Folliculin, encoded by the tumor suppressor gene FLCN, is associated with the Birt-Hogg-Dubé syndrome, characterized by fibrofolliculomas, spontaneous pneumothorax and kidney tumors, and its binding partners FNIP1/FNIP2 (FLCN interacting proteins) are involved in Rag-mediated amino acid signaling through mTORC1 and play a role in tuning the conversion between active and inactive mTORC1. The gene discussed is FLCN; the disease is Birt-Hogg-Dubé syndrome.