Carson Jeffrey D, Van Aller Glenn, Lehr Ruth, Sinnamon Robert H, Kirkpatrick Robert B, Auger Kurt R, Dhanak Dashyant, Copeland Robert A, Gontarek Richard R, Tummino Peter J, Luo Lusong
Department of Enzymology and Mechanistic Pharmacology, GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, PA 19426, USA.
Biochem J. 2008 Jan 15;409(2):519-24. doi: 10.1042/BJ20070681.
The PIK3CA gene, encoding the p110alpha catalytic subunit of Class IA PI3Ks (phosphoinositide 3-kinases), is frequently mutated in many human tumours. The three most common tumour-derived alleles of p110alpha, H1047R, E542K and E545K, were shown to potently activate PI3K signalling in human epithelial cells. In the present study, we examine the biochemical activity of the recombinantly purified PI3K oncogenic mutants. The kinetic characterizations of the wt (wild-type) and the three 'hot spot' PI3K mutants show that the mutants all have approx. 2-fold increase in lipid kinase activities. Interestingly, the phosphorylated IRS-1 (insulin receptor substrate-1) protein shows activation of the lipid kinase activity for the wt and H1047R but not E542K and E545K PI3Kalpha, suggesting that these mutations represent different mechanisms of lipid kinase activation and hence transforming activity in cancer cells.
编码IA类磷脂酰肌醇3激酶（PI3K）p110α催化亚基的PIK3CA基因在许多人类肿瘤中经常发生突变。p110α的三种最常见的肿瘤衍生等位基因H1047R、E542K和E545K，已显示在人上皮细胞中能有效激活PI3K信号传导。在本研究中，我们检测了重组纯化的PI3K致癌突变体的生化活性。野生型（wt）和三种“热点”PI3K突变体的动力学特征表明，这些突变体的脂质激酶活性均约增加了2倍。有趣的是，磷酸化的胰岛素受体底物1（IRS-1）蛋白显示野生型和H1047R的脂质激酶活性被激活，但E542K和E545K的PI3Kα则未被激活，这表明这些突变代表了脂质激酶激活的不同机制，从而也代表了癌细胞中的转化活性。
