Loading...
2 results
Search Results
Now showing 1 - 2 of 2
- Testing the therapeutic potential of doxycycline in a drosophila melanogaster model of Alzheimer diseasePublication . Costa, Rita; Speretta, Elena; Crowther, Damian C.; Cardoso, IsabelTherapies for Alzheimer disease that reduce the production of pathogenic amyloid beta (A beta) peptides have been associated with a range of unwanted effects. For this reason, alternative strategies that promote the clearance of the peptide by preventing its aggregation and deposition in the brain have been favored. In this context we have studied doxycycline, a member of the tetracycline family of antibiotics that has shown neuroprotective effects in a number of models of neurodegenerative disease. We investigated the neuroprotective potential of doxycycline in a Drosophila model of A beta toxicity and sought to correlate any effects with the aggregation state of the peptide. We found that administration of doxycycline to A beta 42-expressing flies did not improve their lifespan but was able to slow the progression of their locomotor deficits. We also measured the rough eye phenotype of transgenic flies expressing the E22G variant of A beta 42 and showed that doxycycline administration partially rescued the toxicity of A beta in the developing eye. We correlated these in vivo effects with in vitro observations using transmission electron microscopy, dynamic light scattering, and thioflavin T binding. We found that doxycycline prevents A beta fibrillization and favors the generation of smaller, non-amyloid structures that were nontoxic as determined by the lack of caspase 3 activation in a neuroblastoma cell line. Our confirmation that doxycycline can prevent amyloid beta toxicity both in vitro and in vivo supports its therapeutic potential in AD.
- S100A6 Amyloid Fibril Formation Is Calcium-modulated and Enhances Superoxide Dismutase-1 (SOD1) AggregationPublication . Botelho, Hugo; S. Leal, Sónia; Cardoso, Isabel; Yanamandra, Kiran; Morozova-Roche, Ludmilla A.; Fritz, Günter; Gomes, Cláudio M.S100A6 is a small EF-hand calcium- and zinc-binding protein involved in the regulation of cell proliferation and cytoskeletal dynamics. It is overexpressed in neurodegenerative disorders and a proposed marker for Amyotrophic Lateral Sclerosis (ALS). Following recent reports of amyloid formation by S100 proteins, we investigated the aggregation properties of S100A6. Computational analysis using aggregation predictors Waltz and Zyggregator revealed increased propensity within S100A6 helices HI and HIV. Subsequent analysis of Thioflavin-T binding kinetics under acidic conditions elicited a very fast process with no lag phase and extensive formation of aggregates and stacked fibrils as observed by electron microscopy. Ca2+ exerted an inhibitory effect on the aggregation kinetics, which could be reverted upon chelation. An FT-IR investigation of the early conformational changes occurring under these conditions showed that Ca2+ promotes anti-parallel β-sheet conformations that repress fibrillation. At pH 7, Ca2+ rendered the fibril formation kinetics slower: time-resolved imaging showed that fibril formation is highly suppressed, with aggregates forming instead. In the absence of metals an extensive network of fibrils is formed. S100A6 oligomers, but not fibrils, were found to be cytotoxic, decreasing cell viability by up to 40%. This effect was not observed when the aggregates were formed in the presence of Ca2+. Interestingly, native S1006 seeds SOD1 aggregation, shortening its nucleation process. This suggests a cross-talk between these two proteins involved in ALS. Overall, these results put forward novel roles for S100 proteins, whose metal-modulated aggregation propensity may be a key aspect in their physiology and function.