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Intestinal CD36 and Other Key Proteins of Lipid Utilization: Role in Absorption and Gut Homeostasis.Comprehensive Physiology Mar 2018Several proteins have been implicated in fatty acid (FA) transport by enterocytes including the scavenger receptor CD36 (SR-B2), the scavenger receptor B1 (SR-B1) a... (Review)
Review
Several proteins have been implicated in fatty acid (FA) transport by enterocytes including the scavenger receptor CD36 (SR-B2), the scavenger receptor B1 (SR-B1) a member of the CD36 family and the FA transport protein 4 (FATP4). Here, we review the regulation of enterocyte FA uptake and its function in lipid absorption including prechylomicron formation, assembly and transport. Emphasis is given to CD36, which is abundantly expressed along the digestive tract of rodents and humans and has been the most studied. We also address the pleiotropic functions of CD36 that go beyond lipid absorption and metabolism to include recent evidence of its impact on intestinal homeostasis and barrier maintenance. Areas of progress involving contribution of membrane phospholipid remodeling and of cytosolic FA-binding proteins, FABP1 and FABP2 to fat absorption will be covered. © 2018 American Physiological Society. Compr Physiol 8:493-507, 2018.
Topics: Animals; Biological Transport; CD36 Antigens; Chylomicrons; Digestive System; Enterocytes; Fatty Acids; Homeostasis; Humans; Intestinal Absorption; Lipid Metabolism; Phospholipids
PubMed: 29687890
DOI: 10.1002/cphy.c170026 -
Biochimica Et Biophysica Acta Jun 2016Binding of coagulation factors X (fX) and Xa (fXa) to activated platelets is required for the formation of membrane-dependent enzymatic complexes of intrinsic tenase and... (Review)
Review
Hysteresis-like binding of coagulation factors X/Xa to procoagulant activated platelets and phospholipids results from multistep association and membrane-dependent multimerization.
Binding of coagulation factors X (fX) and Xa (fXa) to activated platelets is required for the formation of membrane-dependent enzymatic complexes of intrinsic tenase and prothrombinase. We carried out an in-depth characterization of fX/fXa binding to phospholipids and gel-filtered, thrombin-activated platelets. Flow cytometry, surface plasmon resonance, and computational modeling were used to investigate interactions of fX/fXa with the membranes. Confocal microscopy was employed to study fXa binding to platelet thrombi formed in flowing whole blood under arterial conditions. Binding of fX/fXa to either vesicles or procoagulant platelets did not follow a traditional one-step reversible binding model. Their dissociation was a two-step process resulting in a plateau that was up to 10-fold greater than the saturation value observed in the association experiments. Computational modeling and experimental evidence suggested that this was caused by a combination of two-step association (mainly for fX) and multimerization on the membrane (mainly for fXa). Importantly, fX formed multimers with fXa, thereby improving its retention. The same binding/dissociation hysteresis was observed for annexin V known to form trimers on the membranes. Experiments with platelets from gray syndrome patients showed that alpha-granular factor Va provided an additional high-affinity binding site for fXa that did not affect the hysteresis. Confocal microscopy observation of fXa binding to platelet thrombi in a flow chamber and its wash-out confirmed that this phenomenon persisted under physiologically relevant conditions. This suggests its possible role of "locking" coagulation factors on the membrane and preventing their inhibition in plasma and removal from thrombi by flow.
Topics: Biopolymers; Blood Platelets; Computer Simulation; Factor X; Factor Xa; Humans; Phospholipids; Platelet Activation; Surface Plasmon Resonance
PubMed: 26874201
DOI: 10.1016/j.bbamem.2016.02.008 -
Biochimica Et Biophysica Acta.... Sep 2020NMR is a sophisticated method for investigation of structure and dynamics of lipid and protein molecules in membranes. Vibrational spectroscopy is also powerful because... (Review)
Review
NMR is a sophisticated method for investigation of structure and dynamics of lipid and protein molecules in membranes. Vibrational spectroscopy is also powerful because of relatively high resolution and sensitivity, and easier access than NMR. A combined use of these spectroscopies could provide important insights into the membrane biophysics. A structural analysis of phosphatidylethanolamine (PE) bilayers in built-up films by infrared dichroism suggested that polar groups oriented parallel to the membrane surface. A Raman analysis of phosphatidylcholine (PC) revealed that the gauche conformation was preferred for the choline backbone not only in solid, but also in the gel and liquid-crystalline states. The polar group structure of DPPC bilayers in the liquid-crystalline state was determined by analyzing deuterium quadrupole splitting of the choline group and phosphorus chemical shift anisotropy of the phosphate group in combination with restriction of the gauche conformation of the choline group determined by Raman spectroscopy. This was an excellent complementarity of NMR and vibrational spectroscopies. The deuterium quadrupole splitting values mentioned above were found to change on addition of ions such as NaCl, CaCl, and LaCl, suggesting that a structural change takes place on ion binding and the polar group of PC works as an electric charge sensor of membranes. The ion-bound structure was determined by NMR using the restriction from Raman spectroscopy. The PN vector of phosphorylcholine group was inclined by 63° from the membrane surface, while the inclination was 18° in the ion-free form. The deuterium quadrupole splitting values and phosphorus powder patterns revealed that on mixing with phosphatidylglycerol (PG) or cardiolipin (CL), PC did not change its dynamic structure of the glycerol backbone, but PE did. The mixture of PE with PG or CL shared a new dynamic structure, suggesting their adaptive miscibility in the molecular level. PC was molecularly immiscible with any of PE, PG, and CL. The molecular miscibility would regulate not only interactions of proteins with mixed bilayers but also formation of asymmetric lipid membranes. Interactions of crown-ether (CE) modified artificial microbial peptides with phospholipid bilayers were investigated by NMR and FTIR. CE-modified 14-mers with one or two basic amino acid residues revealed position-specific selectivity for the suppression of calcein leakage from PC vesicles but did not for that from PG vesicles, suggesting that structures of the lipid polar groups play crucial roles in different responses of the vesicles to the positively charged peptides. Manipulation of the peptide-polar group interaction can be used for drug design.
Topics: Cardiolipins; Lipid Bilayers; Nuclear Magnetic Resonance, Biomolecular; Phosphatidylethanolamines; Phosphatidylglycerols; Spectrum Analysis, Raman
PubMed: 32407775
DOI: 10.1016/j.bbamem.2020.183352 -
Journal of Thrombosis and Haemostasis :... Aug 2019Blood coagulation factor Va serves an indispensable role in hemostasis as cofactor for the serine protease factor Xa. In the presence of an anionic phospholipid membrane... (Review)
Review
Blood coagulation factor Va serves an indispensable role in hemostasis as cofactor for the serine protease factor Xa. In the presence of an anionic phospholipid membrane and calcium ions, factors Va and Xa assemble into the prothrombinase complex. Following formation of the ternary complex with the macromolecular zymogen substrate prothrombin, the latter is rapidly converted into thrombin, the key regulatory enzyme of coagulation. Over the years, multiple binding sites have been identified in factor Va that play a role in the interaction of the cofactor with factor Xa, prothrombin, or the anionic phospholipid membrane surface. In this review, an overview of the currently available information on these interactive sites in factor Va is provided, and data from biochemical approaches and 3D structural protein complex models are discussed. The structural models have been generated in recent years and provide novel insights into the molecular requirements for assembly of both the prothrombinase and the ternary prothrombinase-prothrombin complexes. Integrated knowledge of functionally important regions in factor Va will allow for a better understanding of factor Va cofactor activity.
Topics: Binding Sites; Blood Coagulation; Cell Membrane; Factor Va; Factor Xa; Humans; Models, Molecular; Phospholipids; Protein Binding; Protein Interaction Domains and Motifs; Prothrombin; Structure-Activity Relationship; Thromboplastin
PubMed: 31102425
DOI: 10.1111/jth.14487 -
Biophysical Journal Nov 2021Immune surveillance cells such as T cells and phagocytes utilize integral plasma membrane receptors to recognize surface signatures on triggered and activated cells...
Immune surveillance cells such as T cells and phagocytes utilize integral plasma membrane receptors to recognize surface signatures on triggered and activated cells such as those in apoptosis. One such family of plasma membrane sensors, the transmembrane immunoglobulin and mucin domain (Tim) proteins, specifically recognize phosphatidylserine (PS) but elicit distinct immunological responses. The molecular basis for the recognition of lipid signals on target cell surfaces is not well understood. Previous results suggest that basic side chains present at the membrane interface on the Tim proteins might facilitate association with additional anionic lipids including but not necessarily limited to PS. We, therefore, performed a comparative quantitative analysis of the binding of the murine Tim1, Tim3, and Tim4, to synthetic anionic phospholipid membranes under physiologically relevant conditions. X-ray reflectivity and vesicle binding studies were used to compare the water-soluble domain of Tim3 with results previously obtained for Tim1 and Tim4. Although a calcium link was essential for all three proteins, the three homologs differed in how they balance the hydrophobic and electrostatic interactions driving membrane association. The proteins also varied in their sensing of phospholipid chain unsaturation and showed different degrees of cooperativity in their dependence on bilayer PS concentration. Surprisingly, trace amounts of anionic phosphatidic acid greatly strengthened the bilayer association of Tim3 and Tim4, but not Tim1. A novel mathematical model provided values for the binding parameters and illuminated the complex interplay among ligands. In conclusion, our results provide a quantitative description of the contrasting selectivity used by three Tim proteins in the recognition of phospholipids presented on target cell surfaces. This paradigm is generally applicable to the analysis of the binding of peripheral proteins to target membranes through the heterotropic cooperative interactions of multiple ligands.
Topics: Animals; Hepatitis A Virus Cellular Receptor 1; Membrane Proteins; Membranes; Mice; Mucins; Phosphatidylserines
PubMed: 34529946
DOI: 10.1016/j.bpj.2021.09.016 -
EMBO Reports Oct 2021Accurate Notch signalling is critical for development and homeostasis. Fine-tuning of Notch-ligand interactions has substantial impact on signalling outputs. Recent...
Accurate Notch signalling is critical for development and homeostasis. Fine-tuning of Notch-ligand interactions has substantial impact on signalling outputs. Recent structural studies have identified a conserved N-terminal C2 domain in human Notch ligands which confers phospholipid binding in vitro. Here, we show that Drosophila ligands Delta and Serrate adopt the same C2 domain structure with analogous variations in the loop regions, including the so-called β1-2 loop that is involved in phospholipid binding. Mutations in the β1-2 loop of the Delta C2 domain retain Notch binding but have impaired ability to interact with phospholipids in vitro. To investigate its role in vivo, we deleted five residues within the β1-2 loop of endogenous Delta. Strikingly, this change compromises ligand function. The modified Delta enhances phenotypes produced by Delta loss-of-function alleles and suppresses that of Notch alleles. As the modified protein is present on the cell surface in normal amounts, these results argue that C2 domain phospholipid binding is necessary for robust signalling in vivo fine-tuning the balance of trans and cis ligand-receptor interactions.
Topics: C2 Domains; Drosophila Proteins; Humans; Ligands; Membrane Proteins; Phospholipids; Receptors, Notch
PubMed: 34347930
DOI: 10.15252/embr.202152729 -
Experimental & Molecular Medicine Feb 2024Helicobacter pylori, particularly cytotoxin-associated gene A (CagA)-positive strains, plays a key role in the progression of gastric cancer (GC). Ferroptosis,...
Helicobacter pylori, particularly cytotoxin-associated gene A (CagA)-positive strains, plays a key role in the progression of gastric cancer (GC). Ferroptosis, associated with lethal lipid peroxidation, has emerged to play an important role in malignant and infectious diseases, but the role of CagA in ferroptosis in cancer cells has not been determined. Here, we report that CagA confers GC cells sensitivity to ferroptosis both in vitro and in vivo. Mechanistically, CagA promotes the synthesis of polyunsaturated ether phospholipids (PUFA-ePLs), which is mediated by increased expression of alkylglycerone phosphate synthase (AGPS) and 1-acylglycerol-3-phosphate O-acyltransferase 3 (AGPAT3), leading to susceptibility to ferroptosis. This susceptibility is mediated by activation of the MEK/ERK/SRF pathway. SRF is a crucial transcription factor that increases AGPS transcription by binding to the AGPS promoter region. Moreover, the results demonstrated that CagA-positive cells are more sensitive to apatinib than are CagA-negative cells, suggesting that detecting the H. pylori CagA status may aid patient stratification for treatment with apatinib.
Topics: Humans; Stomach Neoplasms; Ferroptosis; Helicobacter pylori; Cytotoxins; Phospholipid Ethers
PubMed: 38383581
DOI: 10.1038/s12276-024-01167-5 -
Cell Reports Jan 2024Apicomplexan parasites possess specialized secretory organelles called rhoptries, micronemes, and dense granules that play a vital role in host infection. In this study,...
Apicomplexan parasites possess specialized secretory organelles called rhoptries, micronemes, and dense granules that play a vital role in host infection. In this study, we demonstrate that TgREMIND, a protein found in Toxoplasma gondii, is necessary for the biogenesis of rhoptries and dense granules. TgREMIND contains a Fes-CIP4 homology-Bin/Amphiphysin/Rvs (F-BAR) domain, which binds to membrane phospholipids, as well as a novel uncharacterized domain that we have named REMIND (regulator of membrane-interacting domain). Both the F-BAR domain and the REMIND are crucial for TgREMIND functions. When TgREMIND is depleted, there is a significant decrease in the abundance of dense granules and abnormal transparency of rhoptries, leading to a reduction in protein secretion from these organelles. The absence of TgREMIND inhibits host invasion and parasite dissemination, demonstrating that TgREMIND is essential for the proper function of critical secretory organelles required for successful infection by Toxoplasma.
Topics: Animals; Toxoplasma; Membrane Proteins; Protozoan Proteins; Organelles; Parasites; Phosphatidylinositols
PubMed: 38157297
DOI: 10.1016/j.celrep.2023.113601 -
Role of flippases, scramblases and transfer proteins in phosphatidylserine subcellular distribution.Traffic (Copenhagen, Denmark) Jan 2015It is well known that lipids are heterogeneously distributed throughout the cell. Most lipid species are synthesized in the endoplasmic reticulum (ER) and then... (Review)
Review
It is well known that lipids are heterogeneously distributed throughout the cell. Most lipid species are synthesized in the endoplasmic reticulum (ER) and then distributed to different cellular locations in order to create the distinct membrane compositions observed in eukaryotes. However, the mechanisms by which specific lipid species are trafficked to and maintained in specific areas of the cell are poorly understood and constitute an active area of research. Of particular interest is the distribution of phosphatidylserine (PS), an anionic lipid that is enriched in the cytosolic leaflet of the plasma membrane. PS transport occurs by both vesicular and non-vesicular routes, with members of the oxysterol-binding protein family (Osh6 and Osh7) recently implicated in the latter route. In addition, the flippase activity of P4-ATPases helps build PS membrane asymmetry by preferentially translocating PS to the cytosolic leaflet. This asymmetric PS distribution can be used as a signaling device by the regulated activation of scramblases, which rapidly expose PS on the extracellular leaflet and play important roles in blood clotting and apoptosis. This review will discuss recent advances made in the study of phospholipid flippases, scramblases and PS-specific lipid transfer proteins, as well as how these proteins contribute to subcellular PS distribution.
Topics: Adenosine Triphosphatases; Animals; Biological Transport; Cell Membrane; Endoplasmic Reticulum; Humans; Phosphatidylserines; Phospholipids
PubMed: 25284293
DOI: 10.1111/tra.12233 -
Acta Biochimica Polonica 2018Phosphatidic acid (PA) is the simplest glycerophospholipid naturally occurring in living organisms, and even though its content among other cellular lipids is minor, it... (Review)
Review
Phosphatidic acid (PA) is the simplest glycerophospholipid naturally occurring in living organisms, and even though its content among other cellular lipids is minor, it is drawing more and more attention due to its multiple biological functions. PA is a precursor for other phospholipids, acts as a lipid second messenger and, due to its structural properties, is also a modulator of membrane shape. Although much is known about interaction of PA with its effectors, the molecular mechanisms remain unresolved to a large degree. Throughout many of the well-characterized PA cellular sensors, no conserved binding domain can be recognized. Moreover, not much is known about the cellular dynamics of PA and how it is distributed among subcellular compartments. Remarkably, PA can play distinct roles within each of these compartments. For example, in the nucleus it behaves as a mitogen, influencing gene expression regulation, and in the Golgi membrane it plays a role in membrane trafficking. Here, we discuss how a biophysical experimental approach enabled PA behavior to be described in the context of a lipid bilayer and to what extent various physicochemical conditions may modulate the functional properties of this lipid. Understanding these aspects would help to unravel specific mechanisms of PA-driven membrane transformations and protein recruitment and thus would lead to a clearer picture of the biological role of PA.
Topics: Cell Compartmentation; Cell Membrane; Lipid Bilayers; Phosphatidic Acids
PubMed: 29913482
DOI: 10.18388/abp.2018_2592