| Autor: |
Kandola T; Stowers Institute for Medical Research, Kansas City, MO 64110, USA.; The Open University, Milton Keyes, MK7 6AA, UK., Venkatesan S; Stowers Institute for Medical Research, Kansas City, MO 64110, USA., Zhang J; Department of Physics, North Carolina State University, Raleigh, NC 27695, USA., Lerbakken B; Stowers Institute for Medical Research, Kansas City, MO 64110, USA., Schulze AV; Stowers Institute for Medical Research, Kansas City, MO 64110, USA., Blanck JF; Stowers Institute for Medical Research, Kansas City, MO 64110, USA., Wu J; Stowers Institute for Medical Research, Kansas City, MO 64110, USA.; Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA., Unruh J; Stowers Institute for Medical Research, Kansas City, MO 64110, USA., Berry P; Stowers Institute for Medical Research, Kansas City, MO 64110, USA., Lange JJ; Stowers Institute for Medical Research, Kansas City, MO 64110, USA., Box A; Stowers Institute for Medical Research, Kansas City, MO 64110, USA., Cook M; Stowers Institute for Medical Research, Kansas City, MO 64110, USA., Sagui C; Department of Physics, North Carolina State University, Raleigh, NC 27695, USA., Halfmann R; Stowers Institute for Medical Research, Kansas City, MO 64110, USA.; Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA. |
| Abstrakt: |
A long-standing goal of amyloid research has been to characterize the structural basis of the rate-determining nucleating event. However, the ephemeral nature of nucleation has made this goal unachievable with existing biochemistry, structural biology, and computational approaches. Here, we addressed that limitation for polyglutamine (polyQ), a polypeptide sequence that causes Huntington's and other amyloid-associated neurodegenerative diseases when its length exceeds a characteristic threshold. To identify essential features of the polyQ amyloid nucleus, we used a direct intracellular reporter of self-association to quantify frequencies of amyloid appearance as a function of concentration, conformational templates, and rational polyQ sequence permutations. We found that nucleation of pathologically expanded polyQ involves segments of three glutamine (Q) residues at every other position. We demonstrate using molecular simulations that this pattern encodes a four-stranded steric zipper with interdigitated Q side chains. Once formed, the zipper poisoned its own growth by engaging naive polypeptides on orthogonal faces, in a fashion characteristic of polymer crystals with intramolecular nuclei. We further show that self-poisoning can be exploited to block amyloid formation, by genetically oligomerizing polyQ prior to nucleation. By uncovering the physical nature of the rate-limiting event for polyQ aggregation in cells, our findings elucidate the molecular etiology of polyQ diseases. |
