James Gandolfini, best known for his role as an anxiety-ridden mob boss on HBO’s “The Sopranos,” died in Italy, possibly of a heart attack, an HBO spokeswoman and the actor’s managers said Wednesday. He was 51. Gandolfini was on holiday in Rome, said Mara Mikialian, HBO’s vice president for program publicity. The actor was scheduled to make an appearance at the Taormina Film Fest in Sicily this week, according to the festival. Gandolfini won three Emmy Awards for his portrayal of Tony Soprano, the angst-ridden mob boss who visited a therapist and took Prozac while knocking off people. “The Sopranos” aired from 1999 to 2007.