Conversation so far:
What title did Brock Lesnar win in 2008?
In November 2008, Brock Lesnar defeated Randy Couture to become the UFC Heavyweight Champion.
When did Brock Lesnar lose the UFC Heavyweight Champion title?
Brock Lesnar was defeated by Cain Velasquez for the title by TKO in the first round on October 23 at the Honda Center in Anaheim, California at UFC 121.
When did Brock Lesnar retire?
Brock Lesnar retired from MMA, mentioning his struggles with diverticulitis after UFC 141 on December 30 2011 in Las Vegas against former Strikeforce heavyweight champion Alistair Overeem.
Is Brock Lesnar still with the WWE?

Question: What name did he go by when fighting for the WWE?
Self-contained rewrite: What name did Brock Lesnar go by when fighting for the WWE?