Plasma Membrane Research Articles

Effect of Differentially Charged Polystyrene Nanoplastics on the Performance of Biological Denitrification in Wastewater Treatment

Nanoplastics are widely distributed in the environment and can accumulate in organisms. Increasing attention has been paid to the toxic effects of nanoplastics in wastewater biological treatment processes. In this study, polystyrene nanoplastics with different charges were synthesized and used in sequencing batch activated sludge reactors for short-term nanoplastic exposure experiments. Both positively and negatively charged nanoplastics inhibited the nitrogen removal efficiency and gene expressions of nitrification and denitrification-related genes of activated sludge. The inhibiting effect on nitrification of both nanoplastics was enhanced with increasing concentration. The study further evaluated the molecular mechanisms by which differently charged nanoplastics affect denitrification efficiency using the model denitrifying bacterium Pseudomonas stutzeri （P. stutzeri）. The results showed that both positively and negatively charged nanoplastics affected the efficiency of biological denitrification by P. stutzeri, mainly including the promotion of NO3- to NO2- conversion and the significant acceleration of N2O production. Meanwhile, negatively charged nanoplastics inhibited the growth of P. stutzeri and disrupted the cell membrane of the bacterium； however, no change was observed in the expression of denitrification-related functional genes and the nanoplastics might have affected the enzymatic activities of Nir and Nos, which in turn affected the bioprocessing efficiency. This study can provide a certain reference for the evaluation of the biosafety of nanoplastics and provide a certain support for the stable operation of wastewater treatment plants.

Structural Insight on the Selectivity of Calyx[4]Arene-Based Inhibitors of Mg2+-Dependent Atp-Hydrolases.

Located in plasma membranes, ATP hydrolases are involved in several dynamic transport processes, helping to control the movement of ions across cell membranes. ATP hydrolase acts as a transport protein, converting energy from ATP hydrolysis into transport molecules against their concentration gradients. In addition to energy metabolism and active transport, ATP hydrolase is essential for maintaining cellular homeostasis and cell function. This study focused on the domain architecture model of P-type ATPases, which participate in the reaction cycles of ATP hydrolysis carried out by membrane transport systems - Na+, K+-ATPase and Ca2+, Mg2+-ATPase. Targeted modulation of Na+, K+-ATPase and Ca2+, Mg2+-ATPase by unnatural drugs is of greatest interest due to the lack of known effectors. This new discovery presents a convenient model based on our recent experimental studies of the membrane structures and myocytes of the uterine smooth muscle, the myometrium. This current study strongly supports the fact that nanosized calix[4]arenes functionalised on the upper rings of the macrocycle with biologically active phosphonic acid fragments can serve as selective and potent inhibitors of cation-transporting electroenzymes. This is how we discovered that calix[4]arene of methylenebisphosphonic acid C-97 and calix[4]arene of bis-aminophosphonic acid C-107 selectively and effectively (I0.5 <100 nM) inhibit the activity of Mg2+, ATP-dependent electrogenic Na+ K+ plasma membrane pump. As drug discovery in the field of Mg2+-ATPase inhibitors is uncharted territory, basic research holds the key to explaining and predicting the mechanism of interaction and action of different classes of compounds. In light of the presented results, new calix[4]arene compounds can be used as potent inhibitors of Mg2+, ATP-dependent electrogenic ion pumps.

GFP Farnesylation as a Suitable Strategy for Selectively Tagging Exosomes.

Exosomes are small extracellular vesicles (EVs) constituting fully biological, cell-derived nanovesicles with great potential in cell-to-cell communication and drug delivery applications. The current gold standard for EV labeling and tracking is represented by fluorescent lipophilic dyes which, however, importantly lack selectivity, due to their unconditional affinity for lipids. Herein, an alternative EV fluorescent labeling approach is in-depth evaluated, by taking advantage of green fluorescent protein (GFP) farnesylation (GFP-f), a post-translational modification to directly anchor GFP to the EV membrane. The performance of GFP-f is analyzed, in terms of selectivity and efficiency, in several typical EV experimental setups such as delivery in recipient cells, surface engineering, and cargo loading. First, the capability of GFP and GFP-f to label exosomes was compared, showing significantly higher GFP protein levels and fluorescence intensity in GFP-f- than in GFP-labeled exosomes, highlighting the advantage of directly anchoring the GFP to the EV cell membrane. Then, the GFP-f tag was further compared to Vybrant DiD lipophilic dye labeling in exosome uptake studies, by capturing EV intracellular fluorescence in a time- and concentration-dependent manner. The internalization assay revealed a particular ability of GFP-f to monitor the uptake of tagged exosomes into recipient cells, with a significant peak of intensity reached 12 h after administration by GFP-f but not Vybrant-labeled EVs. Finally, the GFP-f labeling capability was challenged in the presence of a surface modification of exosomes and after transfection for siRNA loading. Results showed that both procedures can influence GFP-f performance compared to naïve GFP-f exosomes, although fluorescence is importantly maintained in both cases. Overall, these data provide direct insight into the advantages and limitations of GFP-f as a tagging protein for selectively and accurately tracking the exosome route from isolation to uptake in recipient cells, also in the context of EV bioengineering applications.

Silencing CaPIP5K4-1 leads to decreased male fertility in Capsicum annuum L.

Phosphatidylinositol 4-phosphate 5-kinase gene CaPIP5K4-1 is highly expressed in the pepper anthers. Virus-induced gene silencing of CaPIP5K4-1 leads to reduced male fertility in pepper. The phosphatidylinositol 4-phosphate 5-kinase (PIP5K) is a pivotal enzyme in the phosphatidylinositol signaling pathway, and its crucial involvement in both plant development and stress response has been established. Here, we found that the expression of CaPIP5K4-1 in pepper was significantly higher in the fertile flower buds compared to sterile flower buds. Furthermore, its expression was validated in anthers and pollens by qRT-PCR and RNA-ISH assays, respectively. Its GFP fusion protein was mainly located on the plasma membrane. Silencing CaPIP5K4-1 in fertile pepper accessions resulted in wrinkled pollen grain cell walls, decreased pollen germination efficiency, and inhibited pollen tube growth. The transcription levels of multiple genes in the phosphatidylinositol signaling pathway were also assessed. Five phospholipase C (PLC) genes were downregulated in silenced plants. On the contrary, inositol phosphatase SAC and phosphatase and tensin homolog (PTEN) were upregulated. This study reported the role of CaPIP5K4-1 in pepper male fertility and provided insights into the regulatory mechanisms of PI signaling in pepper.

Bioinspired adaptive lipid-integrated bilayer coating for enhancing dynamic water retention in hydrogel-based flexible sensors

While hydrogel-based flexible sensors find extensive applications in fields such as medicine and robotics, their performance can be hindered by the rapid evaporation of water, leading to diminished sensitivity and mechanical durability. Despite the exploration of some effective solutions, such as introducing organic solvents, electrolytes, and elastomer composites, these approaches still suffer from problems including diminished conductivity, interface misalignment, and insufficient protection under dynamic conditions. Inspired by cell membrane structures, we developed an adaptive lipid-integrated bilayer coating (ALIBC) to enhance water retention in hydrogel-based sensors. Lipid layers and long-chain amphiphilic molecules are used as compact coating and anchoring agents on the hydrogel surface, mimicking the roles of lipids and membrane proteins in cell membranes, while spare lipids from aggregates within hydrogels can migrate to the surface to combat dehydration under deformation. This lipid-integrated bilayer coating prevents the water evaporation of hydrogels at both static and dynamic states without affecting the inherent flexibility, conductivity, and no cytotoxicity. Hydrogel-based sensors with ALIBC exhibited significantly enhanced performance in conditions of body temperature, extensive deformation, and long-term dynamic sensing. This work presents a general approach for precisely controlling the water-retaining capacity of hydrogels and hydrogel-based sensors without compromising their intrinsic physical properties.

Aflatoxin B1 Promotes Pyroptosis in IPEC-J2 Cells by Disrupting Mitochondrial Dynamics through the AMPK/NLRP3 Pathway.

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins in food and feed, seriously jeopardizing the intestinal health, while the effects of AFB1 on intestinal damage remain to be well understood. This study aims to evaluate the effect of AFB1 on intestinal injury by regulating AMP-activated protein kinase (AMPK)-mediated pyroptosis in vitro. The present study showed that AFB1 led to the formation of large number of bubble-like protrusions on the cell membrane, releasing lactate dehydrogenase (LDH) and interleukin-1β (IL-1β). Stimulation with AFB1 resulted in the activation of the NOD-like receptor protein 3 (NLRP3) pathway, as indicated by the increased expression of pyroptosis-associated factor mRNAs and proteins, which ultimately led to a significant upregulation of the pyroptosis rate. Meanwhile, AFB1 caused dysfunction of mitochondrial dynamics by activating the AMPK signaling pathway as mainly evidenced by upregulating dynamin-1-like protein 1 (Drp1) mRNA and protein expression. Moreover, inhibition of NLRP3 and AMPK pathways by MCC950 and compound C, respectively, significantly alleviated AFB1-induced damage in IPEC-J2 cells, evidenced by suppressed NLRP3-mediated pyroptosis, and ameliorated AMPK-mediated mitochondrial dynamics imbalance. In conclusion, these results demonstrated that AFB1 promoted pyroptosis of IPEC-J2 cells by interfering with mitochondrial dynamics by activating the AMPK/NRLP3 pathway.

Biomimetic Metallacage Nanoparticles with Aggregation-Induced Emission for NIR-II Fluorescence Imaging-Guided Synergistic Immuno-Phototherapy of Tumors.

The integration of theranostics, which combines diagnostics with therapeutics, has markedly improved the early detection of diseases, precise medication management, and assessment of treatment outcomes. In the realm of oncology, organoplatinum-based supramolecular coordination complexes (SCCs) that can coload therapeutic agents and imaging molecules have emerged as promising candidates for multimodal theranostics of tumors. To address the challenges of tumor-targeted delivery and multimodal theranostics for SCCs, this study employs a cell membrane cloaking strategy to fabricate biomimetic metallacage nanoparticles (MCNPs) with multimodal imaging capabilities and homologous targeting capabilities. Specifically, a photosensitizer molecule (BTTP) containing AIE-active groups was assembled into a metallacage of C-BTTP through Pt-N coordination. This process endows the metallacage with strong NIR-II fluorescence in the aggregated state and significantly superior ROS generation compared to that of the precursor ligand. After being encapsulated with F127, the MCNPs were further cloaked with U87 cancer cell membranes, creating biomimetic MCNPs that achieve tumor-targeting capabilities. Verified by in vitro and in vivo experiments, MCNPs enable multimodal imaging and initiate immunotherapy under photothermal and photodynamic stimulation, leading to synergistic antitumor effects. Furthermore, the evaluation of immunogenic cell death and dendritic cell maturation rate in U87 tumor-bearing mice confirmed the mechanism of photothermal and photodynamic synergistic immunotherapy. This study provides an innovative strategy for enhancing the tumor-targeting and therapeutic efficiency of SCCs, offering a versatile strategy for efficient and minimally invasive theranostics of tumors. The development of such biomimetic nanoparticles represents a significant advancement in the field of nanomedicine, potentially transforming cancer treatment through personalized and targeted therapies.

Molecular Engineering of Ultrabright Biomimetic NanoGhost for Site-Selective Tumor Imaging and Biodistribution.

Optically active ultrabright imaging agents are shown to delineate tumor location with deep tissue visualization in pre noclinical tumor models. NanoGhosts (NGs) particles are reconstructed from the cell membrane and integrated with organic fluorophores to attain ultra-brightness for solid tumor imaging. Moreover, the integration of amphiphilic and lipophilic molecules reveals structural characteristics of NGs (≈70nm), which also alter their brightness. Upon intravenous administration (10 mgkg-1 single dose), these ultrabright NGs (778 MESF) enable the high-resolution of tumor site and real-time tracking of vital organs with high-contrast fluorescence signals. Engineered biomimetic NGs demonstrates better resolution and tissue penetration as compared to the clinically approved indocyanine green (ICG). High precision in tumor detection (0.5h) and strong tumor retention (24h which is further up to 30th day) without affecting healthy tissues ensure the future scope of NGs in early-stage cancer imaging. These findings suggest that these NGs mimic the biological characteristics of native cells, enabling them to evade immune clearance and target the solid tumor naturally.

Pyroptotic cell corpses are crowned with F-actin-rich filopodia that engage CLEC9A signaling in incoming dendritic cells.

While apoptosis dismantles the cell to enforce immunological silence, pyroptotic cell death provokes inflammation. Little is known of the structural architecture of cells undergoing pyroptosis, and whether pyroptotic corpses are immunogenic. Here we report that inflammasomes trigger the Gasdermin-D- and calcium-dependent eruption of filopodia from the plasma membrane minutes before pyroptotic cell rupture, to crown the resultant corpse with filopodia. As a rich store of F-actin, pyroptotic filopodia are recognized by dendritic cells through the F-actin receptor, CLEC9A (DNGR1). We propose that cells assemble filopodia before cell rupture to serve as a posthumous mark for a cell that has died by gasdermin-induced pyroptosis, or MLKL-induced necroptosis, for recognition by dendritic cells. This study reveals the spectacular morphology of pyroptosis and identifies a mechanism by which inflammasomes induce pyroptotic cells to construct a de novo alarmin that activates dendritic cells via CLEC9A, which coordinates the transition from innate to adaptive immunity1,2.

A viral protein activates the MAPK pathway to promote viral infection by downregulating callose deposition in plants

Mitogen-activated protein kinase (MAPK) cascades are evolutionarily conserved in both plants and animals and play critical roles in activating innate immunity to defend against various pathogens. However, the role of MAPK cascades in positively regulating or enhancing viral infections in plants is unclear. In this study, we investigate the involvement of MAPK cascades in infection by the positive-strand RNA virus tomato chlorosis virus (ToCV). Our findings reveal that ToCV infection activates MAPK cascades, promoting virus spread within plants. Specifically, ToCV P7, a pathogenicity determinant protein, localizes to the plasma membrane and recruits NbMPK3/6 from the nucleus. Subsequently, P7 is directly phosphorylated on serine 59 by NbMPK3/6. Phosphorylated P7 interacts with NbREM1.1 and inhibits its ability to induce callose deposition at plasmodesmata. These results demonstrate that NbMPK3/6 directly phosphorylate ToCV P7, modulating antiviral defence mechanisms by downregulating callose deposition at plasmodesmata and thereby enhancing ToCV transmission in N. benthamiana. This study sheds light on the intricate arms race between host defence and viral counter-defence strategies.

Design, synthesis, X-ray crystal structure, and antifungal evaluation of new acetohydrazide derivatives containing a 4-thioquinazoline moiety.

To find efficient agricultural fungicides, 29 new 4-thioquinazoline-containing acetohydrazide derivatives were prepared and tested for their fungicidal properties. All of the target compounds were characterized by 1H and 13C nuclear magnetic resonance and high-resolution mass spectrometry techniques, and the molecular structure of compound A2 was verified by single-crystal X-ray diffraction measurement. The experimental results revealed that many compounds from this series had impressive inhibition efficacies in vitro against the tested fungi. For example, compound A25 was identified as the best fungicidal agent against Rhizoctonia solani with an EC50 (half-maximal effective concentration) value of 0.66 μg mL-1, superior to those of the commercial fungicides chlorothalonil, carbendazim and boscalid. Additionally, this compound displayed favorable protection and curative activities in vivo against rice sheath blight caused by R. solani. Antifungal mechanistic studies on compound A25 indicated that this compound exerted its strong anti-R. solani effects probably through an effective inhibition of fungal succinate dehydrogenase activity [half-maximal inhibitory concentration (IC50) = 4.88 μm] and the impairment of cell membrane integrity, based on the results from enzymatic bioassays, molecular docking studies, and scanning and transmission electron microscopy observations. Acetohydrazide derivatives containing the 4-thioquinazoline moiety had the potential to be employed as lead compounds for developing more efficient agricultural fungicides in the near future. © 2024 Society of Chemical Industry.

Complications of delayed diagnosis and challenges: successfully managed SPTB gene variant hereditary spherocytosis with hepatocellular jaundice—a case report

BackgroundHereditary spherocytosis is a rare genetic disorder of the red blood cell membrane that is characterized by anemia, jaundice, and splenomegaly; however, in the absence of family history and with unusual clinical presentation, the diagnosis might not be made until later in life.Case presentationHere, we present a challenging case of genetically proven hereditary spherocytosis that involves the SPTB gene in a 23-year-old female patient from Ethiopia who had repeated medical visits for episodic jaundice and hepatosplenomegaly, with unusual features of conjugated hyperbilirubinemia, pancytopenia, normal reticulocyte count, and lack of family history, where the delay in diagnosis led to several complications. The patient was successfully managed with simultaneous splenectomy and cholecystectomy.ConclusionThis case underscores the importance of a thorough clinical examination, spending the time to review a case periodically without assuming the initial diagnosis is correct, and maintaining a healthy skepticism of inconsistent data to prevent misdiagnosis and mistreatment. The diagnostic delay highlights the need for increased awareness and familiarity with diagnostic modalities of hereditary spherocytosis among healthcare providers in Ethiopia.

Targeting Caveolin-1 in Multiple Myeloma Cells Enhances Chemotherapy and Natural Killer Cell-Mediated Immunotherapy.

The cell membrane transport capacity and surface targets of multiple myeloma (MM) cells heavily influence chemotherapy and immunotherapy. Here, it is found that caveolin-1 (CAV1), a primary component of membrane lipid rafts and caveolae, is highly expressed in MM cells and is associated with MM progression and drug resistance. CAV1 knockdown decreases MM cell adhesion to stromal cells and attenuates cell adhesion-mediated drug resistance to bortezomib. CAV1 inhibition in MM cells enhances natural killer cell-mediated cytotoxicity through increasing CXCL10, SLAMF7, and CD112. CAV1 suppression reduces mitochondrial membrane potential, increases reactive oxygen species, and inhibits autophagosome-lysosome fusion, resulting in the disruption of redox homeostasis. Additionally, CAV1 knockdown enhances glutamine addiction by increasing ASCT2 and LAT1 and dysregulates glutathione metabolism. As a result of CAV1 inhibition, MM cells are more sensitive to starvation, glutamine depletion, and glutamine transporter inhibition, and grow more slowly in vivo in a mouse model treated with bortezomib. The observation that CAV1 inhibition modulated by 6-mercaptopurine, daidzin, and statins enhances the efficacy of bortezomib in vitro and in vivo highlights the translational significance of these FDA-approved drugs in improving MM outcomes. These data demonstrate that CAV1 serves as a potent therapeutic target for enhancing chemotherapy and immunotherapy for MM.

Targeting cholangiocarcinoma cells by cold piezoelectric plasmas: in vitro efficacy and cellular mechanisms

Cold piezoelectric plasma (CPP) is a novel approach in cancer therapy, enabling the development of portable treatment devices capable of triggering cancer cell death. While its effectiveness remains underexplored, this research focuses on its application against cholangiocarcinoma (CCA), an aggressive cancer of the biliary tract. A CPP device is utilized to generate either a corona discharge (Pz-CD) or a dielectric barrier discharge (Pz-DBD) for in vitro experiments. Notably, Pz-CD can deliver more power than Pz-DBD, although both sources produce significant levels of reactive species in plasma and liquid phases. This work shows that CPP causes a gradient increase in medium temperature from the center towards the edges of the culture well, especially for longer treatment times. Although Pz-CD heats more significantly, it cools quickly after plasma extinction. When applied to human CCA cells, CPP shows immediate and long-term effects, more localized for Pz-CD, while more uniform for Pz-DBD. Immediate effects result also in actin cytoskeleton remodeling without alteration of the cell membrane permeability. Long-term effects of CPP, although the antioxidant system is engaged, include activation of the DNA damage response pathway leading to cell death. In conclusion, CPP should be recognized as a promising antitumor therapy.

Sn-Position-Resolved Quantification of Aminophospholipids by Isotopic N,N-Dimethyl Leucine Labeling and High-Resolution Ion Mobility Mass Spectrometry.

Aminophospholipids (APLs), composed of phosphatidylethanolamines (PEs) and phosphatidylserines (PSs), are vital components of mammalian cell membranes and lipoproteins, participating in both homeostasis and cellular signaling. Their structural changes, including the permutation of fatty acid connectivity (sn-positions), due to dysfunctional metabolic processes have been linked to many diseases. However, the accurate quantification of APLs with unambiguous fatty acyl assignment through routine label-free LC-MS/MS lipidomic analysis remains a major challenge. In this study, we explore the functionalization of the free primary amine groups of APLs using amine-reactive isotopic N,N-dimethyl leucine (iDiLeu) and employ high-resolution ion mobility MS (IM-MS) to develop a novel method for sensitive discernment and accurate quantification of APL sn-isomers. With high-resolution demultiplexing (HRdm) providing IM resolving power >200, labeled sn-isomeric pairs of APLs (ΔCCS ≈ 1%) demonstrate excellent, near baseline separation. In addition to greatly enhanced sensitivity, 5-plex iDiLeu labeling enables the construction of an internal 4-point calibration curve and therefore absolute quantification of APL sn-isomers in a single run. This strategy enabled precise annotation and quantification of 239 APLs including 60 pairs of sn-isomers in the mouse cortex. Additionally, we were able to find ratio changes in multiple APL sn-isomer pairs between wild type and APP/PS1 Alzheimer's disease (AD) model mice at different ages, indicating their strong correlation to AD progression. This strategy could provide universal utility in unraveling the alteration of APL sn-isomers, which have long been considered as the "dark matter" of traditional lipidomic analyses, leading to more precise elucidation of molecular mechanisms of various diseases.

ROS Responsive Cerium Oxide Biomimetic Nanoparticles Alleviates Calcium Oxalate Crystals Induced Kidney Injury via Suppressing Oxidative Stress and M1 Macrophage Polarization.

Emerging studies have demonstrated that M1 macrophage polarization and oxidative stress play important roles in calcium oxalate (CaOx) induced kidney injury, which leads to increased crystals deposition. ROS scavenging nanozymes and kidney-targeted nanoparticles for antioxidant drugs delivery have emerged as an arisen methodology for kidney injury therapy. However, cell membrane biomimetic-modified nanozymes as anti-inflammatory drug delivery systems for the treatment of kidney injury is rarely reported. Herein, the ROS responsive red blood cell-membrane-coated resatorvid-loaded cerium oxide nanoparticles (RBCM@CeO2/TAK-242) are constructed to suppress CaOx induced kidney injury and crystals deposition. In vitro, RBCM@CeO2/TAK-242 shows effective internalization by renal tubular epithelial cells, along with demonstrated antioxidative, anti-inflammatory, and macrophage reprogramming effects. Glyoxalate(Gly)-induced renal CaOx crystals mouse model is established, RBCM@CeO2/TAK-242 shows excellent injured kidney targeting and biosafety, and could effectively suppress CaOx induced kidney injury and crystals deposition. RBCM@CeO2/TAK-242 has a dual protective effect by both inhibiting oxidative stress and modulating macrophage polarization in vivo. In addition, RNA seq analysis reveals that RBCM@CeO2/TAK-242 protects against CaOx induced kidney injury via suppressing the TLR4/NF-κB pathway. This study provides an innovative strategy for RBCM@CeO2/TAK-242 as injured kidney targeting and dual protective effects for the treatment of CaOx induced kidney injury and crystals deposition.

A Smart Nanomedicine Unleashes a Dual Assault of Glucose Starvation and Cuproptosis to Supercharge αPD-L1 Therapy.

Combination therapy has become a promising strategy for promoting the outcomes of anti-programmed death ligand-1 (αPD-L1) therapy in lung cancer. Among all, emerging strategies targeting cancer metabolism have shown great potency in treating cancers with immunotherapy. Here, alteration in glucose and copper metabolisms is found to synergistically regulate PD-L1 expression in lung cancer cells. Thus, an intelligent biomimetic nano-delivery system is synthesized by camouflaging lung cancer cell membranes onto glucose oxidase-loaded Cu-LDHs (CMGCL) for cancer metabolism targeted interference. Such novel nanomedicine is able to induce lung cancer cell cuproptosis and PD-L1 upregulation significantly via self-amplified cascade reactions. Meanwhile, with a decent cancer cell membrane coating, CMGCL exhibited great biosafety, tumor-targeted efficiency and anti-tumor effects in LLC lung tumor-bearing mice models. Additionally, a combination of CMGCL can sensitize the therapeutic effects of αPD-L1, substantially promoting tumor inhibition in both subcutaneous and lung metastasis LLC-bearing mice models. Overall, these findings highlight the potential connections between glucose metabolism and cell cuproptosis, offering a promising approach for treating lung cancer by integrating starvation, cuproptosis, and immunotherapy.

Lipid Membrane Domains Control Actin Network Viscoelasticity.

The mammalian cell membrane is embedded with biomolecular condensates of protein and lipid clusters, which interact with an underlying viscoelastic cytoskeleton network to organize the cell surface and mechanically interact with the extracellular environment. However, the mechanical and thermodynamic interplay between the viscoelastic network and liquid-liquid phase separation of 2-dimensional (2D) lipid condensates remains poorly understood. Here, we engineer materials composed of 2D lipid membrane condensates embedded within a thin viscoelastic actin network. The network generates localized anisotropic stresses that deform lipid condensates into triangular morphologies with sharp edges and corners, shapes unseen in many 3D composite gels. Kinetic coarsening of phase-separating lipid condensates accelerates the viscoelastic relaxation of the network, leading to an effectively softer composite material over intermediate time scales. We dynamically manipulate the membrane composition to control the elastic-to-viscous crossover of the network. Such viscoelastic composite membranes may enable the development of coatings, catalytic surfaces, separation membranes, and other interfaces with tunable spatial organization and plasticity mechanisms.

Dietary fructose enhances tumour growth indirectly via interorgan lipid transfer.

Fructose consumption has increased considerably over the past five decades, largely due to the widespread use of high-fructose corn syrup as a sweetener1. It has been proposed that fructose promotes the growth of some tumoursdirectly by serving as a fuel2,3. Here we show that fructose supplementation enhances tumour growth in animal models of melanoma, breast cancer and cervical cancer without causing weight gain or insulin resistance. The cancer cells themselves were unable to use fructose readily as a nutrient because they did not express ketohexokinase-C (KHK-C). Primary hepatocytes did express KHK-C, resulting in fructolysis and the excretion of a variety of lipid species, including lysophosphatidylcholines (LPCs). In co-culture experiments, hepatocyte-derived LPCs were consumed by cancer cells and used to generate phosphatidylcholines, the major phospholipid of cell membranes. In vivo, supplementation with high-fructose corn syrup increased several LPC species by more than sevenfold in the serum. Administration of LPCs to mice was sufficient to increase tumour growth. Pharmacological inhibition of ketohexokinase had no direct effect on cancer cells, but it decreased circulating LPC levels and prevented fructose-mediated tumour growth in vivo. These findings reveal that fructose supplementation increases circulating nutrients such as LPCs, which can enhance tumour growth through a cell non-autonomous mechanism.

Fast-diffusing receptor collisions with slow-diffusing peptide ligand assemble the ternary parathyroid hormone–GPCR–arrestin complex

The assembly of a peptide ligand, its receptor, and β-arrestin (βarr) into a ternary complex within the cell membrane is a crucial aspect of G protein-coupled receptor (GPCR) signaling. We explore this assembly by attaching fluorescent moieties to the parathyroid hormone (PTH) type 1 receptor (PTH1R), using PTH as a prototypical peptide hormone, along with βarr and clathrin, and recording dual-color single-molecule imaging at the plasma membrane of live cells. Here we show that PTH1R exhibits a near-Brownian diffusion, whereas unbound hormone displays limited mobility and slow lateral diffusion at the cell surface. The formation of the PTH–PTH1R–βarr complex occurs in three sequential steps: (1) receptor and ligand collisions, (2) phosphoinositide (PIP3)-dependent recruitment and conformational change of βarr molecules at the plasma membrane, and (3) collision of most βarr molecules with the ligand-bound receptor within clathrin clusters. Our results elucidate the non-random pathway by which PTH–PTH1R–βarr complex is formed and unveil the critical role of PIP3 in regulating GPCR signaling.