologues (OSH1-OSH7) were analyzed. Depletion of all Osh proteins in yeast cells inhibited growth, and defects in endocytosis, polarized exocytosis, and sterol homeostasis, were observed. Consistent with a direct role in exocytosis, Oshdepletion disrupted the polarized localization of vesicle transport regulators (Rho- and Rab-GTPases, and exocyst complex subunits) and the Osh protein Osh4p was observed to travel on exocytic vesicles to sites of polarized growth. Osh4p also formed complexes in vivo with specific Rho- and Rab-GTPases, and exocyst complex subunits. Contrary to the postulated role of ORPs as LTPs, a designed mutation in Osh4p that disrupts its ability to bind and thereby transport sterols, did not inactivate the protein but caused a gain-of-function phenotype affecting exocytosis. Our experiments suggested that ORPs are not sterol LTPs and implied that sterols act as signalling ligands that repress Osh4p, and potentially other ORPs. To understand how Osh proteins might simultaneously affect both exocytosis and endocytosis, I tested whether the regulation of the exocytic and endocytic machinery are directly coupled. I found that the Rab GTPase Sec4p, which is an integral component of exocytosis, directly interacted with specific endocytic proteins at actin patches. SEC4 was required for proper endocytic site assembly and actin patch polarization, indicating that Sec4p links exocytosis and endocytosis to maintain cell polarization. Because these novel mechanisms involving sterol signalling and cell polarization are likely to be conserved, I propose these studies have broader medical implications applicable to cancer cell growth and metastasis.
Systematic Analysis Of Protein Transport Pathways In Saccharomyces Cerevisiae
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Author : Sebastian Eising
language : en
Publisher:
Release Date : 2021
Systematic Analysis Of Protein Transport Pathways In Saccharomyces Cerevisiae written by Sebastian Eising and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
Molecular Requirements For Protein Transport To The Endosome And Vacuole In Saccharomyces Cerevisiae
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Author : Stephanie E. Rieder
language : en
Publisher:
Release Date : 1998
Molecular Requirements For Protein Transport To The Endosome And Vacuole In Saccharomyces Cerevisiae written by Stephanie E. Rieder and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1998 with categories.
Investigating Signaling Pathway Integration In Saccharomyces Cerevisiae On An Alternative Carbon Source To Coordinate Growth Metabolism And Stress Defense
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Author : Ellen Renee Wagner
language : en
Publisher:
Release Date : 2023
Investigating Signaling Pathway Integration In Saccharomyces Cerevisiae On An Alternative Carbon Source To Coordinate Growth Metabolism And Stress Defense written by Ellen Renee Wagner and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
Due to its relative ease, microbial engineering is invaluable for applied research focused on product formation, particularly for biofuel production. The budding yeast Saccharomyces cerevisiae is an ideal organism for biofuel-based engineering due to its genetic tractability, well researched biology, and preference for fermentation. Even with these advantages, two large bottlenecks for sustainable biofuel production remain. First, when lignocellulosic biomass is broken down, it releases several sugars, the majority being glucose and xylose. While many microorganisms, including yeast, can readily ferment glucose, they lack the ability to ferment the pentose sugar xylose. Second, the process of breaking down lignocellulosic material introduces toxic chemicals into the resulting hydrolysate. These toxins inhibit microbial growth and metabolism, specifically limiting pentose utilization in engineered strains. Through collaborative efforts, we identified loss-of-function mutations in the stress-responsive MAP kinase HOG1 and negative regulator of the RAS/Protein Kinase A (PKA) pathway, IRA2, among other minimal genetic changes, enhances anaerobic xylose fermentation. However, these mutations likely reduce cells' ability to tolerate the toxins present in lignocellulosic hydrolysate, making the strain especially vulnerable to it. As these mutations impact broadly acting signaling networks, the physiological changes required for robust xylose fermentation are unclear. Previously, we generated a strain capable of rapid xylose fermentation with minimal growth by deleting the PKA regulatory subunit BCY1 in the presence of wildtype IRA2 and HOG1. Past work found these strains co-activate the alternative carbon source Snf1 pathway with the PKA pathway to enable xylose utilization. This present a unique model in which to study the integration of three highly conserved signaling pathways for the utilization of a non-native carbon source in the presence of environmental stressors. In chapter 2, we test the contributions of Hog1 and PKA signaling via IRA2 or BCY1 to metabolism, growth, and stress tolerance in mixed sugar media. In chapter 3, we use a multi-omics approach to develop models for how cells coordinate growth, metabolism, and other responses in budding yeast and how restructuring these processes enables anaerobic xylose utilization.
Inferring Stress Activated Signaling Networks In Saccharomyces Cerevisiae Reveals Complex Pathway Integration
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Author : Matthew Edward MacGilvray
language : en
Publisher:
Release Date : 2017
Inferring Stress Activated Signaling Networks In Saccharomyces Cerevisiae Reveals Complex Pathway Integration written by Matthew Edward MacGilvray and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Cells respond to stressful conditions by coordinating a complex, multi-faceted response that spans many levels of physiology. Much of the response is coordinated by changes in protein phosphorylation. Although the regulators of transcriptome changes during stress are well characterized in Saccharomyces cerevisiae, the upstream regulatory network controlling protein phosphorylation is less well dissected. In this thesis, we developed a computational approach to infer the stress-activated signaling network that regulates phosphorylation changes in response to salt stress and the ER stressor dithiothreitol (DTT). The method uses integer linear programming (ILP) to integrate stress-responsive phospho-proteome responses in wild-type and mutant strains, predicted phosphorylation motifs on groups of coregulated peptides, and published protein interaction data. The inferred salt-network predicted new regulatory connections between stress-activated and growth-regulating pathways and suggested mechanisms coordinating metabolism, cell-cycle progression, and growth during stress. Further, kinase inference during DTT suggested new functions for the HOG and PKA pathways in augmenting the unfolded protein response (UPR). Together, our work shows how a high-quality computational network model can facilitate discovery of new pathway interactions during diverse stress responses.
The Sac1p An Integral Membrane Protein Involved In Secretory Pathway Function And Actin Function In Saccharomyces Cerevisiae
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Author : Ann Elizabeth Cleves
language : en
Publisher:
Release Date : 1992
The Sac1p An Integral Membrane Protein Involved In Secretory Pathway Function And Actin Function In Saccharomyces Cerevisiae written by Ann Elizabeth Cleves and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992 with categories.
The secretory pathway of the yeast Saccharomyces cerevisiae is strictly analogous to that of mammalian cells. Proteins destined for secretion are transported in a vectorial fashion from the endoplasmic reticulum to the Golgi apparatus to the cell surface. Superimposed on the normal flow of secretory traffic in yeast is a level of spatial organization. Golgi-derived secretory vesicles are directed to a defined region of the mother cell surface known as the bud. During the budding portion of the cell cycle, secretion and cell surface growth are coincident which results in the selective growth of the bud. The actin cytoskeleton has been implicated as the mediator of the polarized mode of yeast cell growth. The filamentous actin cytoskeleton consists of two structures, asymmetrically-arranged cortical patches and cables which are aligned along the mother cell-bud axis. Structural analyses indicated that the patches could participate in localized membrane growth while the cables are correctly positioned to be involved in directed vesicular transport. Given the proposed relationship between secretion and actin, it seems reasonable that there would be communication between the secretory pathway and the actin cytoskeleton in yeast. Presented in this thesis is evidence that the S. cerevisiae SAC1 gene product could represent one aspect of the mechanism for coupling secretory pathway function and actin assembly in yeast. Mutations in SAC1 were isolated as extragenic suppressors of both Golgi and actin defects. Analysis of the SAC1 gene product revealed that the SAC1p was a 71kD integral membrane protein that exhibited a small cytoplasmic domain. The SAC1p localized to yeast ER and Golgi membranes, but showed no obvious association with the filamentous actin cytoskeleton. Native immunoprecipitation experiments suggested that the SAC1p was an actin binding protein in yeast. Finally, a model is proposed which reconciles how the SAC1p could be involved in the activities of both the secretory pathway and actin cytoskeleton, thereby rendering the SAC1p capable of participating in the spatial restriction imposed on secretory traffic in yeast.
Identification And Characterization Of Factors Involved In The Ap 3 Dependent Protein Transport Pathway Of Saccharomyces Cerevisiae
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Author : Vikram Campbell Anand
language : en
Publisher:
Release Date : 2008
Identification And Characterization Of Factors Involved In The Ap 3 Dependent Protein Transport Pathway Of Saccharomyces Cerevisiae written by Vikram Campbell Anand and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
Characterization Of The Cytoplasm To Vacuole Targeting Pathways In Saccharomyces Cerevisiae
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Author : Ju Guan
language : en
Publisher:
Release Date : 2002
Characterization Of The Cytoplasm To Vacuole Targeting Pathways In Saccharomyces Cerevisiae written by Ju Guan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with categories.
Characterization Of Vacuolar Membrane Protein Transport In Saccharomyces Cerevisiae
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Author : Christopher Rollefson Cowles
language : en
Publisher:
Release Date : 1998
Characterization Of Vacuolar Membrane Protein Transport In Saccharomyces Cerevisiae written by Christopher Rollefson Cowles and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1998 with categories.