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)

Epidermal growth factor (EGF) is now well known as a potent mitogen and differentiation factor for a variety of cells both in vivo and in vitro. Like other polypeptide hormones, EGF initially binds to a specific plasma membrane receptor on the target cells. In this study, we investigated the effect of streptozotocin-induced diabetes on EGF receptors on rat liver plasma membranes. An apparent increase in serum glucose concentration was observed in diabetic rats, and treatment of diabetic animals with insulin normalized the glucose concentration to the control level. There was no marked difference in hepatic membrane markers among the control, diabetic and insulin-treated diabetic animals, as judged by protein, sialic acid contents, and phosphodiesterase I and 5'-nucleotidase activities. The binding of 125I-EGF to membranes was found to be significantly lower in diabetic than in control animals. The value in diabetic animals was about 55% of the control level. Insulin treatment of diabetic animals restored the binding of 125I-EGF to the control level, whereas triiodothyronine (T3) treatment had no effect. Scatchard analysis of the binding data clearly showed that the decrease in EGF binding was due to a decrease in the number of receptors rather than to a change in receptor affinity. The decrease in EGF receptor number in diabetic animals was also confirmed by an experiment on affinity labeling of EGF receptors. EGF stimulated the phosphorylation of hepatic EGF receptors (molecular weight = 170,000). The rates of basal and EGF-stimulated phosphorylation of the receptors were lower in diabetic than in control animals. Insulin treatment of diabetic animals restored the phosphorylation activity to control level, whereas T3 treatment had no apparent effect. There was no significant difference in serum EGF concentration among the control, diabetic and insulin-treated diabetic animals. These results indicate that insulin deficiency in vivo causes a decrease in hepatic EGF receptor number, and suggest that the actions of EGF on hepatocytes may also be affected by diabetes mellitus since the effects of EGF are receptor-mediated.
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PMID:[Effect of experimental diabetes on epidermal growth factor (EGF) receptors in the rat liver]. 253 89

Plasma membranes have been isolated from the human epidermoid carcinoma cell line A431 by a rapid fractionation of lysate on Percoll density gradient at pH 9.6. Endoplasmic reticulum, lysosomes and mitochondria sedimented at the bottom of gradient whereas plasma membranes focused at low density, as shown with specific markers. Plasma membranes displayed a 4.5- and 4.4-fold enrichment in [3H]concanavalin A and 5'-nucleotidase, respectively. This proteic fraction was further characterized by its lipid composition and phospholipid analysis. The cholesterol/phospholipid molar ratio was 0.45 in plasma membranes against 0.19 in lysate. Sphingomyelin increased from 7.5% of total phospholipids in lysate to 16.2% in plasma membranes, as well as phosphatidylserine which displayed a 1.5-fold enrichment in the plasma membrane fraction. This was at the expense of phosphatidylcholine (45.2% in lysate, against 35% in plasma membranes). Electron microscopy of the isolated material showed vesicles essentially free from endoplasmic reticulum and organelles. These plasma membranes retained the ability to bind 125I-labelled epidermal growth factor (125I-EGF) with a Kd = 4.7 nM and Bmax = 63 pmol/mg protein. EGF binding resulted in a stimulation of the phosphorylation protein reaction in the presence of [gamma-32P]ATP and sodium dodecyl sulfate polyacrylamide gels of phosphorylated proteins indicated that the radioactivity of the major band of molecular weight 170,000 was clearly enhanced by EGF binding. These results indicate that the EGF receptor and its intrinsic protein kinase activity were preserved during our plasma membrane isolation procedure.
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PMID:Characterization of plasma membranes from A431 cells, isolated by self-generating Percoll gradient: a rapid isolation procedure to obtain plasma membranes with functional epidermal growth factor receptors. 325 34