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Microbiology and Molecular Biology... Sep 2022Phospholipids are vital membrane constituents that determine cell functions and interactions with the environment. For bacterial pathogens, rapid adjustment of... (Review)
Review
Phospholipids are vital membrane constituents that determine cell functions and interactions with the environment. For bacterial pathogens, rapid adjustment of phospholipid composition to changing conditions during infection can be crucial for growth and survival. Fatty acid synthesis (FASII) regulators are central to this process. This review puts the spotlight on FabT, a MarR-family regulator of FASII characterized in streptococci, enterococci, and lactococci. Roles of FabT in virulence, as reported in mouse and nonhuman primate infection models, will be discussed. We present FabT structure, the FabT regulon, and changes in FabT regulation according to growth conditions. A unique feature of FabT concerns its modulation by an unconventional corepressor, acyl-acyl-carrier protein (ACP). Some bacteria express two ACP proteins, which are distinguished by their interactions with endogenous or exogenous fatty acid sources, one of which causes strong FabT repression. This system seems to allow preferred use of environmental fatty acids, thereby saving energy by limiting futile FASII activity. Control of expression and FabT activity link various metabolic pathways to FASII. The various physiological consequences of FabT loss summarized here suggest that FabT has potential as a narrow range therapeutic target.
Topics: Acyl Carrier Protein; Animals; Bacteria; Bacterial Proteins; Co-Repressor Proteins; Fatty Acids; Gene Expression Regulation, Bacterial; Mice; Phospholipids; Transcription Factors; Virulence
PubMed: 35726719
DOI: 10.1128/mmbr.00029-22 -
The Plant Cell Sep 2022Pollen tube guidance regulates the growth direction and ovule targeting of pollen tubes in pistils, which is crucial for the completion of sexual reproduction in...
Pollen tube guidance regulates the growth direction and ovule targeting of pollen tubes in pistils, which is crucial for the completion of sexual reproduction in flowering plants. The Arabidopsis (Arabidopsis thaliana) pollen-specific receptor kinase (PRK) family members PRK3 and PRK6 are specifically tip-localized and essential for pollen tube growth and guidance. However, the mechanisms controlling the polar localization of PRKs at the pollen tube tip are unclear. The Arabidopsis P4-ATPase ALA3 helps establish the polar localization of apical phosphatidylserine (PS) in pollen tubes. Here, we discovered that loss of ALA3 function caused pollen tube defects in growth and ovule targeting and significantly affected the polar localization pattern of PRK3 and PRK6. Both PRK3 and PRK6 contain two polybasic clusters in the intracellular juxtamembrane domain, and they bound to PS in vitro. PRK3 and PRK6 with polybasic cluster mutations showed reduced or abolished binding to PS and altered polar localization patterns, and they failed to effectively complement the pollen tube-related phenotypes of prk mutants. These results suggest that ALA3 influences the precise localization of PRK3, PRK6, and other PRKs by regulating the distribution of PS, which plays a key role in regulating pollen tube growth and guidance.
Topics: Adenosine Triphosphatases; Arabidopsis; Arabidopsis Proteins; Phosphatidylserines; Phospholipids; Pollen Tube; Protein Serine-Threonine Kinases
PubMed: 35861414
DOI: 10.1093/plcell/koac208 -
Journal of Dairy Science Feb 2021In this study dairy phospholipid (PL) gels were made using 3 different concentrations of PL (15%, 30%, and 45%) and soybean oil to determine the gel-forming ability and...
In this study dairy phospholipid (PL) gels were made using 3 different concentrations of PL (15%, 30%, and 45%) and soybean oil to determine the gel-forming ability and functional traits that dairy PL have. After 24 h of storage the visual stability, crystal morphology, solid fat content, melting behavior, viscosity, and oil binding capacity of the gels were evaluated. All samples showed visual stability, whereas polarized light microscopy showed that high concentrations of PL reduced PL mobility, preventing tubular micelles from forming at high concentrations of PL (45%). Solid fat content increased with an increase in PL concentration. The melting enthalpy increased as the concentration of PL increased. The viscosity was assessed at 0.01, 0.1, and 1.0 1/s shear rates. A significant difference was observed between the 45% PL samples and the other samples at low and intermediate shear, but at high shear levels, a significant difference was only seen between the 15% PL sample and the other samples. The oil binding capacity showed a significant difference between the 45% PL sample and the other 2 samples. This study shows that dairy PL can be added to a vegetable oil to produce semi-solid material with appropriate functional properties.
Topics: Animals; Chemical Phenomena; Crystallization; Dairy Products; Fats; Gels; Phospholipids; Soybean Oil; Thermodynamics; Viscosity
PubMed: 33189284
DOI: 10.3168/jds.2020-18737 -
Proceedings of the National Academy of... Jun 2020Temporally harmonized elimination of damaged or unnecessary organelles and cells is a prerequisite of health. Under Type 2 inflammatory conditions, human airway...
Temporally harmonized elimination of damaged or unnecessary organelles and cells is a prerequisite of health. Under Type 2 inflammatory conditions, human airway epithelial cells (HAECs) generate proferroptotic hydroperoxy-arachidonoyl-phosphatidylethanolamines (HpETE-PEs) as proximate death signals. Production of 15-HpETE-PE depends on activation of 15-lipoxygenase-1 (15LO1) in complex with PE-binding protein-1 (PEBP1). We hypothesized that cellular membrane damage induced by these proferroptotic phospholipids triggers compensatory prosurvival pathways, and in particular autophagic pathways, to prevent cell elimination through programmed death. We discovered that PEBP1 is pivotal to driving dynamic interactions with both proferroptotic 15LO1 and the autophagic protein microtubule-associated light chain-3 (LC3). Further, the 15LO1-PEBP1-generated ferroptotic phospholipid, 15-HpETE-PE, promoted LC3-I lipidation to stimulate autophagy. This concurrent activation of autophagy protects cells from ferroptotic death and release of mitochondrial DNA. Similar findings are observed in Type 2 Hi asthma, where high levels of both 15LO1-PEBP1 and LC3-II are seen in HAECs, in association with low bronchoalveolar lavage fluid mitochondrial DNA and more severe disease. The concomitant activation of ferroptosis and autophagy by 15LO1-PEBP1 complexes and their hydroperoxy-phospholipids reveals a pathobiologic pathway relevant to asthma and amenable to therapeutic targeting.
Topics: Adult; Animals; Arachidonate 15-Lipoxygenase; Asthma; Autophagy; Bronchoalveolar Lavage Fluid; Cell Line; Cell Survival; Epithelial Cells; Female; Ferroptosis; Gene Knockout Techniques; Humans; Hydroxyeicosatetraenoic Acids; Interleukin-13; Male; Mice; Microtubule-Associated Proteins; Molecular Dynamics Simulation; Phosphatidylethanolamine Binding Protein; Phosphatidylethanolamines; Primary Cell Culture; Protein Binding; Severity of Illness Index
PubMed: 32513718
DOI: 10.1073/pnas.1921618117 -
ACS Chemical Neuroscience Jun 2021Cooperative binding is a key feature of metabolic pathways, signaling, and transport processes. It provides tight regulation over a narrow concentration interval of a...
Cooperative binding is a key feature of metabolic pathways, signaling, and transport processes. It provides tight regulation over a narrow concentration interval of a ligand, thus enabling switching to be triggered by small concentration variations. The data presented in this work reveal strong positive cooperativity of α-synuclein binding to phospholipid membranes. Fluorescence cross-correlation spectroscopy, confocal microscopy, and -TEM results show that in excess of vesicles α-synuclein does not distribute randomly but binds only to a fraction of all available vesicles. Furthermore, α-synuclein binding to a supported lipid bilayer observed with total internal reflection fluorescence microscopy displays a much steeper dependence of bound protein on total protein concentration than expected for independent binding. The same phenomenon was observed in the case of α-synuclein binding to unilamellar vesicles of sizes in the nm and μm range as well as to flat supported lipid bilayers, ruling out that nonuniform binding of the protein is governed by differences in membrane curvature. Positive cooperativity of α-synuclein binding to lipid membranes means that the affinity of the protein to a membrane is higher where there is already protein bound compared to a bare membrane. The phenomenon described in this work may have implications for α-synuclein function in synaptic transmission and other membrane remodeling events.
Topics: Lipid Bilayers; Phospholipids; Protein Binding; Spectrometry, Fluorescence; Unilamellar Liposomes; alpha-Synuclein
PubMed: 34076426
DOI: 10.1021/acschemneuro.1c00006 -
Life Science Alliance Feb 2023Autotaxin is primarily known for the formation of lysophosphatidic acid (LPA) from lysophosphatidylcholine. LPA is an important signaling phospholipid that can bind to...
Autotaxin is primarily known for the formation of lysophosphatidic acid (LPA) from lysophosphatidylcholine. LPA is an important signaling phospholipid that can bind to six G protein-coupled receptors (LPA). The ATX-LPA signaling axis is a critical component in many physiological and pathophysiological conditions. Here, we describe a potent inhibition of Δ--tetrahydrocannabinol (THC), the main psychoactive compound of medicinal cannabis and related cannabinoids, on the catalysis of two isoforms of ATX with nanomolar apparent EC values. Furthermore, we decipher the binding interface of ATX to THC, and its derivative 9(R)-Δ6a,10a-THC (6a10aTHC), by X-ray crystallography. Cellular experiments confirm this inhibitory effect, revealing a significant reduction of internalized LPA in the presence of THC with simultaneous ATX and lysophosphatidylcholine stimulation. Our results establish a functional interaction of THC with autotaxin-LPA signaling and highlight novel aspects of medicinal cannabis therapy.
Topics: Lysophosphatidylcholines; Lysophospholipids; Medical Marijuana; Receptors, Lysophosphatidic Acid; Dronabinol
PubMed: 36623871
DOI: 10.26508/lsa.202201595 -
Biomolecules Jun 2023G protein-coupled receptors (GPCRs) are embedded in phospholipid membrane bilayers with cholesterol representing 34% of the total lipid content in mammalian plasma... (Review)
Review
G protein-coupled receptors (GPCRs) are embedded in phospholipid membrane bilayers with cholesterol representing 34% of the total lipid content in mammalian plasma membranes. Membrane lipids interact with GPCRs structures and modulate their function and drug-stimulated signaling through conformational selection. It has been shown that anionic phospholipids form strong interactions between positively charged residues in the G protein and the TM5-TM6-TM 7 cytoplasmic interface of class A GPCRs stabilizing the signaling GPCR-G complex. Cholesterol with a high content in plasma membranes can be identified in more specific sites in the transmembrane region of GPCRs, such as the Cholesterol Consensus Motif (CCM) and Cholesterol Recognition Amino Acid Consensus (CRAC) motifs and other receptor dependent and receptor state dependent sites. Experimental biophysical methods, atomistic (AA) MD simulations and coarse-grained (CG) molecular dynamics simulations have been applied to investigate these interactions. We emphasized here the impact of phosphatidyl inositol-4,5-bisphosphate (PtdIns(4,5)P or PIP), a minor phospholipid component and of cholesterol on the function-related conformational equilibria of the human A adenosine receptor (AR), a representative receptor in class A GPCR. Several GPCRs of class A interacted with PIP and cholesterol and in many cases the mechanism of the modulation of their function remains unknown. This review provides a helpful comprehensive overview for biophysics that enter the field of GPCRs-lipid systems.
Topics: Animals; Humans; Binding Sites; Cholesterol; Mammals; Molecular Dynamics Simulation; Phospholipids; Receptors, G-Protein-Coupled; Receptors, Purinergic P1; Receptor, Adenosine A2A
PubMed: 37371538
DOI: 10.3390/biom13060957 -
The Journal of Biological Chemistry Jun 2023The human AdipoR2 and its Caenorhabditis elegans homolog PAQR-2 are multipass plasma membrane proteins that protect cells against membrane rigidification. However, how...
The human AdipoR2 and its Caenorhabditis elegans homolog PAQR-2 are multipass plasma membrane proteins that protect cells against membrane rigidification. However, how AdipoR2 promotes membrane fluidity mechanistically is not clear. Using 13C-labeled fatty acids, we show that AdipoR2 can promote the elongation and incorporation of membrane-fluidizing polyunsaturated fatty acids into phospholipids. To elucidate the molecular basis of these activities, we performed immunoprecipitations of tagged AdipoR2 and PAQR-2 expressed in HEK293 cells or whole C. elegans, respectively, and identified coimmunoprecipitated proteins using mass spectrometry. We found that several of the evolutionarily conserved AdipoR2/PAQR-2 interactors are important for fatty acid elongation and incorporation into phospholipids. We experimentally verified some of these interactions, namely, with the dehydratase HACD3 that is essential for the third of four steps in long-chain fatty acid elongation and ACSL4 that is important for activation of unsaturated fatty acids and their channeling into phospholipids. We conclude that AdipoR2 and PAQR-2 can recruit protein interactors to promote the production and incorporation of unsaturated fatty acids into phospholipids.
Topics: Animals; Humans; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Cell Membrane; Fatty Acids; HEK293 Cells; Membrane Fluidity; Phospholipids; Receptors, Adiponectin; Protein Binding
PubMed: 37164154
DOI: 10.1016/j.jbc.2023.104799 -
Journal of Lipid Research 2021Phospholipidosis, the excessive accumulation of phospholipids within lysosomes, is a pathological response observed following exposure to many drugs across multiple... (Review)
Review
Phospholipidosis, the excessive accumulation of phospholipids within lysosomes, is a pathological response observed following exposure to many drugs across multiple therapeutic groups. A clear mechanistic understanding of the causes and implications of this form of drug toxicity has remained elusive. We previously reported the discovery and characterization of a lysosome-specific phospholipase A2 (PLA2G15) and later reported that amiodarone, a known cause of drug-induced phospholipidosis, inhibits this enzyme. Here, we assayed a library of 163 drugs for inhibition of PLA2G15 to determine whether this phospholipase was the cellular target for therapeutics other than amiodarone that cause phospholipidosis. We observed that 144 compounds inhibited PLA2G15 activity. Thirty-six compounds not previously reported to cause phospholipidosis inhibited PLA2G15 with IC values less than 1 mM and were confirmed to cause phospholipidosis in an in vitro assay. Within this group, fosinopril was the most potent inhibitor (IC 0.18 μM). Additional characterization of the inhibition of PLA2G15 by fosinopril was consistent with interference of PLA2G15 binding to liposomes. PLA2G15 inhibition was more accurate in predicting phospholipidosis compared with in silico models based on pKa and ClogP, measures of protonation, and transport-independent distribution in the lysosome, respectively. In summary, PLA2G15 is a primary target for cationic amphiphilic drugs that cause phospholipidosis, and PLA2G15 inhibition by cationic amphiphilic compounds provides a potentially robust screening platform for potential toxicity during drug development.
Topics: Animals; Enzyme Inhibitors; Humans; Lysosomes; Phospholipases A2; Phospholipids
PubMed: 34087196
DOI: 10.1016/j.jlr.2021.100089 -
Chemphyschem : a European Journal of... Aug 2020Ions are ubiquitous in nature. They play a key role for many biological processes on the molecular scale, from molecular interactions, to mechanical properties, to... (Review)
Review
Ions are ubiquitous in nature. They play a key role for many biological processes on the molecular scale, from molecular interactions, to mechanical properties, to folding, to self-organisation and assembly, to reaction equilibria, to signalling, to energy and material transport, to recognition etc. Going beyond monovalent ions to multivalent ions, the effects of the ions are frequently not only stronger (due to the obviously higher charge), but qualitatively different. A typical example is the process of binding of multivalent ions, such as Ca , to a macromolecule and the consequences of this ion binding such as compaction, collapse, potential charge inversion and precipitation of the macromolecule. Here we review these effects and phenomena induced by multivalent ions for biological (macro)molecules, from the "atomistic/molecular" local picture of (potentially specific) interactions to the more global picture of phase behaviour including, e. g., crystallisation, phase separation, oligomerisation etc. Rather than attempting an encyclopedic list of systems, we rather aim for an embracing discussion using typical case studies. We try to cover predominantly three main classes: proteins, nucleic acids, and amphiphilic molecules including interface effects. We do not cover in detail, but make some comparisons to, ion channels, colloidal systems, and synthetic polymers. While there are obvious differences in the behaviour of, and the relevance of multivalent ions for, the three main classes of systems, we also point out analogies. Our attempt of a comprehensive discussion is guided by the idea that there are not only important differences and specific phenomena with regard to the effects of multivalent ions on the main systems, but also important similarities. We hope to bridge physico-chemical mechanisms, concepts of soft matter, and biological observations and connect the different communities further.
Topics: Cations; Lipid Bilayers; Metals; Micelles; Nucleic Acids; Phospholipids; Protein Binding; Proteins; Static Electricity
PubMed: 32406605
DOI: 10.1002/cphc.202000162