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International Journal of Molecular... Apr 2023Electronegative LDL (LDL(-)) is a minor form of LDL present in blood for which proportions are increased in pathologies with increased cardiovascular risk. In vitro... (Review)
Review
Electronegative LDL (LDL(-)) is a minor form of LDL present in blood for which proportions are increased in pathologies with increased cardiovascular risk. In vitro studies have shown that LDL(-) presents pro-atherogenic properties, including a high susceptibility to aggregation, the ability to induce inflammation and apoptosis, and increased binding to arterial proteoglycans; however, it also shows some anti-atherogenic properties, which suggest a role in controlling the atherosclerotic process. One of the distinctive features of LDL(-) is that it has enzymatic activities with the ability to degrade different lipids. For example, LDL(-) transports platelet-activating factor acetylhydrolase (PAF-AH), which degrades oxidized phospholipids. In addition, two other enzymatic activities are exhibited by LDL(-). The first is type C phospholipase activity, which degrades both lysophosphatidylcholine (LysoPLC-like activity) and sphingomyelin (SMase-like activity). The second is ceramidase activity (CDase-like). Based on the complementarity of the products and substrates of these different activities, this review speculates on the possibility that LDL(-) may act as a sort of multienzymatic complex in which these enzymatic activities exert a concerted action. We hypothesize that LysoPLC/SMase and CDase activities could be generated by conformational changes in apoB-100 and that both activities occur in proximity to PAF-AH, making it feasible to discern a coordinated action among them.
Topics: Humans; Lipoproteins, LDL; 1-Alkyl-2-acetylglycerophosphocholine Esterase; Phospholipids; Sphingomyelins; Atherosclerosis; Arteries
PubMed: 37108253
DOI: 10.3390/ijms24087074 -
Biochimica Et Biophysica Acta.... Feb 2022Annexin A2 (AnxA2) is a calcium- and phospholipid-binding protein that plays roles in cellular processes involving membrane and cytoskeleton dynamics and is able to...
Annexin A2 (AnxA2) is a calcium- and phospholipid-binding protein that plays roles in cellular processes involving membrane and cytoskeleton dynamics and is able to associate to several partner proteins. However, the principal molecular partners of AnxA2 are negatively charged phospholipids such as phosphatidylserine and phosphatidyl-inositol-(4,5)-phosphate. Herein we have studied different aspects of membrane lipid rearrangements induced by AnxA2 membrane binding. X-ray diffraction data revealed that AnxA2 has the property to stabilize lamellar structures and to block the formation of highly curved lipid phases (inverted hexagonal phase, H). By using pyrene-labelled cholesterol and the environmental probe di-4-ANEPPDHQ, we observed that in model membranes, AnxA2 is able to modify both, cholesterol distribution and lipid compaction. In epithelial cells, we observed that AnxA2 localizes to membranes of different lipid order. The protein binding to membranes resulted in both, increases and/or decreases in membrane order depending on the cellular membrane regions. Overall, AnxA2 showed the capacity to modulate plasma membrane properties by inducing lipid redistribution that may lead to an increase in order or disorder of the membranes.
Topics: Annexin A2; Biophysical Phenomena; Calcium; Carrier Proteins; Cell Communication; Cell Membrane; Cytoskeleton; Humans; Membrane Lipids; Phosphatidylserines; Phospholipids
PubMed: 34699769
DOI: 10.1016/j.bbamem.2021.183810 -
Methods in Molecular Biology (Clifton,... 2021The ability to quantify protein-protein interactions without adding labels to protein has made isothermal titration calorimetry (ITC) a preferred technique to study...
The ability to quantify protein-protein interactions without adding labels to protein has made isothermal titration calorimetry (ITC) a preferred technique to study proteins in aqueous solution. Here, we describe the application of ITC to the study of protein-protein interactions in membrane mimics using the association of integrin αIIb and β3 transmembrane domains in phospholipid bicelles as an example. A higher conceptual and experimental effort compared to water-soluble proteins is required for membrane proteins and rewarded with rare thermodynamic insight into this central class of proteins.
Topics: Animals; Binding Sites; Calorimetry; Humans; Integrin alpha2; Integrin beta3; Membranes, Artificial; Models, Molecular; Molecular Conformation; Phospholipids; Protein Binding; Protein Domains; Protein Interaction Maps
PubMed: 33877623
DOI: 10.1007/978-1-0716-1394-8_5 -
European Biophysics Journal : EBJ Dec 2022Human phospholipid scramblase 1 (hPLSCR1) is a 37 kDa multi-compartmental protein, which was initially identified as a Ca-dependent phospholipid translocator upon...
Human phospholipid scramblase 1 (hPLSCR1) is a 37 kDa multi-compartmental protein, which was initially identified as a Ca-dependent phospholipid translocator upon localizing to the plasma membrane. However, under certain physiological conditions, hPLSCR1 is localized to the nucleus where it interacts with the IP3R1 promoter (IP3R1P) and regulates its expression. In this study, the DNA binding properties of hPLSCR1 and ∆100-hPLSCR1 (N-terminal 100 amino acids deleted from hPLSCR1) were investigated by using a synthetic IP3R1P oligonucleotide and nonspecific scrambled-sequence oligonucleotides. Our results revealed that hPLSCR1 and ∆100-hPLSCR1 were bound to IP3R1P oligos in a 1:1 stoichiometry. In addition, ∆160-hPLSCR1 could not bind to IP3R1P oligonucleotide suggesting that the proposed DNA binding motif is the actual DNA binding motif. Specific binding of hPLSCR1 and ∆100-hPLSCR1 to IP3R1P oligos was demonstrated by fluorescence anisotropy assay. ITC analysis revealed that hPLSCR1 binds to IP3R1P oligos with K = 42.91 ± 0.23 nM. Binding of IP3R1P oligos induces β-sheet formation in hPLSCR1 and increases the thermal stability of hPLSCR1 and ∆100-hPLSCR1. Binding of IP3R1P oligos to hPLSCR1 altered the B-form of the DNA, which was not observed with ∆100-hPLSCR1. Results from this study suggest that (i) ∆100-hPLSCR1 possesses a minimal DNA binding region and (ii) structural alterations of IP3R1P oligo by hPLSCR1 require proline-rich N-terminal region.
Topics: Humans; Phospholipid Transfer Proteins; Phospholipids; Cell Membrane; Protein Domains; Oligonucleotides
PubMed: 36260146
DOI: 10.1007/s00249-022-01621-0 -
ACS Chemical Biology Apr 2024Synaptotagmin-1 (Syt-1) is a calcium sensing protein that is resident in synaptic vesicles. It is well established that Syt-1 is essential for fast and synchronous...
Synaptotagmin-1 (Syt-1) is a calcium sensing protein that is resident in synaptic vesicles. It is well established that Syt-1 is essential for fast and synchronous neurotransmitter release. However, the role of Ca and phospholipid binding in the function of Syt-1, and ultimately in neurotransmitter release, is unclear. Here, we investigate the binding of Ca to Syt-1, first in the absence of lipids, using native mass spectrometry to evaluate individual binding affinities. Syt-1 binds to one Ca with a ∼ 45 μM. Each subsequent binding affinity ( ≥ 2) is successively unfavorable. Given that Syt-1 has been reported to bind anionic phospholipids to modulate the Ca binding affinity, we explored the extent that Ca binding was mediated by selected anionic phospholipid binding. We found that phosphatidylinositol 4,5-bisphosphate (PI(4,5)P) and dioleoylphosphatidylserine (DOPS) positively modulated Ca binding. However, the extent of Syt-1 binding to phosphatidylinositol 3,5-bisphosphate (PI(3,5)P) was reduced with increasing [Ca]. Overall, we find that specific lipids differentially modulate Ca binding. Given that these lipids are enriched in different subcellular compartments and therefore may interact with Syt-1 at different stages of the synaptic vesicle cycle, we propose a regulatory mechanism involving Syt-1, Ca, and anionic phospholipids that may also control some aspects of vesicular exocytosis.
Topics: Calcium; Exocytosis; Neurotransmitter Agents; Phospholipids; Synaptic Transmission; Synaptic Vesicles; Synaptotagmin I; Animals; Rats
PubMed: 38566504
DOI: 10.1021/acschembio.3c00772 -
Trends in Biochemical Sciences Sep 2019Anionic phospholipids are minor but prominent components of the plasma membrane that are necessary for ion channel function. Their persistence in bulk membranes, in... (Review)
Review
Anionic phospholipids are minor but prominent components of the plasma membrane that are necessary for ion channel function. Their persistence in bulk membranes, in particular phosphatidylinositol 4,5-bisphosphate (PIP), initially suggested they act as channel cofactors. However, recent technologies have established an emerging system of nanoscale signaling to ion channels based on lipid compartmentalization (clustering), direct lipid binding, and local lipid dynamics that allow cells to harness lipid heterogeneity to gate ion channels. The new tools to study lipid binding are set to transform our view of the membrane and answer important questions surrounding ion channel-delimited processes such as mechanosensation.
Topics: Humans; Ion Channels; Nanotechnology; Phospholipids
PubMed: 31060927
DOI: 10.1016/j.tibs.2019.04.001 -
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 -
FASEB Journal : Official Publication of... Aug 2023Phosphatidylserine (PS) is a negatively charged phospholipid normally localized to the inner leaflet of the plasma membrane of cells but is externalized onto the cell...
Phosphatidylserine (PS) is a negatively charged phospholipid normally localized to the inner leaflet of the plasma membrane of cells but is externalized onto the cell surface during apoptosis as well as in malignant and infected cells. Consequently, PS may comprise an important molecular target in diagnostics, imaging, and targeted delivery of therapeutic agents. While an array of PS-binding molecules exist, their utility has been limited by their inability to internalize diagnostic or therapeutic payloads. We describe the generation, isolation, characterization, and utility of a PS-binding motif comprised of a carboxylated glutamic acid (GLA) residue domain that both recognizes and binds cell surface-exposed PS, and then unlike other PS-binding molecules is internalized into these cells. Internalization is independent of the traditional endosomal-lysosomal pathway, directly entering the cytosol of the target cell rapidly. We demonstrate that this PS recognition extends to stem cells and that GLA-domain-conjugated probes can be detected upon intravenous administration in animal models of infectious disease and cancer. GLA domain binding and internalization offer new opportunities for specifically targeting cells with surface-exposed PS for imaging and delivery of therapeutics.
Topics: Animals; Phosphatidylserines; Cell Membrane; Phospholipids; Phagocytosis; Neoplasms
PubMed: 37486772
DOI: 10.1096/fj.202201250RRR -
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