Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.21 (CPT)
 4,580 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Epac1 is a cAMP-stimulated guanine exchange factor that activates Rap1. The protein product of the T cell leukemia 1 (TCL1) proto-oncogene binds to Akt enhancing its kinase activity. TCL1 and Epac promote cellular proliferation because of their activating effects on Akt. Employing macrophages, we have studied the mechanisms whereby these proteins function in the regulation of Akt kinase activity. Cells were treated with 8-CPT-2-O-Me-cAMP, a cAMP analog which acts selectively and specifically via Epac1. Epac1 co-immunoprecipitated with TCL1 in plasma membrane and nuclear fractions of 8-CPT-2-O-Me-cAMP-stimulated macrophages. Interaction of TCL1 and Epac1 was also observed in a [125I]GST-Epac1 pulldown assay. A two-threefold increase in Akt Thr-308 and Akt Ser-473 protein kinase activities and their phosphoprotein levels was observed in TCL1 immunoprecipitates of plasma membranes and nuclei of the treated cells. Elevated Akt Thr-308 protein kinase activity and its phosphoprotein levels were significantly reduced in TCL1 immunoprecipitates of plasma membranes of 8-CPT-2-O-Me-cAMP-treated cells where Epac1 gene expression was silenced. In contrast, Akt Ser-473 protein kinase activity and its phosphoprotein levels were reduced only in plasma membranes. Our studies suggest that a ternary complex of TCL1, Epac1, and Akt forms in activated macrophages both promoting Akt activation and regulating intracellular distribution of Akt.
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PMID:Interaction between TCL1 and Epac1 in the activation of Akt kinases in plasma membranes and nuclei of 8-CPT-2-O-Me-cAMP-stimulated macrophages. 1799 60

cAMP regulates a wide range of processes through its downstream effectors including PKA, and the family of guanine nucleotide exchange factors. Depending on the cell type, cAMP inhibits or stimulates growth and proliferation in a PKA-dependent or independent manner. PKA-independent effects are mediated by PI 3-kinases-Akt signaling and EPAC1 (exchange protein directly activated by cAMP) activation. Recently, we reported PKA-independent activation of the protein kinase Akt as well co-immunoprecipitation of Epac1 with Rap1, p-Akt(Thr-308), and p-Akt(Ser-473) in forskolin-stimulated macrophages. To further probe the role of Epac1 in Akt protein kinase activation and cellular proliferation, we employed the cAMP analog 8-CPT-2-O-Me-cAMP, which selectively binds to Epac1 and triggers Epac1 signaling. We show the association of Epac1 with activated Akt kinases by co-immunoprecipitation and GST-pulldown assays. Silencing Epac1 gene expression by RNA interference significantly reduced levels of Epac1 mRNA, Epac protein, Rap1 GTP, p-ERK1/2, p-B-Raf, p110alpha catalytic subunit of PI 3-kinase, p-PDK, and p-p(70s6k). Silencing Epac1 gene expression by RNA interference also suppressed 8-CPT-2-O-Me-cAMP-upregulated protein and DNA synthesis. Concomitantly, 8-CPT-2-O-Me-cAMP-mediated upregulation of Akt(Thr-308) protein kinase activity and p-Akt(Thr-308) levels was prevented in plasma membranes and nuclei of the cells. In contrast, silencing Epac1 gene expression reduced Akt(Ser-473) kinase activity and p-Akt(Ser-473) levels in plasma membranes, but showed negligible effects on nuclear activity. In conclusion, we show that cAMP-induced Akt kinase activation and cellular proliferation is mediated by Epac1 which appears to function as an accessory protein for Akt activation.
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PMID:The cAMP-activated GTP exchange factor, Epac1 upregulates plasma membrane and nuclear Akt kinase activities in 8-CPT-2-O-Me-cAMP-stimulated macrophages: Gene silencing of the cAMP-activated GTP exchange Epac1 prevents 8-CPT-2-O-Me-cAMP activation of Akt activity in macrophages. 1849 29

Tuberous sclerosis complex 1 (TSC1) inhibits mammalian target of rapamycin (mTOR), a central promotor of cell growth and proliferation. The protein product of the TSC1 gene, hamartin (referred to as TSC1) is known to interact with Polo-like kinase 1 (Plk1) in a cell cycle regulated, phosphorylation-dependent manner. We hypothesized that the p53 target gene, Plk2, is a tumor suppressor, mediating its tumor suppressor function through interactions with TSC1 that facilitate TSC1/2 restraint of mTOR under hypoxic stress. We found that human lung tumor cells deficient in Plk2 grew larger than control tumors, and that Plk2 interacts with endogenous TSC1 protein. Additionally, C-terminal Plk2-GST fusion protein bound both TSC1 and TSC2 proteins. TSC1 levels were elevated in response to Adriamycin and cells transiently overexpressing Plk2 demonstrated decreased phosphorylation of the downstream target of mTOR, ribosomal protein p70S6 kinase during hypoxia. Plk2 levels were inversely correlated with cytoplasmic p70S6K phosphorylation. Plk2 levels did not increase in response to DNA damage (Adriamycin, CPT -11) when HCT 116 and H460 cells were exposed to hypoxia. TSC1-deficient mouse embryonic fibroblasts with TSC1 added back demonstrated decreased S6K phosphorylation, which was further decreased when Plk2 was transiently overexpressed. Interestingly, under normoxia, Plk2 deficient tumor cells demonstrated increased apoptosis in response to various chemotherapeutic agents including CPT -11 but increased resistance to apoptotic death after CPT-11 treatment under hypoxia, and tumor xenografts comprised of these Plk2-deficient cells were resistant to CPT -11. Our results point to a novel Plk2-TSC1 interaction with effects on mTOR signaling during hypoxia, and tumor growth that may enable targeting Plk2 signaling in cancer therapy.
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PMID:The p53 target Plk2 interacts with TSC proteins impacting mTOR signaling, tumor growth and chemosensitivity under hypoxic conditions. 2005 36

Platinum-based cancer drugs, such as cisplatin, are highly effective chemotherapeutic agents used extensively for the treatment of solid tumors. However, their effectiveness is limited by drug resistance, which, in some cancers, has been associated with an overexpression of pi class glutathione S-transferase (GST P1-1), an important enzyme in the mercapturic acid detoxification pathway. Ethacraplatin (EA-CPT), a trans-Pt(IV) carboxylate complex containing ethacrynate ligands, was designed as a platinum cancer metallodrug that could also target cytosolic GST enzymes. We previously reported that EA-CPT was an excellent inhibitor of GST activity in live mammalian cells compared to either cisplatin or ethacrynic acid. In order to understand the nature of the drug-protein interactions between EA-CPT and GST P1-1, and to obtain mechanistic insights at a molecular level, structural and biochemical investigations were carried out, supported by molecular modeling analysis using quantum mechanical/molecular mechanical methods. The results suggest that EA-CPT preferentially docks at the dimer interface at GST P1-1 and subsequent interaction with the enzyme resulted in docking of the ethacrynate ligands at both active sites (in the H-sites), with the Pt moiety remaining bound at the dimer interface. The activation of the inhibitor by its target enzyme and covalent binding accounts for the strong and irreversible inhibition of enzymatic activity by the platinum complex.
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PMID:Studies of glutathione transferase P1-1 bound to a platinum(IV)-based anticancer compound reveal the molecular basis of its activation. 2168 39

Collagen-derived dipeptide prolyl hydroxyproline (Pro-Hyp) is involved in the proliferation and differentiation of various types of cultured cells. To elucidate the mechanism underlying Pro-Hyp actions during osteoblast differentiation, we hypothesized that proteins binding to Pro-Hyp serve to mediate cellular signaling, affecting Runx2 expression. Recently, we performed the characterization of Foxg1, that it enhances Runx2 expression in the presence of Pro-Hyp. Our findings indicate that Pro-Hyp directly binds to the Foxg1 recombinant protein, which leads to the structural alteration of the Foxg1 protein. In addition, Foxg1 appears to interact with Runx2 in the absence of Pro-Hyp, with Pro-Hyp disrupting the interaction between Foxg1 and Runx2. Collectively, our results indicate that the Pro-Hyp bound Foxg1 alters the structured conformation of Foxg1, resulting in conformational changes that lead to dissociation from Runx2. These novel findings suggest that during osteoblast differentiation, Pro-Hyp mediates Runx2 activity though directly binding to Foxg1 and increases Runx2 expression. Abbreviations: CPT: collagen peptide; GST: Glutathione S-transferase; PAGE: Polyacrylamide gel electrophoresis; PCR: Polymerase chain reaction; prolyl hydroxyproline: Pro-Hyp.
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PMID:Collagen-derived dipeptide prolyl hydroxyproline directly binds to Foxg1 to change its conformation and inhibit the interaction with Runx2. 3132 84