title: Huntingtin-associated protein 1 (HAP1) binds to a Trio-like polypeptide, with a rac1 guanine nucleotide exchange factor domain.
abstract: Huntington's disease (HD) occurs when the widely expressed protein huntingtin contains an expanded glutamine repeat. The selective degeneration and neuronal morphologic abnormalities of HD may involve interactions with proteins that bind to huntingtin, such as HAP1. The biological significance of this interaction is unclear because neither HAP1 nor huntingtin have significant homology to known proteins. Therefore, we sought to identify HAP1-binding proteins. Using the yeast two-hybrid system, we isolated a rat cDNA encoding part of a protein that interacts with HAP1, and we confirmed the specificity of this interaction using an in vitro protein-binding assay. We called the protein Duo because it is closely related to the human protein Trio but is shorter. Northern blot analysis indicates brain-specific expression of Duo. Human Duo contains a guanine nucleotide exchange factor (GEF) domain that is likely to be rac1-specific, a pleckstrin homology (PH) domain and spectrin-like repeat units. These data support the hypothesis that huntingtin is involved in vesicle trafficking and cytoskeletal functions, and raise the possibility of a role for huntingtin in the regulation of a ras-related signaling pathway.
authors.affiliation: The Department of Psychiatry, The Johns Hopkins School of Medicine, Baltimore, MD 21205-2196, USA.
authors.forename: V
authors.initials: V
authors.lastname: Colomer
authors.forename: S
authors.initials: S
authors.lastname: Engelender
authors.forename: A H
authors.initials: AH
authors.lastname: Sharp
authors.forename: K
authors.initials: K
authors.lastname: Duan
authors.forename: J K
authors.initials: JK
authors.lastname: Cooper
authors.forename: A
authors.initials: A
authors.lastname: Lanahan
authors.forename: G
authors.initials: G
authors.lastname: Lyford
authors.forename: P
authors.initials: P
authors.lastname: Worley
authors.forename: C A
authors.initials: CA
authors.lastname: Ross
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D006816:Huntington Disease / Q000235:genetics*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D020663:ras Guanine Nucleotide Exchange Factors
chemical_list: D002352:Carrier Proteins; D020662:Guanine Nucleotide Exchange Factors; C096896:HAP1 protein, human; C490757:Hap1 protein, rat; C102365:Kalrn protein, rat; D009419:Nerve Tissue Proteins; D011506:Proteins; D012333:RNA, Messenger; D020663:ras Guanine Nucleotide Exchange Factors