scholarly journals Saccharomyces cerevisiae, a model to study sterol uptake and transport in eukaryotes

2005 ◽  
Vol 33 (5) ◽  
pp. 1186-1188 ◽  
Author(s):  
S. Reiner ◽  
D. Micolod ◽  
R. Schneiter
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Intracellular Transport ◽  
Molecular Mechanisms ◽  
Unsaturated Fatty Acids ◽  
Eukaryotic Cells ◽  
Lipid Uptake ◽  
Anaerobic Conditions ◽  
Transport Pathway ◽  
Uptake And Transport ◽  
Mutant Collection

The molecular mechanisms that govern intracellular transport of sterols in eukaryotic cells are only poorly understood. Saccharomyces cerevisiae is a facultative anaerobic organism that requires supplementation with unsaturated fatty acids and sterols to grow in the absence of oxygen, as the synthesis of these lipids requires molecular oxygen. The fact that yeast grows well under anaerobic conditions indicates that lipid uptake is rapid and efficient. To identify components in this lipid uptake and transport pathway, we screened the yeast mutant collection for genes that are essential under anaerobic conditions. Out of the approx. 4800 non-essential genes represented in the mutant collection, 37 were required for growth under anaerobic conditions. Uptake assays using radiolabelled cholesterol revealed that 16 of these genes are required for cholesterol uptake/transport and esterification. Further characterization of the precise role of these genes is likely to advance our understanding of this elusive pathway in yeast and may prove to be relevant to understand sterol homoeostasis in higher eukaryotic cells.

Uptake and intracellular transport of the connective tissue growth factor: a potential mode of action

2001 ◽  
Vol 359 (1) ◽  
pp. 89-97 ◽  
Author(s):  
Nadia Abdel WAHAB ◽  
Heike BRINKMAN ◽  
Roger M. MASON
Keyword(s):  
Growth Factor ◽  
Connective Tissue ◽  
Connective Tissue Growth Factor ◽  
Intracellular Transport ◽  
Molecular Mechanisms ◽  
Mesangial Cells ◽  
Tissue Growth ◽  
Transport Pathway ◽  
Potential Mode ◽  
Fibrotic Disorders

Connective tissue growth factor (CTGF) is a secreted cysteine-rich protein now considered as an important effector molecule in both physiological and pathological processes. An increasing amount of evidence indicates that CTGF plays a key role in the pathogenesis of different fibrotic disorders including diabetic nephropathy. However, the molecular mechanisms by which CTGF exerts its effects are not known. Here we provide the first evidence for the existence of an intracellular transport pathway for the growth factor in human mesangial cells. Our results demonstrate that CTGF is internalized from the cell surface in endosomes and accumulates in a juxtanuclear organelle from which the growth factor is then translocated into the cytosol. In the cytosol CTGF is phosphorylated by protein kinase C and PMA treatment can enhance this phosphorylation. Phosphorylated CTGF may have an important role in the cytosol, but it is also translocated into the nucleus where it may directly affect transcription.

scholarly journals Tritium Suicide Selection Identifies Proteins Involved in the Uptake and Intracellular Transport of Sterols in Saccharomyces cerevisiae

2008 ◽  
Vol 8 (2) ◽  
pp. 161-169 ◽  
Author(s):  
David P. Sullivan ◽  
Alexander Georgiev ◽  
Anant K. Menon
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Abc Transporters ◽  
Intracellular Transport ◽  
Cytoplasmic Protein ◽  
Intracellular Accumulation ◽  
Transport Pathway ◽  
Sterol Transport ◽  
Sterol Uptake ◽  
Transposon Insertions

ABSTRACT Sterol transport between the plasma membrane (PM) and the endoplasmic reticulum (ER) occurs by a nonvesicular mechanism that is poorly understood. To identify proteins required for this process, we isolated Saccharomyces cerevisiae mutants with defects in sterol transport. We used Upc2-1 cells that have the ability to take up sterols under aerobic conditions and exploited the observation that intracellular accumulation of exogenously supplied [3H]cholesterol in the form of [3H]cholesteryl ester requires an intact PM-ER sterol transport pathway. Upc2-1 cells were mutagenized using a transposon library, incubated with [3H]cholesterol, and subjected to tritium suicide selection to isolate mutants with a decreased ability to accumulate [3H]cholesterol. Many of the mutants had defects in the expression and trafficking of Aus1 and Pdr11, PM-localized ABC transporters that are required for sterol uptake. Through characterization of one of the mutants, a new role was uncovered for the transcription factor Mot3 in controlling expression of Aus1 and Pdr11. A number of mutants had transposon insertions in the uncharacterized Ydr051c gene, which we now refer to as DET1 (decreased ergosterol transport). These mutants expressed Aus1 and Pdr11 normally but were severely defective in the ability to accumulate exogenously supplied cholesterol. The transport of newly synthesized sterols from the ER to the PM was also defective in det1Δ cells. These data indicate that the cytoplasmic protein encoded by DET1 is involved in intracellular sterol transport.

scholarly journals Specifically Targeted Transport of Plasma Membrane Transporters: From Potential Mechanisms for Regulating Cell Health or Disease to Applications

Membranes ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 736
Author(s):  
Yeqing He ◽  
Guandi He ◽  
Tengbing He
Keyword(s):  
Membrane Protein ◽  
Intracellular Transport ◽  
Molecular Mechanisms ◽  
Reference Value ◽  
Membrane Transporters ◽  
Transport Pathway ◽  
Disease Treatment ◽  
Recognition Mechanism ◽  
Substrate Transport ◽  
Pathogen Invasion

Normal substrate transport and signal transmission are the premise to ensure the health of biological somatic cells. Therefore, a comprehensive understanding of the molecular mechanism of intercellular substrate transport is of great significance for clinical treatment. In order to better understand the membrane protein through its interaction with receptors, to help maintain a healthy cell and the molecular mechanisms of disease, in this paper, we seek to clarify, first of all, the recognition mechanism for different types of membrane protein receptors; pathogen invasion using the transport pathway involved in the membrane; and the latest specific target sites of various kinds of membrane transport carriers; to provide an explanation and summary of the system. Secondly, the downstream receptor proteins and specific substrates of different membrane transporters were classified systematically; the functional differences of different subclasses and their relationship with intracellular transport disorders were analyzed to further explore the potential relationship between cell transport disorders and diseases. Finally, the paper summarizes the use of membrane transporter-specific targets for drug design and development from the latest research results; it points out the transporter-related results in disease treatment; the application prospects and the direction for drug development and disease treatment providing a new train of thought; also for disease-specific targeted therapy, it provides a certain reference value.

scholarly journals A Genomewide Screen Reveals a Role of Mitochondria in Anaerobic Uptake of Sterols in Yeast

2006 ◽  
Vol 17 (1) ◽  
pp. 90-103 ◽  
Author(s):  
Sonja Reiner ◽  
Delphine Micolod ◽  
Günther Zellnig ◽  
Roger Schneiter
Keyword(s):  
Mitochondrial Function ◽  
Membrane Trafficking ◽  
Intracellular Transport ◽  
Unsaturated Fatty Acids ◽  
Cell Fractionation ◽  
Anaerobic Conditions ◽  
Cellular Functions ◽  
Sterol Uptake ◽  
Mitochondrial Functions ◽  
Wide Range

The mechanisms that govern intracellular transport of sterols in eukaryotic cells are not well understood. Saccharomyces cerevisiae is a facultative anaerobic organism that becomes auxotroph for sterols and unsaturated fatty acids in the absence of oxygen. To identify pathways that are required for uptake and transport of sterols, we performed a systematic screen of the yeast deletion mutant collection for genes that are required for growth under anaerobic conditions. Of the ∼4800 nonessential genes represented in the deletion collection, 37 were essential for growth under anaerobic conditions. These affect a wide range of cellular functions, including biosynthetic pathways for certain amino acids and cofactors, reprogramming of transcription and translation, mitochondrial function and biogenesis, and membrane trafficking. Thirty-three of these mutants failed to grow on lipid-supplemented media when combined with a mutation in HEM1, which mimics anaerobic conditions in the presence of oxygen. Uptake assays with radio- and fluorescently labeled cholesterol revealed that 17 of the 33 mutants strongly affect uptake and/or esterification of exogenously supplied cholesterol. Examination of the subcellular distribution of sterols in these uptake mutants by cell fractionation and fluorescence microscopy indicates that some of the mutants block incorporation of cholesterol into the plasma membrane, a presumably early step in sterol uptake. Unexpectedly, the largest class of uptake mutants is affected in mitochondrial functions, and many of the uptake mutants show electron-dense mitochondrial inclusions. These results indicate that a hitherto uncharacterized mitochondrial function is required for sterol uptake and/or transport under anaerobic conditions and are discussed in light of the fact that mitochondrial import of cholesterol is required for steroidogenesis in vertebrate cells.

scholarly journals Quality control in the secretory assembly line

2001 ◽  
Vol 356 (1406) ◽  
pp. 147-150 ◽  
Author(s):  
Ari Helenius
Keyword(s):  
Quality Control ◽  
Control System ◽  
Intracellular Transport ◽  
Secretory Pathway ◽  
Molecular Mechanisms ◽  
Assembly Line ◽  
Eukaryotic Cells ◽  
Unfolded Proteins ◽  
Different Types ◽  
Sorting System

As a rule, only proteins that have reached a native, folded and assembled structure are transported to their target organelles and compartments within the cell. In the secretory pathway of eukaryotic cells, this type of sorting is particularly important. A variety of molecular mechanisms are involved that distinguish between folded and unfolded proteins, modulate their intracellular transport, and induce degradation if they fail to fold. This phenomenon, called quality control, occurs at several levels and involves different types of folding sensors. The quality control system provides a stringent and versatile molecular sorting system that guaranties fidelity of protein expression in the secretory pathway.

scholarly journals Mitochondrial Dynamics, ROS, and Cell Signaling: A Blended Overview

Life ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 332
Author(s):  
Valentina Brillo ◽  
Leonardo Chieregato ◽  
Luigi Leanza ◽  
Silvia Muccioli ◽  
Roberto Costa
Keyword(s):  
Molecular Mechanisms ◽  
Mitochondrial Dynamics ◽  
Eukaryotic Cells ◽  
Therapeutic Approaches ◽  
Cellular Functions ◽  
Lipid Trafficking ◽  
Mitochondrial Ros ◽  
Intracellular Organelles ◽  
Proliferation Regulation ◽  
Dynamic Plasticity

Mitochondria are key intracellular organelles involved not only in the metabolic state of the cell, but also in several cellular functions, such as proliferation, Calcium signaling, and lipid trafficking. Indeed, these organelles are characterized by continuous events of fission and fusion which contribute to the dynamic plasticity of their network, also strongly influenced by mitochondrial contacts with other subcellular organelles. Nevertheless, mitochondria release a major amount of reactive oxygen species (ROS) inside eukaryotic cells, which are reported to mediate a plethora of both physiological and pathological cellular functions, such as growth and proliferation, regulation of autophagy, apoptosis, and metastasis. Therefore, targeting mitochondrial ROS could be a promising strategy to overcome and hinder the development of diseases such as cancer, where malignant cells, possessing a higher amount of ROS with respect to healthy ones, could be specifically targeted by therapeutic treatments. In this review, we collected the ultimate findings on the blended interplay among mitochondrial shaping, mitochondrial ROS, and several signaling pathways, in order to contribute to the dissection of intracellular molecular mechanisms involved in the pathophysiology of eukaryotic cells, possibly improving future therapeutic approaches.

scholarly journals Moving toward molecular mechanisms for chemotaxis in eukaryotic cells

2019 ◽  
Vol 30 (23) ◽  
pp. 2873-2877
Author(s):  
Peter Devreotes
Keyword(s):  
Molecular Mechanisms ◽  
Eukaryotic Cells ◽  
To Receive

It is a tremendous honor to receive the 2019 E.B. Wilson Award and be recognized for my work on chemotaxis in eukaryotic cells. In writing this essay, I hope to achieve three aims: 1) to tell the story of how people in my group made discoveries over the years; 2) to outline key principles we have learned about chemotaxis; and 3) to point to the most important outstanding questions.

scholarly journals Feeding a Saccharomyces cerevisiae fermentation product improves udder health and immune response to a Streptococcus uberis mastitis challenge in mid-lactation dairy cows

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
M. Vailati-Riboni ◽  
D. N. Coleman ◽  
V. Lopreiato ◽  
A. Alharthi ◽  
R. E. Bucktrout ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Somatic Cell ◽  
Pathway Analysis ◽  
Molecular Mechanisms ◽  
Somatic Cell Score ◽  
Molecular Networks ◽  
Epithelial Tissue ◽  
Udder Health ◽  
Streptococcus Uberis ◽  
Fermentation Product

Abstract Background We aimed to characterize the protective effects and the molecular mechanisms of action of a Saccharomyces cerevisiae fermentation product (NTK) in response to a mastitis challenge. Eighteen mid-lactation multiparous Holstein cows (n = 9/group) were fed the control diet (CON) or CON supplemented with 19 g/d NTK for 45 d (phase 1, P1) and then infected in the right rear quarter with 2500 CFU of Streptococcus uberis (phase 2, P2). After 36-h, mammary gland and liver biopsies were collected and antibiotic treatment started until the end of P2 (9 d post challenge). Cows were then followed until day 75 (phase 3, P3). Milk yield (MY) and dry matter intake (DMI) were recorded daily. Milk samples for somatic cell score were collected, and rectal and udder temperature, heart and respiration rate were recorded during the challenge period (P2) together with blood samples for metabolite and immune function analyses. Data were analyzed by phase using the PROC MIXED procedure in SAS. Biopsies were used for transcriptomic analysis via RNA-sequencing, followed by pathway analysis. Results DMI and MY were not affected by diet in P1, but an interaction with time was recorded in P2 indicating a better recovery from the challenge in NTK compared with CON. NTK reduced rectal temperature, somatic cell score, and temperature of the infected quarter during the challenge. Transcriptome data supported these findings, as NTK supplementation upregulated mammary genes related to immune cell antibacterial function (e.g., CATHL4, NOS2), epithelial tissue protection (e.g. IL17C), and anti-inflammatory activity (e.g., ATF3, BAG3, IER3, G-CSF, GRO1, ZFAND2A). Pathway analysis indicated upregulation of tumor necrosis factor α, heat shock protein response, and p21 related pathways in the response to mastitis in NTK cows. Other pathways for detoxification and cytoprotection functions along with the tight junction pathway were also upregulated in NTK-fed cows. Conclusions Overall, results highlighted molecular networks involved in the protective effect of NTK prophylactic supplementation on udder health during a subclinical mastitic event.

scholarly journals Prohibitins Regulate Membrane Protein Degradation by the m-AAA Protease in Mitochondria

1999 ◽  
Vol 19 (5) ◽  
pp. 3435-3442 ◽  
Author(s):  
Gregor Steglich ◽  
Walter Neupert ◽  
Thomas Langer
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Growth ◽  
Membrane Proteins ◽  
Eukaryotic Cells ◽  
Mitochondrial Morphology ◽  
Regulatory Effect ◽  
Inner Membrane ◽  
Functional Activities ◽  
Native Molecular Mass ◽  
Affect Cell Growth

ABSTRACT Prohibitins comprise a protein family in eukaryotic cells with potential roles in senescence and tumor suppression. Phb1p and Phb2p, members of the prohibitin family in Saccharomyces cerevisiae, have been implicated in the regulation of the replicative life span of the cells and in the maintenance of mitochondrial morphology. The functional activities of these proteins, however, have not been elucidated. We demonstrate here that prohibitins regulate the turnover of membrane proteins by the m-AAA protease, a conserved ATP-dependent protease in the inner membrane of mitochondria. The m-AAA protease is composed of the homologous subunits Yta10p (Afg3p) and Yta12p (Rca1p). Deletion ofPHB1 or PHB2 impairs growth of Δyta10 or Δyta12 cells but does not affect cell growth in the presence of the m-AAA protease. A prohibitin complex with a native molecular mass of approximately 2 MDa containing Phb1p and Phb2p forms a supercomplex with them-AAA protease. Proteolysis of nonassembled inner membrane proteins by the m-AAA protease is accelerated in mitochondria lacking Phb1p or Phb2p, indicating a negative regulatory effect of prohibitins on m-AAA protease activity. These results functionally link members of two conserved protein families in eukaryotes to the degradation of membrane proteins in mitochondria.

Analysis of Saccharomyces cerevisiae his3 transcription in vitro: biochemical support for multiple mechanisms of transcription

1990 ◽  
Vol 10 (6) ◽  
pp. 2832-2839
Author(s):  
A S Ponticelli ◽  
K Struhl
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcriptional Activation ◽  
Transcription Initiation ◽  
Molecular Mechanisms ◽  
Initiation Site ◽  
Activator Proteins ◽  
Nuclear Extracts ◽  
Transcription In Vitro

The promoter region of the Saccharomyces cerevisiae his3 gene contains two TATA elements, TC and TR, that direct transcription initiation to two sites designated +1 and +13. On the basis of differences between their nucleotide sequences and their responsiveness to upstream promoter elements, it has previously been proposed that TC and TR promote transcription by different molecular mechanisms. To begin a study of his3 transcription in vitro, we used S. cerevisiae nuclear extracts together with various DNA templates and transcriptional activator proteins that have been characterized in vivo. We demonstrated accurate transcription initiation in vitro at the sites used in vivo, transcriptional activation by GCN4, and activation by a GAL4 derivative on various gal-his3 hybrid promoters. In all cases, transcription stimulation was dependent on the presence of an acidic activation region in the activator protein. In addition, analysis of promoters containing a variety of TR derivatives indicated that the level of transcription in vitro was directly related to the level achieved in vivo. The results demonstrated that the in vitro system accurately reproduced all known aspects of in vivo his3 transcription that depend on the TR element. However, in striking contrast to his3 transcription in vivo, transcription in vitro yielded approximately 20 times more of the +13 transcript than the +1 transcript. This result was not due to inability of the +1 initiation site to be efficiently utilized in vitro, but rather it reflects the lack of TC function in vitro. The results support the idea that TC and TR mediate transcription from the wild-type promoter by distinct mechanisms.

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