In proxy re-encryption schemes, a proxy is given special information that allows it to translate a ciphertext under one key into a ciphertext of the same message under a different key.
How practical is PRE? Is it possible for achieving PRE for AES?
Proxy re-encryption schemes are entirely practical. This is certainly true for AES symmetric encryption, as the proxy does little more than decryption with key 1, followed by encryption with key 2. This is called the "Naïve Way" in this lecture.
Now if PRE is suitable for a specific uses case is an entirely different matter. It depends on how secure the proxy itself is. If you require additional security in the PRE protocol itself you may have to go for a protocol that uses asymmetric encryption primitives.
Beware that a proxy more or less implies communication over insecure networks. If man-in-the-middle attacks are applicable then you should add an authentication tag to your messages.
More detail is required to answer your question for a specific use case.
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Conversion and Proxy Functions for Symmetric Key Ciphers By Cook and Keromytis has conversion techniques that seems to be practical for achieving PRE .