A frequent kinase domain mutation that changes the interaction between PI3Kα and the membrane

doi:10.1073/pnas.0908444106

A frequent kinase domain mutation that changes the interaction between PI3Kα and the membrane

^aThe Ludwig Center for Cancer Genetics and Therapeutics and Howard Hughes Medical Institute, Johns Hopkins Kimmel Cancer Center, Baltimore, MD 21231; and
^bDepartment of Biophysics and Biophysical Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205

↵³Present address: Department of Cell Biology, The Johns Hopkins University, Baltimore, MD 21205.

Contributed by Bert Vogelstein, August 5, 2009
↵¹D.M. and S.B.G. contributed equally to this work. (received for review July 13, 2009)

Abstract

Mutations in oncogenes often promote tumorigenesis by changing the conformation of the encoded proteins, thereby altering enzymatic activity. The PIK3CA oncogene, which encodes p110α, the catalytic subunit of phosphatidylinositol 3-kinase alpha (PI3Kα), is one of the two most frequently mutated oncogenes in human cancers. We report the structure of the most common mutant of p110α in complex with two interacting domains of its regulatory partner (p85α), both free and bound to an inhibitor (wortmannin). The N-terminal SH2 (nSH2) domain of p85α is shown to form a scaffold for the entire enzyme complex, strategically positioned to communicate extrinsic signals from phosphopeptides to three distinct regions of p110α. Moreover, we found that Arg-1047 points toward the cell membrane, perpendicular to the orientation of His-1047 in the WT enzyme. Surprisingly, two loops of the kinase domain that contact the cell membrane shift conformation in the oncogenic mutant. Biochemical assays revealed that the enzymatic activity of the p110α His1047Arg mutant is differentially regulated by lipid membrane composition. These structural and biochemical data suggest a previously undescribed mechanism for mutational activation of a kinase that involves perturbation of its interaction with the cellular membrane.

Footnotes

²To whom correspondence may be addressed. E-mail: gabelli{at}jhmi.edu, vogelbe{at}jhmi.edu, and mamzel{at}jhmi.edu
Author contributions: S.B.G., K.W.K., B.V., and L.M.A. designed research; D.M., O.S.-K., J.Z., I.C., and C.-H.H. performed research; J.Z. contributed new reagents/analytic tools; D.M., S.B.G., O.S.-K., K.W.K., B.V., and L.M.A. analyzed data; and D.M., S.B.G., B.V., and L.M.A. wrote the paper.
Conflict of interest statement: The authors declare a conflict of interest (such as defined by PNAS policy). Under agreements between The Johns Hopkins University and various commercial entities, K.W.K. and B.V. are entitled to a share of the royalties received by The Johns Hopkins University on sales of products related to the diagnosis of mutant PIK3CA genes. The terms of these arrangements are being managed by The Johns Hopkins University in accordance with its conflict of interest policies.
Data deposition: The atomic coordinates of the p110α His1047Arg/niSH2 enzyme, both free and in complex with wortmannin, have been deposited in the Protein Data Bank (PDB ID codes 3HIZ and 3HHM).
This article contains supporting information online at www.pnas.org/cgi/content/full/0908444106/DCSupplemental.