Lipid landscapes and pipelines in membrane homeostasis

Defects in integrin complex formation promote CHKB-mediated muscular dystrophy

Phosphatidylcholine (PC) is the major membrane phospholipid in most eukaryotic cells. Bi-allelic loss of function variants in CHKB, encoding the first step in the synthesis of PC, is the cause of a rostrocaudal muscular dystrophy in both humans and mice. Loss of sarcolemma integrity is a hallmark of muscular dystrophies; however, how this occurs in the absence of choline kinase function is not known. We determine that in Chkb -/- mice there is a failure of the α7β1 integrin complex that is specific to affected muscle. We observed that in Chkb -/- hindlimb muscles there is a decrease in sarcolemma association/abundance of the PI(4,5)P2 binding integrin complex proteins vinculin, and α-actinin, and a decrease in actin association with the sarcolemma. In cells, pharmacological inhibition of choline kinase activity results in internalization of a fluorescent PI(4,5)P2 reporter from discrete plasma membrane clusters at the cell surface membrane to cytosol, this corresponds with a decreased vinculin localization at plasma membrane focal adhesions that was rescued by overexpression of CHKB.

Structure of the endosomal CORVET tethering complex

Cells depend on their endolysosomal system for nutrient uptake and downregulation of plasma membrane proteins. These processes rely on endosomal maturation, which requires multiple membrane fusion steps. Early endosome fusion is promoted by the Rab5 GTPase and its effector, the hexameric CORVET tethering complex, which is homologous to the lysosomal HOPS. How these related complexes recognize their specific target membranes remains entirely elusive. Here, we solve the structure of CORVET by cryo-electron microscopy and revealed its minimal requirements for membrane tethering. As expected, the core of CORVET and HOPS resembles each other. However, the function-defining subunits show marked structural differences. Notably, we discover that unlike HOPS, CORVET depends not only on Rab5 but also on phosphatidylinositol-3-phosphate (PI3P) and membrane lipid packing defects for tethering, implying that an organelle-specific membrane code enables fusion. Our data suggest that both shape and membrane interactions of CORVET and HOPS are conserved in metazoans, thus providing a paradigm how tethering complexes function.

Ratiometric fluorescence nanoscopy and lifetime imaging of novel Nile Red analogs for analysis of membrane packing in living cells

Subcellular membranes have complex lipid and protein compositions, which give rise to organelle-specific membrane packing, fluidity, and permeability. Due to its exquisite solvent sensitivity, the lipophilic fluorescence dye Nile Red has been used extensively to study membrane packing and polarity. Further improvement of Nile Red can be achieved by introducing electron-donating or withdrawing functional groups. Here, we compare the potential of derivatives of Nile Red with such functional substitutions for super-resolution fluorescence microscopy of lipid packing in model membranes and living cells. All studied Nile Red derivatives exhibit cholesterol-dependent fluorescence changes in model membranes, as shown by spectrally resolved stimulated emission depletion (STED) microscopy. STED imaging of Nile Red probes in cells reveals lower membrane packing in fibroblasts from healthy subjects compared to those from patients suffering from Niemann Pick type C1 (NPC1) disease, a lysosomal storage disorder with accumulation of cholesterol and sphingolipids in late endosomes and lysosomes. We also find small but consistent changes in the fluorescence lifetime of the Nile Red derivatives in NPC1 cells, suggesting altered hydrogen-bonding capacity in their membranes. All Nile Red derivatives are essentially non-fluorescent in water but increase their brightness in membranes, allowing for their use in MINFLUX single molecule tracking experiments. Our study uncovers the potential of Nile Red probes with functional substitutions for nanoscopic membrane imaging.

StarD5 levels of expression correlate with onset and progression of steatosis and liver fibrosis

Insufficient expression of steroidogenic acute regulatory-related lipid transfer protein 5 (StarD5) on liver cholesterol/lipid homeostasis is not clearly defined. The ablation of StarD5 was analyzed in mice on a normal or Western diet (WD) to determine its importance in hepatic lipid accumulation and fibrosis compared with wild-type (WT) mice. Rescue experiments in StarD5-/- mice and hepatocytes were performed. In addition to increased hepatic triglyceride (TG)-cholesterol levels, global StarD5-/- mice fed a normal diet displayed reduced plasma triglycerides and liver very low-density lipoprotein (VLDL) secretion as compared with WT counterparts. Insulin levels and homeostatic model assessment for insulin resistance (HOMA-IR) scoring were elevated, demonstrating developing insulin resistance (IR). WD-fed StarD5-/- mice upregulated WW domain containing transcription regulator 1 (TAZ or WWTR1) expression with accelerated liver fibrosis when compared with WD-fed WT mice. Suppression of oxysterol 7α-hydroxylase (CYP7B1) coupled with chronic accumulation of toxic oxysterol levels correlated with presentation of fibrosis. "Hepatocyte-selective" StarD5 overexpression in StarD5-/- mice restored expression, reduced hepatic triglycerides, and improved HOMA-IR. Observations in two additional mouse and one human metabolic dysfunction-associated steatotic liver disease (MASLD) model were supportive. The downregulation of StarD5 with hepatic lipid excess is a previously unappreciated physiological function appearing to promote lipid storage for future needs. Conversely, lingering downregulation of StarD5 with prolonged lipid-cholesterol excess accelerates fatty liver's transition to fibrosis; mediated via dysregulation in the oxysterol signaling pathway.NEW & NOTEWORTHY We have found that deletion of the cholesterol transport protein StarD5 in mice leads to an increase in insulin resistance and lipid accumulation due to the upregulation of lipid synthesis and decrease VLDL secretion from the liver. In addition, deletion of StarD5 increased fibrosis when mice were fed a Western diet. This represents a novel pathway of fibrosis development in the liver.

Lipids and proteins: Insights into the dynamics of assembly, recognition, condensate formation. What is still missing?

Lipid membranes and proteins, which are part of us throughout our lives, have been studied for decades. However, every year, new discoveries show how little we know about them. In a reader-friendly manner for people not involved in the field, this paper tries to serve as a bridge between physicists and biologists and new young researchers diving into the field to show its relevance, pointing out just some of the plethora of lines of research yet to be unraveled. It illustrates how new ways, from experimental to theoretical approaches, are needed in order to understand the structures and interactions that take place in a single lipid, protein, or multicomponent system, as we are still only scratching the surface.

How ceramides affect the development of colon cancer: from normal colon to carcinoma

The integrity of the colon and the development of colon cancer depend on the sphingolipid balance in colon epithelial cells. In this review, we summarize the current knowledge on how ceramides and their complex derivatives influence normal colon development and colon cancer development. Ceramides, glucosylceramides and sphingomyelin are essential membrane components and, due to their biophysical properties, can influence the activation of membrane proteins, affecting protein-protein interactions and downstream signalling pathways. Here, we review the cellular mechanisms known to be affected by ceramides and their effects on colon development. We also describe which ceramides are deregulated during colorectal carcinogenesis, the molecular mechanisms involved in ceramide deregulation and how this affects carcinogenesis. Finally, we review new methods that are now state of the art for studying lipid-protein interactions in the physiological environment.

Microcystin-LR (MC-LR) inhibits green algae growth by regulating antioxidant and photosynthetic systems

Microcystins release from bloom-forming cyanobacteria is considered a way to gain competitive advantage in Microcystis populations, which threaten water resources security and aquatic ecological balance. However, the effects of microcystins on microalgae are still largely unclear. Through simulated culture experiments and the use of UHPLC-MS-based metabolomics, the effects of two microcystin-LR (MC-LR) concentrations (400 and 1,600 μg/L) on the growth and antioxidant properties of three algae species, the toxic Microcystis aeruginosa, a non-toxic Microcystis sp., and Chlorella vulgaris, were studied. The MC-LR caused damage to the photosynthetic system and activated the protective mechanism of the photosynthetic system by decreasing the chlorophyll-a and carotenoid concentrations. Microcystins triggered oxidative stress in C. vulgaris, which was the most sensitive algae species studied, and secreted more glycolipids into the extracellular compartment, thereby destroying its cell structure. However, C. vulgaris eliminated reactive oxygen species (ROS) by secreting terpenoids, thereby resisting oxidative stress. In addition, two metabolic pathways, the vitamin B6 and the sphingolipid pathways, of C. vulgaris were significantly disturbed by microcystins, contributing to cell membrane and mitochondrial damage. Thus, both the low (400 μg/L) and the high (1,600 μg/L) MC-LR concentration inhibited algae growth within 3 to 7 days, and the inhibition rates increased with the increase in the MC-LR concentration. The above results indicate that the toxin-producing Microcystis species have a stronger toxin tolerance under longer-term toxin exposure in natural water environments. Thus, microcystins participates in interspecific interaction and phytoplankton population regulation and creates suitable conditions for the toxin-producing M. aeruginosa to become the dominant species in algae blooms.

A lipid atlas of human and mouse immune cells provides insights into ferroptosis susceptibility

The cellular lipidome comprises thousands of unique lipid species. Here, using mass spectrometry-based targeted lipidomics, we characterize the lipid landscape of human and mouse immune cells ( www.cellularlipidatlas.com ). Using this resource, we show that immune cells have unique lipidomic signatures and that processes such as activation, maturation and development impact immune cell lipid composition. To demonstrate the potential of this resource to provide insights into immune cell biology, we determine how a cell-specific lipid trait-differences in the abundance of polyunsaturated fatty acid-containing glycerophospholipids (PUFA-PLs)-influences immune cell biology. First, we show that differences in PUFA-PL content underpin the differential susceptibility of immune cells to ferroptosis. Second, we show that low PUFA-PL content promotes resistance to ferroptosis in activated neutrophils. In summary, we show that the lipid landscape is a defining feature of immune cell identity and that cell-specific lipid phenotypes underpin aspects of immune cell physiology.

MemPrep, a new technology for isolating organellar membranes provides fingerprints of lipid bilayer stress

Biological membranes have a stunning ability to adapt their composition in response to physiological stress and metabolic challenges. Little is known how such perturbations affect individual organelles in eukaryotic cells. Pioneering work has provided insights into the subcellular distribution of lipids in the yeast Saccharomyces cerevisiae, but the composition of the endoplasmic reticulum (ER) membrane, which also crucially regulates lipid metabolism and the unfolded protein response, remains insufficiently characterized. Here, we describe a method for purifying organelle membranes from yeast, MemPrep. We demonstrate the purity of our ER membrane preparations by proteomics, and document the general utility of MemPrep by isolating vacuolar membranes. Quantitative lipidomics establishes the lipid composition of the ER and the vacuolar membrane. Our findings provide a baseline for studying membrane protein biogenesis and have important implications for understanding the role of lipids in regulating the unfolded protein response (UPR). The combined preparative and analytical MemPrep approach uncovers dynamic remodeling of ER membranes in stressed cells and establishes distinct molecular fingerprints of lipid bilayer stress.

Quantifying Fluorescence Lifetime Responsiveness of Environment-Sensitive Probes for Membrane Fluidity Measurements

The structural diversity of different lipid species within the membrane defines its biophysical properties such as membrane fluidity, phase transition, curvature, charge distribution, and tension. Environment-sensitive probes, which change their spectral properties in response to their surrounding milieu, have greatly contributed to our understanding of such biophysical properties. To realize the full potential of these probes and avoid misinterpretation of their spectral responses, a detailed investigation of their fluorescence characteristics in different environments is necessary. Here, we examined the fluorescence lifetime of two newly developed membrane order probes, NR12S and NR12A, in response to alterations in their environments such as the degree of lipid saturation, cholesterol content, double bond position and configuration, and phospholipid headgroup. As a comparison, we investigated the lifetime sensitivity of the membrane tension probe Flipper in these environments. Applying fluorescence lifetime imaging microscopy (FLIM) in both model membranes and biological membranes, all probes distinguished membrane phases by lifetime but exhibited different lifetime sensitivities to varying membrane biophysical properties (e.g., cholesterol). While the lifetime of Flipper is particularly sensitive to the membrane cholesterol content, the NR12S and NR12A lifetimes are moderately sensitive to both the cholesterol content and lipid acyl chains. Moreover, all of the probes exhibit longer lifetimes at longer emission wavelengths in membranes of any complexity. This emission wavelength dependency results in varying lifetime resolutions at different spectral regions, which are highly relevant for FLIM data acquisition. Our data provide valuable insights on how to perform FLIM with these probes and highlight both their potential and limitations.

The Mitochondrial Connection: The Nek Kinases' New Functional Axis in Mitochondrial Homeostasis

Mitochondria provide energy for all cellular processes, including reactions associated with cell cycle progression, DNA damage repair, and cilia formation. Moreover, mitochondria participate in cell fate decisions between death and survival. Nek family members have already been implicated in DNA damage response, cilia formation, cell death, and cell cycle control. Here, we discuss the role of several Nek family members, namely Nek1, Nek4, Nek5, Nek6, and Nek10, which are not exclusively dedicated to cell cycle-related functions, in controlling mitochondrial functions. Specifically, we review the function of these Neks in mitochondrial respiration and dynamics, mtDNA maintenance, stress response, and cell death. Finally, we discuss the interplay of other cell cycle kinases in mitochondrial function and vice versa. Nek1, Nek5, and Nek6 are connected to the stress response, including ROS control, mtDNA repair, autophagy, and apoptosis. Nek4, in turn, seems to be related to mitochondrial dynamics, while Nek10 is involved with mitochondrial metabolism. Here, we propose that the participation of Neks in mitochondrial roles is a new functional axis for the Nek family.

Reconstitution of ORP-mediated lipid exchange coupled to PI4P metabolism

Oxysterol-binding protein-related proteins (ORPs) play key roles in the distribution of lipids in eukaryotic cells by exchanging sterol or phosphatidylserine for PI4P between the endoplasmic reticulum (ER) and other cell regions. However, it is unclear how their exchange capacity is coupled to PI4P metabolism. To address this question quantitatively, we analyze the activity of a representative ORP, Osh4p, in an ER/Golgi interface reconstituted with ER- and Golgi-mimetic membranes functionalized with PI4P phosphatase Sac1p and phosphatidylinositol (PI) 4-kinase, respectively. Using real-time assays, we demonstrate that upon adenosine triphosphate (ATP) addition, Osh4p creates a sterol gradient between these membranes, relying on the spatially distant synthesis and hydrolysis of PI4P, and quantify how much PI4P is needed for this process. Then, we develop a quantitatively accurate kinetic model, validated by our data, and extrapolate this to estimate to what extent PI4P metabolism can drive ORP-mediated sterol transfer in cells. Finally, we show that Sec14p can support PI4P metabolism and Osh4p activity by transferring PI between membranes. This study establishes that PI4P synthesis drives ORP-mediated lipid exchange and that ATP energy is needed to generate intermembrane lipid gradients. Furthermore, it defines to what extent ORPs can distribute lipids in the cell and reassesses the role of PI-transfer proteins in PI4P metabolism.

The expanding roles of PI4P and PI(4,5)P2 at the plasma membrane: Role of phosphatidylinositol transfer proteins

Phosphoinositides are phosphorylated derivatives of phosphatidylinositol, a phospholipid that is synthesised at the endoplasmic reticulum. The plasma membrane contains the enzymes to phosphorylate phosphatidylinositol and is therefore rich in the phosphorylated derivatives, PI4P and PI(4,5)P2. PI(4,5)P2 is a substrate for phospholipase C and during cell signaling, PI(4,5)P2 levels are reduced. Here I discuss a family of proteins, phosphatidylinositol transfer proteins (PITPs) that can restore PI(4,5)P2 levels.

Cationic amphiphilic drugs induce accumulation of cytolytic lysoglycerophospholipids in the lysosomes of cancer cells and block their recycling into common membrane glycerophospholipids

Lysosomes are acidic organelles responsible for lipid catabolism, and their functions can be disrupted by cationic amphiphilic drugs that neutralize lumenal pH and thereby inhibit most lysosomal hydrolases. These drugs can also induce lysosomal membrane permeabilization and cancer cell death, but the underlying mechanism remains elusive. Here, we uncover that the cationic amphiphilic drugs induce a substantial accumulation of cytolytic lysoglycerophospholipids within the lysosomes of cancer cells, and thereby prevent the recycling of lysoglycerophospholipids to produce common membrane glycerophospholipids. Using quantitative mass spectrometry-based shotgun lipidomics, we demonstrate that structurally diverse cationic amphiphilic drugs, along with other types of lysosomal pH-neutralizing reagents, elevate the amounts of lysoglycerophospholipids in MCF7 breast carcinoma cells. Lysoglycerophospholipids constitute ∼11 mol% of total glycerophospholipids in lysosomes purified from MCF7 cells, compared with ∼1 mol% in the cell lysates. Treatment with cationic amphiphilic drug siramesine further elevates the lysosomal lysoglycerophospholipid content to ∼24 mol% of total glycerophospholipids. Exogenously added traceable lysophosphatidylcholine is rapidly acylated to form diacylphosphatidylcholine, but siramesine treatment sequesters the lysophosphatidylcholine in the lysosomes and prevents it from undergoing acylation. These findings shed light on the unexplored role of lysosomes in the recycling of lysoglycerophospholipids and uncover the mechanism of action of promising anticancer agents.

Emerging roles and therapeutic potentials of sphingolipids in pathophysiology: emphasis on fatty acyl heterogeneity

Sphingolipids not only exert structural roles in cellular membranes, but also act as signaling molecules in various physiological and pathological processes. A myriad of studies have shown that abnormal levels of sphingolipids and their metabolic enzymes are associated with a variety of human diseases. Moreover, blood sphingolipids can also be used as biomarkers for disease diagnosis. This review summarizes the biosynthesis, metabolism, and pathological roles of sphingolipids, with emphasis on the biosynthesis of ceramide, the precursor for the biosynthesis of complex sphingolipids with different fatty acyl chains. The possibility of using sphingolipids for disease prediction, diagnosis, and treatment is also discussed. Targeting endogenous ceramides and complex sphingolipids along with their specific fatty acyl chain to promote future drug development will also be discussed.

Dimeric Tubulin Modifies Mechanical Properties of Lipid Bilayer, as Probed Using Gramicidin A Channel

Using the gramicidin A channel as a molecular probe, we show that tubulin binding to planar lipid membranes changes the channel kinetics-seen as an increase in the lifetime of the channel dimer-and thus points towards modification of the membrane's mechanical properties. The effect is more pronounced in the presence of non-lamellar lipids in the lipid mixture used for membrane formation. To interpret these findings, we propose that tubulin binding redistributes the lateral pressure of lipid packing along the membrane depth, making it closer to the profile expected for lamellar lipids. This redistribution happens because tubulin perturbs the lipid headgroup spacing to reach the membrane's hydrophobic core via its amphiphilic α-helical domain. Specifically, it increases the forces of repulsion between the lipid headgroups and reduces such forces in the hydrophobic region. We suggest that the effect is reciprocal, meaning that alterations in lipid bilayer mechanics caused by membrane remodeling during cell proliferation in disease and development may also modulate tubulin membrane binding, thus exerting regulatory functions. One of those functions includes the regulation of protein-protein interactions at the membrane surface, as exemplified by VDAC complexation with tubulin.

A cholesterol switch controls phospholipid scrambling by G protein-coupled receptors

Class A G protein-coupled receptors (GPCRs), a superfamily of cell membrane signaling receptors, moonlight as constitutively active phospholipid scramblases. The plasma membrane of metazoan cells is replete with GPCRs yet has a strong resting trans-bilayer phospholipid asymmetry, with the signaling lipid phosphatidylserine confined to the cytoplasmic leaflet. To account for the persistence of this lipid asymmetry in the presence of GPCR scramblases, we hypothesized that GPCR-mediated lipid scrambling is regulated by cholesterol, a major constituent of the plasma membrane. We now present a technique whereby synthetic vesicles reconstituted with GPCRs can be supplemented with cholesterol to a level similar to that of the plasma membrane and show that the scramblase activity of two prototypical GPCRs, opsin and the β1-adrenergic receptor, is impaired upon cholesterol loading. Our data suggest that cholesterol acts as a switch, inhibiting scrambling above a receptor-specific threshold concentration to disable GPCR scramblases at the plasma membrane.

Quantification of Phosphatidylserine Molecules on the Surface of Individual Cells Using Single-Molecule Force Spectroscopy

Identification of the phosphatidylserine (PS) discrepancies occurring on the cellular membrane during apoptotic processes is of the utmost importance. However, monitoring the quantity of PS molecules in real-time at a single-cell level currently remains a challenging task. Here, we demonstrate this objective by leveraging the specific binding and reversible interaction exhibited by the zinc(II) dipyridinamine complex (ZnDPA) with PS. Lipoic acid-functionalized ZnDPA (LP-ZnDPA) was subsequently immobilized onto the surface of an atomic force microscopy cantilever to form a force probe, ALP-ZnDPA, enabling a PS-specific dynamic imaging and detection mode. By utilizing this technique, we can not only create a heat map of the expression level of PS with submicron resolution but also quantify the number of molecules present on a single cell's surface with a detection limit of 1.86 × 104 molecules. The feasibility of the proposed method is demonstrated through the analysis of PS expression levels in different cancer cell lines and at various stages of paclitaxel-induced apoptosis. This study represents the first application of a force probe to quantify PS molecules on the surface of individual cells, providing insight into dynamic changes in PS content during apoptosis at the molecular level and introducing a novel dimension to current detection methodologies.

A cholesterol switch controls phospholipid scrambling by G protein-coupled receptors

Class A G protein-coupled receptors (GPCRs), a superfamily of cell membrane signaling receptors, moonlight as constitutively active phospholipid scramblases. The plasma membrane of metazoan cells is replete with GPCRs, yet has a strong resting trans-bilayer phospholipid asymmetry, with the signaling lipid phosphatidylserine confined to the cytoplasmic leaflet. To account for the persistence of this lipid asymmetry in the presence of GPCR scramblases, we hypothesized that GPCR-mediated lipid scrambling is regulated by cholesterol, a major constituent of the plasma membrane. We now present a technique whereby synthetic vesicles reconstituted with GPCRs can be supplemented with cholesterol to a level similar to that of the plasma membrane and show that the scramblase activity of two prototypical GPCRs, opsin and the β1-adrenergic receptor, is impaired upon cholesterol loading. Our data suggest that cholesterol acts as a switch, inhibiting scrambling above a receptor-specific threshold concentration to disable GPCR scramblases at the plasma membrane.

Immunometabolism in the pathogenesis of asthma

Bronchial asthma is a heterogeneous disease characterised by chronic airway inflammation. A variety of immune cells such as eosinophils, mast cells, T lymphocytes, neutrophils and airway epithelial cells are involved in the airway inflammation and airway hyperresponsiveness in asthma pathogenesis, resulting in extensive and variable reversible expiratory airflow limitation. However, the precise molecular mechanisms underlying the allergic immune responses, particularly immunometabolism, remains unclear. Studies have detected enhanced oxidative stress, and abnormal metabolic progresses of glycolysis, fatty acid and amino acid in various immune cells, inducing dysregulation of innate and adaptive immune responses in asthma pathogenesis. Immunometabolism mechanisms contain multiple signalling pathways, providing novel therapy targets for asthma. This review summarises the current knowledge on immunometabolism reprogramming in asthma pathogenesis, as well as potential therapy strategies.

Structure, Function, and Physicochemical Properties of Pore-forming Antimicrobial Peptides

Antimicrobial peptides (AMPs), a class of antimicrobial agents, possess considerable potential to treat various microbial ailments. The broad range of activity and rare complete bacterial resistance to AMPs make them ideal candidates for commercial development. These peptides with widely varying compositions and sources share recurrent structural and functional features in mechanisms of action. Studying the mechanisms of AMP activity against bacteria may lead to the development of new antimicrobial agents that are more potent. Generally, AMPs are effective against bacteria by forming pores or disrupting membrane barriers. The important structural aspects of cytoplasmic membranes of pathogens and host cells will also be outlined to understand the selective antimicrobial actions. The antimicrobial activities of AMPs are related to multiple physicochemical properties, such as length, sequence, helicity, charge, hydrophobicity, amphipathicity, polar angle, and also self-association. These parameters are interrelated and need to be considered in combination. So, gathering the most relevant available information will help to design and choose the most effective AMPs.

Uptake and Metabolic Conversion of Exogenous Phosphatidylcholines Depending on Their Acyl Chain Structure in Arabidopsis thaliana

Fungi and plants are not only capable of synthesizing the entire spectrum of lipids de novo but also possess a well-developed system that allows them to assimilate exogenous lipids. However, the role of structure in the ability of lipids to be absorbed and metabolized has not yet been characterized in detail. In the present work, targeted lipidomics of phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs), in parallel with morphological phenotyping, allowed for the identification of differences in the effects of PC molecular species introduced into the growth medium, in particular, typical bacterial saturated (14:0/14:0, 16:0/16:0), monounsaturated (16:0/18:1), and typical for fungi and plants polyunsaturated (16:0/18:2, 18:2/18:2) species, on Arabidopsis thaliana. For comparison, the influence of an artificially synthesized (1,2-di-(3-(3-hexylcyclopentyl)-propanoate)-sn-glycero-3-phosphatidylcholine, which is close in structure to archaeal lipids, was studied. The phenotype deviations stimulated by exogenous lipids included changes in the length and morphology of both the roots and leaves of seedlings. According to lipidomics data, the main trends in response to exogenous lipid exposure were an increase in the proportion of endogenic 18:1/18:1 PC and 18:1_18:2 PC molecular species and a decrease in the relative content of species with C18:3, such as 18:3/18:3 PC and/or 16:0_18:3 PC, 16:1_18:3 PE. The obtained data indicate that exogenous lipid molecules affect plant morphology not only due to their physical properties, which are manifested during incorporation into the membrane, but also due to the participation of exogenous lipid molecules in the metabolism of plant cells. The results obtained open the way to the use of PCs of different structures as cellular regulators.

Nanoreporter Identifies Lysosomal Storage Disease Lipid Accumulation Intracranially

Dysregulated lipid metabolism contributes to neurodegenerative pathologies and neurological decline in lysosomal storage disorders as well as more common neurodegenerative diseases. Niemann-Pick type A (NPA) is a fatal neurodegenerative lysosomal storage disease characterized by abnormal sphingomyelin accumulation in the endolysosomal lumen. The ability to monitor abnormalities in lipid homeostasis intracranially could improve basic investigations and the development of effective treatment strategies. We investigated the carbon nanotube-based detection of intracranial lipid content. We found that the near-infrared emission of a carbon nanotube-based lipid sensor responds to lipid accumulation in neuronal and in vivo models of NPA. The nanosensor detected lipid accumulation intracranially in an acid sphingomyelinase knockout mouse via noninvasive near-infrared spectroscopy. This work indicates a tool to improve drug development processes in NPA, other lysosomal storage diseases, and neurodegenerative diseases.

Immunity-linked genes are stimulated by a membrane stress pathway linked to Golgi function and the ARF-1 GTPase

Infection response and other immunity-linked genes (ILGs) were first named in Caenorhabditis elegans-based expression after pathogen challenge, but many are also up-regulated when lipid metabolism is perturbed. Why pathogen attack and metabolic changes both increase ILGs is unclear. We find that ILGs are activated when phosphatidylcholine (PC) levels change in membranes of secretory organelles in C. elegans. RNAi targeting of the ADP-ribosylation factor arf-1, which disrupts the Golgi and secretory function, also activates ILGs. Low PC limits ARF-1 function, suggesting a mechanism for ILG activation via lipid metabolism, as part of a membrane stress response acting outside the ER. RNAi of selected ILGs uncovered defects in the secretion of two GFP reporters and the accumulation of a pathogen-responsive complement C1r/C1s, Uegf, Bmp1 (CUB) domain fusion protein. Our data argue that up-regulation of some ILGs is a coordinated response to changes in trafficking and may act to counteract stress on secretory function.

Zinc Cations Uniquely Stabilize Cell Membrane for Cell Cryopreservation

We report, for the first time, merely using a small amount of (0.039% w/w) Zn(II) instead of very high concentration (25%-50% w/w) of conventional cryoprotective agents (CPAs), i.e., glycerol, during the cryopreservation of red blood cells (RBCs) can lead to a comparable post-thaw recovery rate of ∼95% while avoiding the tedious gradient washout process for the removal of CPA afterward. The result is remarkable, since Zn(II) does not have the ice-controlling ability reported to be critical for CPA. It benefits from its moderate interaction with lipid molecules, facilitating the formation of small and dynamic lipid clusters. Consequently, the membrane fluidity is maintained, and the cells are resilient to osmotic and mechanical stresses during cryopreservation. This study first reports the ion-specific effect on stabilizing the cell membrane; meanwhile, reversibly tuning the structure of biological samples against injuries during the cooling and rewarming provides a new strategy for cryopreservation.

Quantitative Analysis of Acetyl-CoA, Malonyl-CoA, and Succinyl-CoA in Myocytes

Several analytical challenges make it difficult to accurately measure coenzyme A (CoA) metaboforms, including insufficient stability and a lack of available metabolite standards. Consequently, our understanding of CoA biology and the modulation of human diseases may be nascent. CoA's serve as lipid precursors, energy intermediates, and mediators of post-translational modifications of proteins. Here, we present a liquid chromatography-mass spectrometry (LC-MS) approach to measure malonyl-CoA, acetyl-CoA, and succinyl-CoA in complex biological samples. Additionally, we evaluated workflows to increase sample stability. We used reference standards to optimize CoA assay sensitivity and test CoA metabolite stability as a function of the reconstitution solvent. We show that using glass instead of plastic sample vials decreases CoA signal loss and improves the sample stability. We identify additives that improve CoA stability and facilitate accurate analysis of CoA species across large sample sets. We apply our optimized workflow to biological samples of skeletal muscle cells cultured under hypoxic and normoxia conditions. Together, our workflow improves the detection and identification of CoA species through targeted analysis in complex biological samples.

Effect of Insulin Resistance on Abdominal Obesity, Liver Fat Infiltration, and Body Mass Index in Youngsters

AIM

Evaluate insulin resistance (IR) as a mediator of the effect of body fat distribution on liver fat infiltration and stiffness (LSt) in young adults using structural equation modeling (SEM).

METHODS

We invited 500 first year students from two universities and evaluated their family history to determine the risk for cardiometabolic disease. Of these, 174 students (age 19 ± 1 years) were assessed for total body fat percentage (BF%), LSt, fat infiltration (Coefficient attenuated parameter CAP), and serum biochemical analysis. We performed a mediation analysis using two different structural equation models to determine the relationship between BMI, BF%, abdominal obesity (AO), IR, LSt, and fat infiltration using standardized β coefficients. The symbol "->" means "explains/causes".

RESULTS

Model#1 supported that mediation analysis and had a better fit than the direct effect. AO->IR (b = 0.62, p = 0.005), AO->CAP (b = 0.63, p <0.001), and CAP->IR (b = 0.23, p = 0.007), with negligible effect of BMI on CAP and IR. Model#2 showed direct effect of BMI on LSt was a better fit than mediation. BMI->LSt (b = 0.17, p = 0.05) but no effect AO->LSt. Interestingly, LSt->IR (b = 0.18, p = 0.001), but bi-directional IR->LSt (b = 0.23, p = 0.001).

CONCLUSIONS

AO and BMI in young adults have differential phenotypic effects on liver CAP and LSt. Visceral fat had a direct effect on IR and CAP. Meanwhile, BMI was associated with LSt. Our findings shed light on the complex interplay of factors influencing liver stiffness, particularly in young individuals. Further research is needed to elucidate the precise mechanisms underlying these associations and their implications for liver health.

Research progress of hyperthermia in tumor therapy by influencing metabolic reprogramming of tumor cells

Cellular metabolic reprogramming is an important feature of malignant tumors. Metabolic reprogramming causes changes in the levels or types of specific metabolites inside and outside the cell, which affects tumorigenesis and progression by influencing gene expression, the cellular state, and the tumor microenvironment. During tumorigenesis, a series of changes in the glucose metabolism, fatty acid metabolism, amino acid metabolism, and cholesterol metabolism of tumor cells occur, which are involved in the process of cellular carcinogenesis and constitute part of the underlying mechanisms of tumor formation. Hyperthermia, as one of the main therapeutic tools for malignant tumors, has obvious effects on tumor cell metabolism. In this paper, we will combine the latest research progress in the field of cellular metabolic reprogramming and focus on the current experimental research and clinical treatment of hyperthermia in cellular metabolic reprogramming to discuss the feasibility of cellular metabolic reprogramming-related mechanisms guiding hyperthermia in malignant tumor treatment, so as to provide more ideas for hyperthermia to treat malignant tumors through the direction of cellular metabolic reprogramming.

Analyzing the impact and mechanism of bisphenol A on testicular lipid metabolism in Gobiocypris rarus through integrated lipidomics and transcriptomics

Bisphenol A (BPA) is one of the most common environmental endocrine chemicals, known for its estrogenic effects that can interfere with male spermatogenesis. Lipids play crucial roles in sperm production, capacitation, and motility as important components of the sperm plasma membrane. However, limited research has explored whether BPA affects lipid metabolism in the testes of male fish and subsequently impacts spermatogenesis. In this study, we employed Gobiocypris rarus rare minnow as a research model and exposed them to environmentally relevant concentrations of BPA (15 μg/L) for 5 weeks. We assessed sperm morphology and function and analyzed changes in testicular lipid composition and transcriptomics. The results demonstrated a significant increase in the sperm head membrane damage rate, along with reduced sperm motility and fertilization ability due to BPA exposure. Lipidomics analysis revealed that BPA increased the content of 11 lipids while decreasing the content of 6 lipids in the testes, particularly within glycerophospholipids, glycerolipids, and sphingolipid subclasses. Transcriptomics results indicated significant up-regulation in pathways such as cholesterol metabolism, peroxisome proliferator-activated receptor signaling, and fat digestion and absorption, with significant alterations in key genes related to lipid metabolism, including apolipoprotein A-I, apolipoprotein C-I, and translocator protein. These findings suggest that BPA exposure can induce testicular lipid metabolism disruption in rare minnows, potentially resulting in abnormalities in rare minnow spermatogenesis.

SGMS2 in primary osteoporosis with facial nerve palsy

Pathogenic heterozygous variants in SGMS2 cause a rare monogenic form of osteoporosis known as calvarial doughnut lesions with bone fragility (CDL). The clinical presentations of SGMS2-related bone pathology range from childhood-onset osteoporosis with low bone mineral density and sclerotic doughnut-shaped lesions in the skull to a severe spondylometaphyseal dysplasia with neonatal fractures, long-bone deformities, and short stature. In addition, neurological manifestations occur in some patients. SGMS2 encodes sphingomyelin synthase 2 (SMS2), an enzyme involved in the production of sphingomyelin (SM). This review describes the biochemical structure of SM, SM metabolism, and their molecular actions in skeletal and neural tissue. We postulate how disrupted SM gradient can influence bone formation and how animal models may facilitate a better understanding of SGMS2-related osteoporosis.

Lipid Sorting and Organelle Identity

The sorting and trafficking of lipids between organelles gives rise to a dichotomy of bulk membrane properties between organelles of the secretory and endolysosome networks, giving rise to two "membrane territories" based on differences in lipid-packing density, net membrane charge, and bilayer leaflet asymmetries. The cellular organelle membrane dichotomy emerges from ER-to-PM anterograde membrane trafficking and the synthesis of sphingolipids and cholesterol flux at the trans-Golgi network, which constitutes the interface between the two membrane territories. Organelle homeostasis is maintained by vesicle-mediated retrieval of bulk membrane from the distal organelles of each territory to the endoplasmic reticulum or plasma membrane and by soluble lipid transfer proteins that traffic particular lipids. The concept of cellular membrane territories emphasizes the contrasting features of organelle membranes of the secretory and endolysosome networks and the essential roles of lipid-sorting pathways that maintain organelle function.

Broadening horizons: The role of ferroptosis in myocardial ischemia-reperfusion injury

Ferroptosis is a novel type of regulated cell death (RCD) discovered in recent years, where abnormal intracellular iron accumulation leads to the onset of lipid peroxidation, which further leads to the disruption of intracellular redox homeostasis and triggers cell death. Iron accumulation with lipid peroxidation is considered a hallmark of ferroptosis that distinguishes it from other RCDs. Myocardial ischemia-reperfusion injury (MIRI) is a process of increased myocardial cell injury that occurs during coronary reperfusion after myocardial ischemia and is associated with high post-infarction mortality. Multiple experiments have shown that ferroptosis plays an important role in MIRI pathophysiology. This review systematically summarized the latest research progress on the mechanisms of ferroptosis. Then we report the possible link between the occurrence of MIRI and ferroptosis in cardiomyocytes. Finally, we discuss and analyze the related drugs that target ferroptosis to attenuate MIRI and its action targets, and point out the shortcomings of the current state of relevant research and possible future research directions. It is hoped to provide a new avenue for improving the prognosis of the acute coronary syndrome.

Ester Bond: Chemically Labile Yet Mechanically Stable

Due to the dynamic nature of ester linkages, ester-bond-containing materials are well known for their outstanding degradability and stimuli responsiveness. However, whether ester hydrolysis is affected by mechanical forces remains unclear. Here, we develop a single-molecule assay to quantitatively study the force-dependent ester hydrolysis using an engineered circular permutant protein with a caged ester bond as a model. Our single-molecule force spectroscopy results show that the ester hydrolysis rate is surprisingly insensitive to forces, with a ∼7 s-1 dissociation rate that remains almost unchanged in the force range of 80 to 200 pN. Quantum calculations reveal that the ester hydrolysis involves an intermediate state formed by either H3O+- or OH--bonded tetrahedral intermediates. The measured ester-hydrolysis kinetics at the single-molecule level may primarily correspond to the rupture of these intermediate states. However, the rate-limiting step appears to be the formation of the tetrahedral intermediates, which cannot be quantitatively characterized in our experiments. Nonetheless, based on the quantum calculations, this step is also insensitive to applied forces. Altogether, our study suggests that the ester bond is chemically labile yet mechanically stable, serving as the basis for the design of responsive materials using ester bonds as mechanically inert units.

Mitochondrial phospholipid metabolism in health and disease

Studies of rare human genetic disorders of mitochondrial phospholipid metabolism have highlighted the crucial role that membrane phospholipids play in mitochondrial bioenergetics and human health. The phospholipid composition of mitochondrial membranes is highly conserved from yeast to humans, with each class of phospholipid performing a specific function in the assembly and activity of various mitochondrial membrane proteins, including the oxidative phosphorylation complexes. Recent studies have uncovered novel roles of cardiolipin and phosphatidylethanolamine, two crucial mitochondrial phospholipids, in organismal physiology. Studies on inter-organellar and intramitochondrial phospholipid transport have significantly advanced our understanding of the mechanisms that maintain mitochondrial phospholipid homeostasis. Here, we discuss these recent advances in the function and transport of mitochondrial phospholipids while describing their biochemical and biophysical properties and biosynthetic pathways. Additionally, we highlight the roles of mitochondrial phospholipids in human health by describing the various genetic diseases caused by disruptions in their biosynthesis and discuss advances in therapeutic strategies for Barth syndrome, the best-studied disorder of mitochondrial phospholipid metabolism.

DYT-TOR1A dystonia: an update on pathogenesis and treatment

DYT-TOR1A dystonia is a neurological disorder characterized by involuntary muscle contractions and abnormal movements. It is a severe genetic form of dystonia caused by mutations in the TOR1A gene. TorsinA is a member of the AAA + family of adenosine triphosphatases (ATPases) involved in a variety of cellular functions, including protein folding, lipid metabolism, cytoskeletal organization, and nucleocytoskeletal coupling. Almost all patients with TOR1A-related dystonia harbor the same mutation, an in-frame GAG deletion (ΔGAG) in the last of its 5 exons. This recurrent variant results in the deletion of one of two tandem glutamic acid residues (i.e., E302/303) in a protein named torsinA [torsinA(△E)]. Although the mutation is hereditary, not all carriers will develop DYT-TOR1A dystonia, indicating the involvement of other factors in the disease process. The current understanding of the pathophysiology of DYT-TOR1A dystonia involves multiple factors, including abnormal protein folding, signaling between neurons and glial cells, and dysfunction of the protein quality control system. As there are currently no curative treatments for DYT-TOR1A dystonia, progress in research provides insight into its pathogenesis, leading to potential therapeutic and preventative strategies. This review summarizes the latest research advances in the pathogenesis, diagnosis, and treatment of DYT-TOR1A dystonia.

Mechanisms of Modulation of Mitochondrial Architecture

Mitochondrial network architecture plays a critical role in cellular physiology. Indeed, alterations in the shape of mitochondria upon exposure to cellular stress can cause the dysfunction of these organelles. In this scenario, mitochondrial dynamics proteins and the phospholipid composition of the mitochondrial membrane are key for fine-tuning the modulation of mitochondrial architecture. In addition, several factors including post-translational modifications such as the phosphorylation, acetylation, SUMOylation, and o-GlcNAcylation of mitochondrial dynamics proteins contribute to shaping the plasticity of this architecture. In this regard, several studies have evidenced that, upon metabolic stress, mitochondrial dynamics proteins are post-translationally modified, leading to the alteration of mitochondrial architecture. Interestingly, several proteins that sustain the mitochondrial lipid composition also modulate mitochondrial morphology and organelle communication. In this context, pharmacological studies have revealed that the modulation of mitochondrial shape and function emerges as a potential therapeutic strategy for metabolic diseases. Here, we review the factors that modulate mitochondrial architecture.

Reconstitution of ORP-mediated lipid exchange process coupled to PI(4)P metabolism

Lipid distribution in the eukaryotic cells depends on tight couplings between lipid transfer and lipid metabolism. Yet these couplings remain poorly described. Notably, it is unclear to what extent lipid exchangers of the OSBP-related proteins (ORPs) family, coupled to PI(4)P metabolism, contribute to the formation of sterol and phosphatidylserine gradient between the endoplasmic reticulum (ER) and other cell regions. To address this question, we have examined in vitro the activity of Osh4p, a representative ORP, between Golgi mimetic membranes in which PI(4)P is produced by a PI 4-kinase and ER mimetic membranes in which PI(4)P is hydrolyzed by the phosphatase Sac1p. Using quantitative, real-time assays, we demonstrate that Osh4p creates a sterol gradient between the two membranes by sterol/PI(4)P exchange as soon as a PI(4)P gradient is generated at this interface following ATP addition, and define how much PI(4)P must be synthesized for this process. Then, using a kinetic model supported by our in vitro data, we estimate to what extent PI(4)P metabolism can drive lipid transfer in cells. Finally, we show that Sec14p, by transferring phosphatidylinositol between membranes, can support the synthesis of PI(4)P and the creation of a sterol gradient by Osh4p. These results indicate to what extent ORPs, under the control of PI(4)P metabolism, can distribute lipids in the cell.

The expanding organelle lipidomes: current knowledge and challenges

Lipids in cell membranes and subcellular compartments play essential roles in numerous cellular processes, such as energy production, cell signaling and inflammation. A specific organelle lipidome is characterized by lipid synthesis and metabolism, intracellular trafficking, and lipid homeostasis in the organelle. Over the years, considerable effort has been directed to the identification of the lipid fingerprints of cellular organelles. However, these fingerprints are not fully characterized due to the large variety and structural complexity of lipids and the great variability in the abundance of different lipid species. The process becomes even more challenging when considering that the lipidome differs in health and disease contexts. This review summarizes the information available on the lipid composition of mammalian cell organelles, particularly the lipidome of the nucleus, mitochondrion, endoplasmic reticulum, Golgi apparatus, plasma membrane and organelles in the endocytic pathway. The lipid compositions of extracellular vesicles and lamellar bodies are also described. In addition, several examples of subcellular lipidome dynamics under physiological and pathological conditions are presented. Finally, challenges in mapping organelle lipidomes are discussed.

Lipid Metabolic Regulatory Crosstalk Between Cancer Cells and Tumor-Associated Macrophages

In the tumor microenvironment, tumor-associated macrophages (TAMs) are one of the most abundant cell populations, playing key roles in tumorigenesis, chemoresistance, immune evasion, and metastasis. There is an important interaction between TAMs and cancer cells: on the one hand, tumors control the function of infiltrating macrophages, contributing to reprogramming of TAMs, and on the other hand, TAMs affect the growth of cancer cells. This review focuses on lipid metabolism changes in the complex relationship between cancer cells and TAMs. We discuss how lipid metabolism in cancer cells affects macrophage phenotypic and metabolic changes and, subsequently, how altered lipid metabolism of TAMs influences tumor progression. Identifying the metabolic changes that influence the complex interaction between tumor cells and TAMs is also an important step in exploring new therapeutic approaches that target metabolic reprogramming of immune cells to enhance their tumoricidal potential and bypass therapy resistance. Our work may provide new targets for antitumor therapies.

MoVast2 combined with MoVast1 regulates lipid homeostasis and autophagy in Magnaporthe oryzae

Macroautophagy/autophagy is an evolutionarily conserved biological process among eukaryotes that degrades unwanted materials such as protein aggregates, damaged mitochondria and even viruses to maintain cell survival. Our previous studies have demonstrated that MoVast1 acts as an autophagy regulator regulating autophagy, membrane tension, and sterol homeostasis in rice blast fungus. However, the detailed regulatory relationships between autophagy and VASt domain proteins remain unsolved. Here, we identified another VASt domain-containing protein, MoVast2, and further uncovered the regulatory mechanism of MoVast2 in M. oryzae. MoVast2 interacted with MoVast1 and MoAtg8, and colocalized at the PAS and deletion of MoVAST2 results in inappropriate autophagy progress. Through TOR activity analysis, sterols and sphingolipid content detection, we found high sterol accumulation in the ΔMovast2 mutant, whereas this mutant showed low sphingolipids and low activity of both TORC1 and TORC2. In addition, MoVast2 colocalized with MoVast1. The localization of MoVast2 in the MoVAST1 deletion mutant was normal; however, deletion of MoVAST2 leads to mislocalization of MoVast1. Notably, the wide-target lipidomic analyses revealed significant changes in sterols and sphingolipids, the major PM components, in the ΔMovast2 mutant, which was involved in lipid metabolism and autophagic pathways. These findings confirmed that the functions of MoVast1 were regulated by MoVast2, revealing that MoVast2 combined with MoVast1 maintained lipid homeostasis and autophagy balance by regulating TOR activity in M. oryzae.

Structural and functional diversity in plant specialized metabolism signals and products: The case of oxylipins and triterpenes

Metabolic enzymes tend to evolve towards catalytic efficacy, precision and speed. This seems particularly true for ancient and conserved enzymes involved in fundamental cellular processes that are present virtually in every cell and organism and converting and producing relatively limited metabolite numbers. Nevertheless, sessile organisms like plants have an astonishing repertoire of specific (specialized) metabolites that, by numbers and chemical complexity, by far exceed primary metabolites. Most theories agree that early gene duplication, subsequent positive selection and diversifying evolution have allowed relaxed selection of duplicated metabolic genes, thus facilitating the accumulation of mutations that could broaden substrate/product specificity and lower activation barriers and kinetics. Here, we use oxylipins, oxygenated fatty acids of plastidial origin to which the phytohormone jasmonate belongs, and triterpenes, a large group of specialized metabolites whose biosynthesis is often elicited by jasmonates, to showcase the structural and functional diversity of chemical signals and products in plant metabolism.

Gaining New Insights into Fundamental Biological Pathways by Bacterial Toxin-Based Genetic Screens

Genetic screen technology has been applied to study the mechanism of action of bacterial toxins-a special class of virulence factors that contribute to the pathogenesis caused by bacterial infections. These screens aim to identify host factors that directly or indirectly facilitate toxin intoxication. Additionally, specific properties of certain toxins, such as membrane interaction, retrograde trafficking, and carbohydrate binding, provide robust probes to comprehensively investigate the lipid biosynthesis, membrane vesicle transport, and glycosylation pathways, respectively. This review specifically focuses on recent representative toxin-based genetic screens that have identified new players involved in and provided new insights into fundamental biological pathways, such as glycosphingolipid biosynthesis, protein glycosylation, and membrane vesicle trafficking pathways. Functionally characterizing these newly identified factors not only expands our current understanding of toxin biology but also enables a deeper comprehension of fundamental biological questions. Consequently, it stimulates the development of new therapeutic approaches targeting both bacterial infectious diseases and genetic disorders with defects in these factors and pathways.

SREBP-1 upregulates lipophagy to maintain cholesterol homeostasis in brain tumor cells

Cholesterol is a structural component of cell membranes. How rapidly growing tumor cells maintain membrane cholesterol homeostasis is poorly understood. Here, we found that glioblastoma (GBM), the most lethal brain tumor, maintains normal levels of membrane cholesterol but with an abundant presence of cholesteryl esters (CEs) in its lipid droplets (LDs). Mechanistically, SREBP-1 (sterol regulatory element-binding protein 1), a master transcription factor that is activated upon cholesterol depletion, upregulates critical autophagic genes, including ATG9B, ATG4A, and LC3B, as well as lysosome cholesterol transporter NPC2. This upregulation promotes LD lipophagy, resulting in the hydrolysis of CEs and the liberation of cholesterol from the lysosomes, thus maintaining plasma membrane cholesterol homeostasis. When this pathway is blocked, GBM cells become quite sensitive to cholesterol deficiency with poor growth in vitro. Our study unravels an SREBP-1-autophagy-LD-CE hydrolysis pathway that plays an important role in maintaining membrane cholesterol homeostasis while providing a potential therapeutic avenue for GBM.

Fatty acid desaturase 2 determines the lipidomic landscape and steroidogenic function of the adrenal gland

Corticosteroids regulate vital processes, including stress responses, systemic metabolism, and blood pressure. Here, we show that corticosteroid synthesis is related to the polyunsaturated fatty acid (PUFA) content of mitochondrial phospholipids in adrenocortical cells. Inhibition of the rate-limiting enzyme of PUFA synthesis, fatty acid desaturase 2 (FADS2), leads to perturbations in the mitochondrial lipidome and diminishes steroidogenesis. Consistently, the adrenocortical mitochondria of Fads2-/- mice fed a diet with low PUFA concentration are structurally impaired and corticoid levels are decreased. On the contrary, FADS2 expression is elevated in the adrenal cortex of obese mice, and plasma corticosterone is increased, which can be counteracted by dietary supplementation with the FADS2 inhibitor SC-26192 or icosapent ethyl, an eicosapentaenoic acid ethyl ester. In humans, FADS2 expression is elevated in aldosterone-producing adenomas compared to non-active adenomas or nontumorous adrenocortical tissue and correlates with expression of steroidogenic genes. Our data demonstrate that FADS2-mediated PUFA synthesis determines adrenocortical steroidogenesis in health and disease.

The History and Science of the Major Birch Pollen Allergen Bet v 1

The term allergy was coined in 1906 by the Austrian scientist and pediatrician Clemens Freiherr von Pirquet. In 1976, Dietrich Kraft became the head of the Allergy and Immunology Research Group at the Department of General and Experimental Pathology of the University of Vienna. In 1983, Kraft proposed to replace natural extracts used in allergy diagnostic tests and vaccines with recombinant allergen molecules and persuaded Michael Breitenbach to contribute his expertise in molecular cloning as one of the mentors of this project. Thus, the foundation for the Vienna School of Molecular Allergology was laid. With the recruitment of Heimo Breiteneder as a young molecular biology researcher, the work began in earnest, resulting in the publication of the cloning of the first plant allergen Bet v 1 in 1989. Bet v 1 has become the subject of a very large number of basic scientific as well as clinical studies. Bet v 1 is also the founding member of the large Bet v 1-like superfamily of proteins with members-based on the ancient conserved Bet v 1 fold-being present in all three domains of life, i.e., archaea, bacteria and eukaryotes. This suggests that the Bet v 1 fold most likely already existed in the last universal common ancestor. The biological function of this protein was probably related to lipid binding. However, during evolution, a functional diversity within the Bet v 1-like superfamily was established. The superfamily comprises 25 families, one of which is the Bet v 1 family, which in turn is composed of 11 subfamilies. One of these, the PR-10-like subfamily of proteins, contains almost all of the Bet v 1 homologous allergens from pollen and plant foods. Structural and functional comparisons of Bet v 1 and its non-allergenic homologs of the superfamily will pave the way for a deeper understanding of the allergic sensitization process.

Multiple tethers of organelle contact sites are involved in α-synuclein toxicity in yeast

The protein α-synuclein (α-syn) is one of the major factors linked to Parkinson's disease, yet how its misfolding and deposition contribute to the pathology remains largely elusive. Recently, contact sites among organelles were implicated in the development of this disease. Here, we used the budding yeast Saccharomyces cerevisiae, in which organelle contact sites have been characterized extensively, as a model to investigate their role in α-syn cytotoxicity. We observed that lack of specific tethers that anchor the endoplasmic reticulum to the plasma membrane resulted in cells with increased resistance to α-syn expression. Additionally, we found that strains lacking two dual-function proteins involved in contact sites, Mdm10 and Vps39, were resistant to the expression of α-syn. In the case of Mdm10, we found that this is related to its function in mitochondrial protein biogenesis and not to its role as a contact site tether. In contrast, both functions of Vps39, in vesicular transport and as a tether of the vacuole-mitochondria contact site, were required to support α-syn toxicity. Overall, our findings support that interorganelle communication through membrane contact sites is highly relevant for α-syn-mediated toxicity.

Maternal Magnolol Supplementation during Pregnancy and Lactation Promotes Antioxidant Capacity, Improves Gut Health, and Alters Gut Microbiota and Metabolites of Weanling Piglets

Maternal nutrition exerts a profound effect on the postnatal performance of offspring, especially during the weaning period. The multifunctional bioactive component magnolol (MAG) has shown promise as a dietary supplement. This study aimed to explore the effects of maternal MAG supplementation on the antioxidant capacity, gut health, gut microbiome, and metabolome composition of weanling piglets. Fifty pregnant sows were randomly divided into two equally sized groups, the control group and the group supplemented with 100 g/t MAG during the gestation and lactation periods, and 7 days postweaning, the pups were euthanized. The microbiome and metabolome features of weanling piglet colons were compared. Our results revealed that maternal MAG supplementation modified the serum redox status of weanling piglets by decreasing malondialdehyde concentration and increasing superoxide dismutase activity and total antioxidant capacity. Moreover, the decreased indicators of diarrhea were accompanied by improved gut barrier function, in which serum diamine oxidase concentration was decreased, and expressions of zona occludens-1, claudin-1, and intestinal alkaline phosphatase were increased in the colon of weanling piglets from sows supplemented with MAG. Further analysis of the gut microbiota indicated that maternal MAG supplementation significantly increased the relative abundance of beneficial bacteria in the colon of weanling piglets, including Faecalibacterium prausnitzii and Oscillospira. Metabolome analysis identified 540 differential metabolites in the colon of piglets from MAG-fed dams, of which glycerophospholipid classes were highly correlated with progeny gut health and key beneficial bacteria. Our findings indicated that maternal MAG supplementation can improve the oxidative status and gut health of weanling piglets, possibly due to alterations in the gut microbiota and metabolites.

New Pieces for an Old Puzzle: Approaching Parkinson's Disease from Translatable Animal Models, Gut Microbiota Modulation, and Lipidomics

Parkinson's disease (PD) is a severe neurodegenerative disease characterized by disabling motor alterations that are diagnosed at a relatively late stage in its development, and non-motor symptoms, including those affecting the gastrointestinal tract (mainly constipation), which start much earlier than the motor symptoms. Remarkably, current treatments only reduce motor symptoms, not without important drawbacks (relatively low efficiency and impactful side effects). Thus, new approaches are needed to halt PD progression and, possibly, to prevent its development, including new therapeutic strategies that target PD etiopathogeny and new biomarkers. Our aim was to review some of these new approaches. Although PD is complex and heterogeneous, compelling evidence suggests it might have a gastrointestinal origin, at least in a significant number of patients, and findings in recently developed animal models strongly support this hypothesis. Furthermore, the modulation of the gut microbiome, mainly through probiotics, is being tested to improve motor and non-motor symptoms and even to prevent PD. Finally, lipidomics has emerged as a useful tool to identify lipid biomarkers that may help analyze PD progression and treatment efficacy in a personalized manner, although, as of today, it has only scarcely been applied to monitor gut motility, dysbiosis, and probiotic effects in PD. Altogether, these new pieces should be helpful in solving the old puzzle of PD.

Targeted Lipidomics Reveals a Novel Role for Glucosylceramides in Glucose Response

The addition of excess glucose to the diet drives a coordinated response of lipid metabolism pathways to tune the membrane composition to the altered diet. Here, we have employed targeted lipidomic approaches to quantify the specific changes in the phospholipid and sphingolipid populations that occur in elevated glucose conditions. The lipids within wildtype Caenorhabditis elegans are strikingly stable with no significant changes identified in our global mass spectrometry-based analysis. Previous work has identified ELO-5, an elongase that is critical for the synthesis of monomethyl-branched chain fatty acids (mmBCFAs), as essential for surviving elevated glucose conditions. Therefore, we performed targeted lipidomics on elo-5 RNAi-fed animals and identified several significant changes in these animals in lipid species that contain mmBCFAs as well as in species that do not contain mmBCFAs. Of particular note, we identified a specific glucosylceramide (GlcCer 17:1;O2/22:0;O) that is also significantly upregulated with glucose in wildtype animals. Furthermore, compromising the production of the glucosylceramide pool with elo-3 or cgt-3 RNAi leads to premature death in glucose-fed animals. Taken together, our lipid analysis has expanded the mechanistic understanding of metabolic rewiring with glucose feeding and has identified a new role for the GlcCer 17:1;O2/22:0;O.

Impact of sphingolipids on protein membrane trafficking

Membrane trafficking is essential to maintain the spatiotemporal control of protein and lipid distribution within membrane systems of eukaryotic cells. To achieve their functional destination proteins are sorted and transported into lipid carriers that construct the secretory and endocytic pathways. It is an emerging theme that lipid diversity might exist in part to ensure the homeostasis of these pathways. Sphingolipids, a chemical diverse type of lipids with special physicochemical characteristics have been implicated in the selective transport of proteins. In this review, we will discuss current knowledge about how sphingolipids modulate protein trafficking through the endomembrane systems to guarantee that proteins reach their functional destination and the proposed underlying mechanisms.