Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 2Y2, Canada.
Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 2Y2, Canada.
Structure. 2020 Feb 4;28(2):145-156.e5. doi: 10.1016/j.str.2019.11.013. Epub 2019 Dec 9.
The class I phosphoinositide 3-kinases (PI3Ks) are key signaling enzymes composed of a heterodimer of a p110 catalytic subunit and a p85 regulatory subunit, with PI3K mutations being causative of multiple human diseases including cancer, primary immunodeficiencies, and developmental disorders. Mutations in the p85α regulatory subunit encoded by PIK3R1 can both activate PI3K through oncogenic truncations in the iSH2 domain, or inhibit PI3K through developmental disorder mutations in the cSH2 domain. Using a combined biochemical and hydrogen deuterium exchange mass spectrometry approach we have defined the molecular basis for how these mutations alter the activity of p110α/p110δ catalytic subunits. We find that the oncogenic Q572 truncation of PIK3R1 disrupts all p85-inhibitory inputs, with p110α being hyper-activated compared with p110δ. In addition, we find that the R649W mutation in the cSH2 of PIK3R1 decreases sensitivity to activation by receptor tyrosine kinases. This work reveals unique insight into isoform-specific regulation of p110s by p85α.
I 类磷酸肌醇 3-激酶（PI3Ks）是由 p110 催化亚基和 p85 调节亚基组成的异源二聚体的关键信号酶，PI3K 突变是包括癌症、原发性免疫缺陷和发育障碍在内的多种人类疾病的病因。PIK3R1 编码的 p85α 调节亚基的突变可以通过 iSH2 结构域的致癌截断激活 PI3K，也可以通过 cSH2 结构域的发育障碍突变抑制 PI3K。我们使用组合的生化和氘氢交换质谱方法，定义了这些突变如何改变 p110α/p110δ 催化亚基活性的分子基础。我们发现 PIK3R1 的致癌 Q572 截断破坏了所有 p85 抑制输入，与 p110δ 相比，p110α 被过度激活。此外，我们发现 PIK3R1 的 cSH2 中的 R649W 突变降低了对受体酪氨酸激酶激活的敏感性。这项工作揭示了 p85α 对 p110 的同工型特异性调节的独特见解。
