Prevention of release of amyloid beta 1‐42 fibrils by inhibiting Hsc70

Abstract

AbstractBackgroundAmyloid beta 1‐42(Aβ1‐42) peptide is famous for its fibrils in amyloid plaques, which are pathological findings of Alzheimer’s disease(AD). The fibrils can amplify themselves like prions by using monomeric peptides as substrates. Therefore, neurons can uptake and release the fibrils, and this process can cause pathology to spread throughout the brain. In addition, hsc70‐mediated tau release by exocytosis has been shown. Therefore, in this study, we examined whether Hsc70 also mediates the release of Aβ1‐42 fibrils(F‐Aβ1‐42).MethodSH‐SY5Y cell was used in the study. Hsc70 dominant negative mutant, D10N, overexpressed with 72 hours plasmid transfection. MOCK plasmid and untransfected cells were used as controls. Hsp70 inhibitor VER‐155008(VER) was applied to other cell groups, and DMSO and untreated cells were controls. F‐Aβ1‐42 was labeled with Alexa Fluor‐488 and fragmented with ultrasonication before applying to the cells. We found that the cells took up fibrils within 6 hours. Therefore, VER, DMSO, D10N, MOCK and untreated cell groups were treated with fibrils, and incubated for 6 hours. Then, the cells were washed to remove extracellular fibrils and incubated for additional 18 hours. Supernatants were collected and measured with a fluorometer. 2 to 0,001 µM fluorescent‐labeled Aβ1‐42 fibrils were measured to make standard graphics.ResultWe showed that SH‐SY5Y cells effectively uptake and release F‐Aβ1‐42. VER application did not significantly affect to release of F‐Aβ1‐42 compared to DMSO and the control groups(p>0,05). However, F‐Aβ1‐42 release was significantly increased in D10N overexpressing cells compared to MOCK and untransfected cells(p<0,05).ConclusionIn this study, we have shown that release of F‐Aβ1‐42 can be prevented by intervention to the pathway that Hsc70 takes roles. Why the release was decreased with D10N but not with VER treatment may be caused by the fact that VER inhibits Hsp70 chaperon class, while D10N targets only Hsc70. These results showed that Hsc70 especially could take a role in the release of F‐Aβ1‐42. Recently, some drugs aiming at clearing extracellular F‐Aβ1‐42 were approved by the FDA. Our findings can provide a new target working in a different pathway for AD treatment. This study was supported by Istanbul University‐Cerrahpaşa BAP (Project ID:33479).