Temperature adaptation of yeast phospholipid molecular species at the acyl chain positional level.

Yeast is a poikilothermic organism and adapts its lipid composition to the environmental temperature to maintain membrane physical properties. Studies addressing temperature-dependent adaptation of the lipidome have described changes in the phospholipid composition at the level of sum composition (e.g.

Shortening of membrane lipid acyl chains compensates for phosphatidylcholine deficiency in choline-auxotroph yeast.

Phosphatidylcholine (PC) is an abundant membrane lipid component in most eukaryotes, including yeast, and has been assigned multiple functions in addition to acting as building block of the lipid bilayer. Here, by isolating S. cerevisiae suppressor mutants that exhibit robust growth in the absence of PC, we show that PC essentiality is subject to cellular evolvability in yeast.

In Vivo Assessment of Thermosensitive Liposomes for the Treatment of Port Wine Stains by Antifibrinolytic Site-Specific Pharmaco-Laser Therapy.

Antifibrinolytic site-specific pharmaco-laser therapy (SSPLT) is an experimental treatment modality for refractory port wine stains (PWS). Conceptually, antifibrinolytic drugs encapsulated in thermosensitive liposomes are delivered to thrombi that form in semi-photocoagulated PWS blood vessels after conventional laser treatment. Local release of antifibrinolytics is induced by mild hyperthermia, resulting in hyperthrombosis and complete occlusion of the target blood vessel (clinical endpoint).

Water soluble lipid precursor contaminants in yeast culture medium ingredients.

The presence of the water soluble glycerophospholipid precursors choline and inositol in culture media highly affects lipid biosynthesis and regulation thereof. We report that widely used media ingredients contain trace amounts of choline and inositol that are not mentioned on the product label, influencing experimental outcome.

The topology of the ER-resident phospholipid methyltransferase Opi3 of is consistent with in catalysis.

Phospholipid -methyltransferases (PLMTs) synthesize phosphatidylcholine by methylating phosphatidylethanolamine using -adenosylmethionine as a methyl donor. Eukaryotic PLMTs are integral membrane enzymes located in the endoplasmic reticulum (ER). Recently Opi3, a PLMT of the yeast was proposed to perform in catalysis, while localized in the ER, Opi3 would methylate lipid substrates located in the plasma membrane at membrane contact sites.

Phospholipid turnover and acyl chain remodeling in the yeast ER.

The turnover of phospholipids plays an essential role in membrane lipid homeostasis by impacting both lipid head group and acyl chain composition. This review focusses on the degradation and acyl chain remodeling of the major phospholipid classes present in the ER membrane of the reference eukaryote Saccharomyces cerevisiae, i.e.

The glycerophosphocholine acyltransferase Gpc1 is part of a phosphatidylcholine (PC)-remodeling pathway that alters PC species in yeast.

Phospholipase B-mediated hydrolysis of phosphatidylcholine (PC) results in the formation of free fatty acids and glycerophosphocholine (GPC) in the yeast GPC can be reacylated by the glycerophosphocholine acyltransferase Gpc1, which produces lysophosphatidylcholine (LPC), and LPC can be converted to PC by the lysophospholipid acyltransferase Ale1. Here, we further characterized the regulation and function of this distinct PC deacylation/reacylation pathway in yeast. Through and experiments, we show that Gpc1 and Ale1 are the major cellular GPC and LPC acyltransferases, respectively.

The role of phospholipid molecular species in determining the physical properties of yeast membranes.

In most eukaryotes, including Saccharomyces cerevisiae, glycerophospholipids are the main membrane lipid constituents. Besides serving as general membrane 'building blocks', glycerophospholipids play an important role in determining the physical properties of the membrane, which are crucial for proper membrane function. To ensure optimal physical properties, membrane glycerophospholipid composition and synthesis are tightly regulated.

Lipidomics in research on yeast membrane lipid homeostasis.

Mass spectrometry is increasingly used in research on membrane lipid homeostasis, both in analyses of the steady state lipidome at the level of molecular lipid species, and in pulse-chase approaches employing stable isotope-labeled lipid precursors addressing the dynamics of lipid metabolism. Here my experience with, and view on mass spectrometry-based lipid analysis is presented, with emphasis on aspects of quantification of membrane lipid composition of the yeast Saccharomyces cerevisiae. This article is part of a Special Issue entitled: BBALIP_Lipidomics Opinion Articles edited by Sepp Kohlwein.

Lipid Acyl Chain Remodeling in Yeast.

Membrane lipid homeostasis is maintained by de novo synthesis, intracellular transport, remodeling, and degradation of lipid molecules. Glycerophospholipids, the most abundant structural component of eukaryotic membranes, are subject to acyl chain remodeling, which is defined as the post-synthetic process in which one or both acyl chains are exchanged. Here, we review studies addressing acyl chain remodeling of membrane glycerophospholipids in Saccharomyces cerevisiae, a model organism that has been successfully used to investigate lipid synthesis and its regulation.

Phosphatidylcholine's functions beyond that of a membrane brick.

Since its discovery in the 19th century, phosphatidylcholine (PC) has been regarded primarily as a structural lipid. However, more recent evidence, much of it in the last five years, strongly suggests that PC has other roles. Here, we explore some of that new evidence and consider the possibility that the ultimate role of phosphatidylcholine may not be predictable.

E. coli MG1655 modulates its phospholipid composition through the cell cycle.

This paper describes a study of the phospholipid profile of Escherichia coli MG1655 cultures at the B and D periods of the cell cycle. The results indicate that the phosphatidyl glycerol fraction grows relatively rapidly and that the size of the cardiolipin (CL) fraction does not grow at all during cell elongation. This is consistent with observations that CL is located preferentially at the poles of E.

Ligation strategies for targeting liposomal nanocarriers.

Liposomes have been exploited for pharmaceutical purposes, including diagnostic imaging and drug and gene delivery. The versatility of liposomes as drug carriers has been demonstrated by a variety of clinically approved formulations. Since liposomes were first reported, research of liposomal formulations has progressed to produce improved delivery systems.

Checks and balances in membrane phospholipid class and acyl chain homeostasis, the yeast perspective.

Glycerophospholipids are the most abundant membrane lipid constituents in most eukaryotic cells. As a consequence, phospholipid class and acyl chain homeostasis are crucial for maintaining optimal physical properties of membranes that in turn are crucial for membrane function. The topic of this review is our current understanding of membrane phospholipid homeostasis in the reference eukaryote Saccharomyces cerevisiae.

Plasma membrane--endoplasmic reticulum contact sites regulate phosphatidylcholine synthesis.

Synthesis of phospholipids, sterols and sphingolipids is thought to occur at contact sites between the endoplasmic reticulum (ER) and other organelles because many lipid-synthesizing enzymes are enriched in these contacts. In only a few cases have the enzymes been localized to contacts in vivo and in no instances have the contacts been demonstrated to be required for enzyme function. Here, we show that plasma membrane (PM)--ER contact sites in yeast are required for phosphatidylcholine synthesis and regulate the activity of the phosphatidylethanolamine N-methyltransferase enzyme, Opi3.

Yeast cells accumulate excess endogenous palmitate in phosphatidylcholine by acyl chain remodeling involving the phospholipase B Plb1p.

In the yeast Saccharomyces cerevisiae, the molecular species profile of the major membrane glycerophospholipid phosphatidylcholine (PC) is determined by the molecular species-selectivity of the biosynthesis routes and by acyl chain remodeling. Overexpression of the glycerol-3-phosphate acyltransferase Sct1p was recently shown to induce a strong increase in the cellular content of palmitate (C16:0). Using stable isotope labeling and mass spectrometry, the present study shows that wild type yeast overexpressing Sct1p incorporates excess C16:0 into PC via the methylation of PE, the CDP-choline route, and post-synthetic acyl chain remodeling.

The yeast acyltransferase Sct1p regulates fatty acid desaturation by competing with the desaturase Ole1p.

The degree of fatty acid unsaturation, that is, the ratio of unsaturated versus saturated fatty acyl chains, determines membrane fluidity. Regulation of expression of the fatty acid desaturase Ole1p was hitherto the only known mechanism governing the degree of fatty acid unsaturation in Saccharomyces cerevisiae. We report a novel mechanism for the regulation of fatty acid desaturation that is based on competition between Ole1p and the glycerol-3-phosphate acyltransferase Sct1p/Gat2p for the common substrate C16:0-CoA.

Quantitative profiling of PE, MMPE, DMPE, and PC lipid species by multiple precursor ion scanning: a tool for monitoring PE metabolism.

We report a method for the simultaneous identification and quantification of phosphatidylethanolamine (PE), monomethyl-phosphatidylethanolamine (MMPE), dimethyl-phosphatidylethanolamine (DMPE), and phosphatidylcholine (PC) species in lipid extracts. The method employs a specific "mass-tag" strategy where DMPE, MMPE, and PE species are chemically methylated with deuterated methyliodide (CD(3)I) to produce PC molecules having class-specific mass offsets of 3, 6 and 9Da, respectively. The derivatized aminoglycerophospholipids release characteristic phosphorylcholine-like fragment ions having specific mass offsets that powers sensitive and quantitative analysis by multiple precursor ion scanning on a hybrid quadrupole time-of-flight mass spectrometer.

Proteome-wide detection of phospholipid-protein interactions in mitochondria by photocrosslinking and click chemistry.

Photoactivatable lipid analogues are uniquely suited for the detection of lipid-protein interactions in biological membranes. Based on photocrosslinking, new methodology has been developed for the proteome-wide detection of lipid-protein interactions. Bifunctional lipid analogues containing a tag for click chemistry in addition to the photoactivatable moiety enable the enrichment of the crosslinked proteins that is required for subsequent identification by mass spectrometry.

The influence of the acyl chain composition of cardiolipin on the stability of mitochondrial complexes; an unexpected effect of cardiolipin in alpha-ketoglutarate dehydrogenase and prohibitin complexes.

The role of cardiolipin acyl chain composition in assembly/stabilization of mitochondrial complexes was investigated using three yeast deletion mutants (acb1Delta strain; taz1Delta strain; and acb1Deltataz1Delta strain). Deletion of the TAZ1 gene, involved in cardiolipin acyl chain remodeling, is known to increase the content of monolyso-cardiolipin (MLCL) at the expense of CL, and to decrease the unsaturation of the remaining CL. Deletion of the ACB1 gene encoding the acyl-CoA-binding protein, involved in fatty acid elongation, decreases the average length of the CL acyl chains.

Nanocapsules of platinum anticancer drugs: development towards therapeutic use.

Platinum-based anticancer agents have been widely used in the clinic to successfully treat many different types of cancer. However, the therapeutic efficacy of platinum drugs is limited by serious side effects and the occurrence of inherent or acquired resistance of tumor cells. Nanoparticulate drug-delivery systems have the potential to reduce side effects and circumvent drug resistance.

Cardiolipin molecular species with shorter acyl chains accumulate in Saccharomyces cerevisiae mutants lacking the acyl coenzyme A-binding protein Acb1p: new insights into acyl chain remodeling of cardiolipin.

The function of the mitochondrial phospholipid cardiolipin (CL) is thought to depend on its acyl chain composition. The present study aims at a better understanding of the way the CL species profile is established in Saccharomyces cerevisiae by using depletion of the acyl-CoA-binding protein Acb1p as a tool to modulate the cellular acyl chain content. Despite the presence of an intact CL remodeling system, acyl chains shorter than 16 carbon atoms (C16) were found to accumulate in CL in cells lacking Acb1p.

On the interaction of fluorophore-encapsulating PEGylated lecithin liposomes with hamster and human platelets.

Polyethylene glycol (PEG)-grafted phosphatidylcholine liposomes are used as drug carriers due to their low immunogenicity and prolonged circulation time. The interaction between sterically stabilized lecithin liposomes and platelets has not been investigated before, and deserves to be subjected to scrutiny inasmuch as the uptake of liposomes by platelets could be detrimental for drug delivery and primary hemostasis. Consequently, the interaction between resting and convulxin-activated hamster and human platelets and calcein- or 5,6-carboxyfluorescein-encapsulating PEGylated liposomes composed of distearoyl- and dipalmitoyl phosphatidylcholine and PEG-derivatized distearoyl phosphatidylethanolamine was investigated by flow cytometry, confocal microscopy, and a glass capillary thrombosis model.