A gas turbine engine having an electric generator includes a transmission shaft extending along a longitudinal axis of the engine and drivingly interconnecting a turbine shaft of the engine and a rotor shaft of the electric generator. The transmission shaft is engaged by splined mating connections with the turbine shaft and the rotor shaft. The transmission shaft has a shear neck defining a reduced radial wall thickness with respect to a remainder of the transmission shaft such as to provide a weakened region of the transmission shaft. An annular support structure, concentric with and surrounding the transmission shaft, is axially located between the shear neck and a forward end of the transmission shaft engaged to the turbine shaft, and includes a bearing operable to rotationally support the transmission shaft.