Oyonnax flanker Pedrie Wannenburg will be the first non-American player to play in new USA league.
The French side have agreed to an early release for Wannenburg's, his contract with the French club terminates at the end of 2016. The back rower will be joining the Denver Rugby Franchise.
The former Springbok achieved great success with the Bulls winning three Super Rugby trophies during his time with the Pretoria side.
"I believe I have a lot to offer in a country where rugby is the fastest growing team sport," Wannenburg told Rapport.
"The interest is great – the team in Denver gets daily emails from players and coaches who are interested. In America everything is indeed bigger and better."
The 35 year old believes that he has a season or two left in the tank.
"I’ve got a five-year visa and I plan to play for two more seasons before getting involved in coaching."
The PRO will consist of five franchises, with Denver being the fifth confirmed team.
These franchises are: Sacramento, San Francisco, San Diego, Ohio and Denver
The tournament kicks off in April and will run through until July, this year.