Phosphatome profiling reveals PTPN2, PTPRJ and PTEN as potent negative regulators of PKB/Akt activation in Ras mutated cancer cells

Jasminka Omerovic , Michael J. Clague , Ian A. Prior (1)

1 The Physiological Laboratory

Oncogenic Ras mutations render the protein constitutively active and promote tumourigenisis via chronic stimulation of effector pathways. In A549 lung adenocarcinoma approximately 50% of the total Ras population is constitutively active yet these cells display only weak activation of the effectors: ERK1/2 and Akt. In order to identify key negative regulators of oncogenic Ras signalling we performed a phosphatome RNAi screen in A549 cells and ranked their effects on phosphorylation of Ser473 of Akt. As expected, the tumour suppressor PTEN emerged as a leading hit – knockdown elevated Akt activation to 70% of maximal generated by acute EGF stimulation. Importantly, we identified other phosphatases with similar potencies including PTPN2 (TC-PTP) and PTPRJ (DEP-1/CD148). Potentiation of Akt phosphorylation by knockdown of PTEN or PTPRJ was contingent on the presence of oncogenic K-Ras. Our data reveal a synergy between oncogene function and the loss of a tumour suppressor within the same pathway that was necessary for full effector activation since each alone failed to elicit significant Akt phosphorylation. Together, these data reveal potent regulators of Akt signalling that contribute to ameliorating the consequences of oncogenic K-Ras activity.

Mots clés: Life Sciences

Jasminka Omerovic, Michael J. Clague, Ian A. Prior. Phosphatome profiling reveals PTPN2, PTPRJ and PTEN as potent negative regulators of PKB/Akt activation in Ras mutated cancer cells. Biochemical Journal, 2010, 426 (1), pp.65-72. ⟨10.1042/BJ20091413⟩. ⟨hal-00479254⟩