Biology subjects

Renne, M. F.

Publications and source records attributed to Renne, M. F..

5 recordsLinked to original sources

bioRxiv2025

Laboratory yeast strains are highly diverse in lipid metabolism

The impact of the genetic background on the lipidome of yeast strains remains underexplored. This study systematically compares the lipidomes of five commonly used laboratory yeast strains: BY4741, W303, D273-10B, RM11-1a, and CEN.PK2-1c. Shotgun lipidomics reveals significant variations in lipid class and acyl chain composition down to the level of molecular species. Notably, the most abundant lipid class differed between the strains: phosphatidylinositol (PI) lipids are predominant in BY4741, while phosphatidylethanolamine (PE) lipids are in D273. Ergosterol esters, which are the storage form of the major yeast sterol ergosterol, are at higher levels in all strains other than BY4741, correlating with a low gene expression of lipid metabolic enzymes Hmg1 and Are2 in BY4741. Despite these lipidomic differences, transcriptomic analysis did not show significant changes in most genes related to lipid metabolism, suggesting post-transcriptional modifications, protein abundance, and metabolic flux as potential regulatory mechanisms. This study underscores the complexity of lipidome regulation and the need for further investigation into the underlying mechanisms.

biochemistry↗

bioRxiv2024

Reversible tuning of membrane sterol levels by cyclodextrin in a dialysis setting

Large unilamellar vesicles (LUVs) are popular membrane models for studying the impact of lipids and bilayer properties on the structure and function of individual membrane proteins. The functional reconstitution of transmembrane in liposomes can be challenging, especially, if the hydrophobic thickness of the protein does not match the thickness of the surrounding lipid bilayer. During the reconstitution procedure Such hydrophobic mismatch causes low yields and protein aggregation, which are exacerbated in sterol-rich membranes featuring low membrane compressibility. Here, we explore new approaches to reversibly tune membrane sterol contents proteoliposomes after their formation. Both cholesterol delivery and extraction are mediated by methyl-{beta}-cyclodextrin in a dialysis setting, which maintains (proteo)liposomes in a confined compartment. This makes it possible to reversibly tune the cholesterol level without losing membrane material simply by placing the dialysis cassette in a new bath containing either empty or cholesterol-loaded methyl-{beta}-cyclodextrin. Cholesterol delivery and removal is monitored with the solvatochromic probe C-Laurdan, which reports on lipid packing. Using Forster-resonance energy transfer, we show that cholesterol delivery to proteoliposomes induces the oligomerization of a membrane property sensor, while the subsequent removal of cholesterol demonstrates the full reversibility. We propose that tuning membrane compressibility by methyl-{beta}-cyclodextrin-meditated cholesterol delivery and removal in a dialysis setup provides a new handle to study its impact on membrane protein structure, function, and dynamics. Statement of significanceGenerating complex, sterol-rich, biomimetic membranes for studying the structure and function of reconstituted membrane proteins is challenging. As an important step towards asymmetric, sterol-rich, complex model membrane systems, we have established a procedure to control the membrane sterol level of liposomes and proteoliposomes using methyl-{beta}-cyclodextrin in a dialysis setup. We demonstrate the feasibility of this approach by C-Laurdan and dehydroergosterol fluorescence spectroscopy and gain control over the membrane sterol content. We explore several parameters that affect the rate of cholesterol delivery and show that the oligomerization of a membrane property sensor, which is on the unfolded protein response sensor protein Ire1, is controlled by the sterol content of the surrounding lipid bilayer.

biophysics↗

bioRxiv2024

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

The budding yeast Saccharomyces cerevisiae 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 in yeast have described changes in the phospholipid composition at the level of sum composition (e.g. PC 32:1) and molecular composition (e.g. PC 16:0_16:1). However, to date, there is no information at the level of positional isomers (e.g. PC 16:0/16:1 versus PC 16:1/16:0). In this study, combined Collision- and Ozone-Induced Dissociation (CID/OzID) mass spectrometry was deployed to investigate homeoviscous adaptation of PC, PE, and PS sn-molecular species composition. We determined the main species to be 16:1/16:1, 16:0/16:1, 16:1/18:1, 16:0/18:1, and 18:0/16:1. In general, at higher culture temperature, the sn-1 position is increased in saturated acyl chains, whereas the sn-2 position mainly is increased in acyl chain length. PC mainly increases in 16:0/16:1 and 16:0/18:1, at the expense of 16:1/16:1, whereas PS and PE increase in 16:1/18:1, at the expense of 16:1/16:1 and 16:0/16:1. Our data suggest distinct adaptation mechanisms of the sn-1 and sn-2 acyl chains, and different manners of sn-molecular species adaptation between PC and PE/PS.

biochemistry↗

bioRxiv2021

Acyl chain shortening induced by inhibition of acetyl-CoA carboxylase renders phosphatidylcholine redundant

Phosphatidylcholine (PC) is an abundant membrane lipid component in most eukaryotes including yeast. PC has been assigned a multitude of functions in addition to that of building block of the lipid bilayer. Here we show that PC is evolvable essential in yeast by isolating suppressor mutants devoid of PC that exhibit robust growth. The requirement for PC is suppressed by monosomy of chromosome XV, or by a point mutation in the ACC1 gene encoding acetyl-CoA carboxylase. Although these two genetic adaptations rewire lipid biosynthesis differently, both decrease Acc1 activity thereby reducing the average acyl chain length. Accordingly, soraphen A, a specific inhibitor of Acc1, rescues a yeast mutant with deficient PC synthesis. In the aneuploid suppressor, up-regulation of lipid synthesis is instrumental to accomplish feed-back inhibition of Acc1 by acyl-CoA produced by the fatty acid synthase (FAS). The results show that yeast regulates acyl chain length by fine-tuning the activities of Acc1 and FAS, and indicate that PC evolved by benefitting the maintenance of membrane fluidity.

biochemistry↗

bioRxiv2020

Molecular species selectivity of lipid transport creates a mitochondrial sink for di-unsaturated phospholipids

Mitochondria depend on the import of phospholipid precursors for the biosynthesis of the non-bilayer lipids phosphatidylethanolamine (PE) and cardiolipin required for proper function, yet the mechanism of lipid import remains elusive. Pulse labeling yeast with stable isotope-labeled serine followed by mass spectrometry analysis revealed that mitochondria preferentially import di-unsaturated phosphatidylserine (PS) for conversion to PE by the mitochondrial PS decarboxylase Psd1p. Several protein complexes tethering mitochondria to the endomembrane system have been implicated in lipid transport in yeast, including the endoplasmic reticulum (ER)-mitochondrial encounter structure (ERMES), ER-mitochondria complex (EMC) and the vacuole and mitochondria patch (vCLAMP). By limiting the availability of unsaturated phospholipids through overexpression of the glycerol-3-phosphate acyltransferase Sct1p, conditions were created to investigate the mechanism of lipid transfer and the contribution of the tethering complexes in vivo. Under these conditions, inactivation of ERMES components or the vCLAMP component Vps39p exacerbated the lipid phenotype, indicating that ERMES and Vps39 contribute to the mitochondrial sink for unsaturated acyl chains by mediating transfer of di-unsaturated phospholipids. The results support the concept that intermembrane lipid flow is rate-limited by molecular species-dependent lipid efflux from the donor membrane and driven by the lipid species concentration gradient between donor and acceptor membrane.

biochemistry↗