TORC1 ensures membrane trafficking of Tat2 tryptophan permease via a novel transcriptional activator Vhr2 in budding yeast.

The target of rapamycin complex 1 (TORC1) protein kinase is activated by nutrients and controls nutrient uptake via the membrane trafficking of various nutrient permeases. However, its molecular mechanisms remain elusive. Cholesterol (ergosterol in yeast) in conjunction with sphingolipids forms tight-packing microdomains, "lipid rafts", which are critical for intracellular protein sorting.

A subcellular proteome atlas of the yeast Komagataella phaffii.

The compartmentalization of metabolic and regulatory pathways is a common pattern of living organisms. Eukaryotic cells are subdivided into several organelles enclosed by lipid membranes. Organelle proteomes define their functions.

The lipid droplet protein Pgc1 controls the subcellular distribution of phosphatidylglycerol.

The biosynthesis of yeast phosphatidylglycerol (PG) takes place in the inner mitochondrial membrane. Outside mitochondria, the abundance of PG is low. Here, we present evidence that the subcellular distribution of PG is maintained by the locally controlled enzymatic activity of the PG-specific phospholipase, Pgc1.

The role of the membrane lipid composition in the oxidative stress tolerance of different wine yeasts.

Oxidative stress is a common stress in yeasts during the stages of the winemaking process in which aerobic growth occurs, and it can modify the cellular lipid composition. The aim of this study was to evaluate the oxidative stress tolerance of two non-conventional yeasts (Torulaspora delbrueckii and Metschnikowia pulcherrima) compared to Saccharomyces cerevisiae. Therefore, their resistance against HO, the ROS production and the cellular lipid composition were assessed.

Melatonin Minimizes the Impact of Oxidative Stress Induced by Hydrogen Peroxide in and Non-conventional Yeast.

Melatonin (-acetyl-5-methoxytryptamine) is synthesized from tryptophan by and non-conventional yeast species. Antioxidant properties have been suggested as a possible role of melatonin in a wine strain. However, the possible antioxidant melatonin effect on non- species and other strains of must be evaluated.

Identification and characterization of the mitochondrial membrane sorting signals in phosphatidylserine decarboxylase 1 from Saccharomyces cerevisiae.

Phosphatidylserine decarboxylase 1 (Psd1p) catalyzes the formation of the majority of phosphatidylethanolamine (PE) in the yeast Saccharomyces cerevisiae. Psd1p is localized to mitochondria, anchored to the inner mitochondrial membrane (IMM) through membrane spanning domains and oriented towards the mitochondrial intermembrane space. We found that Psd1p harbors at least two inner membrane-associated domains, which we named IM1 and IM2.

Steryl ester synthesis, storage and hydrolysis: A contribution to sterol homeostasis.

Sterols are essential lipids of all eukaryotic cells, appearing either as free sterols or steryl esters. Besides other regulatory mechanisms, esterification of sterols and hydrolysis of steryl esters serve to buffer both an excess and a lack of free sterols. In this review, the esterification process, the storage of steryl esters and their mobilization will be described.

The impact of nonpolar lipids on the regulation of the steryl ester hydrolases Tgl1p and Yeh1p in the yeast Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae degradation of steryl esters is catalyzed by the steryl ester hydrolases Tgl1p, Yeh1p and Yeh2p. The two steryl ester hydrolases Tgl1p and Yeh1p localize to lipid droplets, a cell compartment storing steryl esters and triacylglycerols. In the present study we investigated regulatory aspects of these two hydrolytic enzymes, namely the gene expression level, protein amount, stability and enzyme activity of Tgl1p and Yeh1p in strains lacking both or only one of the two major nonpolar lipids, steryl esters and triacylglycerols.

The effect of hypoxia on the lipidome of recombinant Pichia pastoris.

Background: Cultivation of recombinant Pichia pastoris (Komagataella sp.) under hypoxic conditions has a strong positive effect on specific productivity when the glycolytic GAP promoter is used for recombinant protein expression, mainly due to upregulation of glycolytic conditions. In addition, transcriptomic analyses of hypoxic P.

Involvement of a putative substrate binding site in the biogenesis and assembly of phosphatidylserine decarboxylase 1 from Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae, the mitochondrial phosphatidylserine decarboxylase 1 (Psd1p) produces the largest amount of cellular phosphatidylethanolamine (PE). Psd1p is synthesized as a larger precursor on cytosolic ribosomes and then imported into mitochondria in a three-step processing event leading to the formation of an α-subunit and a β-subunit. The α-subunit harbors a highly conserved motif, which was proposed to be involved in phosphatidylserine (PS) binding.

Phosphatidylcholine Affects Inner Membrane Protein Translocases of Mitochondria.

Two protein translocases transport precursor proteins into or across the inner mitochondrial membrane. The presequence translocase (TIM23 complex) sorts precursor proteins with a cleavable presequence either into the matrix or into the inner membrane. The carrier translocase (TIM22 complex) inserts multispanning proteins into the inner membrane.

Regulation of the yeast triacylglycerol lipases Tgl4p and Tgl5p by the presence/absence of nonpolar lipids.

Tgl3p, Tgl4p, and Tgl5p are the major triacylglycerol lipases of the yeast Saccharomyces cerevisiae Recently we demonstrated that properties of Tgl3p are regulated by the formation of nonpolar lipids. The present study extends these investigations to the two other yeast triacylglycerol lipases, Tgl4p and Tgl5p. We show that Tgl4p and Tgl5p, which are localized to lipid droplets in wild type, are partially retained in the endoplasmic reticulum in cells lacking triacylglycerols and localize exclusively to the endoplasmic reticulum in a mutant devoid of lipid droplets.

A novel mechanism for the biogenesis of outer membrane vesicles in Gram-negative bacteria.

Bacterial outer membrane vesicles (OMVs) have important biological roles in pathogenesis and intercellular interactions, but a general mechanism of OMV formation is lacking. Here we show that the VacJ/Yrb ABC (ATP-binding cassette) transport system, a proposed phospholipid transporter, is involved in OMV formation. Deletion or repression of VacJ/Yrb increases OMV production in two distantly related Gram-negative bacteria, Haemophilus influenzae and Vibrio cholerae.

Systems-level organization of yeast methylotrophic lifestyle.

Background: Some yeasts have evolved a methylotrophic lifestyle enabling them to utilize the single carbon compound methanol as a carbon and energy source. Among them, Pichia pastoris (syn. Komagataella sp.

Phosphatidylcholine affects the role of the sorting and assembly machinery in the biogenesis of mitochondrial β-barrel proteins.

Two protein translocases drive the import of β-barrel precursor proteins into the mitochondrial outer membrane: The translocase of the outer membrane (TOM complex) promotes transport of the precursor to the intermembrane space, whereas the sorting and assembly machinery (SAM complex) mediates subsequent folding of the β-barrel and its integration into the target membrane. The non-bilayer-forming phospholipids phosphatidylethanolamine (PE) and cardiolipin (CL) are required for the biogenesis of β-barrel proteins. Whether bilayer-forming phospholipids such as phosphatidylcholine (PC), the most abundant phospholipid of the mitochondrial outer membrane, play a role in the import of β-barrel precursors is unclear.

A Yeast Mutant Deleted of GPH1 Bears Defects in Lipid Metabolism.

In a previous study we demonstrated up-regulation of the yeast GPH1 gene under conditions of phosphatidylethanolamine (PE) depletion caused by deletion of the mitochondrial (M) phosphatidylserine decarboxylase 1 (PSD1) (Gsell et al., 2013, PLoS One. 8(10):e77380.

Phosphatidylcholine Supply to Peroxisomes of the Yeast Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae, phosphatidylcholine (PC), the major phospholipid (PL) of all organelle membranes, is synthesized via two different pathways. Methylation of phosphatidylethanolamine (PE) catalyzed by the methyl transferases Cho2p/Pem1p and Opi3p/Pem2p as well as incorporation of choline through the CDP (cytidine diphosphate)-choline branch of the Kennedy pathway lead to PC formation. To determine the contribution of these two pathways to the supply of PC to peroxisomes (PX), yeast mutants bearing defects in the two pathways were cultivated under peroxisome inducing conditions, i.

Regulatory link between steryl ester formation and hydrolysis in the yeast Saccharomyces cerevisiae.

Steryl esters and triacylglycerols are the major storage lipids of the yeast Saccharomyces cerevisiae. Steryl esters are formed in the endoplasmic reticulum by the two acyl-CoA:sterol acyltransferases Are1p and Are2p, whereas steryl ester hydrolysis is catalyzed by the three steryl ester hydrolases Yeh1p, Yeh2p and Tgl1p. To shed light on the regulatory link between steryl ester formation and hydrolysis in the maintenance of cellular sterol and free fatty acid levels we employed yeast mutants which lacked the enzymes catalyzing the degradation of steryl esters.

A basis for vaccine development: Comparative characterization of Haemophilus influenzae outer membrane vesicles.

Outer membrane vesicles (OMVs) are spherical and bilayered particles that are naturally released from the outer membrane (OM) of Gram-negative bacteria. They have been proposed to possess several biological roles in pathogenesis and interbacterial interactions. Additionally, OMVs have been suggested as potential vaccine candidates against infections caused by pathogenic bacteria like Haemophilus influenzae, a human pathogen of the respiratory tract.

Defects in triacylglycerol lipolysis affect synthesis of triacylglycerols and steryl esters in the yeast.

Tgl3p, Tgl4p and Tgl5p are the major triacylglycerol lipases of the yeast Saccharomyces cerevisiae catalyzing degradation of triacylglycerols stored in lipid droplets. Previous results from our laboratory (Athenstaedt and Daum, 2005, J. Biol.

Modifications of the C terminus affect functionality and stability of yeast triacylglycerol lipase Tgl3p.

Lipid droplets are specific organelles for the storage of triacylglycerols and steryl esters. They are surrounded by a phospholipid monolayer with a small but specific set of proteins embedded. Assembly and insertion of proteins into this surface membrane is an intriguing question of lipid droplet biology.

Isolation and characterization of the plasma membrane from the yeast Pichia pastoris.

Despite similarities of cellular membranes in all eukaryotes, every compartment displays characteristic and often unique features which are important for the functions of the specific organelles. In the present study, we biochemically characterized the plasma membrane of the methylotrophic yeast Pichia pastoris with emphasis on the lipids which form the matrix of this compartment. Prerequisite for this effort was the design of a standardized and reliable isolation protocol of the plasma membrane at high purity.

Storage lipids of yeasts: a survey of nonpolar lipid metabolism in Saccharomyces cerevisiae, Pichia pastoris, and Yarrowia lipolytica.

Biosynthesis and storage of nonpolar lipids, such as triacylglycerols (TG) and steryl esters (SE), have gained much interest during the last decades because defects in these processes are related to severe human diseases. The baker's yeast Saccharomyces cerevisiae has become a valuable tool to study eukaryotic lipid metabolism because this single-cell microorganism harbors many enzymes and pathways with counterparts in mammalian cells. In this article, we will review aspects of TG and SE metabolism and turnover in the yeast that have been known for a long time and combine them with new perceptions of nonpolar lipid research.