Structure of Monomeric Transthyretin Carrying the Clinically Important T119M Mutation

Abstract

Mutations in the protein transthyretin can cause as well as protect individuals from transthyretin amyloidosis, an incurable fatal inherited disease. Little is known, however, about the structural basis of pathogenic and clinically protective transthyretin mutants. Here we determined the solution structure of a transthyretin monomer that carries the clinically important T119M mutation. The structure displays a non-native arrangement that is distinct from all known structures of transthyretin and highlights the importance of high-resolution studies in solution for understanding molecular processes that lead to amyloid diseases.

Oligomerization Profile of Human Transthyretin Variants with Distinct Amyloidogenicity

“…Moreover, in the case of the more amyloidogenic variants TTRV30M and TTRL55P, significant amounts of high-molecular-weight (HMW) aggregates were also observed at the top of the gels, in agreement with the well-known amyloidogenic behavior of these proteins [14][15][16]. Conversely, TTRT119M exhibited the presence of neither HMW nor LMW species other than 1-mers and 2-mers, even when incubated at low pH for several days, which is also in agreement with its nonamyloidogenic behavior [25,28,[48][49][50].…”

“…The gel pattern shows that the reaction mixture contains mainly unreacted TTRT119M monomer. This further validates the applicability of the PICUP method and demonstrates the low tendency for aggregation of the TTRT119M variant, which is also correlated with its nonamyloidogenic potential [25,[48][49][50]. Additionally, the ThT fluorescence assay (Figure 3) also corroborates these findings since it shows no fluorescence intensity increase or shift of the emission maximum in the presence of the dye, indicating that no amyloid fibril formation occurred.…”

“…The naturally occurring TTRT119M variant is often referred to as a stable and nonamyloidogenic TTR variant that protects TTRV30M carriers from disease [25,[48][49][50]. Thus, in order to obtain a PICUP pattern for TTRT119M and compare it with those of TTRwt, TTRV30M, and TTRL55P, we also subjected this nonamyloidogenic variant to acidification at pH 3.6, followed by cross-linking and SDS-PAGE analysis.…”

“…Thus, PICUP has been used as a method to study oligomerization processes and to evaluate the nature of transient oligomers formed by amyloidogenic proteins, such as amyloid-β peptide [33][34][35][36][37][38][39][40][41][42], α-synuclein [43][44][45][46], or prion protein [47], as well as a way to identify relevant targets in the amyloidosis cascade and new therapeutics [37,45]. Here, we compare the oligomerization process of (1) TTRwt; (2) the amyloidogenic variants TTRV30M and TTRL55P; and (3) the nonamyloidogenic variant TTRT119M [25,[48][49][50]. Thioflavin-T (ThT) fluorescence assays were also carried out in order to assess the presence of amyloid oligomers/aggregates.…”

Enthalpy-Driven Stabilization of Transthyretin by AG10 Mimics a Naturally Occurring Genetic Variant That Protects from Transthyretin Amyloidosis

“…Remarkably, similar hydrogen bonds have been reported within the inner cavity of the kinetically stabilizing trans-suppressor T119M-TTR variant (Figure 3b). 22, 23…”