Functional differences between two classes of oncogenic mutation in the PIK3CA gene.
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.
Chaussade
Claire
C
Department of Molecular Medicine, University of Auckland, New Zealand.
Cho
Kitty
K
Mawson
Claire
C
Rewcastle
Gordon W
GW
Shepherd
Peter R
PR
D058534:Class I Phosphatidylinositol 3-Kinases; D006801:Humans; D009154:Mutation; D009369:Neoplasms / Q000235:genetics*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017433:Protein Structure, Secondary / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics
D058534:Class I Phosphatidylinositol 3-Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; C484760:PIK3CA protein, human