title: Conserved acidic amino acid residues in a second RNA recognition motif regulate assembly and function of TDP-43.
abstract: Accumulating evidence suggests that pathogenic TAR DNA-binding protein (TDP)-43 fragments contain a partial RNA-recognition motif domain 2 (RRM2) in amyotrophic lateral sclerosis (ALS)/frontotemporal lobar degeneration. However, the molecular basis for how this domain links to the conformation and function of TDP-43 is unclear. Previous crystal analyses have documented that the RRM2-DNA complex dimerizes under acidic and high salt conditions, mediated by the intermolecular hydrogen bonds of Glu246-Ile249 and Asp247-Asp247. The aims of this study were to investigate the roles of Glu246 and Asp247 in the molecular assembly of RRM2 under physiological conditions, and to evaluate their potential use as markers for TDP-43 misfolding due to the aberrantly exposed dimer interface. Unexpectedly, gel filtration analyses showed that, regardless of DNA interaction, the RRM2 domain remained as a stable monomer in phosphate-buffered saline. Studies using substitution mutants revealed that Glu246 and, especially, Asp247 played a crucial role in preserving the functional RRM2 monomers. Substitution to glycine at Glu246 or Asp247 induced the formation of fibrillar oligomers of RRM2 accompanied by the loss of DNA-binding affinity, which also affected the conformation and the RNA splicing function of full-length TDP-43. A novel monoclonal antibody against peptides containing Asp247 was found to react with TDP-43 inclusions of ALS patients and mislocalized cytosolic TDP-43 in cultured cells, but not with nuclear wild-type TDP-43. Our findings indicate that Glu246 and Asp247 play pivotal roles in the proper conformation and function of TDP-43. In particular, Asp247 should be studied as a molecular target with an aberrant conformation related to TDP-43 proteinopathy.
authors.affiliation: Molecular Neuroscience Research Center, Shiga University of Medical Science, Shiga, Japan.
authors.forename: Akemi
authors.initials: A
authors.lastname: Shodai
authors.forename: Akemi
authors.initials: A
authors.lastname: Ido
authors.forename: Noriko
authors.initials: N
authors.lastname: Fujiwara
authors.forename: Takashi
authors.initials: T
authors.lastname: Ayaki
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Morimura
authors.forename: Miki
authors.initials: M
authors.lastname: Oono
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Uchida
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Takahashi
authors.forename: Hidefumi
authors.initials: H
authors.lastname: Ito
authors.forename: Makoto
authors.initials: M
authors.lastname: Urushitani
mesh_terms: D000368:Aged; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D058846:Antibodies, Monoclonal, Murine-Derived / Q000737:chemistry; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D006860:Hydrogen Bonding; D002479:Inclusion Bodies / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019913:Nuclear Localization Signals; D011485:Protein Binding; D017510:Protein Folding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012326:RNA Splicing; D012995:Solubility; D013116:Spinal Cord / Q000378:metabolism
chemical_list: D058846:Antibodies, Monoclonal, Murine-Derived; D004268:DNA-Binding Proteins; D019913:Nuclear Localization Signals