FNIP2 is the second protein found to interact with folliculin, the product of the Birt-Hogg-Dube (BHD) gene. Folliculin is thought to act as a tumor suppressor as mutations or loss of heterozygosity in this gene are associated with BHD syndrome-related renal tumors. Folliculin and FNIP1, a protein that shares 49% identity to FNIP2, bind to AMPK, an important energy sensor in cells that negatively regulates the mammalian target of rapamycin (mTOR), a protein that is thought to be the master switch for cell growth and proliferation. FNIP1 and FNIP2 are able to form homo- and heteromeric multimers, suggesting these proteins may have a functional relationship.