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31.
Tiziana Vigliarolo Lucrezia Guida Enrico Millo Chiara Fresia Emilia Turco Antonio De Flora Elena Zocchi 《The Journal of biological chemistry》2015,290(21):13042-13052
Abscisic acid (ABA) is a plant hormone involved in the response to environmental stress. Recently, ABA has been shown to be present and active also in mammals, where it stimulates the functional activity of innate immune cells, of mesenchymal and hemopoietic stem cells, and insulin-releasing pancreatic β-cells. LANCL2, the ABA receptor in mammalian cells, is a peripheral membrane protein that localizes at the intracellular side of the plasma membrane. Here we investigated the mechanism enabling ABA transport across the plasmamembrane of human red blood cells (RBC). Both influx and efflux of [3H]ABA occur across intact RBC, as detected by radiometric and chromatographic methods. ABA binds specifically to Band 3 (the RBC anion transporter), as determined by labeling of RBC membranes with biotinylated ABA. Proteoliposomes reconstituted with human purified Band 3 transport [3H]ABA and [35S]sulfate, and ABA transport is sensitive to the specific Band 3 inhibitor 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid. Once inside RBC, ABA stimulates ATP release through the LANCL2-mediated activation of adenylate cyclase. As ATP released from RBC is known to exert a vasodilator response, these results suggest a role for plasma ABA in the regulation of vascular tone. 相似文献
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A covalently bound photoisomerizable agonist. Comparison with reversibly bound agonists at electrophorus electroplaques 下载免费PDF全文
HA Lester ME Krouse MM Nass NH Wassermann BF Erlanger 《The Journal of general physiology》1980,75(2):207-232
After disulphide bonds are reduced with dithiothreitol, trans-3- (α-bromomethyl)-3’-[α- (trimethylammonium)methyl]azobenzene (trans-QBr) alkylates a sulfhydryl group on receptors. The membrane conductance induced by this “tethered agonist” shares many properties with that induced by reversible agonists. Equilibrium conductance increases as the membrane potential is made more negative; the voltage sensitivity resembles that seen with 50 [mu]M carbachol. Voltage- jump relaxations follow an exponential time-course; the rate constants are about twice as large as those seen with 50 μM carbachol and have the same voltage and temperature sensitivity. With reversible agonists, the rate of channel opening increases with the frequency of agonist-receptor collisions: with tethered trans-Qbr, this rate depends only on intramolecular events. In comparison to the conductance induced by reversible agonists, the QBr-induced conductance is at least 10-fold less sensitive to competitive blockade by tubocurarine and roughly as sensitive to “open-channel blockade” bu QX-222. Light-flash experiments with tethered QBr resemble those with the reversible photoisomerizable agonist, 3,3’,bis-[α-(trimethylammonium)methyl]azobenzene (Bis-Q): the conductance is increased by cis {arrow} trans photoisomerizations and decreased by trans {arrow} cis photoisomerizations. As with Bis-Q, ligh-flash relaxations have the same rate constant as voltage-jump relaxations. Receptors with tethered trans isomer. By comparing the agonist-induced conductance with the cis/tans ratio, we conclude that each channel’s activation is determined by the configuration of a single tethered QBr molecule. The QBr-induced conductance shows slow decreases (time constant, several hundred milliseconds), which can be partially reversed by flashes. The similarities suggest that the same rate-limiting step governs the opening and closing of channels for both reversible and tethered agonists. Therefore, this step is probably not the initial encounter between agonist and receptor molecules. 相似文献
35.
Soares RP Cardoso TL Barron T Araújo MS Pimenta PF Turco SJ 《International journal for parasitology》2005,35(3):245-253
During metacyclogenesis of Leishmania in its sand fly vector, the parasite differentiates from a noninfective, procyclic form to an infective, metacyclic form, a process characterised by morphological changes of the parasite and also biochemical transformations in its major surface lipophosphoglycan (LPG). This lipid-anchored polysaccharide is polymorphic among species with variations in sugars that branch off the conserved Gal(beta1,4)Man(alpha1)-PO4 backbone of repeat units and the oligosaccharide cap. Lipophosphoglycan has been implicated as an adhesion molecule that mediates the interaction with the midgut epithelium of the sand fly in the subgenus Leishmania. This paper describes the LPG structure for the first time in a species from the subgenus Viannia, Leishmania (Viannia) braziliensis. The LPG from the procyclic form of L. braziliensis was found to lack side chain sugar substitutions. In contrast to other species from the subgenus Leishmania, metacyclic forms of L. braziliensis makes less LPG and add 1-2 (beta1-3) glucose residues that branch off the disaccharide-phosphate repeat units of LPG. Thus, this represents a novel mechanism in the regulation of LPG structure during metacyclogenesis. 相似文献
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Coelho-Finamore JM Freitas VC Assis RR Melo MN Novozhilova N Secundino NF Pimenta PF Turco SJ Soares RP 《International journal for parasitology》2011,41(3-4):333-342
Interspecies variations in lipophosphoglycan (LPG) have been the focus of intense study over the years due its role in specificity during sand fly-Leishmania interaction. This cell surface glycoconjugate is highly polymorphic among species with variations in sugars that branch off the conserved Gal(β1,4)Man(α1)-PO(4) backbone of repeat units. However, the degree of intraspecies polymorphism in LPG of Leishmania infantum (syn. Leishmania chagasi) is not known. In this study, intraspecific variation in the repeat units of LPG was evaluated in 16 strains of L. infantum from Brazil, France, Algeria and Tunisia. The structural polymorphism in the L. infantum LPG repeat units was relatively slight and consisted of three types: type I does not have side chains; type II has one β-glucose residue that branches off the disaccharide-phosphate repeat units and type III has up to three glucose residues (oligo-glucosylated). The significance of these modifications was investigated during in vivo interaction of L. infantum with Lutzomyia longipalpis, and in vitro interaction of the parasites and respective LPGs with murine macrophages. There were no consequential differences in the parasite densities in sand fly midguts infected with Leishmania strains exhibiting type I, II and III LPGs. However, higher nitric oxide production was observed in macrophages exposed to glucosylated type II LPG. 相似文献
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Annemarie MM Vlaar Angela EP Bouwmans Marinus JPG van Kroonenburgh Werner H Mess Selma C Tromp Piet GWM Wuisman Alfons GH Kessels Ania Winogrodzka Wim EJ Weber 《BMC neurology》2007,7(1):28
Background
Parkinson's disease (PD) is the second most common neurodegenerative disorder. As there is no definitive diagnostic test, its diagnosis is based on clinical criteria. Recently transcranial duplex scanning (TCD) of the substantia nigra in the brainstem has been proposed as an instrument to diagnose PD. We and others have found that TCD scanning of substantia nigra duplex is a relatively accurate diagnostic instrument in patients with parkinsonian symptoms. However, all studies on TCD so far have involved well-defined, later-stage PD patients, which will obviously lead to an overestimate of the diagnostic accuracy of TCD. 相似文献38.
Dobson DE Scholtes LD Valdez KE Sullivan DR Mengeling BJ Cilmi S Turco SJ Beverley SM 《The Journal of biological chemistry》2003,278(18):15523-15531
Lipophosphoglycan (LPG) is an abundant surface molecule that plays key roles in the infectious cycle of Leishmania major. The dominant feature of LPG is a polymer of phosphoglycan (PG) (6Galbeta1,4Manalpha1-PO(4)) repeating units. In L. major these are extensively substituted with Gal(beta1,3) side chains, which are required for binding to midgut lectins and survival. We utilized evolutionary polymorphisms in LPG structure and cross-species transfections to recover genes encoding the LPG side chain beta1,3-galactosyltransferases (betaGalTs). A dispersed family of six SCG genes was recovered, whose predicted proteins exhibited characteristics of eukaryotic GalTs. At least four of these proteins showed significant LPG side chain betaGalT activity; SCG3 exhibited initiating GalT activity whereas SCG2 showed both initiating and elongating GalT activity. However, the activity of SCG2 was context-dependent, being largely silent in its normal genomic milieu, and different strains show considerable variation in the extent of LPG galactosylation. Thus the L. major genome encodes a family of SCGs with varying specificity and activity, and we propose that strain-specific LPG galactosylation patterns reflect differences in their expression. 相似文献
39.
Lipophosphoglycan (LPG) is the predominant surface glycoconjugateof Leishmania promastigotes and consists of a capped polymerof Gal(ß1,4)Man( 相似文献
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