PIK3CA encoding the phosphoinositide 3-kinase (PI3K) p110α catalytic subunit is frequently mutated in cancer. The mechanisms underlying PI3K activation on membranes, and how oncogenic mutations distributed throughout p110α increase kinase activity is undefined. Using a synergy of biochemical assays and hydrogen deuterium exchange mass spectrometry (HDX-MS), we reveal unique regulatory mechanisms underlying PI3K activation. Engagement of p110α on membranes leads to disengagement of the ABD domain of p110α from the catalytic core, and the C2 domain from the iSH2 domain of the p85 regulatory subunit. PI3K activation also requires reorientation of the C-terminus, with mutations that alter the inhibited conformation of the C-terminus increasing membrane binding. Mutations at the C-terminus (M1043I/L, H1047R, G1049R, and N1068KLKR) activate p110α through distinct mechanisms, with this having important implications for mutant selective inhibitor development. This work reveals unique mechanisms underlying oncogenic mutants activate PI3K and explains how double mutants can synergistically increase PI3K activity.

中文翻译：

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PIK3CA 的致癌突变导致由 ABD、p85 和 C 末端的重新定向驱动的膜募集增加

编码磷酸肌醇 3-激酶 (PI3K) p110α 催化亚基的 PIK3CA 在癌症中经常发生突变。膜上 PI3K 激活的潜在机制，以及分布在整个 p110α 中的致癌突变如何增加激酶活性尚不明确。通过生化分析和氢氘交换质谱 (HDX-MS) 的协同作用，我们揭示了 PI3K 激活的独特调节机制。p110α 在膜上的结合导致 p110α 的 ABD 结构域与催化核心脱离，C2 结构域与 p85 调节亚基的 iSH2 结构域脱离。PI3K 激活还需要 C 末端的重新定向，突变会改变 C 末端的抑制构象，从而增加膜结合。C 端突变（M1043I/L、H1047R、G1049R、和 N1068KLKR) 通过不同的机制激活 p110α，这对突变选择性抑制剂的开发具有重要意义。这项工作揭示了致癌突变体激活 PI3K 的独特机制，并解释了双突变体如何协同增加 PI3K 活性。