E-Ras (D5G5J) Rabbit mAb #12575

E-Ras (Embryonic Ras) is a member of the Ras family that includes K-Ras, N-Ras, and H-Ras. E-Ras is expressed in early mouse blastocysts and murine embryonic stem cells and is down-regulated upon differentiation (1). Amino acid substitutions as a result of mutation at three conserved positions in K-, H-, N-, and R-Ras proteins result in constitutive activation of these small GTPases, and oncogenic transformation. Intriguingly, the Eras gene encodes a protein where each of these amino acids are substituted, and so E-Ras is naturally constitutively active. E-Ras is thought to contribute to the tumorigenic potential of mouse ES cells to form teratomas in immunodeficient or isogenic mice (1). Despite the parallels between oncogenic mutated Ras, major differences in signaling exist between H-Ras G12V and E-Ras. While H-Ras G12V highly activates the MAPK pathway, E-Ras cannot bind to Raf1 to activate this pathway. Instead, E-Ras signals through PI3K to activate Akt (1). E-Ras is not expressed in human embryonic stem cells, nor is it is expressed in any adult tissues as found thus far (2). Reports have suggested it may be expressed in several tumor types, including gastric cancer (1,2,3). Researchers have speculated on the role of E-Ras in the early mouse blastocyst. Preimplantation embryos can survive in tissue culture in defined medium until the blastocyst stage without any requirement for serum or growth factors. Preimplantation embryos have a requirement for PI3K signaling, and in the absence of exogenous signals, E-Ras has been suggested to be the effector of this signal transduction (6).