Aims

Mutations in PIK3CA, which encodes p110α subunit of PI3K class IA enzymes, are highly frequent in breast cancer. Here, we aimed to probe mutations in exon 9 of PIK3CA and computationally simulate their function.

Materials and methods

PCR/HRM and PCR/sequencing were used for mutation detection in 40 breast cancer specimens. The identified mutations were queried via in silico algorithms to check the pathogenicity. The molecular dynamics (MD) simulations were utilized to assess the function of mutant proteins.

Key findings

Three samples were found to harbor at least one of the E542K, E545K and L551Q mutations of which L551Q has not been reported previously. All mutations were confirmed to be pathogenic and MD simulations revealed their impact on protein function and regulation. The novel L551Q mutant dynamics was similar to that of previously found carcinogenic mutants, E542K and E545K. A functional role for the helical domain was also suggested by which the inhibitory signal of p85α is conducted to kinase domain via helical domain. Helical domain mutations lead to impairment of kinase domain allosteric regulation. Interestingly, our results show that p110α substrate binding pocket of kinase domain in mutants may have differential affinity for enzyme substrates, including anit-p110α drugs.

Significance

The novel p110α L551Q mutation could have carcinogenic feature similar to previously known helical domain mutations.

中文翻译：

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新的致癌PI3Kα突变提示螺旋结构域在将nSH2调节信号传递至激酶结构域中的作用

目的

编码PI3K IA类酶p110α亚基的PIK3CA中的突变在乳腺癌中非常常见。在这里，我们旨在探测PIK3CA外显子9中的突变，并通过计算模拟其功能。

材料和方法

PCR / HRM和PCR /测序用于40个乳腺癌标本的突变检测。通过计算机模拟算法查询已鉴定的突变，以检查其致病性。分子动力学（MD）模拟用于评估突变蛋白的功能。

主要发现

发现三个样品含有E542K，E545K和L551Q突变中的至少一种，以前没有报道过L551Q。证实所有突变都是致病性的，MD模拟显示它们对蛋白质功能和调节的影响。新的L551Q突变体动力学与先前发现的致癌突变体E542K和E545K相似。还提出了螺旋结构域的功能性作用，其中p85α的抑制信号通过螺旋结构域传导至激酶结构域。螺旋结构域突变导致激酶结构域变构调节受损。有趣的是，我们的结果表明，突变体中激酶结构域的p110α底物结合口袋可能对酶底物（包括anit-p110α药物）具有不同的亲和力。

意义

新的p110αL551Q突变可能具有类似于先前已知的螺旋结构域突变的致癌特征。