Birt-Hogg-Dube' syndrome, a disorder characterised by benign tumours of the hair follicle, lung cysts and renal neoplasia, is caused by germline mutations in the BHD(FLCN) gene; this encodes a tumour suppressor protein, folliculin (FLCN), of unknown function []. The folliculin- interacting protein, FNIP1, has also been identified and shown to interact with 5' AMP-activated protein kinase (AMPK), which plays a vital role in energy sensing []. Together, then, it is thought that folliculin (mutated in Birt-Hogg-Dube' syndrome) and its interaction partner, FNIP1, may be involved in energy and/or nutrient sensing via the AMPK and mTOR signalling pathways.FNIP1 has a homologue, FNIP2, which also interacts with FLCN and AMPK. C-terminally-deleted FLCN mutants, like those produced by germline mutations in BHD patients, do not bind FNIP2, suggesting that FLCN tumour-suppressor function may be facilitated by interactions with both FNIP1 and FNIP2 via its C terminus []. FNIP1 and FNIP2 are able to form homo- or heteromeric multimers, and may hence function either independently or cooperatively with FLCN [].This entry represents the FNIP family, including FNIP1 and FNIP2.
Folliculin (FLCN) is a tumor suppressor that enables nutrient-dependent activation of the mechanistic target of rapamycin complex 1 (mTORC1) protein kinase via its guanosine triphosphatase (GTPase) Activating Protein (GAP) activity. It belong to the DENN module family of proteins and contains a divergent DENN module comprised of a N-terminal longin domain (also known as upstream DENN domain, u-DENN), followed by a DENN domain. It forms a complex with its partners, FNIP1 or FNIP2 (Folliculin interacting protein 1 or 2), which directly contacts the Rag GTPases RagC/D to stimulate GTP hydrolysis and thus promote the conversion to the GDP-bound state. FLCN-FNIP2 adopts an extended conformation with two pairs of heterodimerized domains. They contain longin domains that heterodimerize and contact both nucleotide binding domains of the Rag heterodimer, and C-terminal DENN domains which interact at the distal end of the structure [, , ].This is a subdomain found at the C terminus in the DENN domain of folliculin.
Folliculin (FLCN) is a tumor suppressor that enables nutrient-dependent activation of the mechanistic target of rapamycin complex 1 (mTORC1) protein kinase via its guanosine triphosphatase (GTPase) Activating Protein (GAP) activity. It belong to the DENN module family of proteins and contains a divergent DENN module comprised of a N-terminal longin domain (also known as upstream DENN domain, u-DENN), followed by a DENN domain. It forms a complex with its partners, FNIP1 or FNIP2 (Folliculin interacting protein 1 or 2), which directly contacts the Rag GTPases RagC/D to stimulate GTP hydrolysis and thus promote the conversion to the GDP-bound state. FLCN-FNIP2 adopts an extended conformation with two pairs of heterodimerized domains. They contain longin domains that heterodimerize and contact both nucleotide binding domains of the Rag heterodimer, and C-terminal DENN domains which interact at the distal end of the structure [, , ].This is the DENN domain found at the C-terminal of folliculin. This domain shares structural similarity with DENN domain of DENN1B (a Rab GEF). It mediates contact with the longin domain in the heterodimers to ensure a strong intersubunit interaction [, , ].
Folliculin (FLCN) is a tumor suppressor that enables nutrient-dependent activation of the mechanistic target of rapamycin complex 1 (mTORC1) protein kinase via its guanosine triphosphatase (GTPase) Activating Protein (GAP) activity. It belong to the DENN module family of proteins and contains a divergent DENN module comprised of a N-terminal longin domain (also known as upstream DENN domain, u-DENN), followed by a DENN domain. It forms a complex with its partners, FNIP1 or FNIP2 (Folliculin interacting protein 1 or 2), which directly contacts the Rag GTPases RagC/D to stimulate GTP hydrolysis and thus promote the conversion to the GDP-bound state. FLCN-FNIP2 adopts an extended conformation with two pairs of heterodimerized domains. They contain longin domains that heterodimerize and contact both nucleotide binding domains of the Rag heterodimer, and C-terminal DENN domains which interact at the distal end of the structure [, , ].This is the N-terminal domain of folliculin, the longin domain [, , ]. An arginine residue located in this domain (Arg164) is catalytic residue for GAP activity [, ]. This domain can also be found in SMCR8, a component of the C9orf72-SMCR8 complex, a complex that has guanine nucleotide exchange factor (GEF) activity and regulates autophagy [, , , , , ].
