title: SCFFBXL¹⁵ regulates BMP signalling by directing the degradation of HECT-type ubiquitin ligase Smurf1.
abstract: Smad ubiquitination regulatory factor 1 (Smurf1), an homologous to E6AP C-terminus (HECT)-type E3 ubiquitin ligase, performs a crucial role in the regulation of the bone morphogenetic protein (BMP) signalling pathway in both embryonic development and bone remodelling. How the stability and activity of Smurf1 are negatively regulated remains largely unclear. Here, we report that F-box and LRR domain-containing protein 15 (FBXL15), an F-box protein of the FBXL family, forms an Skp1-Cullin1-F-box protein-Roc1 (SCF)(FBXL15) ubiquitin ligase complex and targets Smurf1 for ubiquitination and proteasomal degradation. FBXL15, through its leucine-rich repeat domain, specifically recognizes the large subdomain within the N-lobe of the Smurf1 HECT domain and promotes the ubiquitination of Smurf1 on K355 and K357 within the WW-HECT linker region. In this way, FBXL15 positively regulates BMP signalling in mammalian cells. Knockdown of fbxl15 expression in zebrafish embryos by specific antisense morpholinos causes embryonic dorsalization phenocoping BMP-deficient mutants. Injection of FBXL15 siRNAs into rat bone tissues leads to a significant loss of bone mass and decrease in bone mineral density. Collectively, our results demonstrate that Smurf1 stability is suppressed by SCF(FBXL15)-mediated ubiquitination and that FBXL15 is a key regulator of BMP signalling during embryonic development and adult bone formation.
authors.affiliation: State Key Laboratory of Proteomics, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Cui
authors.forename: Shan
authors.initials: S
authors.lastname: He
authors.forename: Cencan
authors.initials: C
authors.lastname: Xing
authors.forename: Kefeng
authors.initials: K
authors.lastname: Lu
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Guichun
authors.initials: G
authors.lastname: Xing
authors.forename: Anming
authors.initials: A
authors.lastname: Meng
authors.forename: Shunji
authors.initials: S
authors.lastname: Jia
authors.forename: Fuchu
authors.initials: F
authors.lastname: He
authors.forename: Lingqiang
authors.initials: L
authors.lastname: Zhang
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001846:Bone Development / Q000235:genetics / Q000502:physiology; D019485:Bone Morphogenetic Proteins / Q000378:metabolism* / Q000502:physiology; D002478:Cells, Cultured; D003198:Computer Simulation; D004625:Embryo, Nonmammalian; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008954:Models, Biological; D011499:Protein Processing, Post-Translational / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary; D051381:Rats; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics
chemical_list: D019485:Bone Morphogenetic Proteins; D044783:F-Box Proteins; C561059:FBXL15 protein, rat; C561060:FBXL15 protein, zebrafish; C556581:Smurf1 protein, rat; D044843:SKP Cullin F-Box Protein Ligases; D044767:Ubiquitin-Protein Ligases