Dabizas, who had spells with Newcastle United and Leicester City during his playing career, has good connections in the United Kingdom and his club were previously linked with a move for Magpies winger Callum Roberts.
At the time it seemed Roberts would be heading to Greece but their interest in the young attacker has gone quiet in recent weeks.
The 20 year old made the breakthrough with Celtic last season and played 19 games for the Scottish Premiership club, scoring three goals.
It may be unlikely the Hoops will want to let go of the youngster and it could take some persuading from Panathinaikos to land the player.
Johnston is under contract at Celtic Park until June 2023.