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Okuda T, Osawa C, Yamada H, Hayashi K, Nishikawa S, Ushio T, Kubo Y, Satou M, Ogawa H, Haga T. Transmembrane topology and oligomeric structure of the high-affinity choline transporter. J Biol Chem 2012; 287:42826-34. [PMID: 23132865 DOI: 10.1074/jbc.m112.405027] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The high-affinity choline transporter CHT1 mediates choline uptake essential for acetylcholine synthesis in cholinergic nerve terminals. CHT1 belongs to the Na(+)/glucose cotransporter family (SLC5), which is postulated to have a common 13-transmembrane domain core; however, no direct experimental evidence for CHT1 transmembrane topology has yet been reported. We examined the transmembrane topology of human CHT1 using cysteine-scanning analysis. Single cysteine residues were introduced into the putative extra- and intracellular loops and probed for external accessibility for labeling with a membrane-impermeable, sulfhydryl-specific biotinylating reagent in intact cells expressing these mutants. The results provide experimental evidence for a topological model of a 13-transmembrane domain protein with an extracellular amino terminus and an intracellular carboxyl terminus. We also constructed a three-dimensional homology model of CHT1 based on the crystal structure of the bacterial Na(+)/galactose cotransporter, which supports our conclusion of CHT1 transmembrane topology. Furthermore, we examined whether CHT1 exists as a monomer or oligomer. Chemical cross-linking induces the formation of a higher molecular weight form of CHT1 on the cell surface in HEK293 cells. Two different epitope-tagged CHT1 proteins expressed in the same cells can be co-immunoprecipitated. Moreover, co-expression of an inactive mutant I89A with the wild type induces a dominant-negative effect on the overall choline uptake activity. These results indicate that CHT1 forms a homo-oligomer on the cell surface in cultured cells.
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Takayama Y, Kotake N, Haga T, Suzuki T, Mabuchi K. Formation of one-way-structured cultured neuronal networks in microfluidic devices combining with micropatterning techniques. J Biosci Bioeng 2012; 114:92-5. [DOI: 10.1016/j.jbiosc.2012.02.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 02/10/2012] [Accepted: 02/13/2012] [Indexed: 10/28/2022]
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Takayama Y, Kotake N, Haga T, Suzuki T, Mabuchi K. Microfabrication- and microfluidics-based patterning of cultured neuronal network. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:3613-6. [PMID: 22255121 DOI: 10.1109/iembs.2011.6090606] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The cultured neuronal monolayer has been a promising model system for studying the neuronal dynamics, from single cell to network-wide level. Randomness in the reconstituted network structure has, however, hindered regulated signal transmissions from one neuron to another or from one neuronal population to another. Applying microfabrication-based cell patterning techniques is a promising approach to handling these problems. In the present study, we attempt to regulate the direction of axon development and the pathway of signal transmissions in cultured neuronal networks using micro-fabrication and - fluidic techniques. We created a PDMS-based culture device, which consisted of arrays of U-shaped cell trapping microwells, and placed it onto a chemically micropatterned glass substrate. After 6 days in vitro, we confirmed that cortical neurons extended neurites along the medium flow direction and the micropatterned regions.
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Yamada H, Imajoh-Ohmi S, Haga T. The high-affinity choline transporter CHT1 is regulated by the ubiquitin ligase Nedd4-2. ACTA ACUST UNITED AC 2012; 33:1-8. [PMID: 22361880 DOI: 10.2220/biomedres.33.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The high-affinity choline transporter (CHT1), which is specifically expressed in cholinergic neurons, constitutes a rate-limiting step for acetylcholine synthesis. We have found that the exogenous ubiquitin ligase Nedd4-2 interacts with CHT1 expressed in HEK293 cells decreasing the amount of cell surface CHT1 by approximately 40%, and that small interfering RNA for endogenous Nedd4-2 enhances the choline uptake activity by CHT1 in HEK293 cells. These results indicate that Nedd4-2-mediated ubiquitination regulates the cell surface expression of CHT1 in cultured cells and suggest a possibility that treatments or drugs which inhibit the interaction between CHT1 and Nedd4-2 might be useful for diseases involving decrease in acetylcholine level such as Alzheimer's disease.
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Shiroishi M, Tsujimoto H, Makyio H, Asada H, Yurugi-Kobayashi T, Shimamura T, Murata T, Nomura N, Haga T, Iwata S, Kobayashi T. Platform for the rapid construction and evaluation of GPCRs for crystallography in Saccharomyces cerevisiae. Microb Cell Fact 2012; 11:78. [PMID: 22694812 PMCID: PMC3495400 DOI: 10.1186/1475-2859-11-78] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Accepted: 06/13/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Recent successes in the determination of G-protein coupled receptor (GPCR) structures have relied on the ability of receptor variants to overcome difficulties in expression and purification. Therefore, the quick screening of functionally expressed stable receptor variants is vital. RESULTS We developed a platform using Saccharomyces cerevisiae for the rapid construction and evaluation of functional GPCR variants for structural studies. This platform enables us to perform a screening cycle from construction to evaluation of variants within 6-7 days. We firstly confirmed the functional expression of 25 full-length class A GPCRs in this platform. Then, in order to improve the expression level and stability, we generated and evaluated the variants of the four GPCRs (hADRB2, hCHRM2, hHRH1 and hNTSR1). These stabilized receptor variants improved both functional activity and monodispersity. Finally, the expression level of the stabilized hHRH1 in Pichia pastoris was improved up to 65 pmol/mg from negligible expression of the functional full-length receptor in S. cerevisiae at first screening. The stabilized hHRH1 was able to be purified for use in crystallization trials. CONCLUSIONS We demonstrated that the S. cerevisiae system should serve as an easy-to-handle and rapid platform for the construction and evaluation of GPCR variants. This platform can be a powerful prescreening method to identify a suitable GPCR variant for crystallography.
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Camou S, Haga T, Tajima T, Tamechika E. Detection of aqueous glucose based on a cavity size- and optical-wavelength-independent continuous-wave photoacoustic technique. Anal Chem 2012; 84:4718-24. [PMID: 22548281 DOI: 10.1021/ac203331w] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Toward the achievement of noninvasive and continuous monitoring of blood glucose level, we developed a new measurement method based on the continuous-wave photoacoustic (CW-PA) technique and performed the first validation in vitro with calibrated aqueous glucose solutions. The PA technique has been studied in the past but exclusively based on the pulse setup since the CW one exhibits dependence on the cavity dimensions, which is not compatible with the final application requirements. This paper describes a new strategy relying on the monitoring of the resonant-frequency relative shift induced by the change of glucose concentrations rather than amplitude signal levels at a fixed frequency. From in vitro results, we demonstrate a stable and reproducible response to glucose at various cavity dimensions and optical wavelengths, with a slope of 0.19 ±0.01%/g/dL. From theoretical considerations, this method is consistent with a relative acoustic velocity measurement, which also explains the aforementioned stability. The proposed method then resolves most of the issues usually associated with the CW-PA technique and makes it a potential alternative for the noninvasive and continuous monitoring of glycemia levels. However, experimental determination of sensor responses to albumin and temperature as two potential interferents shows similar levels, which points to the selectivity to glucose as a major issue we should deal with in future development.
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Kubo T, Ono S, Kimura T, Kobayashi S, Kondo T, Fukuda E, Haga T, Kameyama K. Development of the Periss Method to Generate GPCR Ligands/Binders from a Random Peptide Library with a Spider Neurotoxin Scaffold. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.3580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Ohta Y, Nishi S, Haga T, Tsubouchi T, Hasegawa R, Konishi M, Nagano Y, Tsuruwaka Y, Shimane Y, Mori K, Usui K, Suda E, Tsutsui K, Nishimoto A, Fujiwara Y, Maruyama T, Hatada Y. Screening and Phylogenetic Analysis of Deep-Sea Bacteria Capable of Metabolizing Lignin-Derived Aromatic Compounds. ACTA ACUST UNITED AC 2012. [DOI: 10.4236/ojms.2012.24021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Kawano K, Ono H, Iwashita O, Kurogi M, Haga T, Maeda K, Goto Y. stx genotype and molecular epidemiological analyses of Shiga toxin-producing Escherichia coli O157:H7/H- in human and cattle isolates. Eur J Clin Microbiol Infect Dis 2011; 31:119-27. [PMID: 21573816 DOI: 10.1007/s10096-011-1283-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 04/18/2011] [Indexed: 11/28/2022]
Abstract
The relationship between human diseases caused by infection with Shiga toxin (Stx)-producing Escherichia coli (STEC) O157 strains and O157 strains isolated from cattle was investigated in an area where stockbreeding is prolific. For this purpose, the stx genotypes, the molecular epidemiological characteristics of 268 STEC O157 strains including 211 human-origin strains and 57 cattle-origin strains, and clinical manifestations of 210 STEC-infected people were analyzed. Of 211 human-origin strains, 92 strains (44%) were of the stx1/stx2 genotype, and 74 strains (35%) were of the stx2c genotype. Most of the people infected with stx2c genotype strains presented no symptoms or mild symptoms such as slight diarrhea, except for 3 patients with bloody diarrhea. Of the 57 cattle-origin strains, 27 strains (47%) were of the stx2c genotype and 17 strains (30%) were of the stx1/stx2 genotype. Pulsed-field gel electrophoresis (PFGE) and insertion sequence (IS) analysis demonstrated that 11 isolates (41%) of the 27 cattle isolates of the stx2c genotype had high homology (>95% identity) with human isolates. These results suggest that some genetic patterns of the stx2c genotype strains might be preserved in cattle or their surrounding environment for several years, and during these periods, they might have opportunities to infect people through various routes. Because of the mild virulence of the stx2c genotype strains, they seemed to be transmitted asymptomatically from cattle to humans and then spread from person to person. It may be a public health concern. Further, they occasionally cause severe symptoms in humans; therefore, caution is warranted for infections by stx2c genotype O157 strains, in addition to stx2-possessing genotype O157 strains.
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Asada H, Uemura T, Yurugi-Kobayashi T, Shiroishi M, Shimamura T, Tsujimoto H, Ito K, Sugawara T, Nakane T, Nomura N, Murata T, Haga T, Iwata S, Kobayashi T. Evaluation of the Pichia pastoris expression system for the production of GPCRs for structural analysis. Microb Cell Fact 2011; 10:24. [PMID: 21513509 PMCID: PMC3094209 DOI: 10.1186/1475-2859-10-24] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 04/22/2011] [Indexed: 11/18/2022] Open
Abstract
Background Various protein expression systems, such as Escherichia coli (E. coli), Saccharomyces cerevisiae (S. cerevisiae), Pichia pastoris (P. pastoris), insect cells and mammalian cell lines, have been developed for the synthesis of G protein-coupled receptors (GPCRs) for structural studies. Recently, the crystal structures of four recombinant human GPCRs, namely β2 adrenergic receptor, adenosine A2a receptor, CXCR4 and dopamine D3 receptor, were successfully determined using an insect cell expression system. GPCRs expressed in insect cells are believed to undergo mammalian-like posttranscriptional modifications and have similar functional properties than in mammals. Crystal structures of GPCRs have not yet been solved using yeast expression systems. In the present study, P. pastoris and insect cell expression systems for the human muscarinic acetylcholine receptor M2 subtype (CHRM2) were developed and the quantity and quality of CHRM2 synthesized by both expression systems were compared for the application in structural studies. Results The ideal conditions for the expression of CHRM2 in P. pastoris were 60 hr at 20°C in a buffer of pH 7.0. The specific activity of the expressed CHRM2 was 28.9 pmol/mg of membrane protein as determined by binding assays using [3H]-quinuclidinyl benzilate (QNB). Although the specific activity of the protein produced by P. pastoris was lower than that of Sf9 insect cells, CHRM2 yield in P. pastoris was 2-fold higher than in Sf9 insect cells because P. pastoris was cultured at high cell density. The dissociation constant (Kd) for QNB in P. pastoris was 101.14 ± 15.07 pM, which was similar to that in Sf9 insect cells (86.23 ± 8.57 pM). There were no differences in the binding affinity of CHRM2 for QNB between P. pastoris and Sf9 insect cells. Conclusion Compared to insect cells, P. pastoris is easier to handle, can be grown at lower cost, and can be expressed quicker at a large scale. Yeast, P. pastoris, and insect cells are all effective expression systems for GPCRs. The results of the present study strongly suggested that protein expression in P. pastoris can be applied to the structural and biochemical studies of GPCRs.
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Haga T. [G protein-coupled receptor kinase (GRK)]. Nihon Yakurigaku Zasshi 2010; 136:215-218. [PMID: 20948157 DOI: 10.1254/fpj.136.215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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Takeda S, Kadowaki S, Haga T, Takaesu H, Mitaku S. Corrigendum to: Identification of G protein-coupled receptor genes from the human genome sequence (FEBS 26131). FEBS Lett 2010. [DOI: 10.1016/s0014-5793(02)03001-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Fujii T, Masai M, Misawa H, Okuda T, Takada-Takatori Y, Moriwaki Y, Haga T, Kawashima K. Acetylcholine synthesis and release in NIH3T3 cells coexpressing the high-affinity choline transporter and choline acetyltransferase. J Neurosci Res 2010; 87:3024-32. [PMID: 19405101 DOI: 10.1002/jnr.22117] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Acetylcholine (ACh) is known to be a key neurotransmitter in the central and peripheral nervous systems, but it is also produced in a variety of non-neuronal tissues and cells, including lymphocytes, placenta, amniotic membrane, vascular endothelial cells, keratinocytes, and epithelial cells in the digestive and respiratory tracts. To investigate contribution made by the high-affinity choline transporter (CHT1) to ACh synthesis in both cholinergic neurons and nonneuronal cells, we transfected rat CHT1 cDNA into NIH3T3ChAT cells, a mouse fibroblast line expressing mouse choline acetyltransferase (ChAT), to establish the NIH3T3ChAT 112-1 cell line, which stably expresses both CHT1 and ChAT. NIH3T3ChAT 112-1 cells showed increased binding of the CHT1 inhibitor [(3)H]hemicholinium-3 (HC-3) and greater [(3)H]choline uptake and ACh synthesis than NIH3T3ChAT 103-1 cells, a CHT1-negative control cell line. HC-3 significantly inhibited ACh synthesis in NIH3T3ChAT 112-1 cells but did not affect synthesis in NIH3T3ChAT 103-1 cells. ACh synthesis in NIH3T3ChAT 112-1 cells was also reduced by amiloride, an inhibitor of organic cation transporters (OCTs) involved in low-affinity choline uptake, and by procaine and lidocaine, two local anesthetics that inhibit plasma membrane phospholipid metabolism. These results suggest that CHT1 plays a key role in ACh synthesis in NIH3T3ChAT 112-1 cells and that choline taken up by OCTs or derived from the plasma membrane is also utilized for ACh synthesis in both cholinergic neurons and nonneuronal cholinergic cells, such as lymphocytes.
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Fujimura T, Okuyama R, Ohtani T, Ito Y, Haga T, Hashimoto A, Aiba S. Perilesional treatment of metastatic melanoma with interferon-β. Clin Exp Dermatol 2009; 34:793-9. [DOI: 10.1111/j.1365-2230.2009.03207.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Suzuki T, Namba K, Yamagishi R, Kaneko H, Haga T, Nakata H. A highly conserved tryptophan residue in the fourth transmembrane domain of the A1adenosine receptor is essential for ligand binding but not receptor homodimerization. J Neurochem 2009; 110:1352-62. [DOI: 10.1111/j.1471-4159.2009.06227.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Mitra S, Matsuo Y, Haga T, Yasumoto-Hirose M, Yoon J, Kasai H, Yokota A. Leptobacterium flavescens gen. nov., sp. nov., a marine member of the family Flavobacteriaceae, isolated from marine sponge and seawater. Int J Syst Evol Microbiol 2009; 59:207-12. [DOI: 10.1099/ijs.0.004358-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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42
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Yurugi-Kobayashi T, Asada H, Shiroishi M, Shimamura T, Funamoto S, Katsuta N, Ito K, Sugawara T, Tokuda N, Tsujimoto H, Murata T, Nomura N, Haga K, Haga T, Iwata S, Kobayashi T. Comparison of functional non-glycosylated GPCRs expression in Pichia pastoris. Biochem Biophys Res Commun 2009; 380:271-6. [PMID: 19167344 DOI: 10.1016/j.bbrc.2009.01.053] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2008] [Accepted: 01/13/2009] [Indexed: 11/27/2022]
Abstract
N-linked glycosylation is the most common post-translational modification of G-protein-coupled receptors (GPCRs) and is correlated to the localization and function of the receptors depending on each receptor. However, heterogeneity of glycosylation can interfere with protein crystallization. The removal of N-linked glycosylation from membrane proteins improves the ability to crystallize these proteins. We screened 25 non-glycosylated GPCRs for functional receptor production in the methylotrophic yeast Pichia pastoris using specific ligand-receptor binding assays. We found that five clones were expressed at greater than 10 pmol/mg, 9 clones at 1-10 pmol/mg and 11 clones at less than 1 pmol/mg of membrane protein. Further optimization of culture parameters including culture scale, induction time, pH and temperature enabled us to achieve expression of a functional human muscarinic acetylcholine receptor subtype 2 (CHRM2) with a B(max) value of 51.2 pmol/mg of membrane protein. Approximately 1.9 mg of the human CHRM2 was produced from a 1-L culture.
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Kageyama A, Haga T, Kasai H, Shizuri Y, Omura S, Takahashi Y. Marihabitans asiaticum gen. nov., sp. nov., a meso-diaminopimelic acid-containing member of the family Intrasporangiaceae. Int J Syst Evol Microbiol 2008; 58:2429-32. [DOI: 10.1099/ijs.0.65210-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Nakamura T, Sakai M, Sadakane Y, Haga T, Goto Y, Kinouchi T, Saito T, Fujii N. Differential rate constants of racemization of aspartyl and asparaginyl residues in human alpha A-crystallin mutants. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1192-9. [PMID: 18477484 DOI: 10.1016/j.bbapap.2008.04.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2007] [Revised: 03/27/2008] [Accepted: 04/07/2008] [Indexed: 10/22/2022]
Abstract
Asp58 and Asp151 in alpha A-crystallin of human eye lenses become highly inverted and isomerized to d-beta-Asp residues with age. Racemization was previously shown to proceed rapidly when the residue on the carboxyl side of the Asp residue is small. Asn was also demonstrated to be more susceptible to racemization than Asp in protein. In this study, the changes of rate constants for racemization at Asp58 and Asp151 and at Asn58 and Asn151 were investigated using D58N, S59T, D151N and A152V mutants obtained through site-directed mutagenesis. The rate constant of racemization at Asn151 in D151N was found to be 1.5 times more rapid than Asp151 in the wild-type. For A152V, the rate constant at Asp151 was 1/4 that of the wild-type. There were no significant differences in the rate constants of racemization for both Asp58 and Asn58 residues. The aggregate size of D58N, S59T and D151N mutants increased or increased in polydispersity and their chaperone activities decreased. The size and chaperone activity of A152V was unchanged. These results suggest that structures close to Asp58 and Asp151 residues in the protein affect the rate constant of Asp racemization and the size and chaperone function of alpha A-crystallin.
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Chikaraishi H, Takami S, Inoue T, Ise T, Niwa H, Haga T. Control system of dc power supplies for LHD superconducting coils. FUSION ENGINEERING AND DESIGN 2008. [DOI: 10.1016/j.fusengdes.2008.01.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Hashimoto Y, Morisawa K, Saito H, Jojima E, Yoshida N, Haga T. Muscarinic M4 receptor recycling requires a motif in the third intracellular loop. J Pharmacol Exp Ther 2008; 325:947-53. [PMID: 18337477 DOI: 10.1124/jpet.107.135095] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study was performed to identify sequence(s) in the third intracellular loop (i3) of the muscarinic acetylcholine receptor M4 subtype (M4 receptor) involved in its internalization and recycling. In transiently transfected human embryonic kidney 293-tsA201 cells, 40 to 50% of cell-surface M4 receptors are internalized in an agonist-dependent manner, and approximately 65% of internalized receptors are recycled back to the cell surface after removal of the agonist. We examined the internalization and recycling of M4 receptor mutants with partial deletion in i3 and found that various mutants (M4del-K(235)-K(240), M4del-T(241)-K(271), and M4del-W(339)-N(372)) showed internalization and cell-surface recycling in a similar manner to the M4 receptor. We also found that the mutant M4del-L(272)-R(338) was internalized to only half the extent of the M4 receptor and was recycled after agonist removal, and the mutant M4del-V(373)-A(393) was also internalized to half the extent of the wild type but was not recycled back to the cell surface after agonist removal. When the sequence corresponding to Val(373)-Ala(393) was grafted onto the i3 portion of a recycling-negative mutant of muscarinic M2 receptor with deletion of almost the whole of the i3 sequence, approximately 40% of the chimeric receptor on the cell surface was internalized, and more than 65% of the internalized receptors were recycled back to the cell surface. These results indicate that the regions including Leu(272)-Arg(338) and Val(373)-Ala(393) are involved in internalization of the M4 receptor, and the region including Val(373)-Ala(393) is indispensable for its recycling, whereas the other regions of i3 are dispensable for internalization and recycling.
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Yamada H, Imajoh‐Ohmi S, Haga T. Regulation of the high affinity choline transporter (CHT1) by ubiquitin ligase Nedd4‐2. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.813.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Urashima K, Kubo Y, Nishikawa S, Nakamura T, Hayashi K, Yamada H, Osawa C, Okuda T, Haga T. The high affinity choline transporter: topology and choline binding site as studied by site‐directed mutagenesis. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.813.14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Kawano K, Okada M, Haga T, Maeda K, Goto Y. Relationship between pathogenicity for humans and stx genotype in Shiga toxin-producing Escherichia coli serotype O157. Eur J Clin Microbiol Infect Dis 2007; 27:227-32. [PMID: 18071766 DOI: 10.1007/s10096-007-0420-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2007] [Accepted: 10/30/2007] [Indexed: 11/24/2022]
Abstract
To examine the reason why people infected with Shiga toxin (Stx) producing Escherichia coli (STEC) O157 strains develop varying clinical manifestations, 65 STEC O157 isolates originating from 64 different occurrences of infection in Miyazaki Prefecture in 2001-2003 and their 79 infected individuals were analyzed by stx genotyping, quantitative analysis of reversed passive latex agglutination (RPLA), genomic DNA analysis using pulsed-field gel electrophoresis (PFGE), and clinical manifestations. The isolates were found to carry the following stx genes: stx2vha alone (60.0%), stx1/stx2 (27.7%), stx1/stx2vha (6.1%), stx2 alone (3.1%), and stx2/stx2vha (3.1%). No strain carried the stx1 gene alone. STEC strains carrying stx2 were more frequently associated with clinical manifestations of hemolytic-uremic syndrome (HUS) or bloody diarrhea than those carrying stx2vha. Clusters of PFGE banding patterns were correlated well with the stx genotypes. We conclude that stx genotype is one of the important factors of clinical outcome of STEC O157 infection and that pathogenicity for humans was higher in the stx2 genotype strains than in the stx2vha genotype strains, as reported previously by other researchers. Further, we newly found that four clusters identified by PFGE using restriction enzyme XbaI, stx genotypes and clinical manifestations were well correlated with each other.
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Suga H, Haga T. Ligand screening system using fusion proteins of G protein-coupled receptors with G protein alpha subunits. Neurochem Int 2007; 51:140-64. [PMID: 17659814 DOI: 10.1016/j.neuint.2007.06.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2007] [Revised: 06/07/2007] [Accepted: 06/08/2007] [Indexed: 01/04/2023]
Abstract
G protein-coupled receptors (GPCRs) constitute one of the largest families of genes in the human genome, and are the largest targets for drug development. Although a large number of GPCR genes have recently been identified, ligands have not yet been identified for many of them. Various assay systems have been employed to identify ligands for orphan GPCRs, but there is still no simple and general method to screen for ligands of such GPCRs, particularly of G(i)-coupled receptors. We have examined whether fusion proteins of GPCRs with G protein alpha subunit (Galpha) could be utilized for ligand screening and showed that the fusion proteins provide an effective method for the purpose. This article focuses on the followings: (1) characterization of GPCR genes and GPCRs, (2) identification of ligands for orphan GPCRs, (3) characterization of GPCR-Galpha fusion proteins, and (4) identification of ligands for orphan GPCRs using GPCR-Galpha fusion proteins.
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