title: A frequent kinase domain mutation that changes the interaction between PI3Kalpha and the membrane.
abstract: Mutations in oncogenes often promote tumorigenesis by changing the conformation of the encoded proteins, thereby altering enzymatic activity. The PIK3CA oncogene, which encodes p110alpha, the catalytic subunit of phosphatidylinositol 3-kinase alpha (PI3Kalpha), is one of the two most frequently mutated oncogenes in human cancers. We report the structure of the most common mutant of p110alpha in complex with two interacting domains of its regulatory partner (p85alpha), both free and bound to an inhibitor (wortmannin). The N-terminal SH2 (nSH2) domain of p85alpha is shown to form a scaffold for the entire enzyme complex, strategically positioned to communicate extrinsic signals from phosphopeptides to three distinct regions of p110alpha. 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 p110alpha 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.
authors.affiliation: The Ludwig Center for Cancer Genetics and Therapeutics and Howard Hughes Medical Institute, Johns Hopkins Kimmel Cancer Center, Baltimore, MD 21231, USA.
authors.forename: Diana
authors.initials: D
authors.lastname: Mandelker
authors.forename: Sandra B
authors.initials: SB
authors.lastname: Gabelli
authors.forename: Oleg
authors.initials: O
authors.lastname: Schmidt-Kittler
authors.forename: Jiuxiang
authors.initials: J
authors.lastname: Zhu
authors.forename: Ian
authors.initials: I
authors.lastname: Cheong
authors.forename: Chuan-Hsiang
authors.initials: CH
authors.lastname: Huang
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Kinzler
authors.forename: Bert
authors.initials: B
authors.lastname: Vogelstein
authors.forename: L Mario
authors.initials: LM
authors.lastname: Amzel
mesh_terms: D000730:Androstadienes / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D020134:Catalytic Domain / Q000235:genetics; D002460:Cell Line; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D058534:Class I Phosphatidylinositol 3-Kinases; D003460:Crystallization; D045325:HCT116 Cells; D006801:Humans; D006860:Hydrogen Bonding; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D047428:Protein Kinase Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D018411:Spodoptera; D000077191:Wortmannin; D014961:X-Ray Diffraction
chemical_list: D000730:Androstadienes; D007527:Isoenzymes; D047428:Protein Kinase Inhibitors; D011994:Recombinant Proteins; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; D000077191:Wortmannin