The activity of cyclin-dependent kinase 2 (CDK2) is essential for progression of cells from G 1 to the S phase of the mammalian cell cycle. CVT-313 is a potent CDK2 inhibitor, which was identified from a purine analog library with an IC 50 of 0.5 M in vitro. Inhibition was competitive with respect to ATP (K i ؍ 95 nM), and selective CVT-313 had no effect on other, nonrelated ATP-dependent serine/threonine kinases. When added to CDK1 or CDK4, a 8.5-and 430-fold higher concentration of CVT-313 was required for half-maximal inhibition of the enzyme activity. In cells exposed to CVT-313, hyperphosphorylation of the retinoblastoma gene product was inhibited, and progression through the cell cycle was arrested at the G 1 /S boundary. The growth of mouse, rat, and human cells in culture was also inhibited by CVT-313 with the IC 50 for growth arrest ranging from 1.25 to 20 M. To evaluate the effects of CVT-313 in vivo, we tested this agent in a rat carotid artery model of restenosis. A brief intraluminal exposure of CVT-313 to a denuded rat carotid artery resulted in more than 80% inhibition of neointima formation. These observations suggest that CVT-313 is a promising candidate for evaluation in other disease models related to aberrant cell proliferation.Cell cycle progression in mammalian cells is regulated by a family of cyclin-dependent protein kinases (CDKs), 1 that include CDK1, CDK2, CDK3, CDK4, and CDK6 (1). CDK2 is a serine/threonine kinase whose activity is essential for the G 1 to S transition during cell division. A number of proteins have been shown to be substrates for CDK2 phosphorylation, and among them are the retinoblastoma gene product (Rb) and other related pocket proteins, members of the E2F transcription factor family, cyclin E, and members of the CDK inhibitory proteins. It is also postulated that CDK2 phosphorylates and regulates proteins involved in DNA replication (2, 3). Two lines of evidence suggest that CDK2 activity is essential for cell proliferation; microinjection of antibodies directed against CDK2 blocks the progression of human diploid fibroblasts into S phase (4, 5), and overexpression of a dominant negative mutant of CDK2 in human osteosarcoma cells has a similar effect (6). The crucial role of CDK2 in controlling cell cycle progression suggests that CDK2 is an attractive target for treatment of aberrant cell proliferation.Smooth muscle cell proliferation is largely responsible for restenosis following angioplasty (7). A recent study has shown that CDK2 is activated very early after endothelial denudation in the rat carotid artery model of restenosis (8); moreover, antisense oligonucleotides directed against CDK2 were shown to be effective in reducing neointima formation in this model (9, 10). Arguably, the restenosis model can be used as a "proof of principle" for developing CDK2 inhibitors as drug candidates for the treatment of diseases related to aberrant cell proliferation. Olomoucine is a purine analog of ATP and is a specific inhibitor of CDK1 and CDK2 (11). Its potency, ho...
Insulin resistance, an important feature of type 2 diabetes, is manifested as attenuated insulin receptor (IR) signaling in response to insulin binding. A drug that promotes the initiation of IR signaling by enhancing IR autophosphorylation should, therefore, be useful for treating type 2 diabetes. This report describes the effect of a small molecule IR sensitizer, TLK16998, on IR signaling. This compound activated the tyrosine kinase domain of the IR -subunit at concentrations of 1 mol/l or less but had no effect on insulin binding to the IR ␣-subunit even at much higher concentrations. TLK16998 alone had no effect on IR signaling in mouse 3T3-L1 adipocytes but, at concentrations as low as 3.2 mol/l, enhanced the effects of insulin on the phosphorylation of the IR -subunit and IR substrate 1, and on the amount of phosphatidylinositol 3-kinase that coimmunoprecipitated with IRS-1. Phosphopeptide mapping revealed that the effect of TLK16998 on the IR was associated with increased tyrosine phosphorylation of the activation loop of the -subunit tyrosine kinase domain. TLK16998 also increased the potency of insulin in stimulating 2-deoxy-D-glucose uptake in 3T3-L1 adipocytes, with a detectable effect at 8 mol/l and a 10-fold increase at 40 mol/l. In contrast, only small effects were observed on IGF-1-stimulated 2-deoxy-D-glucose uptake. In diabetic mice, TLK16998, at a dose of 10 mg/kg, lowered blood glucose levels for up to 6 h. These results suggest, therefore, that small nonpeptide molecules that directly sensitize the IR may be useful for treating type 2 diabetes. Diabetes 50: 824 -830, 2001
The individual enantiomers 8 and 12 of the potent and highly selective racemic A1-adenosine antagonist 1,3-dipropyl-8-[2-(5,6-epoxynorbornyl)]xanthine (ENX, 4) were synthesized utilizing asymmetric Diels-Alder cycloadditions for the construction of the norbornane moieties. The absolute configuration of 12 was determined by X-ray crystallography of the 4-bromobenzoate 14, which was derived from the bridged secondary alcohol 13. The latter was obtained from 12 by an acid-catalyzed intramolecular rearrangement. The binding affinities of the enantiomers 8 and 12 and the racemate 4 at guinea pig, rat, and cloned human A1- and A2a-adenosine receptor subtypes were determined. The S-enantiomer 12 (CVT-124) appears to be one of the more potent and clearly the most A1-selective antagonist reported to date, with K1 values of 0.67 and 0.45 nM, respectively, at the rat and cloned human A1-receptors and with 1800-fold (rat) and 2400-fold (human) subtype selectivity. Both enantiomers, administered intravenously to saline-loaded rats, induced diuresis via antagonism of renal A1-adenosine receptors.
1 The purpose of this study was to compare the pharmacological properties (i.e. the AV nodal depressant, vasodilator, and inotropic e ects) of two AV nodal blocking agents belonging to di erent drug classes; a novel A 1 adenosine receptor (A 1 receptor) agonist, N-(3(R)-tetrahydrofuranyl)-6-aminopurine riboside (CVT-510), and the prototypical calcium channel blocker diltiazem. 2 In the atrial-paced isolated heart, CVT-510 was approximately 5 fold more potent to prolong the stimulus-to-His bundle (S ± H interval), a measure of slowing AV nodal conduction (EC 50 =41 nM) than to increase coronary conductance (EC 50 =200 nM). At concentrations of CVT-510 (40 nM) and diltiazem (1 mM) that caused equal prolongation of S ± H interval (*10 ms), diltiazem, but not CVT-510, signi®cantly reduced left ventricular developed pressure (LVP) and markedly increased coronary conductance. CVT-510 shortened atrial (EC 50 =73 nM) but not the ventricular monophasic action potentials (MAP). 3 In atrial-paced anaesthetized guinea-pigs, intravenous infusions of CVT-510 and diltiazem caused nearly equal prolongations of P ± R interval. However, diltiazem, but not CVT-510, signi®cantly reduced mean arterial blood pressure. 4 Both CVT-510 and diltiazem prolonged S ± H interval, i.e., slowed AV nodal conduction. However, the A 1 receptor-selective agonist CVT-510 did so without causing the negative inotropic, vasodilator, and hypotensive e ects associated with diltiazem. Because CVT-510 did not a ect the ventricular action potential, it is unlikely that this agonist will have a proarrythmic action in ventricular myocardium.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.