My son's a PLME and I think the requirements changed beginning with last year's class. You can find the details on PLME website under academic handbook. In general, you need to take so many "pre-req" classes to show competency in Bio, Chem, Physics and Math (also social sciences, behavioral sciences and writing). Brown does not require a specific GPA but "satisfactory" progress is expected. For instance, you are required to take 3 bio courses (2 if skipping the intro class, the other two you get to choose) and get an A or B in them. Although you don't need to maintain a "3.0", Brown can issue academic warnings and probation. I just don't know the particulars.
If you go to Brown's PLME website, you can find all the details.
http://bms.brown.edu/plme/handbook/P...ss_of_2011.pdf
For other info about PLME:
Brown Program in Liberal Medical Education