Yes, PIE is a Scrabble word!

Letter values in Scrabble US: P 3, I 1, E 1.

Is it a valid word?

PIE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

dish baked in pastry-lined pan often with a pastry top
a prehistoric unrecorded language that was the ancestor of all Indo-European languages

Also: proto-indo european.