All Hail Megatron, Spotlight: Drift, 2 issues of the ongoing..... I believe he was originally in All Hail Megatron.
Showed up in All Hail Megatron for the issues where they were on Cybertron. Later got a Spotlight to explain how he joined Kup's crew and ended up with them on Cybertron, which also explained how Perceptor changed so much and hinted at his origins. His next major appearance is in his own miniseries which will go into more detail about his origins. He was also in the Robot Heroes "I am Optimus Prime!" book.