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Ramirez Reyes JMJ, Cuesta R, Pause A. Folliculin: A Regulator of Transcription Through AMPK and mTOR Signaling Pathways. Front Cell Dev Biol 2021; 9:667311. [PMID: 33981707 PMCID: PMC8107286 DOI: 10.3389/fcell.2021.667311] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 03/29/2021] [Indexed: 12/15/2022] Open
Abstract
Folliculin (FLCN) is a tumor suppressor gene responsible for the inherited Birt-Hogg-Dubé (BHD) syndrome, which affects kidneys, skin and lungs. FLCN is a highly conserved protein that forms a complex with folliculin interacting proteins 1 and 2 (FNIP1/2). Although its sequence does not show homology to known functional domains, structural studies have determined a role of FLCN as a GTPase activating protein (GAP) for small GTPases such as Rag GTPases. FLCN GAP activity on the Rags is required for the recruitment of mTORC1 and the transcriptional factors TFEB and TFE3 on the lysosome, where mTORC1 phosphorylates and inactivates these factors. TFEB/TFE3 are master regulators of lysosomal biogenesis and function, and autophagy. By this mechanism, FLCN/FNIP complex participates in the control of metabolic processes. AMPK, a key regulator of catabolism, interacts with FLCN/FNIP complex. FLCN loss results in constitutive activation of AMPK, which suggests an additional mechanism by which FLCN/FNIP may control metabolism. AMPK regulates the expression and activity of the transcriptional cofactors PGC1α/β, implicated in the control of mitochondrial biogenesis and oxidative metabolism. In this review, we summarize our current knowledge of the interplay between mTORC1, FLCN/FNIP, and AMPK and their implications in the control of cellular homeostasis through the transcriptional activity of TFEB/TFE3 and PGC1α/β. Other pathways and cellular processes regulated by FLCN will be briefly discussed.
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Affiliation(s)
- Josué M. J. Ramirez Reyes
- Goodman Cancer Research Center, McGill University, Montréal, QC, Canada
- Department of Biochemistry, McGill University, Montréal, QC, Canada
| | - Rafael Cuesta
- Goodman Cancer Research Center, McGill University, Montréal, QC, Canada
- Department of Biochemistry, McGill University, Montréal, QC, Canada
| | - Arnim Pause
- Goodman Cancer Research Center, McGill University, Montréal, QC, Canada
- Department of Biochemistry, McGill University, Montréal, QC, Canada
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Wang X, Wu H, Zhao L, Liu Z, Qi M, Jin Y, Liu W. FLCN regulates transferrin receptor 1 transport and iron homeostasis. J Biol Chem 2021; 296:100426. [PMID: 33609526 PMCID: PMC7995610 DOI: 10.1016/j.jbc.2021.100426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 01/19/2021] [Accepted: 02/12/2021] [Indexed: 11/30/2022] Open
Abstract
Birt–Hogg–Dubé (BHD) syndrome is a multiorgan disorder caused by inactivation of the folliculin (FLCN) protein. Previously, we identified FLCN as a binding protein of Rab11A, a key regulator of the endocytic recycling pathway. This finding implies that the abnormal localization of specific proteins whose transport requires the FLCN-Rab11A complex may contribute to BHD. Here, we used human kidney-derived HEK293 cells as a model, and we report that FLCN promotes the binding of Rab11A with transferrin receptor 1 (TfR1), which is required for iron uptake through continuous trafficking between the cell surface and the cytoplasm. Loss of FLCN attenuated the Rab11A–TfR1 interaction, resulting in delayed recycling transport of TfR1. This delay caused an iron deficiency condition that induced hypoxia-inducible factor (HIF) activity, which was reversed by iron supplementation. In a Drosophila model of BHD syndrome, we further demonstrated that the phenotype of BHD mutant larvae was substantially rescued by an iron-rich diet. These findings reveal a conserved function of FLCN in iron metabolism and may help to elucidate the mechanisms driving BHD syndrome.
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Affiliation(s)
- Xiaojuan Wang
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shanxi, China
| | - Hanjie Wu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shanxi, China
| | - Lingling Zhao
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shanxi, China
| | - Zeyao Liu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shanxi, China
| | - Maozhen Qi
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shanxi, China
| | - Yaping Jin
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shanxi, China.
| | - Wei Liu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shanxi, China.
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Ramírez JA, Iwata T, Park H, Tsang M, Kang J, Cui K, Kwong W, James RG, Baba M, Schmidt LS, Iritani BM. Folliculin Interacting Protein 1 Maintains Metabolic Homeostasis during B Cell Development by Modulating AMPK, mTORC1, and TFE3. J Immunol 2019; 203:2899-2908. [PMID: 31676673 DOI: 10.4049/jimmunol.1900395] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 09/30/2019] [Indexed: 12/11/2022]
Abstract
Folliculin interacting protein 1 (Fnip1) is a cytoplasmic protein originally discovered through its interaction with the master metabolic sensor 5' AMP-activated protein kinase (AMPK) and Folliculin, a protein mutated in individuals with Birt-Hogg-Dubé Syndrome. In response to low energy, AMPK stimulates catabolic pathways such as autophagy to enhance energy production while inhibiting anabolic pathways regulated by the mechanistic target of rapamycin complex 1 (mTORC1). We previously found that constitutive disruption of Fnip1 in mice resulted in a lack of peripheral B cells because of a block in B cell development at the pre-B cell stage. Both AMPK and mTORC1 were activated in Fnip1-deficient B cell progenitors. In this study, we found inappropriate mTOR localization at the lysosome under nutrient-depleted conditions. Ex vivo lysine or arginine depletion resulted in increased apoptosis. Genetic inhibition of AMPK, inhibition of mTORC1, or restoration of cell viability with a Bcl-xL transgene failed to rescue B cell development in Fnip1-deficient mice. Fnip1-deficient B cell progenitors exhibited increased nuclear localization of transcription factor binding to IgHM enhancer 3 (TFE3) in developing B cells, which correlated with an increased expression of TFE3-target genes, increased lysosome numbers and function, and increased autophagic flux. These results indicate that Fnip1 modulates autophagy and energy response pathways in part through the regulation of AMPK, mTORC1, and TFE3 in B cell progenitors.
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Affiliation(s)
- Julita A Ramírez
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195
| | - Terri Iwata
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195
| | - Heon Park
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195
| | - Mark Tsang
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195
| | - Janella Kang
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195
| | - Katy Cui
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195
| | - Winnie Kwong
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195
| | | | - Masaya Baba
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892; and
| | - Laura S Schmidt
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892; and.,Basic Sciences Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Brian M Iritani
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195;
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Zhao L, Ji X, Zhang X, Li L, Jin Y, Liu W. FLCN is a novel Rab11A-interacting protein that is involved in the Rab11A-mediated recycling transport. J Cell Sci 2018; 131:jcs.218792. [PMID: 30446510 DOI: 10.1242/jcs.218792] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 11/02/2018] [Indexed: 12/23/2022] Open
Abstract
The Birt-Hogg-Dubé (BHD) syndrome related protein FLCN has recently been implicated in the vesicular trafficking processes by interacting with several Rab family GTPases. In the previous studies, we have shown that FLCN could inhibit the binding of overexpressed PAT1, which is a membrane-bound amino acid transporter, to the lysosome in human embryonic kidney 293 cells. This tends to stabilize the lysosomal amino acid pool that is a critical signal to activate the mTORC1 signaling pathway. However, the mechanisms of FLCN during this process remain unexplored. Here we report that FLCN can bind through its C-terminal DENN-like domain to the recycling transport regulator, Rab11A. Suppression of either Rab11A or FLCN facilitated the localization of the overexpressed PAT1 to the lysosome and inhibited its targeting on the plasma membrane. As a consequence, the mTORC1 was down-regulated. The in vitro GEF activity assay does not support FLCN modifies the Rab11A activity directly. Instead, we found FLCN promoted the loading of PAT1 on Rab11A. Our data uncover a function of FLCN in the Rab11A-mediated recycling pathway and might provide new clues to understand BHD.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Lingling Zhao
- Key Laboratory of Animal Biotechnology, the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China 712100
| | - Xin Ji
- Key Laboratory of Animal Biotechnology, the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China 712100
| | - Xiangxiang Zhang
- Key Laboratory of Animal Biotechnology, the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China 712100
| | - Lin Li
- Key Laboratory of Animal Biotechnology, the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China 712100
| | - Yaping Jin
- Key Laboratory of Animal Biotechnology, the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China 712100
| | - Wei Liu
- Key Laboratory of Animal Biotechnology, the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China 712100
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Schmidt LS, Linehan WM. FLCN: The causative gene for Birt-Hogg-Dubé syndrome. Gene 2018; 640:28-42. [PMID: 28970150 DOI: 10.1016/j.gene.2017.09.044] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 09/11/2017] [Accepted: 09/21/2017] [Indexed: 01/30/2023]
Abstract
Germline mutations in the novel tumor suppressor gene FLCN are responsible for the autosomal dominant inherited disorder Birt-Hogg-Dubé (BHD) syndrome that predisposes to fibrofolliculomas, lung cysts and spontaneous pneumothorax, and an increased risk for developing kidney tumors. Although the encoded protein, folliculin (FLCN), has no sequence homology to known functional domains, x-ray crystallographic studies have shown that the C-terminus of FLCN has structural similarity to DENN (differentially expressed in normal cells and neoplasia) domain proteins that act as guanine nucleotide exchange factors (GEFs) for small Rab GTPases. FLCN forms a complex with folliculin interacting proteins 1 and 2 (FNIP1, FNIP2) and with 5' AMP-activated protein kinase (AMPK). This review summarizes FLCN functional studies which support a role for FLCN in diverse metabolic pathways and cellular processes that include modulation of the mTOR pathway, regulation of PGC1α and mitochondrial biogenesis, cell-cell adhesion and RhoA signaling, control of TFE3/TFEB transcriptional activity, amino acid-dependent activation of mTORC1 on lysosomes through Rag GTPases, and regulation of autophagy. Ongoing research efforts are focused on clarifying the primary FLCN-associated pathway(s) that drives the development of fibrofolliculomas, lung cysts and kidney tumors in BHD patients carrying germline FLCN mutations.
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Toledano A, Bourmech M, Lamallem H, Bollet M, Bauduceau O, Pujol P, Bloch P, Khayat D. [Prospective: How will renal, prostatic and urothelial tumours be treated in 10 years?]. Nephrol Ther 2017; 13 Suppl 1:S115-25. [PMID: 28577732 DOI: 10.1016/j.nephro.2017.01.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 01/19/2017] [Indexed: 12/13/2022]
Abstract
Forward thinking does not seek to predict the future, to unveil it as if it were already in existence, rather, its aim is to help us to construct it. Although today's epidemiological and therapeutic situations for urogenital tumours can evolve over the next 10 years, diagnostic and therapeutic methods, as well as the treatment and implementation of innovations, are already rapidly changing. Rather than reducing our prospective thinking to the therapeutic treatment of cancer only, we will aim at proposing a global sanitary vision that includes diagnosis, therapies, prevention, routine utilisation of technomedicine, genomics and even nanomedicine. This journey into the near future of tomorrow's cancerology holds the promise of being better adapted to the evolution of the medical thinking process. Imagining the way we will be treating renal, prostatic and urothelial tumours in 10 years' time is as much an introspection into our present day treatment system as a projection into its hoped for future evolution.
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Kenyon EJ, Luijten MNH, Gill H, Li N, Rawlings M, Bull JC, Hadzhiev Y, van Steensel MAM, Maher E, Mueller F. Expression and knockdown of zebrafish folliculin suggests requirement for embryonic brain morphogenesis. BMC Dev Biol 2016; 16:23. [PMID: 27391801 PMCID: PMC4939010 DOI: 10.1186/s12861-016-0119-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 05/15/2016] [Indexed: 12/27/2022]
Abstract
Background Birt-Hogg-Dubé syndrome (BHD) is a dominantly inherited familial cancer syndrome characterised by the development of benign skin fibrofolliculomas, multiple lung and kidney cysts, spontaneous pneumothorax and susceptibility to renal cell carcinoma. BHD is caused by mutations in the gene encoding Folliculin (FLCN). Little is known about what FLCN does in a healthy individual and how best to treat those with BHD. As a first approach to developing a vertebrate model for BHD we aimed to identify the temporal and spatial expression of flcn transcripts in the developing zebrafish embryo. To gain insights into the function of flcn in a whole organism system we generated a loss of function model of flcn by the use of morpholino knockdown in zebrafish. Results flcn is expressed broadly and upregulated in the fin bud, somites, eye and proliferative regions of the brain of the Long-pec stage zebrafish embryos. Together with knockdown phenotypes, expression analysis suggest involvement of flcn in zebrafish embryonic brain development. We have utilised the zFucci system, an in vivo, whole organism cell cycle assay to study the potential role of flcn in brain development. We found that at the 18 somite stage there was a significant drop in cells in the S-M phase of the cell cycle in flcn morpholino injected embryos with a corresponding increase of cells in the G1 phase. This was particularly evident in the brain, retina and somites of the embryo. Timelapse analysis of the head region of flcn morpholino injected and mismatch control embryos shows the temporal dynamics of cell cycle misregulation during development. Conclusions In conclusion we show that zebrafish flcn is expressed in a non-uniform manner and is likely required for the maintenance of correct cell cycle regulation during embryonic development. We demonstrate the utilisation of the zFucci system in testing the role of flcn in cell proliferation and suggest a function for flcn in regulating cell proliferation in vertebrate embryonic brain development. Electronic supplementary material The online version of this article (doi:10.1186/s12861-016-0119-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Emma J Kenyon
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. .,Sussex Neuroscience, School of Life Sciences, University of Sussex, Falmer, Brighton, UK.
| | - Monique N H Luijten
- Department of Dermatology and GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Harmeet Gill
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Nan Li
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Matthew Rawlings
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - James C Bull
- Department of Biosciences, College of Science, Swansea University, Swansea, SA2 8PP, Wales, UK
| | - Yavor Hadzhiev
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Maurice A M van Steensel
- School of Medicine and School of Life Sciences, University of Dundee, Dow Street, Dundee, UK.,Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore, Singapore
| | - Eamonn Maher
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Ferenc Mueller
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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Wu X, Zhao L, Chen Z, Ji X, Qiao X, Jin Y, Liu W. FLCN Maintains the Leucine Level in Lysosome to Stimulate mTORC1. PLoS One 2016; 11:e0157100. [PMID: 27280402 DOI: 10.1371/journal.pone.0157100] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 05/24/2016] [Indexed: 01/09/2023] Open
Abstract
The intracellular amino acid pool within lysosome is a signal that stimulates the nutrient-sensing mTORC1 signalling pathway. The signal transduction cascade has garnered much attention, but little is known about the sequestration of the signalling molecules within the lysosome. Using human HEK293 cells as a model, we found that suppression of the BHD syndrome gene FLCN reduced the leucine level in lysosome, which correlated with decreased mTORC1 activity. Both consequences could be reversed by supplementation with high levels of leucine, but not other tested amino acids. Conversely, overexpressed FLCN could sequester lysosomal leucine and stimulate mTORC1 in an amino acid limitation environment. These results identify a novel function of FLCN: it controls mTORC1 by modulating the leucine signal in lysosome. Furthermore, we provided evidence that FLCN exerted this role by inhibiting the accumulation of the amino acid transporter PAT1 on the lysosome surface, thereby maintaining the signal level within the organelle.
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Kennedy JC, Khabibullin D, Henske EP. Mechanisms of pulmonary cyst pathogenesis in Birt-Hogg-Dube syndrome: The stretch hypothesis. Semin Cell Dev Biol 2016; 52:47-52. [PMID: 26877139 DOI: 10.1016/j.semcdb.2016.02.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 02/04/2016] [Accepted: 02/08/2016] [Indexed: 12/11/2022]
Abstract
Loss-of-function mutations in the folliculin gene (FLCN) on chromosome 17p cause Birt-Hogg-Dube syndrome (BHD), which is associated with cystic lung disease. The risk of lung collapse (pneumothorax) in BHD patients is 50-fold higher than in the general population. The cystic lung disease in BHD is distinctive because the cysts tend to be basilar, subpleural and lentiform, differentiating BHD from most other cystic lung diseases. Recently, major advances in elucidating the primary functions of the folliculin protein have been made, including roles in mTOR and AMPK signaling via the interaction of FLCN with FNIP1/2, and cell-cell adhesion via the physical interaction of FLCN with plakophilin 4 (PKP4), an armadillo-repeat containing protein that interacts with E-cadherin and is a component of the adherens junctions. In addition, in just the last three years, the pulmonary impact of FLCN deficiency has been examined for the first time. In mouse models, evidence has emerged that AMPK signaling and cell-cell adhesion are involved in alveolar enlargement. In addition, the pathologic features of human BHD cysts have been recently comprehensively characterized. The "stretch hypothesis" proposes that cysts in BHD arise because of fundamental defects in cell-cell adhesion, leading to repeated respiration-induced physical stretch-induced stress and, over time, expansion of alveolar spaces particularly in regions of the lung with larger changes in alveolar volume and at weaker "anchor points" to the pleura. This hypothesis ties together many of the new data from cellular and mouse models of BHD and from the human pathologic studies. Critical questions remain. These include whether the consequences of stretch-induced cyst formation arise through a destructive/inflammatory program or a proliferative program (or both), whether cyst initiation involves a "second hit" genetic event inactivating the remaining wild-type copy of FLCN (as is known to occur in BHD-associated renal cell carcinomas), and whether cyst initiation involves exclusively the epithelial compartment versus an interaction between the epithelium and mesenchyme. Ultimately, understanding the mechanisms of cystic lung disease in BHD may help to elucidate the pathogenesis of primary spontaneous pneumothorax, with more than 20,000 cases reported annually in the United States alone.
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Abstract
The evolutionarily conserved target of rapamycin complex 1 (TORC1) is a master regulator of cell growth and metabolism. In mammals, growth factors and cellular energy stimulate mTORC1 activity through inhibition of the TSC complex (TSC1-TSC2-TBC1D7), a negative regulator of mTORC1. Amino acids signal to mTORC1 independently of the TSC complex. Here, we review recently identified regulators that link amino acid sufficiency to mTORC1 activity and how mutations affecting these regulators cause human disease.
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Gijezen LMC, Vernooij M, Martens H, Oduber CEU, Henquet CJM, Starink TM, Prins MH, Menko FH, Nelemans PJ, van Steensel MAM. Topical rapamycin as a treatment for fibrofolliculomas in Birt-Hogg-Dubé syndrome: a double-blind placebo-controlled randomized split-face trial. PLoS One 2014; 9:e99071. [PMID: 24910976 PMCID: PMC4049818 DOI: 10.1371/journal.pone.0099071] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 05/08/2014] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Birt-Hogg-Dubé syndrome (BHD) is a rare autosomal dominant disorder characterised by the occurrence of benign, mostly facial, skin tumours called fibrofolliculomas, multiple lung cysts, spontaneous pneumothorax and an increased renal cancer risk. Current treatments for fibrofolliculomas have high rates of recurrence and carry a risk of complications. It would be desirable to have a treatment that could prevent fibrofolliculomas from growing. Animal models of BHD have previously shown deregulation of mammalian target of rapamycin (mTOR). Topical use of the mTOR inhibitor rapamycin is an effective treatment for the skin tumours (angiofibromas) in tuberous sclerosis complex, which is also characterised by mTOR deregulation. In this study we aimed to determine if topical rapamycin is also an effective treatment for fibrofolliculomas in BHD. METHODS We performed a double blinded, randomised, facial left-right controlled trial of topical rapamycin 0.1% versus placebo in 19 BHD patients. Trial duration was 6 months. The primary outcome was cosmetic improvement as measured by doctors and patients. Changes in fibrofolliculoma number and size were also measured, as was occurrence of side effects. RESULTS No change in cosmetic status of fibrofolliculomas was reported in the majority of cases for the rapamycin treated (79% by doctors, 53% by patients) as well as the placebo treated facial sides (both 74%). No significant differences between rapamycin and placebo treated facial halves were observed (p = 1.000 for doctors opinion, p = 0.344 for patients opinion). No significant difference in fibrofolliculoma number or change in size of the fibrofolliculomas was seen after 6 months. Side effects occurred more often after rapamycin treatment (68% of patients) than after placebo (58% of patients; p = 0.625). A burning sensation, erythema, itching and dryness were most frequently reported. CONCLUSIONS This study provides no evidence that treatment of fibrofolliculomas with topical rapamycin in BHD results in cosmetic improvement. TRIAL REGISTRATION ClinicalTrials.gov NCT00928798.
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Affiliation(s)
- Lieke M. C. Gijezen
- Department of Dermatology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Marigje Vernooij
- Department of Dermatology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Herm Martens
- Department of Dermatology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Charlene E. U. Oduber
- Department of Dermatology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Charles J. M. Henquet
- Department of Dermatology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Theo M. Starink
- Department of Dermatology, VU University Medical Centre, Amsterdam, The Netherlands
| | - Martin H. Prins
- Department of Epidemiology, CAPHRI Research School for Public Health Primary Care, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Fred H. Menko
- Department of Clinical Genetics, VU University Medical Centre, Amsterdam, The Netherlands
| | - Patty J. Nelemans
- Department of Epidemiology, CAPHRI Research School for Public Health Primary Care, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Maurice A. M. van Steensel
- Department of Dermatology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
- Department of Clinical Genetics, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
- Institute of Medical Biology, Singapore, Singapore
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Goncharova EA, Goncharov DA, James ML, Atochina-Vasserman EN, Stepanova V, Hong SB, Li H, Gonzales L, Baba M, Linehan WM, Gow AJ, Margulies S, Guttentag S, Schmidt LS, Krymskaya VP. Folliculin controls lung alveolar enlargement and epithelial cell survival through E-cadherin, LKB1, and AMPK. Cell Rep 2014; 7:412-23. [PMID: 24726356 DOI: 10.1016/j.celrep.2014.03.025] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 01/30/2014] [Accepted: 03/10/2014] [Indexed: 12/21/2022] Open
Abstract
Spontaneous pneumothoraces due to lung cyst rupture afflict patients with the rare disease Birt-Hogg-Dubé (BHD) syndrome, which is caused by mutations of the tumor suppressor gene folliculin (FLCN). The underlying mechanism of the lung manifestations in BHD is unclear. We show that BHD lungs exhibit increased alveolar epithelial cell apoptosis and that Flcn deletion in mouse lung epithelium leads to cell apoptosis, alveolar enlargement, and an impairment of both epithelial barrier and overall lung function. We find that Flcn-null epithelial cell apoptosis is the result of impaired AMPK activation and increased cleaved caspase-3. AMPK activator LKB1 and E-cadherin are downregulated by Flcn loss and restored by its expression. Correspondingly, Flcn-null cell survival is rescued by the AMPK activator AICAR or constitutively active AMPK. AICAR also improves lung condition of Flcn(f/f):SP-C-Cre mice. Our data suggest that lung cysts in BHD may result from an underlying defect in alveolar epithelial cell survival, attributable to FLCN regulation of the E-cadherin-LKB1-AMPK axis.
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Petit CS, Roczniak-Ferguson A, Ferguson SM. Recruitment of folliculin to lysosomes supports the amino acid-dependent activation of Rag GTPases. ACTA ACUST UNITED AC 2013; 202:1107-22. [PMID: 24081491 PMCID: PMC3787382 DOI: 10.1083/jcb.201307084] [Citation(s) in RCA: 244] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Birt-Hogg-Dubé syndrome, a human disease characterized by fibrofolliculomas (hair follicle tumors) as well as a strong predisposition toward the development of pneumothorax, pulmonary cysts, and renal carcinoma, arises from loss-of-function mutations in the folliculin (FLCN) gene. In this study, we show that FLCN regulates lysosome function by promoting the mTORC1-dependent phosphorylation and cytoplasmic sequestration of transcription factor EB (TFEB). Our results indicate that FLCN is specifically required for the amino acid-stimulated recruitment of mTORC1 to lysosomes by Rag GTPases. We further demonstrated that FLCN itself was selectively recruited to the surface of lysosomes after amino acid depletion and directly bound to RagA via its GTPase domain. FLCN-interacting protein 1 (FNIP1) promotes both the lysosome recruitment and Rag interactions of FLCN. These new findings define the lysosome as a site of action for FLCN and indicate a critical role for FLCN in the amino acid-dependent activation of mTOR via its direct interaction with the RagA/B GTPases.
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Affiliation(s)
- Constance S Petit
- Department of Cell Biology and 2 Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT 06510
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Tsun ZY, Bar-Peled L, Chantranupong L, Zoncu R, Wang T, Kim C, Spooner E, Sabatini DM. The folliculin tumor suppressor is a GAP for the RagC/D GTPases that signal amino acid levels to mTORC1. Mol Cell 2013; 52:495-505. [PMID: 24095279 DOI: 10.1016/j.molcel.2013.09.016] [Citation(s) in RCA: 390] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 09/18/2013] [Accepted: 09/18/2013] [Indexed: 10/26/2022]
Abstract
The mTORC1 kinase is a master growth regulator that senses numerous environmental cues, including amino acids. The Rag GTPases interact with mTORC1 and signal amino acid sufficiency by promoting the translocation of mTORC1 to the lysosomal surface, its site of activation. The Rags are unusual GTPases in that they function as obligate heterodimers, which consist of RagA or B bound to RagC or D. While the loading of RagA/B with GTP initiates amino acid signaling to mTORC1, the role of RagC/D is unknown. Here, we show that RagC/D is a key regulator of the interaction of mTORC1 with the Rag heterodimer and that, unexpectedly, RagC/D must be GDP bound for the interaction to occur. We identify FLCN and its binding partners, FNIP1/2, as Rag-interacting proteins with GAP activity for RagC/D, but not RagA/B. Thus, we reveal a role for RagC/D in mTORC1 activation and a molecular function for the FLCN tumor suppressor.
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Affiliation(s)
- Zhi-Yang Tsun
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Liron Bar-Peled
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Lynne Chantranupong
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Roberto Zoncu
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Tim Wang
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Choah Kim
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Eric Spooner
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA
| | - David M Sabatini
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.,Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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