1
|
Chudziak F, Schwanstecher M, Laatsch H, Panten U. Synthesis of a 125I labelled azido-substituted glibenclamide analogue for photoaffinity labelling of the sulfonylurea receptor. J Labelled Comp Radiopharm 2006. [DOI: 10.1002/jlcr.2580340713] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
2
|
Sievert MK, Pilli G, Liu Y, Sutkowski EM, Seamon KB, Ruoho AE. Photoaffinity labeling of adenylyl cyclase. Methods Enzymol 2002; 345:188-97. [PMID: 11665604 DOI: 10.1016/s0076-6879(02)45016-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Affiliation(s)
- Michael K Sievert
- Department of Pharmacology, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
| | | | | | | | | | | |
Collapse
|
3
|
Brunet-Desruet MD, Ghezzi C, Morin C, Comet M, Fagret D. Biological evaluation of two iodine-123-labeled D-glucose acetals prepared as glucose transporter radioligands. Nucl Med Biol 1998; 25:473-80. [PMID: 9720665 DOI: 10.1016/s0969-8051(98)00005-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two iodinated acetals of D-glucose, 4,6-(R)-O-(2'-iodoethylidene)-alpha, beta-D-glucose (1) and 4,6-(R)-O-(4'-iodobenzylidene)-alpha, beta-D-glucose (2), were prepared and their potential as suitable SPECT radioligands for imaging of glucose transporters was studied. Both are analogs of acetal D-glucose derivatives, which are known to bind to the exofacial sites of the glucose transport protein (GluT). To assess whether iodinated acetals 1 and 2 interacted with the glucose transporter, they were tested in vitro in human erythrocytes (GluT1) and neonatal rat cardiomyocytes (GluT4). The results indicated that 1 and 2 had a very low affinity for the glucose transporter and probably accumulated in cells. Study of their tissue distribution was carried out in the mouse in vivo: Both compounds showed fast tissue clearance with preferential renal elimination. It is concluded that iodinated acetals of D-glucose 1 and 2 are not suitable for GluT targeting in vivo.
Collapse
Affiliation(s)
- M D Brunet-Desruet
- Laboratoire D'Etude des Radiopharmaceutiques, ESA CNRS 5077, Faculté de Médecine et de Pharmacie, Université de Grenoble, La Tronche, France
| | | | | | | | | |
Collapse
|
4
|
Li WM, McNeill JH. Quantitative methods for measuring the insulin-regulatable glucose transporter (Glut4). J Pharmacol Toxicol Methods 1997; 38:1-10. [PMID: 9339410 DOI: 10.1016/s1056-8719(97)00036-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This review article describes various quantitation methods for the insulin-regulatable glucose transporter (Glut4). Several methods including reconstituted glucose transport, cytochalasin B binding assays, immunocytochemistry, immunoblots, ELISA, and the more recently developed exofacial labels are discussed. Since Glut4 translocates from an intracellular compartment to the plasma membrane in response to the action of insulin, it is of particular interest to measure Glut4 changes in the membrane fractions. Hence, the measurement of Glut4 commonly involves the isolation of cell membranes using subcellular fractionation in combination with one of the quantitation methods. The limitations of each quantitation method due to the use of subcellular fractionation are discussed in this article. As well, the advantages and disadvantages in terms of isoform specificity and technical difficulties of each method are presented.
Collapse
Affiliation(s)
- W M Li
- Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada
| | | |
Collapse
|
5
|
|
6
|
Wandel S, Schürmann A, Becker W, Summers SA, Shanahan MF, Joost HG. Substitution of conserved tyrosine residues in helix 4 (Y143) and 7 (Y293) affects the activity, but not IAPS-forskolin binding, of the glucose transporter GLUT4. FEBS Lett 1994; 348:114-8. [PMID: 8034025 DOI: 10.1016/0014-5793(94)00558-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Six tyrosine residues (Y28, Y143, Y292, Y293, Y308, Y432(1)) which are conserved in all mammalian glucose transporters were substituted for phenylalanine by site-directed mutagenesis, and mutant glucose transporters were transiently expressed in COS-7 cells. Glucose transport activity as assessed by reconstitution of the solubilized transporters into lecithin liposomes was reduced by 70% in the mutant Y143F and appeared to be abolished in Y293F, but was not affected by substitution of Y28, Y292, Y308 and Y432. In contrast, covalent binding of the photolabel 125IAPS-forskolin was normal in all mutants. Stable expression of the mutants Y143F, Y293F, and Y292F in LTK cells yielded identical results. These data indicate that only two of the 6 conserved helical tyrosine residues, located in helices 4 and 7, are essential for full activity, but not for IAPS-forskolin binding of the GLUT4.
Collapse
Affiliation(s)
- S Wandel
- Institut für Pharmakologie und Toxikologie, RWTH Aachen, Germany
| | | | | | | | | | | |
Collapse
|
7
|
Langford CK, Burchmore RJ, Hart DT, Wagner W, Landfear SM. Biochemistry and molecular genetics of Leishmania glucose transporters. Parasitology 1994; 108 Suppl:S73-83. [PMID: 8084658 DOI: 10.1017/s0031182000075740] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Glucose is utilized as a significant source of metabolic energy by Leishmania parasites. This sugar is accumulated by the parasite via a specific carrier-mediated transport system located in the parasite membrane. Parasites may also contain another transporter that shuttles glucose between the cytoplasm and the glycosome, a membrane-bound organelle where the early steps of glycolysis occur. The transport systems of both the insect stage promastigotes and the intracellular amastigotes have been characterized and shown to have kinetic properties that are consistent with the different physiological environments of the insect gut and the macrophage phagolysosome. Several genes have been cloned from Leishmania species which encode proteins with substantial sequence similarity to glucose transporters from mammals and lower eukaryotes. Two of these genes are expressed preferentially in the promastigote stage of the life cycle, where glucose is more readily available and more rapidly transported and metabolized than in the intracellular amastigotes. One of these two developmentally-regulated genes has been functionally expressed in Xenopus oocytes and shown to encode a glucose transporter. A third gene encodes a protein that is also a member of the glucose transporter family on the basis of sequence similarity and proposed secondary structure. However, the significant differences between this protein and the other two suggest that it is likely to transport a different substrate. Functional expression will be required to define the specific biochemical role of each gene within the parasite.
Collapse
Affiliation(s)
- C K Langford
- Department of Microbiology and Immunology, Oregon Health Sciences University, Portland 97201
| | | | | | | | | |
Collapse
|
8
|
Baldwin SA. Mammalian passive glucose transporters: members of an ubiquitous family of active and passive transport proteins. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1154:17-49. [PMID: 8507645 DOI: 10.1016/0304-4157(93)90015-g] [Citation(s) in RCA: 225] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- S A Baldwin
- Department of Biochemistry and Molecular Biology, University of Leeds, UK
| |
Collapse
|
9
|
Sutkowski EM, Maher F, Laurenza A, Simpson IA, Seamon KB. Interaction of 7-bromoacetyl-7-desacetylforskolin, and alkylating derivative of forskolin, with bovine brain adenylyl cyclase and human erythrocyte glucose transporter. Biochemistry 1993; 32:2415-22. [PMID: 8443181 DOI: 10.1021/bi00060a037] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
7-Bromoacetyl-7-desacetylforskolin (BrAcFsk), an alkylating derivative of forskolin, activated adenylyl cyclase and irreversibly blocked high affinity forskolin binding sites in human platelet membranes and rat brain membranes (Laurenza et al., 1990). Photoincorporation of an iodinated arylazido derivative of forskolin, 125I-6-AIPP-Fsk, into adenylyl cyclase in bovine brain membranes was irreversibly inhibited by BrAcFsk but not by 1,9-dideoxy-BrAcFsk, suggesting that BrAcFsk was reacting specifically with a nucleophilic group(s) at the forskolin binding site of adenylyl cyclase. Immunoblotting with antiforskolin antiserum demonstrated that partially purified bovine brain adenylyl cyclase had incorporated BrAcFsk. The interaction of BrAcFsk with the glucose transporter in human erythrocyte membranes was examined in a similar manner. Photoincorporation of 125I-7-AIPP-Fsk, an iodinated arylazido derivative of forskolin which is specific for the glucose transporter, into the glucose transporter was not irreversibly inhibited by BrAcFsk, suggesting that, in contrast to adenylyl cyclase, there is no reactive nucleophilic group at the forskolin binding site on the human erythrocyte glucose transporter. The immunoblotting procedure with antiforskolin antiserum confirmed that BrAcFsk was not covalently attached to human erythrocyte glucose transporter.
Collapse
Affiliation(s)
- E M Sutkowski
- Molecular Pharmacology Laboratory, Food and Drug Administration, Bethesda, Maryland 20892
| | | | | | | | | |
Collapse
|
10
|
Diamond D, Carruthers A. Metabolic control of sugar transport by derepression of cell surface glucose transporters. An insulin-independent recruitment-independent mechanism of regulation. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53271-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
|
11
|
Bhat SV. Forskolin and congeners. FORTSCHRITTE DER CHEMIE ORGANISCHER NATURSTOFFE = PROGRESS IN THE CHEMISTRY OF ORGANIC NATURAL PRODUCTS. PROGRES DANS LA CHIMIE DES SUBSTANCES ORGANIQUES NATURELLES 1993; 62:1-74. [PMID: 8349218 DOI: 10.1007/978-3-7091-9250-4_1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- S V Bhat
- Department of Chemistry, Indian Institute of Technology, Powai, Bombay
| |
Collapse
|
12
|
Hellwig B, Brown FM, Schürmann A, Shanahan MF, Joost HG. Localization of the binding domain of the inhibitory ligand forskolin in the glucose transporter GLUT-4 by photolabeling, proteolytic cleavage and a site-specific antiserum. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1111:178-84. [PMID: 1420253 DOI: 10.1016/0005-2736(92)90309-a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The binding domain of forskolin in the adipocyte/muscle-type glucose transporter (GLUT-4) was localized with the aid of the photoreactive derivative, [125I]IAPS-forskolin (3-[125I]iodo-4-azidophenethylamido-7-O-succinyldeacetyl-forskolin). Plasma membranes from insulin-treated rat adipocytes containing predominantly the GLUT-4 isoform were irradiated with UV light in the presence of [125I]IAPS-forskolin. The covalently labeled glucose transporters were isolated by immunoprecipitation with specific antiserum and partially digested with trypsin and elastase. The fragments were separated by gel electrophoresis, transferred on to nitrocellulose membranes, and identified by direct autoradiography and by immunoassay with antiserum against a peptide sequence corresponding to the C-terminus of GLUT-4. Digestion with a high-purity grade trypsin generated two photolabeled fragments with apparent molecular weights of 21 and 16 kDa. Since the antiserum detected two fragments with identical electrophoretic mobility, both labeled fragments appeared to contain the intact C-terminus of GLUT-4. In contrast, digestion with elastase generated only one photolabeled fragment with intact C-terminus at 21 kDa, and a smaller unlabeled fragment with intact C-terminus at 15 kDa. A less pure trypsin preparation generated two labeled (21 and 17 kDa) and one unlabeled (15 kDa) fragment with intact C-terminus. These data suggest that the site of covalent binding of IAPS-forskolin in the GLUT-4 is located within a region of 1-6 kDa defined by the difference between the unlabeled C-terminal fragment (15 kDa) and the labeled fragments (21, 17 and 16 kDa). Based on a tentative allocation of the fragments to the sequence of the GLUT-4, it is suggested that the covalent binding site of IAPS-forskolin is located between the membrane spanning helices 7-9, possibly in the proximity of helix 9.
Collapse
Affiliation(s)
- B Hellwig
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät der RWTH Aachen, Germany
| | | | | | | | | |
Collapse
|
13
|
Robbins JD, Appel NM, Laurenza A, Simpson IA, De Souza EB, Seamon KB. Differential identification and localization of adenylyl cyclase and glucose transporter in brain using iodinated derivatives of forskolin. Brain Res 1992; 581:148-52. [PMID: 1498664 DOI: 10.1016/0006-8993(92)90354-c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Two radioiodinated derivatives of forskolin, [125I]6-IHPP-Fsk and [125I]7-IHPP-Fsk, were synthesized as specific ligands for adenylyl cyclase and glucose transporter, respectively. [125I]6-IHPP-Fsk bound to bovine brain homogenates with a Kd of 9 nM and binding was inhibited by forskolin but not 1,9-dideoxyforskolin, cytochalasin B, or D-glucose. [125I]7-IHPP-Fsk bound to bovine brain homogenates at two classes of binding sites with Kd's of 56 nM and 4.7 microM; cytochalasin B and D-glucose inhibited 75% of the high affinity binding while having no effect on the low affinity binding. [125I]6-IHPP-Fsk and [125I]7-IHPP-Fsk were used to localize adenylyl cyclase and glucose transporter in rat brain by receptor autoradiography. The pattern of binding obtained with [125I]6-IHPP-Fsk was similar to that observed using [3H]forskolin to detect adenylyl cyclase. In contrast, the pattern of binding obtained with [125I]7-IHPP-Fsk was similar to that observed by others using [3H]cytochalasin B to detect glucose transporter. These iodinated ligands are selective for adenylyl cyclase and glucose transporter and require significantly shorter exposure times to yield autoradiographs than tritiated ligands.
Collapse
Affiliation(s)
- J D Robbins
- Molecular Pharmacology Laboratory, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892
| | | | | | | | | | | |
Collapse
|
14
|
Chapter 6 Mechanisms of active and passive transport in a family of homologous sugar transporters found in both prokaryotes and eukaryotes. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/s0167-7306(08)60068-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
|
15
|
Forskolin photoaffinity labels with specificity for adenylyl cyclase and the glucose transporter. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)98850-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
16
|
Clancy B, Harrison S, Buxton J, Czech M. Protein synthesis inhibitors activate glucose transport without increasing plasma membrane glucose transporters in 3T3-L1 adipocytes. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)99198-2] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
17
|
Uchida S, Takami K, Kobayashi H, Hashimoto K, Matsumoto N. Functions of a co-transmitter, calcitonin gene-related peptide, on the neuromuscular junction. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1991; 287:39-50. [PMID: 1684696 DOI: 10.1007/978-1-4684-5907-4_4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- S Uchida
- Department of Pharmacology 1, School of Medicine, Osaka University, Japan
| | | | | | | | | |
Collapse
|
18
|
Liu KP, Tamir H, Adlersberg M. Photoaffinity labeling of the two forms of serotonin binding protein: peptide mapping of the binding sites. J Neurochem 1990; 54:963-70. [PMID: 2303822 DOI: 10.1111/j.1471-4159.1990.tb02344.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Serotonin binding protein (SBP) is a vesicular protein found in neurectoderm-derived cells that store 5-hydroxytryptamine (5-HT, serotonin), such as central and peripheral serotonergic neurons and paraneurons (parafollicular cells of the thyroid). 5-HT is stored as a complex with SBP in vivo. Two forms of the protein are found. These differ in molecular mass: one is 45 kDa and the other 56 kDa. It has been suggested that the 56-kDa form of SBP may be the precursor of the 45-kDa form. To study the relationship between these two proteins, we have used a covalently bound radiolabeled probe to analyze their binding domains. A photoaffinity reagent, N-(4-azido-2-nitrophenyl)-5-hydroxytryptamine (NAP-5-HT), was synthesized and characterized by nuclear magnetic resonance spectroscopy, mass spectra, and UV-visible absorption spectra. A 1 M excess of NAP-5-HT inhibited the binding of [3H]5-HT to SBP by 50%. NAP[3H]5-HT was also synthesized and attached to both high- and low-affinity binding sites on both forms of SBP. The high-affinity constants for 45-kDa and 56-kDa proteins were 0.8 nM and 0.02 nM, respectively, whereas the low-affinity constants were 0.3 microM and 0.15 microM. When the high-affinity site of partially purified SBP was photoaffinity-labeled with the reagent, two covalently labeled proteins (45 kDa and 56 kDa) were found by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Inhibition of the labeling of both proteins by 50% was observed in the presence of a 15-fold molar excess of 5-HT.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- K P Liu
- Division of Neuroscience, New York State Psychiatric Institute, NY 10032
| | | | | |
Collapse
|
19
|
Deuticke B, Grebe R, Haest CWM. Action of Drugs on the Erythrocyte Membrane. BLOOD CELL BIOCHEMISTRY 1990. [DOI: 10.1007/978-1-4757-9528-8_16] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
20
|
Affiliation(s)
- H G Joost
- Institute of Pharmacology and Toxicology, University of Göttingen, FRG
| | | |
Collapse
|
21
|
Laurenza A, Sutkowski EM, Seamon KB. Forskolin: a specific stimulator of adenylyl cyclase or a diterpene with multiple sites of action? Trends Pharmacol Sci 1989; 10:442-7. [PMID: 2692256 DOI: 10.1016/s0165-6147(89)80008-2] [Citation(s) in RCA: 324] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Forskolin, a naturally occurring diterpene, directly stimulates adenylyl cyclase and has been used extensively to increase cAMP and to elicit cAMP-dependent physiological responses. More recently, forskolin has been shown to inhibit a number of membrane transport proteins and channel proteins through a mechanism that does not involve the production of cAMP. Many of these channel proteins are predicted to have similar topographies in the membrane bilayer and it is tempting to speculate that forskolin may be binding at structurally homologous sites. Kenneth Seamon and colleagues discuss the cAMP-independent effects of forskolin and the structural similarity between forskolin and other physiologically important substances such as hexoses and steroids with respect to potential forskolin binding sites.
Collapse
|
22
|
Photoinhibition of 2-Amino-2-carboxybicyclo[2,2,1]heptane Transport by O-Diazoacetyl-L-serine. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84720-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
|
23
|
Insulin-regulated Glucose Uptake in Rat Adipocytes Is Mediated by Two Transporter Isoforms Present in at Least Two Vesicle Populations. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)63866-9] [Citation(s) in RCA: 207] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|
24
|
|
25
|
Hashimoto K, Watanabe Y, Uchida S, Yoshida H. Increase in the amount of adenylate cyclase in rat gastrocnemius muscle after denervation. Life Sci 1989; 44:1887-95. [PMID: 2786983 DOI: 10.1016/0024-3205(89)90308-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
After section of the sciatic nerve, the basal adenylate cyclase (AC) activity in rat gastrocnemius muscle increased 6-7 times per membrane protein and about 2 times per whole muscle in the following 30 or 40 days. The AC activity in the muscle 30 days after denervation was increased about 4 times by forskolin. Calcitonin gene-related peptide (CGRP) also increased the adenylate cyclase activity in the denervated muscle. The binding of [3H]-forskolin (10nM) to cells isolated from gastrocnemius muscle was examined to determine the amount of AC molecules. Inhibition of [3H]-forskolin binding by increasing amounts of unlabeled forskolin gave a sigmoid curve with a IC50 value of 3 x 10(-7) M. Results showed that the number of [3H]-forskolin binding sites per cell was higher on the denervated side than on the control side, like the basal AC activity. The IC50 values for inhibition by unlabeled forskolin of binding of [3H]-forskolin were similar to muscles on the control and denervated sides. These results suggest that an increase in the AC activity induced by denervation was due to an increase in the numbers of AC molecules in the muscle.
Collapse
Affiliation(s)
- K Hashimoto
- Department of Pharmacology I, Osaka University Medical School, Japan
| | | | | | | |
Collapse
|
26
|
Holman GD, Karim AR, Karim B. Photolabeling of erythrocyte and adipocyte hexose transporters using a benzophenone derivative of bis(D-mannose). BIOCHIMICA ET BIOPHYSICA ACTA 1988; 946:75-84. [PMID: 3207733 DOI: 10.1016/0005-2736(88)90459-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The benzophenone derivative of 1,3-bis(D-mannos-4-yloxy)-2-propylamine (BB-BMPA) has been tested as an exofacial photoaffinity label for the sugar transport systems of human erythrocytes and rat adipocytes. The half-maximal inhibition constants for the reagent are 971 microM in erythrocytes and 536 microM in basal and 254 microM in insulin-treated adipocytes. The photolabelling of erythrocyte membranes is very specific for the 50 kDa transporter peptide and is completely displaced by D-glucose. The exofacial photoaffinity labelling of adipocytes also shows labelling of a 50 kDa transporter peptide, which is displaced by cytochalasin B, but extensive nonspecific labelling of a 75 kDa plasma membrane peptide occurs. The transporter is labelled in insulin-treated cells but not in basal cells which indicates that this in situ labelling technique selectively reveals only those transporters that visit and are active in the plasma membrane during the labelling period. This also indicates that in basal cells transporters do not turn over rapidly. Subcellular redistribution of transporters after the labelling period has been studied. Following incubation and washing at 37 degrees C in the presence of insulin, 30% of the transporters photolabelled at the plasma membrane are internalised and are found in the light microsome fraction of the cell. The proportion of transporter that is observed to be internalised is much greater than can be accounted for by a contamination of the light microsome fraction by plasma membrane. The labelled 50 kDa transporter peptide in the light microsomes is enriched when compared with the carry-over of the 75 kDa nonspecifically labelled plasma membrane peptide. Thus we have obtained direct evidence for transporter translocation.
Collapse
Affiliation(s)
- G D Holman
- Department of Biochemistry, University of Bath, U.K
| | | | | |
Collapse
|
27
|
Resek JF, Ruoho AE. Photoaffinity labeling the beta-adrenergic receptor with an iodoazido derivative of norepinephrine. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68235-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|