Nah, mate. PGP signatures and Bitcoin private keys are different things.

PGP (Pretty Good Privacy) is used for encrypting and decrypting texts, emails, files - that sort of thing. It uses a pair of keys: one public, one private. You use your private key to sign stuff and others use your public key to verify it's really you.

Bitcoin private keys are also part of a pair (the other being your Bitcoin address), but they're used for making transactions on the blockchain.

So while they both involve cryptography and key pairs, they're used in different ways for different things. Apples and oranges!