Serine Phosphorylation Suppresses Huntingtin Amyloid Accumulation by Altering Protein Aggregation Properties

JOURNAL OF MOLECULAR BIOLOGY

卷:424

Article

Mishra, Rakesh^1,2  Hoop, Cody L.¹  Kodali, Ravindra^1,2  Sahoo, Bankanidhi^1,2  van der Wel, Patrick C. A.¹  Wetzel, Ronald^1,2 

[1] Univ Pittsburgh, Sch Med, Dept Biol Struct, Pittsburgh, PA 15260 USA

[2] Univ Pittsburgh, Sch Med, Pittsburgh Inst Neurodegenerat Dis, Pittsburgh, PA 15260 USA

关键词: alpha-helical oligomers;    nucleation;    critical concentration;    posttranslational modification;    phosphomimetic;   

DOI  :  10.1016/j.jmb.2012.09.011

来源: Elsevier

【 摘 要 】

Aggregation of expanded polyglutamine repeat-containing fragments of the huntingtin (htt) protein may play a key role in Huntington's disease. Consistent with this hypothesis, two Ser-to-Asp mutations in the 17-aminoacid N-terminal htt(NT) segment abrogate both visible brain aggregates and disease symptoms in a full-length Q(97) htt mouse model while compromising aggregation kinetics and aggregate morphology in an htt fragment in vitro [Gu et al. (2009). Serines 13 and 16 are critical determinants of full-length human mutant huntingtin induced disease pathogenesis in HD mice. Neuron 64,828-840]. The htt(NT) segment has been shown to play a critical role in facilitating nucleation of amyloid formation in htt N-terminal exon1 fragments. We show here how these Ser-to-Asp mutations dramatically affect aggregation kinetics and aggregate structural integrity. First, these negatively charged Ser replacements impair the assembly of the a-helical oligomers that play a critical role in htt amyloid nucleation, thus providing an explanation for reduced amyloid formation rates. Second, these sequence modifications alter aggregate morphology, decrease aggregate stability, and enhance the steric accessibility of the htt(NT) segment within the aggregates. Together, these changes make the sequence-modified peptides kinetically and thermodynamically less likely to aggregate and more susceptible, if they do, to posttranslational modifications and degradation. These effects also show how phosphorylation of a protein might achieve cellular effects via direct impacts on the protein's aggregation properties. In fact, preliminary studies on exon1-like molecules containing phosphoryl-Ser residues at positions 13 and 16 show that they reduce aggregation rates and generate atypical aggregate morphologies similar to the effects of the Ser-to-Asp mutants. (C) 2012 Elsevier Ltd. All rights reserved.

【 授权许可】

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