The guitarist quit the band in 2010 after finishing work on their self-titled fourth album, and he has since retrained as an actor.
Dengler has now revealed there were many reasons why he left Interpol, including his long-running struggle with substance abuse, but he finally made the decision to quit while watching Chris Martin's band play a lacklustre set on TV sketch show Saturday Night Live.
He tells BedfordandBowery.com, "I think the moment for me, and it's funny to think that this is the occasion for it, but when Coldplay - our old manager was Coldplay's manager - played Saturday Night Live, he offered us tickets.
"And when I felt so much titillation and excitement over all the skits - Jon Hamm was the host - and looking at how they were being performed. And then when Coldplay came on, I felt bored, quite frankly. I knew then that there was something going on with me, some kind of identity shift, really. It really troubled me."