TY  - JOUR
A1  - Roethlein, Christoph
A1  - Miettinen, Markus S.
A1  - Borwankar, Tejas
A1  - Buerger, Joerg
A1  - Mielke, Thorsten
A1  - Kumke, Michael Uwe
A1  - Ignatova, Zoya
T1  - Architecture of polyglutamine-containing fibrils from time-resolved fluorescence decay
JF  - The journal of biological chemistry
N2  - The disease risk and age of onset of Huntington disease (HD) and nine other repeat disorders strongly depend on the expansion of CAG repeats encoding consecutive polyglutamines (polyQ) in the corresponding disease protein. PolyQ length-dependent misfolding and aggregation are the hallmarks of CAG pathologies. Despite intense effort, the overall structure of these aggregates remains poorly understood. Here, we used sensitive time-dependent fluorescent decay measurements to assess the architecture of mature fibrils of huntingtin (Htt) exon 1 implicated in HD pathology. Varying the position of the fluorescent labels in the Htt monomer with expanded 51Q (Htt51Q) and using structural models of putative fibril structures, we generated distance distributions between donors and acceptors covering all possible distances between the monomers or monomer dimensions within the polyQ amyloid fibril. Using Monte Carlo simulations, we systematically scanned all possible monomer conformations that fit the experimentally measured decay times. Monomers with four-stranded 51Q stretches organized into five-layered beta-sheets with alternating N termini of the monomers perpendicular to the fibril axis gave the best fit to our data. Alternatively, the core structure of the polyQ fibrils might also be a zipper layer with antiparallel four-stranded stretches as this structure showed the next best fit. All other remaining arrangements are clearly excluded by the data. Furthermore, the assessed dimensions of the polyQ stretch of each monomer provide structural evidence for the observed polyQ length threshold in HD pathology. Our approach can be used to validate the effect of pharmacological substances that inhibit or alter amyloid growth and structure.
Y1  - 2014
U6  - https://doi.org/10.1074/jbc.M114.581991
SN  - 0021-9258
SN  - 1083-351X
VL  - 289
IS  - 39
SP  - 26817
EP  - 26828
PB  - American Society for Biochemistry and Molecular Biology
CY  - Bethesda
ER  - 
TY  - JOUR
A1  - Borwankar, Tejas
A1  - Roethlein, Christoph
A1  - Zhang, Gong
A1  - Techen, Anne
A1  - Dosche, Carsten
A1  - Ignatova, Zoya
T1  - Natural osmolytes remodel the aggregation pathway of mutant huntingtin exon 1
JF  - Biochemistry
N2  - In response to stress small organic compounds termed osmolytes are ubiquitously accumulated in all cell types to regulate the intracellular solvent quality and to counteract the deleterious effect on the stability and function of cellular proteins. Given the evidence that destabilization of the native state of a protein either by mutation or by environmental changes triggers the aggregation in the neurodegenerative pathologies, the modulation of the intracellular solute composition with osmolytes is an attractive strategy to stabilize an aggregating protein. Here we report the effect of three natural osmolytes on the in vivo and in vitro aggregation landscape of huntingtin exon 1 implicated in the Huntington's disease. Trimethylamine N-oxide (TMAO) and proline redirect amyloid fibrillogenesis of the pathological huntingtin exon 1 to nonamyloidogenic amorphous assemblies via two dissimilar molecular mechanisms. TMAO causes a rapid formation of bulky amorphous aggregates with minimally exposed surface area, whereas proline solubilizes the monomer and suppresses the accumulation of early transient aggregates. Conversely, glycine betaine enhances fibrillization in a fashion reminiscent of the genesis of functional amyloids. Strikingly, none of the natural osmolytes can completely abrogate the aggregate formation; however, they redirect the amyloidogenesis into alternative, nontoxic aggregate species. Our study reveals new insights into the complex interactions of osmoprotectants with polyQaggregates.
Y1  - 2011
U6  - https://doi.org/10.1021/bi1018368
SN  - 0006-2960
VL  - 50
IS  - 12
SP  - 2048
EP  - 2060
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - THES
A1  - Borwankar, Tejas
T1  - Natural osmolytes remodel the aggregation pathway of mutant huntingtin exon 1
Y1  - 2011
CY  - Potsdam
ER  -