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Journal of Colloid and Interface Science Jan 2023Inositol phospholipids are well known to form clusters in the cytoplasmic leaflet of the plasma membrane that are responsible for the interaction and recruitment of...
HYPOTHESIS
Inositol phospholipids are well known to form clusters in the cytoplasmic leaflet of the plasma membrane that are responsible for the interaction and recruitment of proteins involved in key biological processes like endocytosis, ion channel activation and secondary messenger production. Although their phosphorylated inositol ring headgroup plays an important role in protein binding, its orientation with respect to the plane of the membrane and its lateral packing density has not been previously described experimentally.
EXPERIMENTS
Here, we study phosphatidylinositol 4,5-bisphosphate (PIP) planar model membranes in the form of Langmuir monolayers by surface pressure-area isotherms, Brewster angle microscopy and neutron reflectometry to elucidate the relation between lateral (in-plane) and perpendicular (out-of-plane) molecular organization of PIP.
FINDINGS
Different surface areas were explored through monolayer compression, allowing us to correlate the formation of transient PIP clusters with the change in orientation of the inositol-biphosphate headgroup, which was experimentally determined by neutron reflectometry.
Topics: Phosphatidylinositols; Phosphatidylinositol 4,5-Diphosphate; Inositol Phosphates; Cell Membrane; Protein Binding
PubMed: 36195018
DOI: 10.1016/j.jcis.2022.09.095 -
Journal of the American Society For... Nov 2000Structural characterization of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PI-4P), and phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2) by...
Characterization of phosphatidylinositol, phosphatidylinositol-4-phosphate, and phosphatidylinositol-4,5-bisphosphate by electrospray ionization tandem mass spectrometry: a mechanistic study.
Structural characterization of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PI-4P), and phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2) by collisionally activated dissociation (CAD) tandem mass spectrometry with electrospray ionization is described. In negative ion mode, the major fragmentation pathways under low energy CAD for PI arise from neutral loss of free fatty acid substituents ([M - H - RxCO2H]-) and neutral loss of the corresponding ketenes ([M - H - R'xCH=C=O]-), followed by consecutive loss of the inositol head group. The intensities of the ions arising from neutral loss of the sn-2 substituent as a free fatty acid ([M - H - R2CO2H]-) or as a ketene ([M - H - R'2CH=C=O] ) are greater than those of ions reflecting corresponding losses of the sn-1 substutient. This is consistent with our recent finding that ions reflecting those losses arise from charge-driven processes that occur preferentially at the sn-2 position. These features permit assignment of the position of the fatty acid substituents on the glycerol backbone. Nucleophilic attack of the anionic phosphate onto the C-1 or the C-2 of the glycerol to which the fatty acids attached expels sn-1 (R1CO2-) or sn-2 (R2CO2-) carboxylate anion, respectively. This pathway is sterically more favorable at sn-2 than at sn-1. However, further dissociations of [M - H - RxCO2H - inositol] , [M - H - RxCO2H]-, and [M - H - RxCH=C=O]- precursor ions also yield RxCO2- ions, whose abundance are affected by the collision energy applied. Therefore, relative intensities of the RxCO2- ions in the spectrum do not reflect their positions on the glycerol backbone and determination of their regiospecificities based on their ion intensities is not reliable. The spectra also contain specific ions at m/z 315, 279, 259, 241, and 223, reflecting the inositol head group. The last three ions are also observed in the tandem spectra of the [M - H]- ions of phosphatidylinositol monophosphate (PI-P) and phosphatidylinositol bisphosphate (PI-P2), in addition to the ions at m/z 321 and 303, reflecting the doubly phosphorylated inositol ions. The PI-P2 also contains unique ions at m/z 401 and 383 that reflect the triply phosphorylated inositol ions. The [M - H]- ions of PI-P and PI-P2 undergo fragmentation pathways similar to that of PI upon CAD. However, the doubly charged ([M - 2H]2-) molecular ions undergo fragmentation pathways that are typical of the [M - H]- ions of glycerophosphoethanolamine, which are basic. These results suggest that the further deprotonated gaseous [M - 2H]2 ions of PI-P and PI-P2 are basic precursors.
Topics: Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositol Phosphates; Phosphatidylinositols; Spectrometry, Mass, Electrospray Ionization
PubMed: 11073262
DOI: 10.1016/S1044-0305(00)00172-0 -
[Metabolism of phosphatidylinositol and the mechanism of signal transduction of membrane receptors].Nihon Naibunpi Gakkai Zasshi Dec 1987
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Frontiers in Bioscience : a Journal and... May 2008Nature has created an immense combinatorial and structural heterogeneity among lipids. It is becoming increasingly accepted that the vast range of unique chemical... (Review)
Review
Nature has created an immense combinatorial and structural heterogeneity among lipids. It is becoming increasingly accepted that the vast range of unique chemical entities encodes for distinct functions within biological systems. A unique group of lipids which stands out in terms of diversity as well as biological activity are inositol-containing lipids. The most well characterized inositol lipids are the phosphoinositides, phosphorylated derivatives of glycerophosphoinositol, which play a wide variety of cellular roles in many eukaryotic cells. Less well understood are ceramides containing inositol in fungi, and inositol glycolipids in pathogens. Here we review biochemical aspects of inositol-containing lipids with a focus on novel analytical procedures for their characterization.
Topics: Cell Membrane; Endoplasmic Reticulum; Glycosylphosphatidylinositols; Humans; Membrane Lipids; Phosphatidylinositol Phosphates; Phosphatidylinositols; Sphingolipids
PubMed: 18508430
DOI: 10.2741/2923 -
Bioorganic & Medicinal Chemistry Nov 2006Phosphatidylinositol mannosides (PIMs) isolated from mycobacteria have been identified as an important class of glycolipids with significant immune modulating...
Phosphatidylinositol mannosides (PIMs) isolated from mycobacteria have been identified as an important class of glycolipids with significant immune modulating properties. We present here the syntheses of phosphatidylinositol dimannoside (PIM2, 1) and phosphatidylinositol tetramannoside (PIM4, 2) and evaluate their adjuvant properties in a transgenic mouse model. The key step in the synthetic methodology for the synthesis of 2 relies on the selective glycosylation of diol 3 with mannosyl donor 11. Both synthetic PIMs were effective at enhancing IFN-gamma when given as adjuvants with a model antigen, with PIM2 being the more active. These data suggest that in this assay the PIM core structure is responsible for the observed biological activity.
Topics: Adjuvants, Immunologic; Animals; Carbohydrate Conformation; Mannosides; Mice; Mice, Inbred C57BL; Ovalbumin; Phosphatidylinositols
PubMed: 16876422
DOI: 10.1016/j.bmc.2006.07.003 -
Biochemistry and Cell Biology =... Dec 2016Phosphatidylinositol transfer proteins (PITPs) are believed to be lipid transfer proteins because of their ability to transfer either phosphatidylinositol (PI) or...
Phosphatidylinositol transfer proteins (PITPs) are believed to be lipid transfer proteins because of their ability to transfer either phosphatidylinositol (PI) or phosphatidylcholine (PC) between membrane compartments, in vitro. However, the detailed mechanism of this transfer process is not fully established. To further understand the transfer mechanism of PITPs we examined the interaction of PITPs with membranes using dual polarization interferometry (DPI), which measures protein binding affinity on a flat immobilized lipid surface. In addition, a fluorescence resonance energy transfer (FRET)-based assay was also employed to monitor how quickly PITPs transfer their ligands to lipid vesicles. DPI analysis revealed that PITPβ had a higher affinity to membranes compared with PITPα. Furthermore, the FRET-based transfer assay revealed that PITPβ has a higher ligand transfer rate compared with PITPα. However, both PITPα and PITPβ demonstrated a preference for highly curved membrane surfaces during ligand transfer. In other words, ligand transfer rate was higher when the accepting vesicles were highly curved.
Topics: Cell Membrane; Fluorescence Resonance Energy Transfer; Humans; Ligands; Lipids; Mutation; Phosphatidylinositols; Phospholipid Transfer Proteins; Protein Binding; Protein Conformation
PubMed: 27783542
DOI: 10.1139/bcb-2015-0152 -
Carbohydrate Research Jun 2004A number of deoxyfluoro cyclitols have been synthesized and evaluated as probes of the phosphatidylinositol pathway (PtdIns pathway), most notably... (Review)
Review
A number of deoxyfluoro cyclitols have been synthesized and evaluated as probes of the phosphatidylinositol pathway (PtdIns pathway), most notably 5-deoxy-5-fluoro-myo-inositol, which is incorporated into the pathway at about 25% the level of myo-inositol itself. Unfortunately, none of the cyclitols have proved effective in limiting cell proliferation, as the cells are able to 'synthesize around' the fraudulent cyclitols using natural myo-inositol as substrate. Inhibitors for 3-phosphatidylinositol kinase, which has importance in a number of pathological conditions, including cancer, have been intensively investigated. 3-Deoxy-3-fluoro-myo-inositol is incorporated into the PtdIns pathway; however, only related phosphatidyl derivatives, for example, a methyl ether derivative of the 3-deoxy inositol, showed significant antiproliferative activity. Synthesis of the deoxyfluoro analogues most often has been accomplished by DAST fluoro-de-hydroxylation of the appropriate cyclitol, generally leading to products of inversion.
Topics: Animals; Fluorine Compounds; Inositol; Molecular Structure; Phosphatidylinositols; Structure-Activity Relationship
PubMed: 15183732
DOI: 10.1016/j.carres.2004.03.030 -
Sheng Li Ke Xue Jin Zhan [Progress in... Oct 1987
Review
Topics: Animals; Humans; Oncogene Proteins, Viral; Phosphatidylinositols; Proto-Oncogene Proteins
PubMed: 3330866
DOI: No ID Found -
Current Opinion in Cell Biology Aug 2002Phosphoinositides act as precursors of second messengers and membrane ligands for protein modules. Specific lipid kinases and phosphatases are located and differentially... (Review)
Review
Phosphoinositides act as precursors of second messengers and membrane ligands for protein modules. Specific lipid kinases and phosphatases are located and differentially regulated in cell organelles, generating a non-uniform distribution of phosphoinositides. Although it is not clear whether and how the phosphoinositide pools are integrated, it is certain that they locally control fundamental processes, including membrane trafficking. This applies to the Golgi complex, where a direct, central role of the phosphatidylinositol 4,5-bisphosphate precursor phosphatidylinositol 4-phosphate has recently been reported.
Topics: Animals; Golgi Apparatus; Humans; Models, Biological; Phosphatidylinositol 3-Kinases; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositol Phosphates; Phosphatidylinositols; Yeasts
PubMed: 12383794
DOI: 10.1016/s0955-0674(02)00357-5 -
Chemical synthesis and immunosuppressive activity of dipalmitoyl phosphatidylinositol hexamannoside.The Journal of Organic Chemistry Jun 2011Phosphatidylinositol mannosides (PIMs) isolated from mycobacteria have been identified as an important class of phosphoglycolipids with significant immune-modulating...
Phosphatidylinositol mannosides (PIMs) isolated from mycobacteria have been identified as an important class of phosphoglycolipids with significant immune-modulating properties. We present here the synthesis of dipalmitoyl phosphatidylinositol hexamannoside (PIM(6)) 1 and the first reported functional biology of a synthetic PIM(6). Key steps in the synthetic protocol included the selective glycosylation of an inositol 2,6-diol with a suitably protected mannosyl donor and construction of the glycan core utilizing a [3 + 4] thio-glycosylation strategy. The target 1 was purified by reverse phase chromatography and characterized by standard spectroscopic methods, HPLC, and chemical modification by deacylation to dPIM(6). The (1)H NMR spectrum of synthetic dPIM(6) obtained from 1 matched that of dPIM(6) obtained from nature. PIM(6) (1) exhibited dendritic cell-dependent suppression of CD8(+) T cell expansion in a human mixed lymphocyte reaction consistent with the well established immunosuppressive activity of whole mycobacteria.
Topics: Cell Differentiation; Cell Proliferation; Cells, Cultured; Humans; Lymphocyte Culture Test, Mixed; Molecular Structure; Phosphatidylinositols; T-Lymphocytes
PubMed: 21574597
DOI: 10.1021/jo200588u