Foukas Lazaros C, Daniele Nathalie, Ktori Chariklia, Anderson Karen E, Jensen Jorgen, Shepherd Peter R
Department of Physiology, National Institute of Occupational Health, 0033 Oslo, Norway.
J Biol Chem. 2002 Oct 4;277(40):37124-30. doi: 10.1074/jbc.M202101200. Epub 2002 Jul 26.
We investigated the effects of methylxanthines on enzymatic activity of phosphoinositide 3-kinases (PI3Ks). We found that caffeine inhibits the in vitro lipid kinase of class I PI3Ks (IC(50) = 75 microm for p110 delta, 400 microm for p110 alpha and p110 beta, and 1 mm for p110 gamma), and theophylline has similar effects (IC(50) = 75 microm for p110 delta, 300 microm for p110 alpha, and 800 microm for p110 beta and p110 gamma) and also inhibits the alpha isoform of class II PI3K (PI3K-C2 alpha) (IC(50) approximately 400 microm). However, four other xanthine derivatives tested (3-isobutyl-1-methylxanthine, 3-propylxanthine, alloxazine, and PD116948 (8-cyclopentyl-1,3-dipropylxanthine)) were an order of magnitude less effective. Surprisingly the triazoloquinazoline CGS15943 (9-chloro-2-(2-furyl)(1,2,d)triazolo(1,5-c)quinazolin-5-amine) also selectively inhibits p110 delta (IC(50) < 10 microm). Caffeine and theophylline also inhibit the intrinsic protein kinase activity of the class IA PI3Ks and DNA-dependent protein kinase, although with a much lower potency than that for the lipid kinase (IC(50) approximately 10 mm for p110 alpha, 3 mm for p110 beta, and 10 mm for DNA-dependent protein kinase). In CHO-IR cells and rat soleus muscle, theophylline and caffeine block the ability of insulin to stimulate protein kinase B with IC(50) values similar to those for inhibition of PI3K activity, whereas insulin stimulation of ERK1 or ERK2 was not inhibited at concentrations up to 10 mm. Theophylline and caffeine also blocked insulin stimulation of glucose transport in CHO-IR cells. These results demonstrate that these methylxanthines are direct inhibitors of PI3K lipid kinase activity but are distinctly less effective against serine kinase activity and thus could be of potential use in dissecting these two distinct kinase activities. Theophylline, caffeine, and CGS15943 may be of particular use in dissecting the specific role of the p110 delta lipid kinase. Finally, we conclude that inhibition of PI3K (p110 delta in particular) is likely explain some of the physiological and pharmacological properties of caffeine and theophylline.
我们研究了甲基黄嘌呤对磷酸肌醇3激酶（PI3Ks）酶活性的影响。我们发现咖啡因可抑制I类PI3Ks的体外脂质激酶活性（p110δ的IC50 = 75 μM，p110α和p110β的IC50 = 400 μM，p110γ的IC50 = 1 mM），茶碱也有类似作用（p110δ的IC50 = 75 μM，p110α的IC50 = 300 μM，p110β和p110γ的IC50 = 800 μM），并且还抑制II类PI3K的α亚型（PI3K-C2α）（IC50约为400 μM）。然而，所测试的其他四种黄嘌呤衍生物（3-异丁基-1-甲基黄嘌呤、3-丙基黄嘌呤、咯嗪和PD116948（8-环戊基-1,3-二丙基黄嘌呤））的效力要低一个数量级。令人惊讶的是，三唑并喹唑啉CGS15943（9-氯-2-(2-呋喃基)(1,2,d)三唑并(1,5-c)喹唑啉-5-胺）也选择性抑制p110δ（IC50 < 10 μM）。咖啡因和茶碱还抑制IA类PI3Ks的内在蛋白激酶活性和DNA依赖性蛋白激酶，尽管其效力远低于对脂质激酶的抑制作用（p110α的IC50约为10 mM，p110β的IC50为3 mM，DNA依赖性蛋白激酶的IC50为10 mM）。在CHO-IR细胞和大鼠比目鱼肌中，茶碱和咖啡因可阻断胰岛素刺激蛋白激酶B的能力，其IC50值与抑制PI3K活性的IC50值相似，而在浓度高达10 mM时，胰岛素对ERK1或ERK2的刺激未受抑制。茶碱和咖啡因还可阻断CHO-IR细胞中胰岛素对葡萄糖转运的刺激作用。这些结果表明，这些甲基黄嘌呤是PI3K脂质激酶活性的直接抑制剂，但对丝氨酸激酶活性的抑制作用明显较弱，因此可能在剖析这两种不同的激酶活性方面具有潜在用途。茶碱、咖啡因和CGS15943在剖析p110δ脂质激酶的特定作用方面可能特别有用。最后，我们得出结论，抑制PI3K（尤其是p110δ）可能解释了咖啡因和茶碱的一些生理和药理特性。
