Fig. 1: Structural insights into PI3Kα activation by small-molecule activator 1938 and cancer-specific mutation H1047R.
a Cryo-EM density map and corresponding atomic model for PI3Kα in complex with 1938 (highlighted in green). b Compound 1938 dose-dependently activates wild-type (WT) PI3Kα with an EC50 value of 3.4 μM. c Representative SPR sensorgram of 1938 binding to PI3Kα WT with a KD value of 253 ± 69 μM. d A surface representation comparing the binding pose of 1938 in cryo-EM (green) and X-ray crystallography (purple) within PI3Kα. e, f Structural (e) and schematic (f) representation of the interactions between 1938 and PI3Kα in the cryo-EM structure. Residues involved in 1938 recognition are shown as sticks. g Interaction network at the interface among the iSH2, ABD, and C2 domains is disrupted in the 1938-bound structure (bottom) compared to the unliganded PI3Kα (PDB ID: 7MYN, top). h Distribution of the interface area between p110α and p85α (left), and between ABD and the p110α without ABD (right), from the last 500 ns of MD simulation trajectories, calculated by FreeSASA 2.0. i Cryo-EM density map and corresponding atomic model for the 1938-bound H1047R complex, shown in two orientations. The EM density of 1938 is shown as a mesh. j Compound 1938 activates PI3Kα/AKT signaling in breast cancer cells. SKBR3 (PIK3CAWT) and T-47D (PIK3CAH1047R) cells were treated with the indicated concentrations of 1938 for 5 min at 37 °C. Western blot analysis shows dose-dependent upregulation of pAKT (S473) following 1938 treatment (left). GAPDH: loading control. Bar graphs show densitometric analysis of pAKT (S473) and GAPDH (mean ± SEM, n = 3) (right). k Conformational comparison of F1016 (left) and the activation loop (right) between 1938-bound H1047R and 1938-bound WT PI3Kα structures. l The interaction network at the p110α–p85α interface is further disrupted in the 1938-bound H1047R structure (top) compared to the unliganded H1047R (bottom).
