tough spot against a brilliant lag

[mike l.]

4 handed 20-40. im on the button w/ A8o. very laggy, tough aggressive high limit pro raises utg. he has been running over the game. i 3 bet. sb folds, bb who is also a very good player but has been losing his mind against utg and spewing with turn 5 bet bluffs calls, utg calls.

the flop is JT5 rainbow, checked to utg who donks, i call, bb calls.

the turn is a K. checked to me and i check.

the river is a 4. bb checks, utg bets, i ???