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dc.contributor.authorHeyworth, Clare Men
dc.contributor.authorWhetton, Anthony Den
dc.contributor.authorWong, Sen
dc.contributor.authorMartin, Ben
dc.contributor.authorHouslay, Men
dc.date.accessioned2010-12-03T11:50:07Z
dc.date.available2010-12-03T11:50:07Z
dc.date.issued1985-06-15
dc.identifier.citationInsulin inhibits the cholera-toxin-catalysed ribosylation of a Mr-25000 protein in rat liver plasma membranes. 1985, 228 (3):593-603 Biochem Jen
dc.identifier.issn0264-6021
dc.identifier.pmid3896232
dc.identifier.urihttp://hdl.handle.net/10541/117105
dc.description.abstractA method is described for preparing a plasma-membrane fraction from hepatocytes by a rapid, gentle, Percoll fractionation procedure. Cholera toxin elicited the ribosylation of a number of proteins in these membranes, including the components of the stimulatory guanine nucleotide regulatory protein, Ns. Insulin, however, inhibited the ability of cholera toxin to ribosylate a protein of Mr 25 000. The action was decreased in membranes from cells that had been pre-treated with glucagon. Ribosylation of both the components of Ns and the Mr-25 000 species occurred in whole cells treated with cholera toxin, because membranes from such treated cells exhibited decreased labelling when incubated with [32P]NAD+ and activated cholera toxin. The labelling of proteins, including the Mr-25 000 species, with [32P]NAD+ and cholera toxin in the plasma membranes was decreased by an inhibitor of ribosylation. Azido-GTP photoaffinity labelling identified several high-affinity GTP-binding proteins, including one of Mr 25 000. Cholera toxin failed to ribosylate the Mr-25 000 protein in membranes from cells that had been pre-treated with the tumour-promoting agent 12-O-tetradecanoylphorbol 13-acetate (TPA). In membranes from such treated cells, insulin actually allowed cholera toxin to label this species. As TPA activates protein kinase C, it is possible that the Mr-25 000 protein, or a species that interacts with it, is a substrate for phosphorylation. These observations may offer an explanation for some of the perturbing effects that TPA exerts on insulin's action. It is suggested that the insulin receptor interacts with the guanine nucleotide regulatory protein system in the liver, and that the Mr-25 000 species may be a component of Nin, a specific guanine nucleotide regulatory protein that has been proposed to mediate certain of the actions of insulin on target cells [Houslay & Heyworth (1983) Trends Biochem. Sci. 8, 449-452].
dc.language.isoenen
dc.subject.meshAnimals
dc.subject.meshCell Fractionation
dc.subject.meshCell Membrane
dc.subject.meshCholera Toxin
dc.subject.meshElectrophoresis, Polyacrylamide Gel
dc.subject.meshInsulin
dc.subject.meshLiver
dc.subject.meshMale
dc.subject.meshMembrane Proteins
dc.subject.meshRats
dc.subject.meshRats, Inbred Strains
dc.subject.meshTetradecanoylphorbol Acetate
dc.titleInsulin inhibits the cholera-toxin-catalysed ribosylation of a Mr-25000 protein in rat liver plasma membranes.en
dc.typeArticleen
dc.contributor.departmentDepartment of Biochemistry and Applied Molecular Biology, UMIST, P.O.Box 88, Manchester M60 1QD, UK.en
dc.identifier.journalThe Biochemical Journalen
html.description.abstractA method is described for preparing a plasma-membrane fraction from hepatocytes by a rapid, gentle, Percoll fractionation procedure. Cholera toxin elicited the ribosylation of a number of proteins in these membranes, including the components of the stimulatory guanine nucleotide regulatory protein, Ns. Insulin, however, inhibited the ability of cholera toxin to ribosylate a protein of Mr 25 000. The action was decreased in membranes from cells that had been pre-treated with glucagon. Ribosylation of both the components of Ns and the Mr-25 000 species occurred in whole cells treated with cholera toxin, because membranes from such treated cells exhibited decreased labelling when incubated with [32P]NAD+ and activated cholera toxin. The labelling of proteins, including the Mr-25 000 species, with [32P]NAD+ and cholera toxin in the plasma membranes was decreased by an inhibitor of ribosylation. Azido-GTP photoaffinity labelling identified several high-affinity GTP-binding proteins, including one of Mr 25 000. Cholera toxin failed to ribosylate the Mr-25 000 protein in membranes from cells that had been pre-treated with the tumour-promoting agent 12-O-tetradecanoylphorbol 13-acetate (TPA). In membranes from such treated cells, insulin actually allowed cholera toxin to label this species. As TPA activates protein kinase C, it is possible that the Mr-25 000 protein, or a species that interacts with it, is a substrate for phosphorylation. These observations may offer an explanation for some of the perturbing effects that TPA exerts on insulin's action. It is suggested that the insulin receptor interacts with the guanine nucleotide regulatory protein system in the liver, and that the Mr-25 000 species may be a component of Nin, a specific guanine nucleotide regulatory protein that has been proposed to mediate certain of the actions of insulin on target cells [Houslay & Heyworth (1983) Trends Biochem. Sci. 8, 449-452].


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