Astria D. Ferrão-Gonzales

Dissociation of amyloid fibrils of α-synuclein and transthyretin by pressure reveals their reversible nature and the formation of water-excluded cavities

Protein misfolding and aggregation have been linked to several human diseases, including Alzheimers disease, Parkinsons disease, and systemic amyloidosis, by mechanisms that are not yet completely understood. The hallmark of most of these diseases is the formation of highly ordered and β-sheet-rich aggregates referred to as amyloid fibrils. Fibril formation by WT transthyretin (TTR) or TTR variants has been linked to the etiology of systemic amyloidosis and familial amyloid polyneuropathy, respectively. Similarly, amyloid fibril formation by α-synuclein (α-syn) has been linked to neurodegeneration in Parkinsons disease, a movement disorder characterized by selective degeneration of dopaminergic neurons in the substantia nigra. Here we show that consecutive cycles of compression–decompression under aggregating conditions lead to reversible dissociation of TTR and α-syn fibrils. The high sensitivity of amyloid fibrils toward high hydrostatic pressure (HHP) indicates the existence of packing defects in the fibril core. In addition, through the use of HHP we are able to detect differences in stability between fibrils formed from WT TTR and the familial amyloidotic polyneuropathy-associated variant V30M. The fibrils formed by WT α-syn were less susceptible to pressure denaturation than the Parkinsons disease-linked variants, A30P and A53T. This finding implies that fibrils of α-syn formed from the variants would be more easily dissolved into small oligomers by the cellular machinery. This result has physiological importance in light of the current view that the pathogenic species are the small aggregates rather the mature fibrils. Finally, the HHP-induced formation of fibrils from TTR is relatively fast (≈60 min), a quality that allows screening of antiamyloidogenic drugs.

Hydration and packing are crucial to amyloidogenesis as revealed by pressure studies on transthyretin variants that either protect or worsen amyloid disease

The formation of amyloid aggregates is the hallmark of the amyloidogenic diseases. Transthyretin (TTR) is involved in senile systemic amyloidosis (wild-type protein) and familial amyloidotic polyneuropathy (point mutants). Through the use of high hydrostatic pressure (HHP), we compare the stability among wild-type (wt) TTR, two disease-associated mutations (V30M and L55P) and a trans-suppressor mutation (T119M). Our data show that the amyloidogenic conformation, easily populated in the disease-associated mutant L55P, can be induced by a cycle of compression-decompression with the wt protein rendering the latter highly amyloidogenic. After decompression, the recovered wt structure has weaker subunit interactions (loosened tetramer, T(4)(*)) and presents a stability similar to L55P, suggesting that HHP induces a defective fold in the wt protein, converting it to an altered conformation already present in the aggressive mutant, L55P. On the other hand, glucose, a chemical chaperone, can mimic the trans-suppression mutation by stabilizing the native state and by decreasing the amyloidogenic potential of the wt TTR at pH 5.0. The sequence of pressure stability observed was: L55P<V30M<wt<<T119M. The pressure dissociation of L55P at 1 degrees C exhibited dependence on protein concentration, allowing us to assess the volume change of association and the free-energy change. After a cycle of compression-decompression at 37 degrees C and pH 5.6 or lower, all amyloidogenic variants underwent aggregation. Binding of bis-(8-anilinonaphthalene-1-sulfonate) (bis-ANS) revealed that the species formed under pressure retained part of its tertiary contacts (except T119M). However, at neutral pH, where aggregation did not take place after decompression, bis-ANS binding was absent. Thus, TTR has to experience this partially folded conformation to undergo aggregation after decompression. Overall, our studies provide evidence that amyloidogenesis correlates with less packed structures (larger volume changes) and high susceptibility to water infiltration. The hydration effects can be counteracted by osmolytes or by a specific mutation.

One-step enzymatic production of fatty acid ethyl ester from high-acidity waste feedstocks in solvent-free media

This work aims to demonstrate the enzymatic production of fatty acid ethyl ester biodiesel from highly acidic feedstock in a single-step reaction, without co-solvents and avoiding the inhibition of the enzyme by ethanol and glycerol. Additionally, an empirical equation is proposed to predict the kinetics of the production reaction as a function of the used feedstock and catalyst concentration. Biodiesel production from highly acidic feedstock perform via simultaneous esterification of free fatty acids and transesterification of triacylglycerols. Enzymatic catalysis is one of the most promising alternative technologies for the biodiesel production. Increasing of the enzymatic bioactivity is crucial for the success of such process in industrial scale. Currently, stepwise addition of the alcohol or the use of co-solvents have been proposed to avoid enzyme inhibition, such strategies add downstream processes to the production. These results can be applied to the development economical-viable enzymatic production of biodiesel in industrial scale.