Cell Membrane Components Research Articles

Synthesis of azide-modified glycerophospholipid precursor analogs for detection of enzymatic reactions.

Glycerophospholipids (GPLs) are major cell membrane components. Although various phosphorylated molecules are attached to lipid moieties as their headgroups, GPLs are biosynthesized from phosphatidic acid (PA) via its derivatives, diacylglycerol (DAG) or cytidine diphosphate diacylglycerol (CDP-DAG). A variety of molecular probes capable of introducing detection tags have been developed to investigate biological events involved in GPLs. In this study, we report the design, synthesis, and evaluation of novel analytical tools suitable to monitor the activity of GPL biosynthetic enzymes in vitro. Our synthetic targets, namely, azide-modified PA, azide-modified DAG, and azide-modified CDP-DAG, were successfully obtained from solketal as their common starting material. Moreover, using CDP-diacylglycerol-inositol 3-phosphatidyltransferase (CDIPT), an enzyme that catalyzed the final reaction step in synthesizing phosphatidylinositol, we demonstrated that azide-modified CDP-DAG worked as a substrate for CDIPT.

Impact of De Novo Cholesterol Biosynthesis on the Initiation and Progression of Breast Cancer.

Cholesterol (CHOL) is a multifaceted lipid molecule. It is an essential structural component of cell membranes, where it cooperates in regulating the intracellular trafficking and signaling pathways. Additionally, it serves as a precursor for vital biomolecules, including steroid hormones, isoprenoids, vitamin D, and bile acids. Although CHOL is normally uptaken from the bloodstream, cells can synthesize it de novo in response to an increased requirement due to physiological tissue remodeling or abnormal proliferation, such as in cancer. Cumulating evidence indicated that increased CHOL biosynthesis is a common feature of breast cancer and is associated with the neoplastic transformation of normal mammary epithelial cells. After an overview of the multiple biological activities of CHOL and its derivatives, this review will address the impact of de novo CHOL production on the promotion of breast cancer with a focus on mammary stem cells. The review will also discuss the effect of de novo CHOL production on in situ and invasive carcinoma and its impact on the response to adjuvant treatment. Finally, the review will discuss the present and future therapeutic strategies to normalize CHOL biosynthesis.

Effect of cholesterol on nanoparticle translocation across a lipid bilayer.

Nanoparticles (NPs) have attracted significant attention as carriers for the delivery of drugs, genes, and macromolecules for biomedical and therapeutic applications. These technologies require NPs to be delivered to the interior of the cell. However, this translocation is unlikely because of the presence of a cell membrane composed of phospholipids, cholesterol, proteins, and glycans. The cell membrane composition can influence its rigidity; thus, membrane composition is a crucial factor in determining the translocation of NPs across the cell membrane. Here, we focus on cholesterol, which is an essential component of biological cell membranes, and investigate NP translocation across membranes containing cholesterol under an applied electric field using a coarse-grained molecular dynamics simulation. We found that NPs could translocate directly across cholesterol-containing membranes without irreversible membrane disruption. This unique translocation was induced by two key phenomena. Before NP translocation, a phospholipid-rich/cholesterol-poor domain was formed at the NP-membrane contact interface. Second, a smaller transmembrane pore was formed in the cholesterol-containing membrane during membrane crossing of the NP. Our findings imply that the delivery of NPs to the cell interior across the cholesterol-containing membrane can be achieved by appropriately controlling the strength of the applied electric field, depending on the cholesterol content in the membrane.

Evaluation of functional transbilayer coupling in live cells by controlled lipid exchange and imaging fluorescence correlation spectroscopy.

Biophysical coupling between the inner and outer leaflets, known as inter-leaflet or transbilayer coupling, is a fundamental organizational principle in the plasma membranes of live mammalian cells. Lipid-based interactions between the two leaflets are proposed to be a primary mechanism underlying transbilayer coupling. However, there are only a few experimental evidence supporting the existence of such interactions in live cells. This is seemingly due to the lack of experimental strategies to perturb the lipid composition in one leaflet and quantitative techniques to evaluate the biophysical properties of the opposite leaflet. The existing strategies often dependent on immobilization and clustering a component in one of the leaflets and technically demanding biophysical tools to evaluate the effects on the opposing leaflet. In the recent years, the London group developed a simple but elegant method, namelymethyl-alpha-cyclodextrin catalyzed lipid exchange (LEX), to efficiently exchange outer leaflet lipids with an exogenous lipid of choice. Here, we adopted this method to perturb outer leaflet lipid composition. The corresponding changes in the inner leaflet is evaluated by comparing the diffusion of lipid probes localized in this leaflet in unperturbed and perturbed conditions. We employed highly multiplexed imaging fluorescence correlation spectroscopy (ImFCS), realized in a commercially available or home-built total internal reflection fluorescence microsocope equipped with a fast and sensitive camera, to determine diffusion coefficient of the lipid probes. Using the combination of LEX and ImFCS, we directly demonstrate lipid-based transbilayer coupling that does not require immobilization of membrane components in live mast cells in resting conditions. Overall, we present a relatively straightforward experimental strategy to evaluate transbilayer coupling quantitively in live cells.

Application of synthetic biology strategies to promote biosynthesis of fatty acids and their derivatives.

Fatty acids and their derivatives are indispensable biomolecules in all organisms, and can be used as intermediates in the synthesis of pharmaceuticals, biofuels and pesticides, and thus their demand has increased dramatically in recent years. In addition to serving as structural components of cell membranes and metabolic energy, fatty acids and their derivatives can also be used as signal transduction and regulatory bioactive molecules to regulate cell functions. Biosynthesis of fatty acids and their derivatives through microbial catalysis provides green and alternative options to meet the goal. However, the low biosynthetic titer of fatty acids and their derivatives limits their industrial production and application. In this review, we first summarize the metabolic pathways and related enzymes of fatty acids and their derivatives biosynthesis. Then, the strategies and research progress of biosynthesis of fatty acids and derivatives through metabolic and enzyme engineering were reviewed. The biosynthesis of saturated fatty acids (medium chain fatty acids and long chain fatty acids), bioactive fatty acids (PUFAs, oxylipins, ether lipids), and their derivatives with microbial and enzymatic catalysis were respectively summarized. Finally, synthetic biology strategies to improve fatty acids and their derivatives production through enzyme rational design, carbon metabolism flux, cofactors balance, and metabolic pathways design were discussed. The review provides references and prospects for fatty acids and their derivatives biosynthesis and industrial production.

Branched-Chain Amino Acid Degradation Pathway was Inactivated in Colorectal Cancer: Results from a Proteomics Study.

Background: Colorectal cancer (CRC) ranks third in terms of cancer incidence and fourth in terms of cancer-related deaths worldwide. Identifying potential biomarkers of CRC is crucial for treatment and drug development. Methods: In this study, we established a C57B/6N mouse model of colon carcinogenesis using azoxymethane-dextran sodium sulfate (AOM-DSS) treatment for 14 weeks to identify proteins associated with colon cancer. An isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic analysis was conducted on the cell membrane components enriched in the colonic mucosa. Additionally, tumor tissues and adjacent normal colon tissues were collected from patients with colon cancer for comparative protein and metabolite analyses. Results: In total, 74 differentially expressed proteins were identified in the tumor tissue samples from AOM/DSS-treated mice compared to both the adjacent tissue samples from AOM/DSS-treated mice and tissue samples from saline-treated control mice. Bioinformatics analysis revealed eight downregulated proteins enriched in the branched-chain amino acids pathway (valine, leucine, and isoleucine degradation). Moreover, these proteins are already known to be associated with the survival rate of patients with cancer. Targeted metabolomics showed increased levels of valine, leucine, and isoleucine in tumor tissues compared to those in adjacent normal tissues in patients with colon cancer. Furthermore, a real-time PCR experiment demonstrated that Aldehyde dehydrogenase, mitochondrial (short protein name ALDH2, gene name Aldh2) and Hydroxyacyl-coenzyme A dehydrogenase, mitochondrial (short protein name HCDH, gene name Hadh) (two genes) in the pathway of branched-chain amino acids) were downregulated in patients with colon cancer (colon tumor tissues vs. their adjacent colon tissues). ALDH2 expression was further validated by western blotting in AOM/DSS-treated mouse model and in clinical samples. Conclusion: This study highlighted the inactivation of the branched-chain amino acid degradation pathway in colon cancer and identified ALDH2 and HCDH as potential biomarkers for diagnosing colon cancer and developing new therapeutic strategies.

Not all plaques are created equal: Uncovering a unique molecular signature in Alzheimer's disease.

Although neuritic plaques - comprised of aggregated fibrils of the misfolded protein, amyloid β (Aβ) - have formed a central focus of Alzheimer's disease (AD) research for decades, it is now well understood that plaque burden alone is a poor correlate of cognitive decline. This is highlighted especially when compared against other neuropathological hallmarks, such as synapse loss (the strongest correlate) and hyperphosphorylated protein tau. However, it is known that Familial AD arises due to autosomal dominant mutations directly influencing the generation of Aβ, suggesting that Aβ pathology may play a key upstream role in the disease. Such contrasting lines of evidence have thus raised questions as to why some aged individuals with high plaque burden develop AD while others remain cognitively healthy. In their recent study, published in Analytical Chemistry (June 2024), Enzlein and colleagues aimed to investigate whether differences in the molecular composition of plaques between individuals with sporadic Alzheimer's disease (N = 9) versus age-matched amyloid positive but cognitively unaffected controls (N = 8) could go towards explaining this outstanding question in the field. Using novel methods integrating mass spectrometry imaging with machine learning feature extraction, the authors compared peptide and lipid profiles to a resolving limit of 400 μm2 for >5000 individual plaques. In doing so, a distinct peptide signature was identified in sporadic Alzheimer's disease plaques that was characterised by strongly increased aggregation of the short amyloid β isoform, Aβ1-38 coupled with a lesser co-aggregation of pyroglutamate-modified Aβ3-42pE. Sporadic Alzheimer's disease plaques also demonstrated a robust lipid signature denoted by an increased presence of cell membrane components, GM1 and GM2 gangliosides. Here, we review this work; aiming to place these findings within the context of existing literature and with a view to discussing their importance in developing our current knowledge of Alzheimer's disease.

Antiphospholipid Antibody Testing: An Audit on Testing Practices in a Public Tertiary Care Center.

Antiphospholipid antibodies (aPLs) are antibodies directed against cell membrane components and can be associated with clinical features or be asymptomatic. Testing and interpreting these antibodies is associated with many challenges and pitfalls in clinical practice. To review all antiphospholipid antibody testing and describe the testing practices, indications for testing and interpretation of results to infer local challenges with aPL testing and subsequently address ways to overcome those challenges. This is a retrospective analysis of all aPL testing done in a tertiary center between 2014 and 2018. Characteristics of study patients collected through chart review were described using the mean and standard deviation for continuous variables and proportion for categorical variables. Group differences were compared between patients with any aPL-positive result and those with no positive result using chi-square or Fisher's exact test as appropriate for categorical variables and a simple regression model for numerical variables. Among 414 patients undergoing aPL testing, mainly adult females, 62 (14.9%) patients had at least one positive antibody, of those, 26 (42%) had repeat testing done. Testing was mostly done for obstetric indication (107, 25.8%), with 36 patients having one or two early pregnancy losses <10 weeks as their testing indication. A total of 27 (6.5%) patients were labeled with APS/possible APS based on chart review, but on review of the testing of those patients according to classification criteria, only nine patients satisfied the criteria for APS. This study highlights the clinical challenges associated with aPL testing, including the controversies around indication for testing, the low rates of repeat testing to confirm persistence, and the common misinterpretation of results. Having an aPL testing profile, explicit reference ranges, results commentary, and close interaction between ordering physicians and laboratory staff might be starting points to overcome these challenges.

Cholesterol de novo biosynthesis: a promising target to overcome the resistance to aromatase inhibitors in postmenopausal patients with estrogen receptor-positive breast cancer

Aim: Cholesterol is an essential component of cell membranes and serves as a precursor for several bioactive molecules, including steroid hormones and isoprenoids. Generally supplied by the bloodstream, the de novo cholesterol biosynthesis is activated in response to an increased cell requirement due to normal tissue remodeling or tumor proliferation. In estrogen receptor (ER)-positive breast cancers, cholesterol biosynthesis may promote and sustain tumor growth and concur with the failure of the treatment with aromatase inhibitors. Methods: In this study, the comparison of gene compared the expression involved in cholesterol biosynthesis was conducted in ER-positive tumors that were responsive and nonresponsive to letrozole; besides, an exploration of their association with genes implicated in estrogen production, the Hippo pathway, and cell cycle control was performed. Results: In responsive tumors, letrozole significantly decreased the expression of five genes [acetyl-coenzyme A (CoA) acetyltransferase 2 (ACAT2), 3-hydroxy-3-methylglutaryl-CoA synthase 1 (HMGCS1), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), farnesyl diphosphate synthase (FDPS), and squalene epoxidase (SQLE)] crucial for the biosynthetic process. Conversely, in nonresponsive tumors, these genes were unaffected by letrozole but associated with several genes involved in estrogens production [cytochrome P450 family 19 subfamily A member 1 (CYP19A1), hydroxysteroid 17-beta dehydrogenase 2 (HSD17B2), and sulfotransferase family 1A member 1 (SULT1A1)], cell cycle [control cyclin dependent kinase 4 (CDK4) and CDK6], and Hippo pathway [Yes1 associated transcriptional regulator (YAP1) and baculoviral inhibitor of apoptosis (IAP) repeat containing 5 (BIRC5)]. Conclusions: The findings corroborated the notion that the dysregulation of the mevalonate pathway may contribute to the resistance to letrozole and supported the use of statins to contrast this metabolic dysfunction.

γ irradiation mediated the inhibitory effect of Ca2+ signals on softening of blueberry fruit during cold storage

Postharvest blueberries tend to soften and rot, resulting in serious fruit waste. Gamma (γ) irradiation can delay the softening of blueberries and improve fruit quality. Calcium is a structural component of plant cell wall and membrane, and plays a role as a second messenger in the physiological process of fruit. To explore the mechanism of inhibiting the softening of cold storage blueberry fruit by γ irradiation, ‘Bluecrop’ blueberry fruit were treated by γ irradiation at a dose of 2.5 kGy, and then combined with calcium ion (Ca2+) inhibitors and intracellular calmodulin antagonists. The Ca2+ fluorescence signals, fruit firmness, protopectin and different soluble pectin contents, cellulose and hemicellulose contents, and hydrolase activities were detected. Results showed that irradiation induced Ca2+ release from intracellular calcium store to generate fluorescence signals. Irradiation mediated the Ca2+ signals to exert a positive effect on fruit firmness of blueberries during cold storage, for the degradation of protopectin and chelator-soluble pectin to water-soluble pectin was reduced by inhibiting activities of polygalacturonase and pectin methylesterase. Therefore, γ irradiation-induced Ca2+ signals played an important role in regulation of pectin-involved fruit softening in blueberries during cold storage. This study provides a theoretical basis for the mechanism of Ca2+ signaling in blueberry storage.

Cholesterol is more readily oxidized than phospholipid linoleates in cell membranes to produce cholesterol hydroperoxides

Cholesterol is an essential component of cell membranes and serves as an important precursor of steroidal hormones and bile acids, but elevated levels of cholesterol and its oxidation products have been accepted as a risk factor for maintenance of health. The free and ester forms of cholesterol and fatty acids are the two major biological lipids. The aim of this hypothesis paper is to address the long-standing dogma that cholesterol is less susceptible to free radical peroxidation than polyunsaturated fatty acids (PUFAs). It has been observed that cholesterol is peroxidized much slower than PUFAs in plasma but that, contrary to expectations from chemical reactivity toward peroxyl radicals, cholesterol appears to be more readily autoxidized than linoleates in cell membranes. The levels of oxidation products of cholesterol and linoleates observed in humans support this notion. It is speculated that this discrepancy is ascribed to the fact that cholesterol and phospholipids bearing PUFAs are localized apart in raft and non-raft domains of cell membranes respectively and that the antioxidant vitamin E distributed predominantly in the non-raft domains cannot suppress the oxidation of cholesterol lying in raft domains which are relatively deficient in antioxidant.

Neurotensin counteracts hair growth inhibition induced by chronic restraint stress.

Stress has been considered as a potential trigger for hair loss through the neuroendocrine-hair follicle (HF) axis. Neurotensin (NTS), a neuropeptide, is known to be dysregulated in the inflammatory-associated skin diseases. However, the precise role of NTS in stress-induced hair loss is unclear. To investigate the function and potential mechanisms of NTS in stress-induced hair growth inhibition, we initially detected the expression of neurotensin receptor (Ntsr) and NTS in the skin tissues of stressed mice by RNA-sequencing and ELISA. We found chronic restraint stress (CRS) significantly decreased the expression of both NTS and Ntsr in the skin tissues of mice. Intracutaneous injection of NTS effectively counteracted CRS-induced inhibition of hair growth in mice. Furthermore, NTS regulated a total of 1093 genes expression in human dermal papilla cells (HDPC), with 591 genes being up-regulated and 502 genes being down-regulated. GO analysis showed DNA replication, cell cycle, integral component of plasma membrane and angiogenesis-associated genes were significantly regulated by NTS. KEGG enrichment demonstrated that NTS also regulated genes related to the Hippo signalling pathway, axon guidance, cytokine-cytokine receptor interaction and Wnt signalling pathway in HDPC. Our results not only uncovered the potential effects of NTS on stress-induced hair growth inhibition but also provided an understanding of the mechanisms at the gene transcriptional level.

Metabolic mechanism of Cr(VI) pollution remediation by Alicycliphilus denitrificans Ylb10

Cr(VI) is a well-known toxic pollutant and its remediation has attracted great attention. It is important to continuously discover and explore new high-efficiency Cr(VI) reducing bacteria to further improve the efficiency of Cr(VI) pollution remediation. In this paper, metabolic mechanism of Cr(VI) reduction in a new highly efficient Cr(VI) reducing bacterium, Alicycliphilus denitrificans Ylb10, was investigated. The results showed that Ylb10 could tolerate and completely reduce 450 mg/L Cr(VI). Cr(VI) can be reduced in the intracellular compartment, membrane and the extracellular compartment, with the plasma membrane being the main active site for Cr(VI) reduction. With the addition of NADH, the reduction efficiency of cell membrane components for Cr(VI) increased 2.3-fold. The omics data analysis showed that sulfite reductase CysJ, thiosulfate dehydrogenase TsdA, nitrite reductase NrfA, nitric oxide reductase NorB, and quinone oxidoreductase ChrR play important roles in the reduction of Cr(VI), in the intracellular, and the extracellular compartment, and the membrane of Ylb10, and therefore Cr(VI) was reduced by the combined action of several reductases at these three locations.

Identifying molecular tags selectively retained on the surface of brain endothelial cells to generate artificial targets for therapy delivery

Current strategies to identify ligands for brain delivery select candidates based on preferential binding to cell-membrane components (CMC) on brain endothelial cells (EC). However, such strategies generate ligands with inherent brain specificity limitations, as the CMC (e.g., the transferrin receptor TfR1) are also significantly expressed on peripheral EC. Therefore, novel strategies are required to identify molecules allowing increased specificity of therapy brain delivery. Here, we demonstrate that, while individual CMC are shared between brain EC and peripheral EC, their endocytic internalization rate is markedly different. Such differential endocytic rate may be harnessed to identify molecular tags for brain targeting based on their selective retention on the surface of brain EC, thereby generating ‘artificial’ targets specifically on the brain vasculature. By quantifying the retention of labelled proteins on the cell membrane, we measured the general endocytic rate of primary brain EC to be less than half that of primary peripheral (liver and lung) EC. In addition, through bio-panning of phage-displayed peptide libraries, we unbiasedly probed the endocytic rate of individual CMC of liver, lung and brain endothelial cells. We identified phage-displayed peptides which bind to CMC common to all three endothelia phenotypes, but which are preferentially endocytosed into peripheral EC, resulting in selective retention on the surface of brain EC. Furthermore, we demonstrate that the synthesized free-form peptides are capable of generating artificial cell-surface targets for the intracellular delivery of model proteins into brain EC with increasing specificity over time. The developed identification paradigm, therefore, demonstrates that the lower endocytic rate of individual CMC on brain EC can be harnessed to identify peptides capable of generating ‘artificial’ targets for the selective delivery of proteins into the brain vasculature. In addition, our approach identifies brain-targeting peptides which would have been overlooked by conventional identification strategies, thereby increasing the repertoire of candidates to achieve specific therapy brain delivery.

Cholesterol and Sphingomyelin Uniquely Alter the Rate of Transthyretin Aggregation and Decrease the Toxicity of Amyloid Fibrils.

Transthyretin (TTR) is a small tetrameric protein that aggregates, forming highly toxic oligomers and fibrils. In the blood and cerebrospinal fluid, TTR can interact with various biomolecules, phospho- and sphingolipids, and cholesterol on the red blood cell plasma membrane. However, the role of these molecules in TTR aggregation remains unclear. In this study, we investigated the extent to which phosphatidylcholine (PC), sphingomyelin (SM), and cholesterol (Cho), important components of plasma membranes, could alter the rate of TTR aggregation. We found that PC and SM inhibited TTR aggregation whereas Cho strongly accelerated it. The presence of these lipids during the stage of protein aggregation uniquely altered the morphology and secondary structure of the TTR fibrils, which changed the toxicity of these protein aggregates. These results suggest that interactions of TTR with red blood cells, whose membranes are rich with these lipids, can trigger irreversible aggregation of TTR and cause transthyretin amyloidosis.

Nanoscale Confinement of Dip‐Pen Nanolithography Written Phospholipid Structures on CuZr Nanoglasses

AbstractNanoglasses have attracted considerable interest among material scientists due to their novel and surprising properties. However, there is still a significant gap in understanding how nanoglasses interact with biomaterials and their effects on living cells. Previous cell studies have reported indications of possible proliferation effects, but a comprehensive understanding of differentiating nanoglass influences from distinct material or topography effects is yet to be established. In this study, the interaction between nanoglass surfaces and phospholipids, which are fundamental components of cell membranes, is investigated. The findings reveal a unique stabilizing effect exhibited by nanoglasses on structures created using lipid dip‐pen nanolithography, preventing their spreading over the surface (“confinement”). This discovery suggests that nanoglasses can potentially influence the structure of cell membranes, providing a conceivable mechanism for how nanoglasses may impact cell behavior.

The effects of molecular and nanoscopic additives on phospholipid membranes

Lipid bilayers—the main matrix of cell membranes—are a paradigm of soft molecular assemblies whose properties have been evolutionarily optimized to satisfy the functional requirements of cells. For instance, lipid bilayers must be rigid enough to serve as the protective barrier between cells and their environment, yet fluid enough to enable the diffusion of proteins and molecular clusters necessary for biological functions. Inspired by their biological multifunctionality, lipid membranes have also been used as a central design element in many practical applications including artificial cells, drug nanocarriers, and biosensors. Whether biological or synthetic, lipid membranes often involve molecular or nanoscopic additives that modulate the membrane properties through various mechanisms. Hence, how lipid membranes respond to additives has justifiably drawn much attention in recent years. This review summarizes findings and observations on different classes of additives and their effects on structural, thermodynamic, elastic, and dynamical membrane properties that are central to biological function or synthetic membrane performance. The review primarily focuses on phospholipids as a major component of cell membranes and a widely used lipid type in synthetic membrane designs.

Metabolic Features of a Novel Trichoderma asperellum YNQJ1002 with Potent Antagonistic Activity against Fusarium graminearum.

Trichoderma, a well-known and extensively studied fungal genus, has gained significant attention for its remarkable antagonistic abilities against a wide range of plant pathogens. In this study, a total of 108 Trichoderma isolates were screened through in vitro dual antagonistic assays and culture filtrate inhibition against Fusarium graminearum. Of these, the YNQJ1002 displayed noteworthy inhibitory activities along with thermal stability. To validate the metabolic differences between YNQJ1002 and GZLX3001 (with strong and weak antagonism, respectively), UPLC-TOF-MS/MS mass spectrometry was employed to analyze and compare the metabolite profiles. We identified 12 significantly up-regulated metabolites in YNQJ1002, which include compounds like Trigoneoside, Torvoside, trans,trans-hepta-2,4,6-trienoic acid, and Chamazulene. These metabolites are known for their antimicrobial properties or signaling roles as components of cell membranes. Enriched KEGG analysis revealed a significant enrichment in sphingolipid metabolism and linoleic acid metabolism, as well as autophagy. The results demonstrated that YNQJ1002's abundance of antimicrobial substances, resulting from specific metabolic pathways, enhanced its superior antagonistic activity against F. graminearum. Finally, YNQJ1002 was identified using the ITS, tef1-1α, and rpb2 regions, with MIST system sequence matching confirming its classification within the species. Overall, we have obtained a novel strain, T. asperellum YNQJ1002, which is rich in metabolites and shows potential antagonistic activity against F. graminearum. This study has opened promising prospects for the development of innovative Trichoderma-derived antifungal compounds, featuring a unique mechanism against pathogens.

TMET-05. LIPOPHAGY CONTROLS CHOLESTEROL HOMEOSTASIS AND BRAIN TUMOR GROWTH

Abstract Cholesterol is an essential 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 their lipid droplets (LDs). Mechanistically, we found that SREBP-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 became quite sensitive to cholesterol deficiency with poor growth. Our study unravels a previously unrecognized SREBP-1-autophagy-LD-CE hydrolysis pathway that plays an important role in maintaining membrane cholesterol homeostasis, while providing a potential new therapeutic avenue for GBM

Receptor Plants Alleviated Allelopathic Stress from Invasive Chenopodium ambrosioides L. by Upregulating the Production and Autophagy of Their Root Border Cells.

Chenopodium ambrosioides L. is an invasive plant native to the Neotropics that has seriously threatened the ecological security of China, and allelopathy is one of the mechanisms underlying its successful invasion. Maize (Zea mays L.) and soybean (Glycine max (L.) Merr.), as the main food crops, are usually affected by C. ambrosioides in their planting areas. The purpose of this study was to investigate the ultrastructure, autophagy, and release-related gene expression of receptor plant root border cells (RBCs) after exposure to volatile oil from C. ambrosioides and its main component α-terpene, which were studied using maize and soybean as receptor plants. The volatiles inhibited root growth and promoted a brief increase in the number of RBCs. As the volatile concentration increased, the organelles in RBCs were gradually destroyed, and intracellular autophagosomes were produced and continuously increased in number. Transcriptomic analysis revealed that genes involved in the synthesis of the plasma membrane and cell wall components in receptor root cells were significantly up-regulated, particularly those related to cell wall polysaccharide synthesis. Meanwhile, polygalacturonase and pectin methylesterases (PME) exhibited up-regulated expression, and PME activity also increased. The contribution of α-terpene to this allelopathic effect of C. ambrosioides volatile oil exceeded 70%. Based on these results, receptor plant root tips may increase the synthesis of cell wall substances while degrading the intercellular layer, accelerating the generation and release of RBCs. Meanwhile, their cells survived through autophagy of RBCs, indicating the key role of RBCs in alleviating allelopathic stress from C. ambrosioides volatiles.