Rare cancer-specific mutations in PIK3CA show gain of function

M Gymnopoulos, MA Elsliger… - Proceedings of the …, 2007 - National Acad Sciences
M Gymnopoulos, MA Elsliger, PK Vogt
Proceedings of the National Academy of Sciences, 2007National Acad Sciences
Fifteen rare cancer-derived mutants of PIK3CA, the gene coding for the catalytic subunit
p110α of phosphatidylinositol 3-kinase (PI3K), were examined for their biological and
biochemical properties. Fourteen of these mutants show a gain of function: they induce
rapamycin-sensitive oncogenic transformation of chicken embryo fibroblasts, constitutively
activate Akt and TOR-mediated signaling, and show enhanced lipid kinase activity. Mapping
of these mutants on a partial structural model of p110α suggests three groups of mutants …
Fifteen rare cancer-derived mutants of PIK3CA, the gene coding for the catalytic subunit p110α of phosphatidylinositol 3-kinase (PI3K), were examined for their biological and biochemical properties. Fourteen of these mutants show a gain of function: they induce rapamycin-sensitive oncogenic transformation of chicken embryo fibroblasts, constitutively activate Akt and TOR-mediated signaling, and show enhanced lipid kinase activity. Mapping of these mutants on a partial structural model of p110α suggests three groups of mutants, defined by their location in distinct functional domains of the protein. We hypothesize that each of these three groups induces a gain of PI3K function by a different molecular mechanism. Mutants in the C2 domain increase the positive surface charge of this domain and therefore may enhance the recruitment of p110α to cellular membranes. Mutants in the helical domain map to a contiguous surface of the protein and may affect the interaction with other protein(s). Mutants in the kinase domain are located near the hinge of the activation loop. They may alter the position and mobility of the activation loop. Arbitrarily introduced mutations that have no detectable phenotype map either to the interior of the protein or are positioned on a surface region that lies opposite to the exposed surfaces containing gain-of-function mutants. Engineered mutants that exchange acidic or neutral residues for basic residues on the critical surfaces show a gain of function.
National Acad Sciences