Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published July 31, 2015 | public
Journal Article Open

Anti-polyQ antibodies recognize a short polyQ stretch in both normal and mutant huntingtin exon 1


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.

Additional Information

© 2015 Elsevier B.V. Received date: 25 March 2015; Revised date: 19 May 2015; Accepted date: 20 May 2015; Available online 3 June 2015. We thank Beth Huey-Tubman and Alejandra Olvera for technical support; Thomas Weiss, Lester Carter, and the scientific staff of SSRL beamline 4-2 for help with SAXS experiments; Tobias Stuwe for assistance with SEC-MALS experiments; and Beth Stadtmueller and Melanie Brewer for critical reading of the manuscript. We thank R. S. Atwal at the Massachusetts General Hospital for providing the N17 antibody. We acknowledge the Gordon and Betty Moore Foundation for support of the Molecular Observatory at Caltech. The operations at SSRL are supported by the Department of Energy and by the National Institutes of Health. G.E.O. was supported by National Research Service Awards (T32GM7616, 5T32GM008042) from the National Institute of General Medical Sciences and by the Center for Advancement of Science in Space. Author Contributions: G.E.O. and P.J.B. conceived the study; G.E.O. and D.M.N. performed protein expression, purification, Western and dot blots, and SEC-MALS; G.E.O. performed equilibrium gel-filtration assays; G.E.O., A.P.W., and P.J.B. analyzed the data; and G.E.O. and P.J.B. wrote the paper with all co-authors contributing to scientific planning and discussions.

Attached Files

Accepted Version - nihms700085.pdf


Files (1.1 MB)
Name Size Download all
1.1 MB Preview Download

Additional details

August 22, 2023
August 22, 2023