Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.26 (GSK)
 6,788 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The A3 adenosine receptor, A3AR, belongs to the family of Gi proteins, which upon induction, suppresses the formation of cAMP and its downstream effectors. Recent studies have indicated that activation of A3AR by its agonist, IB-MECA, results in growth inhibition of malignant cells. Here we demonstrate the ability of IB-MECA to decrease the levels of protein kinase A, a downstream effector of cAMP, and protein kinase B/Akt in melanoma cells. Examination of glycogen synthase kinase 3beta, GSK-3beta, whose phosphorylation is controlled by protein kinase A and B, showed a substantial decrease in the levels of its phosphorylated form and an increase in total GSK-3beta levels in IB-MECA treated melanoma cells. This observation suggests that the treatment of cells with IB-MECA augments the activity of GSK-3beta in the cells. Evaluation of beta-catenin, a key component of Wnt signaling pathway which, upon phosphorylation by GSK-3beta rapidly ubiquitinates, showed a substantial decrease in its level after IB-MECA treatment. Accordingly, the level of beta-catenin responsive cell growth regulatory genes including c-myc and cyclin D1 was severely declined upon treatment of the cells with IB-MECA. These observations which link cAMP to the Wnt signaling pathway provide mechanistic evidence for the involvement of Wnt pathway via its key elements GSK-3beta and beta-catenin in the anti-tumor activity of A3AR agonists.
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PMID:Evidence for involvement of Wnt signaling pathway in IB-MECA mediated suppression of melanoma cells. 1203 88

Targeting the A3 adenosine receptor (A3AR) by adenosine or a synthetic agonist to this receptor (IB-MECA and Cl-IB-MECA) results in a differential effect on tumor and on normal cells. Both the adenosine and the agonists inhibit the growth of various tumor cell types such as melanoma, colon or prostate carcinoma and lymphoma. This effect is specific and is exerted on tumor cells only. Moreover, exposure of peripheral blood mononuclear cells to adenosine or the agonists leads to the induction of granulocyte colony stimulating factor (G-CSF) production. When given orally to mice, the agonists suppress the growth of melanoma, colon and prostate carcinoma in these animals, while inducing a myeloprotective effect via the induction of G-CSF production. The de-regulation of the Wnt signaling pathway was found to be involved in the anticancer effect. Receptor activation induces inhibition of adenylyl cyclase with a subsequent decrease in the level of protein kinase A and protein kinase B/Akt leading to activation of glycogen synthase kinase-3beta, a key element in the Wnt pathway. The oral bioavailability of the synthetic A3AR agonists, and their induced systemic anticancer and myeloprotective effect, renders them potentially useful in three different modes of treatment: as a stand-alone anticancer treatment, in combination with chemotherapy to enhance its therapeutic index and myelprotection. It is evident that use of the A3AR agonist for increasing the therapeutic index of chemotherapy may also invariably give rise to myeloprotection and vice versa. The A3AR agonists are thus a promising new class of agents for cancer therapy.
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PMID:A3 adenosine receptor as a target for cancer therapy. 1204 54

Activation of the Gi protein-coupled A3 adenosine receptor (A3AR) has been implicated in the inhibition of melanoma cell growth by deregulating protein kinase A and key components of the Wnt signaling pathway. Receptor activation results in internalization/recycling events that play an important role in turning on/off receptor-mediated signal transduction pathways. Thus, we hereby examined the association between receptor fate, receptor functionality, and tumor growth inhibition upon activation with the agonist 1-deoxy-1-[6-[[(3-iodophenyl)-methyl]amino]-9H-purine-9-yl]-N-methyl-beta-D-ribofuranuronamide (IB-MECA). Results showed that melanoma cells highly expressed A3AR on the cell surface, which was rapidly internalized to the cytosol and "sorted" to the endosomes for recycling and to the lysosomes for degradation. Receptor distribution in the lysosomes was consistent with the down-regulation of receptor protein expression and was followed by mRNA and protein resynthesis. At each stage, receptor functionality was evidenced by the modulation in cAMP level and the downstream effectors protein kinase A, glycogen synthase kinase-3beta, c-Myc, and cyclin D1. The A3AR antagonist MRS 1523 counteracted the internalization process as well as the modulation in the expression of the signaling proteins, demonstrating that the responses are A3AR-mediated. Supporting this notion are the in vivo studies showing tumor growth inhibition upon IB-MECA treatment and reverse of this response when IB-MECA was given in combination with MRS 1523. In addition, in melanoma tumor lesions derived from IB-MECA-treated mice, the expression level A3AR and the downstream key signaling proteins were modulated in the same pattern as was seen in vitro. Altogether, our observations tie the fate of A3AR to modulation of downstream molecular mechanisms leading to tumor growth inhibition both in vitro and in vivo.
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PMID:A3 adenosine receptor activation in melanoma cells: association between receptor fate and tumor growth inhibition. 1286 31

Human A3 adenosine receptor (A3AR) agonists have been shown to play important roles in several physiological and pathological processes, including growth inhibition of human cancer cells. On this line, we recently found that a novel adenosine analog, 2-chloro-N6-(3-iodobenzyl)-4'-thioadenosine-5'-N-methyluronamide (thio-Cl-IB-MECA) was a potent human A3AR agonist, and is superior to a known agonist Cl-IB-MECA [Jeong LS, Jin DZ, Kim HO, Shin DH, Moon HR, Gunaga P, et al. J Med Chem 2003;46:3775]. Here, we report that a novel A3AR agonist, thio-Cl-IB-MECA inhibited the growth of human promyelocytic leukemia HL-60 cells by arresting cell cycle and induction of apoptosis. Thio-Cl-IB-MECA induced the cell cycle arrest of G0/G1 in the early time and at lower concentration (up to 25 microM). At higher concentration (50 microM), the apoptotic cell deaths were manifested by observation of the increase of sub-G0 phase of cell cycle distribution, DNA fragmentation and poly(ADP-ribose) polymerase (PARP) cleavage. In addition, the down-regulation of checkpoint protein cyclin D1 and c-myc by thio-Cl-IB-MECA was well correlated with the arrest of cell cycle transition of G1 to S phase. Further study revealed that the growth inhibitory activity of thio-Cl-IB-MECA is also related with the modulation of Wnt signaling pathway. The levels of beta-catenin, phosphorylated forms of GSK-beta and Akt were down-regulated by the treatment of thio-Cl-IB-MECA (10 nM) in a time-dependent manner, providing one of plausible mechanistic evidence for the involvement of the Wnt signaling pathway in the HL-60 cell growth inhibitory effects by thio-Cl-IB-MECA. These results suggest that a novel A3AR agonist, thio-Cl-IB-MECA can down-regulate Wnt signaling, inhibit proliferation and induce apoptosis in HL-60 leukemia cells, and thus provide the possibility of this compound in the potential therapeutic value of the treatment of leukemia.
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PMID:A novel adenosine analog, thio-Cl-IB-MECA, induces G0/G1 cell cycle arrest and apoptosis in human promyelocytic leukemia HL-60 cells. 1605 Nov 94