The Golden Throne's effect applies any time you would lose the game while it is on the battlefield, even if you're not losing due to your life total being 0 or less. If you would have lost the game because you tried to draw from an empty library, your life total becomes 1 and you won't lose again until you try to draw again and still can't do so. If you would have lost the game due to having ten or more poison counters, your life total becomes 1, but you will lose the game immediately afterward because you still have ten or more poison counters.