Chaussade Claire, Cho Kitty, Mawson Claire, Rewcastle Gordon W, Shepherd Peter R
Department of Molecular Medicine, University of Auckland, New Zealand.
Biochem Biophys Res Commun. 2009 Apr 17;381(4):577-81. doi: 10.1016/j.bbrc.2009.02.081. Epub 2009 Feb 20.
PIK3CA codes for the p110alpha isoform of class-IA PI 3-kinase and oncogenic mutations in the helical domain and kinase domain are common in several cancers. We studied the biochemical properties of a common helical domain mutant (E545K) and a common kinase domain mutant (H1047R). Both retain the ability to autophosphorylate Ser608 of p85alpha and are also inhibited by a range of PI 3-kinase inhibitors (Wortmannin, LY294002, PI-103 and PIK-75) to a similar extent as WT p110alpha. Both mutants display an increased V(max) but while a PDGF derived diphosphotyrosylpeptide caused an increase in V(max) for WT p85alpha/p110alpha it did not for the E545K variant and actually decreased V(max) for the H1047R variant. Further, the E545K mutant was activated by H-Ras whereas the H1047R mutant was not. Together these results suggest helical domain mutants are in a state mimicking activation by growth factors whereas kinase domain mutants mimic the state activated by H-Ras.
PIK3CA编码IA类PI 3激酶的p110α亚型，螺旋结构域和激酶结构域中的致癌突变在几种癌症中很常见。我们研究了一种常见的螺旋结构域突变体（E545K）和一种常见的激酶结构域突变体（H1047R）的生化特性。两者都保留了对p85α的Ser608进行自身磷酸化的能力，并且也受到一系列PI 3激酶抑制剂（渥曼青霉素、LY294002、PI-103和PIK-75）的抑制，抑制程度与野生型p110α相似。两种突变体都表现出V(max)增加，但虽然源自血小板衍生生长因子（PDGF）的双磷酸化酪氨酸肽会使野生型p85α/p110α的V(max)增加，但对E545K变体却没有这种作用，实际上对H1047R变体反而降低了V(max)。此外，E545K突变体被H-Ras激活，而H1047R突变体则未被激活。这些结果共同表明，螺旋结构域突变体处于一种模拟生长因子激活的状态，而激酶结构域突变体则模拟被H-Ras激活的状态。
