Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sulphonylurea drugs stimulate glucose transport and metabolism in muscle and fat cells in vitro. The molecular basis for the insulin-mimetic extrapancreatic effects of these oral antidiabetic therapeutic agents is unknown at present. Here we demonstrate that incubation of 3T3 adipocytes with the novel sulphonylurea, glimepiride, causes a time- and concentration-dependent release of the glycosylphosphatidylinositol (GPI)-anchored ecto-proteins, 5'-nucleotidase, lipoprotein lipase and a 62 kDa cyclic AMP (cAMP)-binding protein from the plasma membrane into the culture medium. The change in the localization is accompanied by conversion of the membrane-anchored amphiphilic proteins into their soluble hydrophilic versions, as judged by pulse-chase experiments and Triton X-114 partitioning, and by appearance of anti-cross-reacting determinant (CRD) immunoreactivity of the released proteins as shown by Western blotting. Metabolic labelling of cells with myo-[14C]inositol demonstrates that inositol is retained in the major portion of released lipoprotein lipase and cAMP-binding ectoprotein. The identification of inositol phosphate after deamination of these proteins with nitrous acid suggests cleavage of their GPI membrane anchor by a GPI-specific phospholipase C. However, after longer incubation with glimepiride the amount of soluble versions of the GPI-proteins lacking inositol and anti-CRD immunoreactivity increases, which may be caused by additional drug-stimulated hydrolytic events within their GPI structure or C-termini. Since insulin also stimulates membrane release of these GPI-modified proteins, and in combination with glimepiride in a synergistic manner, sulphonylurea drugs may exert their peripheral actions in adipose tissue by using (part of) the insulin postreceptor signalling cascade at the step of activation of a GPI-specific phospholipase C.
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PMID:The sulphonylurea drug, glimepiride, stimulates release of glycosylphosphatidylinositol-anchored plasma-membrane proteins from 3T3 adipocytes. 767 37

Glycosyl-phosphatidylinositol-anchored membrane proteins (GPI-proteins) are normally identified either by cleavage of the lipid anchor using (glycosyl)phosphatidylinositol-specific phospholipases C or D (GPI-PLs) or by metabolic labeling of the lipid moiety with specific building blocks. Therefore, methods for discrimination between transmembrane proteins and GPI-proteins on the basis of their physicochemical properties are desirable. Here we are presenting a selective extraction method for typical well-characterized mammalian GPI-proteins, e.g., acetylcholine esterase, alkaline phosphatase, 5'-nucleotidase, and lipoprotein lipase, using a derivative of taurocholate. The results were compared to those obtained with well-characterized transmembrane proteins, e.g., insulin receptor and hydroxymethyl glutaryl coenzyme A-reductase, glucose transporters, or aminopeptidase M and several commercially available detergents. With regard to total membrane proteins, it was possible to selectively enrich GPI-proteins up to 8- to 14-fold by using concentrations between 0.1 and 0.3% of 4'-NH2-amino-7 beta-benzamido-taurocholic acid (BATC). In addition, the cleavage specificity and efficiency of (G)PI-PLs were increased in the presence of identical concentrations of BATC compared to commonly used detergents, e.g., Nonidet P-40. Therefore, the present study shows that the use of BATC facilitates the identification of glycosyl-phosphatidylinositol-anchored membrane proteins.
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PMID:4'-Amino-benzamido-taurocholic acid selectively solubilizes glycosyl-phosphatidylinositol-anchored membrane proteins and improves lipolytic cleavage of their membrane anchors by specific phospholipases. 813 45

A short-term incubation of isolated rat fat pads with vanadate showed the stimulated release of lipoprotein lipase (LPL) activity and suppression of the rise in extracellular adenosine level. The addition of adenosine to the medium showed inhibition of both the stimulated release of LPL activity and an increase in intracellular cAMP content by vanadate. A progressive increase in 5'-nucleotidase activity in the particulate fraction containing plasma membrane was suppressed by vanadate in a time- and dose-dependent manner, suggesting that vanadate inhibits, in part, the production of adenosine based on a dephosphorylation of AMP. In adipocytes, the inhibition of adenylate cyclase via A1 adenosine receptor is more predominant than the stimulation of adenylate cyclase via A2 adenosine receptor (Londos C. et al., Proc. Natl. Acad. Sci. U.S.A., 75, 5362-5366 (1978)). Therefore, vanadate may stimulate the release of LPL activity from the fat pads by suppressing the rise in extracellular adenosine level, accompanied by the activation of adenylate cyclase activity.
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PMID:Involvement of adenosine in vanadate-stimulated release of lipoprotein lipase activity. 978 34