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This study aimed to investigate the efficacy of a composite coating composed of 150 mg/L ε-Poly-L-lysine (ε-PL) and 5 g/L chitosan (CTS) in extending the shelf life and maintaining the postharvest quality of fresh Tremella fuciformis. Freshly harvested T. fuciformis were treated by surface spraying, with distilled water serving as the control. The effects of the coating on storage quality, physicochemical properties, reactive oxygen species (ROS) metabolism, and membrane lipid metabolism were evaluated during storage at (25 ± 1) °C. The results showed that the ε-PL/CTS composite coating significantly retarded quality deterioration, as evidenced by reduced weight loss, maintained whiteness and color, and higher retention of soluble sugars, soluble solids, and soluble proteins. The coating also effectively limited water migration and loss. Mechanistically, the coated T. fuciformis exhibited enhanced antioxidant capacity, characterized by increased superoxide anion (O2−) resistance capacity, higher activities of antioxidant enzymes (SOD, CAT, APX), and elevated levels of non-enzymatic antioxidants (AsA, GSH). This led to a significant reduction in malondialdehyde (MDA) accumulation, alongside improved DPPH radical scavenging activity and reducing power. Furthermore, the ε-PL/CTS coating preserved cell membrane integrity by inhibiting the activities of lipid-degrading enzymes (lipase, LOX, PLD), maintaining higher levels of key phospholipids (phosphatidylinositol and phosphatidylcholine), delaying phosphatidic acid accumulation, and consequently reducing cell membrane permeability. In conclusion, the ε-PL/CTS composite coating effectively extends the shelf life and maintains the quality of postharvest T. fuciformis by modulating ROS metabolism and preserving membrane lipid homeostasis. This study provides a theoretical basis and a practical approach for the quality control of fresh T. fuciformis.

Sweet sorghum has strong stress resistance and is considered a promising energy crop. In the present study, the effects of salt on the membrane lipid metabolism of two sweet sorghum inbred lines (salt-tolerant M-81E and salt-sensitive Roma) were analyzed. After treatment with 150 mM NaCl, higher levels of fresh weight and chlorophyll fluorescence, as well as lower levels of malondialdehyde (MDA) were found in salt-tolerant M-81E. Concomitantly, 702 and 1339 differentially expression genes (DEGs) in M-81E and Roma were identified in response to salt stress. We determined that most DEGs were related to glycerophospholipid metabolism, glycerolipid metabolism, and other membrane lipid metabolisms. Under NaCl treatment, the expression of the membrane-associated phospholipase A1 was down-regulated at the transcriptional level, along with an increased content of phosphatidylcholine (PC) in both cultivars. The inhibition of triacylglycerol (TAG) mobilization in M-81E delayed salt-induced leaf senescence. Furthermore, enhanced levels of glycerol-3-phosphate acyltransferase (GPAT) expression contributed to improved salt resistance in M-81E. The results of this study demonstrate membrane the role of lipid regulation in mediating salt-defensive responses in sweet sorghum and expand our understanding of the relationship between changes in membrane lipid content and salt resistance.

Key Points Cellular membranes are laterally heterogeneous and consist of transient and dynamic domains with varying properties, which prominently include ordered lipid-driven domains that are referred to as lipid (or membrane) rafts. Membrane domains can be induced and regulated by a variety of interactions, which include specific lipid–lipid and lipid–protein interactions, bulk membrane properties, and interactions between membrane components and the underlying cytoskeleton. Advanced microscopy and biochemistry techniques facilitate the study of membrane domains; however, these domains still elude direct in vivo visualization. The multiplicity of possible organizational states and their context-dependent nature most likely account for experimental inconsistencies. Membrane rafts potentially have crucial physiological roles across cell types that range from immune cells to cancer cells. Membrane domains are conserved throughout the domains of life, which supports their functional importance in biological systems. Lipid rafts are relatively ordered membrane domains that are enriched in cholesterol and saturated lipids, and selectively recruit other lipids and proteins. They are dynamic and heterogeneous in composition and are thus challenging to visualize in vivo . New technologies are providing novel insights into the formation, organization and functions of these membrane domains. Cellular plasma membranes are laterally heterogeneous, featuring a variety of distinct subcompartments that differ in their biophysical properties and composition. A large number of studies have focused on understanding the basis for this heterogeneity and its physiological relevance. The membrane raft hypothesis formalized a physicochemical principle for a subtype of such lateral membrane heterogeneity, in which the preferential associations between cholesterol and saturated lipids drive the formation of relatively packed (or ordered) membrane domains that selectively recruit certain lipids and proteins. Recent studies have yielded new insights into this mechanism and its relevance in vivo , owing primarily to the development of improved biochemical and biophysical technologies.

The lipid composition of cellular organelles is tailored to suit their specialized tasks. A fundamental transition in the lipid landscape divides the secretory pathway in early and late membrane territories, allowing an adaptation from biogenic to barrier functions. Defending the contrasting features of these territories against erosion by vesicular traffic poses a major logistical problem. To this end, cells evolved a network of lipid composition sensors and pipelines along which lipids are moved by non-vesicular mechanisms. We review recent insights into the molecular basis of this regulatory network and consider examples in which malfunction of its components leads to system failure and disease.

Cholesterol is an integral component of eukaryotic cell membranes and a key molecule in controlling membrane fluidity, organization, and other physicochemical parameters. It also plays a regulatory function in antibiotic drug resistance and the immune response of cells against viruses, by stabilizing the membrane against structural damage. While it iswell understood that, structurally, cholesterol exhibits a densification effect on fluid lipid membranes, its effects on membrane bending rigidity are assumed to be nonuniversal; i.e., cholesterol stiffens saturated lipid membranes, but has no stiffening effect on membranes populated by unsaturated lipids, such as 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). This observation presents a clear challenge to structure–property relationships and to our understanding of cholesterol-mediated biological functions. Here, using a comprehensive approach—combining neutron spin-echo (NSE) spectroscopy, solid-state deuterium NMR (²H NMR) spectroscopy, and molecular dynamics (MD) simulations—we report that cholesterol locally increases the bending rigidity of DOPC membranes, similar to saturated membranes, by increasing the bilayer’s packing density. All three techniques, inherently sensitive to mesoscale bending fluctuations, show up to a threefold increase in effective bending rigidity with increasing cholesterol content approaching a mole fraction of 50%. Our observations are in good agreement with the known effects of cholesterol on the area-compressibility modulus and membrane structure, reaffirming membrane structure–property relationships. The current findings point to a scale-dependent manifestation of membrane properties, highlighting the need to reassess cholesterol’s role in controlling membrane bending rigidity over mesoscopic length and time scales of important biological functions, such as viral budding and lipid–protein interactions.

Lipidomics is an important aspect of personalized medicine in relation to nutrition and metabolism. This approach has become important due to the substantial presence of nutraceuticals in the market, since it gives personalized criteria on how to choose the right nutraceutical strategy for both prevention and for quality of life. This multi-disciplinary textbook uses a simple and practical approach to provide a comprehensive overview of lipidomics and their connection with health and nutrition. The text is divided into two parts:    -  Part 1 outlines the basics of lipidomics and focuses on the biochemical and nutritional aspects with descriptions of the analytical methods employed for the examination of cell membrane fatty acid composition.    - Part 2 familiarizes the reader with the use of membrane lipidomic diagnostics in practical health care, using health conditions as examples to introduce the concept of lipidomic profiles in different physiological and pathological situations including prevention. Through the various properties of membrane lipidomics, readers will be able to combine the molecular status of the cell membrane with the evaluation of the subject for personalized nutritional and nutraceutical strategies. Membrane Lipidomics for Personalized Health will be beneficial to biologists, biochemists and medical researchers, as well as health care professionals, pharmacists, and nutritionists seeking in-depth information on the topic.

Tumor-associated macrophages (TAMs) display pro-tumorigenic phenotypes for supporting tumor progression in response to microenvironmental cues imposed by tumor and stromal cells. However, the underlying mechanisms by which tumor cells instruct TAM behavior remain elusive. Here, we uncover that tumor-cell-derived glucosylceramide stimulated unconventional endoplasmic reticulum (ER) stress responses by inducing reshuffling of lipid composition and saturation on the ER membrane in macrophages, which induced IRE1-mediated spliced XBP1 production and STAT3 activation. The cooperation of spliced XBP1 and STAT3 reinforced the pro-tumorigenic phenotype and expression of immunosuppressive genes. Ablation of XBP1 expression with genetic manipulation or ameliorating ER stress responses by facilitating LPCAT3-mediated incorporation of unsaturated lipids to the phosphatidylcholine hampered pro-tumorigenic phenotype and survival in TAMs. Together, we uncover the unexpected roles of tumor-cell-produced lipids that simultaneously orchestrate macrophage polarization and survival in tumors via induction of ER stress responses and reveal therapeutic targets for sustaining host antitumor immunity. Tumor-associated macrophages support an immunosuppressive tumor microenvironment. Di Conza et al. uncover how IRE1–XBP1 and IRE1−STAT3 endoplasmic reticulum stress responses pathways are engaged by tumor-derived lipids to orchestrate pro-tumorigenic features and survival in tumor-associated macrophages.

Cellular membranes are formed from a chemically diverse set of lipids present in various amounts and proportions. A high lipid diversity is universal in eukaryotes and is seen from the scale of a membrane leaflet to that of a whole organism, highlighting its importance and suggesting that membrane lipids fulfil many functions. Indeed, alterations of membrane lipid homeostasis are linked to various diseases. While many of their functions remain unknown, interdisciplinary approaches have begun to reveal novel functions of lipids and their interactions. We are beginning to understand why even small changes in lipid structures and in composition can have profound effects on crucial biological functions.

A new mass-spectrometry method has been developed to obtain high-resolution spectra of folded proteins bound to lipids; using this technique as well as X-ray crystallography provides evidence for membrane protein conformational change as a result of lipid–protein interaction. Lipid bound to influence protein structure Many of the high-resolution membrane protein structures published recently are notable for the presence of lipids closely associated with the protein, prompting the question, how are these lipids influencing membrane complex structure? Carol Robinson and colleagues have developed a new ion mobility mass spectrometry (IM-MS) method that enabled them to obtain mass spectra of folded protein conformations bound to lipids. Using this method they identified lipids that altered the stability of MscL (mechanosensitive channel of large conductance), aquaporin Z and the ammonia channel. They then determined the X-ray crystal structure of the ammonia channel bound to one of these lipids (phosphatidylglycerol), which revealed how a conformational change in a specific loop led to the formation of a phosphatidylglycerol-binding site. The major conclusion from this work is that an individual lipid-binding event can change the stability of a membrane complex. On the cover, IM-MS captures a native membrane protein complex emerging from an ion mobility cell. Shown is the ammonia channel in apo, one- and two-lipid bound states. Previous studies have established that the folding, structure and function of membrane proteins are influenced by their lipid environments 1 , 2 , 3 , 4 , 5 , 6 , 7 and that lipids can bind to specific sites, for example, in potassium channels 8 . Fundamental questions remain however regarding the extent of membrane protein selectivity towards lipids. Here we report a mass spectrometry approach designed to determine the selectivity of lipid binding to membrane protein complexes. We investigate the mechanosensitive channel of large conductance (MscL) from Mycobacterium tuberculosis and aquaporin Z (AqpZ) and the ammonia channel (AmtB) from Escherichia coli , using ion mobility mass spectrometry (IM-MS), which reports gas-phase collision cross-sections. We demonstrate that folded conformations of membrane protein complexes can exist in the gas phase. By resolving lipid-bound states, we then rank bound lipids on the basis of their ability to resist gas phase unfolding and thereby stabilize membrane protein structure. Lipids bind non-selectively and with high avidity to MscL, all imparting comparable stability; however, the highest-ranking lipid is phosphatidylinositol phosphate, in line with its proposed functional role in mechanosensation 9 . AqpZ is also stabilized by many lipids, with cardiolipin imparting the most significant resistance to unfolding. Subsequently, through functional assays we show that cardiolipin modulates AqpZ function. Similar experiments identify AmtB as being highly selective for phosphatidylglycerol, prompting us to obtain an X-ray structure in this lipid membrane-like environment. The 2.3 Å resolution structure, when compared with others obtained without lipid bound, reveals distinct conformational changes that re-position AmtB residues to interact with the lipid bilayer. Our results demonstrate that resistance to unfolding correlates with specific lipid-binding events, enabling a distinction to be made between lipids that merely bind from those that modulate membrane protein structure and/or function. We anticipate that these findings will be important not only for defining the selectivity of membrane proteins towards lipids, but also for understanding the role of lipids in modulating protein function or drug binding.

Lipids are distributed in a highly heterogeneous fashion in different cellular membranes. Only a minority of lipids achieve their final intracellular distribution through transport by vesicles. Instead, the bulk of lipid traffic is mediated by a large group of lipid transfer proteins (LTPs), which move small numbers of lipids at a time using hydrophobic cavities that stabilize lipid molecules outside membranes. Although the first LTPs were discovered almost 50 years ago, most progress in understanding these proteins has been made in the past few years, leading to considerable temporal and spatial refinement of our understanding of the function of these lipid transporters. The number of known LTPs has increased, with exciting discoveries of their multimeric assembly. Structural studies of LTPs have progressed from static crystal structures to dynamic structural approaches that show how conformational changes contribute to lipid handling at a sub-millisecond timescale. A major development has been the finding that many intracellular LTPs localize to two organelles at the same time, forming a shuttle, bridge or tube that links donor and acceptor compartments. The understanding of how different lipids achieve their final destination at the molecular level allows a better explanation of the range of defects that occur in diseases associated with lipid transport and distribution, opening up the possibility of developing therapies that specifically target lipid transfer.