title: FLCN, a novel autophagy component, interacts with GABARAP and is regulated by ULK1 phosphorylation.
abstract: Birt-Hogg-Dubé (BHD) syndrome is a rare autosomal dominant condition caused by mutations in the FLCN gene and characterized by benign hair follicle tumors, pneumothorax, and renal cancer. Folliculin (FLCN), the protein product of the FLCN gene, is a poorly characterized tumor suppressor protein, currently linked to multiple cellular pathways. Autophagy maintains cellular homeostasis by removing damaged organelles and macromolecules. Although the autophagy kinase ULK1 drives autophagy, the underlying mechanisms are still being unraveled and few ULK1 substrates have been identified to date. Here, we identify that loss of FLCN moderately impairs basal autophagic flux, while re-expression of FLCN rescues autophagy. We reveal that the FLCN complex is regulated by ULK1 and elucidate 3 novel phosphorylation sites (Ser406, Ser537, and Ser542) within FLCN, which are induced by ULK1 overexpression. In addition, our findings demonstrate that FLCN interacts with a second integral component of the autophagy machinery, GABA(A) receptor-associated protein (GABARAP). The FLCN-GABARAP association is modulated by the presence of either folliculin-interacting protein (FNIP)-1 or FNIP2 and further regulated by ULK1. As observed by elevation of GABARAP, sequestome 1 (SQSTM1) and microtubule-associated protein 1 light chain 3 (MAP1LC3B) in chromophobe and clear cell tumors from a BHD patient, we found that autophagy is impaired in BHD-associated renal tumors. Consequently, this work reveals a novel facet of autophagy regulation by ULK1 and substantially contributes to our understanding of FLCN function by linking it directly to autophagy through GABARAP and ULK1.
authors.affiliation: Institute of Cancer and Genetics, Cardiff University; Heath Park, Cardiff, Wales UK.
authors.forename: Elaine A
authors.initials: EA
authors.lastname: Dunlop
authors.affiliation: Institute of Cancer and Genetics, Cardiff University; Heath Park, Cardiff, Wales UK.
authors.forename: Sara
authors.initials: S
authors.lastname: Seifan
authors.affiliation: Institute of Cancer and Genetics, Cardiff University; Heath Park, Cardiff, Wales UK; Department of Dermatology; GROW School for Oncology and Developmental Biology; Maastricht University Medical Center; Maastricht, Netherlands.
authors.forename: Tijs
authors.initials: T
authors.lastname: Claessens
authors.affiliation: Frankfurt Institute for Molecular Life Sciences (FMLS) and Institute of Biochemistry II; Goethe University School of Medicine; Frankfurt, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Behrends
authors.affiliation: Department of Dermatology; GROW School for Oncology and Developmental Biology; Maastricht University Medical Center; Maastricht, Netherlands.
authors.forename: Miriam Af
authors.initials: MA
authors.lastname: Kamps
authors.affiliation: Centre for Cancer Research and Cell Biology; School of Medicine, Dentistry and Biomedical Science; Queen's University Belfast; Belfast, UK.
authors.forename: Ewelina
authors.initials: E
authors.lastname: Rozycka
authors.affiliation: Institute of Genetics and Molecular Medicine; Edinburgh Cancer Research UK Centre; University of Edinburgh; Edinburgh, UK.
authors.forename: Alain J
authors.initials: AJ
authors.lastname: Kemp
authors.affiliation: Department of Biochemistry; University of Cambridge; Cambridge, UK.
authors.forename: Ravi K
authors.initials: RK
authors.lastname: Nookala
authors.affiliation: Department of Cell Biology; Harvard Medical School; Boston, MA USA.
authors.forename: John
authors.initials: J
authors.lastname: Blenis
authors.affiliation: Department of Dermatology; GROW School for Oncology and Developmental Biology; Maastricht University Medical Center; Maastricht, Netherlands.
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Coull
authors.affiliation: Centre for Cancer Research and Cell Biology; School of Medicine, Dentistry and Biomedical Science; Queen's University Belfast; Belfast, UK; Trinity Biomedical Sciences Institute; School of Biochemistry and Immunology; Trinity College; Dublin, Ireland.
authors.forename: James T
authors.initials: JT
authors.lastname: Murray
authors.affiliation: Department of Dermatology; GROW School for Oncology and Developmental Biology; Maastricht University Medical Center; Maastricht, Netherlands; Immunos; Institute of Medical Biology; Singapore.
authors.forename: Maurice Am
authors.initials: MA
authors.lastname: van Steensel
authors.affiliation: Institute of Genetics and Molecular Medicine; Edinburgh Cancer Research UK Centre; University of Edinburgh; Edinburgh, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Wilkinson
authors.affiliation: Institute of Cancer and Genetics, Cardiff University; Heath Park, Cardiff, Wales UK.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Tee
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D001343:Autophagy; D000071189:Autophagy-Related Protein-1 Homolog; D058249:Birt-Hogg-Dube Syndrome / Q000378:metabolism / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*; D000071456:Sequestosome-1 Protein; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; C476078:FLCN protein, human; C516440:FNIP1 protein, human; C529782:FNIP2 protein, human; C116741:GABARAP protein, human; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D011518:Proto-Oncogene Proteins; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D025521:Tumor Suppressor Proteins; D000071189:Autophagy-Related Protein-1 Homolog; D017346:Protein Serine-Threonine Kinases; C484754:ULK1 protein, human
keywords: BHD; FLCN; GABARAP; MAP1LC3B; SQSTM1; ULK1; autophagy