Phospholipid Molecules Research Articles

Can fragment ion intensity be used for fatty acid sn-position determination of food phospholipids?

Fatty acid (FA) regio-position is critical information for the structures of both triglycerides and phospholipids in food products. Although lipase/phospholipase hydrolysis combined with TLC separation and GC analysis can be used to determine the overall sn-2 FA composition of triglycerides/phospholipids in food samples, it is much more challenging to pinpoint FA regio-position at the molecular species level. Currently, the most widely used method to obtain such information is based on the relative intensity of fragment ions generated in tandem mass spectrometry. The reliability of this approach was verified in this study using regio-pure phospholipid standards and by cross-validation with the Paternò–Büchi photochemical reaction. We have demonstrated that for food materials with widespread regioisomers, a standard calibration curve from regio-pure standards is needed to determine the proportion of each isomer, whereas fragment ion intensity can only be used to reveal the sn-position of FA in phospholipid molecules devoid of regioisomers.

Exploring the potential of biosurfactants produced by fungi found in soil contaminated with petrochemical wastes

Biosurfactants are a diverse group of compounds derived from microorganisms, possessing various structures and applications. The current study was seeking to isolate and identify a new biosurfactant-producing fungus from soil contaminated with petrochemical waste. The bioprocess conditions were optimized to maximize biosurfactant production for Aspergillus carneus OQ152507 using a glucose peptone culture medium with a pH of 7.0 and a temperature of 35 °C. The carbon source was glucose (3%), and ammonium sulfate (0.25%) was utilized as the nitrogen source. For Aspergillus niger OQ195934, the optimized conditions involved a starch nitrate culture medium with a pH of 7.0 and a temperature of 30 °C. The carbon source used was sucrose (3.5%), and ammonium sulfate (0.25%) served as the nitrogen source. The phenol-H2SO4 and phosphate tests showed that the biosurfactants that were extracted did contain glycolipid and/or phospholipid molecules. They showed considerable antimicrobial activity against certain microbes. The obtained biosurfactants increased the solubility of tested polyaromatic hydrocarbons, including fluoranthene, pyrene, anthracene, and fluorine, and successfully removed the lubricating oil from contaminated soil and aqueous media surface tension reduction. Based on the obtained results, A. carneus and A. niger biosurfactants could be potential candidates for environmental oil remediation processes.

Applications of radionuclide-carrying liposomes for diagnosis and treatment of cancer

Using nanocapsules to deliver diagnostic and therapeutic agents to targeted biological sites enhances the safety and effectiveness of healthcare by decreasing toxicity and increasing the accumulation of medicinal agents at targeted sites. Liposomes, nanocapsules made of naturally occurring lipids, boast many advantages for the delivery of therapeutic agents. This article reviews both the advantages and challenges associated with liposomal drug delivery for the treatment of cancerous tumors and infectious diseases. These minute spherical sacs of phospholipid molecules are flexible carriers that can be modified in various ways to optimize their use. Examples of this include alteration of the size of liposomes to selectively accumulate in tumor microenvironments and “PEGylation” of their surface to reduce uptake of liposomes by the mononuclear phagocytic system (MPS). While one of the main challenges of liposomal drug delivery is the heightened uptake of liposomes by the MPS, this unique property can be used to target diseased areas with a significant MPS presence. Furthermore, the liposomal structure can be manipulated to allow for the triggered release of internal contents with externally controlled factors. Liposomes carrying therapeutic radionuclides can be injected directly into solid tumors and dispersed throughout the tumor by convection-enhanced delivery. The flexibility and pliability of liposomes allow them to move through tight spaces within a tumor with much greater dispersion and penetration when compared to more rigid nanoparticles. Due to the benefits of radionuclide-carrying liposomes in disease diagnosis and delivery of chemotherapeutic agents, their utilization is expected to be expanded.

Light-Responsive Smart Nanoliposomes: Harnessing the Azobenzene Moiety for Controlled Drug Release under Near-Infrared Irradiation.

The azobenzene moiety is an intriguing structure that deforms under UV and visible light, indicating a high potential for biomedical applications. However, its reaction to UV radiation is problematic because of its high energy and low tissue penetration. Unlike previous research on azobenzene structures in photoresponsive materials, this study presents a novel method for imparting photostimulation-responsive properties to liposomes by incorporating the azobenzene moiety and extending the light wavelength with up-conversion nanoparticles. First, the azobenzene structure was incorporated into a phospholipid molecule to create Azo-PSG, which could spontaneously form vesicle assemblies in aqueous solutions and isomerizes within 1 h of light exposure. Furthermore, orthogonal up-conversion nanoparticles with a core-shell structure were created by sequentially growing lanthanide rare earths in the shell layer, which efficiently converts near-infrared light into ultraviolet (400 nm) and blue-green (540 nm) light. Combining these core-shell structured up-conversion nanomaterials with Azo-PSG molecules resulted in the creation of a near-infrared light-responsive smart nanoliposome system. Under near-infrared light irradiation, UCNPs emit UV and blue-green light, causing conformational changes in Azo-PSG molecules that allow drug release within 6 h. The reversible structural shift of Azo-PSG in response to light stimulation holds enormous promise for improving drug release techniques. This novel technique also expands the usage of UV-responsive compounds beyond their constraints of low penetration and high biotoxicity, allowing for rapid medication release under NIR light.

A GDSL motif-containing lipase modulates Sclerotinia sclerotiorum resistance in Brassica napus.

Sclerotinia stem rot (SSR) caused by Sclerotinia sclerotiorum (Lib.) De Bary is a devastating disease infecting hundreds of plant species. It also restricts the yield, quality, and safe production of rapeseed (Brassica napus) worldwide. However, the lack of resistance sources and genes to S. sclerotiorum has greatly restricted rapeseed SSR-resistance breeding. In this study, a previously identified GDSL motif-containing lipase gene, Brassica napus GDSL LIPASE-LIKE 1 (BnaC07.GLIP1), encoding a protein localized to the intercellular space, was characterized as functioning in plant immunity to S. sclerotiorum. The BnaC07.GLIP1 promoter is S. sclerotiorum-inducible and the expression of BnaC07.GLIP1 is substantially enhanced after S. sclerotiorum infection. Arabidopsis (Arabidopsis thaliana) heterologously expressing and rapeseed lines overexpressing BnaC07.GLIP1 showed enhanced resistance to S. sclerotiorum, whereas RNAi suppression and CRISPR/Cas9 knockout B. napus lines were hyper-susceptible to S. sclerotiorum. Moreover, BnaC07.GLIP1 affected the lipid composition and induced the production of phospholipid molecules, such as phosphatidylethanolamine, phosphatidylcholine and phosphatidic acid, which were correlated with decreased levels of reactive oxygen species (ROS) and enhanced expression of defense-related genes. A B. napus bZIP44 transcription factor specifically binds the CGTCA motif of the BnaC07.GLIP1 promoter to positively regulate its expression. BnbZIP44 responded to S. sclerotiorum infection, and its heterologous expression inhibited ROS accumulation, thereby enhancing S. sclerotiorum resistance in Arabidopsis. Thus, BnaC07.GLIP1 functions downstream of BnbZIP44 and is involved in S. sclerotiorum resistance by modulating the production of phospholipid molecules and ROS homeostasis in B. napus, providing insights into the potential roles and functional mechanisms of BnaC07.GLIP1 in plant immunity and for improving rapeseed SSR disease-resistance breeding.

Cryo-EM structures of a mycobacterial ABC transporter that mediates rifampicin resistance

Drug-resistant Tuberculosis (TB) is a global public health problem. Resistance to rifampicin, the most effective drug for TB treatment, is a major growing concern. The etiological agent, Mycobacterium tuberculosis (Mtb), has a cluster of ATP-binding cassette (ABC) transporters which are responsible for drug resistance through active export. Here, we describe studies characterizing Mtb Rv1217c-1218c as an ABC transporter that can mediate mycobacterial resistance to rifampicin and have determined the cryo-electron microscopy structures of Rv1217c-1218c. The structures show Rv1217c-1218c has a type V exporter fold. In the absence of ATP, Rv1217c-1218c forms a periplasmic gate by two juxtaposed-membrane helices from each transmembrane domain (TMD), while the nucleotide-binding domains (NBDs) form a partially closed dimer which is held together by four salt-bridges. Adenylyl-imidodiphosphate (AMPPNP) binding induces a structural change where the NBDs become further closed to each other, which downstream translates to a closed conformation for the TMDs. AMPPNP binding results in the collapse of the outer leaflet cavity and the opening of the periplasmic gate, which was proposed to play a role in substrate export. The rifampicin-bound structure shows a hydrophobic and periplasm-facing cavity is involved in rifampicin binding. Phospholipid molecules are observed in all determined structures and form an integral part of the Rv1217c-1218c transporter system. Our results provide a structural basis for a mycobacterial ABC exporter that mediates rifampicin resistance, which can lead to different insights into combating rifampicin resistance.

Mechanisms and Factors Influencing the Production of Uniform-Sized Giant Unilamellar Vesicles by Discrete Lipid Film Arrays.

In this paper, we innovatively proposed a highly uniform vesicle preparation scheme based on the intervesicle mechanical self-constraint effect of vesicle crowding. By adjusting the spacing of discrete microwell structures, we observed that during the self-assembly of phospholipid molecules in microwells to form giant unilamellar vesicles (GUVs), the scale swelling of the vesicles during the continuous growth process would lead to the crowding of vesicles in adjacent microwells, thus inducing the formation of intervesicle mechanical self-constraint effect. The results of the experiment showed that this paper obtained the optimized discretized microwell structure (micropillar side: 30 μm; pitch: 0 μm), and the corresponding lipid mass was measured and determined, yielding homogeneous giant GUVs of 37.9 ± 2.0 μm. In this paper, homogenized GUVs (∼40 μm) with different cholesterol concentrations (10, 20, and 30%) were obtained by this method, and the above vesicles were subjected to controlled electroporation experiment under external electric fields of 23, 31, and 41 kV/cm, respectively. It showed that the mechanical self-constraint effect of vesicle crowding induced by patterned microstructures during the self-assembly of phospholipid molecules significantly enhances the size homogeneity of GUVs, which would be helpful for the wide applications of GUVs in other areas such as cell-like models and controlled release of drugs.

Role of Enzymes Capable of Transporting Phosphatidylserine in Brain Development and Brain Diseases.

Phosphatidylserine (PS) is a common type of phospholipid, typically located in the inner leaflet of the cell membrane, especially abundant in the nervous system. It is an important component of the neuronal membrane and is considered to play a regulatory role in various brain functions, including memory and emotional stability, because its exposure to the outer leaflet of the neuronal membrane can result in abnormalities in various neurobiological processes such as synaptic transmission and neuronal apoptosis. Recently, research on two types of membrane proteins that synergistically mediate the transmembrane transport of phospholipid molecules in eukaryotic cells has become more in-depth and detailed. This review mainly explores the regulation of the expression of phosphatidylserine transporters and their impact on brain development and diseases.

Phytosomes: An Emerging Drug Delivery System

A smart transport procedure known as "Phytosome advancement" has been created to concede phospholipid and water-dissolvable phytoconstituent the capacity to cooperate synergistically. The phospholipid molecule, made out of two fat-dissolvable tails and a water-solvent head, assumes a pivotal part in this cycle. Going about as an emulsifying subject matter expert, it uses its double dissolvability qualities to work with the mix with natural concentrates. The consequence of this blend is the upgrade of the bioavailability of lipid-dissolvable drugs, empowering quicker and more successful assimilation. The meaning of this article lies in its compact outline of both a unique drug conveyance framework and vesicular prescription conveyance frameworks. It plans to give a complete comprehension of different perspectives, including the presentation and clarification of Phytosome, the advantages and detriments related with this conveyance methodology, significant properties to consider, strategies for planning, portrayal procedures, and the wide cluster of uses it offers in the field of medication. It is trusted that this extended substance will help perusers in procuring a more profound comprehension of Phytosome development and its likely ramifications in further developing medication conveyance proficiency.

Hyaluronic Acid-Coated Nanoliposomes as Delivery Systems for Fisetin: Stability, Membrane Fluidity, and Bioavailability.

Fisetin has shown numerous health benefits, whereas its food application is constrained by water insolubility, poor stability, and low bioaccessibility. This work investigated the potential of hyaluronic acid (HA)-coated nanoliposomes for the encapsulation and delivery of fisetin. It was observed that HA can adsorb onto the liposomal membrane through hydrogen bonding and maintain the spherical shape of nanoliposomes. Fluorescence analysis suggested that the HA coating restricted the motion and freedom of phospholipid molecules in the headgroup region and reduced the interior micropolarity of the nanoliposomes but did not affect the fluidity of the hydrophobic core. These effects were more pronounced for the HA with a low molecular weight (35 kDa) and moderate concentration (0.4%). The HA coating improved the storage and thermal stability of the nanoliposomes, as well as the digestive stability and bioaccessibility of the encapsulated fisetin. These findings could guide the development of HA-coated nanoliposomes for the controlled delivery of hydrophobic bioactives such as fisetin in functional foods.

Long-term impacts of egg quiescence and Wolbachia infection on lipid profiles in Aedes aegypti: Ovarian roles in lipid synthesis during reproduction

Wolbachia, an endosymbiotic bacterium, relies on nutrients from its host to complete its life cycle. The presence of Wolbachia strain wAlbB in the mosquito Aedes aegypti during egg or larval stages affects the host’s development, leading to the absence of developed and visible ovaries in adult mosquito females. In this study, we investigated the impacts of egg quiescence and Wolbachia infection on lipid profiles of adult Ae. aegypti females, and discerned the role of ovaries in lipid synthesis in the reproductive process. The lipidomes of Wolbachia infected and uninfected female individuals at various developmental stages were quantitatively analyzed by LC-MS/MS. Lipidomic change patterns were systematically further investigated in wAlbB-infected fertile females and infertile females following blood feeding. Prolonged egg quiescence induced a shortage of acyl-carnitine (CAR) and potentially impacted some molecules of diacyl-phospholipid (diacyl-PL) and sphingolipid (SL) in young adult mosquitoes. After the first gonotrophic cycle, infertile females accumulated more CAR and lyso-phospholipid (lyso-PL) than fertile females. Then in the second gonotrophic cycle, the patterns of different lipid groups remained similar between fertile and infertile females. Only a small proportion of molecules of triglyceride (TG), phospholipid (lyso-PL and diacyl-PL) and ceramide (Cer) increased exclusively in fertile females from 0 h to 16 h post blood meal, suggesting that the generation or prescence of these lipids rely on ovaries. In addition, we found cardiolipins (CL) might be impacted by Wolbachia infection at the egg stage, and infected mosquitoes also showed distinct patterns between fertile and infertile females at their second gonotrophic cycle. Our study provides new insights into the long-term influence of Wolbachia on lipid profiles throughout various life stages of mosquitoes. Additionally, it suggests a role played by ovaries in lipid synthesis during mosquito reproduction.

Phytosomes Nanocarrier with Insight Towards the Future in Cancer Therapy: A Mini-Review.

Cancer is classified as having one of the highest mortality rates on a global scale, presenting a significant challenge in its treatment, especially when conventional chemotherapy methodologies are used. Conversely, there is a growing interest in utilizing herbal medicine as an alternative to the treatment of cancer because of its lack of adverse effects compared to contemporary medical strategies. The incorporation of nanotechnology into therapy has attracted attention owing to its efficacy in the treatment of various illnesses. Phytosomes play a crucial role in the treatment of cancer by enhancing the characteristics of drugs and nanostructures within carriers to enable targeted drug delivery. The establishment of chemical bonds between phospholipid molecules and bioactive compounds from plants ensures the stability of phytosomes, thus establishing them as an innovative mechanism for drug delivery systems that transport plant-derived constituents to specific areas. This mini-overview discusses the potential phytosome complexes, uses, drawbacks, patents, challenges, and prospects of phytosomes in cancer treatment. Thus, numerous phytosomal formulations incorporating plant-derived components have exhibited promising anticancer properties, with several formulations currently undergoing clinical trials.

Alkanols Regulate the Fluidity of Phospholipid Bilayer in Accordance to Their Concentration and Polarity.

In spite of the widespread use of alkanols as penetration enhancers, their effect on vesicular formulations remains largely unexplored. These can affect the stability and integrity of the phospholipid bilayers. In this study, we have investigated the interaction of linear (ethanol, butanol, hexanol, octanol) and branched alkanols (t-amylol and t-butanol) with three phospholipids (soya lecithin, SL; soy L-α-phosphatidylcholine, SPC; and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, DPPC). Thermodynamic and structural aspects of these interactions were studied as a function of the alkanol concentration and chain length. Our interpretations are based on isothermal titration calorimetry (ITC) and dynamic light scattering (DLS) experiments. We observed one-site interactions wherein hydroxyl and acyl groups interacted with the polar and nonpolar regions of the phospholipid, respectively. The stability and structural integrity of bilayers appeared to be dependent upon (a) the hydrocarbon chain length and concentration of alcohols, and (b) the degree of unsaturation in the phospholipid molecule. We found that these interactions triggered a reduction in the enthalpy which was compensated by increased entropy, keeping free energy negative. Drop in enthalpy indicates reversible disordering of the bilayer which enables the diffusion of alcohol without triggering destabilization. Ethanol engaged predominantly with the interface, and it resulted in higher enthalpic changes. Interactions became increasingly unfavorable with longer alcohols - a cutoff point was recorded with hexanol. The overall sequence of membrane disordering capability was recorded as follows: ethanol < butanol < octanol < hexanol. Octanol's larger size restricted its penetration in the bilayer, and hence it caused less enthalpic changes relative to hexanol. This could also be verified from the trends in the area ratio of these vesicles obtained from the DLS data. Branched alkanols displayed a lower binding affinity with the phospholipids relative to their linear counterparts. These data are useful while contemplating the inclusion of short-chain alcohols as penetration enhancers in phospholipid vesicles.

UPLC-MS based lipidomics analysis on optimization of soybean phosphatidylethanolamine extraction

Soybean-derived phosphatidylethanolamine (PE) is a valuable phospholipid component yet its high-purity form is costly and its molecular structure is poorly understood. The present study combined solvent extraction and cryopurification to purify PE. The optimal extraction conditions were as follows: material-liquid ratio 1:15 (g/mL), ethanol base concentration 100:4 (Vanhydrous ethanol /V25% ammonia), extraction temperature 40 °C, time 60 min, extraction twice. The cryopurification conditions were: material-liquid ratio 1:60, ethanol base concentration 100:6 (Vanhydrous ethanol/V25% ammonia), freezing temperature − 20 °C, time 20 h. UPLC-QTOF-MS/MS analysis revealed phospholipid composition of raw material, crude product, and purified product. The results showed that the purity of PE in the purified products was 76.74%, and the yield was 72.43% under optimal conditions. 181 phospholipid molecules were quantified. The study successfully explored high-purity PE preparation method and the composition of PE product. It provides a basis for the subsequent exploration of its biofunction and potential applications.

Effects of short-term supplementation with DHA-enriched phosphatidylcholine and phosphatidylserine on lipid profiles in the brain and liver of n-3 PUFA-deficient mice in early life after weaning.

Lack of n-3 polyunsaturated fatty acids during the period of maternity drastically lowers the docosahexaenoic acid (DHA) level in the brain of offspring and studies have demonstrated that different molecular forms of DHA are beneficial to brain development. The aim of this study was to investigate the effect of short-term supplementation with DHA-enriched phosphatidylserine (PS) and phosphatidylcholine (PC) on DHA levels in the liver and brain of congenital n-3-deficient mice. Dietary supplementation with DHA significantly changed the fatty acid composition of various phospholipid molecules in the cerebral cortex and liver while DHA-enriched phospholipid was more effective than DHA triglyceride (TG) in increasing brain and liver DHA. Both DHA-PS and DHA-PC could effectively increase the DHA levels, but DHA in the PS form was superior to PC in the contribution of DHA content in the brain ether-linked PC (ePC) and liver lyso-phosphatidylcholine molecular species. DHA-PC showed more significant effects on the increase of DHA in liver TG, PC, ePC, phosphatidylethanolamine (PE) and PE plasmalogen (pPE) molecular species and decreasing the arachidonic acid level in liver PC plasmalogen, ePC, PE and pPE molecular species compared with DHA-PS. The effect of dietary interventions with different molecular forms of DHA for brain and liver lipid profiles is different, which may provide theoretical guidance for dietary supplementation of DHA for people. © 2024 Society of Chemical Industry.

Cell membrane-inspired self-assembly corrosion resistant liquid metal composite coating with photothermal/electrothermal anti-icing/de-icing performance

Liquid metals have been expected to be promising photothermal/electrothermal anti-icing materials for their excellent electrical and thermal conductivity. However, inescapable oxidation and corrosion limit the life and efficiency of liquid metal materials. Inspired by the self-assembly of phospholipid molecules in cell membranes, self-assembly corrosion resistant liquid metal composite coating is designed to protect liquid metal from icing and corrosion hazards. Based on self-assembly of fluor‑silicon molecules mimicking phospholipid molecules and micro-nano surface morphology, the coating has water contact angle of 150.8°and icing delay time of 497 s, which is 4.21 times that of unmodified liquid metal. Under the combined action of 80.5 °C photothermal effect and superhydrophobicity, the de-icing efficiency of the coating is 2.04 times that of the unmodified liquid metal. The photothermal de-icing efficiency remains 99.3 % after two months of acid corrosion and 94.4 % after two months of alkali corrosion. In addition, the thermal network of the coating leads to thermal conductivity of 3.66 W/mK and flame retardancy with UL94 at V0 rating. The coating is made into an electrothermal device with 52.5 °C heating temperature and rapidly de-icing property. The cell membrane-inspired self-assembly liquid metal composite coating provides a secure solution for long-term photothermal/electrothermal anti-icing/de-icing in exposed environment.

A quantitative electrodiffusion model of antibacterial heavy metals: Ion influx through hydrophilic pores

Excessive heavy-metal ions in the cytoplasm, being toxic ions, can inactivate bacteria, which has been widely used as an effective antibacterial method. Nevertheless, how such toxic ions can be transported into bacteria is poorly understood. Here, we discovered a new mechanism showing that toxic ions electro-diffuse into the cytoplasm through the inherent hydrophilic pores in the cell membrane of living bacteria. Transmembrane potential induces recoverable defects by enhancing the thermal fluctuation of phospholipid molecules. By integrating electroporation, surface potential, and cell osmotic pressure, we develop a simple model for the influx rate of heavy metal ions into living bacteria. Our modeling results agree well with the experimental ones on the survival rates of Gram-negative and Gram-positive bacteria.

Development of a highly efficient solubilization method for mass spectrometric analysis of phospholipids in living single cells.

Phospholipids are vital constituents of the cell membrane and aid in signal transduction. Phospholipid profiles vary distinctively with the cell type. Notably, specific phospholipid molecules are present in significantly higher or lower concentrations in cancer cells versus normal cells. In this study, live single-cell mass spectrometry (MS) was developed for analyzing phospholipids at the single-cell level. This method facilitates rapid molecular analysis of cells under microscopic observation. For nanoelectrospray ionization, phospholipids were extracted from single cells isolated in a glass capillary through a high-efficiency process. Cell-derived phosphatidylcholines were detected with high sensitivity when trehalose C14 was added as a solubilizing reagent. Trehalose C14 can solubilize cells at low concentrations owing to its low critical micelle concentration, and exerts minimal matrix effects (such as suppressing ionization and causing peak overlap) in the MS analysis of cellular molecules. Analyses of phospholipids in Raji and HEV0070 cells using the developed method revealed specific peaks of phosphatidylcholine and sphingomyelin in the respective cells. The developed technique not only affords phospholipid profiles at the single-cell level, but also holds promise for identifying biomarkers associated with various diseases, particularly cancer.

Mesoporous nanoperforators as membranolytic agents via nano- and molecular-scale multi-patterning

Plasma membrane lysis is an effective anticancer strategy, which mostly relying on soluble molecular membranolytic agents. However, nanomaterial-based membranolytic agents has been largely unexplored. Herein, we introduce a mesoporous membranolytic nanoperforators (MLNPs) via a nano- and molecular-scale multi-patterning strategy, featuring a spiky surface topography (nanoscale patterning) and molecular-level periodicity in the spikes with a benzene-bridged organosilica composition (molecular-scale patterning), which cooperatively endow an intrinsic membranolytic activity. Computational modelling reveals a nanospike-mediated multivalent perforation behaviour, i.e., multiple spikes induce nonlinearly enlarged membrane pores compared to a single spike, and that benzene groups aligned parallelly to a phospholipid molecule show considerably higher binding energy than other alignments, underpinning the importance of molecular ordering in phospholipid extraction for membranolysis. Finally, the antitumour activity of MLNPs is demonstrated in female Balb/c mouse models. This work demonstrates assembly of organosilica based bioactive nanostructures, enabling new understandings on nano-/molecular patterns co-governed nano-bio interaction.

Constitutive activation mechanism of a class C GPCR.

Class C G-protein-coupled receptors (GPCRs) are activated through binding of agonists to the large extracellular domain (ECD) followed by rearrangement of the transmembrane domains (TMDs). GPR156, a class C orphan GPCR, is unique because it lacks an ECD and exhibits constitutive activity. Impaired GPR156-Gi signaling contributes to loss of hearing. Here we present the cryo-electron microscopy structures of human GPR156 in the Go-free and Go-coupled states. We found that an endogenous phospholipid molecule is located within each TMD of the GPR156 dimer. Asymmetric binding of Gα to the phospholipid-bound GPR156 dimer restructures the first and second intracellular loops and the carboxy-terminal part of the elongated transmembrane 7 (TM7) without altering dimer conformation. Our findings reveal that GPR156 is a transducer for phospholipid signaling. Constant binding of abundant phospholipid molecules and the G-protein-induced reshaping of the cytoplasmic face provide a basis for the constitutive activation of GPR156.