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  • 1
    Online Resource
    Online Resource
    Discovery of a lysophospholipid acyltransferase family essential for membrane asymmetry and diversity
    Proceedings of the National Academy of Sciences ; 2008
    In:  Proceedings of the National Academy of Sciences Vol. 105, No. 8 ( 2008-02-26), p. 2830-2835
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 105, No. 8 ( 2008-02-26), p. 2830-2835
    Abstract: All organisms consist of cells that are enclosed by a cell membrane containing bipolar lipids and proteins. Glycerophospholipids are important not only as structural and functional components of cellular membrane but also as precursors of various lipid mediators. Polyunsaturated fatty acids comprising arachidonic acid or eicosapentaenoic acid are located at sn -2 position, but not at sn -1 position of glycerophospholipids in an asymmetrical manner. In addition to the asymmetry, the membrane diversity is important for membrane fluidity and curvature. To explain the asymmetrical distribution of fatty acids, the rapid turnover of sn -2 position was proposed in 1958 by Lands [Lands WE (1958) Metabolism of glycerolipides: A comparison of lecithin and triglyceride synthesis. J Biol Chem 231:883–888]. However, the molecular mechanisms and biological significance of the asymmetry remained unknown. Here, we describe a putative enzyme superfamily consisting mainly of three gene families, which catalyzes the transfer of acyl-CoAs to lysophospholipids to produce different classes of phosph olipids. Among them, we characterized three important enzymes with different substrate specificities and tissue distributions; one, termed lysophosphatidylcholine acyltransferase-3 (a mammalian homologue of Drosophila nessy critical for embryogenesis), prefers arachidonoyl-CoA, and the other two enzymes incorporate oleoyl-CoAs to lysophosphatidylethanolamine and lysophosphatidylserine. Thus, we propose that the membrane diversity is produced by the concerted and overlapped reactions with multiple enzymes that recognize both the polar head group of glycerophospholipids and various acyl-CoAs. Our findings constitute a critical milestone for our understanding about how membrane diversity and asymmetry are established and their biological significance.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0712245105
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2008
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  • 2
    Online Resource
    Online Resource
    IL-1 Receptor Accessory Protein-Like 1 Associated with Mental Retardation and Autism Mediates Synapse Formation by Trans -Synaptic Interaction with Protein Tyrosine Phosphatase δ
    Society for Neuroscience ; 2011
    In:  The Journal of Neuroscience Vol. 31, No. 38 ( 2011-09-21), p. 13485-13499
    Details
    In: The Journal of Neuroscience, Society for Neuroscience, Vol. 31, No. 38 ( 2011-09-21), p. 13485-13499
    Abstract: Mental retardation (MR) and autism are highly heterogeneous neurodevelopmental disorders. IL-1-receptor accessory protein-like 1 (IL1RAPL1) is responsible for nonsyndromic MR and is associated with autism. Thus, the elucidation of the functional role of IL1RAPL1 will contribute to our understanding of the pathogenesis of these mental disorders. Here, we showed that knockdown of endogenous IL1RAPL1 in cultured cortical neurons suppressed the accumulation of punctate staining signals for active zone protein Bassoon and decreased the number of dendritic protrusions. Consistently, the expression of IL1RAPL1 in cultured neurons stimulated the accumulation of Bassoon and spinogenesis. The extracellular domain (ECD) of IL1RAPL1 was required and sufficient for the presynaptic differentiation-inducing activity, while both the ECD and cytoplasmic domain were essential for the spinogenic activity. Notably, the synaptogenic activity of IL1RAPL1 was specific for excitatory synapses. Furthermore, we identified presynaptic protein tyrosine phosphatase (PTP) δ as a major IL1RAPL1–ECD interacting protein by affinity chromatography. IL1RAPL1 interacted selectively with certain forms of PTPδ splice variants carrying mini-exon peptides in Ig-like domains. The synaptogenic activity of IL1RAPL1 was abolished in primary neurons from PTPδ knock-out mice. IL1RAPL1 showed robust synaptogenic activity in vivo when transfected into the cortical neurons of wild-type mice but not in PTPδ knock-out mice. These results suggest that IL1RAPL1 mediates synapse formation through trans -synaptic interaction with PTPδ. Our findings raise an intriguing possibility that the impairment of synapse formation may underlie certain forms of MR and autism as a common pathogenic pathway shared by these mental disorders.
    Type of Medium: Online Resource
    ISSN: 0270-6474 , 1529-2401
    URL: Article
    DOI: 10.1523/JNEUROSCI.2136-11.2011
    Language: English
    Publisher: Society for Neuroscience
    Publication Date: 2011
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    SSG: 12
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  • 3
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    Online Resource
    Intracellular phosphatidylserine is essential for retrograde membrane traffic through endosomes
    Proceedings of the National Academy of Sciences ; 2011
    In:  Proceedings of the National Academy of Sciences Vol. 108, No. 38 ( 2011-09-20), p. 15846-15851
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 108, No. 38 ( 2011-09-20), p. 15846-15851
    Abstract: Phosphatidylserine (PS) is a relatively minor constituent of biological membranes. Despite its low abundance, PS in the plasma membrane (PM) plays key roles in various phenomena such as the coagulation cascade, clearance of apoptotic cells, and recruitment of signaling molecules. PS also localizes in endocytic organelles, but how this relates to its cellular functions remains unknown. Here we report that PS is essential for retrograde membrane traffic at recycling endosomes (REs). PS was most concentrated in REs among intracellular organelles, and evectin-2 (evt-2), a protein of previously unknown function, was targeted to REs by the binding of its pleckstrin homology (PH) domain to PS. X-ray analysis supported the specificity of the binding of PS to the PH domain. Depletion of evt-2 or masking of intracellular PS suppressed membrane traffic from REs to the Golgi. These findings uncover the molecular basis that controls the RE-to-Golgi transport and identify a unique PH domain that specifically recognizes PS but not polyphosphoinositides.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1109101108
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2011
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    TLR4–MD-2 complex is negatively regulated by an endogenous ligand, globotetraosylceramide
    Proceedings of the National Academy of Sciences ; 2013
    In:  Proceedings of the National Academy of Sciences Vol. 110, No. 12 ( 2013-03-19), p. 4714-4719
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 110, No. 12 ( 2013-03-19), p. 4714-4719
    Abstract: Although endogenous ligands for Toll-like receptor (TLR)4–myeloid differentiation factor 2 (MD2) have not been well-understood, we here report that a globo-series glycosphingolipid, globotetraosylceramide (Gb4), attenuates the toxicity of lipopolysaccharides (LPSs) by binding to TLR4–MD-2. Because α1,4-galactosyltransferase (A4galt)-deficient mice lacking globo-series glycosphingolipids showed higher sensitivity to LPS than wild-type mice, we examined mechanisms by which globo-series glycosphingolipids attenuate LPS toxicity. Cultured endothelial cells lacking A4galt showed higher expression of LPS-inducible genes upon LPS treatment. In turn, introduction of A4galt cDNA resulted in the neo expression of Gb4, leading to the reduced expression of LPS-inducible genes. Exogenous Gb4 induced similar effects. As a mechanism for the suppressive effects of Gb4 on LPS signals, specific binding of Gb4 to the LPS receptor TLR4–MD-2 was demonstrated by coprecipitation of Gb4 with recombinant MD-2 and by native PAGE. A docking model also supported these data. Taken together with colocalization of TLR4–MD-2 with Gb4 in lipid rafts after LPS stimulation, it was suggested that Gb4 competes with LPS for binding to TLR4–MD-2. Finally, administration of Gb4 significantly protected mice from LPS-elicited mortality. These results suggest that Gb4 is an endogenous ligand for TLR4–MD-2 and is capable of attenuating LPS toxicity, indicating the possibility for its therapeutic application in endotoxin shock.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1218508110
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2013
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Peroxisome dependency of alkyl-containing GPI-anchor biosynthesis in the endoplasmic reticulum
    Proceedings of the National Academy of Sciences ; 2009
    In:  Proceedings of the National Academy of Sciences Vol. 106, No. 42 ( 2009-10-20), p. 17711-17716
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 42 ( 2009-10-20), p. 17711-17716
    Abstract: Glycosylphosphatidylinositol-anchored proteins (GPI-APs) play various roles in cell–cell and cell–environment interactions. GPI is synthesized in the endoplasmic reticulum (ER) from phosphatidylinositol (PI) through step-wise reactions including transfers of monosaccharides and preassembled GPI is transferred en bloc to proteins. Cellular PI contains mostly diacyl glycerol and unsaturated fatty acid in the sn-2 position, whereas mammalian GPI-APs have mainly 1-alkyl-2-acyl PI and almost exclusively stearic acid, a saturated chain, at the sn-2 position. The latter characteristic is the result of fatty acid remodeling occurring in the Golgi, generating GPI-anchors compatible with raft membrane. The former characteristic is the result of diacyl to alkyl-acyl change occurring in the third GPI intermediate, glucosaminyl-inositolacylated-PI (GlcN-acyl-PI). Here we investigated the origin of the sn-1 alkyl-chain in GPI-APs. Using cell lines defective in the peroxisomal alkyl-phospholipid biosynthetic pathway, we demonstrated that generation of alkyl-containing GPI is dependent upon the peroxisomal pathway. We further demonstrated that in cells defective in the peroxisome pathway, the chain composition of the diacyl glycerol moiety in GlcN-acyl-PI is different from those in the first intermediate N-acetylglucosaminyl-PI and cellular PI, indicating that not only diacyl to alkyl-acyl change but also diacyl to diacyl change occurs in GlcN-acyl-PI. We therefore propose a biosynthetic step within GlcN-acyl-PI in which the diacyl glycerol (or diacyl phosphatidic acid) part is replaced by diradyl glycerol (or diradyl phosphatidic acid). These results highlight cooperation of three organelles, the ER, the Golgi, and the peroxisome, in the generation of the lipid portion of GPI-APs.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0904762106
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2009
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    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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