A lion is a symbol for good and evil, sun, splendor, power, majesty, courage, justice, king; cruelty; ferocity. it can also be a maternal symbol.
Many civilizations have legends of lion or cat people. These may refer to an actual humanoid cat like race from the Constellation of Lyra. Therefore, a cat or lion can be used as a symbol for the Lyrans. This is consistent with ancient myths that tell of fights between serpents and lions, cats or eagles, which is a symbolic representation of the fights between Sirians, depicted as serpents, and Lyrans, depicted as eagles or cats. (See: Earth's Galactic History for more information).
Note that at least two authors, though, refer to Sirius as the origin of the lion and / or cat people, while yet another one refers to Regulus.