Signal Transduction of Unique RAS Family Member towards Cell Survival

Small GTPases of RAS act as central regulators of intracellular signal transduction and translate external stimuli to the various cellular responses. Embryonic stem cell expressed RAS (ERAS) is a member of the RAS family that is specifically expressed in undifferentiated mouse embryonic stem cells, hepatic stellate cells and diverse human tumors, such as gastric, breast, brain, pancreatic, and colorectal tumors. Although ERAS belongs to GTPase family, it is an inefficient enzyme to hydrolyze GTP to GDP. Therefore, it remains mainly in its GTP-bound active form and contributes to sustained signal transduction. In comparison with classical members (HRAS, NRAS and KRAS4B), ERAS is known as a unique member, due to its temporal expression, remarkable amino acid sequence deviations and functional differences. Notably, ERAS has been recently proposed as a potential marker for drug resistance in several human tumors. In this minireview, I compare in great detail the biochemical properties of ERAS with conventional members of the RAS family, and discuss the main ERAS function in the control of the PI3K-AKT-mTORC survival pathway. Targeting this pathway may sensitize ERAS expressing cell populations to chemotherapy.