Safoura Ghalamkari1, Shahryar Alavi2, Hamidreza Mianesaz1, Farinaz Khosravian3, Amir Bahreini4, Mansoor Salehi5. 1. Department of Genetics and Molecular Biology, Isfahan University of Medical Sciences, Isfahan, Iran. 2. Department of Cell and Molecular Biology & Microbiology, Faculty of Biological Science and Technology, University of Isfahan, Isfahan, Iran. 3. Cellular, Molecular and Genetics Research Center, Isfahan University of Medical Sciences, Isfahan, Iran; Medical Genetics Research Center of Genome, Isfahan University of Medical Sciences, Isfahan, Iran. 4. Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, PA, USA; KaryoGen, Isfahan, Iran. Electronic address: bahreini_amir@palinlab.com. 5. Department of Genetics and Molecular Biology, Isfahan University of Medical Sciences, Isfahan, Iran; Cellular, Molecular and Genetics Research Center, Isfahan University of Medical Sciences, Isfahan, Iran; Medical Genetics Research Center of Genome, Isfahan University of Medical Sciences, Isfahan, Iran. Electronic address: m_salehi@med.mui.ac.ir.
Abstract
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.
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.