Anti-PolyQ Antibodies Recognize a Short PolyQ Stretch in Both Normal and Mutant Huntingtin Exon 1

JOURNAL OF MOLECULAR BIOLOGY

卷:427

Article

Owens, Gwen E.^1,2  New, Danielle M.¹  West, Anthony P., Jr.¹  Bjorkman, Pamela J.^1,3 

[1] CALTECH, Div Biol & Biol Engn, Pasadena, CA 91125 USA

[2] CALTECH, Grad Opt Biochem & Mol Biophys, Pasadena, CA 91125 USA

[3] Howard Hughes Med Inst, Chevy Chase, MD 20815 USA

关键词: equilibrium gel-filtration;    Huntington's disease;    linear lattice;    polyglutamine;    small-angle X-ray scattering;   

DOI  :  10.1016/j.jmb.2015.05.023

来源: Elsevier

【 摘 要 】

Huntington's disease is caused by expansion of a polyglutamine (polyQ) repeat in the huntingtin protein. A structural basis for the apparent transition between normal and disease-causing expanded polyQ repeats of huntingtin is unknown. The linear lattice model proposed random-coil structures for both normal and expanded polyQ in the preaggregation state. Consistent with this model, the affinity and stoichiometry of the anti-polyQ antibody MW1 increased with the number of glutamines. An opposing structural toxic threshold model proposed a conformational change above the pathogenic polyQ threshold resulting in a specific toxic conformation for expanded polyQ. Support for this model was provided by the anti-polyQ antibody 3B5H10, which was reported to specifically recognize a distinct pathologic conformation of soluble expanded polyQ. To distinguish between these models, we directly compared binding of MW1 and 3B5H10 to normal and expanded polyQ repeats within huntingtin exon 1 fusion proteins. We found similar binding characteristics for both antibodies. First, both antibodies bound to normal, as well as expanded, polyQ in huntingtin exon 1 fusion proteins. Second, an expanded polyQ tract contained multiple epitopes for fragments antigen-binding (Fabs) of both antibodies, demonstrating that 3B5H10 does not recognize a single epitope specific to expanded polyQ. Finally, small-angle X-ray scattering and dynamic light scattering revealed similar binding modes for MW1 and 3B5H10 Fab huntingtin exon 1 complexes. Together, these results support the linear lattice model for polyQ binding proteins, suggesting that the hypothesized pathologic conformation of soluble expanded polyQ is not a valid target for drug design. (C) 2015 Elsevier Ltd. All rights reserved.

【 授权许可】

Free