A double mutant Aβ42 inhibits Aβ42-induced plasma and mitochondrial membrane disruption in artificial membranes and intact cells

Ofek Oren ¹ Shani Ben Zichry ² Raz Jelinek ² Ran Taube ¹ Niv Papo ^3,4

¹Shraga Segal Department of Microbiology, Immunology and Genetics, Ben-Gurion University of the Negev, Beer-Sheva, Israel, Israel
²Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel, Israel
³Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel, Israel
⁴The National Institute of Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel, Israel

Aggregation and accumulation of the 42-residue amyloid β peptide (Aβ42) in the extracellular matrix of neurons and within these cells is considered a major cause of neuronal cell toxicity in Alzheimer`s disease (AD) patients. It is hypothesized that extra- and intracellular Aβ42 respectively interacts and disrupt the plasma and mitochondrial membranes fluidity, permeate these membranes and form pores enabling dysregulated calcium signaling and amyloid toxicity in AD. We have recently showed that a non-aggregating Aβ42 double mutant (Aβ42_DM) strongly binds Aβ42 and modifies both extra- and intracellular Aβ42-aggregation pathway resulting in low order Aβ42 oligomers with reduced neuronal cell uptake and toxicity.
In the current study, we show that Aβ42_DMprotects neuronal cells from Aβ42-induced accumulation of intracellular toxic levels of calcium and apoptosis. Aβ42_DM also inhibits Aβ42- induced mitochondrial membrane potential depolarization in intact neuronal cells and abolishes Aβ42 mediated decrease in cytochrome C oxidase activity in isolated mitochondria.

These results can be explained by the reduction in Aβ42-mediated changes in fluidity by Aβ42_DM that was observed in DOPC and CL/DOPC phospholipid vesicles mimicking the plasma and mitochondrial membranes, respectively. These observations are also in agreement with the phospholipid-induced conformational changes in Aβ42 that are inhibited by Aβ42_DM, and with the fact that Aβ42_DM, not like Aβ42, could not permeate cells and remained membrane localized.
Overall, we provide here a mechanistic explanation for the Aβ42_DM inhibitory activity against Aβ42-induced membranolytic activity and cell toxicity and give further evidence for its protective function in neuronal cells. We strongly believe that Aβ42_DM should be evaluated in-vivo for its potential use as a therapeutic lead for treating AD.