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Intrabodies Binding the Proline-Rich Domains of Mutant Huntingtin Increase Its Turnover and Reduce Neurotoxicity

Southwell, Amber L. and Khoshnan, Ali and Dunn, Denise E. and Bugg, Charles W. and Lo, Donald C. and Patterson, Paul H. (2008) Intrabodies Binding the Proline-Rich Domains of Mutant Huntingtin Increase Its Turnover and Reduce Neurotoxicity. Journal of Neuroscience, 28 (36). pp. 9013-9020. ISSN 0270-6474. PMCID PMC2633448. doi:10.1523/JNEUROSCI.2747-08.2008.

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Image (GIF) (Figure S1. MW7, Happ1 and Happ3 bind Htt in a PRR-dependent manner) - Supplemental Material
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Image (GIF) (Figure S2. VL12.3 increases the level of nuclear HDx-1) - Supplemental Material
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Although expanded polyglutamine (polyQ) repeats are inherently toxic, causing at least nine neurodegenerative diseases, the protein context determines which neurons are affected. The polyQ expansion that causes Huntington's disease (HD) is in the first exon (HDx-1) of huntingtin (Htt). However, other parts of the protein, including the 17 N-terminal amino acids and two proline (polyP) repeat domains, regulate the toxicity of mutant Htt. The role of the P-rich domain that is flanked by the polyP domains has not been explored. Using highly specific intracellular antibodies (intrabodies), we tested various epitopes for their roles in HDx-1 toxicity, aggregation, localization, and turnover. Three domains in the P-rich region (PRR) of HDx-1 are defined by intrabodies: MW7 binds the two polyP domains, and Happ1 and Happ3, two new intrabodies, bind the unique, P-rich epitope located between the two polyP epitopes. We find that the PRR-binding intrabodies, as well as VL12.3, which binds the N-terminal 17 aa, decrease the toxicity and aggregation of HDx-1, but they do so by different mechanisms. The PRR-binding intrabodies have no effect on Htt localization, but they cause a significant increase in the turnover rate of mutant Htt, which VL12.3 does not change. In contrast, expression of VL12.3 increases nuclear Htt. We propose that the PRR of mutant Htt regulates its stability, and that compromising this pathogenic epitope by intrabody binding represents a novel therapeutic strategy for treating HD. We also note that intrabody binding represents a powerful tool for determining the function of protein epitopes in living cells.

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Additional Information:Copyright © 2008 Society for Neuroscience. Received June 16, 2008; accepted July 24, 2008. This work was supported by grants from the High Q, Hereditary Disease, and McGrath Foundations. We thank David Colby and K. Dane Wittrup for providing us with VL12.3, the Medical Research Council Center for Protein Engineering for providing us with the Griffin.1 library, Elena Cattaneo for providing us with ST14A cells, Christian Essrich for the design and piloting of the brain slice experiments, and Jan Ko for experimental support. Featured in TWIJ: This Week in the Journal.
Funding AgencyGrant Number
High Q FoundationUNSPECIFIED
Hereditary Disease FoundationUNSPECIFIED
McGrath FoundationUNSPECIFIED
Subject Keywords:Huntington; neurodegeneration; gene therapy; immunotherapy; intrabody; polyproline
Issue or Number:36
PubMed Central ID:PMC2633448
Record Number:CaltechAUTHORS:SOUjns08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11591
Deposited By: Archive Administrator
Deposited On:09 Sep 2008 02:47
Last Modified:08 Nov 2021 22:00

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