title: KBTBD13 interacts with Cullin 3 to form a functional ubiquitin ligase.
abstract: Autosomal dominant mutations in BTB and Kelch domain containing 13 protein (KBTBD13) are associated with a new type of Nemaline Myopathy (NEM). NEM is a genetically heterogeneous group of muscle disorders. Mutations causing phenotypically distinct NEM variants have previously been identified in components of muscle thin filament. KBTBD13 is a muscle specific protein composed of an N terminal BTB domain and a C terminal Kelch-repeat domain. The function of this newly identified protein in muscle remained unknown. In this study, we show that KBTBD13 interacts with Cullin 3 (Cul3) and the BTB domain mediates this interaction. Using ubiquitination assays, we determined that KBTBD13 participates in the formation of a Cul3 based RING ubiquitin ligase (Cul3-RL) capable of ubiquitin conjugation. Confocal microscopy of transiently expressed KBTBD13 revealed its co-localization with ubiquitin. Taken together, our results demonstrate that KBTBD13 is a putative substrate adaptor for Cul3-RL that functions as a muscle specific ubiquitin ligase, and thereby implicate the ubiquitin proteasome pathway in the pathogenesis of KBTBD13-associated NEM.
authors.affiliation: Department of Anesthesiology, Uniformed Services University, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA. nyamkhishig.sambuughin@usuhs.edu
authors.forename: Nyamkhishig
authors.initials: N
authors.lastname: Sambuughin
authors.forename: Wieslaw
authors.initials: W
authors.lastname: Swietnicki
authors.forename: Stephen
authors.initials: S
authors.lastname: Techtmann
authors.forename: Vera
authors.initials: V
authors.lastname: Matrosova
authors.forename: Tarina
authors.initials: T
authors.lastname: Wallace
authors.forename: Lev
authors.initials: L
authors.lastname: Goldfarb
authors.forename: Ernest
authors.initials: E
authors.lastname: Maynard
mesh_terms: D000818:Animals; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000201:enzymology; D006801:Humans; D051379:Mice; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D017696:Myopathies, Nemaline / Q000201:enzymology / Q000235:genetics; D041681:NIH 3T3 Cells; D017434:Protein Structure, Tertiary; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: C503645:CUL3 protein, human; D044842:Cullin Proteins; C555066:KBTBD13 protein, human; D009124:Muscle Proteins; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases