Multi-functional protein, involved in both the cellular response to amino acid availability and in the regulation of glycolysis (PubMed:17028174, PubMed:18663353, PubMed:21209915, PubMed:24081491, PubMed:24095279, PubMed:31704029, PubMed:31672913, PubMed:34381247). GTPase-activating protein that plays a key role in the cellular response to amino acid availability through regulation of the mTORC1 signaling cascade controlling the MiT/TFE factors TFEB and TFE3 (PubMed:17028174, PubMed:18663353, PubMed:21209915, PubMed:24081491, PubMed:24095279, PubMed:31704029, PubMed:31672913). Regulates glycolysis by binding to lactate dehydrogenase LDHA, acting as an uncompetitive inhibitor (PubMed:34381247). Activates mTORC1 by acting as a GTPase-activating protein: specifically stimulates GTP hydrolysis by RRAGC/RagC or RRAGD/RagD, promoting the conversion to the GDP-bound state of RRAGC/RagC or RRAGD/RagD, and thereby activating the kinase activity of mTORC1 (PubMed:24095279, PubMed:31704029, PubMed:31672913). The GTPase-activating activity is inhibited during starvation and activated in presence of nutrients (PubMed:31672913). Acts as a key component for mTORC1-dependent control of the MiT/TFE factors TFEB and TFE3, while it is not involved in mTORC1-dependent phosphorylation of canonical RPS6KB1/S6K1 and EIF4EBP1/4E-BP1 (PubMed:21209915, PubMed:24081491, PubMed:31672913). In low-amino acid conditions, the lysosomal folliculin complex (LFC) is formed on the membrane of lysosomes, which inhibits the GTPase-activating activity of FLCN, inactivates mTORC1 and maximizes nuclear translocation of TFEB and TFE3 (PubMed:31672913). Upon amino acid restimulation, RRAGA/RagA (or RRAGB/RagB) nucleotide exchange promotes disassembly of the LFC complex and liberates the GTPase-activating activity of FLCN, leading to activation of mTORC1 and subsequent cytoplasmic retention of TFEB and TFE3 (PubMed:31672913). Indirectly acts as a positive regulator of Wnt signaling by promoting mTOR-dependent cytoplasmic retention of MiT/TFE factor TFE3 (PubMed:31272105). Required for the exit of hematopoietic stem cell from pluripotency by promoting mTOR-dependent cytoplasmic retention of TFE3, thereby increasing Wnt signaling (PubMed:30733432). Acts as an inhibitor of browning of adipose tissue by regulating mTOR-dependent cytoplasmic retention of TFE3 (By similarity). Involved in the control of embryonic stem cells differentiation; together with LAMTOR1 it is necessary to recruit and activate RRAGC/RagC and RRAGD/RagD at the lysosomes, and to induce exit of embryonic stem cells from pluripotency via non-canonical, mTOR-independent TFE3 inactivation (By similarity). In response to flow stress, regulates STK11/LKB1 accumulation and mTORC1 activation through primary cilia: may act by recruiting STK11/LKB1 to primary cilia for activation of AMPK resided at basal bodies, causing mTORC1 down-regulation (PubMed:27072130). Together with FNIP1 and/or FNIP2, regulates autophagy: following phosphorylation by ULK1, interacts with GABARAP and promotes autophagy (PubMed:25126726). Required for starvation-induced perinuclear clustering of lysosomes by promoting association of RILP with its effector RAB34 (PubMed:27113757). GTPase-activating activity is inhibited in the folliculin complex (LFC), which stabilizes the GDP-bound state of RRAGA/RagA (or RRAGB/RagB), because Arg-164 is located far from the RRAGC/RagC or RRAGD/RagD nucleotide pocket (PubMed:31672913). Disassembly of the LFC complex upon amino acid restimulation liberates the GTPase-activating activity (PubMed:31672913). Interacts (via C-terminus) with FNIP1 or FNIP2 (via C-terminus) (PubMed:17028174, PubMed:18403135, PubMed:18663353, PubMed:27353360). Component of the lysosomal folliculin complex (LFC), composed of FLCN, FNIP1 (or FNIP2), RRAGA/RagA or RRAGB/RagB GDP-bound, RRAGC/RagC or RRAGD/RagD GTP-bound, and Ragulator (PubMed:31704029, PubMed:31672913). Interaction with FNIP1 or FNIP2 mediates indirect interaction with the PRKAA1, PRKAB1 and PRKAG1 subunits of 5'-AMP-activated protein kinase (AMPK) (PubMed:17028174). Interacts with HSP90AA1 in the presence of FNIP1 (PubMed:27353360). Interacts with HSP70, STUB1, CDC37, AHSA1, CCT2, STIP1, PTGES3 and PPP5C (PubMed:27353360). Interacts with GABARAP; interaction takes place in the presence of FNIP1 and/or FNIP2 (PubMed:25126726). Interacts with RILP; the interaction is direct and promotes association between RILP and RAB34 (PubMed:27113757). Interacts with KIF3A and KIF3B (PubMed:27072130). Interacts with lactate dehydrogenase LDHA, but not LDHB; the interaction is direct, may preferentially bind LDHA dimers rather than tetramers, and regulates LDHA activity, acting as an uncompetitive inhibitor (PubMed:34381247). Localizes to lysosome membrane in amino acid-depleted conditions and relocalizes to the cytosol upon refeeding (PubMed:24095279, PubMed:29848618, PubMed:31672913). Colocalizes with FNIP1 and FNIP2 in the cytoplasm (PubMed:17028174, PubMed:18663353). Also localizes to motile and non-motile cilia, centrosomes and the mitotic spindle (PubMed:23784378). Expressed in most tissues tested, including skin, lung, kidney, heart, testis and stomach. Expressed in fetal lung, kidney, liver, and brain. Phosphorylation by ULK1 modulates the interaction with GABARAP and is required to regulate autophagy. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The gene represented in this entry may be involved in disease pathogenesis. Belongs to the folliculin family. Based on its structure and in vitro assays, was initially thought to have guanine nucleotide exchange factor (GEF) activity (PubMed:22977732). However, subsequent studies showed that it does not act as GEF in vivo (PubMed:24095279). Folliculin (FLCN)