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)

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

Extracellular ATP, when added as a single dose at concentrations higher than 0.1 mM to the culture medium, was growth inhibitory or even cytotoxic for human epidermoid carcinoma cells (A431). Adenosine at the same concentrations was much less potent. The molecular mechanism underlying the inhibitory effect of extracellular ATP has been investigated. The cytostatic as well as the cytotoxic effects of ATP could be prevented by supplying uridine as a pyrimidine source and, alternatively, by simultaneous addition of dipyridamole, which inhibits the uptake of adenosine. The data suggest that the long-term production and continuous uptake of adenosine, which is enzymatically generated from the ATP in the medium, led to an intracellular nucleotide imbalance with pyrimidine starvation. This triggered suicidal processes ending up in apoptosis of the cells. The tumor cells have been adapted to extracellular ATP with the aim to obtain cells which are more resistant to ATP. Therefore, growing cells were periodically treated with extracellular ATP. These cells were characterized by an enlargement of cell size, a decreased proliferation rate, and a reduced but not abolished sensitivity to cytostatic and cytotoxic ATP doses. The calcium response of adapted cells was shortened. The nucleotide hydrolyzing ectoenzyme activities (ecto-ATPase, ecto-ADPase, ecto-AMPase, ecto-Ap4Aase) were simultaneously upregulated. All phenotypic alterations of the adapted cells disappeared after cultivation for several generations in the absence of extracellular ATP. Considering ATP as a potential chemotherapeutic agent the adaptive phenomena of treated cells might be important.
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PMID:Nucleotide metabolizing ectoenzymes are upregulated in A431 cells periodically treated with cytostatic ATP leading to partial resistance without preventing apoptosis. 973 53

Esophageal cancer is an aggressive tumor and is the sixth leading cause of cancer death worldwide. ATP is well known to regulate cancer progression in a variety of models by different mechanisms, including P2X7R activation. This study aimed to evaluate the role of P2X7R in esophageal squamous cell carcinoma (ESCC) proliferation. Our results show that treatment with high ATP concentrations induced a decrease in cell number, cell viability, number of polyclonal colonies, and reduced migration of ESCC. The treatment with the selective P2X7R antagonist A740003 or siRNA for P2X7 reverted this effect in the KYSE450 cell line. In addition, results showed that P2X7R is highly expressed, at mRNA and protein levels, in KYSE450 lineage. Additionally, KYSE450, KYSE30, and OE21 cells express P2X3R, P2X4R, P2X5R, P2X6R, and P2X7R genes. P2X1R is expressed by KYSE30 and KYSE450, and only KYSE450 expresses the P2X2R gene. Furthermore, esophageal cancer cell line KYSE450 presented higher expression of E-NTPDases 1 and 2 and of Ecto-5'-NT/CD73 when compared to normal cells. This cell line also exhibits ATPase, ADPase, and AMPase activity, although in different levels, and the co-treatment of apyrase was able to revert the antiproliferative effects of ATP. Moreover, results showed high immunostaining for P2X7R in biopsies of patients with esophageal carcinoma, indicating the involvement of this receptor in the growth of this type of cancer. The results suggest that P2X7R may be a potential pharmacological target to treat ESCC and can lead us to further investigate the effect of this receptor in cancer cell progression.
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PMID:Potential role of P2X7R in esophageal squamous cell carcinoma proliferation. 2839 10