- Email: [email protected]
Membrane microdomains in regulated secretion in endothelial cells
S16
Abstracts / Chemistry and Physics of Lipids 164S (2011) S15–S17
expressed, the annexin protein family function as intracellular Ca2+ sensors. Most cells contain multiple annexins, which interact with distinct plasma membrane regions promoting membrane segregation and membrane fusion. Recent results have implicated a role for the annexins in plasma membrane repair. An injury-induced Ca2+ elevation triggers the translocation of annexins from the cytoplasm to the plasma membrane, where they reseal the injury. According to their individual Ca2+ profile, highly Ca2+ sensitive annexins will translocate preferentially and act as a first line of defense, whereas annexins with a lower Ca2+ sensitivity will be used if the injury persists and/or early attempts at resealing fail. Thus, multiple annexins within one cell allow a graded response to membrane injury, discerning between a limited and a sustained lesion. doi:10.1016/j.chemphyslip.2011.05.057 PL 20 Membrane microdomains in regulated secretion in endothelial cells Volker Gerke Institute of Medical Biochemistry, University of Muenster, Germany Endothelial cells regulate thrombosis, haemostasis and local inflammatory responses by supplying the vasculature with a number of factors that include the pro-coagulant and pro-inflammatory von-Willebrand factor (vWF) and P-selectin. Both proteins are stored in large organelles, the Weibel-Palade bodies (WPB) and can be secreted in a Ca2+ -regulated manner following endothelial activation. The molecular mechanisms underlying acute WPB exocytosis are far from being understood although a number of endothelial proteins involved in this process have been described. These include members of the SNARE and annexin families that most likely participate in docking of WPB at the plasma membrane and initiating the actual fusion event. Preliminary evidence also indicates that WPB fusion Is accompanied by changes in the plasma membrane lipid composition with certain phospholipids facilitating agonist-triggered WPB secretion. Recent progress towards the identification of the endothelial machinery that supports WPB exocytosis will be discussed. doi:10.1016/j.chemphyslip.2011.05.058 SO 17 Sphingomyelin synthase 2 is responsible for obesity and lipid droplet formation in liver and is a novel regulator of membrane microdomain Susumu Mitsutake 1,∗ , Hazuki Yokota 1 , Kota Zama 1 , Tetsuya Yoshida 2 , Tadashi Yamashita 3 , Toshiro Okazaki 4 , Ken Watanabe 5 , Yasuyuki Igarashi 1 1
Department of Biofunctional Chemistry, Hokkaido University, Japan Department of Developmental Biotechnology, Faculty of Advanced Life Science, Hokkaido University, Japan 3 Shionogi Innovation Center for Drug Discovery, Shionogi & Co., Ltd., Japan 4 Department of Clinical Laboratory, Medicine/Hematology, Faculty of Medicine, Tottori University, Japan 5 Department of Bone and Joint Disease, National Center for Geriatrics and Geriatrics and Gerontology, Obu, Japan Sphingomyelin (SM) is a major phospholipid in the plasma membrane, and has an important role in the formation of membrane lipid microdomains. Sphingomyelin synthase SMS has two isoform, SMS1 and SMS2. In this study, we investigated the physio2
logical function of SMS2 using SMS2-knockout mice, and found that SMS2 deficiency prevents high fat diet-induced obesity and insulin resistance. Interestingly, in the liver of SMS2-knockout mice, large and matured lipid droplets were scarcely observed, suggesting that SMS2 is involved in lipid droplet formation. Additionally, we found that SMS2 exists in lipid microdomains and partially interacts with the scavenger receptor CD36/FAT and with caveolin 1, a scaffolding protein of caveolae. Since CD36/FAT and caveolin 1 exist in lipid microdomains and are coordinately involved in lipid droplet formation, SMS2 is implicated in modulation of the SM in lipid microdomains, resulting in the regulation of CD36/FAT and caveolae. Furthermore, we demonstrated that SMS2 could convert ceramide produced in the outer leaflet of the plasma membrane. Our findings demonstrate the novel and dynamic regulation of lipid microdomains via conformational changes in lipids on the plasma membrane by SMS2. doi:10.1016/j.chemphyslip.2011.05.059 SO 18 A novel bioactive lipid, Lyso-phosphatidylglucoside as repulsive axon guidance cue in the developing spinal cord Yoshio Hirabayashi 1,∗ , Adam Guy 2 , Yasuko Nagatsuka 1 , Peter Greimel 3 , Takuji Nabetani 1 , Mariko Inoue 2 , Asuka Nakata 2 , Noriko Ooashi 2 , Hiroyuki Kamiguchi 2 1 Laboratory for Molecular Membrane Neuroscience, RIKEN BSI, Wako City, Saitama, Japan 2 Laboratory for Neuronal Growth Mechanisms, RIKEN BSI, Wako City, Saitama, Japan 3 RIKEN ASI, Wako City, Saitama, Japan There are three distinct lipids modified with glucose in mammals: glucosylceramide, cholesteryl--d-glucoside, and phosphatidyl--d-glucoside (PtdGlc). PtdGlc is the most recently discovered glycolipid as very minor component in fetal rat brains. Importantly, PtdGlc consists solely of saturated fatty acyl chains: C18:0 at sn-1 and C20:0 at the sn-2 position of the glycerol backbone, denoting its localization in lipid rafts (Nagatsuka et al., 2003, 2006). PtdGlc-enriched lipid rafts are present in cells of astroglial lineage in developing mouse CNS and that they are potentially involved in astrogliogenesis in mouse cerebral cortex by physiologically coupling to EGFRs during late embryonic stages of development (Kinoshita et al., 2009). The lipid was also found in the adult neural stem cells (NSCs)/precursor cells (NPCs) in a postnatal neurogenic region, subventricular zone, suggesting that PtdGlc is a novel marker of adult NSCs (Kaneko et al., 2011). Here, we have identified a water-soluble derivative of PtdGlc, lyso-PtdGlc as a potent axon chemo-repellent molecule specific for NGF-dependent (TrkA) but not NT3-dependent (TrkC) chick DRG neurons. Loss-of-function of lyso-PtdGlc by injecting anti-lysoPtdGlc in vivo in the developing spinal cord causes abnormal axon projection in TrkA-neuron specific manner. Our study demonstrates that lyso-PtdGlc released from radial glia plays a key role in sorting and patterning of the two major neurons in the developing spinal cord.
References Kaneko, J., et al., 2011. J. Neurochem. 116, 840–844. Kinoshita, M.O., et al., 2009. Biochem. J. 419, 565–575. Nagatsuka, Y., et al., 2003. Proc. Natl. Acad. Sci. U.S.A. 100, 7454–7459. Nagatsuka, Y., et al., 2006. Biochemistry 45, 8742–8750.
doi:10.1016/j.chemphyslip.2011.05.060
Abstracts / Chemistry and Physics of Lipids 164S (2011) S15–S17
expressed, the annexin protein family function as intracellular Ca2+ sensors. Most cells contain multiple annexins, which interact with distinct plasma membrane regions promoting membrane segregation and membrane fusion. Recent results have implicated a role for the annexins in plasma membrane repair. An injury-induced Ca2+ elevation triggers the translocation of annexins from the cytoplasm to the plasma membrane, where they reseal the injury. According to their individual Ca2+ profile, highly Ca2+ sensitive annexins will translocate preferentially and act as a first line of defense, whereas annexins with a lower Ca2+ sensitivity will be used if the injury persists and/or early attempts at resealing fail. Thus, multiple annexins within one cell allow a graded response to membrane injury, discerning between a limited and a sustained lesion. doi:10.1016/j.chemphyslip.2011.05.057 PL 20 Membrane microdomains in regulated secretion in endothelial cells Volker Gerke Institute of Medical Biochemistry, University of Muenster, Germany Endothelial cells regulate thrombosis, haemostasis and local inflammatory responses by supplying the vasculature with a number of factors that include the pro-coagulant and pro-inflammatory von-Willebrand factor (vWF) and P-selectin. Both proteins are stored in large organelles, the Weibel-Palade bodies (WPB) and can be secreted in a Ca2+ -regulated manner following endothelial activation. The molecular mechanisms underlying acute WPB exocytosis are far from being understood although a number of endothelial proteins involved in this process have been described. These include members of the SNARE and annexin families that most likely participate in docking of WPB at the plasma membrane and initiating the actual fusion event. Preliminary evidence also indicates that WPB fusion Is accompanied by changes in the plasma membrane lipid composition with certain phospholipids facilitating agonist-triggered WPB secretion. Recent progress towards the identification of the endothelial machinery that supports WPB exocytosis will be discussed. doi:10.1016/j.chemphyslip.2011.05.058 SO 17 Sphingomyelin synthase 2 is responsible for obesity and lipid droplet formation in liver and is a novel regulator of membrane microdomain Susumu Mitsutake 1,∗ , Hazuki Yokota 1 , Kota Zama 1 , Tetsuya Yoshida 2 , Tadashi Yamashita 3 , Toshiro Okazaki 4 , Ken Watanabe 5 , Yasuyuki Igarashi 1 1
Department of Biofunctional Chemistry, Hokkaido University, Japan Department of Developmental Biotechnology, Faculty of Advanced Life Science, Hokkaido University, Japan 3 Shionogi Innovation Center for Drug Discovery, Shionogi & Co., Ltd., Japan 4 Department of Clinical Laboratory, Medicine/Hematology, Faculty of Medicine, Tottori University, Japan 5 Department of Bone and Joint Disease, National Center for Geriatrics and Geriatrics and Gerontology, Obu, Japan Sphingomyelin (SM) is a major phospholipid in the plasma membrane, and has an important role in the formation of membrane lipid microdomains. Sphingomyelin synthase SMS has two isoform, SMS1 and SMS2. In this study, we investigated the physio2
logical function of SMS2 using SMS2-knockout mice, and found that SMS2 deficiency prevents high fat diet-induced obesity and insulin resistance. Interestingly, in the liver of SMS2-knockout mice, large and matured lipid droplets were scarcely observed, suggesting that SMS2 is involved in lipid droplet formation. Additionally, we found that SMS2 exists in lipid microdomains and partially interacts with the scavenger receptor CD36/FAT and with caveolin 1, a scaffolding protein of caveolae. Since CD36/FAT and caveolin 1 exist in lipid microdomains and are coordinately involved in lipid droplet formation, SMS2 is implicated in modulation of the SM in lipid microdomains, resulting in the regulation of CD36/FAT and caveolae. Furthermore, we demonstrated that SMS2 could convert ceramide produced in the outer leaflet of the plasma membrane. Our findings demonstrate the novel and dynamic regulation of lipid microdomains via conformational changes in lipids on the plasma membrane by SMS2. doi:10.1016/j.chemphyslip.2011.05.059 SO 18 A novel bioactive lipid, Lyso-phosphatidylglucoside as repulsive axon guidance cue in the developing spinal cord Yoshio Hirabayashi 1,∗ , Adam Guy 2 , Yasuko Nagatsuka 1 , Peter Greimel 3 , Takuji Nabetani 1 , Mariko Inoue 2 , Asuka Nakata 2 , Noriko Ooashi 2 , Hiroyuki Kamiguchi 2 1 Laboratory for Molecular Membrane Neuroscience, RIKEN BSI, Wako City, Saitama, Japan 2 Laboratory for Neuronal Growth Mechanisms, RIKEN BSI, Wako City, Saitama, Japan 3 RIKEN ASI, Wako City, Saitama, Japan There are three distinct lipids modified with glucose in mammals: glucosylceramide, cholesteryl--d-glucoside, and phosphatidyl--d-glucoside (PtdGlc). PtdGlc is the most recently discovered glycolipid as very minor component in fetal rat brains. Importantly, PtdGlc consists solely of saturated fatty acyl chains: C18:0 at sn-1 and C20:0 at the sn-2 position of the glycerol backbone, denoting its localization in lipid rafts (Nagatsuka et al., 2003, 2006). PtdGlc-enriched lipid rafts are present in cells of astroglial lineage in developing mouse CNS and that they are potentially involved in astrogliogenesis in mouse cerebral cortex by physiologically coupling to EGFRs during late embryonic stages of development (Kinoshita et al., 2009). The lipid was also found in the adult neural stem cells (NSCs)/precursor cells (NPCs) in a postnatal neurogenic region, subventricular zone, suggesting that PtdGlc is a novel marker of adult NSCs (Kaneko et al., 2011). Here, we have identified a water-soluble derivative of PtdGlc, lyso-PtdGlc as a potent axon chemo-repellent molecule specific for NGF-dependent (TrkA) but not NT3-dependent (TrkC) chick DRG neurons. Loss-of-function of lyso-PtdGlc by injecting anti-lysoPtdGlc in vivo in the developing spinal cord causes abnormal axon projection in TrkA-neuron specific manner. Our study demonstrates that lyso-PtdGlc released from radial glia plays a key role in sorting and patterning of the two major neurons in the developing spinal cord.
References Kaneko, J., et al., 2011. J. Neurochem. 116, 840–844. Kinoshita, M.O., et al., 2009. Biochem. J. 419, 565–575. Nagatsuka, Y., et al., 2003. Proc. Natl. Acad. Sci. U.S.A. 100, 7454–7459. Nagatsuka, Y., et al., 2006. Biochemistry 45, 8742–8750.
doi:10.1016/j.chemphyslip.2011.05.060