Self-assembly of human latexin into amyloid-like oligomers

In conformational disorders, it is not evident which amyloid aggregates affect specific molecular mechanisms or cellular pathways, which cause disease because of their quantity and mechanical features and which states in aggregate formation are pathogenic. Due to the increasing consensus that prefibrillar oligomers play a major role in conformational diseases, there is a growing interest in understanding the characteristics of metastable polypeptide associations.

Here, we show that human latexin, a protein that shares the same fold with cystatin C, assembles into stable spherical amyloid-like oligomers that bind thioflavin-T and congo red similarly to common amyloid structures but do not evolve into fibrils. Latexin self-assembly correlates with the formation of a mostly denaturated state rather than with the population of partially structured intermediates during the unfolding process. The results suggest that unfolding of alpha-helix 3 might be involved in the transition of latexin toward amyloidotic species, supporting the notion of the protective role of the native protein structure against polymerization.

Overall the data herein indicate that latexin could be a good model for the study of the structural and sequential determinants of oligomeric assemblies in protein aggregation processes.